This is an open access article published under an ACS AuthorChoice License, which permits copying and redistribution of the article or any adaptations for non-commercial purposes. http://pubs.acs.org/journal/acsodf Article Influence of Aromatic Cations on the Structural Arrangement of Hg(II) Halides Francisco Sań chez-Feŕ ez, Xavier Solans-Monfort, Teresa Calvet, Merce ̀ Font-Bardia, and Josefina Pons* Cite This: ACS Omega 2020, 5, 29357−29372 Read Online ACCESS Metrics & More Article Recommendations * sı Supporting Information ABSTRACT: Understanding the structure and arrangement of hybrid metal halides and their contribution to the optoelectronic properties is, thus far, a challenging topic. In particular, new materials composed of d10 metal halides and pyridinium cations are still largely unexplored. Therefore, we report the synthesis and characterization of six Hg(II) salts built up from (Hg2Cl6)2− or (HgX4)2− anions (X = Cl, Br, I) and 2,2′-bipyridium (2,2′- Hbipy)+, 2,2′-bipyridine-1,1′-diium (2,2′-H2bipy)2+, or 1,10- phenantrolinium (1,10-Hphen)+ cations, using the same exper- imental conditions. All of them have been characterized by PXRD, EA, FTIR-ATR, and 1H NMR spectroscopies; single-crystal X-ray diffraction; and TG/DTA determinations. The study of their packing via Hirshfeld surface analysis and 3D deformation density mapping revealed the contributions of the intermolecular interactions to the structural arrangement, notably, the effect of the cation planarity on them. Successively, periodic DFT calculations showed that (i) the valence and conducting bands are mainly composed of the p orbitals of the halide and the organic cation, respectively, and (ii) the corresponding band gap depends mainly on the halide. ■ INTRODUCTION The study of hybrid organic−inorganic materials composed of and Hg(II)16−21 being prospective homovalent candidates. In previous papers, Hg(II) halides containing alkylammonium metal halide anions and ammonium-based organic cations has cations inter alia, (C3H12N2)(HgC14)22 and (C4H14N2)- suffered a rekindled interest flagged by their application in (HgCl4),23 presented corner-sharing HgCl6 octahedra with optoelectronic devices. Their solvent processability and easy (HgCl4)2− units forming layers separated by the bifunctional fabrication in combination with their structural tunability ammonium cations. The larger aliphatic chain of (C4H14N2)2+ distinguished them as promising materials.1,2 favored van der Waals interactions, better stacking the cations As their structural arrangement directly affects the electronic and favoring the shorter separation of the inorganic layers. properties, thoroughgoing studies on the effects of anion and Their substitution by benzidinium cations in cation into the final packing and their influence on the band (NH3(C6H4)2NH3)(HgCl4)24 modified the inorganic con- gap are required. Indeed, the structural features of the cation nectivity, constructing tetrahedral HgCl4 units but preserving (size, planarity, and aromaticity) conjointly with those of the the layered structure. In this case study, the aromatic anion (size, geometrical metal preferences, and halide benzidinium cations did not form π···π stacking interactions, dimensions)3 are known to drive the assembly of the inorganic which favored the separation of the inorganic units. units through their intermolecular interactions (electrostatic, In addition, their spherical d10 closed-shell electronic π···π stacking, anion···π, and σ-hole effects).4−9 configuration stands out for promoting the electronic Notwithstanding the extensive research done with primary transitions to occur through ligand-centered (LC) and amines and in a lesser extent with aromatic rings,10 the studies ligand-to-ligand charge transfer (LLCT) and hence excels at incorporating pyridinium cations are scarce.2,11 Howbeit, presenting photophysical properties.25 In this sense, to the best aromatic cations were proven to be remarkable candidates of our knowledge, there is no previously reported study on the for preparing light-emitting compounds. 12 While alkyl ammonium cations tend to form layered arrays,13,14 even more pronounced with large cations,15 their replacement with Received: August 28, 2020 bipyridinium rings with a delocalized π-electron character may, Accepted: October 16, 2020 at the same time, modify the packing and the electronic Published: November 6, 2020 properties. Within this frame, there has been extensive research on Sn(II), Pb(II), and Ge(II) halides but less on Zn(II), Cd(II), © 2020 American Chemical Society https://dx.doi.org/10.1021/acsomega.0c04175 29357 ACS Omega 2020, 5, 29357−29372 ACS Omega http://pubs.acs.org/journal/acsodf Article optoelectronic properties of Hg(II) halides incorporating in the spectrum of compound 6 in which the N−H+ group is pyridinium cations. not hydrogen bonded to the (HgI4)2− anion and thus, the Our group has previously explored the structural behavior of υ(N−H+) peak is shifted to higher values. In addition, the d10 metal ions in the presence of either carboxylic aromatic formation of C−H···X interactions provoked a redshift on the ligands or combined with N-donor aromatic ligands, relating it υar(C−H) modes of the cations. Since the strength of these with their photophysical properties.26−28 In this contribution, associations depend on the electronegativity of the acceptor,31 we focused on Hg(II) halides in the presence of N-donor the shift is in line with the order Cl > Br > I, ranging from 3094 aromatic conjugated cations being 2,2′-bipyridium (2,2′- to 3022 cm−1. The bands attributable to υ(CC/CN) and Hbipy)+, 2,2′-bipyridine-1,1′-diium (2,2′-H2bipy)2+, and 1,10- δ(N−H+) appeared in the region between 1635 and 1443 phenantrolinium (1,10-Hphen)+, bearing on their different cm−1, while δ(CC/CN) ring modes32 appeared between planarity and bulkiness. Herein, the synthesis of six hybrid 1428 and 1370 cm−1. The aromatic C−H vibrational modes of Hg(II) halides, (2,2′-Hbipy)2(Hg2Cl6) (1), (2,2′-H2bipy)- the cations are also identified between 1185 and 1165 cm−1 (HgX4) (X = Br (2), I (3)), and (1,10-Hphen)2(HgX4) (X [δ(C−H)ip] or between 844 and 714 cm−1 [δ(C−H)oop]33 = Cl (4), Br (5), and I (6)), is reported, and their single-crystal (Supporting Information, Figures S3−S8). An additional band X-ray structures are determined. The study of their arrange- from the γ(N−H)+ out-of-plane mode30 is identified from 960 ments conjointly with periodic DFT calculations has enabled to 917 cm−1. us to obtain more insight on the effect of these relatively The 1H NMR spectra of 1−6 have been recorded in DMSO- unexplored cations with their corresponding halogen atom on d6 solution. They show four signals between 8.90 and 7.81 the final packing and optoelectronic properties. ppm (1−3) or between 9.32 and 8.18 ppm (4−6) assigned to ■ RESULTS AND DISCUSSION Synthesis and General Characterization. All the the aromatic protons of the cations, which are shifted with respect to the free 2,2′-bipy and 1,10-phen molecules (8.68− 7.44 ppm and 9.10−7.76 ppm, respectively), indicating a reactions have been carried out by mixing HgX2 (X = Cl, Br, change of the electronic distribution caused by the protonation I) with 2,2′-bipyridine (2,2′-bipy) or 1,10-phenantroline (1,10- of the corresponding N-donor atoms. The N−H+ protons phen) in a 1:2 molar ratio and acidified media with the appear from 5.32−4.73 ppm in 1−3 and between 4.10−4.39 corresponding acid (HCl, HBr, and HI) in a CH2Cl2/MeOH ppm in 4−6.34 Further NMR details are provided in the solvent mixture at room temperature (r.t.). The CH2Cl2/ Experimental Section (Supporting Information, Figures S9− MeOH solvent mixtures were 2:1 (1, 2, 4, 5) or 1:1 (3, 6), S14). relying on the low solubility of HgI2 in CH2Cl2 (Scheme 1). Finally, the TG/DTA determination of the samples enabled to analyze their thermal stability showing that they are stable Scheme 1. Outline of the Synthesis of Compounds 1−6 until at least 220 °C (Supporting Information, Figure S15). Crystal and Extended Structure of (2,2′-Hbi- py)2(Hg2Cl6) (1). Compound 1 is composed of a dimeric (Hg2Cl6)2− anion and two (2,2′-Hbipy)+ cations in cis conformation. The (Hg2Cl6)2− unit is formed around two Hg(II) centers at 3.8978 (4) Å (slightly longer than other reported Hg···Hg distances, 3.7523 (3)−3.884 (4) Å), displaying a distorted tetrahedral geometry (τ4(Hg (1)) = 0.80; τ4(Hg (2)) = 0.72)35 and being connected through two asymmetrically bridging Cl and four terminal Cl atoms (Figure 1a). All the Hg−Cl bond lengths fall within the range 2.3745 (9)−2.8758 (8) Å (Table 1), which are in accord with reported (Hg2Cl6)2− containing compounds (2.370 (2)−2.881 (2) Å).36−39 The formation of 2,2′-bipyridium (2,2′-Hbipy)+, 2,2′- These dimeric units are held together in a linear fashion bipyridine-1,1′-diium (2,2′-H2bipy)2+, or 1,10-phenantroli- through the a axis by interdimeric interactions between the nium (1,10-Hphen)+ cationic species resulted in compounds Hg(II) centers and the terminal Cl (Hg (2)···Cl (1), 3.1429 (2,2′-Hbipy)2(Hg2Cl6) (1), (2,2′-H2bipy)(HgX4) (X = Br (2) (7) Å and Hg (1)···Cl (5), 3.3911 (8) Å) (being 3.30 Å the and I(3)), and (1,10-Hphen)2(HgX4) (X = Cl (4), Br (5), and sum of the van der Waals radii of both atoms). The 2,2′-Hbipy I (6)). All these compounds have been characterized by cations are disposed around these chains, being N−H oriented PXRD, EA, FTIR-ATR, and 1H NMR spectroscopies; single- to the remaining terminal Cl via hydrogen bond interactions. crystal X-ray diffraction; and TG/DTA determination. It At both sides and parallel to the (Hg2Cl6)2− chain, the 2,2′- should be mentioned that even if the crystal structure of 2 was Hbipy cations are stacked through π···π interactions (Figure previously reported by Ali and Al-Far,29 it was determined at 1b) in an alternate manner (double-single and so forth): 297 K rather than at 100 K, which leads to slight changes in the double (pyridyl−pyridyl and pyridinium−pyridinium) and unit cell and intermolecular interactions. In addition, the single (pyridyl−pyridyl) (Table 1). These 2,2′-Hbipy cations synthesis was performed using a different synthetic method. associate the chains forming a 3D net. Phase purity of the bulk samples was confirmed by PXRD Crystal and Extended Structure of (2,2′-H2bipy)- (Supporting Information, Figure S1). In the FTIR-ATR (HgBr4) (2). Compound 2 was previously reported29 by Ali spectra of 1−6, the υ(N−H+) appeared as a broad band and Al-Far,29 but we extended the structural study considering between 3448 and 2712 cm−1 and probably shifted to a minor further interactions relevant for this paper. It is composed of wavenumber due to the strong ionic interaction between the one monomeric (HgBr4)2− anion and two (2,2′-H2bipy)2+ proton and the corresponding halogen atom.30 This is reflected cations (Figure 2a), in which the Hg(II) center displays a 29358 https://dx.doi.org/10.1021/acsomega.0c04175 ACS Omega 2020, 5, 29357−29372 ACS Omega http://pubs.acs.org/journal/acsodf Article Figure 1. (a) Molecular structure of (2,2’-Hbipy)2(Hg2Cl6) (1) highlighting the ionic interactions between the 2,2’-Hbipy cations and the chlorine atoms. (b) 1D expansions of the dimeric units through Hg···Cl and π···π interactions. slightly distorted tetrahedral geometry (τ4(Hg (1)) = 0.86).35 Crystal and Extended Structure of (1,10- These anions are joined through ionic interactions into 1D Hphen)2(HgX4) (X = Cl (4), Br (5), or I (6)). Compounds chains along the a axis via bridging trans(2,2′-H2bipy)2+ 4−6 are composed of (HgX4)2− (X = Cl (4), Br (5), or I (6)) (Figure 2b). It should be noted that there is an interaction anions and 1,10-Hphen cations mainly associated through N− between the Br (3) atom and the subsequent Hg(II) center of H···X, N−H···O, and C−H···X interactions (Figure 4). In the a contiguous monomeric unit at 3.5785 (5) Å (longer than the three compounds, the monomeric Hg(II) centers display a sum of their van der Waals radii: 3.40 Å). slightly distorted tetrahedral geometry (4: τ4(Hg (1)) = 0.92; Even though it could not be considered a coordination 5: τ4(Hg (1)) = 0.91; 6: τ4(Hg (1)) = 0.95).35 The Hg−X bond, it is a non-negligible interaction since it directs the bond lengths are within the range of reported (HgX4)2− (HgBr4)2− stacking through the c axis and lengthens the Hg anions12,36−42 (Table 4). (1)−Br (3) bond (2.7985 (5) Å) compared to the rest (2.5491 In 4, each Hg(II) node interacts with two (1,10-Hphen)+ (4)−2.6299 (4) Å). All the Hg−Br bond lengths are similar to cations either directly N (2)−H(2N)···Cl (2) (2.4169 Å) or the previously reported structure29 and within the range of through a water molecule N (4)−H(4N)···O (1.855 Å) and other reported compounds with (HgBr4)2− anions and O(1 W)−H(1WB)···Cl (4) (2.375 (2) Å) (Table 5). This pyridinium cations12 (2.6328 (4)−2.6900 (5) Å) (Table 2). double association alters the intermolecular interactions, In this case, the 2,2′-H2bipy rings are too far to assemble by forming zigzag 1D chains along the c axis (Figure 5a). π···π interactions (4.774 Å) (Figure 2b). In two previously reported closely related case studies, the Finally, the 2,2′-H2bipy cations interact both supporting the mono- or diprotonated 1,10-phenantrolines in stacking of the inorganic units via C−H···Br interactions (C (phenH)2[ZnCl4]·H2O or (phenH2)2Pb3I10·2H2O also interact through water molecules rather than directly with the (4)−H (4)···Br (3), 2.9257 Å; C (7)− H (7)···Br (1), 2.8372 corresponding halogen atoms.2,43 There are precedents Å; C (1)−H (1)···Br (4), 2.7677 Å; and C (12)−H (12)···Br demonstrating the strength of the Cl···H2O interaction.44 In (4), 2.8960 Å) and joining the chains through N−H···Br ionic addition, (HgCl4)2− anions are surrounded by six (1,10- associations (N (1)−H (1N)···Br (3), 2.3852 Å and N (2)−H Hphen)+ cations stacked in pairs by reciprocal π···π (2N)···Br (2), 2.4593 Å), which form a 2D layer along the ac interactions (Figure 5b) and associated with the anion via plane (Figure 2c) (Table 2). combination of C−H···Cl and N−H···Cl. In addition, these Crystal and Extended Structure of (2,2′-H2bipy)(HgI4) cations are weakly interacting with neighboring anions by (3). Compound 3 is composed of a monomeric (HgI4)2− anion Cl···π4,5 (Figure 5c) ,which form a 3D net. and two (2,2′-H2bipy)2+ cations. The Hg(II) center has a In 5, two (1,10-Hphen)+ cations associate with a (HgBr4)2− tetrahedral geometry (τ4(Hg (1)) = 0.94)35 (Figure 3a) (Table anion through double N−H···Br and C−H···Br interactions 3). These anions are discrete units without any significant within the range of similar compounds12 (Table 6). In interactions between them and surrounded by (2,2′-H2bipy)2+ addition, these anions are surrounded by (1,10-Hphen)+ cations through N−H···I ionic associations (N (1)−H (1N)···I cations disposed in five pairs stacked by double (Figure 6a) (2), 2.6524 Å and N (2)−H (2N)···I (1), 2.5764 Å) and weak or triple (Figure 6b) π···π interactions and a weak Br···π C−H···I interactions, which form linear zigzag chains along the contact4,5 (Figure 6c). These planar associations hold together b axis (Figure 3b) (Table 3). The Hg−I bond lengths (2.7398 the (1,10-Hphen)2(HgBr4) assemblies, forming a 3D net. (5)−2.8398 (5) Å) are within the range of reported (HgI4)2− In 6, the structural disorder limits the analysis of the anions (2.7430 (8)−2.844 (1) Å).40−42 intermolecular interactions; however, N atoms are too far from Only weak reciprocal C−H···I contacts join the chains along the I and thus, there is not any N−H···I interaction. Instead, the c axis (C (8)−H (8)···I (4), 3.1363 Å and H (8)−C (8)···I the (HgI4)2− anions associate through C−H···I interactions (4), 3.895 (7) Å; 138.10°), defining 2D layers through the bc with eight (1,10-Hphen)+ cations (Figure 7a), which are plane and as in the case of 2, (2,2′-H2bipy)2+ cations are too stacked in chains by reciprocals pyridinium-phenyl π···π far to be stacked trough π···π interactions (4.360 Å). interactions (Table 7) along the a axis in a piled disposition 29359 https://dx.doi.org/10.1021/acsomega.0c04175 ACS Omega 2020, 5, 29357−29372 ACS Omega http://pubs.acs.org/journal/acsodf Article Table 1. Selected Bond Lengths, Angles, and Intermolecular Interactions of (2,2′-Hbipy)2(Hg2Cl6) (1)a bond lengths (Å) Hg (1)−Cl (1) 2.4082 (8) Hg (2)−Cl (6) 2.4092 (8) Hg (1)−Cl (2) 2.4116 (7) Hg (2)−Cl (4) 2.5527 (7) Hg (1)−Cl (3) 2.5179 (8) Hg (2)−Cl (3) 2.8757 (7) Hg (1)−Cl (4) 2.7273 (7) Hg (1)···Hg (2) 3.8978 (4) Hg (2)−Cl (5) 2.3745 (8) bond angles (°) Cl (2)−Hg (1)− 127.81 (3) Cl (5)−Hg (2)−Cl 121.97 Cl (1) (4) (3) Cl (2)−Hg (1)− 108.80 (3) Cl (6)−Hg (2)−Cl 100.03 Cl (3) (4) (3) Cl (1)−Hg (1)− 120.05 (3) Cl (5)−Hg (2)−Cl 91.61 (3) Cl (3) (3) Cl (2)−Hg (1)− 103.99 (3) Cl (6)−Hg (2)−Cl 103.18 Figure 2. (a) Molecular structure of (2,2′-H2bipy)(HgBr4) (2) Cl (4) (3) (2) highlighting the ionic interactions between the 2,2′-H2bipy cations Cl (1)−Hg (1)− 95.24 (2) Cl (4)−Hg (2)−Cl 84.26 (2) and the bromine atoms. (b) Linear Br···Hg associations and (c) Cl (4) (3) intermolecular interactions between (2,2′-H2Bipy)2+ and Br atoms. Cl (3)−Hg (1)− 88.08 (2) Hg (1)−Cl (3)−Hg 92.31 (2) Cl (4) (2) Cl (5)−Hg (2)− 136.77 (3) Hg (2)−Cl (4)−Hg 95.10 (2) Table 2. Selected Bond Lengths, Angles, and Intermolecular Cl (6) (1) Interactions of (2,2′-H2bipy)(HgBr4) (2) intermolecular interactions bond lengths (Å) interaction H···A (Å) D···A (Å) D−H >D−H···A (Å) (°) Hg (1)−Br (1) 2.4082 (8) Hg (1)−Br (4) 2.7273 (7) N (2)−H 2.4434 3.250 (3) 0.880 152.68 Hg (1)−Br (2) 2.4116 (7) Hg (1)···Br (3) 3.5785 (5) (2N)···Cl (2) Hg (1)−Br (3) 2.5179 (8) N (3)−H 2.4437 3.178 (3) 0.880 141.30 bond angles (°) (3N)···Cl (6) Br (4)−Hg (1)−Br 122.503 Br (4)−Hg (1)−Br 102.176 (10) C (1)−H (1)··· 2.8228 3.674 (3) 0.950 149.63 (1) (11) (3) Cl (4) Br (4)−Hg (1)−Br 114.042 Br (1)−Hg (1)−Br 101.330 (11) C (3)−H (3)··· 2.9393 3.669 (3) 0.949 134.60 (2) (11) (3) Cl (6) Br (1)−Hg (1)−Br 116.734 Br (2)−Hg (1)−Br 91.901 (10) C (7)−H (7)··· 2.5997 3.435 (3) 0.951 146.88 (2) (13) (3) Cl (3) intermolecular interactions C (9)−H (9)··· 2.8970 3.605 (5) 0.950 132.27 Cl (3) interaction H···A (Å) D···A D−H >D−H···A (Å) (Å) (°) C (10)−H 2.8786 3.620 (4) 0.951 135.68 (10)···Cl (5) N (1)−H (1N)···Br 2.3852 3.202 (3) 0.880 154.53 (3) C (11)−H 2.8979 3.612 (3) 0.950 132.83 (11)···Cl (5) N (2)−H (2N)···Br 2.4593 3.276 (3) 0.880 154.60 (2) C (12)−H 2.8724 3.476 (3) 0.950 122.48 (12)···Cl (2) C (1)−H (1)···Br (4) 2.7677 3.673 (4) 0.950 159.61 C (13)−H 2.9238 3.509 (3) 0.950 121.01 C (2)−H (2)···Br (1) 2.9689 3.800 (4) 0.951 146.85 (13)···Cl (2) C (4)−H (4)···Br (3) 2.9257 3.830 (3) 0.950 159.50 C (14)−H 2.9350 3.881 (3) 0.950 174.41 C (7)−H (7)···Br (1) 2.8372 3.751 (4) 0.950 132.27 (14)···Cl (1) C (8)−H (8)···Br (3) 2.9803 3.653 (3) 0.949 128.98 π···π interactions C (11)−H (11)···Br 2.9828 3.834 (4) 0.950 149.89 Cg (1)···Cg (3) 3.739 Å 69.71° Cg (2)··· 3.635 Å 71.68° (2) Cg (4) C (12)−H (12)···Br 2.8960 3.789 (4) 0.950 157.08 Cg (1)′···Cg (3) 3.653 Å 67.98° (4) a Cg (1) = Cg (1)′: N1−C1−C2−C3−C4−C5; Cg (2): N2−C6− C7−C8−C9−C10; Cg (3): N4−C16−C17−C18−C19−C20; Cg (4): N3−C11−C12−C13−C14−C15. hydrogen bonds (WHB).9 Despite being considered secondary interactions, the formation of the cations is deemed (Figure 7b). These chains are held together by the anions responsible to increase the hydrogen donor propensity of the forming a 3D net. aromatic C−H groups, thus promoting the formation of C− Packing Analysis of 1−6. General Considerations. Some H···X (X = Cl, Br, or I) interactions. Likewise, it facilitated the remarks should be examined to better comprehend these formation of X···π interactions instead of C−H···π associations. structural arrangements. We will emphasize the role of the All of them arise as determining factors in the structural halogen atoms (regarding their electronegativities, radii, and analysis. polarizabilities) and the organic units (planarity, mono- or The essential interactions will be divided into three groups: diprotonation, and thus, their different electronic density N−H/C−H···X, X···Hg(II), and planar π···π interactions. For distributions). Noteworthy is the increased role of weak the sake of analyzing them, Hirshfeld surfaces with their 2D 29360 https://dx.doi.org/10.1021/acsomega.0c04175 ACS Omega 2020, 5, 29357−29372 ACS Omega http://pubs.acs.org/journal/acsodf Article Table 4. Selected Bond Lengths and Angles of (1,10- Hphen)2(HgCl4)·H2O (4), (1,10-Hphen)(HgBr4) (5), and (1,10-Hphen)(HgI4) (6)a 4 bond lengths (Å) Hg (1)−Cl (1) 2.4412 (5) Hg (1)−Cl (3) 2.4803 (4) Hg (1)−Cl (2) 2.5452 (5) Hg (1)−Cl (4) 2.4952 (5) bond angles (°) Cl (1)−Hg (1)− 115.258 (15) Cl (1)−Hg (1)−Cl 107.685 (16) Cl (3) (2) Cl (1)−Hg (1)− 115.283 (18) Cl (3)−Hg (1)−Cl 102.096 (15) Cl (4) (2) Cl (3)−Hg (1)− 108.624 (16) Cl (4)−Hg (1)−Cl 106.723 (18) Cl (4) (2) 5 bond lengths (Å) Hg (1)−Br (1) 2.5594 (10) Hg (1)−Br (3) 2.4512 (11) Hg (1)−Br (2) 2.4486 (11) Hg (1)−Br (4) 2.5221 (11) Figure 3. (a) Molecular structure of (2,2′-H2bipy)(HgI4) (3) bond angles (°) highlighting the ionic interactions between the 2,2′-H2bipy cations Br (2)−Hg (1)− 120.59 (4) Br (2)−Hg (1)−Br 108.55 (4) and the iodine atoms and (b) 1D zigzag association through the b Br (3) (1) axis. Br (2)−Hg (1)− 110.75 (4) Br (3)−Hg (1)−Br 104.78 (4) Br (4) (1) Table 3. Selected Bond Lengths, Angles and Intermolecular Br (3)−Hg (1)− 108.41(4) Br (4)−Hg (1)−Br 102.02 (4) Interactions of (2,2′-H2bipy)(HgI4) (3) Br (4) (1) 6 bond lengths (Å) bond lengths (Å) Hg (1)−I (1)#1 2.7760 (9) Hg (1)−I (2)#1 2.7737 (9) Hg (1)−I (1) 2.8032(4) Hg (1)−I (3) 2.7756 (5) bond angles (°) Hg (1)−I (2) 2.8398(5) Hg (1)−I (4) 2.7483 (4) I (2)−Hg (1)−I 113.27 (4) I (2)#1−Hg (1)−I 105.36 (2) bond angles (°) (2)#1 (1)#1 I (4)−Hg (1)−I (3) 116.276 I (4)−Hg (1)−I (2) 111.799 (14) I (2)−Hg (1)−I 109.83 (2) I (1)#1−Hg (1)−I 113.36 (4) (14) (1)#1 (1) I (4)−Hg (1)−I (1) 108.793 I (3)−Hg (1)−I (2) 100.591 (14) a #1 −x + 2,y,−z. (14) I (3)−Hg (1)−I (1) 111.401 I (1)−Hg (1)−I (2) 107.493 (13) (14) isosurfaces of 1−5 are drawn at 0.008 eau−3, and their wave intermolecular interactions functions were calculated by the density functional theory interaction H···A (Å) D···A (Å) D−H (Å) >D−H···A (DFT) at the 6-311++G(2d,2p) level with Becke 88 gradient- (°) corrected exchange and LYP correlation energy functional46 N (1)−H (1N)···I 2.6524 3.486 (5) 0.880 158.38 using TONTO. Unfortunately, the structural disorder of (2) compound 6 has excluded it from this calculation. N (2)−H (2N)···I 2.5764 3.434 (5) 0.880 165.99 (1) The DD mapping allows the representation of electronic C (4)−H (4)···I (2) 3.1783 4.022 (6) 0.950 149.05 density distribution along the molecule after suffering the C (7)−H (7)···I (3) 3.1264 3.977 (6) 0.950 149.87 polarization because of the interactions in which it participates. C (8)−H (8)···I (4) 3.1363 3.895 (7) 0.950 138.10 Low electron density areas termed charge depletion (CD) C (9)−H (9)···I (2) 3.1407 3.976 (6) 0.950 147.66 regions can attractively interact with charge concentration (CC) areas which are more electron rich. In this sense, univalent halogen atoms can be polarized upon coordination fingerprint plots and 3D deformation density (DD) maps have and generate a CD region named σ-hole6,7 on the extension of been generated using CrystalExplorer 17.5.45 The DD the bond and thus more electron-rich regions at the sides. Figure 4. Molecular structure of (1,10-Hphen)2(HgX4) (X = (a) Cl (4), (b) Br (5), or (c) I (6)) highlighting the closer interactions between the 1,10-Hphen cations and the halogen atoms. 29361 https://dx.doi.org/10.1021/acsomega.0c04175 ACS Omega 2020, 5, 29357−29372 ACS Omega http://pubs.acs.org/journal/acsodf Article Table 5. Intermolecular Interactions of (1,10- The percentages of the surface area implied in these Hphen)2(HgCl4)·H2O (4)a interactions are 31.5 and 28.8 (1), 42.6 (2), and 50.1 (3), being the greatest values compared to the rest (Table 8). The >D-H···A interaction H···A (Å) D···A (Å) D-H (Å) (°) size of the halogen atoms and proximity to the cations are the N (2)−H(2N)···Cl 2.4169 3.200 (2) 0.880 148.44 main contributors; hence, even if 3 has a bigger percentage, the (2) position of the peaks in the 2D fingerprint plots reflects the N (4)−H(4N)···O (1 1.855 2.683 (2) 0.880 155.87 larger distances and thus weaker interactions between the inner W) hydrogens of the surface and the closest outer I atom. O (1W)−H (1WB)··· 2.375 (2) 3.171 (1) 0.803 (2) 171.16 The DD mapping of (2,2′-Hbipy)+ (1) and (2,2′-H2bipy)2+ Cl (4) (2 and 3) displays large CD regions extended throughout the C (2)−H (2)···Cl (1) 2.7057 3.576 (2) 0.950 152.60 rings promoted by their protonation and the interactions with C (3)−H (3)···Cl (3) 2.7647 3.661 (2) 0.950 157.57 the surrounding atoms (Figure 9). Within this frame, the C (13)−H (13)···Cl 2.8201 3.461 (2) 0.950 125.62 (4) tendency of halogen atoms of being oriented through a side, C (14)−H (14)···Cl 2.9070 3.647 (2) 0.950 135.66 perpendicular to the extension of the bond when they interact (2) with CD regions, or through the extension of the bond when C (18)−H (18)···Cl 2.7230 3.669 (2) 0.950 173.71 they associate to CC regions, suggests the presence of σ-hole (1) interactions. It is worth mentioning a haptic-like interaction2 C (21)−H (21)···Cl 2.9302 3.727 (2) 0.950 142.24 (4) between the face of the (HgI4)2− tetrahedra and the pyridyl π···π interactions ring of the (2,2′H2bipy)2+ cation (Figure 9c), which could Cg (1)···Cg (2) 3.685 Å 68.06° facilitate charge transfers (CTs) between them. Cg (3)···Cg (4) 3.593 Å 77.33° For what concerns the X···Hg(II) interactions, they have a Cg (1): C4−C5−C6−C7−C11−C12; Cg (2): N1−C1−C2−C3− modified the nuclearity and association of inorganic anions C4−C12; Cg (3): N4−C17−C18−C19−C20−C21; Cg (4): C16− between themselves, forming strong linear associated dimeric C17−C20−C22−C23−C24. arrays (1), weak linear associated monomers (2), or discrete monomers assembled by cations in a zigzag fashion (3). Their 2D fingerprint displays small sharp peaks that decrease until disappearance from Cl to I, and the surface percentage Structures Containing (2,2′-Hbipy)+ or (2,2′-H2bipy)2+ between the halogen atoms and the Hg(II) centers being 3.8 (1−3). The N−H···X contacts hold together these arrays being (1), 1.8 (2), and 0.2 (3) thereby confirms the aforementioned the strongest interactions, subsequently supported by C−H···X tendency. Likewise, the distortion of the (HgX4)2− (X = Cl, Br, associations. Their Hirshfeld surfaces outline these contacts, or I) geometry is directly correlated to the strength of the and the shorter N−H···X interactions are represented as sharp interactions between the inorganic units in the order Cl > Br > peaks in the 2D fingerprint plots (Figure 8). I (Figure 8). Figure 5. Intermolecular interactions of (1,10-Hphen)2(HgCl4)·H2O (4). (a) Zigzag chains formed through N−H···Cl and N−H···O/O−H···Cl interactions. (b) Six (1,10-Hphen)+ cations around (HgCl4)2−. Hydrogen atoms that do not interact with the anion are omitted for clarity. (c) Cl···π interactions. Dashed black lines pinpoint the distance of Cl to the plane containing the aromatic rings. 29362 https://dx.doi.org/10.1021/acsomega.0c04175 ACS Omega 2020, 5, 29357−29372 ACS Omega http://pubs.acs.org/journal/acsodf Article Table 6. Intermolecular Interactions of (1,10-Hphen)2(HgBr4) (5)a interaction H···A (Å) D···A (Å) D−H (Å) >D−H···A (°) N (1)−H(1N)···Br (1) 2.412 3.15 (1) 0.88 141.18 N (3)−H(3N)···Br (4) 2.409 3.12 (1) 0.88 138.19 C (1)−H (1)···Br (3) 2.753 3.61 (2) 0.95 150.05 C (1)−H (1)···Br (1) 2.935 3.41 (1) 0.95 112.08 C (2)−H (2)···Br (4) 2.982 3.71 (1) 0.95 133.91 C (3)−H (3)···Br (1) 2.728 3.64 (1) 0.95 160.67 C (6)−H (6)···Br (2) 2.863 3.78 (2) 0.95 163.42 C (13)−H (13)···Br (4) 2.841 3.35 (2) 0.95 114.35 C (13)−H (13)···Br (1) 2.647 3.52 (1) 0.95 153.50 C (14)−H (14)···Br (2) 2.747 3.57 (1) 0.95 146.05 C (15)−H (15)···Br (4) 2.539 3.47 (2) 0.95 165.58 C (18)−H (18)···Br (3) 2.826 3.74 (2) 0.95 163.58 π···π interactions Cg (1)···Cg (3) 3.621 Å 66.63° Cg (2)···Cg (2) 3.613 Å 78.51° Cg (3)···Cg (1)′ 3.633 Å 65.28° a Cg (1) = Cg (1)′: N3−C13−C14−C15−C16−C24; Cg (2): C16−C17−C18−C19−C23−C24; Cg (3): N4−C19−C20−C21−C22−C23. Figure 6. Intermolecular interaction of (1,10-Hphen)2(HgBr4) (5). Hydrogen atoms not involved in the interactions are omitted for clarity. Highlighting of (b) double or (b) triple π···π stacking. (c) Br···π contact. Dashed black lines pinpoint the distance of Br to the plane containing the aromatic rings. Figure 7. (a) Intermolecular interaction of (1,10-Hphen)2(HgI4) (6). (b) View of the piled packing of the anions or cations. The smaller radius of Cl (1.75 Å) compared to Br (1.85 Å) linear disposition of the monomeric units. On the contrary, the and I (1.98 Å), in combination with its higher electro- bigger radius and lower electronegativity of I weaken this negativity, allowed the formation of dimeric units linearly association and facilitate the distortion of the linear assembled through semi-coordination bonds. In the case of Br, disposition. The intra-chain Hg(II)···Hg(II) distance increases which is midway in size, there is a clear directional Hg(II)···Br in the order 1 > 2 > 3 being 4.3595 (4) Å, 6.3546 (5) Å, and interaction, out-of-bond range but enough to maintain the 6.9656 (5) Å, respectively. 29363 https://dx.doi.org/10.1021/acsomega.0c04175 ACS Omega 2020, 5, 29357−29372 ACS Omega http://pubs.acs.org/journal/acsodf Article Table 7. Intermolecular Interactions of (1,10- triple π···π interactions between the cations. Likewise, X··· Hphen)2(HgI4) (6)a Hg(II) interactions are negligible, the percentage of the surface being 0.0. H···A D−H >D−H···A interaction (Å) D···A (Å) (Å) (°) The intra-chain Hg(II)···Hg(II) distance tendency in 4−6 is C (3)−H (3)···I (2) 3.1712 3.913 (8) 0.951 136.25 not in line with that observed in 1−3, probably as a result of C (8)−H (8)···I (2) 3.0707 3.844 (8) 0.950 136.70 the spacing promoted by the presence of the water molecule in C (15)−H (15)···I (1) 3.0829 3.871 (10) 0.950 141.30 4, being 8.3158 (5), 7.8160 (7), and 8.911 (1) Å, respectively. C (20)−H (20)···I (1) 3.1712 3.913 (8) 0.950 136.25 The DD maps of the cations in 4 and 5 exhibit a similar π···π interactions behavior of the N−H/C−H···X interactions, suggesting the Cg (1)···Cg (2) 3.750 Å 50.08° presence of halogen σ-holes but in this case, the polarization a Cg (1): N3−C13−C14−C15−C16−C24; Cg (2): C16−C17− over the aromatic H atoms of the cations has bigger CC C18−C19−C23−C24. regions. The (1,10-Hphen)+ cations are close between them probably because they are bulkier and thus, the proximity of Since 2,2′-bipyridine tends to be in trans conformation and the positively charged N−H+ from neighboring cations is not planar,47 its diprotonation with the consequent positive promotes the formation of these CC regions (Figure 11). charge repulsion probably emphasize it. Planarity decreased Halogen atoms are likely to interact with electron-deficient π from mono- to diprotonation (rings torsion angle: 1.53 and systems over the periphery of the rings.4,5 Figure 11a,c 2.66° (1), 34.66° (2), and 51.74° (3)) and thus, π···π illustrates the Cl···π and Br···π interactions, respectively. In interactions are not favored in 2 and 3. What should be noted both, the halogen atoms are directed to the periphery of the is the nearly planar (2,2′-Hbipy)+. The lone electron pair of (1,10-Hphen)+ rings at a distance of 3.512 (2) Å (Cl (3)···C the neighboring N atom could stabilize the pyridinium proton (17)) and 3.383 (2) Å (Cl (3)···C (16)) in 4 or at 3.36 (1) Å and retain the planarity, favoring the assembly of (2,2′-Hbipy)+ (Br (3)···N (3)) and 3.39 (2) Å (Br (3)···C (13)) in 5. This cations through weak π···π interactions. preferential orientation has a more electrostatic character, and Structures Containing (1,10-Hphen)+ (4−6). In com- pounds 4 and 5, the Hirshfeld surface analysis with 2D it has been proven to promote CTs between the halogen atom fingerprint plot of N−H/C−H···X interactions (Figure 10) has and the electron-deficient π system.5 similar distance values compared to that of 1−3, the Overall, the (1,10-Hphen)+ retention of planarity promoted percentages of the surface being decreased (16.2 and 17.2 the formation of layered crystal structures increasingly from 4 (4) and 22.5 and 22.7 (5)) because cations tend to interact to 6 (Figure 12). Withal, the planarity of (2,2′-Hbipy)+ in 1 between themselves by π···π interactions (Table 9). resulted in an intermediate packing being the cations with The structural rigidity of (1,10-Hphen)+ cations hinders the similar disposition to the structures of 4−6 but without the rotation of the rings and the consequent loss of planarity, and formation of layers. Finally, the trans conformation of (2,2′- this structural feature promotes the formation of double or H2bipy)2+ in 2 and 3 leads to the worst cation···cation Figure 8. Hirshfeld surface representation and 2D fingerprint plot of the organic cations (left) and inorganic anions (right) of compounds (a) (2,2′-Hbipy)2(Hg2Cl6) (1), (b) (2,2′-H2bipy)(HgBr4) (2), and (c) (2,2′-H2bipy)(HgI4) (3). 29364 https://dx.doi.org/10.1021/acsomega.0c04175 ACS Omega 2020, 5, 29357−29372 ACS Omega http://pubs.acs.org/journal/acsodf Article Table 8. Percentage (%) of Hirshfeld Surface Implied in Each Interaction for Compounds 1−3 (X = Cl (1), Br (2), and I (3)) inorganic anions organic cations interaction 1 2 3 interaction 1 2 3 X···Hg(II) 3.0 1.5 0.1 N···X 1.0 3.0 3.0 3.0 X···X 2.2 7.9 4.1 H···X 31.5 28.8 42.6 50.1 X···N 2.2 3.4 2.8 C···C 8.0 8.2 3.4 1.7 X···C 6.0 8.9 10.3 C···X 3.7 3.1 7.0 9.7 X···H 78.3 73.4 78.7 Hg···X 3.8 1.8 0.2 Figure 9. 3D deformation density maps of compounds (a) 1, (b) 2, and (c) 3 highlighting CD (red) and CC (blue) regions. Dashed black lines indicate N−H···X contacts, while dashed blue lines highlight C−H···X interactions (X = Cl (1), Br (2), and I (3)). In detail, haptic-like interaction in panel (c). The isosurfaces are drawn at 0.008 eau−3. interaction and the intersperse distribution of the anions and valence band shows larger variations. Within this frame, all cations. compounds show an important contribution of the p orbitals Electronic Structure Analysis of 1−6. With the aim of of the halogen atom, the peaks for 5 (Figure 13e) and 6 analyzing the electronic structure and the effect of halide and (Figure 13f) being sharper where no inorganic−inorganic organic cation on the band gap of the six salts, PBE-D248,49 interactions are identified. However, in (1,10-Hphen)+ and/or periodic boundary calculations using the VASP code50,51 were chlorine-containing salts (Figure 13a,d−f), the contributions to performed (see details in the Experimental Section). The the valence band of p orbitals from the organic cation are not projected density of states (pDOS) of the six compounds neglectable. around the Fermi level are shown in Figure 13a−f. In this This is particularly remarkable for 4 where the highest in figure, we report the total DOS (black curves) and the energy occupied states are mainly composed of (1,10-Hphen)+ contributions arising from Hg(II) centers (red curve), the p orbitals. Therefore, the most likely excitations are expected halogen atoms (green curve), and the organic cations (blue to involve charge-transfer processes for bromine and iodine curve). Noteworthily, the pDOS reports the number of salts while for chlorine species, the charge-transfer character of electronic states at a given energy, thus defining the electronic the main excitations is expected to be smaller, particularly for bands of the compounds and the corresponding band gap. 4. For all compounds, the conducting band is mainly The gap between the valence and conducting band is also composed of the p orbitals of the organic cation, the highly dependent on the halide anion and, in a smaller extent, contribution of Hg(II) and the halide atom being always by the organic cation. In this context, chlorine-containing salts small. In particular, the contribution of the organic cation to (1 and 4) show the largest band gaps. Moreover, within those this conducting band shows less pronounced peaks for 5 and 6. compounds having the same organic cation, it decreases from This suggests a larger electronic delocalization, which could be chlorine to iodine. These results are consistent with the color associated with a stronger π···π interaction between the organic of the synthetized solids: 1, 4, and 5 are white; 2 is pale yellow; cations in these two salts. Instead, the composition of the and 3 and 6 are yellow. It may seem that the organic cation 29365 https://dx.doi.org/10.1021/acsomega.0c04175 ACS Omega 2020, 5, 29357−29372 ACS Omega http://pubs.acs.org/journal/acsodf Article Figure 10. Hirshfeld surface and 2D fingerprint plot representations of (a) water molecule in 4; (b) (1,10-Hphen)+ associated with water in 4, appointed as A; (c) (1,10-Hphen)+ associated with (HgCl4)2− appointed as B (left) and (HgCl4)2− anion in 4 (right); (d) two different (1,10- Hphen)+ in 5; and (e) (HgBr4)2− (left) (5) and (HgI4)2− (right) (6) anions. Table 9. Percentage (%) of Hirshfeld Surface Implied in Each Interaction for Compounds 4−6 (X = Cl (4), Br (5), and I (6))a inorganic anions organic cations interaction 4 5 6 interaction 4 5 X···Hg(II) 0.0 0.0 0.0 A H2O B X···X 0.0 0.0 0.9 N···X 1.0 0.0 2.0 0.9 1.0 X···N 3.9 2.4 0.1 H···X 16.2 33.4 17.2 22.5 22.7 X···C 9.0 8.3 4.1 C···C 7.7 0.0 7.5 10.5 4.7 X···H 83.0 85.6 90.9 C···X 5.3 0.0 4.2 3.0 3.2 Hg···X 0.0 0.0 0.0 O···H 0.0 27.6 0.0 0.0 0.0 a For identification of A and B see Figure 1010ca-. nature has almost no effect on the band gap per se. However, little influence on the band gap of the different salts, but as since it has a big influence on the crystal packing, it can clearly suggested for the bromine-containing compounds (2 indirectly modify the band gap. This is particularly the case of and 5), it is capable of indirectly modifying the band gap complexes 2 and 5 that only differ on the organic cation, and through its effect on the crystal packing. ■ they present very different band gaps (Figure 13b,e). Indeed, these two complexes show very different packing and CONCLUSIONS intermolecular interactions, which appears to be the origin of this large difference between their band gaps. A series of six Hg(II) halides (Cl, Br, and I) with aromatic In summary, optical properties of these compounds are conjugated (2,2′-Hbipy)+, (2,2′-H2bipy)2+ and (1,10-Hphen)+ associated with charge-transfer processes from the halogen cations have been synthesized. The study of their crystal atoms to the organic cations being more pronounced for structures enabled the identification of the intermolecular bromine- and iodine-containing compounds. The energy interactions and revealed their effect on the final packing. The difference between the valence and conducting band is largely small size and electronegativity of chlorine promoted a shorter influenced by the halogen, decreasing the band gap as Cl > Br anion···anion intra-chain distance than Br and I. In this regard, > I. In this set of compounds, the organic cation has directly the bulkiness of the (1,10-Hphen)+ cations does not 29366 https://dx.doi.org/10.1021/acsomega.0c04175 ACS Omega 2020, 5, 29357−29372 ACS Omega http://pubs.acs.org/journal/acsodf Article Figure 11. 3D deformation density maps highlighting CD (red) and CC (blue) regions of (a) (1,10-Hphen)+···Cl and (b) (1,10-Hphen)+···H2O associated in 4 and (c) (1,10-Hphen)+···Br associated in 5. Dashed black lines indicate N−H···X contacts, dashed blue lines highlight C−H/O− H···X interactions, and dashed white lines identify X··· π interactions. Dashed blue circles point large CC regions. The isosurfaces are drawn at 0.008 eau−3. Figure 12. c axis view of the crystal packing in (a−f) compounds 1−6, respectively. particularly increase this spacing but instead lengthens the light absorbers. Despite the band gap being highly dependent anion···anion inter-chain distance located at the sides of these on the halide and following the series Cl > Br > I, the chains. In addition, their planarity promoted the stacking of the modification of the crystal packing by the cations can ring, shortening the cation···cation distance. The electronic substantially vary it. This has been evinced in the pair of structure calculations revealed the p orbitals of the organic compounds 2 and 4, in which the better organic−inorganic cations as main contributors to the conducting band, while interactions in 2 promoted a smaller band gap. those of the halides defined the valence band. The electron transport in 1−6 is expected to involve charge-transfer processes favored in 2, 3, 5, and 6 where the band gap falls ■ EXPERIMENTAL SECTION Chemical Risks. Any mercury compound poses potential within the appropriate range for their potential application as health risks, and appropriate safety precautions along with 29367 https://dx.doi.org/10.1021/acsomega.0c04175 ACS Omega 2020, 5, 29357−29372 ACS Omega http://pubs.acs.org/journal/acsodf Article Figure 13. Projected density of states (pDOS) of the six compounds. Energies are referred to the Fermi level. The total (black curve) DOS is decomposed in those states arising from Hg(II) (red curve), the organic cation (blue curve), and the halogen atoms (green curve). disposal procedures must be taken in handling the complexes to evaporate slowly for 1 day until suitable crystals for single- reported here. Hg(II) halides sublime to emit highly poisonous crystal X-ray diffraction were grown. The solution was filtered fumes and must be handled only under appropriate conditions. off, and the resulting crystals were washed twice with cold Materials and Methods. Hg(II) halides (HgCl2, HgBr2, dichloromethane (10 mL) and diethyl ether (10 mL) and and HgI2), 2,2′-bipyridine (2,2′-bipy), 1,10-phenantroline dried under vacuum. monohydrate (1,10-phen), methanol (MeOH), and dichloro- The syntheses of 2−6 were performed by the same methane (CH2Cl2) solvents as well as hydrobromic acid (HBr, methodology but using the corresponding acid (HBr or HI) 48 wt. %) and hydroiodic acid (HI, 57 wt. %) were purchased and allowing to slowly evaporate for 1 day (3 and 4), 2 days (2 from Sigma-Aldrich. Hydrochloric acid (HCl, 37 wt. %) was and 5), or 3 days (6). purchased from Scharlau. DMSO-d6 was used for the 1H NMR 1: Yield: 0.207 g (40%). Elem. anal. calc. for experiments and was purchased from Eurisotop. All of them C20H18Hg2N4Cl6 (928.28 g/mol): C, 25.88; H, 1.95; N, were used without further purification. Elemental analyses (C, 6.04. Found: C, 25.63; H, 1.84; N, 6.04. FTIR-ATR H, and N) were carried out on a Thermo Scientific Flash 2000 (wavenumber, cm−1): 3236 (w), 3150 (w), 3031 (m) CHNS analyzer. PXRD patterns were recorded at 298 K on a [νar(C−H)], 2932−2322(m) [ν(N−H)], 1600 (s) [ν(C PANalytical X′Pert PRO MPD θ/θ powder diffractometer of C/CN)], 1524 (s) [ν(CC/CN)], 1447 (m) [ν(CC/ 240 mm radius in a configuration of a convergent beam with a CN)], 1387 (s) [δ(CC/CN)], 1285 (s), 1242 (m), focalizing mirror and a transmission geometry with flat samples 1165 (w) [δip(C−H)], 999 (w), 930 (w) [γ(N−H)], 802 (w), sandwiched between low absorbing films from 2 to 30° with a 760 (s) [δoop(C−H)], 623 (w), 541 (w). 1H NMR (360 MHz; step size of 0.0263° and a measuring time of 300s per step. The DMSO-d6; 298 K, TMS): δ = 4.80 [br, N−H], 7.87 [2H, m, samples were sandwiched between films of polyester Mylar of meta-H], 8.41 [2H, m, para-H], 8.66 [2H, t, 3J = 7.3 Hz, C− 3.6 μm of thickness. FTIR-ATR spectra were recorded on a CC−H], 8.88 [2H, d, 3J = 4.2 Hz, ortho-H]. Perkin Elmer spectrometer equipped with a universal 2: Yield: 0.209 g (74%). Elem. anal. calc. for C10H10HgN2Br4 attenuated total reflectance (ATR) accessory with a diamond (678.41 g/mol): C, 17.70; H, 1.49; N, 4.13. Found: C, 17.62; window in the range 4000−500 cm−1. 1H NMR spectra were H, 1.42; N, 4.08. FTIR-ATR (wavenumber, cm−1): 3373 (br) recorded on an NMR-FT Bruker360 MHz spectrometer in [ν(N−H)], 3232 (w), 3138−3023 (m) [νar(C−H)], 2983− DMSO-d6 solution at room temperature (r.t.). All chemical 2631 (m) [ν(N−H)], 1599 (s) [ν(CC/CN)], 1563 (w), shifts (δ) are given in ppm relative to TMS as the internal 1542 (w), 1523 (s) [ν(CC/CN)], 1473 (w), 1443 (m) standard. Simultaneous TG/DTA determinations were carried [ν(CC/CN)], 1411 (w), 1385 (m) [δ(CC/CN)], out in a Netzsch STA 409 instrument with an aluminum oxide 1281 (m), 1240 (m), 1167 (w) [δip(C−H)], 1088 (w), 1073 powder (Al2O3) crucible and heating at 5 °C·min−1 from 20 to (w), 1040 (w), 1014 (w), 997 (w), 940 (w), 920 (m) [γ(N− 400 °C under a nitrogen atmosphere with a flow rate of 80 mL· H)], 871 (w), 860 (w), 791 (w), 753 (s) [δoop(C−H)], 735 min−1. Al2O3 (PerkinElmer 0419-0197) was used as a (s) [δoop(C−H)], 714 (m), 623 (m), 538 (m). 1H NMR (360 standard. Further experimental data and PXRD, FTIR-ATR MHz; DMSO-d6; 298 K, TMS): δ = 5.32 [br, N−H], 7.88 and 1H NMR spectra, and TG/DTA determinations of 1−6 [2H, dd, 3J = 7.9 Hz, 3J = 5.0 Hz, meta-H], 8.42 [2H, td, 3J = are in the Supporting Information (Figures S1−S14). 7.9 Hz, 4J = 2.0 Hz, para-H], 8.66 [2H, d, 3J = 8.1 Hz, C−C Synthesis of Complexes 1−6. A methanolic solution (7 C−H], 8.89 [2H, dd, 3J = 5.1 Hz, 4J = 1.7 Hz, ortho-H]. mL) of HgCl2 (0.151 g, 0.557 mmol) was added dropwise to a 3: Yield: 0.152 g (53%). Elem. anal. calc. for C10H10HgN2I4 CH2Cl2 solution (14 mL) of 2,2′-bipy (0.173 g, 1.11 mmol) (866.41 g/mol): C, 13.86; H, 1.16; N, 3.23. Found: C, 13.67; with 0.2 mL of aqueous HCl (37 wt %). The solution was let H, 1.05; N, 3.11. FTIR-ATR (wavenumber, cm−1): 3209 (br) 29368 https://dx.doi.org/10.1021/acsomega.0c04175 ACS Omega 2020, 5, 29357−29372 ACS Omega http://pubs.acs.org/journal/acsodf Article [ν(N−H)]/[ν(O−H)], 3091−3050 (m) [νar(C−H)], 2945 Hz, 3J = 4.7 Hz, meta-H], 8.36 [4H, s, phenyl-H], 9.07 [4H, d, 3 (w), 2882 (w), 1627 (w), 1617 (w), 1582 (s) [ν(CC/C J = 8.3 Hz, para-H], 9.30 [4H, d, 3J = 5.1 Hz, ortho-H]. N)], 1569 (w), 1525 (s) [ν(CC/CN)], 1470 (w), 1457 X-Ray Crystallographic Data and Electronic Calcu- (m) [ν(CC/CN)], 1428 (s) [δ(CC/CN)], 1411 lations. Colorless (1, 4, and 5), yellow (3), and red (6) prism- (w), 1354 (w), 1326 (m), 1311 (w), 1277 (w), 1247 (w), like or colorless plate-like (2) specimens were used for the X- 1215 (m), 1178 (m) [δip(C−H)], 1150 (w), 1110 (w), 1089 ray crystallographic analysis. For all compounds, the frames (m), 1066 (w), 1037 (w), 1005 (w), 994 (w), 977 (w), 927 were integrated with the Bruker SAINT software package using (m), 917 (m) [γ(N−H)], 861 (w), 809 (w), 754 (s) [δoop(C− a narrow-frame algorithm (Tables 10 and 11). H)], 737 (m) [δoop(C−H)], 720 (s) [δoop(C−H)], 644 (w), The electronic structure of 1−6 has been analyzed by 633 (w), 611 (w), 541 (w). 1H NMR (360 MHz; DMSO-d6; performing periodic DFT calculations using the VASP 298 K, TMS): δ = 4.73 [br, N−H], 7.81 [2H, d, 3J = 6.3 Hz, code.50,51 All calculations were done at the PBE level of meta-H], 8.34 [2H, d, 3J = 7.9 Hz, para-H], 8.61 [2H, d, 3J = theory.48 van der Waals interactions were included through 8.3 Hz, C−CC−H], 8.85 [2H, d, 3J = 4.7 Hz, ortho-H]. Grimme’s D2 empirical correction.49 The use of D2 instead of 4: Yield: 0.127 g (32%). Elem. anal. calc. for D3 correction was based on previous results that showed that C24H20HgN4Cl4O (722.83 g/mol): C, 39.88; H, 2.79; N, 7.75. Found: C, 39.77; H, 2.71; N, 7.64. FTIR-ATR Table 10. Crystal Structure Refinement Data for (wavenumber, cm−1): 3178−2643 (br) [ν(O−H/N−H)], Compounds 1−3 3090−3022 (m) [νar(C−H)], 2994 (w), 2948 (w), 1633 (w), 1613 (m), 1595 (m) [ν(CC/CN)], 1537 (s) parameters 1 2 3 [ν(CC/CN)], 1495 (w), 1464 (m) [ν(CC/CN)], empirical C20H18Cl6Hg2N4 C10H10Br4HgN2 C10H10I4HgN2 1452 (m) [ν(CC/CN)], 1415 (m) [δ(CC/CN)], formula 1365 (w), 1338 (w), 1315 (w), 1279 (m), 1234 (m), 1185 formula weigh 928.26 678.43 866.39 (m) [δip(C−H)], 1152 (w), 1139 (w), 1098 (w), 1071 (w), T (K) 100(2) 100(2) 100(2) 1043 (w), 1034 (w), 1007 (w), 987 (w), 916 (w) [γ(N−H)], wavelength (Å) 0.71073 0.71073 0.71073 883 (w), 844 (s) [δoop(C−H)], 819 (m) [δoop(C−H)], 802 system, space monoclinic, P21/c monoclinic, P21/c monoclinic, (sh.) [δoop(C−H)], 771 (s) [δoop(C−H)], 714 (s) [δoop(C− group P21/c H)], 678 (w), 621 (m), 597 (w), 552 (w), 538 (w), 502 (w). unit cell dimensions 1 H NMR (360 MHz; DMSO-d6; 298 K, TMS): δ = 4.10 [br, a (Å) 7.4413(3) 8.4640(6) 7.8704(4) N−H], 8.20 [4H, dd, 3J = 8.2 Hz, 3J = 4.9 Hz, meta-H], 8.34 b (Å) 21.6102(12) 14.0128(10) 15.6908(7) [4H, s, phenyl-H], 9.05 [4H, dd, 3J = 8.2 Hz, 4J = 1.6 Hz, para- c (Å) 15.4817(8) 12.6748(8) 13.8093(7) H], 9.29 [4H, dd, 3J = 4.9 Hz, 4J = 1.5 Hz, ortho-H]. β (°) 94.962(2) 99.102(2) 90.282(2) 5: Yield: 0.271 g (74%). Elem. anal. calc. for C24H18HgN4Br4 V (Å3) 2480.3(2) 1484.36(18) 1705.33(14) (882.65 g/mol): C, 32.66; H, 2.06; N, 6.35. Found: C, 32.48; Z 4 4 4 H, 1.94; N, 6.13. FTIR-ATR (wavenumber, cm−1): 3193− Dcalc (g cm3) 2.486 3.036 3.375 3172 (m) [ν(N−H)], 3099−3040 (w) [νar(C−H)], 1635 (w), μ (mm−1) 13.029 21.116 16.250 1613 (m), 1597 (m) [ν(CC/CN)], 1542 (s) [ν(CC/ F(000) 1712 1216 1504 CN)], 1494 (m), 1464 (s) [ν(CC/CN)], 1451 (m), crystal size 0.213 × 0.089 × 0.330 × 0.233 × 0.075 × 0.065 × 1417 (m) [δ(CC/CN)], 1370 (m) [δ(CC/CN)], (mm3) 0.030 0.088 0.041 1336 (m), 1314 (m), 1285 (m), 1242 (m), 1225 (m), 1182 hkl ranges −10 ≤ h ≤ 10 −10 ≤ h ≤ 10 −11 ≤ h ≤ 9 (w) [δip(C−H)], 1148 (w), 1097 (w), 1071 (w), 1032 (w), 0 ≤ k ≤ 30 0 ≤ k ≤ 17 −22 ≤ k ≤ 22 960 (w) [γ(N−H)], 883 (w), 866 (w), 840 (s) [δoop(C−H)], 0 ≤ l ≤ 22 0 ≤ l ≤ 15 −18 ≤ l ≤ 19 807 (s) [δoop(C−H)], 794 (m) [δoop(C−H)], 755 (s) 2θ range (°) 2.748−30.532 2.182−26.426 2.895−30.547 [δoop(C−H)], 714 (s) [δoop(C−H)], 615 (m), 529 (m). 1H reflections 7586/7586/[Rint] 3019/3019/[Rint] 33,327/5178/ collected/ = 0.0502 = 0.0536 [Rint] = NMR (360 MHz; DMSO-d6; 298 K, TMS): δ = 4.24 [br, N− unique/[Rint] 0.0304 H], 8.22 [4H, dd, 3J = 8.2 Hz, 3J = 4.9 Hz, meta-H], 8.36 [4H, completeness to 99.9 99.0 99.5 s, phenyl-H], 9.07 [4H, dd, 3J = 8.2 Hz, 4J = 1.2 Hz, para-H], θ (%) 9.31 [4H, dd, 3J = 4.8 Hz, 4J = 1.2 Hz, ortho-H]. absorption semi-empirical semi-empirical semi-empirical correction 6: Yield: 0.255 g (72%). Elem. anal. calc. for C24H18HgN4I4 max. and min. 0.7461 and 0.5426 0.7454 and 0.7461 and (1039.74 g/mol): C, 26.87; H, 1.69; N, 5.23. Found: C, 26.65; transmis. 0.2515 0.5031 H, 1.52; N, 5.04. FTIR-ATR (wavenumber, cm−1): 3448 (br) refinement full matrix least- full matrix least- full matrix least- [ν(N−H)], 3094−3052 (w) [νar(C−H)], 2980 (w), 2942 (w), method squares on |F|2 squares on |F|2 squares on |F|2 2869 (w), 2784 (w), 2738 (w), 2660 (w), 1634 (w), 1614 data/restrains/ 7586/0/289 3019/0/154 5178/0/154 parameters (m), 1593 (s) [ν(CC/CN)], 1541 (s) [ν(CC/C goodness of fit 1.066 1.063 1.254 N)], 1493 (m) [ν(CC/CN)], 1467 (m), 1447 (m), 1414 (GOF) on |F|2 (m) [δ(CC/CN)], 1378 (s) [δ(CC/CN)], 1335 final R indices [I R1 = 0.0224, wR2 R1 = 0.0228, wR2 R1 = 0.0279, (m), 1314 (m), 1287 (m), 1240 (m), 1221 (w), 1189 (w) > 2σ(I)] = 0.0437 = 0.0545 wR2 = 0.0584 [δip(C−H)], 1147 (w), 1136 (w), 1098 (w), 1072 (w), 1029 R indices (all R1 = 0.0340, wR2 R1 = 0.0238, wR2 R1 = 0.0390, (w), 993 (w), 964 (w) [γ(N−H)], 934 (w) [γ(N−H)], 883 data) = 0.0503 = 0.0550 wR2 = 0.0659 extinction n/a n/a n/a (w), 840 (s) [δoop(C−H)], 823 (m) [δoop(C−H)], 807 (sh.) coefficient [δoop(C−H)], 767 (m) [δoop(C−H)], 714 (s) [δoop(C−H)], largest diff. peak 1.542 and −1.644 1.408 and −2.586 1.663 and 618 (m), 599 (w), 541 (m), 518 (m). 1H NMR (360 MHz; and hole (e −1.871 DMSO-d6; 298 K): δ = 4.39 [br, N−H], 8.23 [4H, dd, 3J = 8.7 Å−3) 29369 https://dx.doi.org/10.1021/acsomega.0c04175 ACS Omega 2020, 5, 29357−29372 ACS Omega http://pubs.acs.org/journal/acsodf Article Table 11. Crystal Structure Refinement Data for Compounds 4−6 parameters 4 5 6 empirical formula C24H20Cl4HgN4O C24H18Br4HgN4 C24H18I4HgN4 formula weigh 722.83 882.65 1070.61 T (K) 100(2) 100(2) 100(2) wavelength (Å) 0.71073 0.71073 0.71073 system, space group monoclinic, P21/c triclinic, P-1 monoclinic, P2/m unit cell dimensions a (Å) 16.3186(6) 7.8160(7) 8.991(3) b (Å) 10.6960(4) 9.0601(8) 19.040(8) c (Å) 14.6085(5) 18.7870(17) 9.004(3) α (°) 90 86.438(3) 90 β (°) 107.8560(10) 86.462(3) 93.322 (13) γ (°) 90 66.489(3) 90 V (Å3) 2427.00(15) 1216.59(19) 1538.8(10) Z 4 2 2 Dcalc (g cm3) 1.978 2.409 2.311 μ (mm−1) 6.809 12.916 9.031 F(000) 1392 820 964 Crystal size (mm3) 0.447 × 0.417 × 0.360 0.372 × 0.149 × 0.137 0.360 × 0.179 × 0.057 hkl ranges −23 ≤ h ≤ 22 −11 ≤ h ≤ 11 −12 ≤ h ≤ 12 0 ≤ k ≤ 15 −12 ≤ k ≤ 12 −26 ≤ k ≤ 27 0 ≤ l ≤ 20 0 ≤ l ≤ 26 −11 ≤ l ≤ 12 2θ range (°) 2.312−30.522 2.454−30.589 2.506−30.516 reflections collected/unique/[Rint] 7241/7241/[Rint] = 0.0522 7217/7217/[Rint] = 0.0462 35,555/4787/[Rint] = 0.0293 completeness to θ (%) 98.2 97.2 98.9 absorption correction semi-empirical semi-empirical semi-empirical max. and min. transmis. 0.7461 and 0.2506 0.7461 and 0.3802 0.7461 and 0.4860 refinement method full matrix least-squares on |F|2 full matrix least-squares on |F|2 full matrix least-squares on |F|2 data/restrains/parameters 7241/3/313 7217/0/298 4787/25/90 goodness of fit (GOF) on |F|2 1.059 1.104 1.132 final R indices [I > 2σ(I)] R1 = 0.0223, wR2 = 0.0540 R1 = 0.0389, wR2 = 0.0986 R1 = 0.0419, wR2 = 0.0983 R indices (all data) R1 = 0.0241, wR2 = 0.0547 R1 = 0.0398, wR2 = 0.0992 R1 = 0.0487, wR2 = 0.1032 extinction coefficient n/a n/a n/a largest diff. peak and hole (e Å−3) 1.602 and −2.548 1.600 and −2.138 2.617 and −1.774 for some transition metal oxides, the D2 correction leads to Accession Codes cell parameters that are closer to experimental data than CCDC 2012988-2012993 contain the supplementary crystallo- D3.52,53 Ionic cores were described with projector-augmented graphic data for this paper. These data can be obtained free of wave pseudopotentials,54,55 and the valence electrons were charge via www.ccdc.cam.ac.uk/data_request/cif, by emailing represented through a plane wave basis set with a kinetic data_request@ccdc.cam.ac.uk, or by contacting The Cam- energy cutoff of 400 eV. A (4,4,4) Monkhorst−Pack K-point bridge Crystallographic Data Centre, 12 Union Road, mesh56 was employed to describe the Brillouin zone. The Cambridge CB2 1EZ, UK; fax: +44 1223 336033. ■ energy convergence criteria were fixed to 10−5 and 10−4 eV for electronic and geometry relaxations, respectively. Further AUTHOR INFORMATION details about crystal structure refinement and electronic calculations are in the Supporting Information. Corresponding Author ■ ́ Josefina Pons − Departament de Quimica, Universitat ASSOCIATED CONTENT Autònoma de Barcelona, Barcelona 08193, Spain; * sı Supporting Information orcid.org/0000-0002-9546-6828; Email: Josefina.Pons@ The Supporting Information is available free of charge at uab.es https://pubs.acs.org/doi/10.1021/acsomega.0c04175. Authors Crystallographic data of compound 1 (CIF) Francisco Sánchez-Férez − Departament de Quimica,́ Crystallographic data of compound 2 (CIF) Universitat Autònoma de Barcelona, Barcelona 08193, Spain Xavier Solans-Monfort − Departament de Quimica, ́ Universitat Crystallographic data of compound 3 (CIF) Crystallographic data of compound 4 (CIF) Autònoma de Barcelona, Barcelona 08193, Spain Teresa Calvet − Departament de Mineralogia, Petrologia i Crystallographic data of compound 5 (CIF) Geologia Aplicada, Universitat de Barcelona, Barcelona 08028, Crystallographic data of compound 6 (CIF) Spain Further details about crystal structures refinement, Mercè Font-Bardia − Unitat de Difracció de Raig-X, Centres electronic calculations, PXRD, FTIR-ATR and 1H ́ i Tecnològics de la Universitat de Barcelona Cientifics NMR spectra, and TG/DTA determination (PDF) (CCiTUB), Universitat de Barcelona, Barcelona 08028, Spain 29370 https://dx.doi.org/10.1021/acsomega.0c04175 ACS Omega 2020, 5, 29357−29372 ACS Omega http://pubs.acs.org/journal/acsodf Article Complete contact information is available at: (16) Albero, J.; Asiri, A. M.; García, H. Influence of the Composition https://pubs.acs.org/10.1021/acsomega.0c04175 of Hybrid Perovskites on Their Performance in Solar Cells. J. Mater. Chem. A 2016, 4, 4353−4364. Notes (17) Saparov, B.; Mitzi, D. B. Organic-Inorganic Perovskites: Structural Versatility for Functional Materials Design. Chem. Rev. The authors declare no competing financial interest. 2016, 116, 4558−4596. ■ ACKNOWLEDGMENTS J.P. acknowledges financial support from the CB615921 (18) Bharara, M. S.; Bui, T. H.; Parkin, S.; Atwood, D. A. Structure- Directing Influence of Halide in Mercury Thiolate Clusters. Inorg. Chem. 2005, 44, 5753−5760. (19) Bharara, M. S.; Bui, T. H.; Parkin, S.; Atwood, D. A. project, the CB616406 project from “Fundació La Caixa”, Mercurophilic Interaction in Novel Polynuclear Hg(II)-2- Amino- and the 2017SGR1687 project from the Generalitat de ethanethiolates. Dalton Trans. 2005, 3874−3880. Catalunya. X.S.M. acknowledges financial support from (20) Bharara, M. S.; Parkin, S.; Atwood, D. A. Solution and Solid- MINECO (CTQ2017-89132-P) and the Generalitat de State Study of Heteroleptic Hg(II)-Thiolates: Crystal Structures of Catalunya (2017SGR132). F.S.F. acknowledges the PIF pre- [Hg4I4(SCH2CH2NH2)4] and [Hg4I8(SCH2CH2NH3)2]. Inorg. Chem. doctoral fellowship from the Universitat Autònoma de 2006, 45, 2112−2118. (21) Bharara, M. S.; Parkin, S.; Atwood, D. A. Mercury(II) 2- Barcelona. X.S.M. is also grateful for the Professor Agregat Aminoethanethiolate Clusters: Intramolecular Transformations and Serra Húnter position. Mechanisms. Inorg. Chem. 2006, 45, 7261−7268. ■ REFERENCES (1) Zarick, H. F.; Soetan, N.; Erwin, W. R.; Bardhan, R. Mixed (22) Spengler, R.; Zouari, R.; Zimmermann, H.; Ben Salah, A.; Burzlaff, H. 1,3-Propanediammonium Tetrachloromercurate. Acta Crystallogr. Sect. C Cryst. Struct. Commun. 1998, 54, 1628−1631. (23) Amami, M.; Zouari, R.; Ben Salah, A.; Burzlaff, H. 1,4- Halide Hybrid Perovskites: A Paradigm Shift in Photovoltaics. J. Butanediammonium Tetrachloromercurate(II). Acta Crystallogr., Sect. Mater. Chem. A 2018, 6, 5507−5537. E 2002, 58, m357−m359. (2) Oswald, I. W. H.; Ahn, H.; Neilson, J. R. Influence of Organic (24) Belhouchet, M.; Wamani, W.; Mhiri, T. Synthesis, Structure Cation Planarity on Structural Templating in Hybrid Metal-Halides. and Spectroscopic Investigations of Two New Organic-Inorganic Dalton Trans. 2019, 48, 16340−16349. Hybrids NH3(C6H4)2NH3CuCl4 and NH3(C6H4)2NH3HgCl. IOP (3) Chatterjee, S.; Pal, A. J. Influence of Metal Substitution on Conf. Ser.: Mater. Sci. Eng. 2010, 13, No. 012039. Hybrid Halide Perovskites: Towards Lead-Free Perovskite Solar Cells. (25) Barbieri, A.; Accorsi, G.; Armaroli, N. Luminescent Complexes J. Mater. Chem. A 2018, 6, 3793−3823. beyond the Platinum Group: The d10 Avenue. Chem. Commun. 2008, (4) Berryman, O. B.; Bryantsev, V. S.; Stay, D. P.; Johnson, D. W.; 2185−2193. Hay, B. P. Structural Criteria for the Design of Anion Receptors: The (26) Guerrero, M.; Vázquez, S.; Ayllón, J. A.; Calvet, T.; Font- Interaction of Halides with Electron-Deficient Arenes. J. Am. Chem. Bardia, M.; Pons, J. Zn(II) and Cd(II) Coordination Dimers Based on Soc. 2007, 129, 48−58. Mixed Benzodioxole-Carboxylate and N-Donor Ligands: Synthesis, (5) Albrecht, M.; Wessel, C.; De Groot, M.; Rissanen, K.; Lüchow, Characterization, Crystal Structures and Photoluminescence Proper- A. Structural Versatility of Anion-π Interactions in Halide Salts with ties. ChemistrySelect 2017, 2, 632−639. Pentafluorophenyl Substituted Cations. J. Am. Chem. Soc. 2008, 130, (27) Ejarque, D.; Sánchez-Férez, F.; Ayllón, J. A.; Calvet, T.; Font- 4600−4601. Bardia, M.; Pons, J. Diverse Structures and Dimensionalities in (6) Lim, J. Y. C.; Beer, P. D. Sigma-Hole Interactions in Anion Zn(II), Cd(II), and Hg(II) Metal Complexes with Piperonylic Acid. Recognition. Chem 2018, 4, 731−783. Cryst. Growth Des. 2020, 20, 383−400. (7) Politzer, P.; Murray, J. S.; Clark, T.; Resnati, G. The σ-Hole (28) Moreno-Gómez, L.; Sánchez-Férez, F.; Calvet, T.; Font-Bardia, Revisited. Phys. Chem. Chem. Phys. 2017, 19, 32166−32178. M.; Pons, J. Zn(II) and Cd(II) Monomer, Dimer and Polymer (8) Nepal, B.; Scheiner, S. NX···Y Halogen Bonds. Comparison with Compounds Coordinated by Benzoic Acid and 4-Acetylpyridine: NH···Y H-Bonds and CX···Y Halogen Bonds. Phys. Chem Chem. Phys. Synthesis and Crystal Structures. Inorg. Chim. Acta 2020, 506, 2016, 18, 18015−18023. 119561. (9) Melandri, S. “Union Is Strength”: How Weak Hydrogen Bonds (29) Ali, B. F.; Al-Far, R. Isostructural Series of (2,2′-Bipyridinium) Become Stronger. Phys. Chem. Chem. Phys. 2011, 13, 13901−13911. Tetrabromometallate(II); Intermolecular Interactions in the Struc- (10) Oswald, I. W. H.; Mozur, E. M.; Moseley, I. P.; Ahn, H.; tures of (BpyH2)[MBr4]; M = Zn Hg and Co. J. Chem. Crystallogr. Neilson, J. R. Hybrid Charge-Transfer Semiconductors: (C7H7)SbI4, 2008, 38, 689−693. (C7H7)BiI4, and Their Halide Congeners. Inorg. Chem. 2019, 58, (30) Tsuge, M.; Lai, C. P.; Lee, Y. P. Infrared Spectra of 3-Hydroxy- 5818−5826. (1H)-Pyridinium Cation and 3-Hydroxy-(1H)-Pyridinyl Radical (11) Savory, C. N.; Palgrave, R. G.; Bronstein, H.; Scanlon, D. O. Isolated in Solid Para -Hydrogen. J. Chem. Phys. 2018, 149, Spatial Electron-Hole Separation in a One Dimensional Hybrid No. 014306. Organic-Inorganic Lead Iodide. Sci. Rep. 2016, 6, 20626−20627. (31) Rutkowski, K. S.; Melikova, S. M.; Rospenk, M.; Koll, A. Strong (12) Chen, W. T.; Zeng, X. R.; Fang, X. N.; Li, X. F.; Liu, L. M. and Weak Effects Caused by Non Covalent Interactions between Synthesis, Structure and Properties of (4,4′-H2Bipy)[HgBr4] · H2O Chloroform and Selected Electron Donor Molecules. Phys. Chem. with Strong Fluorescence. Inorg. Chem. Commun. 2007, 10, 223−225. Chem. Phys. 2011, 13, 14223−14234. (13) Smith, I. C.; Hoke, E. T.; Solis-Ibarra, D.; McGehee, M. D.; (32) Golec, B.; Das, P.; Bahou, M.; Lee, Y.-P. Infrared Spectra of the Karunadasa, H. I. A Layered Hybrid Perovskite Solar-Cell Absorber 1-Pyridinium(C5H5NH+) Cation and Pyridinyl(C5H5NH and 4- with Enhanced Moisture Stability. Angew. Chem. 2014, 53, 11232− C5H6N) Radicals Isolated in Solid Para-Hydrogen. J. Phys. Chem. A 11235. 2013, 117, 13680−13690. (14) Mao, L.; Stoumpos, C. C.; Kanatzidis, M. G. Two-Dimensional (33) Williams, D. H.; Fleming, I. Spectroscopic Methods in Organic Hybrid Halide Perovskites: Principles and Promises. J. Am. Chem. Soc. Chemistry; 7th ed.; Springer Nature: Cham, Switzerland, 2008. 2019, 141, 1171−1190. (34) Teleb, S. M.; Gaballa, A. S. Preparation and Spectroscopic (15) Cheng, P.; Wang, P.; Xu, Z.; Jia, X.; Wei, Q.; Yuan, N.; Ding, J.; Studies on Charge-Transfer Complexes of 2,2′-Bipyridine with Picric Li, R.; Zhao, G.; Cheng, Y.; Zhao, K.; Liu, S. F. Ligand-Size Related and Chloranilic Acids. Spectrochim. Acta, Part A 2005, 62, 140−145. Dimensionality Control in Metal Halide Perovskites. ACS Energy Lett. (35) Yang, L.; Powell, D. R.; Houser, R. P. Structural Variation in 2019, 4, 1830−1838. Copper(I) Complexes with Pyridylmethylamide Ligands: Structural 29371 https://dx.doi.org/10.1021/acsomega.0c04175 ACS Omega 2020, 5, 29357−29372 ACS Omega http://pubs.acs.org/journal/acsodf Article Analysis with a New Four-Coordinate Geometry Index, T4. J. Chem. (56) Pack, J. D.; Monkhorst, H. J. “special Points for Brillouin-Zone Soc Dalton Trans. 2007, 9, 955−964. Integrations”-a Reply. Phys. Rev. B 1977, 16, 1748−1749. (36) Rabeand, S.; Mü l ler, U. Crystal Structure of Bis- (Tetraphenylphosphonium) Octachlorotrimercurate, [P- (C6H5)4]2[Hg3Cl8]. Zeitschrift für Krist. - New Cryst. Struct. 1999, 214, 277−278. (37) Fernando, I. R.; Mezei, G. Blue-Colored, Linear Rigid-Axle [2]Pseudorotaxanes: Metal-Binding Properties, Crystal Structures, and Blue/Red Dichroism. Inorg. Chem. 2012, 51, 3156−3160. (38) Xu, L.; Gao, J. X.; Chen, X. G.; Hua, X. N.; Wu, D. H.; Liao, W. Q. Unprecedented Dielectric Bistable Switching in a Binuclear Hg(II) Based Hybrid Compound. Eur. J. Inorg. Chem. 2019, 2019, 800−807. (39) Oueslati, A.; Chaabane, I.; Adil, K.; Hlel, F. Structural Characterization and Infrared and Electrical Properties of the New Inorganic-Organic Hybrid Compound [N(C3H7)4]2[Hg2Cl6]. J. Chem. 2013, 2013, 1−10. (40) Chen, J.-X.; Zhang, W.-H.; Ren, Z.-G.; Zhang, Y.; Lang, J.-P. Bis[4(Trimethylammonio)Phenyl]Disulfide Tetraiodomercurate(II). Acta Crystallogr., Sect. E: Struct. Rep. Online 2005, 61, 60−62. (41) Ishihara, H.; Horiuchi, K.; Svoboda, I.; Fuess, H.; Gesing, T. M.; Buhl, J.-C.; Terao, H. Crystal Structures of Piperazinium Tetrahalogenometallates (II)[C4H12N2]MX4 (M = Zn, Hg; X = Br, I). Z. Naturforsch. B 2006, 61, 69−72. (42) Ye, Z. Y.; Zhang, Z. Y.; Huo, L. H.; Deng, Z. P.; Zhang, X. F.; Gao, S. Mercury Supramolecular Architectures Constructed from Flexible Unsymmetrical Bis(Pyridyl) Ligands: Structural Motif Mediated by Mercury-Halide Clusters, Ligand Conformations and Non-Covalent Interactions. Polyhedron 2016, 117, 338−351. (43) Govindan, E.; Thirumurugan, S.; Ganeshraja, A. S.; Anbalagan, K.; Subbiahpandi, A. Bis(1,10-Phenanthrolin-1-Ium) Tetrachlorido- zincate Monohydrate. Acta Crystallogr., Sect. E 2014, 70, m53. (44) Feng, G.; Evangelisti, L.; Favero, L. B.; Grabow, J. U.; Xia, Z.; Caminati, W. On the Weak O-H···halogen Hydrogen Bond: A Rotational Study of CH3CHClF···H2O. Phys. Chem. Chem. Phys. 2011, 13, 14092−14096. (45) Turner, M. J.; McKinnon, J. J.; Wolff, S. K.; Grimwood, D. J.; Spackman, P. R.; Jayatilaka, D.; Spackman, M. A. CrystalExplorer17. University of Western Australia, 2017. (46) Hernández-Haro, N.; Ortega-Castro, J.; Martynov, Y. B.; Nazmitdinov, R. G.; Frontera, A. DFT Prediction of Band Gap in Organic-Inorganic Metal Halide Perovskites: An Exchange-Correla- tion Functional Benchmark Study. Chem. Phys. 2019, 516, 225−231. (47) Göller, A.; Grummt, U. W. Torsional Barriers in Biphenyl, 2,2′- Bipyridine and 2-Phenylpyridine. Chem. Phys. Lett. 2000, 321, 399− 405. (48) Perdew, J. P.; Burke, K.; Ernzerhof, M. Generalized Gradient Approximation Made Simple. Phys. Rev. Lett. 1996, 77, 3865−3868. (49) Grimme, S. Accurate Description of Van Der Waals Complexes by Density Functional Theory Including Empirical Corrections. J. Comput. Chem. 2004, 25, 1463−1473. (50) Kresse, G.; Hafner, J. Ab Initio Molecular Dynamics for Liquid Metals. Phys. Rev. B 1993, 47, 558−561. (51) Kresse, G.; Furthmüller, J. Efficient Iterative Schemes for Ab Initio Total-Energy Calculations Using a Plane-Wave Basis Set. Phys. Rev. B 1996, 54, 11169−11186. (52) Heras-Domingo, J.; Sodupe, M.; Solans-Monfort, X. Interaction between Ruthenium Oxide Surfaces and Water Molecules. Effect of Surface Morphology and Water Coverage. J. Phys Chem. C 2019, 123, 7786−7798. (53) González, D.; Heras-Domingo, J.; Pantaleone, S.; Rimola, A.; Rodríguez-Santiago, L.; Solans-Monfort, X.; Sodupe, M. Water Adsorption on MO2 (M = Ti, Ru, and Ir) Surfaces. Importance of Octahedral Distortion and Cooperative Effects. ACS Omega 2019, 4, 2989−2999. (54) Blöchl, P. E. Projector Augmented-Wave Method. Phys. Rev. B 1994, 50, 17953−17979. (55) Kresse, G.; Joubert, D. From Ultrasoft Pseudopotentials to the Projector Augmented-Wave Method. Phys. Rev. B - Condens. Matter Mater. Phys. 1999, 59, 1758−1775. 29372 https://dx.doi.org/10.1021/acsomega.0c04175 ACS Omega 2020, 5, 29357−29372