Syntheses and Properties of Two-Dimensional Charged Nonlinear Optical Chromophores Incorporating Redox-Switchable cis-Tetraammineruthenium(ll)Centers

摘要

In this article,we describe a series of new complex salts in which electron-donating cis-{Ru~II(NH_3)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 beta have been determined by using hyper-Rayleigh scattering at 800 nm and also via Stark(electroabsorption)spectroscopic studies on the intense,visible d ->pi*metal-to-ligand charge-transfer bands.These experiments reveal that these dipolar pseudo-C_2v chromophores exhibit two substantial components of the beta tensor,beta_zzz and beta_zyy,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.