Syntheses and properties of two-dimensional charged nonlinear optical chromophores incorporating redox-switchable cis-tetraammineruthenium(II) centers

In this article, we describe a series of new complex salts in which electron-donating cis-{RuII(NH3)4}2+ centers are connected to two electron-accepting N-methyl/aryl-pyridinium groups. These V-shaped complexes contain either monodentate 4,4'- bipyridyl-derived ligands or related chelates based on 2,2':4,4?: 4',4?-quaterpyridyl and have been characterized by using various techniques including electronic absorption spectroscopy and cyclic voltammetry. Molecular quadratic nonlinear optical (NLO) responses ß have been determined by using hyper-Rayleigh scattering at 800 nm and also via Stark (electroabsorption) spectroscopic studies on the intense, visible d ? p* metal-to-ligand charge-transfer bands. These experiments reveal that these dipolar pseudo-C2v chromophores exhibit two substantial components of the ß tensor, ßzzz and ßzyy, with the difference between them being most marked for the nonchelated systems. Time-dependent density-functional theory and finite field calculations serve to further illuminate the electronic structures and associated linear and NLO properties of the new chromophoric salts.