Structural, theoretic and spectroscopic analysis of 2-methyl-5-nitroaniline salts with various inorganic acids

Abstract

Crystal structures of six new salts of 2‐methyl‐5‐nitroaniline with inorganic acids [(H2Me5NA)Br, (H2Me5NA)I, (H2Me5NA)NO3, (H2Me5NA)Cl, (H2Me5NA)HSO4 and (H2Me5NA)I3·0.5H2O] are determined by single‐crystal X‐ray diffraction. The most important hydrogen‐bonding patterns are formed by the ammonio group and respective anions composing 1D or 2D networks. The patterns are analysed using the graph‐set approach and mathematical interrelations between graph‐set descriptors are shown for comparative purposes. Analysis of IR spectra enables the strength of hydrogen bonds in the crystals to be assessed. The frequency of N—H and O—H stretching vibrations and NH3 group libration indicates that the strongest hydrogen bonds are present in (H2Me5NA)HSO4, whereas the weakest ones occur in (H2Me5NA)I3·0.5H2O. Hirshfeld surface analysis reveals that apart from obvious N—H…anion hydrogen bonds, the molecules are also connected to each other by exclusive C—H…ONO2 interactions. The opposite occurs in the crystal structure of 2‐methyl‐4‐nitroaniline salts, where a variety of ONO2…π(N)NO2 non‐hydrogen bonding interactions are observed.

Structural and theoretical analysis of 2-chloro-4-nitroaniline and 2-methyl-6-nitroaniline salts

“…As a result, the lowest repulsions between the groups are realized. Such an atomic arrangement was also found for the structure of the global minimum of the H2m5na + ion (Medviediev & Daszkiewicz, 2019).…”

“…In the crystal structures of 1 and 2, the nitro group is rotated around the C-N bond by a few degrees, but the position of the ammonium group is far from the global minimum. When the NO 2 group reaches an orientation perpendicular to the arene ring, the H2Cl4na + ion is at a rotational barrier of 4.60 kcal mol À1 and is lower than values reported previously for other nitroanilines (Daszkiewicz, 2014b;Chen & Chen, 2001Medviediev & Daszkiewicz, 2019). In the case of the ammonium group, the barrier is only 0.13 kcal mol À1 at the level of theory used here.…”

“…Thus, the ammonium group forms charge-assisted hydrogen bonds, which play a basic role in the molecular self-assembly and crystal growth of nitroanilinium salts (Daszkiewicz & Mielcarek, 2016;Dinesh et al, 2008;Masse & Levy, 1991;Azumi et al, 1996;Arjunan et al, 2012;Lemmerer & Billing, 2006;Daszkiewicz, 2013aDaszkiewicz, , 2014aDaszkiewicz, ,b, 2015. In the nitroanilines containing only one ammonium group, hydrogen-bonding patterns along three dimensions are not observed, but layer or ladder patterns are formed (Medviediev et al, 2020a;Medviediev & Daszkiewicz, 2019. This fact is probably associated with the molecular structures of such nitroanilines.…”

“…2). Since the literature data (Chen & Chen, 2001 and our previous studies on 2methyl-5-nitroanilinium cations (Medviediev & Daszkiewicz, 2019) showed that the position of the NO 2 group had the greatest impact on the potential energy, the first scan concerned only the nitro group. The rotation step was 1 in the range from À90 to 90 .…”

“…Thus, a juxtaposition of the molecules forming hydrogen-bonding patterns can be expressed as a summation of particular elementary graph-set descriptors. Using mathematical operations on the graph-set descriptors gives an opportunity to investigate similarities and differences among the patterns in various crystal structures (Medviediev & Daszkiewicz, 2019;Daszkiewicz, 2013a). In addition, this method was applied successfully in the analysis of hydrogen-bonding patterns during phase transition (Rejnhardt et al, 2019(Rejnhardt et al, , 2020Medviediev et al, 2020a).…”