2-arylthienyl-substituted 1,3-benzothiazoles as new nonlinear optical chromophores

Abstract

A series of nonlinear optical chromophores 6 containing a substituted benzothiazole ring have been synthesized and characterized. 1,3-Benzothiazoles 6 were prepared by reacting various formyl derivatives of thienyl compounds with ortho-aminobenzenethiol in fair to excellent yields. These in turn were prepared by Suzuki coupling between aryl and thienyl precursors. The electronic interactions between donor and acceptor end groups in the conjugated 1,3-benzothiazoles 6 are expressed in the intense and markedly solvatochromic CT transitions. The solvatochromic behaviour of compounds 6 was determinated by linear regression analyses of absorption maxima in several solvents, whereby benzothiazole 6f was found to be a very appropriate indicator dye whose absorption wavenumbers (νmax= 1590 cm –1) in aliphatic and dipolar aprotic and in aromatic and chlorinated solvents excellently correlate with the π* values defined by Kamlet and Taft. Hyper-Rayleigh scattering was used to measure the first hyperpolarizabilities β of the mentioned compounds. Thermo gravimetric analysis (TGA) was used to evaluate their thermal stability. The experimental results indicate that good nonlinearity–thermal stability is well balanced for chromophores 6, making them good candidates for device applications.