Organometallic Acetylide Complexes for Nonlinear Optics: Revealing their behavior as possible molecular switching devices

The development of new organometallic compounds with second order nonlinear optical (SONLO) properties has a great interest nowadays due to their possible applications in optical devices for communications, computation and data storage. [1] The concept of molecular switching in SONLO is based in the idea of commuting between different molecular states will infer a different response amplitude for the first hyperpolarizibility of the compounds. [2] This can be accomplished either by external chemical, optical or electrochemical stimulus. In the case of organometallic complexes the modification in the oxidation state of the metal center by electrochemical means is the most easy and straightforward method to evaluate the molecular switching properties of a molecule. [3] The present study pertains the synthesis and characterization of iron (II), ruthenium (II) and nickel(II) thiophenic monocyclopentadienyl acetylide complexes, which were characterized by the usual spectroscopic techniques (NMR, Uv-Vis, FTIR) and electrochemically by cyclic voltammetry. The SONLO proprieties were calculated by DFT calculations and later measured by Hyper Rayleigh Scattering. In order to evaluate their switching properties, electrochemical and DFT data were correlated. Results prove that, despite some stability problems, the complexes synthesized possess good NLO switching properties. Of all the complexes synthesized, iron (II) complexes are the most feasible for such applications