Competition vs. Cooperativity of I⋅⋅⋅Omorpholinyl and I⋅⋅⋅Cl−M Halogen Bonds in Cocrystals of Zinc(II) and Copper(II) Coordination Compounds Carrying Multiple Acceptor Sites
Abstract
In order to explore a strategy for synthesizing halogen-bonded metal-organic cocrystals by utilizing metal complexes whose pendant chloride group and the morpholinyl oxygen atom enables halogen bonding, we have synthesized four pentacoordinated Cu(II) and Zn(II) complexes of the MCl2L general formula (L=imines prepared by the condensation reaction of 4-aminoethylmorpholine with 2-pyridinecarboxyaldehide or 2-acetylpyridine). The prepared metal complexes were further cocrystallized with selected iodoperfluorinated benzenes. Out of 20 combinations, 14 experiments yielded crystals suitable for single-crystal X-ray diffraction. Structural analysis revealed that in 7 cocrystals halogen bonds are formed both with morpholinyl oxygen as well as with chloride atoms. In 6 cocrystals only I⋅⋅⋅Cl halogen bonds are present, while only one cocrystal exclusively featured I⋅⋅⋅Omorpholinyl halogen bonds. We observed 5 halogen bonding motifs to the MCl2 moiety, in which each chloride atom can be an acceptor of one halogen bond, two, or none at all. The most common motif in our work (6 cocrystals) is where one chlorine atom is an acceptor of one halogen bond, while the other chlorine atom does not participate in halogen bonding. The crystal packing in the prepared cocrystals is directed by halogen-bonded architectures which are either zero-, one- or two-dimensional.
Introduction
In the past three decades, halogen bonding1 has become widely recognized as a reliable design element in crystal engineering of cocrystals.2 Although numerous reports and reviews dealing with halogen bonding in single-component metal-organic solids and salts have been published to date,3 and the majority of studied halogen-bonded cocrystals have involved organic molecules, systematic exploration of cocrystal formation using (neutral) metal coordination compounds as building blocks is relatively limited.4 Numerous studies have been focused on molecules with halogen atoms bonded to an electronegative atom or an ethynyl or perfluronated moiety, as halogen bond donors in cocrystal design.5, 6b To date the most commonly used halogen bond donors in crystal engineering are perhalogenated benzenes (PHB). This family of classical halogen bond donors, which are commercially available and appropriate for supramolecular chemistry, has been introduced by Dehnicke and co-workes in 1999 (the first salt cocrystal of 1,4-diiodotetrafluorobenzene)6a as well as by Resnati and Metrangolo in 2000 (the first cocrystal of 1,4-diiodotetrafluorobenzene)6b and later by other groups for other PHBs.7 By searching the Cambridge Structural Database (CSD),8 one can find 1627 deposited data sets corresponding to multicomponent crystals containing PHBs C6Y5X (Y=F, Cl, Br, I; X=Cl, Br, I). A subset of this data, 426 data sets, corresponds to multicomponent crystals containing metal-organic building blocks (in comparison, by 2018 only 42 data sets had been deposited). The rising interest in cocrystals involving metal coordination compounds is not surprising, given that metal-containing species can exhibit captivating and potentially applicable properties (i. e. electric,9 magnetic10 etc.) Additionally, from a crystal engineering perspective, coordination compounds offer an avenue for obtaining a diverse array of geometries typically unreachable when using only organic molecules. Coordination compounds can also be tailored by an introduction of donor and acceptor sites to the ligand periphery, thus enabling the formation of targeted interactions between the complex molecules and their supramolecular environment.11
The design of a majority of halogen-bonded metal-organic cocrystals prepared to date has been based on strategies using coordination compounds as halogen bond acceptors and organic molecules as donors.4a The acceptor functionality may be introduced directly to the metal center as a halogenido12 or pseudohalogenido13 ligand, or as an additional functionality (usually nitrogen4a, 11c, 14 or oxygen15 atoms) on the periphery of an organic ligand. Additionally, many metal complexes may act as halogen bond acceptors even without added halogen acceptor groups, employing either the coordinated atoms of the chelating ligands16 or even the metal atom itself as halogen acceptor sites.17 The first above-mentioned strategy is well-represented in the literature, in keeping with the ubiquitous utilization of halogenide ligands as halogen bond acceptors. Systematic studies of metal-organic cocrystals designed by employing this strategy were first performed by the Rissanen group.12a Searching the CSD, we found 67 data sets for the [M–X, XPHB] motif (M being any transition metal atom and X being Cl, Br and I) with the M−X⋅⋅⋅XPHB halogen bond present in 56 data sets. Of those, 11 data sets correspond to structures with the M−I⋅⋅⋅XPHB motif, 8 data sets have the M−Br⋅⋅⋅XPHB motif and 37 data sets have the M−Cl⋅⋅⋅XPHB motif. Most studies have revealed that chloride ligands are prolific halogen-bond acceptor sites in metal-organic building blocks, underscoring the importance of M–Cl⋅⋅⋅I motifs as a reliable approach in the rational design of metal-organic cocrystals based on halogen bonding.12b Another strategy that has been employed relies on the introduction of a halogen acceptor functionality on the periphery of a ligand. Studies based on this strategy mostly utilize metal complexes carrying pyridine nitrogen14 or carbonyl oxygen15d, 15e, 18 atom as halogen bond acceptors. There are no systematic studies of cocrystals with metal complexes carrying the morpholine oxygen atom, in spite of the fact that the morpholinyl oxygen atom has been established as a prominent acceptor site for halogen bonding in the formation of cocrystals with organic building blocks.19 There are currently 16 data sets containing the Omorpholinyl⋅⋅⋅XPHB motif in the CSD. When we narrowed the search to the [M, Omorpholinyl⋅⋅⋅XPHB] motif (M being any transition metal atom), we found only 2 data sets. This motif has first been used by Friščić and coworkers in the planned cocrystallization of nickel(II) and cobalt(II) complexes with morpholine and thiomorpholine ligands as halogen bond acceptors.4b In both cocrystals, the ligands coordinate the metal centre through the nitrogen atom, leaving the oxygen or sulphur atom free to form halogen bonds with the donor molecule. The main challenge in the implementation of this approach (which involves labile, weakly bound ligands as halogen bond acceptors) lies in adjusting the synthetic/crystallization procedure so that the metal complex does not decompose. Furthermore, exploration of halogen-bonded cocrystallization of molecules containing a morpholine moiety was recently studied by our group.20 We have explored the transferability of X⋅⋅⋅Omorpholinyl bonds from smaller to larger building blocks, from N-aminomorpholine to two larger derivatives, a Schiff base (L) derived from 2-hydroxy-1-naphthaldehyde and the corresponding copper(II) complex CuL2.
Guided by the insights gathered from our previous research, in this work we decided to explore metal coordination compounds with multiple acceptor sites, featuring both chloride ligands and a tridentate organic ligand containing a morpholine moiety. The main goal of our present work was to systematically research the possibility of combining halogen bonding strategies in order to design novel halogen-bonded multicomponent systems. This would also allow us to ascertain the reliability of the used acceptor sites and investigate their simultaneous influence on halogen bonding in the same supramolecular environment. For this purpose, we have selected four coordination compounds, pentacoordinated Cu(II) and Zn(II) complexes of the MCl2L general formula. Ligands (L) were prepared by a condensation reaction from 4-aminoethylmorpholine and either 2-pyridinecarboxaldehyde (pm) or 2-acetylpyridine (apm).21 All four metal complexes have been cocrystallized with selected perfluorinated iodobenzenes: 1,2-diiodotetrafluorobenzene (12 tfib), 1,3-diiodotetrafluorobenzene (13 tfib), 1,4-diiodotetrafluorobenzene (14 tfib), 1,3,5-trifluoro-2,4,6- triiodobenzene (135 tfib) and iodopentafluorobenzene (ipfb) (Scheme 1).
Halogen bond acceptor and donor species used within this study
Results and Discussion
In order to examine whether the prepared metal complexes will act as acceptors in cocrystals, we first performed liquid-assisted grinding22 of the reactants in a 1 : 1 stoichiometric ratio. Out of 20 possible combinations of donors and acceptors, 14 of them (70 %) yielded novel crystalline phases. Solution crystallization experiments were subsequently undertaken to prepare crystals suitable for determination of molecular and crystal structures by single-crystal X-ray diffraction. These crystallization experiments were performed by simple evaporation methods, yielding appropriate single crystals of 14 cocrystals. Structural analysis revealed that the cocrystals feature diverse halogen bonding motifs (Figure 1). In 7 cocrystals halogen bonds are formed both with the morpholinyl oxygen atom and chloride ligands, in 6 cocrystals only I⋅⋅⋅Cl halogen bonds are present, while in only one cocrystal, [Zn(pm)Cl2](14 tfib), are I⋅⋅⋅Omorpholinyl halogen bonds exclusively formed. We observed 5 halogen bonding motifs to the MCl2 moiety, in which each chloride atom can be an acceptor of one halogen bond, two, or none at all (Figure 2). The most common motif in our work (6 cocrystals) is where one chlorine atom is an acceptor of one halogen bond, while the other chlorine atom does not participate in halogen bonding. We compared this result to data deposited in CSD for cocrystals which contain the M–Cl⋅⋅⋅XPHB motif (Figure 2). Of the 37 data sets that we mentioned before, we analyzed only 15 that correspond to cocrystals which contain metal complexes with chloride ligands in
Parts of the crystal structure in cocrystals of: a) [Cu(pm)Cl2](12 tfib)2; b) [Cu(pm)Cl2](13 tfib); c) [Cu(pm)Cl2](135 tfib); d) [Cu(pm)Cl2]2(14 tfib)3; e) [Cu(apm)Cl2](12 tfib)2; f) [Cu(apm)Cl2]2(14 tfib)3; g) [Cu(apm)Cl2](135 tfib)(CH3NO2); h) [Zn(pm)Cl2](12 tfib); i) [Zn(pm)Cl2](13 tfib); j) [Zn(pm)Cl2](135 tfib); k) [Zn(pm)Cl2]2(14 tfib); l) [Zn(pm)Cl2](ipfb); m) [Zn(apm)Cl2](12 tfib) and n) [Zn(apm)Cl2](14 tfib).
Halogen bonding motifs with the MCl2 moiety and their occurrence in our work and in the CSD.
the cis position,8 because the other 22 data sets correspond to cocrystals with metal complexes containing either one chlorine ligand on the metal, two chloride ligands in the trans position, or polynuclear complexes. A vast majority of cocrystals in the literature exhibit the motif where both chlorine atoms are acceptors of one halogen bond. This is in contrast to our cocrystals, where the motif is present in only two cases. The observed differences in occurrence can be attributed to the additional acceptor moiety that is peripherally located on the metal complexes used in our research. In all cocrystals containing the I⋅⋅⋅O motif, the oxygen atom is an acceptor of one halogen bond. Relative shortening values1 of I⋅⋅⋅Cl halogen bonds vary from 1 % to 17 %, averaging at 11 %, whilst for the I⋅⋅⋅O halogen bonds values are between 15 % and 18 %, averaging at 17 %. Although I⋅⋅⋅O contacts are present in [Cu(pm)Cl2](13 tfib) and [Cu(apm)Cl2](135 tfib)(CH3NO2) cocrystals, interaction angles (C−I⋅⋅⋅O) are just below 140°, and I⋅⋅⋅O relative shortening values are almost negligible. Therefore, while these contacts are not included in Figure 3, we included them when describing supramolecular architectures due to their importance. It can also be noted from structural data that halogen bonds involving peripherally located morpholine oxygen atoms, though less frequent, are shorter and more directional than halogen bonds with the more reliable chloride ligand. The reduced directionality and consequently longer relative shortening values observed for chloride ligands may be attributed to more sterically demanding environments due to their proximity to the central metal ion. By comparing relative shortening values and halogen bond angles to those of cocrystals from our previous works that utilized the M−Cl⋅⋅⋅I motif12b as well as to previous investigations on the proclivity of the morpholine fragment as a halogen bond acceptor,20 it can be observed that the relative shortening values (see Table S2 in Supporting Information) are on average somewhat shorter in the cocrystals presented herein than in similar systems comprising only chloride ligands as acceptor sites. Thus, we have confirmed our hypothesis that the peripheral introduction of another acceptor site on the ligand can reduce the acceptor potential of the reliable M–Cl⋅⋅⋅I motif. In the context of the extended supramolecular architectures present in cocrystals, the obtained halogen bonding motifs are diverse and distinct from one cocrystal to another. According to the dimensionality obtained by halogen bonding, we can divide them into three groups: discrete supramolecular complexes (0D, 6/14 cocrystals), chains (1D, 4/14 cocrystals) and networks (2D, 4/14 cocrystals). In our data set, discrete complexes are formed mostly with zinc coordination compounds and either ipfb, 13 tfib, 135 tfib (Figure 4), the exception is the [Cu(pm)Cl2](135 tfib) cocrystal. Halogen-bonded chains are exclusively formed with 12 tfib (Figure 5), while 2D networks are formed exclusively with copper coordination compounds (Figure 6). There are four different bonding motifs in 0D systems. The most frequent one (4/6 cocrystals) is a tetrameric motif where coordination compound molecules are interconnected through cooperative I⋅⋅⋅O and I⋅⋅⋅Cl halogen bonding via two donor molecules. This motif is exhibited in the [Cu(pm)Cl2](135 tfib), [Zn(pm)Cl2](135 tfib), [Zn(pm)Cl2](13 tfib) and [Zn(apm)Cl2](14 tfib) cocrystals. In all these cocrystals, discrete complexes are connected via CAr–H⋅⋅⋅O or CAr–H⋅⋅⋅Cl hydrogen bonds, or in some specific instances even Cl⋅⋅⋅π interactions or displacement π⋅⋅⋅π stacking into a 3D network. Utilizing molecules 13 tfib and 135 tfib, which have donor atoms at an angle of 120°, is conducive for forming the tetrameric motif. Exceptions can be found in the [Zn(apm)Cl2](14 tfib) cocrystal where this motif is obtained by diagonally bending the acceptor geometry, and in the [Cu(pm)Cl2](13 tfib) cocrystal, where halogen bonding does not stop at a tetrameric discrete complex, but leads to the formation of a 2D network via bifurcation of an iodine donor atom and rather complex interconnecting motifs (Figure 6b).
a) Comparison of the shortest I⋅⋅⋅Cl and I⋅⋅⋅O halogen bonds in each obtained cocrystal; b) Scatterplot of halogen bond angles and respective values of relative shortening for each halogen bond in the obtained cocrystals.
Parts of the crystals structure in: a) [Zn(pm)Cl2](13 tfib), b) [Zn(pm)Cl2](135 tfib), c) [Zn(apm)Cl2](14 tfib)
Parts of the crystal structure showcasing halogen-bonded chains in: a) [Cu(pm)Cl2](12 tfib)2, b) [Cu(apm)Cl2](12 tfib)2, c) [Zn(pm)Cl2](12 tfib), d) [Zn(apm)Cl2](12 tfib).
Parts of the 2D halogen-bonded networks in crystal structures of: a) [Cu(pm)Cl2]2(14 tfib)3, b) [Cu(pm)Cl2](13 tfib), c) [Cu(apm)Cl2](135 tfib)
The [Zn(pm)Cl2]2(14 tfib) cocrystal is the only cocrystal in our work where chloride ligands do not participate in halogen bonding, and therefore a trimeric discrete complex is formed via I⋅⋅⋅O halogen bonding, while [Zn(pm)Cl2](ipfb) is the only cocrystal with a monotopic halogen bond donor, which somewhat expectedly forms a dimeric discrete supramolecular complex via an I⋅⋅⋅Cl halogen bond.
As regards cocrystals with halogen-bonded chains, an interesting motif can be observed in the [Cu(pm)Cl2](12 tfib)2 cocrystal. Two 12 tfib molecules simultaneously bridge the same two adjacent acceptor molecules, thus connecting them into a linear chain. The CAr–H⋅⋅⋅O and CAr–H⋅⋅⋅Cl contacts connect the chains into a 2D network, while π⋅⋅⋅π stacking interactions between 12 tfib molecules connect the networks into 3D. The [Cu(apm)Cl2](12 tfib)2 cocrystal features two types of bridging 12 tfib molecules. One type forms tetramers via I⋅⋅⋅Cl halogen bonds, while the other type connects tetramers into a chain. A different motif can be observed in the [Zn(pm)Cl2](12 tfib) cocrystal where a simple chain is cooperatively formed by both I⋅⋅⋅Cl and I⋅⋅⋅O halogen bonding. Another unique motif is exhibited in the [Zn(apm)Cl2](12 tfib) cocrystal, where both chloride ligands are acceptor moieties, and both donor and acceptor molecules alternate between two orientations in the linear chain bridged by 12 tfib molecules. (Figure 5)
Cocrystals [Cu(pm)Cl2]2(14 tfib)3 and [Cu(apm)Cl2]2(14 tfib)3 are fairly similar both in stoichiometry and halogen-bonded motifs. In both, linear one-dimensional halogen-bonded chains are formed through chloride ligands that are approximately in plane with the pm or apm ligand. Additional I⋅⋅⋅Cl halogen bonds with the out-of-plane chloride ligand lead to the formation of large halogen-bonded network involving 6 donor and 6 acceptor molecules per one network “cell” (Figure 6). The network “cells” from one layer are filled in by elements from neighboring network layers. The network layers are connected into 3D via C−H⋅⋅⋅Cl, C−H⋅⋅⋅F and C−H⋅⋅⋅I contacts in the [Cu(pm)Cl2]2(14 tfib)3 cocrystal, and via C−H⋅⋅⋅Cl, C−H⋅⋅⋅F and C−H⋅⋅⋅O contacts in the [Cu(apm)Cl2]2(14 tfib)3 cocrystal. In the case of the [Cu(apm)Cl2](135 tfib)(CH3NO2) cocrystal, the supramolecular assembly can be described as an intrinsically complex 2D network driven both by hydrogen and halogen bonds.
Due to the plethora of different supramolecular architectures present in the prepared cocrystals, it is expected that, other than the fact that all zinc-containing cocrystals have lower decomposition points than pure Zn(pm)Cl2 or Zn(apm)Cl2, no sweeping trends can be readily observed in the thermal analysis data (Table 1). The two stoichiometrically equivalent and structurally very similar cocrystals with 135 tfib, [Cu(pm)Cl2](135 tfib) and [Zn(pm)Cl2](135 tfib), show a possible trend similar to pure metal complexes, in that the decomposition points of equivalent zinc compounds are higher than those of copper compounds. Additionally, for zinc complex cocrystals featuring discrete supramolecular architectures: [Zn(pm)Cl2](ipfb), [Zn(pm)Cl2](13 tfib), [Zn(pm)Cl2](135 tfib), [Zn(pm)Cl2]2(14 tfib) and [Zn(apm)Cl2](14 tfib), it can be seen that the thermal stabilities fall in the following order, 135 tfib >14tfib >13tfib > ipfb. It can also be seen that decomposition points for architecturally similar copper complex cocrystals, [Cu(pm)Cl2]2(14 tfib)3 and [Cu(apm)Cl2]2(14 tfib)3, are almost equal. While all these observations seem to imply that the biggest effects on cocrystal stability at similar supramolecular architectures are due to differences in the metal center or linking donor molecule used, as hypothesized and observed in our prior work, 15d a bigger data set of structurally similar enough or isostructural cocrystals would be needed to ascertain whether there is merit to these implications.
Compound |
td/°C |
|---|---|
[Cu(pm)Cl2](12 tfib)2 |
130.5 |
[Cu(pm)Cl2](13 tfib) |
104.2 |
[Cu(pm)Cl2](135 tfib) |
187.8 |
[Cu(pm)Cl2]2(14 tfib)3 |
157.1 |
[Cu(apm)Cl2](12 tfib)2 |
125.8 |
[Cu(apm)Cl2]2(14 tfib)3 |
156.5 |
[Cu(apm)Cl2](135 tfib)(CH3NO2) |
110.8 (solvent loss) 165.7 |
[Zn(pm)Cl2](ipfb) |
62.5 |
[Zn(pm)Cl2](12 tfib) |
129.2 |
[Zn(pm)Cl2](13 tfib) |
143.9 |
[Zn(pm)Cl2](135 tfib) |
211.9 |
[Zn(pm)Cl2]2(14 tfib) |
152.1 |
[Zn(apm)Cl2](12 tfib) |
106.0 |
[Zn(apm)Cl2](14 tfib) |
154.9 |
Cu(pm)Cl2 |
164.6 |
Cu(apm)Cl2 |
115.0 |
Zn(pm)Cl2 |
239.1 |
Zn(apm)Cl2 |
206.1 |
Conclusions
We have demonstrated that the combination of strategies for designing metal-containing halogen-bonded cocrystals can be effectively utilized and tailored through the selection of reliable halogen-bonding motifs. Our comprehensive study of 14 metal-organic halogen-bonded cocrystals has elucidated these motifs and their associated supramolecular architectures. From the observed dataset, a hierarchy of combined acceptor moieties can be established. Halogen bonds of the M−Cl⋅⋅⋅I type have once again proven to be reliable and robust interactions, present in 93 % of the cocrystals prepared. Conversely, the I⋅⋅⋅Omorpholinyl motif, although less frequently observed, tends to form shorter and more linear halogen bonds. From a supramolecular architecture perspective, this combination of acceptor moieties has proven to be both competitive in terms of the robustness of halogen-bonding motifs, and cooperative in terms of forming supramolecular complexes, chains, and networks. These synergies demonstrate the potential for assembly into a variety of distinct supramolecular architectures with broad variations. Such architectural diversity is likely due to the propensity of halogen-bonded solids to exhibit maximal dense packing, with higher-dimensional interconnections achieved through weak hydrogen bonds, hydrogen bond-like contacts, and notable π⋅⋅⋅π displaced stacking interactions. The results presented here could be valuable for further investigations into the reliability of halogen-bonding motifs in metal-organic solids, as well as for leveraging these solids in the preparation of functional materials with desired physicochemical properties characteristic of metal-containing compounds.
Experimental Section
Acceptor synthesis: Acceptors were prepared according to adapted literature procedures.21 First, a methanol solution of either pyridine-2-carbaldehyde (5 mmol, 475 μL for pm) or 2-acetylpyridine (5 mmol, 560 μL for apm) was prepared. To this solution, 4-(2-aminoethyl)morpholine (5 mmol, 655 μL) was added. The resultant solution was mildly heated within a beaker and was subsequently transferred to a round-bottom flask. Following this transfer, either copper(II) chloride dihydrate (5 mmol, 852.4 mg) for the copper complexes, or anhydrous zinc(II) chloride (5 mmol, 681.4 mg) for the zinc complexes, was dissolved in a minimal amount of ethanol and the ethanol solution added to the reaction mixture. The reaction mixture was refluxed for 3 hours. The obtained product was separated by vacuum filtration and used for mechanochemical and crystallization experiments without further purification. Compounds [Cu(pm)Cl2] and [Zn(apm)Cl2] were identified by a comparison of the bulk product with powder X-ray diffraction patterns of BARPIW and QAHRUO,21a, 21b respectively, whilst single crystals of [Zn(pm)Cl2] were obtained after cooling the reaction mixture to room temperature, and the crystal and molecular structure determined by single crystal X-ray diffraction was then used to ascertain bulk purity.
Cocrystal Screening: Initial cocrystal screening was performed by liquid-assisted grinding (LAG). A mixture of one of the coordination compounds and one of the halogen bond donors in a 1 : 1 stoichiometric ratio (mtotal ≈80 mg) with 10 μL of nitromethane was placed in a 15 mL stainless steel jar along with two stainless steel balls 7 mm in diameter. The mixture was then milled for 30 min in a Retsch MM200 Shaker Mill operating at 25 Hz milling frequency. The obtained powder samples were analyzed by powder X-ray diffraction (PXRD).
Preparation of single crystals: All cocrystals suitable for single-crystal X-ray diffraction experiments (SCXRD) were prepared by crystallization from solution. Coordination compounds and halogen bond donors were mixed in a 1 : 1 stoichiometric ratio and dissolved in an appropriate solvent or a mixture of solvents. The crystals were obtained by slow evaporation of the solvent at room temperature after a few days. Details on the solvents used, exact masses of co-formers and product morphology are given in Table S1 in the Supporting Information.
Preparation of cocrystal bulk: Synthesis of crystalline bulk product was performed by liquid-assisted grinding (LAG). A coordination compound was mixed with an appropriate halogen bond donor and a small amount of nitromethane in the stoichiometric ratio determined from the corresponding crystal structure. The mixture was placed in a 15 mL agate jar along with two agate balls 7 mm in diameter and then milled for 30 min in a Retsch MM200 Shaker Mill operating at 25 Hz milling frequency. The obtained powder samples were analyzed by powder X-ray diffraction (PXRD), thermogravimetric analysis (TG) and differential scanning calorimetry (DSC). Details for bulk-synthesis LAG experiments are given in Table S2 in the Supporting Information.
Thermal analysis: TG and DSC measurements were performed on a Mettler-Toledo TG/DSC 3+ module. The samples were placed in alumina pans (70 μL) and heated in flowing oxygen (50 mL min−1) from 25 °C to 700 °C at a rate of 10 °C min−1. Data collection and analysis were performed using the program package STARe Evaluation Software 17.00.23
Powder X-ray diffraction (PXRD): PXRD experiments were performed either on a Malvern PANalytical Empyrean X-ray diffractometer at 40 mA and 45 kV or on a Malvern PANalytical Aeris X-ray diffractometer at 15 mA and 40 kV, both utilizing CuKα (λ=1.54056 Å) radiation. The scattered intensities were measured with line (1D) detectors in the angular range from 5° to 40° (2θ) with interpolated step size of 0.0066° with time per step of 9.027 s for scans conducted on Empyrean or 0.0054° and 8.670 s on Aeris diffractometer, respectively. Data analysis was performed using the program Data Viewer.24
Single crystal X-ray diffraction (SCXRD): Crystal and molecular structures of the prepared cocrystals were determined by single crystal X-ray diffraction. Details of data collection and crystal structure refinement are listed in Tables S1–S7 in SI. Diffraction measurements were made on a Rigaku Synergy XtaLAB X-ray diffractometer with graphite-monochromated MoKα (λ= 0.71073 Å) radiation. The data sets were collected using the ω scan mode over the 2θ range up to 64°. Data was collected at room temperature (295 K), with an exception for the [Zn(pm)Cl2](ipfb) cocrystal for which data was collected at 170 K. The CrysAlisPro program package was employed for data collection, cell refinement, and data reduction.25 The structures were solved by direct methods and refined using the SHELXS, SHELXT, and SHELXL programs, respectively.26 Structural refinement was performed on F2 using all data. Hydrogen atoms were placed in calculated positions and treated as riding on their parent atoms. All calculations were performed using the WINGX or Olex2 crystallographic suite of programs.27, 28 Molecular structures of compounds and their molecular packing projections were prepared using Mercury 2023.3.0.29
Supporting Information Summary
The data supporting this article (experimental procedures, TG-DSC thermograms, PXRD patterns, crystal data and ORTEP representations of obtained structures) have been included as part of the Supporting Information. Deposition Numbers CCDC 2411944 (for [Cu(pm)Cl2](135 tfib)), 2411945 (for [Zn(pm)Cl2]2(14 tfib)), 2411946 (for [Zn(pm)Cl2](ipfb)), 2411947 (for [Cu(apm)Cl2](12 tfib)2), 2411948 (for [Cu(pm)Cl2](12 tfib)2), 2411949 (for [Zn(pm)Cl2](135 tfib)), 2411950 (for [Zn(apm)Cl2](12 tfib)), 2411951 (for [Cu(apm)Cl2](135 tfib)(CH3NO2)), 2411952 (for [Zn(pm)Cl2](13 tfib)), 2411953 (for [Zn(apm)Cl2](14 tfib)), 2411954 (for [Cu(pm)Cl2]2(14 tfib)3), 2411955 (for [Cu(pm)Cl2](13 tfib)), 2411956 (for [Zn(pm)Cl2](12 tfib)), 2411957 (for Zn(pm)Cl2) and 2411958 (for [Cu(apm)Cl2]2(14 tfib)3) contain the supplementary crystallographic data for this paper. These data are provided free of charge by the joint Cambridge Crystallographic Data Centre and Fachinformationszentrum Karlsruhe via https://www.ccdc.cam.ac.uk/data request/cif.
Acknowledgments
This research was funded by the Croatian Science Foundation under the research project IP-2019-04-1868. Additionally, we acknowledge support of the project CIuK cofinanced through the European Regional Development Fund-Competitiveness and Cohesion Operational Programme (Grant KK.01.1.1.02.0016). Open Access publishing facilitated by $WOA_OO_ELIGIBLE_INSTITUTION, as part of the Wiley - National and University Library in Zagreb Consortium Croatian Academic and Research Libraries Consortium agreement.
Conflict of Interests
The authors declare no conflict of interest.
Open Research
Data Availability Statement
The data that support the findings of this study are available in the supplementary material of this article.
