Single-Crystal-to-Single-Crystal Transformation and Catalytic Properties of New Hybrid Perhalidometallates

Abstract

Two new organic–inorganic salts of perhalidometallates with protonated organic amine cations have been synthesized and characterized by X-ray diffraction and thermal analysis. (CHBMAH2)ZnBr4·3/2H2O 1 and (CHBMAH2)ZnCl4 4 [(CHBMAH2)2+: 1,3-cyclohexanebis(methylammonium)] were obtained in single-crystal form. The crystal packing in all of the obtained compounds is governed by the formation of various non-covalent intermolecular forces between tetrahalidometallate anions and organic cations, assisted by water molecules in the hydrates. Hirshfeld surface analysis denotes that the most important contributions to the crystal packing are X···H/H···X (X: Cl, Br, I) and H···H interactions. Interestingly, the compound 1,3-cyclohexanebis(methylammonium)tetrachloridozincate (II) dihydrate, (CHBMAH2)ZnCl4·2H2O 2, undergoes thermally-triggered single-crystal-to-single-crystal (SCSC) transformation upon dehydration to produce a supramolecular solid compound, 1,3-cyclohexanebis(methylammonium) tetrachloridozincate (II), (CHBMAH2)ZnCl4 4. The SCSC transformation causes changes in the lattice parameters and a structural rearrangement. Furthermore, the catalytic properties of (CHBMAH2)ZnCl4·2H2O 2 and (CHBMAH2)CdI4·2H2O 3 have been explored in the acetalization process using various uncommon alcohols, beyond methanol or ethanol, for the first time in the literature, with outstanding results, and opening the door to the formation of alternative acetals.

Hirshfeld Surface Analysis for Investigation of Intermolecular Interaction of Molecular Crystals

“…Nowadays, Hirshfeld surface analysis can be performed by loading CIF files obtained from crystal structure analysis into available programs, whose key features may be visualization and quantitation of various types of intermolecular interactions. Recently, many papers published in MDPI's journals have used Hirshfeld surface analysis to discuss various types of intermolecular interactions [2]- [41].…”

“…Even then, it is the intermolecular interactions that bind the building blocks together. Moyano In the analysis, which was proposed in 1977 [41] and recently used to review actual usage in single molecule magnets [42], a space is defined in which the International Journal of Organic Chemistry electron density of the molecule of interest is greater than the surrounding electron density. This space wraps the outer region, similar to a cover, and is called the 'Hirshfeld surface'.…”

“…Furthermore, whereas van der Waals surfaces defined by known van der Waals radii are only defined by the molecule itself, Hirshfeld surfaces are defined by the proximity of the molecule itself and its nearest molecular neighbors, as mentioned in Spackman's review [43]. Please refer to [41,43] for It is necessary to position the hydrogen atoms precisely and to ensure that the bonding distances to the hydrogen atoms are realistic values. Although hydrogen positions determined using X-ray crystallography may be always biased, Hirshfeld surface analysis is usually used for intermolecular interaction in crystals (not in optimized structures based on DFT calculations).…”

Crystal engineering and structural diversity of 2-aminopyridinium hypodiphosphates obtained by crystallization and dehydration

“…As a result of dehydration, crystals with a very similar crystal structure to that of the hydrate may be formed 32,33 or this process may be destructive and give rise to crystals with quite different crystal architectures. 34 Therefore, an understanding of the nature of the dehydration process, and its mechanism and structural effects, in particular, whether it occurs gradually or continuously, along with the factors that influence it, is needed. In 1996, S. Petit and G. Coquerel 35 presented a classification scheme for the dehydration of organic compounds.…”