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

A series of nonlinear optical chromophores 6 containing a substituted benzothiazole ring have been synthesized and characterized. 1, 3 -Benzothiazoles 6 were prepared by treating 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 revealed by the intense and markedly solvatochromic CT transitions. The solvatochromic behaviour of compounds 6 was determined by linear regression analyses of absorption maxima in several solvents, where benzothiazole 6f was found to be a very appropriate indicator dye whose absorption wavenumbers (Delta(v) over tilde (max) = 1590 cm(-1)) in aliphatic and dipolar aprotic and in aromatic and chlorinated solvents correlated excellently with the pi* values defined by Kamlet and Taft. Hyper-Rayleigh scattering was used to measure the first hyperpolarizabilities beta. of the aforementioned compounds. Thermogravimetric analysis (TGA) was used to evaluate their thermal stability. The experimental results indicate that good nonlinearity and thermal stability are well balanced for chromophores 6, making them good candidates for device applications. ((c) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)