A theoretical study of tetrabutylammonium [bis(1,3-dithiole-2-thione-4,5-dithiolato)bismuthate], [NBu4][Bi(dmit)2]: infrared spectrum in the solid state and solvation effects on the molecular geometry

A theoretical study of tetrabutylammonium [bis(1,3-dithiole-2-thione-4,5-dithiolato)bismuthate], [NBu4][Bi(dmit)2] is reported. The vibrational spectrum and the molecular orbitals were calculated at the Hartree–Fock level of theory with the pseudo-potential SBKJC for Bi and a basis set of 6-31G or 6-31G(d,p) for the other atoms. The molecular geometry of the anion, [Bi(dmit)2]−, was optimised with the same level of theory and basis sets, but utilising the polarisable continuum method, for simulation of acetone and benzene media. Molecular geometries of solvated and solid-state species are compared: solvation effects are discussed in terms of anisotropy or isotropy of the media. Analysis of the molecular orbitals allowed a qualitative description of the anion–anion intermolecular interactions.