Molecular Engineering of Benzothiazolium Salts with Large Quadratic Hyperpolarizabilities: Can Auxiliary Electron-Withdrawing Groups Enhance Nonlinear Optical Responses?

• DOI: 10.1021/jp108623d
• Publication Date: 2010-11-24T13:44:11Z
• Authors: Peter Hrobárik; Ivica Sigmundová; Pavol Zahradník; Peter Kasák; Vladimir Arion; Edith Franz; Koen Clays
• Keywords: Polar effect; Chromophore

A series of push−pull chromophores comprising a dimethylamino or diphenylamino electron-donating functionality and cationic benzothiazolium acceptor with an additional electron-withdrawing group (EWG = NO2 CN) at various positions the heterocyclic benzene ring have been synthesized comprehensively investigated for their linear quadratic nonlinear optical (NLO) properties by means UV−visible spectroscopy hyper-Rayleigh scattering, as well quantum-chemical calculations different levels theory (B3LYP, CAM-B3LYP, MP2, RI-CC2). In general, all under study display large static hyperpolarizabilities β0, comparable to in most cases even larger than conventional stilbazolium-containing analogues, which makes these systems attractive practical NLO applications. The introduction auxiliary EWG into causes substantial red shift intramolecular charge-transfer band. Still, same time, this modification structure reduces β0 values longer π-conjugated spacers. unexpected negative impact substitution pattern on activity is rationalized experimentally determined one-photon absorption characteristics discussed detail. Furthermore, computational studies revealed that dyes "reverse" polarity respect commonly used one would be more worthwhile target synthesis, because enhanced response due positive effect group.