Ab-initio DFT study on the mechanism of the electron conductivity of molecular devices composed of indium atoms and C&z.dbd;O carbonyl compounds

Ab-initio DFT and configuration interaction (CI) calculations have been carried out for indium–carbonyl compounds, such as acetone–In (Ac–In), 1,8-naphthalic anhydride–In (In₂NA) and 3,4,9,10-perylenetetracarboxylic dianhydride–indium (In₄PTCDA), in order to shed light on the mechanism of electronic conductivity in the molecular devices. It was found that the electronic state of these complexes at the ground state is composed of ion-pair states expressed approximately by (Ac^δ−)(In^δ+), (In₂)^δ+(NA)^δ− and (In₄)^δ+(PTCDA)^δ−, respectively. On the other hand, the interaction at the first excited state was changed to a van der Waals interaction. Namely, the electron returned again to the In atom by electronic excitation. The second excited state is attributed to internal excitation within the carbonyl anion, while the charge on the indium was close to neutral. The mechanism of the electronic conductivity was discussed on the basis of theoretical results.