TUNING THE ELECTRONIC PROPERTIES AND PACKING OF BENZONITRILEIRON(II) CENTRES THROUGH MOLECULAR DESIGN OF COLIGANDS

Abstract

There has been much interest in the nonlinear optical (NLO) properties of organometallic complexes in the last two decades. The most efficient NLO-active complexes are push-pull systems with an electron donor group linked by a p- conjugated bridge to an electron acceptor group. Our studies on push-pull type complexes have focused on metal s-nitriles, for which the second-order NLO responses have been determined [1,2] and prompted us to extend the studies in order to fine tune the NLO properties through some structural changes, namely to assess the importance of coligands in the donor metal coordination sphere [3]. Since macroscopic properties arise from the properties of the individual molecules, the ability to predict and control the assembly of molecular and ionic species into ordered networks, in order to optimise the molecular response, has become an important target in this field. In this communication we present a systematic study on the family of complexes [Fe(h5-L)(L’)(L’’)(p-system)] +(L=Cyclopentadienyl or Indenyl; L’,L’’= CO, P(OC6H5)3, P(C6H5)3, DPPE, etc; p-system= aromatic nitriles) where the organometallic donor has been enriched or depleted by changing the ligands L, L’ and L’’ and the p- system has been extended in order to maximise the delocalisation on the ligand. Since a small change in the molecular structure may lead to dramatic changes on the crystal structure, we have studied the influence of the molecular structural changes in the 3D crystal packing. This study may give some contribution to understand the relationships between structure and NLO responses.