First hyperpolarizabilities of transition metal sesquifulvalene complexes

The static first hyperpolarizabilities of some typical transition metal sesquifulvalene complexes have been assessed within the framework of the density functional theory (DFT). The molecular orbital analyses illuminate that the molecular structural factors predominate the characteristics of frontier molecular orbitals, linear electronic absorption spectra and static first hyperpolarizabilities, in a great extent. The complexations of sesquifulvalene derivatives (C5H4-π-bridge-C7H6) with the (η5-C5H5)Fe+-, (η5-C5H5)Ru+- and (CO)3Mn+- monocations gain mononuclear ferrocenyl complexes and result in longer distances and larger charge separations between the electronic donor and acceptor, and narrower HOMO-LUMO gaps. These changes in return enhance the electric dipole moment and static electric first hyperpolarizability. Nevertheless, the subsequent integrations of mononuclear ferrocenyl sesquifulvalene monocations with the (CO)3Cr- group reduce static first hyperpolarizability for the complexes with the ethylene or acetylene spacer but increase static first hyperpolarizability for the complexes with the benzene bridge. Additionally, the complexations of mononuclear ferrocenyl sesquifulvalene monocations with the (η5-C5H5)Ru+- monocation result in the considerable reducement of static first hyperpolarizability. These differences have been well interpreted in terms of an integration of molecular geometry with electronic structure.