Quantum mechanical interpretation of photodecomposition of di-tertiarybutyl mercury

Abstract

The quantum mechanical “Extended Hückel Theory” is applied to the electronic structure calculation of compounds containing heavy elements like mercury. Di-tertiarybutyl mercury, which deposits elementary mercury when irradiated, shows an absorption band at 242 nm (ε = 4070). A quantitative discussion of the molecular orbitals calculated by the Extended Hückel Method, using a basis set of s-, p- and d-functions was made. The calculations indicate that the absorption band at 242 nm is attributed to a charge transfer between the Highest Occupied Molecular Orbital (HOMO) and the Lowest Occupied Molecular Orbital (LUMO). It was found to be a symmetry allowed transition and its calculated energy is in good agreement with that observed. A quantitative discussion of the coefficients of different atomic orbitals of both the HOMO- and LUMO-calculated wave functions and calculation of bond orders between Hg- and C-atoms for the ground and first excited states explained reasonably, that it is this transition which is responsible for the decomposition of di-tertiarybutyl mercury with the liberation of elementary mercury.