NEW TRIMETHYLAMMONIUM DERIVATIVES TOWARD SECOND-ORDER NONLINEAR OPTICS

Abstract

In order to find new ionic compounds with good characteristics for second harmonic generation (SHG), the relationship between first hyperpolarizabilities (β) and the position of the cationic center with respect to the benzene ring was investigated. The β values of a series of trimethylammonium cations: X–C 6 H 4–( CH 2)n N +( CH 3)3, where X = H , CH 3, OCH 3, NH 2, and N ( CH 3)2; n = 0–2, were calculated by using the MOPAC PM3 method. Relatively large calculated β values were obtained when X = N ( CH 3)2 and X = NH 2. Series of [4-(dimethylamino)phenyl]trimethylammonium ( X = N ( CH 3)2; n = 0) and [2-(4-aminophenyl)ethyl]trimethylammonium ( X = NH 2; n = 2) derivatives were synthesized. Among them, seven SHG-active complexes were found and four crystal structures were determined.