π-Conjugated 2,1,3-benzothiadiazole derivatives (BTDs) based on the D-π-A framework have recently received significant attention because of their potential applications in the field of organic light-emitting diodes (OLEDs), photovoltaics, organic field-effect transistors (OFETs), fluorescence sensors and fluorescence imaging probes.1,2 This is due to their absorption in the visible-light region with large molar absorptivity, high quantum yield with a large Stokes shift, small optical band gap, facile synthetic accessibility as well as high thermal and optical stability in solutions and solids. The unique photophysical properties of BTDs are the result of through-bond intramolecular charge transfer (ICT) taking place from the donor moiety towards the acceptor moiety.3 In a polar solvent medium, this ICT state becomes the lowest energy state compared to the Franck-Condon or locally excited (LE) state. Thus, we aim to couple 2,1,3-benzothiadiazole (BTD) moiety as a strong electron receptor, with electron-donating substituted aromatic moiety, through the π-acetylene bridge leading to develop efficient fluorescence emission with unique optical properties. A series of π-conjugated 2,1,3-benzothiadiazole derivatives with different electron-donating and electron-withdrawing substituents have been synthesized through the Sonogashira cross-coupling reaction. Detailed photophysical studies have been carried out in homogeneous solvents and heterogeneous organized media. Some of the synthesized molecules show appreciable ICT behavior. It was also found that the fluorescence anisotropy of some molecules in solvent media shows excellent sensitivity towards viscosity changes in the medium. This can be useful for estimating the microviscosity of different media. After giving an overview of the literature in this area, our preliminary findings will be discussed during this presentation.
References:
1 Neto, B. A. D.; Carvalho, P. H. P. R.; Correa, J. R. Acc. Chem. Res., 2015, 48, 1560–1569.
2 Westrup, J. L.; Oenning, L. W.; Paula, M. M. D. S.; Duarte, R.C.; Rodembusch, F. S.; Frizon, T. E. A.; Silva L. D.; Dal-Bo, A. G. Dye. Pigment., 2016, 126, 209–217.
3 Wang, Z.; Peng, Z.; Huang, K.; Lu, P.; Wang, Y. J. Mater. Chem. C, 2019, 7, 6706–6713.