Compromise Between Conjugation Length and Charge-Transfer in Nonlinear Optical Monocyclopentadienyliron Complexes

Abstract

We study the conjugation-length dependence of the first hyperpolarizability in a series of complexes of general formula [FeCp(P_P)(NC{SC4H2}nNO2)][PF6] (P_P=dppe, (+)-diop; n=1 3). Spectroscopic data are used in order to evaluate the effect of the type of phosphine coligand and the length of the conjugated ligand on the second-order NLO response of the complexes, which is compared to the observations for the p-benzonitrile analogues. Cyclic voltammetry is also used as a tool for a better understanding of the electronic factors responsible for the NLO behaviour of the compounds studied in this work.