Density functional theory calculations on η5-monocyclopentadienylnitrilecobalt complexes concerning their second-order nonlinear optical properties

Density functional theory calculations were performed to determine first static hyperpolarizabilities (β) of model complexes [CoCp(H2PCH2CH2PH2)(p-NCC6H4R)]2+. The results show that these complexes have low hyperpolarizabilities which are due to weak electronic coupling between the organometallic fragment and the nitrile ligands. It was shown that in these complexes the electronic excitation responsible for second-order non-linear optical response is a ligand to metal charge transfer. The results also show the inverse relationship between the first hyperpolarizability and the corresponding electronic transfer energy gaps.