Synthesis, physical characterization, thermal studies, biological activities and DFT computations on the molecular structure and vibrational spectra of [C7H12N2]2Bi2Br10·4H2O compound

Abstract

A new bismuth (III) complex, 2,4-diammonium toluene decabromodibismuthate (III) tetra-hydrate, was synthesized and its structure was determined. Bismuth complex crystallizes in the monoclinic system with the P21/c space group. The cohesion between [C7H12N2]2+ cations, [Bi2Cl10]4- anions and water molecules is ensured by N–H⋯Br, N–H … Ow and Ow-H…Br hydrogen bonds that build a three-dimensional network. The NMR spectra shows the presence of one organic group C7H12N2, which is in agreement with the XRD structure. The optimized molecular structure and vibrational frequencies were calculated by the Density Functional Theory (DFT) method using the B3LYP function with the LanL2DZ basis set. On the basis of the comparison between calculated and experimental results, assignments of the fundamental vibrational modes are discussed. Besides, the electronic properties HOMO and LUMO energies were measured by TD-DFT approach. Their values indicate that the energy gap reflect the chemical stability and biological activity of this molecule. In this regard, the biological study focused on the antioxidant and antibacterial activities of bismuth (III) complex and its organic molecule have been investigated. These results showed that synthesized compound exhibit significant antioxidant and antibacterial activities. Moreover, the thermal analysis of the title compound between 200 and 500 ​K have been occurred and revealed one phase transition at 360 ​K. Furthermore, to discuss the mechanism of this phase transition in this material, a dielectric study of the title compound has been effectuated.