Theoretical Study on a Novel Series of Fullerene-Containing Organometallics Fe(η5-C55X5)2(X = CH, N, B) and Their Large Third-Order Nonlinear Optical Properties.

Geometry structures, electronic spectra, and third-order nonlinear optical (NLO) properties of Fe(η 5-C 55X 5) 2(X = CH, N, B) have first been investigated by time-dependent density functional theory. We analyzed the intramolecular interactions between ferrocene and the C 50moiety. The calculated electronic absorption spectrum indicates that the short wavelength transitions are ascribed to the C 50moiety mixed charge transfer transition of ferrocene itself, while the low energy excitation transitions are ascribed to the unique charge transfer transition from ferrocene to C 50moiety in these systems. The third-order polarizability γ values based on sum of states (SOS) method show that this class of ferrocene/fullerene hybrid molecule possesses a remarkably large third-order NLO response, especially for Fe(η 5-C 55B 5) 2with the static third-order polarizability (γ av) computed to be −10410 × 10 −36esu and the intrinsic second hypepolarizability to be 0.250. Thus, these complexes have the potential to be used for excellent third-order nonlinear optical materials. Analysis of the major contributions to the γ avvalue suggest that the charge transfer from ferrocene to C 50moiety along the z-axis (through Fe atom and the centers of two hybrid fullerenes) play the key role in the NLO response. Furthermore, boron substitution is an effective way of enhancing the optical nonlinearity compared to CH and N substitution, owing to smaller energy gap and better conjugation through the whole molecule. [ABSTRACT FROM AUTHOR]