Synthesis of new donor-acceptor thiophene linked coumarin chromophores: Potential photosensitizers for dye sensitized solar cells

Abstract

Synthesis of four new dyes, designated as <strong>C1-C4</strong>, incorporating dialkylamino coumarin as a donor, thiophene ring as a common spacer and quinazolinone-N-acetic acid, homophthalimide-N-acetic acid, rhodanine acetic acid and indoline carboxylic acid as acceptors, respectively is reported. Condensation of 4-diethylaminosalicaldehyde with thiophene-2-acetic acid methyl ester afforded 3-(2-thiophenyl) coumarin <strong>3</strong>, which has been formylated to afford aldehyde <strong>4</strong>. Knoevenagel condensation of <strong>4</strong> with four different acceptors affords <strong>C1-C4</strong>. The dyes show absorption maxima in the range of 497 to 538 nm and high extinction coefficients in the range of 32700 to 54300 M⁻¹cm⁻¹. The band gaps of <strong>C1-C4</strong>, derived from the absorption cut-off edges are estimated to be 2.21, 2.27, 2.09 and 2.00 eV respectively. High extinction coefficients coupled with narrow band gaps are promising features of these dyes which may allow them to act as photosensitizers in dye sensitized solar cells.