CrystEngComm View Article Online PAPER View Journal | View Issue Pyridine-driven assembly of Zn(II) and Cd(II) This article is licensed under a Creative Commons Attribution 3.0 Unported Licence. Cite this: CrystEngComm, 2023, 25, complexes with 2-furoic acid. The role of water in Open Access Article. Published on 17 April 2023. Downloaded on 6/26/2023 8:32:29 AM. 2739 a structural transformation† Daniel Ejarque, a Francisco Sánchez-Férez, a Núria Félez-Guerrero, a Teresa Calvet,b Mercè Font-Bardiac and Josefina Pons *a Understanding the factors governing the self-assembly of organic ligands with metal ions is essential to engineering target molecular arrangements with the desired properties. Indeed, small modifications of the synthetic conditions lead to the obtention of different complexes, varying from discrete monomers to coordination polymers (CPs). Based on the potential coordinating ability of 2-furoic acid (2-FA), we prepared five Zn(II) and Cd(II) complexes to study the behavior of the furane O atom and the competitiveness of the M–O bond formation in methanol (MeOH). Reactions between M(OAc)2·2H2O (M = Zn(II), Cd(II)), 2-FA, and two p-substituted pyridine ligands (isonicotinamide (Isn) and 4-acetylpyridine (4-Acpy)) in MeOH yielded the two dimers [Zn(μ-2-FA)(2-FA)(Isn)2]2 (1) and [Cd(μ-2-FA)(2-FA)(Isn)2]2 (2), the dimeric paddle-wheel [Zn(μ-2-FA)2(4-Acpy)]2 (3), and the monomer [Cd(2-FA)2(4-Acpy)2(OH2)] (4). Their crystal structures have been studied, observing diverse coordination numbers between five and seven and diverse coordination modes of the carboxylate groups. Interestingly, the recrystallization of 4 in acetonitrile (ACN) resulted in a dissolution–recrystallization structural transformation (DRST), leading to an intricate coordination polymer (CP) with the formula {[Cd(μ-2-FA)(2-FA)(OH2)2]n[Cd(μ-2-FA)(2-FA)(4-Acpy)(OH2)]n} Received 3rd February 2023, (5) exhibiting coordination of the furane O atom. Within this collection of arrangements, 2-FA displayed a Accepted 19th March 2023 great diversity of coordination modes that were combined and interchanged in the DRST process. Their DOI: 10.1039/d3ce00104k photophysical properties in solution have been analyzed and their quantum yields calculated. Likewise, further insight into the DRST process was obtained from fluorescence measurements. From these results, a rsc.li/crystengcomm pathway for the structural transformation highlighting the crucial role of solvents has been proposed. Introduction and the size of the d10 metal ion. Hence, accessible coordination numbers of d10 carboxylates range from four to The rational design of d10 coordination complexes has six for Zn(II), while Cd(II) tends to form coordination numbers emerged as an outstanding research area benefitting from up to seven. Zn(II) carboxylates display an almost equal their application in the field of optical materials as tendency to form either the paddle-wheel or the dimeric luminophores,1,2 their importance in sensing devices,3 or arrangement assembled by four or two bridging (μ2:η1:η1) their photoelectrical conductivity.4,5 The soft nature of Zn(II) carboxylate moieties, forming the [Zn2(CO2)4] or [Zn2(CO2)2] and Cd(II) ions enables a great structural diversity and secondary building units (SBUs), respectively. Instead, Cd(II) coordination versatility, giving access to a plethora of carboxylates display the dimeric array [Cd2(CO2)2] as the most arrangements guided only by the ligands' steric requirements common arrangement subsequently followed by the dimeric array with two additional chelate (μ1:η2) ligands denoted as [Cd2(CO2)4]-2 + 2. After the introduction of pyridine a derivatives, the preferred arrangements are barely altered, Departament de Química, Universitat Autònoma de Barcelona, 08193-Bellaterra, Barcelona, Spain. E-mail: josefina.pons@uab.es only leading to a further increase in dimensionality.6 b Departament de Mineralogia, Petrologia i Geologia Aplicada, Universitat de Regarding the structure of discrete molecular Zn(II) and Barcelona, Martí i Franquès s/n, 08028 Barcelona, Spain Cd(II) carboxylate complexes with N-donor ligands, a search in c Unitat de Difracció de Raig-X, Centres Científics i Tecnològics de la Universitat de the CSD7 has revealed that the Zn(II) tendency is shifted Barcelona (CCiTUB), Universitat de Barcelona, Solé i Sabarís, 1-3, 08028 towards the formation of the dimeric paddle-wheel (112 hits) Barcelona, Spain † Electronic supplementary information (ESI) available. CCDC 2239452–2239456. with respect to the dimer (4 hits).8–11 However, Cd(II) For ESI and crystallographic data in CIF or other electronic format see DOI: preferentially accommodates the [Cd2(CO2)4]-2 + 2 dimeric https://doi.org/10.1039/d3ce00104k array (82 hits). Interestingly, the combination of d10 metal This journal is © The Royal Society of Chemistry 2023 CrystEngComm, 2023, 25, 2739–2754 | 2739 View Article Online Paper CrystEngComm carboxylates and pyridine derivatives has already led to the or in molecular capture.32 Conversely, the transformations formation of excellent luminophores.12 involving the dissolution, bond breaking, and rearrangement Our group has previously studied the coordination into a different array are referred to as dissolution– chemistry of d10 metal ions towards carboxylic acids holding recrystallization structural transformations (DRSTs).33,34 ether groups,13,14 observing that Hg(II) and Hg(I) have a Despite the ongoing research in this field, there is still the preferential interaction over Zn(II) and Cd(II) with these O need for a better understanding of the factors governing this atoms, leading to the arrangement of unusual structures. process as well as to provide further mechanistic Instead, in the presence of Zn(II) and Cd(II), the dioxole O insights.35,36 Interestingly, DRST processes have shown atoms did not participate in the coordination environment promising results, presenting changes in their magnetic35,37 This article is licensed under a Creative Commons Attribution 3.0 Unported Licence. and only promoted weak C–H⋯O interactions.13 Continuing or photophysical properties.28,36 Aiming at the furane O with this research, we selected 2-furoic acid (2-FA) and two coordination, we selected the [M2(CO2)4]-2 + 2 dimeric array Open Access Article. Published on 17 April 2023. Downloaded on 6/26/2023 8:32:29 AM. pyridine derivatives (dPy), namely, isonicotinamide (Isn) and as the model structure from the available accessible 4-acetylpyridine (4-Acpy), to further study the crystal arrangements. We surmised that the higher distortion in engineering of Zn(II) and Cd(II) carboxylates with N-donor these dimers could enable decoordination, inducing available ligands in the presence of ether O atoms. There are a few coordination sites in the metal center that can be filled by reported cases in which the ether O atom of furane carboxylic weaker coordinating atoms. Hence, the choice of Isn was acid partakes in the coordination towards Zn(II) and Cd(II), based on the guided arrangement into dimeric Zn(II) but in those examples, the formation of the M–O bond is complexes driven by the amide–amide homosynthon,11 supported by a bridging bis-chelate (μ2:η2:η1:η1) coordination otherwise obtaining the dimeric paddle-wheel, whereas mode (Fig. 1).15–17 This double-chelate arrangement together 4-Acpy was selected as a non-guiding ligand for better with the formation of two five-membered rings is probably comparison.38 Therefore, we conducted the reaction of Zn(II) driving the coordination of the furane O atom. and Cd(II) with 2-FA and Isn or 4-Acpy. From these reactions, Although the 2-FA ligand can only be found coordinated we have isolated five complexes bearing two isostructural by the furane O atom in a heterometallic Zn(II)/Na dimeric [Zn(μ-2-FA)(2-FA)(Isn)2]2 (1) and [Cd(μ-2-FA)(2-FA) arrangement,18 we envisioned that it could promote the (Isn)]2]2 (2) arrays, a dimeric paddle-wheel ([Zn(μ-2-FA)2(4- coordination of the furane O atom to the metal center Acpy)]2 (3), a monomeric [Cd(2-FA)2(4-Acpy)2(OH2)] (4), and a supported by the formation of one five-membered ring that polymeric structure {[Cd(μ-2-FA)2(OH2)2]n[Cd(μ-2-FA)2(4-Acpy) provides better stabilization to bigger ions, and thus it will (OH2)]n} (5) (Scheme 1). preferentially support Cd–O bond formation over the Zn(II) Within this series, the 2-FA ligand presented the whole ion. Nevertheless, when dealing with ligands bearing weak range of coordination modes from μ1:η1 to μ1:η2:η1. coordinating atoms able to act as hemilabile linkers,19 Interestingly, complex 5 has been obtained from a DRST competitive bond formation with additional solvent process21,39 starting from 4 and presented an unusual molecules can occur.20,21 From these data, it is also inferred μ2:η2:η1:η1-coordination mode which is, to the best of our that strong intra- and intermolecular interactions can knowledge, the first reported case in which the furane O atom displace the coordination of additional carboxylate O atoms, of 2-FA participates in the coordination towards the Cd(II) ion. guiding a lower denticity and shifting from chelate to bridged Furthermore, the photophysical properties in solution of the or even to monodentate.22–26 Within this frame, structural aforementioned complexes have been compared to those of transformations arose as a fundamental process guiding the the previously reported analogues.11 In addition, the arrangement of molecular and extended entities.27,28 Among structural transformation is found to be accompanied by a them, those occurring in the solid state are denoted as solid- significant change in emission, and thus fluorescence state structural transformations (SSSTs), in which the experiments were used to trace the conversion of 4 to 5, switching between single crystal to single crystal (SCSC) is ensuring the importance of both solvent and water molecules predominant.29,30 In this regard, SCSC transformations in the transformation. From these results, a pathway for the demonstrated promising applications as molecular switches31 DRST process from 4 to 5 has been proposed. Fig. 1 Potential coordination modes of 2-FA ligand in Zn(II) and Cd(II) complexes. 2740 | CrystEngComm, 2023, 25, 2739–2754 This journal is © The Royal Society of Chemistry 2023 View Article Online CrystEngComm Paper This article is licensed under a Creative Commons Attribution 3.0 Unported Licence. Open Access Article. Published on 17 April 2023. Downloaded on 6/26/2023 8:32:29 AM. Scheme 1 Outline of the preparation of complexes 1–4 and DRST from 4 to 5. Experimental section from a 2θ angle of 5° to 30° and a step scan of 0.01671°, Materials and general methods using a Panalytical X'pert PRO MPD apparatus with a monochromatic CuKα radiation with λ = 1.5406 Å. Elemental Zinc(II) acetate dihydrate (Zn(OAc)2·2H2O), cadmium(II) analyses (C, H, N) were carried out on a Thermo Scientific acetate dihydrate (Cd(OAc)2·2H2O), 2-furoic acid (2-FA), Flash 2000 CHNS Analyzer. FTIR-ATR spectra were recorded isonicotinamide (Isn), and 4-acetylpyridine (4-Acpy) ligands, on a Perkin Elmer spectrometer equipped with an attenuated acetonitrile (ACN) (≥99.5%), diethyl ether (Et2O), n-heptane, total reflectance (ATR) accessory (model MKII Golden Gate) and methanol (MeOH) (99.5%) as solvents were purchased with a diamond window in the range 4000–500 cm−1. 1H and 13 from Sigma-Aldrich. Deuterated dimethyl sulfoxide (DMSO- C{1H} NMR spectra of 1–5 as well as DEPT-135 NMR spectra d6) was purchased from Eurisotop. All of them were used of 2 were recorded on a Bruker Ascend 300 MHz without further purification. All the reactions and spectrometer in DMSO-d6 solutions at RT. All the chemical manipulations were carried out in air at room temperature shifts (δ) are given in ppm relative to Me4Si as an internal (RT). Powder X-ray diffraction (PXRD) patterns were recorded standard. Thermogravimetric analysis (TGA) was conducted This journal is © The Royal Society of Chemistry 2023 CrystEngComm, 2023, 25, 2739–2754 | 2741 View Article Online Paper CrystEngComm using 2.204 mg (1), 3.147 mg (2), 2.835 mg (3), 2.255 mg (4), (2) Yield: 132 mg (60.8% with respect to Cd(OAc)2·2H2O). and 3.818 mg (5) in a TGA 7 Perkin Elmer thermobalance, Elem. anal. calc. for C44H36Cd2N8O16 (1157.61): C 45.65; H using an open platinum crucible. The heating ramp was set 3.13; N 9.68. Found: C, 45.54; H 3.09; N 9.49. FTIR-ATR to 5 °C min−1 from 50 to 330 °C under a nitrogen flow rate of (wavenumber, cm−1): 3299(w) [ν(N–H)], 3172(w) [ν(N–H)], 60 mL min−1. The electronic spectra in MeOH (anhydrous, 3144–3066 (br) [ν(C–H)]ar, 1696(m) [ν(CO)], 1612(w), 99.8%, Sigma-Aldrich) solution for 1–4, in ACN (HPLC grade, 1588(m), 1557(s) [νas(COO)], 1480(s) [ν(CC/CN)], 1411(sh) Sigma-Aldrich) solution for 5; and in Milli-Q water for [νs(COO)], 1399(s) [νs(COO)], 1368(s) [δ(CC/CN)], 1226 L-tyrosine (L-tyr) were run on an Agilent HP 8453 UV-vis (m), 1195(m) [ν(C–O–C)], 1147(m), 1119(w) [ν(C–O–C)], spectrophotometer with a quartz cell having a path length of 1098(w), 1080(w), 1067(w), 1017(m) [δip(C–H)], 933(w), 885(w), This article is licensed under a Creative Commons Attribution 3.0 Unported Licence. 1 cm in the range of 190–500 nm. Fluorescence 859(w), 820(m), 783(m) [δoop(C–H)], 752(m) [δoop(C–H)], measurements were carried out with a Perkin Elmer LS 55 50 677(w), 644(m), 612(m), 599 (m), 527(m), 513(w). 1H NMR Open Access Article. Published on 17 April 2023. Downloaded on 6/26/2023 8:32:29 AM. Hz Fluorescence Spectrometer using a 1 cm quartz cell in (300 MHz, DMSO-d6, Me4Si, 298 K): δ = 8.71 [2H, dd3, J = 4.4 MeOH (anhydrous, 99.8%, Sigma-Aldrich) (1–4), ACN (HPLC Hz; 4J = 1.7 Hz, o–H], 8.23 [1H, m, OC–NHsyn], 7.76 [2H, dd, 3 grade, Sigma-Aldrich) (5), and Milli-Q water (L-tyr) solutions. J = 4.4 Hz; 4J = 1.7 Hz, m–H], 7.69 [2H, m, OC–NHanti + In addition, the fluorescence measurements to trace the O–CH–CH–CH], 6.87 [1H, m, O–CH–CH–CH], 6.51 [1H, m, DRST from 4 to 5 were done using ACN (≥99.5%). All the O–CH–CH–CH]. 13C{1H} NMR (75 MHz, DMSO-d6; Me4Si; emission spectra were measured at 25 °C. The samples were 298 K): δ = 166.3 [H2N–CO], 164.5 [O2C], 150.3 [N–CH], excited at their maximum emission wavelength and their 149.7 [O2C–C], 144.5 [O–CH–CH–CH], 141.6 [N–CH–CH–C], emission was recorded between 200 and 600 nm. The data 121.6 [N–CH–CH], 114.5 [O–CH–CH–CH], 111.4 [O–CH–CH–CH]. obtained were corrected by means of the Origin Pro 2019b DEPT-135 NMR (75 MHz, DMSO-d6; Me4Si; 298 K): δ = 150.3 software. A CIE 1931 chromaticity diagram was generated [N–CH], 144.5 [O–CH–CH–CH], 121.7 [N–CH–CH], 114.5 using Origin Pro 2019b software. [O–CH–CH–CH], 111.4 [O–CH–CH–CH]. Preparation of compounds 1 and 2 Preparation of compounds 3 and 4 A MeOH solution (1 mL) of 2-FA (102 mg, 0.910 mmol (1); To a MeOH solution (1 mL) of M(OAc)2·2H2O (100 mg, 0.456 87.0 mg, 0.776 mmol (2)) was added dropwise to a MeOH mmol, M = Zn(II) (3); 102 mg, 0.383 mmol, M = Cd(II) (4)), solution (1 mL) of M(OAc)2·2H2O (100 mg, 0.456 mmol, M = 4-Acpy (0.208 mL, 1.87 mmol (3); 0.087 mL, 0.783 mmol (4)) Zn(II) (1); 103 mg, 0.386 mmol, M = Cd(II) (2)) at RT under was added dropwise at RT under constant stirring. Afterward, constant stirring. Then, a MeOH solution (1.5 mL) of Isn (231 a MeOH solution (1 mL) of 2-FA (105 mg, 0.918 mmol (3); mg, 1.89 mmol (1); 95.0 mg, 0.778 mmol (2)) was added 87.0 mg, 0.776 mmol (4)) was added to the mixture. The dropwise to the mixture at RT, observing immediately the reaction was left stirring for 2 h (3) and 24 h (4) at RT and formation of a white precipitate, and was left stirring for 1 h then, a white solid precipitated for 3, while the reaction (1) or 3 h (2). The powder was filtered, washed twice with 10 mixture of 4 was concentrated under vacuum and kept in the mL of cold Et2O, and dried under vacuum. Single crystals fridge for 3 days until a white solid was obtained. The suitable for X-ray diffraction were obtained by resulting solids were filtered, washed twice with 10 mL of recrystallization in MeOH after one week (1) or one day (2) at cold Et2O and dried under vacuum. Single crystals suitable RT. for X-ray diffraction were obtained by recrystallization in (1) Yield: 204 mg (84.2% with respect to Zn(OAc)2·2H2O). MeOH (3) or MeOH/EtOH (4) after keeping the solution in Elem. anal. calc. for C44H36Zn2N8O16 (1063.58): C 49.69; H the fridge for three weeks (3) or letting it evaporate at RT for 3.41; N 10.54; found: C, 49.48; H 3.24; N 10.31. FTIR-ATR four days (4). (wavenumber, cm−1): 3312(w) [ν(N–H)], 3161(w) [ν(N–H)], (3) Yield: 74.0 mg (39.7% with respect to Zn(OAc)2·2H2O). 3069(w) [ν(C–H)]ar, 1699(m) [ν(CO)], 1609(s), 1555(s) Elem. anal. calc. for C34H26Zn2N2O14 (817.35): C 49.96; H [νas(COO)], 1481(s) [ν(CC/CN)], 1420(s) [νs(COO)], 1397(s) 3.21; N 3.43. Found: C, 49.69; H 3.15; N 3.21. FTIR-ATR [νs(COO)], 1372(s) [δ(CC/CN)], 1227(m), 1196(m) [ν(C–O– (wavenumber, cm−1): 3150–3105(br) [ν(C–H)]ar, 1701(m) C)], 1148(m), 1121(w) [ν(C–O–C)], 1099(w), 1080(w), 1067(w), [ν(CO)], 1640(s) [ν(CC/CN)], 1591(m), 1574(m) 1018(m) [δip(C–H)], 1009(m), 935(w), 885(m), 860(w), 823(m), [νas(COO)], 1479(s), 1415(s) [νs(COO)], 1367(s) [δ(CC/CN)], 783(s) [δoop(C–H)], 750(s) [δoop(C–H)], 679(w), 642(s), 615(s), 1326(m), 1268(m), 1229(m), 1196(m) [ν(C–O–C)], 1142(m), 594(m), 519(w), 505(w). 1H NMR (300 MHz; DMSO-d6, Me4Si, 1076(m), 1063(m), 1012(m) [δip(C–H)], 962(m), 882(m), 298 K): δ = 8.76 [2H, m, o–H], 8.25 [1H, m, OC–NHsyn], 7.76 827(m), 798(m), 781(s) [δoop(C–H)], 755(s) [δoop(C–H)], 663(m), [4H, m, m–H + OC–NHanti + O–CH–CH–CH], 6.93 [1H, m, O– 616(m), 595(m). 1H NMR (300 MHz, DMSO-d6, 298 K): 8.83 CH–CH–CH], 6.55 [1H, m, O–CH–CH–CH]. 13C{1H} NMR (75 [2H, d, 3J = 3.8 Hz, o–H], 7.85 [2H, dd, 3J = 6.0 Hz; 4J = 1.2 Hz, MHz, DMSO-d6, Me4Si, 298 K): δ = 166.5 [H2N–CO], 163.8 m–H], 7.72 [2H, dd, 3J = 1.5 Hz; 4J = 0.7, O–CH–CH–CH], 6.93 [O2C], 150.3 [N–CH], 149.1 [O2C–C], 144.9 [O–CH–CH–CH], [2H, dd, 3J = 3.3 Hz; 4J = 0.5 Hz, O–CH–CH–CH], 6.52 [2H, 141.8 [N–CH–CH–C], 122.0 [N–CH–CH], 115.0 [O–CH–CH– dd, 3J = 3.3 Hz; 4J = 1.7 Hz, O–CH–CH–CH], 2.63 [3H, s, CH3]. 13 CH], 111.6 [O–CH–CH–CH]. C{1H} NMR (75 MHz, DMSO-d6, 298 K): 198.1 [H3C–CO], 2742 | CrystEngComm, 2023, 25, 2739–2754 This journal is © The Royal Society of Chemistry 2023 View Article Online CrystEngComm Paper 163.7 [O2C], 150.8 [N–CH], 149.1 [O2C–C], 144.7 [O–CH–CH– Table 1 Crystal data and structure refinement for 1 and 2 CH], 143.0 [N–CH–CH–C], 121.7 [N–CH–CH], 114.8 [O–CH– 1 2 CH–CH], 111.5 [O–CH–CH–CH], 27.0 [CH3]. Empirical formula C44H36Zn2N8O16 C44H36Cd2N8O16 (4) Yield: 132 mg (58.0% with respect to Cd(OAc)2·2H2O). Formula weight 1063.55 1157.61 Elem. anal. calc. for C24H22CdN2O9 (594.85): C 48.46; H 3.73; T (K) 100(2) 100(2) N 4.71. Found: C, 48.69; H 3.55; N 4.41. FTIR-ATR Wavelength (Å) 0.71073 0.71073 (wavenumber, cm−1): 3202–3066(br) [ν(O–H)], 3051(w) [ν(C– System, space group Monoclinic, P21/c Monoclinic, P21/c Unit cell dimensions H)]ar, 2997–2920(br) [ν(C–H)]al, 1698(w) [ν(CO)], 1684(m) a (Å) 11.0553(7) 11.1356(18) [ν(CO)], 1589(m), 1540(s) [νas(COO)], 1481(m) [ν(CC/ This article is licensed under a Creative Commons Attribution 3.0 Unported Licence. b (Å) 13.6054(10) 13.457(2) CN)], 1413(s) [νs(COO)], 1362(s) [δ(CC/CN)], 1260(m), c (Å) 15.7426(10) 15.870(2) 1224(m), 1193(m) [ν(C–O–C)], 1011 (m) [δip(C–H)], 816(s) α (°) 90 90 Open Access Article. Published on 17 April 2023. Downloaded on 6/26/2023 8:32:29 AM. β (°) 104.307 103.005(4) [δoop(C–H)], 783(m), 736(m), 591(s). 1H NMR (300 MHz, γ (°) 90 90 DMSO-d6, 298 K): 8.81 [4H, d, 3J = 5.8 Hz, o–H], 7.82 [4H, d, V (Å3) 2294.4(3) 2317.2(7) 3 J = 4.8 Hz, m–H], 7.70 [2H, d, 3J = 0.7 Hz, O–CH–CH–CH], Z 2 2 6.90 [2H, dd, 3J = 3.3 Hz; 4J = 1.7 Hz, O–CH–CH–CH], 6.51 Dcalc (mg m−3) 1.539 1.659 μ (mm−1) 1.127 0.998 [2H, dd, 3J = 3.3 Hz; 4J = 1.7 Hz, O–CH–CH–CH], 2.62 [6H, s, F (000) 1088 1160 CH3]. 13C{1H} NMR (75 MHz, DMSO-d6, 298 K): 198.1 [H3C– Crystal size (mm3) 0.135 × 0.031 0.155 × 0.027 CO], 164.6 [O2C], 150.8 [N–CH], 149.7 [O2C–C], 144.5 [O–CH– × 0.016 × 0.023 hkl ranges −13 ≤ h ≤ 13 −13 ≤ h ≤ 13 CH–CH], 142.9 [N–CH–CH–C], 121.6 [N–CH–CH], 114.5 [O– −17 ≤ k ≤ 17 0 ≤ k ≤ 16 CH–CH–CH], 111.4 [O–CH–CH–CH], 26.9 [CH3]. −19 ≤ l ≤ 19 0 ≤ l ≤ 19 θ range (°) 1.901 to 26.404 1.877 to 26.463 Reflections 53 701/4693/0.1346 4759/4759/0.2442 DRST of compound 5 collected/unique/[Rint] Complex 4 (22.2 mg, 0.037 mmol) was dissolved in 4 mL of Completeness to θ (%) 100.0 100.0 ACN (≥99.5%) and was left to slowly evaporate at RT until Absorption correction Semi-empirical Semi-empirical from equivalents from equivalents colorless prismatic crystals were formed after four days. The Max. and min. 0.7454 and 0.6222 0.7454 and 0.4775 resulting crystals were washed twice with 10 mL of n-heptane transmission and dried under vacuum. Refinement method Full-matrix Full-matrix least-squares on least-squares on Yield: 13.8 mg (87.6% with respect to 4). Elem. anal. calc. |F|2 |F|2 for C27H25Cd2NO16 (844.31): C, 38.41; H, 2.98; N, 1.66. Found: Data/restraints/parameters 4693/0/286 4759/4/286 C, 38.29; H, 2.74; N, 1.39. FTIR-ATR (wavenumber, cm−1): Goodness of fit on F 2 1.088 0.968 3488–3250(br) [ν(O–H)], 3144(w) [ν(C–H)ar], 1697(m) [ν(CO)], Final R indices [I > 2σ (I)] R1 = 0.0628, R1 = 0.0360, wR2 = 0.1158 wR2 = 0.0662 1591(m), 1543(s) [νas(COO)], 1477(s) [ν(CC/CN)], 1411(s) R indices (all data) R1 = 0.0863, R1 = 0.1056, [νs(COO)], 1399(s) [νs(COO)], 1365 (s) [δ(CC/CN)], wR2 = 0.1243 wR2 = 0.0936 1330(m), 1273(m), 1229(m), 1221(m), 1193(m) [ν(C–O–C)], Absolute structure n/a n/a 1140(w), 1074(w), 1065(w), 1017(m) [δip(C–H)], 968(w), 932(w), parameter Extinction coefficient n/a n/a 884(w), 859(w), 826(m), 815(m) [δoop(C–H)], 781(s) [δoop(C–H)], Largest diff. peak and 0.443 and −0.980 1.595 and −0.747 756(s) [δoop(C–H)], 666(m), 616(m), 593(s), 529(m), 501(s). 1H hole (e Å−3) NMR (300 MHz, DMSO-d6, 298 K): 8.81 [2H, dd, 3J = 4.4 Hz, 4J = 1.6 Hz, o–H], 7.81 [2H, dd, 3J = 4.4 Hz, 4J = 1.7 Hz, m–H], 7.70 [4H, dd, 3J = 1.7 Hz, 3J = 0.8 Hz, O–CH–CH–CH], 6.89 solved and refined using a SHELXTL Software Package [4H, dd, 3J = 3.3 Hz; 4J = 0.8 Hz, O–CH–CH–CH], 6.51 [4H, (version-2018/3).40 The integration of the data with a 0.80 Å dd, 3J = 3.3 Hz; 4J = 1.8 Hz, O–CH–CH–CH], 2.62 [3H, s, CH3]. 13 (1 and 2) and 0.70 Å (3–5) resolution, of which 4693 (1), 4759 C{1H} NMR (75 MHz, DMSO-d6, 298 K): 198.2 [H3C–CO], (2), 10 156 (3), 7294 (4), and 9453 (5) reflections were 164.4 [O2C], 150.9 [N–CH], 149.7 [O2C–C], 144.4 [O–CH–CH– independent, gave an average redundancy of 11.443 (1), 1.000 CH], 142.6 [N–CH–CH–C], 121.4 [N–CH–CH], 114.4 [O–CH– (2), 14.699 (3), 9.126 (4), and 3.927 (5), completeness of CH–CH], 111.4 [O–CH–CH–CH], 26.9 [CH3]. 99.9% (1), 99.7% (2), 99.9% (3), 99.6% (4), and 99.0% (5), Rsig of 5.88% (1), 10.56% (2), 1.78% (3), 6.63% (4), and 2.80% (5), X-ray crystallographic data presenting 3681 (78.44%) (1), 2688 (56.48%) (2), 9552 Colorless (1–5) specimens were used for the X-ray (94.05%) (3), 5785 (79.31%) (4), and 9106 (96.33%) (5) crystallographic analysis (Tables 1 and 2). reflections greater than 2σ(|F|2). The X-ray intensity data were measured on a D8 Venture For 1–5 the final cell constants and volume are based system equipped with a multilayer monochromator and a Mo upon refinement of the XYZ centroids of reflections above 20 microfocus (λ = 0.71073 Å). For all the compounds, the σ(I). Data were corrected for absorption effects using the frames were integrated using the Bruker SAINT software multi-scan method (SADABS). Crystal data and additional package using a narrow-frame algorithm. The structures were details of structure refinement for 1–5 are reported in This journal is © The Royal Society of Chemistry 2023 CrystEngComm, 2023, 25, 2739–2754 | 2743 View Article Online Paper CrystEngComm Table 2 Crystal data and structure refinement for 3–5 3 4 5 Empirical formula C34H26Zn2N2O14 C24H22CdN2O9 C27H25Cd2NO16 Formula weight 817.31 594.83 844.28 T (K) 100(2) 100(2) 100(2) Wavelength (Å) 0.71073 0.71073 0.71073 System, space group Tetragonal, P43 Triclinic, P1̄ Monoclinic, P21 Unit cell dimensions a (Å) 11.7905(4) 9.2175(3) 12.3981(6) This article is licensed under a Creative Commons Attribution 3.0 Unported Licence. b (Å) 11.7905(4) 11.0467(5) 8.4459(3) c (Å) 23.9682(8) 13.4532(6) 15.1806(7) α (°) 90 104.477(2) 90 Open Access Article. Published on 17 April 2023. Downloaded on 6/26/2023 8:32:29 AM. β (°) 90 101.662(2) 104.276(2) γ (°) 90 109.6270(10) 90 V (Å3) 3332.0(3) 1186.22(9) 1540.52(12) Z 4 2 2 Dcalc (mg m−3) 1.629 1.665 1.820 μ (mm−1) 1.515 0.978 1.457 F (000) 1664 600 836 Crystal size (mm3) 0.276 × 0.153 × 0.069 0.061 × 0.025 × 0.012 0.132 × 0.087 × 0.040 hkl ranges −16 ≤ h ≤ 16 −13 < = h < = 13 −17 ≤ h ≤ 17 −16 ≤ k ≤ 16 −15 < = k < = 15 −12 ≤ k ≤ 12 −34 ≤ l ≤ 34 −19 < = l < = 19 −21 ≤ l ≤ 21 θ range (°) 1.925 to 30.517 2.085 to 30.621 2.439 to 30.732 Reflections collected/unique/[Rint] 149 278/10 156/0.0442 66 566/7294/0.1313 37 126/9453/0.0299 Completeness to θ (%) 99.9 100.0 99.8 Absorption correction Semi-empirical from equivalents Semi-empirical from equivalents Semi-empirical from equivalents Max. and min. transmission 0.7444 and 0.6605 0.7461 and 0.5736 0.7461 and 0.6472 Refinement method Full-matrix least-squares on |F|2 Full-matrix least-squares on |F|2 Full-matrix least-squares on |F|2 Data/restraints/parameters 10 156/4/472 7294/3/333 9453/10/402 Goodness of fit on F 2 1.033 1.049 1.037 Final R indices [I > 2σ (I)] R1 = 0.0298, R1 = 0.0448, R1 = 0.0272, wR2 = 0.0809 wR2 = 0.0920 wR2 = 0.0645 R indices (all data) R1 = 0.0335, R1 = 0.0693, R1 = 0.0292, wR2 = 0.0835 wR2 = 0.1033 wR2 = 0.0658 Absolute structure parameter n/a n/a 0.18(2) Extinction coefficient n/a n/a n/a Largest diff-peak and hole (e Å−3) 0.611 and −0.434 1.535 and −1.058 2.254 and −1.073 Tables 1 and 2. Complete information about the crystal for X-ray crystallographic analysis were grown via structure and molecular geometry is available in CIF format recrystallization in MeOH (1 and 3) or MeOH/EtOH (4) and via CCDC 2239454 (1), 2239452 (2), 2239456 (3), 2239453 (4), by slow evaporation of the mother liquors (2). In addition, and 2239455 (5). Molecular graphics were generated using the recrystallization of 4 in ACN (≥99.5%) resulted in the Mercury 4.3.1 software,41 using the POV-Ray image package.42 DRST process yielding the coordination polymer 5. The The color codes for all the molecular graphics are as follows: selection of ACN was done aiming to minimize hydrogen dark blue (Zn), light orange (Cd), red (O), light blue (N), gray bond interactions that can abstract and compete with the (C), and white (H). The evaluation of the geometry distortion coordination of the weakly coordinating O atom from the of the metal cores in 1–5 was carried out using version 2.1 of furane ring.22,24–26 SHAPE software from the corresponding .cif files.43 Further discussion of the extended structures of 1–5 is provided in the ESI.† General characterization Compounds 1–5 were characterized by powder X-ray Results and discussion diffraction (PXRD), elemental analysis (EA), FTIR-ATR, 1H, 13 C{1H} NMR spectroscopy, thermogravimetric analysis Preparation of 1–5 (TGA), and single-crystal X-ray diffraction method. The phase Complexes 1–4 were obtained by reaction of M(OAc)2·2H2O purity of the samples was confirmed by PXRD. The (M = Zn(II), Cd(II)) and 2-FA with their corresponding dPy corresponding patterns can be found in the ESI,† Fig. S1–S5. ligands (Isn, 1 and 2; 4-Acpy, 3 and 4) in MeOH at room The EA of all the compounds agrees with the proposed temperature (RT). Compounds 1 and 3 were prepared using a formulas. TGA of complexes 1–5 was used to evaluate the 1 : 2 : 4 molar ratio, while 2 and 4 were synthesized with a 1 : thermal stability of the samples (ESI,† Fig. S6–S10). 2 : 2 molar ratio. The corresponding single crystals suitable Complexes 1 and 2 are stable up to 158.0 and 161.2 °C, 2744 | CrystEngComm, 2023, 25, 2739–2754 This journal is © The Royal Society of Chemistry 2023 View Article Online CrystEngComm Paper respectively (ESI,† Fig. S6 and S7). At these temperatures, they and 3066 cm−1 attributed to ν(O–H) of solvent molecules start to release the four Isn ligands up to 264.2 °C (exp. (ESI,† Fig. S11–S15). 45.3%; calcd 45.9%) and 273.9 °C (exp. 42.5%; calcd 42.2%). The 1H and 13C{1H} NMR spectra of 1–5 were recorded in Therefore, the thermal stability of complexes 1 and 2 is DMSO-d6. All the spectra show the signals of 2-FA and their almost identical, which is in line with their isostructural corresponding dPy ligands. The 1H NMR spectra of all the arrangement. Complex 3 is stable up to 115.7 °C, where a compounds present three signals between 7.76 and 6.51 ppm weight loss of 28.3% (calcd 29.6%) attributed to the release assigned to the protons of 2-FA. For 1 and 2, the aromatic H of two 4-Acpy is observed (ESI,† Fig. S8). In 4, a weight loss atoms from Isn are observed between 8.83 and 7.76 ppm, from 71.7 °C to 97.7 °C of 3.9% (calcd 3.0%) is assigned to while the bands attributable to the amide group H atoms are This article is licensed under a Creative Commons Attribution 3.0 Unported Licence. the removal of a water molecule, while in 5 the weight loss found at 8.25, 7.76 (1), and 8.23, 7.69 ppm (2). Otherwise, the between 75.7 °C and 112.6 °C of 6.1% (calcd 6.4%) is aromatic H atoms of 4-Acpy in 3–5 appear between 8.83 and Open Access Article. Published on 17 April 2023. Downloaded on 6/26/2023 8:32:29 AM. attributed to the release of three water molecules. From this 7.81 ppm. Moreover, the signal of the methyl group from point, complex 4 exhibits a sequential loss of two 4-Acpy 4-Acpy is found around 2.62 ppm. The 1H NMR spectra of ligands, the first between 97.7 °C and 172.6 °C (exp. 23.2%; 1–5 confirm the 1 : 1 (1, 2, 4), 2 : 1 (3) and 4 : 1 (5) molar ratio calcd 20.4%) and then from 172.6 °C to 284.9 °C (exp. 20.0%; between 2-FA and the corresponding dPy ligand (ESI,† Fig. calcd 20.4%) (ESI,† Fig. S9). Instead, the TGA of complex 5 S16–S20). suggests a simultaneous loss of one 4-Acpy and two 2-FA In the 13C{1H} NMR spectra, the signals corresponding to ligands (exp. 40.9%; calcd 40.7%) accompanied by the carboxylate group of 2-FA are found between 164.6 and decomposition (ESI,† Fig. S10). Thus, the thermal stability of 163.7 ppm, while those corresponding to the carbon atoms the complexes follows the order 4 < 5 < 3 < 1 < 2. from the five-membered ring appear between 144.9 and 111.4 The FTIR-ATR spectra of 1–5 display the characteristic ppm. Regarding the dPy ligands, the signal from the carbonyl bands of 2-FA and their corresponding dPy ligands. The group of 4-Acpy in 3–5 (∼198 ppm) is downfield shifted with absence of a strong band at 1674 cm−1 in all the compounds respect to the carbonyl of Isn in 1 and 2 (∼166 ppm). In indicates that 2-FA is deprotonated. In addition, all the addition, the aromatic carbon atoms appeared between 150.9 compounds display typical bands between 1574–1540 cm−1 and 121.4 ppm, while the methyl carbon atoms of 4-Acpy are for νas(COO) and 1420–1397 cm−1 for νs(COO), displaying a shown around 27 ppm in 3–5 (ESI,† Fig. S21–S26).46 The difference with values of 158 and 135 cm−1 (1), 158 and 146 correct assignment of the C aromatic atoms required the use cm−1 (2), 159 cm−1 (3), 127 cm−1 (4), 144 and 132 cm−1 (5) of a DEPT-135 experiment (ESI,† Fig. S23). attributed to the Δ values, indicating bridged (1–3, 5) and chelated (1, 2, 4, and 5) coordination modes of the carboxylate groups.44,45 Additionally, other bands such as the Crystal structure of compounds 1 and 2 vibrations of the aromatic rings (ν(CC/CN) and δ(CC/ Compounds 1 and 2 crystallize in the monoclinic P21/c space CN)) from either 2-FA and the dPy ligands, or the carbonyl group. Both are isostructural compounds consisting of a groups from dPy and the N–H vibrations from Isn, have also dimeric complex with [MO4N2] cores (M = Zn(II) (1), Cd(II) (2)) been identified and assigned.46 Remarkably, compound 4 composed of two μ2-η1:η1-2-FA, which join together the metal presents two ν(CO) vibrations attributed to a slightly ions as well as two μ2-η2-2-FA and two μ1-η1-Isn ligands, different behavior of their 4-Acpy ligands in comparison with forming distorted octahedral geometries (S = 6.229 (1), 3.807 3 and 5, which only show a single signal for ν(CO). (2)) (Fig. 2; ESI,† Table S1, Fig. S1 and S2), giving rise to Compounds 4 and 5 also exhibit a broad band between 3330 [M2(CO2)4]-2 + 2 SBUs. In addition, the bond lengths and Fig. 2 Molecular structure of (a) 1 and (b) 2. Hydrogen atoms have been omitted for clarity. This journal is © The Royal Society of Chemistry 2023 CrystEngComm, 2023, 25, 2739–2754 | 2745 View Article Online Paper CrystEngComm Table 3 Bond lengths (Å) and bond angles (°) present in complexes 1 Table 4 Bond lengths (Å) and bond angles (°) present in complex 3 and 2 Bond lengths (Å) 1 Zn(1)–O(2) 2.042(3) Zn(2)–O(1) 2.008(3) Bond lengths (Å) Zn(1)–O(5) 2.080(3) Zn(2)–O(4) 2.045(3) Zn(1)–O(3) 2.220(3) Zn(1)–N(1) 2.144(4) Zn(1)–O(8) 2.034(3) Zn(2)–O(7) 2.063(3) Zn(1)–O(11) 2.016(3) Zn(2)–O(10) 2.073(3) Zn(1)–O(4) 2.295(3) Zn(1)–N(3) 2.148(3) Zn(1)–O(6) 2.020(3) Zn(1)⋯Zn(1) 3.9286(8) Zn(1)–N(1) 2.029(3) Zn(2)–N(2) 2.031(3) Zn(1)⋯Zn(2) 2.9875(5) Zn(1)–O(7)#1 2.015(3) This article is licensed under a Creative Commons Attribution 3.0 Unported Licence. Bond angles (°) Bond angles (°) O(3)–Zn(1)–O(4) 58.48(10) O(4)–Zn(1)–N(3) 86.55(12) O(2)–Zn(1)–O(5) 157.72(11) O(1)–Zn(2)–O(4) 159.68(11) Open Access Article. Published on 17 April 2023. Downloaded on 6/26/2023 8:32:29 AM. O(2)–Zn(1)–O(8) 88.69(12) O(1)–Zn(2)–O(7) 88.79(11) O(3)–Zn(1)–O(6) 149.39(11) O(6)–Zn(1)–O(7)#1 118.36(12) O(2)–Zn(1)–O(11) 87.85(11) O(1)–Zn(2)–O(10) 89.26(12) O(3)–Zn(1)–O(7)#1 91.51(11) O(6)–Zn(1)–N(1) 93.93(13) O(3)–Zn(1)–N(1) 88.77(12) O(6)–Zn(1)–N(3) 88.25(13) O(2)–Zn(1)–N(1) 103.50(11) O(1)–Zn(2)–N(2) 101.87(11) O(5)–Zn(1)–O(8) 87.84(11) O(4)–Zn(2)–O(7) 87.46(11) O(3)–Zn(1)–N(3) 84.88(12) O(7)#1–Zn(1)–N(1) 96.52(12) O(4)–Zn(1)–O(6) 91.39(11) O(7)#1–Zn(1)–N(3) 90.22(13) O(5)–Zn(1)–O(11) 87.67(11) O(4)–Zn(2)–O(10) 86.85(11) O(5)–Zn(1)–N(1) 98.77(10) O(4)–Zn(2)–N(2) 98.45(11) O(4)–Zn(1)–O(7)#1 149.98(11) N(1)–Zn(1)–N(3) 170.86(14) O(4)–Zn(1)–N(1) 84.52(12) O(8)–Zn(1)–O(11) 159.28(11) O(7)–Zn(2)–O(10) 158.16(11) O(8)–Zn(1)–N(1) 96.98(11) O(7)–Zn(2)–N(2) 101.28(10) 2 O(11)–Zn(1)–N(1) 103.69(11) O(10)–Zn(2)–N(2) 100.40(11) Bond lengths (Å) Cd(1)–O(1) 2.358(3) Cd(1)–N(1) 2.338(4) Cd(1)–O(2) 2.436(3) Cd(1)–N(3) 2.288(4) bond angles oscillate between 2.015(3)–2.295(3) Å and Cd(1)–O(4) 2.193(4) Cd(1)⋯Cd(1) 3.8337(7) 58.48(10)–170.86(14)° (1), and 2.193(4)–2.436(3) Å and Cd(1)–O(5)#1 2.225(4) 54.37(11)–172.24(14)° (2), lying within the range of previously Bond angles (°) reported dimeric compounds (Table 3).11 O(1)–Cd(1)–O(2) 54.37(11) O(2)–Cd(1)–N(3) 87.42(12) O(1)–Cd(1)–O(4) 145.32(14) O(4)–Cd(1)–O(5)#1 124.35(15) O(1)–Cd(1)–O(5)#1 89.51(14) O(4)–Cd(1)–N(1) 87.23(15) Crystal structure of compound 3 O(1)–Cd(1)–N(1) 86.36(13) O(4)–Cd(1)–N(3) 92.06(14) O(1)–Cd(1)–N(3) 89.86(12) O(5)#1–Cd(1)–N(1) 88.47(15) Compound 3 crystallizes in the tetragonal P43 space group O(2)–Cd(1)–O(4) 91.12(13) O(5)#1–Cd(1)–N(3) 98.28(14) bearing a [Zn2(CO2)4] dimeric paddle-wheel Zn(II) array O(2)–Cd(1)–O(5)#1 143.55(13) N(1)–Cd(1)–N(3) 172.24(14) holding two [ZnO4N] cores with a slightly distorted square O(2)–Cd(1)–N(1) 84.86(13) pyramidal geometry (S = 0.199 for Zn(1), 0.175 for Zn(2)) (1) #1: −x + 1, −y + 2, −z + 1. (2) #1: −x + 1, −y, −z + 1. (Fig. 3a and Table S1, ESI†). This arrangement is assembled by four μ2-η1:η1 carboxylate ligands in a syn–syn conformation and two μ1–η1-4-Acpy ligands at the apical sites (Fig. 3b). The Zn–O bond lengths range between 2.008(2) and 2.080(3) Å, while the Zn–N bond lengths are between 2.029(3) and 2.031(3) Å (Table 4). These values are in range with those of previously reported paddle-wheel structures (2.009(1)– 2.085(3)).47–49 Finally, Zn(II) ions are displaced by 0.374 Å out of the basal plane towards the apical position. Fig. 3 Representation of (a) the [ZnO4N] cores and (b) the dimeric paddle-wheel arrangement in 3. Hydrogen atoms have been omitted Fig. 4 (a) Monomeric structure of 4. (b) Representation of its for clarity. [CdO5N2] core. Hydrogen atoms have been omitted for clarity. 2746 | CrystEngComm, 2023, 25, 2739–2754 This journal is © The Royal Society of Chemistry 2023 View Article Online CrystEngComm Paper Table 5 Bond lengths (Å) and bond angles (°) present in complex 4 by two asymmetrically coordinated μ1–η2-2-FA ligands, two Bond lengths (Å) μ1–η1-4-Acpy and one μ1–η1 water molecule (Fig. 4a), showing a distorted pentagonal bipyramidal geometry (S = 2.773) Cd(1)–O(1) 2.333(2) Cd(1)–O(9) 2.284(2) (Fig. 4b and Table S1, ESI†). Its bond lengths and bond Cd(1)–O(2) 2.537(2) Cd(1)–N(1) 2.361(3) Cd(1)–O(4) 2.324(2) Cd(1)–N(2) 2.356(3) angles range between 2.284(2) and 2.553(2) Å, in agreement Cd(1)–O(5) 2.553(2) with similar Cd(II) monomeric structures (Table 5).50,51 Bond angles (°) O(1)–Cd(1)–O(2) 53.81(8) O(4)–Cd(1)–O(5) 53.63(8) Crystal structure of compound 5 This article is licensed under a Creative Commons Attribution 3.0 Unported Licence. O(1)–Cd(1)–O(4) 82.19(8) O(4)–Cd(1)–O(9) 139.19(9) O(1)–Cd(1)–O(5) 134.02(8) O(4)–Cd(1)–N(1) 97.87(9) Compound 5 crystallizes in the monoclinic P21 space group, accommodating two different polymeric chains (A and B). Open Access Article. Published on 17 April 2023. Downloaded on 6/26/2023 8:32:29 AM. O(1)–Cd(1)–O(9) 138.58(9) O(4)–Cd(1)–N(2) 90.66(9) O(1)–Cd(1)–N(1) 90.40(9) O(5)–Cd(1)–O(9) 86.14(8) Chain A contains a [CdO6] core bearing a distorted trigonal O(1)–Cd(1)–N(2) 100.88(9) O(5)–Cd(1)–N(1) 84.45(8) prismatic geometry (S = 2.895; ESI,† Table S1) from two O(2)–Cd(1)–O(4) 134.50(8) O(5)–Cd(1)–N(2) 92.54(8) O(2)–Cd(1)–O(5) 171.86(7) O(9)–Cd(1)–N(1) 83.02(9) μ2–η1:η1-syn–anti-2-FA ligands, one μ1:η2-2-FA and two water O(2)–Cd(1)–O(9) 85.75(8) O(9)–Cd(1)–N(2) 83.87(9) molecules (Fig. 5a), whereas chain B holds a [CdO6N] core O(2)–Cd(1)–N(1) 93.82(8) N(1)–Cd(1)–N(2) 166.71(9) with a slightly distorted pentagonal bipyramidal geometry (S O(2)–Cd(1)–N(2) 87.34(8) = 1.210; ESI,† Table S1) from two different coordination modes of the 2-FA ligands (μ2–η2:η1:η1 and μ1:η1), a μ1–η1-4- Acpy ligand and a water molecule (Fig. 5b). Interestingly, the bridging bis-chelate (μ2–η2:η1: η1) coordination mode of the Crystal structure of compound 4 2-FA ligand in chain B is quite unusual and seems to be Compound 4 crystallizes in the triclinic P1̄ space group, modulated by the coordination of water molecules, which displaying a monomeric array with a [CdO5N2] core formed force geometric constraints through intra- and intermolecular Fig. 5 Representation of the cores of (a) chain A and (b) chain B of 5, and intramolecular interactions (black dashed lines) in (c) A and (d) B. Hydrogen atoms not involved in the interactions have been omitted for clarity. This journal is © The Royal Society of Chemistry 2023 CrystEngComm, 2023, 25, 2739–2754 | 2747 View Article Online Paper CrystEngComm Table 6 Bond lengths (Å) and bond angles (°) present in complex 5 Bond lengths (Å) Cd(1)–O(1) 2.270(3) Cd(2)–O(9) 2.241(3) Cd(1)–O(2) 2.633(4) Cd(2)–O(12) 2.309(3) Cd(1)–O(4) 2.271(3) Cd(2)–O(12)#2 2.502(3) Cd(1)–O(5)#1 2.297(3) Cd(2)–O(13)#2 2.361(3) Cd(1)–O(7) 2.258(3) Cd(2)–O(14) 2.621(3) Cd(1)–O(8) 2.310(3) Cd(2)–O(16) 2.317(3) Cd(2)–N(1) 2.306(3) This article is licensed under a Creative Commons Attribution 3.0 Unported Licence. Bond angles (°) Open Access Article. Published on 17 April 2023. Downloaded on 6/26/2023 8:32:29 AM. O(1)–Cd(1)–O(2) 52.52(12) O(9)–Cd(2)–O(14) 93.10(11) O(1)–Cd(1)–O(4) 114.28(12) O(9)–Cd(2)–O(16) 92.24(12) O(1)–Cd(1)–O(5)#1 90.84(14) O(9)–Cd(2)–N(1) 178.31(16) O(1)–Cd(1)–O(7) 95.80(14) O(12)–Cd(2)–O(12)#2 135.55(5) O(1)–Cd(1)–O(8) 154.04(12) O(12)–Cd(2)–O(13)#2 82.10(11) O(2)–Cd(1)–O(4) 80.32(12) O(12)–Cd(2)–O(14) 65.67(10) O(2)–Cd(1)–O(5)#1 125.32(11) O(12)–Cd(2)–O(16) 138.03(11) O(2)–Cd(1)–O(7) 86.52(12) O(12)–Cd(2)–N(1) 88.66(13) O(2)–Cd(1)–O(8) 151.18(11) O(12)#2–Cd(2)–O(13)#2 53.81(10) O(4)–Cd(1)–O(5)#1 81.60(11) O(12)#2–Cd(2)–O(14) 157.91(10) O(4)–Cd(1)–O(7) 127.46(11) O(12)#2–Cd(2)–O(16) 85.82(10) O(4)–Cd(1)–O(8) 87.32(11) O(12)#2–Cd(2)–N(1) 87.58(13) O(5)#1–Cd(1)–O(7) 142.53(11) O(13)#2–Cd(2)–O(14) 147.77(10) O(5)#1–Cd(1)–O(8) 77.72(11) O(13)#2–Cd(2)–O(16) 139.63(11) O(7)–Cd(1)–O(8) 80.50(12) O(13)#2–Cd(2)–N(1) 91.92(12) O(9)–Cd(2)–O(12) 92.89(13) O(14)–Cd(2)–O(16) 72.47(11) O(9)–Cd(2)–O(12)#2 91.78(12) O(14)–Cd(2)–N(1) 86.92(13) O(9)–Cd(2)–O(13)#2 88.97(11) O(16)–Cd(2)–N(1) 86.15(13) Cd(2)–O(12)–Cd(2)#4 144.80(14) #1: −x + 1, y − 1/2, −z. #2: −x + 2, y − 1/2, −z + 1. #4 –x + 2, y + 1/2, −z + 1. interactions. The Cd–O bond lengths with 2-FA ligands are μ2:η2:η1: η1-2-FA is lengthened to 2.361(3) Å (Table 6). Indeed, within the range of previously reported Cd(II) complexes probably both H(16B) by an intramolecular interaction and (2.218(3) for monodentate, 2.297(3)–2.361(3) Å for bridging, H(7A) through an intermolecular association triggered the 2.1735(12)–2.3168(12), and 2.313(3)–2.499(3) for chelate).52,53 μ1:η1 coordination mode of 2-FA by grabbing the carboxylate Selected bond lengths and angles are displayed in Table 6. O(10) atom. The presence of strong intramolecular The presence of coordinated water molecules promoted interactions between coordinated water molecules and O–H⋯O interactions with carboxylate ligands and supported carboxylate O atoms has already fostered monodentate both the chain formation and the assembly of the chains. coordination modes in Cd(II) complexes.53,54 Two intramolecular interactions are held within chain A A detailed description of the extended structures as well between H(7B) and H(8A) with O(4) and O(2), respectively as their associated distances and angles is provided in the (Fig. 5c). Likewise, H(16A) and H(16B) interact with O(10) and ESI,† Fig. S27 and Table S2 (1 and 2), Fig. S28 and Table S3 O(13) along chain B (Table 7 and Fig. 5d). Intramolecular (3), Fig. S29 and Table S4 (4), and Fig. S30 and Table S5 (5). interactions subtracted carboxylate O atoms and promoted the elongation of the corresponding Cd–O bond lengths. In A, the Cd(1)–O(2) bond length of μ1:η2-2-FA increases up to Photophysical properties 2.634(4) Å, while in B the Cd(2)–O(13) bond length in UV-vis spectroscopy. The UV-vis spectra of Isn and 4-Acpy ligands and complexes 1–4 were recorded in MeOH (99.8%), Table 7 Intramolecular interactions present in complex 5 whereas those of 4-Acpy and 5 were measured in ACN (HPLC grade) at 298 K. To ensure non-aggregation of the ligands Intramolecular (ESI,† Fig. S31–S35) and the complexes (ESI,† Fig. S36–S40), interactions in A D–H (Å) H⋯A (Å) D⋯A (Å) >D–H⋯A (°) we performed additive measurements between ∼1 × 10−9 M O(7)–H(7B)⋯O(4) 0.80(3) 1.93(3) 2.729(4) 177(5) and ∼1 × 10−5 M in MeOH or ACN when required. In O(8)–H(8A)⋯O(2) 0.81(4) 1.93(4) 2.719(5) 168(4) addition, a comparison between the absorption spectra of the Intramolecular ligands (ESI,† Fig. S41) and the complexes (ESI,† Fig. S42) at interactions in B D–H (Å) H⋯A (Å) D⋯A (Å) >D–H⋯A (°) the selected concentration for the emission experiments is O(16)–H(16A)⋯O(10) 0.80(4) 1.86(4) 2.645(4) 168(6) provided in the ESI.† The complexes display absorptions with O(16)–H(16B)⋯O(13) 0.81(3) 1.91(3) 2.712(5) 178(6) an increasing intensity following the order 4 < 5 < 2 < 3 < 1 2748 | CrystEngComm, 2023, 25, 2739–2754 This journal is © The Royal Society of Chemistry 2023 View Article Online CrystEngComm Paper Table 8 Detailed parameters extracted from the photophysical properties of 1–5b Compound λmax-abs (log(ε)) λexc λmax-em Stokes shift Φs 1 202 (4.60), 226 (4.60), 275 (4.01), 281 (3.84) 227 334, 345 14 113, 15 067 0.02 2 204 (6.87), 247 (6.43), 278 (5.75) 230 347, 364, 387 14 660, 16 006, 17 638 0.01 3 202 (7.20), 226 (6.69), 274 (5.94), 281 (5.90) 281 343 6433 0.43 4 207 (4.22), 278 (3.57) 281 334 5647 0.20 5 190a (4.74), 227 (4.74), 275 (3.75) 281 397, 419 10 398, 11 721 0.03 a Absorption maxima is out of range and the data of the highest energy peak is provided. b All the wavelengths are given in nm. ε values are given in M−1 × cm−1. Stokes shift values are given in cm−1. λmax-abs = maximum of absorption; λexc = excitation maximum; λmax-em = maximum of This article is licensed under a Creative Commons Attribution 3.0 Unported Licence. emission; Φs = relative quantum yield of the samples using L-tyr as the standard (Φ = 0.14).58 Open Access Article. Published on 17 April 2023. Downloaded on 6/26/2023 8:32:29 AM. at the selected concentrations. All the relevant details of the energies, these transitions become dependent on the complexes are summarized in Table 8, while those from the molecular structure and the electronic properties of the dPy ligands are provided in the ESI,† Table S6. From these data, it ligands. In line with these results, absorption maxima at 275 can be inferred that diluted samples of ∼1 × 10−9 M solutions and 281 nm (1, ESI,† Fig. S43) and 278 nm (2, ESI,† Fig. S44) of complexes 1 and 2 show two bands centered at 202 and could be ascribed to 2-FA LC transitions, whereas absorption 227 nm (1) and 204 and 242 nm (2); upon concentration, any at 281 nm (3, ESI,† Fig. S45) and 278 nm (4, ESI,† Fig. S46) significant change is observable until ∼1 × 10−7 M, where a probably originates from a mixture of 2-FA and 4-Acpy LC progressive bathochromic shift was observed, suggesting transitions. Mimicking previous results, the Isn ligand seems aggregation (ESI,† Fig. S36 and S37). Compounds 3 and 4 to promote intraligand charge transfer (ILCT) transitions present two defined bands centered at 202 and 281 nm (3) between 220 and 250 nm supported by the dimeric and 205 and 282 nm (4) at the initial concentration of ∼1 × arrangement, while complexes with 4-Acpy display only LC 10−9 M, while two additional bands overlapped the first one transitions, especially in the dimeric paddle-wheel complex arising at 222 and 242 nm (3) and 219 and 242 nm (4) after that displays the worst arrangement for charge transfers the concentration is increased. Since a noticeable shift of the between dPy ligands. Indeed, the origin of the absorptions at bands as in 1 and 2 was not observed when the concentration 226 nm (1) and 247 nm (2) was attributed to ILCT between was increased, no apparent signals of aggregation of 3 and 4 Isn ligands since these bands were not observed for the free were observed (ESI,† Fig. S38 and S39). Finally, the UV-vis ligands in MeOH (202 and 271 nm for 2-FA, and 202 and 274 spectrum of 5 presents a main signal centered at 242 nm nm for Isn) and fall within the mentioned range for Isn together with an overlapped signal around 219 nm and a complexes. In the case of 5, from the absorption spectra of minor one at 281 nm. The spectrum does not show any the ligands in ACN, the assignment of the absorption band aggregation evidence upon concentration as for complexes 3 at 275 nm to a 4-Acpy LC transition seems more reasonable, and 4 (ESI,† Fig. S40). Hence, it seems that compounds perhaps with a small contribution from 2-FA even if its presenting Isn (1 and 2) are more prone to present absorption in this region is meager (ESI,† Fig. S47). aggregation than complexes containing 4-Acpy (3–5) as Therefore, the absorption of the complexes can be ligands, which could be attributed to the strong preference of attributed to local excitations (LEs) of 2-FA and dPy ligands in the Isn ligands towards the formation of amide–amide 3–5, with the contribution of ILCT between Isn ligands in 1 homosynthons between their amide moieties, in contrast to and 2. Since the incorporation of a better electron-withdrawing 4-Acpy, which does not present any recurrent supramolecular group in para position should be reflected as a bathochromic synthon.55,56 Therefore, solutions of ∼1 × 10−8 M were shift in absorption, complexes with 4-Acpy ligand display selected for 1–5 to measure their photoluminescence absorption maxima at lower energy than those with Isn. properties, aiming to prevent negative effects derived from Fluorescence spectroscopy. Fluorescence measurements aggregation-caused quenching (ACQ).57 In addition, the UV- were performed using MeOH (99.8%) for 1–4 and ACN (HPLC vis absorption spectra of each complex have been compared grade) for 4 and 5, whereas DRST studies of 4 were to those of the corresponding ligands at the concentration conducted in ACN (≥99.5%). Complexes 1 and 2 show used for the emission experiments (ESI,† Fig. S43–S47). unfolded emission bands presenting their maxima at 334, It seems that the photophysical properties of the 345 nm (1) and 347, 364, 387 nm (2) when excited at 227 and complexes can be understood by extrapolating the results 230 nm, respectively. Differently, compounds 3–5 were from previously reported analogous complexes.11 In these excited at 281 nm, displaying single bands centered at 343 studies, the origin of the less energetic transitions in the nm (3) and 334 nm (4), while compound 5 showed an absorption spectra of Zn(II) and Cd(II) complexes was found unfolded signal with two apparent peaks at 397 and 419 nm to be ligand centered (LC) over the carboxylate ligands (Table 8 and Fig. 6). regardless of the structure with only contribution from LC The wavelength of the emission maxima of the transitions over 4-Acpy, whereas Isn excitation in the compounds containing Isn (λexc = 227 nm, 1; 230 nm, 2) is complexes occurs at lower wavelengths. Moving to higher hypsochromically shifted compared to that of the compounds This journal is © The Royal Society of Chemistry 2023 CrystEngComm, 2023, 25, 2739–2754 | 2749 View Article Online Paper CrystEngComm This article is licensed under a Creative Commons Attribution 3.0 Unported Licence. Open Access Article. Published on 17 April 2023. Downloaded on 6/26/2023 8:32:29 AM. Fig. 6 Emission spectra of complexes 1–5 excited at 227 nm (1), 230 nm (2) and 281 nm (3–5) using MeOH (1–4) and ACN (5) solutions of ∼1 × 10−8 M. containing 4-Acpy (λexc = 281 nm, 3–5). In addition, the radiative decay processes as more water molecules are emission of each complex has been compared with their coordinated to the metal centers.63–65 Finally, compound 3 corresponding ligands at the same λexc, observing a possesses a higher Φs, which should be related to the bathochromic shift of the bands in complexes 1–3 and 5, paddle-wheel motif that minimizes charge transfer whereas compound 4 shows a hypsochromic shift with respect transitions between the 4-Acpy and the 2-FA ligands to the emission of 2-FA (ESI,† Fig. S48–S52). Furthermore, compared with the arrays of the rest of the compounds.11 according to the CIE 1931 chromaticity diagram, the resultant emission colors are electric violet (1 and 2), azure radiance (3 and 4), and blue ribbon (5) (ESI,† Fig. S53). Insights into the DRST process The relative quantum yields (Φs) of 1–5 were calculated The formation of the M–O bond from the furane ring in using eqn (1): complexes 1–4 seems to be hindered by the saturated      2 coordination environment of Zn(II) and Cd(II) ions via the ODref IS ns preferred coordination of the carboxylate O atoms and Φs ¼ Φref × × × (1) ODs I ref nref N-donor ligands in MeOH. The H-bond ability of MeOH can promote O–H⋯O interactions with the furane O atom and where Φs is the quantum yield, OD is the optical density displace its coordination. Hence, we selected complex 4 as a (or absorbance) at the selected excitation wavelength, I is suitable candidate for the DRST experiment considering two the area under the curve of the emission spectra, and n premises: (i) that heptacoordinate geometry presents is the refractive index of the employed solvent. L-Tyrosine remarkable degrees of geometrical distortions and (ii) Cd(II) was utilized as reference (Φref = 0.14),58 using 1.01 × 10−7 ions can accommodate high coordination numbers up to M solutions with Milli-Q water (n = 1.3325),59 while eight. samples 1–4 were measured in MeOH (n = 1.3314),60 and Indeed, heptacoordinate geometries hold small energetic compound 5 in ACN (n = 1.3404),61 all of them at 298 K. differences between the primary accessible polyhedral: the The resulting Φs values were 0.02 (1), 0.01 (2), 0.43 (3), capped octahedral (COC-7), the capped trigonal prismatic 0.20 (4), and 0.03 (5). The lower quantum yields of (CTPR-7), and the pentagonal bipyramidal (PBPY-7)66–68 and compounds 1 and 2 should be tentatively attributed to are prone to be intermediates of six- and eight-coordinated the probable rotation of their amide moieties towards the complexes from associative or dissociative reactions.69 These formation of intramolecular amide–amide homosynthons, small differences are associated with low-barrier fluxional leading to charge transfers between Isn ligands that processes that foster stereochemical modifications and should decrease the resulting fluorescence efficiencies.11,62 interconversion through small angular displacement. Instead, Moreover, the coordination of water molecules in 4 and 5 the greater stability of a hexacoordinated Cd(II) complex was is also ascribed to a quenching of their fluorescence reported to exhibit small geometrical changes without quantum yields, providing additional pathways to non- variation in the coordination bonds.70 2750 | CrystEngComm, 2023, 25, 2739–2754 This journal is © The Royal Society of Chemistry 2023 View Article Online CrystEngComm Paper In complex 4, the 4-Acpy ligands are located at the apical resulted in a decrease of the Φs without a significant shift in sites of the pentagonal bipyramid and thus are prone to be emission maxima.36 exchanged. It should be stressed that surrounding O atoms To ensure the role of both the solvent and the presence of from carboxylate groups, even if not directly coordinated to water molecules, we conducted fluorescence experiments to the Cd(II) center, participate in the interconversion between follow the structural transformation between 4 and 5. We the polyhedra by imposing geometrical constraints. Initially, therefore recorded the emission spectra of 4 in ACN (HPLC in the structure of 4, the coordinated water molecule orients grade) using a concentration of ∼1 × 10−3 M without the furane O atoms of vicinal monomers towards the Cd(II) observing changes when compared with the spectra of 4 in ion. The incorporation of a second water molecule led to the MeOH. Considering that no structural transformation seems This article is licensed under a Creative Commons Attribution 3.0 Unported Licence. full dissociation of 4-Acpy ligands resulting in chain A to occur under these conditions and that the difference formation. Therefore, we could understand chain B of 5 as between the emission of 4 and 5 in ACN (HPLC grade) is Open Access Article. Published on 17 April 2023. Downloaded on 6/26/2023 8:32:29 AM. an intermediate arrangement of a DRST process in which 4 reflected as a bathochromic shift of 85 nm and a decrease of suffers an apical site ligand exchange between 4-Acpy and the Φs, fluorescence proved to be a useful technique to trace water molecules to yield chain A. The co-crystallization of the interconversion between 4 and 5. chain B seems to be grounded by the five-membered ring Then, the spectrum of 4 in ACN (≥99.5%) was monitored stabilization after the coordination of the furane O atom. over time. At a concentration of ∼1 × 10−3 M, the initial t = 0 There are three potential mechanisms for ligand substitution: min measurement resulted in the rising of an emission band associative, dissociative, or interchange, and in particular, at the same position of 5 with a small shoulder from 4, interchange can retain the metal coordination environment indicating a fast conversion from 4 to 5. In less than three or present products from association or dissociation.21 In minutes this shoulder disappeared (Fig. 7a), suggesting a full this example, the DRST process induces a dissociative conversion. Hence, to slow down the transformation from 4 interchange since the bond formation and breaking results to 5, the same experiment was carried out using a more in a lower coordination number.21 In line with this diluted sample (∼1 × 10−4 M). In this case, the initial statement, the reaction of 2-FA with Cd(II) in water promoted measurement shows that 4 remains completely unaltered, the coordination of an additional water molecule, increasing while after three minutes a mixture of 4 and 5 has been the coordination number to seven and yielding the monomer identified, that continues the transformation until minute six [Cd(2-FA)(OH2)3] with three coordinated water molecules.71 (Fig. 7b). From this point forward, the process has been As aforementioned, study of the changes in the properties followed for two days without observing any significant of the complexes involved in DRST processes has not been change in emission, suggesting a partial structural extensively pursued. Most of the cases provide structural data transformation below 1 × 10−3 M in solution, being both 4 about the initial and the final product,28,72 but fewer and 5 in coexistence. It should be noted that the examples present tracing of the DRST and factors governing recrystallization of 4 was conducted at higher concentrations the transformation. From the limited number of examples, of ∼1 × 10−2 M and thus, the full conversion would be Zhang et al. demonstrated the importance and potential achieved, favoring the crystallization of 5. interest of water-induced DRST processes in a series of Cu(I)- Therefore, the fluorescence experiments demonstrate that based arrays. Indeed, they were able to trace the the DRST process requires both the use of a polar aprotic interconversion process by fluorescence spectroscopy, which solvent, avoiding the formation of strong hydrogen bond Fig. 7 Monitoring of the structural transformation of 4 to 5 in a concentration of (a) ∼1 × 10−3 M and (b) ∼1 × 10−4 M in 3 mL of ACN (≥99.5%). Purple dashed lines represent the emission spectra of 4 in MeOH (99.8%) at ∼1 × 10−8 M, while orange dashed lines indicate the emission spectra of 5 in ACN (HPLC grade) at ∼1 × 10−8 M. This journal is © The Royal Society of Chemistry 2023 CrystEngComm, 2023, 25, 2739–2754 | 2751 View Article Online Paper CrystEngComm This article is licensed under a Creative Commons Attribution 3.0 Unported Licence. Open Access Article. Published on 17 April 2023. Downloaded on 6/26/2023 8:32:29 AM. Scheme 2 Representation of the DRST pathway between 4 and 5. Charts between brackets represent intermediate geometries. Green solid lines refer to newly formed edges by the addition or uncoordination of carboxylate moieties. Ligands in grey stand for non-chelating 2-FA. Straight black arrows indicate the release of the atom, whereas black curved arrows indicate addition of atoms. interactions, and the presence of water that triggered the already been demonstrated and it seems to be required for molecular rearrangement. Interestingly, this DRST process the structural transformation.21,27 Indeed, water holds 48% results in a significant change in the emission properties by of the structural transformations involving changes in the both a change in the emission wavelength and a decrease in coordination environment.73 The key role of water within this the fluorescence quantum yield. DRST process is highlighted by the formation of strong After merging these results, our assumption is that the intramolecular and intermolecular H-bond interactions. It redissolution of 4 in a polar medium led to a geometric assists in the change in coordination number of the Cd(II) accommodation and the addition of the vicinal furane O center both by modulating the coordination or not of the atom from a neighboring monomeric unit already facing carboxylate ligands through strong H-bond interactions and towards the Cd(II) ion by the mentioned H-bond (Scheme 2-A) by promoting their geometric re-accommodation. that favors the release of one 4-Acpy ligand at the apical site. This spatial disposition is triggered by the strong O–H⋯O Conclusions interactions from coordinated water molecules, so the addition of the furane ring is accomplished through the Five Zn(II)/Cd(II) complexes based on 2-FA and two different complementary face sharing the vertex with water in the dPy ligands (Isn and 4-Acpy) have been successfully PBPY-7 polyhedron. The additional stabilization of the five- synthesized and characterized. We confirmed the structure- membered ring formation seems to be enough to displace directed arrangement of the dimeric complexes (1 and 2) by the 4-Acpy ligand and change the chelate coordination mode the recurrent amide–amide homosynthon regardless of the of 2-FA to monodentate, promoting polymerization of the monodentate carboxylic acid. Instead, the non-guiding 4-Acpy monomeric units (Scheme 2-B). Again, coordinated water allows the formation of paddle-wheel (3) or monomeric (4) molecules shift to perform intramolecular H-bond arrangements. Remarkably, the DRST of 4 in ACN leads to interactions to stabilize the monodentate coordination mode. the formation of an unusual CP (5). This set of compounds Once chain B of 5 is formed (Scheme 2-C), a water-assisted displayed the whole range of coordination modes of 2-FA addition of another water molecule promotes the from monodentate to the unusual bridging bis-chelate, and decoordination of the weak furane O atoms and the release variable coordination numbers between five and seven. The of the remaining 4-Acpy. This is accompanied by a geometric photophysical properties of all the compounds were accommodation of the coordination environment with the recorded, observing better Φs values for the complexes subsequent change in the coordination mode of the containing 4-Acpy (3–5) with respect to Isn (1 and 2). Among monodentate 2-FA to chelate (Scheme 2-D), ending in them, the paddle-wheel motif seems to maximize its IL polymer chain A. The water-assisted addition of the second emission, displaying a Φs of 0.43. Conversely, the water molecule agrees with their allocation, both being at the coordination of water molecules in 4 and 5 leads to a same edge of the trigonal prismatic polyhedron (Scheme 2-E). quenching of their fluorescence efficiency, while the amide– The role of solvent molecules in inducing rearrangements, amide homosynthon of 1 and 2 could force a molecular changes or even cleavage of M–O carboxylate bonds has motion in solution towards the formation of intramolecular 2752 | CrystEngComm, 2023, 25, 2739–2754 This journal is © The Royal Society of Chemistry 2023 View Article Online CrystEngComm Paper amide–amide interactions and cause the strong reduction of 9 A. E. Goldberg, M. A. Kiskin, S. A. Kozyukhin, A. A. Sidorov Φs. Interestingly, the competitiveness between water, and I. L. Eremenko, Russ. Chem. Bull., 2011, 60, 1012–1015. carboxylate, and a weakly coordinating O atom from a furane 10 G.-B. Che, S.-S. Wang, X.-L. Zha, X.-Y. Li, C.-B. Liu, X.-J. ring has been demonstrated by tracing the formation of 5 Zhang, Z.-L. Xu and Q.-W. Wang, Inorg. Chim. Acta, by a DRST process through X-ray data and fluorescence 2013, 394, 481–487. experiments. These results contribute to the limited number 11 F. Sánchez-Férez, J. M. Rius-Bartra, J. A. Ayllón, T. Calvet, M. of cases in which DRST processes have been traced to date Font-Bardia and J. Pons, Molecules, 2022, 27, 1365. and evince the crucial role of solvents in controlling the 12 G. Kumar, G. Kumar and R. Gupta, Inorg. Chem. Front., engagement of weakly coordinating atoms, in particular of 2021, 8, 1334–1373. This article is licensed under a Creative Commons Attribution 3.0 Unported Licence. water molecules in the assembly of discrete molecular entities. 13 D. Ejarque, F. Sánchez-Férez, J. A. Ayllón, T. Calvet, M. Font- Bardia and J. Pons, Cryst. Growth Des., 2020, 20, 383–400. Open Access Article. Published on 17 April 2023. Downloaded on 6/26/2023 8:32:29 AM. Author contributions 14 F. Sánchez-Férez, X. Solans-Monfort, T. Calvet, M. Font- Bardia and J. Pons, CrystEngComm, 2022, 24, 4351–4355. Conceptualization, J. P.; data curation, D. E., F. S.-F. and M. 15 L. Zhang, Z.-J. Li, Q.-P. Lin, J. Zhang, P.-X. Yin, Y.-Y. Qin, F.-B; formal analysis, D. E., F. S.-F. and M. F.-B; funding J.-K. Cheng and Y.-G. Yao, CrystEngComm, 2009, 11, acquisition, J. P.; investigation, D. E. and F. S.-F.; 1934–1939. methodology, D. E. and F. S.-F.; project administration, J. P.; 16 C.-S. Liu, E. C. Sañudo, M. Hu, L.-M. Zhou, L.-Q. Guo, S.-T. resources, J. P. and T. C.; software, D. E. and F. S.-F.; Ma, L.-J. Gao and S.-M. Fang, CrystEngComm, 2010, 12, supervision, J. P.; validation, J. P. and T. C.; visualization, D. 853–865. E. and F. S.-F.; writing – original draft preparation, D. E. and 17 C.-S. Liu, C. Wang, M. Hu and S.-M. Fang, Z. Anorg. Allg. F. S.-F.; writing – review and editing, J. P. and T. C. All Chem., 2011, 637, 748–754. authors have read and agreed to the published version of the 18 B. Paluchowska, J. K. Maurin and J. Leciejewicz, J. Coord. manuscript. Chem., 2001, 52, 253–264. 19 P. Braunstein and F. Naud, Angew. Chem., Int. Ed., 2001, 40, Conflicts of interest 680–699. 20 L. Zhang, J. Zhang, Z.-J. Li, Y.-Y. Qin, Q.-P. Lin and Y.-G. Yao, There are no conflicts to declare. Chem. – Eur. J., 2009, 15, 989–1000. 21 C.-P. Li and M. Du, Chem. Commun., 2011, 47, 5958–5972. Acknowledgements 22 X. F. Zheng, X. Q. Shen, X. S. Wan, H. Y. Zhang, H. Wang, R. J. P. acknowledges financial support from the CB615921 Yang and C. Y. Niu, J. Coord. Chem., 2007, 60, 1317–1325. project, the CB616406 project from “Fundació La Caixa”, and 23 C.-C. Ai, J.-F. Xiang, M. Li and L.-J. Yuan, Acta Crystallogr., the 2017SGR1687 project from the Generalitat de Catalunya. Sect. E: Struct. Rep. Online, 2007, 63, m565–m566. D. E. acknowledges the PIF predoctoral fellowship from the 24 I. A. Lutsenko, D. E. Baravikov, M. A. Kiskin, Y. V. Nelyubina, Universitat Autònoma de Barcelona. P. V. Primakov, O. B. Bekker, A. V. Khoroshilov, A. A. Sidorov and I. L. Eremenko, Russ. J. Coord. Chem., 2020, 46, 411–419. References 25 I. A. Lutsenko, D. S. Yambulatov, M. A. Kiskin, Y. V. Nelyubina, P. V. Primakov, O. B. Bekker, A. A. Sidorov and 1 A. N. Gusev, M. A. Kiskin, E. V. Braga, M. Chapran, G. I. L. Eremenko, Russ. J. Coord. Chem., 2020, 46, 787–794. Wiosna-Salyga, G. V. Baryshnikov, V. A. Minaeva, B. F. 26 W. Ai, H. He, L. Liu, Q. Liu, X. Lv, J. Li and D. Sun, Minaev, K. Ivaniuk, P. Stakhira, H. Ågren and W. Linert, CrystEngComm, 2008, 10, 1480–1486. J. Phys. Chem. C, 2019, 123, 11850–11859. 27 D.-X. Xue, W.-X. Zhang, X.-M. Chen and H.-Z. Wang, Chem. 2 A. Gusev, V. Shul, E. Braga, E. Zamnius, M. Kryukova and W. Commun., 2008, 1551–1553. Linert, Dyes Pigm., 2020, 183, 108626. 28 L.-H. Cao, H.-Y. Li, H. Xu, Y.-L. Wei and S.-Q. Zang, Dalton 3 C. V. Esteves, J. Costa, H. Bernard, R. Tripier and R. Trans., 2017, 46, 11656–11663. Delgado, New J. Chem., 2020, 44, 6589–6600. 29 A. Chaudhary, A. Mohammad and S. M. Mobin, Cryst. 4 B. Dutta, A. Dey, C. Sinha, P. Pratim Ray and M. H. Mir, Growth Des., 2017, 17, 2893–2910. Inorg. Chem., 2018, 57, 8029–8032. 30 Y. Li, B. Zhao, J.-P. Xue, J. Xie, Z.-S. Yao and J. Tao, Nat. 5 A. Chandra, M. Das, K. Pal, S. Jana, B. Dutta, P. P. Ray, K. Commun., 2021, 12, 6908. Jana and C. Sinha, ACS Omega, 2019, 4, 17649–17661. 31 F. F. Li, L. Zhang, L. Le Gong, C. S. Yan, H. Y. Gao and F. 6 J. Cepeda, S. Pérez-Yáñez, J. Á. García, S. Rojas and A. Luo, Dalton Trans., 2017, 46, 338–341. Rodríguez-Diéguez, Dalton Trans., 2021, 50, 9269–9282. 32 M. Zhu, X.-Z. Song, S.-Y. Song, S.-N. Zhao, X. Meng, L.-L. Wu, 7 C. R. Groom, I. J. Bruno, M. P. Lightfoot and S. C. Ward, C. Wang and H.-J. Zhang, Adv. Sci., 2015, 2, 1500012. Acta Crystallogr., Sect. B: Struct. Sci., Cryst. Eng. Mater., 33 L.-H. Cao, Y.-S. Wei, H. Xu, S.-Q. Zang and T. C. W. Mak, Adv. 2016, 72, 171–179. Funct. Mater., 2015, 25, 6448–6457. 8 Y. Bing, X. Li, M.-Q. Zha and D.-J. Wang, Synth. React. Inorg., 34 D.-L. Meng, X. Wang, C.-B. Tian, W. Wei and S.-W. Du, Cryst. Met.-Org., Nano-Met. Chem., 2011, 41, 798–804. Growth Des., 2020, 20, 1203–1210. This journal is © The Royal Society of Chemistry 2023 CrystEngComm, 2023, 25, 2739–2754 | 2753 View Article Online Paper CrystEngComm 35 X.-F. Zhang, T. Yan, T. Wang, J. Feng, Q. Wang, X. Wang, L. 52 M.-S. Chen, C.-H. Zhang, D.-Z. Kuang, Y.-L. Feng and Y.-F. Du and Q.-H. Zhao, CrystEngComm, 2018, 20, 570–577. Deng, Acta Crystallogr., Sect. E: Struct. Rep. Online, 2007, 63, 36 Z.-Y. Zhang, Y. Su, L.-X. Shi, S.-F. Li, F. Fabunmi, S.-L. Li, T. m1290–m1291. Yu, Z.-N. Chen, Z. Su and H.-K. Liu, Inorg. Chem., 2020, 59, 53 Y.-Q. Yang, C.-H. Li, W. Li, D.-C. Guo and Y.-F. Kuang, Chin. 13326–13334. J. Struct. Chem., 2006, 25, 1409–1413. 37 L. Fan, X. Liu, L. Zhang, X. Kong, Z. Xiao, W. Fan, R. Wang 54 X.-F. Zheng, X.-Q. Shen, X.-S. Wan, H.-Y. Zhang, H. Wang, R. and D. Sun, J. Mol. Struct., 2019, 1197, 87–95. Yang and C.-Y. Niu, J. Coord. Chem., 2007, 60, 1317–1325. 38 L. Moreno-Gómez, F. Sánchez-Férez, T. Calvet, M. Font- 55 R. Brahma and J. B. Baruah, ACS Omega, 2020, 5, 3774–3785. Bardia and J. Pons, Inorg. Chim. Acta, 2020, 506, 119561. 56 C. B. Aakeröy, B. M. T. Scott, M. M. Smith, J. F. Urbina and J. This article is licensed under a Creative Commons Attribution 3.0 Unported Licence. 39 W. Wang, Y.-X. Wang and H.-B. Yang, Chem. Soc. Rev., Desper, Inorg. Chem., 2009, 48, 4052–4061. 2016, 45, 2656–2693. 57 P. Li, D. Zhang, Y. Zhang, W. Lu, J. Zhang, W. Wang, Q. He, Open Access Article. Published on 17 April 2023. Downloaded on 6/26/2023 8:32:29 AM. 40 G. M. Sheldrick, Acta Crystallogr., Sect. A: Found. Crystallogr., P. Théato and T. Chen, ACS Macro Lett., 2019, 8, 937–942. 2008, 64, 112–122. 58 R. F. Chen, Anal. Lett., 1967, 1, 35–42. 41 C. F. MacRae, I. Sovago, S. J. Cottrell, P. T. A. Galek, P. 59 G. M. Hale and M. R. Querry, Appl. Opt., 1973, 12, 555–563. McCabe, E. Pidcock, M. Platings, G. P. Shields, J. S. Stevens, 60 H. El-Kashef, Phys. B, 2000, 279, 295–301. M. Towler and P. A. Wood, J. Appl. Crystallogr., 2020, 53, 61 K. Moutzouris, M. Papamichael, S. C. Betsis, I. Stavrakas, G. 226–235. Hloupis and D. Triantis, Appl. Phys. B: Lasers Opt., 2014, 116, 42 Persistence of Vision Pty. Ltd., Persistence of Vision (TM) 617–622. Raytracer, Williamstown, Australia, 2004, Available online: 62 P. L. Muiño and P. R. Callis, J. Phys. Chem. B, 2009, 113, https://www.povray.org/ (accessed on 12 April 2023). 2572–2577. 43 M. Llunell, D. Casanova, J. Cirera, P. Alemany and S. Alvarez, 63 A. Kobayashi, R. Arata, T. Ogawa, M. Yoshida and M. Kato, SHAPE. Program for the Stereochemical Analysis of Molecular Inorg. Chem., 2017, 56, 4280–4288. Fragments by Means of Continuous Shape Measures and 64 F. W. Steuber, J. J. Gough, É. Whelan, L. Burtnyak, A. L. Associated Tools, Universitat de Barcelona, Barcelona, 2013. Bradley and W. Schmitt, Inorg. Chem., 2020, 59, 44 G. B. Deacon and R. J. Phillips, Coord. Chem. Rev., 1980, 33, 17244–17250. 227–250. 65 D. Ejarque, F. Sánchez-Férez, T. Calvet, M. Font-Bardia and J. 45 K. Nakamoto, Infrared and Raman Spectra of Inorganic and Pons, Inorg. Chim. Acta, 2020, 509, 119695. Coordination Compounds: Part A: Theory and Applications in 66 D. L. Kepert, Inorganic Stereochemistry, Springer, Berlin, Inorganic Chemistry, Wiley Interscience, Hoboken, New Heidelberg, 1982, vol. 6. Jersey, USA, 6th edn, 2009. 67 R. Hoffmann, B. F. Beier, E. L. Muetterties and A. R. Rossi, 46 D. H. Williams and I. Fleming, Spectroscopic Methods in Inorg. Chem., 1977, 16, 511–522. Organic Chemistry, Springer Nature, Cham, Switzerland, 7th 68 Z. Lin and I. Bytheway, Inorg. Chem., 1996, 35, 594–603. edn, 2008. 69 D. Casanova, P. Alemany, J. M. Bofill and S. Alvarez, Chem. – 47 A. Karmakar and J. B. Baruah, Polyhedron, 2008, 27, Eur. J., 2003, 9, 1281–1295. 3409–3416. 70 M. K. Sharma and P. K. Bharadwaj, Inorg. Chem., 2011, 50, 48 K. Yadava and J. J. Vittal, Cryst. Growth Des., 2019, 19, 1889–1897. 2542–2547. 71 M. A. Shmelev, G. N. Kuznetsova, N. V. Gogoleva, F. M. 49 D. C. Akintayo, W. A. Munzeiwa, S. B. Jonnalagadda and B. Dolgushin, M. A. Kiskin, A. A. Sidorov and I. L. Eremenko, Omondi, Polyhedron, 2022, 213, 115589. Russ. Chem. Bull., 2021, 70, 830–838. 50 P. Saxena and N. Thirupathi, Polyhedron, 2015, 98, 238–250. 72 B. Notash, M. Farhadi Rodbari, G. Gallo and R. Dinnebier, 51 E. A. H. Griffith, N. G. Charles and E. L. Amma, Acta Inorg. Chem., 2021, 60, 9212–9223. Crystallogr., Sect. C: Cryst. Struct. Commun., 1985, 41, 73 Q.-Q. Li, H. Liu, T.-T. Zheng, P. Liu, J.-X. Song and Y.-Y. 673–678. Wang, CrystEngComm, 2020, 22, 6750–6775. 2754 | CrystEngComm, 2023, 25, 2739–2754 This journal is © The Royal Society of Chemistry 2023