The synthesis and examination of spectral properties of some 2,2′-bithienyl derivatives with carbonyl-containing substituents

The theoretical and experimental study of ten model 2,2′-bithiophene (BT) derivatives containing carbonyl chromophoric pair in position 5 is presented. In this context, the synthesis and chemical characterization of four derivatives with substituents COCF3 (trifluoroacetyl) (H_CF), COCH3 acetyl (H_Me), COCH2CN oxopropanenitrile (H_CCN) and 5′-(9H-fluoren-9-ylidenemethyl)3-methyl,5-methylcarboxylate (FL_OMe) was described. The absorption and fluorescence spectra of prepared molecules were measured in solution (dichloromethane, methanol and acetonitrile). These selected molecules, comparing to the parental BT, exhibit in absorption spectrum the bathochromic shift about 50 nm and distinct fluorescence above 400 nm. The most intense fluorescence was observed for H_CCN and H_CF molecules and their lifetime of fluorescence was measured in the range 1.0–2.6 ns. The quantum chemical calculations were used for the investigation of the molecular electronic structure, energy diagrams of excited singlet and triplet states as well as optical properties of all selected derivatives.