Theoretical investigation of charge transfer to solvent in photoexcited iodide–acetonitrile clusters

Photoexcitation of the iodide–acetonitrile complex leading to charge-transfer-to-solvent precursor states has been investigated with electronic structure theory calculations. The resulting vertical excitation energies are in good agreement with experimental results. The picture that emerges from the calculations is that, upon photoexcitation, an electron is transferred from one of the iodide valence p orbitals to the acetonitrile molecule, where it is stabilized by interactions with the acetonitrile dipole and the electrophilic hydrogen atoms of the methyl group. A similar picture applies to the photoexcitation of iodide–water clusters, but charge transfer to solvent appears much more obvious for iodide–acetonitrile clusters.