Structure, absorption and fluorescence of (bi)thiophene substituted methylidene-pyrrolinones

Four thiophene and bithiophene substituted methylidene-pyrrolinones were synthesized and their absorption and fluorescence properties were compared with previously reported behavior of their phenyl and biphenyl substituted analogues. Their structures were estimated theoretically by density functional theory (DFT) and proved by X-ray diffraction in two cases. Thiophene derivatives show a considerable bathochromic shifts in absorption with respect to phenyl analogues, in accordance with theoretical predictions based on time dependent DFT. Conjugation extension caused a bathochromic shift in absorption, too. All compounds show fluorescence in low temperature solvent glass, while only one bithiophene substituted derivative fluoresce weakly in room temperature solution. Three of four N-methylated derivatives show strong yellow, orange and red solid-state fluorescence. An ability of solid-state fluorescence was correlated with nearest neighbor out-of-plane interactions in crystal.