Document Type : Regular Article
Department of Chemistry, Faculty of Science, University of Sistan and Baluchestan, Zahedan, Iran
University of sistan and baluchestan
The quantum chemical calculations were performed to investigate the interplay between the anion˗π and intramolecular hydrogen bond (IMHB) interactions in the various complexes of 1,3,5-triamino-2,4,6-trinitrobenzene (ANB) with Hˉ, Fˉ, Clˉ and Brˉ anions. For better understanding the cooperative effects, the parent molecules (ANB) and the corresponding complexes of 1,3,5˗trinitrobenzene with the mentioned anions are also considered, as a set of the reference points. In this regard, the IMHB and anion˗π interactions are comprehensively analyzed by energetic, geometrical, spectroscopic and topological descriptors. It was found that the coexistence of the anion˗π and IMHB increases the strength of both interactions. Furthermore, the influences of the anion-π and IMHB interactions on the significance of the π˗electron delocalization (π˗ED) of the resonance assisted hydrogen bond (RAHB) units and the aromaticity of the benzene ring are evaluated by the harmonic oscillator model of aromaticity (HOMA), as a geometry based index. According to the HOMA values, we concluded that the coexistence of the mentioned interactions decreases the aromaticity of benzene ring and increases the π˗ED of RAHB units. Finally, the strength of the non-covalent interactions and the significance of π˗ED and aromaticity strongly depend on type of the anion.