The nonlinear optical (NLO) properties of a series of sandwich complexes which are coordinated by 7,10,12 vertexes ferradicarbaboranes and 1,2,4,5-Me₄C₆H₂ (dur1), 1,2,3,4-Me₄C₅H (dur₂) were investigated by density functional theory (DFT) CAM-B3LYP method. The results indicate that the vertexes of ferradicarbaboranes and the substitution position of nitryl both affect the molecular geometry and then affect the NLO properties of molecules. The dipole moment and the polarizability are both enhanced with the increase of the vertexes of ferradicarbaboranes. The HOMO-LUMO energy gaps of molecules with 10 vertexes ferradicarbaboranes are relatively smaller, so the first hyperpolarizabilities (β_tot) values of them are larger than the molecules with 12 and 7 vertexes ferradicarbaboranes. When replacing of the atom H of Fe(II) para-position by nitro, the β_tot values of molecules are larger than the non-substitution molecules; however, the atom H of Fe(II) ortho-position is substituted by nitro, the β_tot values of molecules are smaller than the non-substitution molecules. In the studied molecules, the carboranes can act as either electronic donor or acceptor.

Key words: ferradicarbollide sandwich complexes, polarizability, NLO property, DFT