Synthesis of Donor-Acceptor (D-A) Hybrids Based on Functionalized Thiophene-imides for High Fluorescent Material Development

Nowadays, high efficient and low cost organic fluorescent semiconductor materials are extremely important for the development of new technological photoelectronic devices. These materials have been obtained from hybrid systems containing two sub-units: one with higher electronic density (electron donor (D)), and another one with lower electronic density (electron acceptor (A)).1-3 These Donor-Acceptor (D-A) or ambipolar systems with high conjugation increases the quantum efficiency. This work presents the synthesis and the study of photophysical properties of novel D-A hybrids: N-aryl-thiophenoimides 1 and 2 (Figure 1) formed by thiophene-dicarboxy (A) and two fluorescent amino units (D). Derivatives 1 and 2 were obtained (80% yield) by imide condensation reactions between the 3,4-dicarboxythiophene anhydride and the corresponding amines. The conjugation and the occurrence of locally excited state (LE) and/or inter-chain charge-transfer state (CT) were investigated by UV-Visible, photoluminescence spectroscopy (PL), and solvatochromic experiments applied to the final hybrid and the initial sub-units. 1 and 2 show strong light emissions at 540 and 570 nm and, in fact, these hybrids exhibited usual redshift values in UV absorption ( 21-30 nm) in comparison to the corresponding precursors. However, much higher redshitf values were obtained in PL emission ( 180-210 nm), since generally the measured values are lower than 100 nm3. These novel thiopheneimide hybrids seem to be promising materials as novel luminescent materials.