Optical properties and ab initio study on the hybrid organic–inorganic material [(CH3)2NH2]3[BiI6]

The tri (dimetylammonium) hexa-iodobismuthate of general formula [(CH3)2NH2]3[BiI6] is an organic–inorganic hybrid material. The crystal lattice is composed of discrete [BiI6] anions surrounded by dimethylamine cations. The X-ray diffraction pattern was obtained and indexed on the basis of rhombohedra unit cell with the R  3¯ space group. Room temperature IR and Raman spectra of the title compound were recorded and analyzed. Semi-empirical Parameter Model three (PM3) method as well as density functional theory (DFT) calculations have been performed to derive the equilibrium geometry, vibrational wave numbers and a prediction of IR and Raman spectral activities. In this compound the bands corresponding to the cation vibrational modes show that the symmetry of these cations is distorted and they are strongly hydrogen bonded to the respective anions. The frontier molecular orbital and the energy gap between the highest occupied molecular orbital (HOMO) and the lowest un-occupied molecular orbital (LUMO) were calculated with time dependent density functional theory (TD-DFT). The results show good consistent with the experiment and confirm the contribution of metal orbital to the HOMO–LUMO boundary.