Synthesis, properties, and solvatochromism of 1,3-dimethyl-5-{(thien-2-yl)-[4-(1-piperidyl)phenyl]methylidene}-(1H,3H)-pyrimidine-2,4,6-trione

A new merocyanine dye, 1,3-Dimethyl-5-{(thien-2-yl)-[4-(1-piperidyl)phenyl]methylidenel} (1H, 3H)-pyrimidine-2,4,6-trione 3, has been synthesized by condensation of 2-[4-(piperidyl)benzoyl]thiophene 1 with N,N'-dimethyl barbituric acid 2. The solvatochromic response of 3 dissolved in 26 solvents of different polarity has been measured. The solvent-dependent long-wavelength UV/Vis spectroscopic absorption maxima, v(max), are analyzed using the empirical Kamlet-Taft solvent parameters pi* (dipolarity/polarizability), a (hydrogen-bond donating capacity), and (hydrogen-bond accepting ability) in terms of the well-established linear solvation energy relationship (LSER): (v) over tilde (max) = ( (v) over tilde (max))(0) + S pi* + a alpha + b beta The solvent independent coefficients s, a, and b and (V-max)(0) have been determined. The McRae equation and the empirical solvent polarity index, E-T(30) have been also used to study the solvatochromism of 3. Copyright (c) 2007 John Wiley & Sons, Ltd.