Journal of Molecular Structure 1277 (2023) 134896 Contents lists available at ScienceDirect Journal of Molecular Structure journal homepage: www.elsevier.com/locate/molstr Structural influence of the length and functionality of N,N-donor spacers in Cd(II) ladder-type coordination polymers Daniel Ejarque a, Teresa Calvet b, Mercè Font-Bardia c, Josefina Pons a,∗ a Departament de Química, Universitat Autònoma de Barcelona, 08193-Bellaterra, Barcelona, Spain b Departament de Mineralogia, Petrologia i Geologia Aplicada, Universitat de Barcelona, Martí i Franquès s/n, 08028 Barcelona, Spain c Unitat de Difracció de Raig-X, Centres Científics i Tecnològics de la Universitat de Barcelona (CCiTUB), Universitat de Barcelona, Solé i Sabarís, 1-3, 08028 Barcelona, Spain a r t i c l e i n f o a b s t r a c t Article history: The understanding of the effect generated by small differences of the organic ligands on the molec- Received 3 December 2022 ular and supramolecular arrangement of coordination polymers (CPs) is a key factor to control their Revised 27 December 2022 properties. Therefore, the study of structurally related ligands differing in some factors inter alia func- Accepted 31 December 2022 tional group orientation, length, or functionality is a crucial task for crystal engineers. In this contribu- Available online 1 January 2023 tion, the reactions between Cd(OAc)2 ·2H2 O, α -acetamidocinnamic acid (HACA) and different N,N-donor Keywords: spacers with increasing length (pyrazine, pyz; 4,4’-bipyridine, 4,4’-bipy; 1,2-bis(4-pyridyl)ethylene, 1,2- Cd(II) compounds bpe), as well as additional functionalities (4,4’-azopyridine, 4,4’-azpy) have been successfully performed. X-ray crystal structure Their crystal structures have been elucidated revealing a family of ladder-type 1D CPs showing molec- N,N-donor linkers ular arrays with single pillars for {[Cd2 (μ-ACA)2 (ACA)2 (pyz)(H2 O)2 ]·2EtOH}n (1), and double pillars for Spacer length effect [Cd2 (μ-ACA)2 (ACA)2 (4,4’-bipy)2 ]n (2), [Cd2 (μ-ACA)2 (ACA)2 (1,2-bpe)2 ]n (3) and {[Cd2 (μ-ACA)2 (ACA)2 (4,4’- Ladder-type coordination polymers azpy)2 ]·4,4’-azpy·9H2 O}n (4). Remarkably, the effect of the addition of the azo group in 4 compared with Photophysical properties 2 and 3 has led to a CP with the same molecular arrangement but different crystal packing, allowing the introduction of one non-coordinated 4,4’-azpy and nine water molecules. Finally, their solid-state UV-Vis and photoluminescence have been measured observing their blue-emitting properties. © 2022 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/) 1. Introduction avoiding heavy atom effects in fluorescence materials [16]. How- ever, this structural diversity requires of a precise control of the The rational design of coordination polymers (CPs) by means synthetic conditions such as solvent [17], ratio of reactants [18], or of crystal engineering has emerged as a hot topic during the last temperature [19], in order to achieve the desired CPs. decades [1–3], providing a tool for chemist to design specific ar- In this scenario, the approach consisting on the preparation rangements with potential applications in fluorescence [4,5], mag- of CPs with the same molecular arrangement by changing some netism [6,7], or catalysis [8], among others [9,10]. characteristics of their starting ligands (mainly functional groups In this context, d10 metal ions have been specially utilized ow- and/or ligand lengths) has been successfully employed to pre- ing to their close-shell configuration, which provides variable ge- pare diverse families of CPs and studying their properties [20– ometries and therefore, structural diversity to the resulting CPs 22]. Nonetheless, these small changes can also influence the struc- [11,12]. Among them, those presenting bigger ionic radii such ture of CPs leading to the obtention of products with differ- Cd(II) offer a wide range of coordination numbers oscillating be- ent molecular and/or supramolecular structures [23,24]. Therefore, tween two and eight [13]. Their size combined with its relatively given our previous experience in the preparation of ACA-based high electronegativity compared with the rest of d10 metal ions complexes containing Zn(II) and Cd(II) as metal nodes [25–29], [14,15], confers it the possibility to reach a larger number of co- in this contribution we have prepared four Cd(II) CPs containing ordination bonds with more ionic character, which is pursued for ACA as a common ligand and four different N,N-donor spacers (pyrazine, pyz; 4,4’-bipyridine, 4,4’-bipy; 1,2-bis(4-pyridyl)ethylene, 1,2-bpe; 4,4’-azopyridine, 4,4’-azpy) presenting different lengths, ∗ Corresponding author. ranging from ∼2.80 Å to 9.44 Å, as well as an additional func- E-mail address: josefina.pons@uab.es (J. Pons). tionality in 4,4’-azpy. From the reactions between Cd(OAc)2 ·2H2 O, https://doi.org/10.1016/j.molstruc.2022.134896 0022-2860/© 2022 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/) D. Ejarque, T. Calvet, M. Font-Bardia et al. Journal of Molecular Structure 1277 (2023) 134896 Scheme 1. Outline of the synthesis of CPs 1-4. α -acetamidocinnamic acid (HACA) and the corresponding linkers, carried on a Thermo Scientific Flash 20 0 0 CHNS Analyzer. FTIR-ATR we have successfully synthesized four CPs referred as {[Cd2 (μ- spectra were recorded on a Perkin Elmer spectrometer, equipped ACA)2 (ACA)2 (pyz)(H2 O)2 ]·2EtOH}n (1), [Cd2 (μ-ACA)2 (ACA)2 (4,4’- with an attenuated total reflectance (ATR) accessory model MKII bipy)2 ]n (2), [Cd2 (μ-ACA)2 (ACA)2 (1,2-bpe)2 ]n (3), and {[Cd2 (μ- Golden Gate with diamond window in the range 40 0 0-50 0 cm−1 . ACA)2 (ACA)2 (4,4’-azpy)2 ]·4,4’-azpy·9H2 O}n (4) (Scheme 1). The 1 H, 13 C{1 H} and DEPT-135 NMR spectra were recorded on a Bruker crystal structures of the four CPs have been elucidated and ana- Ascend 300 MHz spectrometer in DMSO-d6 solutions at RT. All the lyzed. The effects generated by the change in length of the differ- chemical shifts (δ ) are given in ppm relative to tetramethylsilane ent linkers as well as the introduction of the N=N group in the (Me4 Si) as internal standard. Solid-state UV-Vis spectra were car- 4,4’-azpy ligand of 4 have been discussed. Finally, we have studied ried out using a Cary 40 0 0 spectrophotometer between 20 0-80 0 the solid-state absorption and emission properties of the resulting nm. Solid-state photoluminescence measurements were recorded compounds. using a Varian Cary Eclipse Fluorescence spectrophotometer. CIE 1931 chromaticity diagram was generated using Origin Pro 2019b 2. Experimental software. 2.1. Materials and general details 2.2. Synthesis of compound 1 Cd(OAc)2 ·2H2 O, HACA, pyz, 4.4’-bipy, 1,2-bpe, 4,4’-azpy ligands, An EtOH solution (8 mL) of Cd(OAc)2 ·2H2 O (100 mg, 0.375 and acetone, diethyl ether (Et2 O), and ethanol (EtOH) as solvents mmol) was added dropwise to an EtOH solution (10 mL) of HACA were purchased from Sigma-Aldrich. All of them were used with- (156 mg, 0.760 mmol) and pyz (15.1 mg, 0.189 mmol) at RT. The out further purification. The water used for the preparation of 2-4 solution was stirred during 24 h, and then it was kept evaporating was obtained with a Milli-Q® system (18.2 M·cm). Deuterated at RT during 10 days until a white crystalline solid precipitated. dimethylsulfoxide (DMSO-d6 ) was used for the NMR experiments The resulting product was filtered, washed with 10 mL of cold Et2 O and was purchased from Eurisotop. The reactions and manipula- (repeated twice), and dried under vacuum. Single crystals suitable tions for the obtention of 1 were carried out at room temperature for X-ray diffraction were obtained after layering 2 mL of hexane (RT), while those for the synthesis of 2-4 were done in a Digiheat- above 2 mL of a solution of the reaction mixture and kept it undis- TFT furnace (JP Selecta) using sealed vials under autogenous pres- turbed at RT for four days. sure, and a cooling ramp from 90 °C to RT (SI: Fig. S1). Powder 1. Yield: 167 mg (71.2%) (based on Cd). Elemental analysis calc. X-ray diffraction (PXRD) patterns were measured with a Panalyti- (%) for C52 H60 Cd2 N6 O16 (1249.88): C 49.97; H 4.84; N 6.72; found: cal X’pert PRO MPD apparatus using a monochromatic CuKα radi- C 49.74; H 4.72; N 6.55. FTIR-ATR (wavenumber, cm−1 ): 3355(w) ation with λ = 1.5406 Å. All of them were recorded from 2θ = 5° [ν (O-H)], 3249(m) [ν (N-H)], 3168-3024(br) [ν (C-H)ar + ν (C-H)alk ], to 30° with a step scan of 0.01671°. Elemental analyses (EA) were 2982-2934(br) [ν (C-H)al ], 1677(w), 1663(w), 1648(m) [ν (C=O)], 2 D. Ejarque, T. Calvet, M. Font-Bardia et al. Journal of Molecular Structure 1277 (2023) 134896 1549(w) [ν (C=C/C=N)], 1516(s) [ν as (COO)], 1492(m), 1446(w), nm → λem = 358, 422, 491 nm; λexc = 315 nm → λem = 361, 1416(s) [ν s (COO)], 1399(s) [δ (C=C/C=N)], 1370(s) [ν s (COO)], 377, 392 nm. 1357(s) [δ (C=C/C=N)], 1279(m), 1212(w), 1185(w), 1159(w), 3. Yield: 85.7 mg (65.0%) (based on Cd). Elemental analysis 1128(w), 1110(w), 1083(w), 1059(w), 1047(m) [δ ip (C-H)], 1031(w), calc. (%) for C68 H60 Cd2 N8 O12 (1406.07): C 58.09; H 4.30; N 7.97; 1004(w), 984(w), 974(w), 943(w), 918(w), 893(w), 877(w), 856(w), found: C 57.86; H 4.18; N 7.72. FTIR-ATR (wavenumber, cm−1 ): 846(w), 813(w), 788(w), 780(w), 766(m) [δ oop (C-H)], 752(w), 3402(w) [ν (N-H)], 3062-3028(br) [ν (C-H)ar + ν (C-H)alk ], 2985- 727(w), 690(s) [δ oop (C-H)], 597(m), 565(m), 545(m), 518(s). 1 H 2941(br) [ν (C-H)al ], 1686(w), 1661(m) [ν (C=O)], 1640(w), 1609(m), NMR (300 MHz; DMSO-d6 ; Me4 Si; 298 K): δ = 9.17 [4H, s, NHACA ], 1563(sh) [ν (C=C/C=N)], 1547(s) [ν as (COO)], 1484(w) [ν as (COO)], 8.66 [4H, s, Hpyz ], 7.50 [8H, d, 3 J = 7.2 Hz, o-HACA ], 7.35 [8H, 1445(w), 1429(w), 1387(s) [ν s (COO)], 1362(sh) [δ (C=C/C=N)], t, 3 J = 7.5 Hz, m-HACA ], 7.27 [8H, m, p-HACA + NH-C-CHACA ], 1332(m), 1309(m), 1255(m), 1221(sh), 1209(w), 1181(w), 1157(w), 4.34 [2H, t, 3 J = 5.1 Hz, OHEtOH ], 3.44 [4H, qd, 3 J = 7.0 Hz, 1120(w), 1101(m), 1077(w), 1073(w), 1017(m) [δ ip (C-H)], 1002(w), 4 J = 5.1 Hz, CH , 2 EtOH ], 1.96 [12H, s, CO-CH3 ,ACA ], 1.05 [6H, t, 960(w), 936(w), 842(m), 793(w), 771(m) [δ oop (C-H)], 740(m), 3 J = 7.0 Hz, CH , 3 EtOH ]. 13 C{1 H} NMR (75 MHz; DMSO-d ; Me Si; 6 4 692(s) [δ oop (C-H)], 588(w), 552(s), 534(s). 1 H NMR (300 MHz; 298 K): δ = 171.5 [NH-COACA ], 168.1 [COOACA ], 145.2 [Cpyz ], DMSO-d6 ; Me4 Si; 298 K): δ = 9.18 [2H, s, NHACA ], 8.61 [4H, 135.2 [O2 C-CACA ], 129.5 [HN-C-CH-CACA ], 129.3 [o-CACA ], 129.0 d, 3 J = 5.7 Hz, o-H1,2-bpe ], 7.62 [4H, dd, 3 J = 4.1 Hz, 4 J = 1.5 [p-CACA ], 128.2 [m-CACA ], 128.0 [NH-C-CH-CACA ], 56.0 [CH2 ,EtOH ], Hz, m-H1,2-bpe ], 7.55 [2H, s, py-CH1,2-bpe ], 7.50 [4H, d, 3 J = 7.3 23.0 [CO-CH3 ,ACA ], 18.6 [CH3 ,EtOH ]. DEPT-135 NMR (75 MHz; Hz, o-HACA ], 7.35 [4H, t, 3 J = 7.3 Hz, m-HACA ], 7.27 [4H, m, p- DMSO-d6 ; Me4 Si; 298 K): δ = 145.2 [Cpyz ], 129.2 [o-CACA ], 128.9 HACA + NH-C-CHACA ], 1.96 [6H, s, CO-CH3 ,ACA ]. 13 C{1 H} NMR (75 [p-CACA ], 128.2 [m-CACA ], 128.0 [NH-C-CH-CACA ], 56.0 [CH2 ,EtOH ], MHz; DMSO-d6 ; Me4 Si; 298 K): δ = 171.3 [NH-COACA ], 168.2 23.0 [CO-CH3 ,ACA ], 18.5 [CH3 ,EtOH ]. UV-Vis: λmax-Abs = 252, 302 [COOACA ], 150.2 [o-C1,2-bpe ], 143.5 [N-CH-CH-C1,2-bpe ], 135.1 [O2 C- nm. Fluorescence: λexc = 262 nm → λem = 359, 422, 491 nm; CACA ], 130.7 [py-CH1,2-bpe ], 129.5 [HN-C-CH-CACA ], 129.3 [o-CACA ], λexc = 315 nm → λem = 360, 376, 392 nm. 129.0 [p-CACA ], 128.3 [m-CACA ], 128.1 [NH-C-CH-CACA ], 121.4 [m- C1,2-bpe ], 23.0 [CO-CH3 ,ACA ]. DEPT-135 NMR (75 MHz; DMSO-d6 ; Me4 Si; 298 K): δ = 150.2 [o-C1,2-bpe ], 130.6 [py-CH1,2-bpe ], 129.3 2.3. Synthesis of compounds 2-4 [o-CACA ], 128.9 [p-CACA ], 128.2 [m-CACA ], 128.1 [NH-C-CH-CACA ], 121.3 [m-C1,2-bpe ], 23.0 [CO-CH3 ,ACA ]. UV-Vis: λmax-Abs = 276, 329 For 2 and 3, a hot Milli-Q water solution (1.0 mL, 2; 3.0 mL, 3) nm. Fluorescence: λexc = 262 nm → λem = 360, 421, 492 nm; of Cd(OAc)2 ·2H2 O (50.0 mg, 0.188 mmol) was added dropwise to a λexc = 315 nm → λem = 362, 377, 391 nm. hot Milli-Q water solution (4.0 mL) of HACA (77.0 mg, 0.375 mmol) 4. Yield: 12.2 mg (55.6%) (based on 4,4’-azpy). Elemental anal- and 0.188 mmol of the corresponding N,N-donor spacer (4,4’-bipy, ysis calc. (%) for C74 H82 Cd2 N16 O21 (1756.36): C 50.60; H 4.71; 2; 1,2-bpe, 3). The preparation of 4 was done using the same molar N 12.76; found: C 50.84; H 4.49; N 12.91. FTIR-ATR (wavenum- ratio as for 2 and 3 but starting from 0.5 mL of a hot Milli-Q water ber, cm−1 ): 3389-2639(br) [ν (O-H)+ν (N-H)+ν (C-H)], 1670(sh), solution of Cd(OAc)2 ·2H2 O (10 mg, 0.038 mmol), and a hot solu- 1655(w) [ν (C=O)], 1645(w), 1598(w), 1567(sh) [ν (C=C/C=N)], tion of Milli-Q water/EtOH (1.25 mL/25.0 μL) with the ligands. The 1544(s) [ν as (COO)], 1536(s), 1527(s) [ν as (COO)], 1513(sh), 1492(m), resulting solutions of 2-4 were kept at 90 °C during 2 h and then, 1446(w), 1398(s) [ν s (COO)], 1364(s) [δ (C=C/C=N)], 1325(sh), they were cooled down to RT using a temperature ramp (SI: Fig. 1285(w), 1224(w), 1212(w), 1185(w), 1140(w), 1123(w), 1081 (w), S1), obtaining single crystals suitable for X-ray diffraction when the 1051(w), 1030(w), 1016(m) [δ ip (C-H)], 983(w), 964(w), 929(w), cooling ramp was completed for 2 and 3, while the single crystals 917(w), 842(w), 784(w), 775(m) [δ oop (C-H)], 744(w), 693(m) of 4 were obtained after keeping the vials undisturbed at RT for [δ oop (C-H)], 608(w), 593(w), 567(m), 544(w), 524(m). 1 H NMR three days once the cooling ramp was completed. All the crystals (300 MHz; DMSO-d6 ; Me4 Si; 298 K): δ = 9.15 [4H, s, NHACA ], were filtered, washed twice with 5 mL of acetone, and dried under 8.88 [12H, dd, 3 J = 4.6 Hz, 4 J = 1.4 Hz, o-H4,4’-azpy ], 7.81 [12H, vacuum. dd, 3 J = 4.6 Hz, 4 J = 1.5 Hz, m-H4,4’-bipy ], 7.48 [8H, d, 3 J = 7.0 2. Yield: 99.3 mg (78.2%) (based on Cd). Elemental analysis calc. Hz, o-HACA ], 7.34 [8H, t, 3 J = 7.3 Hz, m-HACA ], 7.27 [4H, d, p-HACA , (%) for C64 H56 Cd2 N8 O12 (1354.00): C 56.77; H 4.17; N 8.28; found: 3 J = 7.2 Hz], 7.25 [4H, s, NH-C-CH ACA ], 1.95 [12H, s, CO-CH3 ,ACA ]. C 56.62; H 4.02; N 8.39. FTIR-ATR (wavenumber, cm−1 ): 3410(w) 13 C{1 H} NMR (75 MHz; DMSO-d ; Me Si; 298 K): δ = 171.4 6 4 [ν (N-H)], 3090-3060(br) [ν (C-H)ar + ν (C-H)alk ], 2983-2874(br) [NH-COACA ], 168.2 [COOACA ], 156.4 [N-CH-CH-C4,4’-azpy ], 151.9 [o- [ν (C-H)al ], 1687(w), 1660(s) [ν (C=O)], 1641(sh), 1604(m), 1554(s) C4,4’-azpy ], 135.2 [O2 C-CACA ], 129.6 [HN-C-CH-CACA ], 129.4 [o-CACA ], [ν (C=C/C=N)], 1543(s) [ν as (COO)], 1492(w) [ν as (COO)], 1477(w), 129.1 [p-CACA ], 128.4 [m-CACA ], 128.2 [NH-C-CH-CACA ], 116.2 [m- 1448(w), 1415(sh), 1388(s) [ν s (COO)], 1349(s) [δ (C=C/C=N)], C4,4’-azpy ], 23.1 [CO-CH3 ,ACA ]. DEPT-135 NMR (75 MHz; DMSO-d6 ; 1329(s), 1255(m), 1223(m), 1184(w), 1162(w), 1125(w), 1077(m) Me4 Si; 298 K): δ = 151.9 [o-C4,4’-azpy ], 129.4 [o-CACA ], 129.1 [p- [δ ip (C-H)], 1044(w), 1033(w), 1012(w), 967(w), 935(w), 864(w), CACA ], 128.4 [m-CACA ], 128.2 [NH-C-CH-CACA ], 116.2 [m-C4,4’-azpy ], 855(w), 821(m), 792(m), 771(s) [δ oop (C-H)], 746(m), 733(m), 690(s) 23.1 [CO-CH3 ,ACA ]. UV-Vis: λmax-Abs = 285, 345, 470 nm. Fluores- [δ oop (C-H)], 675(w), 662(w), 632(m), 597(sh), 589(w), 574(w), cence: λexc = 262 nm → λem = 359, 422, 493 nm; λexc = 315 543(sh), 531(w), 521(sh). 1 H NMR (300 MHz; DMSO-d6 ; Me4 Si; nm → λem = 374, 386 nm; λexc = 470 nm → λem = 484 nm. 298 K): δ = 9.18 [4H, s, NHACA ], 8.73 [8H, d, 3 J = 4.1 Hz, o- H4,4’-bipy ], 7.84 [8H, d, 3 J = 4.1 Hz, m-H4,4’-bipy ], 7.50 [8H, d, 2.4. X-ray crystallographic data 3 J = 6.8 Hz, o-H 3 J = 7.1 Hz, m-H ACA ], 7.35 [8H, t, ACA ], 7.28 [8H, m, p-HACA + NH-C-CHACA ], 1.96 [12H, s, CO-CH3 ,ACA ]. 13 C{1 H} Colorless (1-3) and red-prism (4) specimens were used for NMR (75 MHz; DMSO-d6 ; Me4 Si; 298 K): δ = 171.3 [NH-COACA ], the X-ray crystallographic analysis. The X-ray intensity data were 168.2 [COOACA ], 150.6 [o-C4,4’-bipy ], 144.4 [N-CH-CH-C4,4’-bipy ], 135.2 measured on a D8 Venture system equipped with a multilayer [O2 C-CACA ], 129.5 [HN-C-CH-CACA ], 129.3 [o-CACA ], 128.9 [p-CACA ], monochromator and a Mo microfocus (λ = 0.71073 Å). For all the 128.3 [m-CACA ], 128.1 [NH-C-CH-CACA ], 121.3 [m-C4,4’-bipy ], 23.0 [CO- compounds, the frames were integrated using the Bruker SAINT CH3 ,ACA ]. DEPT-135 NMR (75 MHz; DMSO-d6 ; Me4 Si; 298 K): software package using a narrow-frame algorithm. The struc- δ = 150.6 [o-C4,4’-bipy ], 129.3 [o-CACA ], 128.9 [p-CACA ], 128.3 [m- tures were solved and refined using a SHELXTL Software Package CACA ], 128.1 [NH-C-CH-CACA ], 121.3 [m-C4,4’-bipy ], 23.0 [CO-CH3 ,ACA ]. (version-2018/3) [30]. The integration of the data with a 0.80 Å UV-Vis: λmax-Abs = 264, 290 nm. Fluorescence: λexc = 262 (1), 0.68 Å (2), 0.79 Å (3) and 0.73 Å (4) resolution, gave an av- 3 D. Ejarque, T. Calvet, M. Font-Bardia et al. Journal of Molecular Structure 1277 (2023) 134896 Table 1 Crystal data and structure refinement for 1-4. 1 2 3 4 Empirical Formula C26 H30 CdN3 O8 C32 H28 CdN4 O6 C34 H30 CdN4 O6 C74 H82 Cd2 N16 O21 Formula weight 624.93 676.98 703.02 1756.35 T (K) 100(2) 100(2) 100(2) 100(2) Wavelength (Å) 0.71073 0.71073 0.71073 0.71073 System, space group Monoclinic, P21 /c Triclinic, P1 Triclinic, P1 Monoclinic, P21 Unit cell dimensions a (Å) 20.080(3) 10.770(2) 10.396(4) 13.6110(5) b (Å) 8.5048(13) 10.957(2) 11.761(5) 22.8777(11) c (Å) 15.726(2) 13.512(3) 13.096(6) 14.3548(7) α (°) 90 87.154(7) 91.794(14) 90 β (°) 101.199(5) 86.938(7) 92.560(15) 117.209(2) γ (°) 90 65.068(7) 102.342(15) 90 V (Å3 ) 2634.5(7) 1443.2(5) 1561.3(12) 3975.3(3) Z 4 2 2 2 Dcalc (mg/m3 ) 1.576 1.558 1.495 1.467 μ (mm-1) 0.883 0.809 0.751 0.617 F (000) 1276 688 716 1804 Crystal size (mm−3 ) 0.043 × 0.036 × 0.016 0.269 × 0.046 × 0.044 0.134 × 0.029 × 0.012 0.253 × 0.038 × 0.033 hkl ranges -23<=h<=25, -15<=h<=15, -13<=h<=13, -18<=h<=17, -10<=k<=10, -15<=k<=15, -14<=k<=14, -31<=k<=31, -19<=l<=19 0<=l<=19 0<=l<=16 -19<=l<=19 θ range (°) 2.068 to 26.461 2.051 to 31.307 2.008 to 26.696 1.595 to 29.217 Reflections collected/unique/[Rint ] 20116/5415/0.1824 8914/8914/0.0906 6441/6441/0.1488 149152/21525/0.0718 Completeness to θ (%) 99.9 99.1 99.3 100.0 Absorption correction Semi-empirical from Semi-empirical from Semi-empirical from Semi-empirical equivalents equivalents equivalents from equivalents Max. and min. transmission 0.7454 and 0.5210 0.7461 and 0.5441 0.7454 and 0.5717 0.7458 and 0.6510 Refinement method Full-matrix Full-matrix Full-matrix Full-matrix least-squares on |F| least-squares on |F| least-squares on |F| least-squares on |F| 2 2 2 2 Data/Restrains/Parameters 5415/0/322 8914/4/390 6441/0/408 21525/9/1077 Goodness-on-fit on F2 1.050 0.828 0.882 1.028 Final R indices [I>2σ (I)] R1 = 0.1060, R1 = 0.0358, R1 = 0.0546, R1 = 0.0357, wR2 = 0.1831 wR2 = 0.0659 wR2 = 0.0910 wR2 = 0.0805 R indices (all data) R1 = 0.1691, R1 = 0.0590, R1 = 0.0969, R1 = 0.0409, wR2 = 0.2082 wR2 = 0.0703 wR2 = 0.1012 wR2 = 0.0832 Extinction coefficient n/a n/a n/a n/a Largest diff-peak and hole (e. Å−3 ) 1.693 and -1.811 3.060 and -1.105 1.387 and -1.059 1.933 and -0.649 erage redundancy of 3.715 (1), 1.0 0 0 (2), 1.0 0 0 (3) and 6.929 (4), (pyz, 1; 4,4’-bipy, 2; 1,2-bpe, 3; 4,4’-azpy, 4). All the CPs were a completeness of 99.6% (1), 94.6% (2), 97.5% (3) and 99.9% (4), obtained as crystalline materials, which were used for the further Rsig of 19.19% (1), 12.44% (2), 15.48% (3), and 4.20% (4), present- characterization and photophysical properties measurements. ing 3325 (61.40%) (1), 6305 (70.73%) (2), 4066 (63.13%) (3), and Compound 1 was prepared using a 1:2:0.5 molar ratio in EtOH 20027 (93.04%) (4) reflections greater than 2σ (|F|2 ). at RT. Otherwise, compounds 2-4 were obtained using a 1:2:1 For 1-4 the final cell constants and volume are based upon re- molar ratio and Milli-Q water, starting the reactions at 90 °C and finement of the XYZ-centroids of reflections above 20 σ (I). Data following a cooling ramp (SI: Fig. S1). Interestingly, the addition of were corrected for absorption effects using the Multi-Scan method a 1.7% of EtOH to the reaction media in 4 results in a remarkable (SADABS). Crystal data and additional details of structure refine- enhancement of the quality of the crystals. Furthermore, all the ment for 1-4 are reported in Table 1. Complete information about assays for obtaining 1 using the same synthetic conditions as the crystal structure and molecular geometry is available in CIF for the obtention of 2-4 yielded the monomer [Cd(ACA)2 (H2 O)2 ] format via CCDC 2222663 (1), 2222662 (2), 2222664 (3), and [25] independently of the utilized stoichiometry. Otherwise, the 2222665 (4). use of EtOH resulted in the obtention of 1, and the increase of Molecular graphics were generated using Mercury 4.3.1 soft- equivalents of pyz lead to the same product with lower yields. ware [31], with the POV-Ray image package [32], and Olex2 soft- ware [33]. The color codes for all the molecular graphics are as 3.2. General characterization follows: light orange (Cd), red (O), light blue (N), gray (C), and white (H). All the accessible void volumes have been calculated Compounds 1-4 were characterized by PXRD, EA, FTIR-ATR, 1 H, with Mercury 4.3.1 software [31], using a probe radius of 1.2 Å 13 C{1 H},DEPT-135 NMR spectroscopies, and single crystal X-ray [34]. The evaluation of the geometry distortion of the Cd(II) cores diffraction method. Phase purity of the bulk samples of 1-4 were in 1-4 has been done using version 2.1 of SHAPE software from verified by PXRD (SI: Figs. S2-S5). Moreover, the EA agree with the the corresponding CIF files [35]. The resulting topologies were an- proposed formulas. In the FTIR-ATR spectra we observe the bands alyzed with the ToposPro 5.3.3.4 and Gavrog Systre (version 1.2.0 attributable to the ACA and N,N-donor spacers. The absence of a beta2) programs and the TopCryst website (https://topcryst.com). strong band at 1637 cm−1 corresponding to ν (COOH)HACA , indicates that the HACA ligand is deprotonated in all the CPs. The four spec- 3. Results and discussion tra display the characteristic bands between 1547-1484 cm−1 for 3.1. Preparation of 1-4 ν as (COO) and 1416-1370 cm−1 for ν s (COO), whose difference re- sults in the value [36,37], being 146 and 100 cm−1 (1), 155 and The four CPs were prepared from the reaction of 104 cm−1 (2), 160 and 97 cm−1 (3), and 146 and 129 cm−1 (4), Cd(OAc)2 ·2H2 O, HACA and their corresponding N,N-donor spacer which suggest bidentate bridged-chelated (μ2 -η1 :η1 ), and chelated 4 D. Ejarque, T. Calvet, M. Font-Bardia et al. Journal of Molecular Structure 1277 (2023) 134896 (μ2 -η2 ) coordination modes of the carboxylate groups. Addition- torted capped trigonal prismatic geometry (Fig. 1b; SI: Table S1). ally, other bands of the ACA corresponding to the ν (N-H) and The crystal structure also contains two equivalent non-coordinated ν (C=O) signals have also been identified, as well as the typi- EtOH molecules, which are placed on voids with an accessible vol- cal bands from the aromatic rings (ν (C=C/C=N) and δ (C=C/C=N)) ume of 48.61 Å3 (1.8% of the unit cell volume) [34] generated from either ACA and the corresponding spacers [38]. Furthermore, by the supramolecular scaffold of the CP. In addition, their bond the presence of a broad band between 3355-2862 cm−1 (1) and lengths and bond angles oscillate between 2.279(8)-2.451(8) Å and 3389-1639 cm−1 (4) has been attributed to ν (O-H) of solvent 54.9(2)-159.9(3)°, showing similar values than other Cd(II) ladder- molecules (SI: Figs. S6-S9). type CPs presenting pyz ligands as single pillars (Table 2) [39,40]. The 1 H NMR spectra of 1-4 were recorded in DMSO-d6 solu- The intramolecular interactions of 1 are based on a C-H···O in- tions to ascertain the molar ratio between the ligands (SI: Figs. teraction between an o-H from pyz and a carboxylate oxygen atom S10-S13). All the spectra display a signal between 9.18-9.15 ppm from the μ2 -η2 ACA ligands (Fig. 1a). The intermolecular interac- attributable to the amide H-atom, while the signals corresponding tions form 2D layers along the (200) plane (Fig. 1c) resulting in a to the N,N-donor spacers appeared at 8.66 (1), 8.73 and 7.84 (2), hxl topology. This layers are mainly originated by the coordinated 8.61-7.55 (3), and 8.88 and 7.81 (4). In addition, the aromatic and water molecules that joint together the polymeric chains, forming the alkene hydrogen atoms from ACA are found between 7.50-7.25 two H-bonds with one oxygen atom from the μ2 -η1 :η1 ACA ligand ppm, while the methyl H-atoms are shown around 1.95 ppm. The and one oxygen atom from the μ2 -η2 carboxylate group as accep- 1 H NMR spectra of the four CPs confirm their different ACA:spacer tors. The 2D plane is also supported by H-bonds promoted by the ratio, being 4:1 (1), 4:2 (2 and 3), and 4:3 (4), which is in agree- NH and C=O groups from the amide moieties from ACA, which in- ment with the elucidated crystal structures [38]. teract with nearby μ2 -η1 :η1 linked oxygen atoms from carboxylate The 13 C{1 H} and DEPT-135 NMR spectra of 1-4 have also been ACA ligands and non-coordinated EtOH molecules, as well as C- recorded using DMSO-d6 as solvent, observing the typical signals H···π interactions involving the EtOH molecules and the polymeric corresponding to the carbonyl (171.5-171.3 ppm) and carboxylate chains (Fig. 1d). (168.2-168.1 ppm) carbon atoms from ACA in the downfield region, followed by the carbon atoms from the N,N-donor linkers, which 3.4. Crystal structure of complexes 2-4 appeared between 151.9 and 130.7 ppm. In this region, the aro- matic and alkene carbon atoms from ACA are also shown between Compounds 2-4 belong to the triclinic P1 (2, 3) and monoclinic 135.2 and 128.9 ppm, while the methyl carbon atoms from ACA ap- P21 (4) space groups. They consist of 1D ladder-type CPs expanded peared in the up-field region of the spectra around 23.0 ppm (SI: along the [11̄0] (2), [220] (3) and [100] (4) directions (Figs. 2a- Figs. S14-S17). c), which are formed by dimeric SBUs connected by double pil- lars of 4,4’-bipy (2), 1,2-bpe (3) and 4,4’-azpy (4) linkers, show- 3.3. Crystal and extended structure of complex 1 ing different degrees of distortion between the pyridyl rings of their corresponding spacers (Figs. 2d-e). Remarkably, compound 4 The compound belongs to the monoclinic P21 /c space group. contains one non-coordinated 4,4’-azpy and nine water molecules It consists of a 1D zig-zag CP expanded along the [010] direction located in voids of 257.56 Å3 (6.5% of the unit cell) [34], gener- through dimeric secondary building units (SBUs) connected by a ated by their supramolecular scaffold along the [100] direction. pyz linker acting as a single pillar (Fig. 1a). These SBUs are formed The three CPs present the same SBU formed by two μ2 -η1 :η1 by two equivalent Cd(II) centers with [CdO6 N] cores connected by ACA ligands joining the metal nodes and two μ2 -η2 ACA ligands, two ACA ligands presenting a μ2 -η1 :η1 coordination mode. In ad- that combined with two linkers per metal ion form [CdO5 N2 ] dition, a pair of μ2 -η2 ACA, a water and a pyz molecules complete cores, presenting distorted pentagonal bipyramid geometries (SI: the coordination sphere of both Cd(II) centers, displaying a dis- Table S1). Moreover, the bond lengths and bond angles range be- Fig. 1. (a) Molecular structure of compound 1. (b) Dimeric SBU. (c) General and (d) In detail views of the intermolecular interactions expanding the structure through the (200) plane. All the atoms not involved in the highlighted interactions have been omitted for clarity. 5 D. Ejarque, T. Calvet, M. Font-Bardia et al. Journal of Molecular Structure 1277 (2023) 134896 Table 2 Selected bond lengths (Å), bond angles (°), intra- and intermolecular interactions (Å) for 1. Bond lengths (Å) Cd(1)-O(1) 2.339(7) Cd(1)-O(4) 2.348(7) Cd(1)-O(7) 2.297(8) Cd(1)-O(1)#1 2.437(7) Cd(1)-O(5) 2.318(7) Cd(1)-N(3) 2.279(8) Cd(1)-O(2) 2.451(8) Bond angles (°) O(1)-Cd(1)-O(1)#1 72.9(3) (1)#1-Cd(1)-O(4) 91.5(2) O(2)-Cd(1)-N(3) 84.1(3) O(1)-Cd(1)-O(2) 54.9(2) (1)#1-Cd(1)-O(5) 81.8(2) O(4)-Cd(1)-O(5) 56.6(3) O(1)-Cd(1)-O(4) 93.9(3) (1)#1-Cd(1)-O(7) 159.9(3) O(4)-Cd(1)-O(7) 86.3(3) O(1)-Cd(1)-O(5) 140.7(3) 1)#1-Cd(1)-N(3) 81.2(3) O(4)-Cd(1)-N(3) 156.2(3) O(1)-Cd(1)-O(7) 127.2(3) (2)-Cd(1)-O(4) 119.0(2) (5)-Cd(1)-O(7) 80.3(3) O(1)-Cd(1)-N(3) 105.3(3) (2)-Cd(1)-O(5) 159.2(2) (5)-Cd(1)-N(3) 99.8(3) O(1)#1-Cd(1)-O(2) 118.9(2) (2)-Cd(1)-O(7) 79.1(3) (7)-Cd(1)-N(3) 92.8(3) Intramolecular interactions (Å) D-H···A D-H (Å) H···A (Å) D···A (Å) >D-H···A (°) C(23)-H(23)···O(4) 0.95 2.33 3.244(13) 160 Intermolecular interactions (Å) D-H···A D-H (Å) H···A (Å) D···A (Å) >D-H···A (°) O(7)-H(7A)···O(4) 0.67(16) 2.12(16) 2.729(13) 151(17) O(7)-H(7B)···O(3) 0.73(14) 2.03(15) 2.721(12) 158(16) N(1)-H(1N)···O(1W) 0.88 2.15 3.008(12) 165 N(2)-H(2N)···O(2) 0.88 2.10 2.939(11) 158 X-H···Cg(J) H···Cg(J) (Å) H-Perpa (Å) γ (°)b X-H···Cg(J)c X···Cg(J) (Å) X-H, Pid C(1W)-H(1WB)···Cg(1) 2.95 2.70 24.18 143 3.788(16) 54 C(19)-H(19)···Cg(1) 2.69 2.67 6.71 147 3.525(12) 64 a Perpendicular distance of H to ring plane J. b Angle between Cg(J)-H vector and ring J normal. c X-H···Cg(J) angle. d Angle of the X-H bond with the Pi-plane (Perpendicular = 90°, Parallel = 0°). #1: -x+1,-y+1,-z+1; Cg(1) = C(4) C(5) C(6) C(7) C(8) C(9). tween 2.310(2)-2.4832(17) Å and 54.59(6)-163.93(5)° (2), 2.258(4)- tion of water molecules should be higher than in the rest of link- 2.487(3) Å and 53.84(11)-177.22(14)° (3), and 2.310(3)-2.520(3) Å ers [49]. These results are in line with the observations regarding and 53.34(11)-174.00(16)° (4), showing similar values than other the obtention of 1, since the trials to synthesize it using the same ladder-type Cd(II) CPs with the same linkers [41–44] (Table 3). synthetic conditions as for the rest of compounds always promote The different molecular arrangement of the studied CPs consist- the coordination of water molecules instead of pyz, leading to the ing on the presence of single (1) or double pillars (2-4) could be [Cd(ACA)2 (H2 O)2 ] monomer. attributed to the difference in pKa values of the utilized N,N-donor The intramolecular interactions of 2-4 consist of π ···π and C- spacers (pyz, 0.6 [45]; 4,4’-bipy, 3.17 [46]; 1,2-bpe, 3.89 [47]; 4,4’- H···O interactions. The torsion angles between the aromatic rings azpy, 2.19 [48]). These values show that pyz presents the less coor- from the linkers evinced the higher planarity of 1,2-bpe (4.88°) and dinating ability and therefore, their competition with the coordina- 4,4’-azpy (4.39 and 14.86°) in 3 and 4 compared with the 4,4’-bipy Fig. 2. Molecular structure of compounds (a) 2, (b) 3, and (c) 4. In detail views of the SBUs in (d) 2 and 3, and (e) 4. All the atoms not involved in the highlighted interactions have been omitted for clarity. 6 D. Ejarque, T. Calvet, M. Font-Bardia et al. Journal of Molecular Structure 1277 (2023) 134896 Table 3 Selected bond lengths (Å) and bond angles (°) for 2-4. 2 Bond lengths (Å) Cd(1)-O(1) 2.3839(18) Cd(1)-O(4)#2 2.3448(17) Cd(1)-N(3) 2.310(2) Cd(1)-O(2) 2.4012(19) Cd(1)-O(5) 2.3874(16) Cd(1)-N(4)#1 2.311(2) Cd(1)-O(4) 2.4832(17) Bond angles (°) O(1)-Cd(1)-O(2) 54.92(6) O(2)-Cd(1)-O(4)#2 145.31(6) O(4)-Cd(1)-N(4)#1 85.33(7) O(1)-Cd(1)-O(4) 163.93(5) O(2)-Cd(1)-O(5) 85.33(6) O(4)#2-Cd(1)-O(5) 128.82(6) O(1)-Cd(1)-O(4)#2 90.53(6) O(2)-Cd(1)-N(3) 89.01(7) O(4)#2-Cd(1)-N(3) 96.25(7) O(1)-Cd(1)-O(5) 140.13(6) O(2)-Cd(1)-N(4)#1 88.42(7) O(4)#2-Cd(1)-N(4)#1 87.91(7) O(1)-Cd(1)-N(3) 92.43(7) O(4)-Cd(1)-O(4)#2 74.26(6) O(5)-Cd(1)-N(3) 89.57(7) O(1)-Cd(1)-N(4)#1 89.05(7) O(4)-Cd(1)-O(5) 54.59(6) O(5)-Cd(1)-N(4)#1 86.62(7) O(2)-Cd(1)-O(4) 139.68(6) O(4)-Cd(1)-N(3) 94.31(7) N(3)-Cd(1)-N(4)#1 175.57(8) 3 Bond lengths (Å) Cd(1)-O(1) 2.476(3) Cd(1)-O(4)#2 2.487(3) Cd(1)-N(3) 2.258(4) Cd(1)-O(2) 2.320(3) Cd(1)-O(5)#2 2.383(3) Cd(1)-N(4)#1 2.267(4) Cd(1)-O(4) 2.371(4) Bond angles (°) O(1)-Cd(1)-O(2) 54.69(11) O(2)-Cd(1)-O(4)#2 159.32(11) O(4)-Cd(1)-N(4)#1 86.84(13) O(1)-Cd(1)-O(4) 139.81(11) O(2)-Cd(1)-O(5)#2 144.26(11) O(4)#2-Cd(1)-O(5)#2 53.84(11) O(1)-Cd(1)-O(4)#2 144.45(11) O(2)-Cd(1)-N(3) 95.22(13) O(4)#2-Cd(1)-N(3) 93.64(12) O(1)-Cd(1)-O(5)#2 90.63(11) O(2)-Cd(1)-N(4)#1 87.28(12) O(4)#2-Cd(1)-N(4)#1 83.60(12) O(1)-Cd(1)-N(3) 87.99(12) O(4)-Cd(1)-O(4)#2 75.68(12) O(5)#2-Cd(1)-N(3) 91.47(13) O(1)-Cd(1)-N(4)#1 94.46(12) O(4)-Cd(1)-O(5)#2 129.52(11) O(5)#2-Cd(1)-N(4)#1 87.19(13) O(2)-Cd(1)-O(4) 85.34(11) O(4)-Cd(1)-N(3) 92.14(13) N(3)-Cd(1)-N(4)#1 177.22(14) 4 Bond lengths (Å) Cd(1)-O(1) 2.349(3) Cd(1)-N(5) 2.318(3) Cd(2)-O(10) 2.415(3) Cd(1)-O(2) 2.370(3) Cd(1)-N(8)#1 2.318(4) Cd(2)-O(11) 2.345(3) Cd(1)-O(4) 2.334(3) Cd(2)-O(5) 2.339(3) Cd(2)-N(9) 2.310(3) Cd(1)-O(5) 2.520(3) Cd(2)-O(7) 2.503(3) Cd(2)-N(12)#2 2.317(4) Cd(1)-O(7) 2.315(3) Cd(2)-O(8) 2.373(3) Bond angles (°) O(1)-Cd(1)-O(2) 55.86(11) O(4)-Cd(1)-N(8)#1 93.35(12) O(7)-Cd(2)-O(10) 165.63(11) O(1)-Cd(1)-O(4) 81.30(12) O(5)-Cd(1)-O(7) 77.39(10) O(7)-Cd(2)-O(11) 135.96(11) O(1)-Cd(1)-O(5) 134.95(11) O(5)-Cd(1)-N(5) 82.66(11) O(7)-Cd(2)-N(9) 83.36(12) O(1)-Cd(1)-O(7) 147.65(11) O(5)-Cd(1)-N(8)#1 96.67(12) O(7)-Cd(2)-N(12)#2 100.80(12) O(1)-Cd(1)-N(5) 99.70(13) O(7)-Cd(1)-N(5) 83.17(14) O(8)-Cd(2)-O(10) 138.62(12) O(1)-Cd(1)-N(8)#1 88.20(12) O(7)-Cd(1)-N(8)#1 86.48(12) O(8)-Cd(2)-O(11) 83.37(12) O(2)-Cd(1)-O(4) 136.51(12) N(5)-Cd(1)-N(8)#1 169.52(16) O(8)-Cd(2)-N(9) 92.64(14) O(2)-Cd(1)-O(5) 165.89(10) O(5)-Cd(2)-O(7) 77.31(10) O(8)-Cd(2)-N(12)#2 93.32(13) O(2)-Cd(1)-O(7) 92.51(12) O(5)-Cd(2)-O(8) 129.96(11) O(10)-Cd(2)-O(11) 55.30(12) O(2)-Cd(1)-N(5) 86.40(11) O(5)-Cd(2)-O(10) 91.42(12) O(10)-Cd(2)-N(9) 87.61(12) O(2)-Cd(1)-N(8)#1 92.47(12) O(5)-Cd(2)-O(11) 146.59(11) O(10)-Cd(2)-N(12)#2 87.45(13) O(4)-Cd(1)-O(5) 53.77(11) O(5)-Cd(2)-N(9) 89.00(15) O(11)-Cd(2)-N(9) 92.01(14) O(4)-Cd(1)-O(7) 130.85(11) O(5)-Cd(2)-N(12)#2 87.71(13) O(11)-Cd(2)-N(12)#2 87.98(13) O(4)-Cd(1)-N(5) 94.63(13) O(7)-Cd(2)-O(8) 53.34(11) N(9)-Cd(2)-N(12)#2 174.00(16) 2. #1: x-1,y+1,z; #2: -x,-y+2,-z; 3. #1: x+1,y+1,z; #2: -x+1,-y+2,-z; 4. #1: x-1,y,z; #2: x+1,y,z. Table 4 Selected intramolecular interactions (Å) for 2-4. 2 D-H···A D-H (Å) H···A (Å) D···A (Å) >D-H···A (°) C(14)-H(14)···O(1) 0.95 2.33 3.256(4) 166 3 D-H···A D-H (Å) H···A (Å) D···A (Å) >D-H···A (°) C(14)-H(14)···O(1) 0.95 2.20 3.139(6) 170 Cg(I)···Cg(J) dCg-Cg a (Å) α b (°) β , γ c (°) dplane-plane d (Å) doffset e (Å) Cg(1)···Cg(2) 3.744(4) 4.9(3) 27.5, 23.1 3.444(2), 3.321(2) 1.729 4 D-H···A D-H (Å) H···A (Å) D···A (Å) >D-H···A (°) C(14)-H(14)···O(10) 0.95 2.40 3.311(6) 161 C(16)-H(16)···O(10) 0.95 2.51 3.381(7) 153 C(25)-H(25)···O(2) 0.95 2.34 3.259(6) 163 C(45)-H(45)···O(6) 0.95 2.36 3.277(6) 163 Cg(1)···Cg(J) dCg-Cg a (Å) α b (°) β , γ c (°) dplane-plane d (Å) doffset e (Å) Cg(1)···Cg(2) 3.761(3) 3.2(3) 13.9, 17.2 3.5939(18), 3.650(2) 0.907 Cg(3)···Cg(4) 3.717(3) 8.7(3) 14.1, 19.7 3.5001(19), 3.606(2) 0.904 a Centroid-centroid distance. b Dihedral angle between the ring planes. c Offset angles: angle between Cg(I)-Cg(J) vector and normal to plane I, angle between Cg(I)-Cg(J) vector and normal to plane J (β = γ , when α = 0). d Perpendicular distance of Cg(I) on plane J and perpendicular distance of Cg(J) on plane I (equal when α = 0). e Horizontal displacement or slippage between Cg(I) and Cg(J) (equal for both centroids when α = 0). 3: Cg(1) = N(3) C(23) C(24) C(25) C(26) C(27); Cg(2) = N(4) C(30) C(31) C(32) C(33) C(34); 4: Cg(1) = N(5) C(45) C(46) C(47) C(48) C(49); Cg(2) = N(12) C(60) C(61) C(62) C(63) C(64); Cg(3) = N(8) C(50) C(51) C(52) C(53) C(54); Cg(4) = N(9) C(55) C(56) C(57) C(58) C(59). 7 D. Ejarque, T. Calvet, M. Font-Bardia et al. Journal of Molecular Structure 1277 (2023) 134896 Fig. 3. (a, d and g) General and (b, e and h) In detail views of the supramolecular interactions of 2-4 along the (110) plane. (c, f and i). General view of the supramolecular interactions of 2-4 along the (011) (2 and 3) and (101) (4) planes. All the atoms not involved in the highlighted interactions have been omitted for clarity. of 2 (22.74°), allowing the stacking of their aromatic rings forming volving the carbonyl and carboxylate oxygen atoms from ACA with π ···π interactions (Figs. 2a-c). In addition, compounds 2-4 display hydrogen atoms from nearby N,N-donor linkers (Fig. 3b and 3e). the same C-H···O interaction between the alkene H-atom of the The presence of π ···π , C-H···π and N-H···π interactions extends μ2 -η1 :η1 ACA ligand and one of the oxygen atoms from a nearby the supramolecular scaffold along the [001] direction, forming the μ2 -η2 ACA. Otherwise, in compound 4, the torsion angles of the final 3D nets, presenting pcu topologies with different degrees of cinnamate skeletons of the μ2 -η1 :η1 ACA (8.47° and 12.27°) re- distortion, differently from the hxl topology of the 2D layers from vealed their higher planarity in comparison with 2 and 3 (22.40°, 1. (Table 5; Fig. 3c, 3f and 4). 2; 46.49°, 3), permitting the C-H···O interaction between the o-H In compound 4, the azo group of 4,4’-azpy promotes a change atom of this ACA and the oxygen atom from a μ2 -η2 ACA of the in its crystal packing compared with 2 and 3, allowing the same dimeric SBU (Table 4). introduction of one non-coordinated 4,4’-azpy and nine water molecules into the supramolecular network (Figs. 3 and 5). This 3.5. Extended structure of complexes 2-4 effect has been previously observed by Kitagawa et al. [50], and is attributed to the electronic repulsions between the lone pair elec- The supramolecular scaffold of 2 and 3 form 2D layers along trons of the carboxylate oxygen atoms and the azo groups. There- the (110) plane (Fig. 3a and 3d), which are mainly held together fore, the non-coordinated water molecules drive the supramolecu- by H-bonds involving the amide moieties from the μ2 -η2 ACA lig- lar assembly connecting the polymeric chains via H-bonding with ands, which joint together contiguous chains via amide-amide ho- the NH and C=O moieties from contiguous amide groups and the mosynthons. Moreover, there are additional C-H···O interactions in- carboxylate groups from ACA ligands of nearby chains, extending 8 D. Ejarque, T. Calvet, M. Font-Bardia et al. Journal of Molecular Structure 1277 (2023) 134896 Table 5 Selected intermolecular interactions (Å) for 2-4. 2 D-H···A D-H (Å) H···A (Å) D···A (Å) >D-H···A (°) N(1)-H(1)···O(6) 0.88 1.99 2.811(3) 155 C(24)-H(24)···O(2) 0.95 2.41 3.321(4) 161 C(26)-H(26)···O(3) 0.95 2.41 3.329(5) 162 C(29)-H(29)···O(2) 0.95 2.62 3.554(4) 167 C(32)-H(32)···O(3) 0.95 2.10 2.958(4) 149 X-H···Cg(J) H···Cg(J) (Å) H-Perpa (Å) γ (°)b X-H···Cg(J)c (°) X···Cg(J) (Å) X-H, Pid (°) C(22)-H(22C)···Cg(1) 2.69 2.67 7.71 159 3.623(4) 74 Cg(I)···Cg(J) dCg-Cg e (Å) α f (°) β , γ g (°) dplane-plane h (Å) doffset i (Å) Cg(2)···Cg(2) 3.861(2) 0 28.3, 28.3 3.3980(14) 1.833 3 D-H···A D-H (Å) H···A (Å) D···A (Å) >D-H···A (°) N(1)-H(1N)···O(6) 0.88 2.07 2.889(6) 154 C(28)-H(28)···O(1) 0.95 2.35 3.277(6) 165 C(29)-H(29)···O(3) 0.95 2.43 3.321(7) 156 C(31)-H(31)···O(1) 0.95 2.62 3.553(7) 167 C(34)-H(34)···O(3) 0.95 2.52 3.384(7) 151 X-H···Cg(J) H···Cg(J) (Å) H-Perpa (Å) γ (°)b X-H···Cg(J)c (°) X···Cg(J) (Å) X-H, Pid (°) N(2)-H(2N)···Cg(3) 2.72 2.61 16.71 163 3.573(5) 68 4 D-H···A D-H (Å) H···A (Å) D···A (Å) >D-H···A (°) O(1W)-H(1WA)···O(11) 0.96(7) 1.84(7) 2.792(5) 170(7) N(1)-H(1N)···O(5W) 0.88 1.99 2.823(6) 159 O(1W)-H(1WB)···O(9W) 0.99(5) 2.03(6) 2.856(5) 139(6) N(2)-H(2N)···O(2W) 0.88 1.98 2.785(6) 151 N(3)-H(3)···O(3) 0.88 2.12 2.856(6) 141 O(2W)-H(2WA)···O(9) 0.77(8) 1.96(8) 2.723(6) 171(8) O(2W)-H(2WB)···O(3W) 0.79(8) 2.05(8) 2.768(7) 150(7) N(4)-H(4N)···O(8W) 0.88 2.18 2.998(6) 154 O(3W)-H(3WA)···O(4W) 0.85(8) 1.87(8) 2.715(6) 175(10) O(3W)-H(3WB)···O(1W) 0.97(9) 1.81(8) 2.704(7) 152(6) O(4W)-H(4WA)···O(7W) 0.78(9) 2.43(8) 3.107(9) 147(7) O(4W)-H(4WB)···N(16) 0.88(7) 1.98(7) 2.776(6) 150(7) O(5W)-H(5WA)···O(12) 0.85(7) 1.88(7) 2.718(6) 171(7) O(5W)-H(5WB)···O(4W) 0.83(7) 2.02(7) 2.853(6) 177(8) O(6W)-H(6WB)···O(3W) 0.82(8) 1.97(7) 2.780(8) 170(13) O(7W)-H(7WA)···O(1) 0.83(7) 2.01(7) 2.831(7) 173(6) O(7W)-H(7WB)···O(6) 0.83(8) 2.32(7) 3.084(7) 153(7) O(8W)-H(8WA)···O(6) 0.91(8) 2.00(8) 2.903(6) 172(7) O(8W)-H(8WB)···O(9W) 0.88(7) 2.17(7) 3.042(6) 169(6) O(9W)-H(9WA)···O(8) 0.88(7) 1.86(8) 2.726(6) 167(6) O(9W)-H(9WB)···O(3) 0.84(7) 2.20(6) 2.954(5) 149(7) C(8)-H(8)···O(6) 0.95 2.52 3.331(7) 143 C(18)-H(18)···O(5W) 0.95 2.38 3.185(7) 142 C(33)-H(33A)···O(3) 0.98 2.43 3.228(8) 138 X-H···Cg(J) H···Cg(J) (Å) H-Perpa (Å) γ (°)b X-H···Cg(J)c (°) X···Cg(J) (Å) X-H, Pid (°) C(9)-H(9)···Cg(5) 2.74 2.70 9.53 152 3.606(7) 61 C(64)-H(64)···Cg(6) 2.71 2.64 13.36 152 3.574(7) 56 C(66)-H(66)···Cg(5) 2.63 2.62 4.61 150 3.483(8) 60 C(74)-H(74)···Cg(7) 2.92 2.77 18.49 134 3.645(8) 59 Cg(I)···Cg(J) dCg-Cg f (Å) α g (°) β , γ h (°) dplane-plane i (Å) doffset j (Å) Cg(1)···Cg(8) 3.848(3) 22.4(2) 8.5, 26.4 3.4444(19), 3.805(2) 0.569 Cg(4)···Cg(9) 3.935(4) 10.7(3) 18.9, 25.5 3.553(2), 3.724(3) 1.273 a Perpendicular distance of H to ring plane J.b Angle between Cg(J)-H vector and ring J normal.c X-H···Cg(J) angle.d Angle of the X-H bond with the Pi-plane (Perpendicular = 90°, Parallel = 0°).f Centroid-centroid distance.g Dihedral angle between the ring planes.h Offset angles: angle between Cg(I)-Cg(J) vector and normal to plane I, angle between Cg(I)-Cg(J) vector and normal to plane J (β = γ , when α = 0).i Perpendicular distance of Cg(I) on plane J and perpendicular distance of Cg(J) on plane I (equal when α = 0).j Horizontal displacement or slippage between Cg(I) and Cg(J) (equal for both centroids when α = 0). 2: Cg(1) = C(4) C(5) C(6) C(7) C(8) C(9); Cg(2) = C(15) C(16) C(17) C(18) C(19) C(20). 3: Cg(3) = C(4) C(5) C(6) C(7) C(8) C(9). 4: Cg(1) = N(5) C(45) C(46) C(47) C(48) C(49); Cg(4) = N(9) C(55) C(56) C(57) C(58) C(59); Cg(5) = C(15) C(16) C(17) C(18) C(19) C(20); Cg(6) = C(4) C(5) C(6) C(7) C(8) C(9); Cg(7) = C(26) C(27) C(28) C(29) C(30) C(31); Cg(8) = N(13) C(65) C(66) C(67) C(68) C(69); Cg(9) = N(16) C(70) C(71) C(72) C(73) C(74). the structure through the (110) plane (Fig. 3g). In addition, the wa- overlapped bands centered at 252 and 302 nm (1), 264 and 293 ter molecules form supramolecular patterns of H-bonds between nm (2), 276 and 329 nm (3), and 284 and 345 nm (4) (SI: Fig. them (Fig. 3h). The non-coordinated 4,4’-azpy molecules also con- S18). Moreover, compound 4 presents an additional absorption tribute to the formation of this plane through their π ···π stack- band centered at 470 nm. The comparison of these results with ing with the pillaring 4,4’-azpy linkers (Fig. 5c). Finally, additional the corresponding free ligands shows that the common peaks of C-H···O and C-H···π interactions extend the structure forming the 1-4 should be mainly attributed to a combination of absorptions final 3D network (Table 5, Fig. 3i). of the π -π ∗ transitions of the former ligands of each CP, where a higher contribution of the ACA ligand (λmax (HACA) = 246 nm, 294 nm) should be associated to the first band, and the second 3.6. Photophysical properties band might be more dependent of the N,N-donor linkers [51–54]. In addition, the band centered at 470 nm in 4 has been attributed The solid-state UV-Vis and fluorescence measurements of com- to the n-π ∗ transitions of the 4,4’-azpy ligand, mainly centered in plexes 1-4 have been recorded. Their absorption spectra show the azo chromophore [55]. 9 D. Ejarque, T. Calvet, M. Font-Bardia et al. Journal of Molecular Structure 1277 (2023) 134896 Fig. 4. Topological analysis of (a) compound 1 displaying a 2D layer with hxl topology. (b-d) Compounds 2-4 forming 3D networks with pcu topologies. Fig. 5. Disposition of the chains in: (a) 2, (b) 3, and (c) 4, showing the effect of the azo group in 4, which drives a different supramolecular packing compared with 2 and 3. All the atoms not involved in the highlighted interactions have been omitted for clarity. Fig. 6. Normalized solid-state emission spectra of compounds 1-4 excited at: (a) 262 nm showing emission peaks around 359, 422 and 491 nm. (b) 315 nm showing emission peaks around 360, 376 and 392 nm. The dashed line of capture (b) corresponds to the emission of 4 when excited at 470 nm, showing an emission peak at 484 nm. When all the compounds were irradiated at their first absorp- radiation (Fig. 6b). Finally, when compound 4 was irradiated at tion band (λexc = 262 nm), all of them display the same pat- 470 nm, the emission of the azo chromophore has been observed, tern of unstructured emission signals with different maxima in displaying a peak at 484 nm (Fig. 6b). Considering these exci- the range of 320-500 nm, and moderate Stokes shift between tations, the resulting emission colors according to the CIE 1931 10235 and 17884 cm−1 (Fig. 6a). Relevant emission maxima and chromaticity diagrams when irradiated at 262 nm are blue rib- Stokes shifts are listed in the SI (Table S2). Besides, the irradia- bon (1-3) and azure radiance (4), while when λexc = 315 nm tion of the complexes at their second absorption band (λexc = 315 the observed color was electric violet (1-4), and the excitation nm) show the emission of similar unstructured bands but with of the azo chromophore of 4 at 470 nm results in a cyan color a lower range, probably due to the use of a less energetic ir- (SI: Fig. S19). 10 D. Ejarque, T. Calvet, M. Font-Bardia et al. Journal of Molecular Structure 1277 (2023) 134896 4. Conclusions [5] S.-D. Han, J.-X. Hu, G.-M. Wang, Recent advances in crystalline hybrid pho- tochromic materials driven by electron transfer, Coord. Chem. Rev. 452 (2022) 214304, doi:10.1016/j.ccr.2021.214304. We have successfully synthesized four Cd(II) CPs, whose struc- [6] Q. Yue, E.-Q. Gao, Azide and carboxylate as simultaneous coupler for magnetic tural elucidation revealed the formation of 1D ladder-type ar- coordination polymers, Coord. Chem. 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