Reversible Redox Switching of First Hyperpolarizability of β Metallorganic Complexes

Abstract

The concept of molecular switches has garnered enormous interest because of the vital role of these switches as components in molecular electronic/photonic devices, signal transmission and optical communication. Compounds possessing switchable(on/off) nonlinear optical (NLO) properties can serve as important building blocks in the formation of molecular devices in the optoelectronic field. Alteration of the electronic charge distribution in the components of an NLO-active molecule can substantially change the second order NLO response (which is quantified by first hyperpolarizability, and#946;) and can be exploited for constructing molecular switches. For designing an effective switch, a molecule must be stable in two or more forms and must exhibit significantly contrasting and#946; in each form. Among various approaches that use external stimuli to change the electronic properties and thereby and#946;, the one that utilizes the reversible redox properties of metal atoms/ligands in metallorganic complexes is preferred, due to minimal structural distortion. Multivalent (MV) metals can be stabilized in different oxidation states and their donor/acceptor properties are changed accordingly. This in turn is expected to change and#946; significantly. In this thesis, I have investigated the redox switching of and#946; of various metallorganic complexes containing Ru, Re and Fe centers by in-situ second harmonic light scattering (SHLS). The experimental results have been rationalized by DFT and TDDFT calculations of linear and nonlinear electronic properties. In chapter 1, I have introduced the second order nonlinear optical response of metallorganic complexes, various factors influencing and#946; and different strategies used to increase the and#946; value of molecules and materials. The basic principle of SHLS experiments has also been described in this chapter. The scope and motivation of this work have been presented at the end of this chapter...