A current challenge in materials chemistry and engineering is to afford a specific macromolecular or molecular property by tuning a molecular structure through deliberate chemical changes. Materials that display nonlinear optical (NLO) activity are of fundamental interest and technological use for a number of photonic applications, including optical switching, communications, and data storage and retrieval. Consequently, we are synthesizing and characterizing new Pt(II) dimine dithiolate or catecholate chromophores possessing bulky electron-donating or electron-withdrawing sulfur or oxygen ligands to better understand the relationships between structure and optical properties.
Three compounds from our research activites are particulary interesting and were evaluated for their optical properties inlcuding NLO activty. A number of important conclusions can be drawn from our data, given the strong correlation between the metal chromophore electronic structure and the second-order polarizability (see Figures). First, these platinum(II) chromophores possess solvent dependent second-order polarizability responses, underlying the importance of both molecular structure and the influence of the solvent medium. Second, m*b for inorganic chromophores can be optimized and platinum chromophore III exhibits one of the largest negative second-order polarizabilities measured for a metal complex. Third, these data for inorganic chromophores conform to the two-state model which relates the molecular structure and the second-order polarizability. Fourth, as suggested previously for organic chromophores, this present study also proposes that NLO spectroscopy may be a new analytical tool for characterizing the electronic structure of inorganic complexes. Finally, our results further substantiate the use of the two-state model and its concepts for the design, optimization, and study of new NLO chromophores.