Elementary Graph-Set Descriptors in Crystal Structure Comparison of 2-Methyl-4-Nitroanilinium Hexachloridostannate(IV), Bromide and Two Noncentrosymmertic Chlorides. X-Ray, Vibrational and Theoretical Studies

Abstract

Crystal structures of two polymorphs of [H2m4na]Cl (1α,1β) and (H2m4na) 2 SnCl 6 •H 2 O (2), where 2m4na = 2methyl-4-nitroaniline are shown and comparison of these crystal structures with the bromide salt reported earlier is presented. In all the presented crystal structures, alternatively arranged cations and anions form chain and ring hydrogen-bonding patterns of weak unconventional N−H•••Cl hydrogen bonds. Interrelations among the elementary graph-set descriptors and descriptors of the hydrogen-bonding patterns are presented. Nonhydrogen bonding interactions between the nitro groups are also described using graph-set descriptors. Comparison of the experimental, also for deuterated 1α polymorph, and theoretical, for H2m4na + ion with B3LYP/6-31G(d,p), spectra showed good agreement among the frequencies due to very weak interactions existing in studied compounds. Detailed analysis of the spectra revealed that the interaction between adjacent −NO 2 groups in 1α is stronger than the other types involving the nitro group. The bands were assigned on the basis of theoretical calculations of vibrational frequencies for H2m4na + ion and PED analysis.

Comparison of hydrogen bonds and diverse weak interactions of the nitro group in 2-methyl-4-nitroanilinium nitrate, bisulfate and two hexafluoridosilicates: elementary graph-set approach

“…These descriptors can be summarized resulting in a descriptor for the hydrogen-bonding pattern and likewise the molecules that create hydrogen bonds. In such an approach, the creation of a complex pattern is expressed by mathematical operations among elementary graph-set descriptors and also the descriptors of hydrogen-bonding patterns (Daszkiewicz, 2013b). In the case of the ammonio group, a set of elementary graph-set descriptors were recently reported in order to analyze the hydrogen-bonding patterns in 2-methyl-4-nitro-anilinium chloride, G NH3 = {3E 0 1 (1); 3E 0 2 (3)} (Daszkiewicz, 2013b).…”

“…In such an approach, the creation of a complex pattern is expressed by mathematical operations among elementary graph-set descriptors and also the descriptors of hydrogen-bonding patterns (Daszkiewicz, 2013b). In the case of the ammonio group, a set of elementary graph-set descriptors were recently reported in order to analyze the hydrogen-bonding patterns in 2-methyl-4-nitro-anilinium chloride, G NH3 = {3E 0 1 (1); 3E 0 2 (3)} (Daszkiewicz, 2013b). Similarly, the following elementary graph-set descriptors for atomic pathways in nitrate, bisulfate and hexafluoridosilicate anions are…”

“…So, we describe a comparison of the patterns based on the isotopology of the anions and branching as the issues inducing similarities and differences of a twodimensional hydrogen-bonding network. The patterns found in the studied crystals were also compared wih that described earlier for (H2m4na)Cl (Daszkiewicz, 2013b). The topological analysis was carried out using mathematical operations on elementary graph-set descriptors.…”

“…A survey on the Cambridge Structural Database shows only nine crystal structures containing the H2m4na + ion (Azumi et al, 1996;Arjunan et al, 2012;Daszkiewicz, 2013b;Dinesh et al, 2008;Lemmerer & Billing, 2006;Masse & Levy, 1991). Overall, the common feature of all these structures are two ISSN 2052-5206 # 2016 International Union of Crystallography layers, where the basic one contains a complex network of hydrogen-bonding interactions constructed by anions and the ammonio group.…”

“…Since no stronger interactions are formed in this layer and the nature of interactions of the nitro group is rather weak, they appear to be important in a molecular self-assembly process along the crystallographic direction associated with the axis running through the ammonio and nitro groups. For instance, it was observed for the phase of (H2m4na)Cl that the largest face of the plate crystals is parallel to the layer of (N) NO2 Á Á ÁO NO2 interactions formed by perpendicularly arranged nitro groups (Daszkiewicz, 2013b). However, it is worth noting that usually the interaction energy of hydrogen bonds formed by the positively charged ammonio group and anions is significantly greater than the aforementioned C-HÁ Á ÁO or -type interactions.…”