Mutual effects of the cation-π, anion-π and intramolecular hydrogen bond in the various complexes of 1,3,5-triamino-2,4,6-trinitrobenzene with some cations (Li+, Na+, K+, Mg2+, Ca2+) and anions (F˗, Cl˗, Br˗)

Abstract

A comprehensive theoretical investigation of the mutual effects of the cation-π, anion-π, and intramolecular hydrogen bond (IMHB) interactions in the various ternary complexes of 1,3,5-triamino-2,4,6-trinitrobenzene (ANB) with anions (A: F˗, Cl˗, Br˗) and cations (M: Li+, Na+, K+, Mg2+, Ca2+) were carried out. The energetic, geometrical, topological, and molecular orbital descriptors are employed to estimate the strength of the mentioned non-covalent interactions and their results were compared with the corresponding data of the ANB⋯M, ANB⋯A and A⋯Bz⋯M complexes, as a set of reference points. The results indicate that the presence of resonance-assisted hydrogen bond (RAHB) units decreases the strength of cation-π interaction while for anion-π interactions, the reverse process is observed. On the other hand, the RAHB units reduce the binding energies of the ternary complexes and cooperative effects between the cation-π and anion-π interactions, with respect to the A⋯Bz⋯M complexes. Furthermore, the coexistence of cation-π and anion-π interactions modulates their effects on the strength of IMHB. Finally, the harmonic oscillator model of aromaticity (HOMA) indicator was applied to analyze the influences of the mentioned interactions on the significance of the π-electron delocalization (π-ED) of the RAHB units and aromaticity of the benzene ring. It was found that the coexistence of cation-π and anion-π interactions effectively change the π˗ED and aromaticity.