-Pyrrole functionalized push-pull BODIPYs: Synthesis, photophysical, electrochemical, thermal and computational studies

A series of beta-pyrrole functionalized push-pull BODIPYs BDP 1-6 were designed and synthesized via Palladium-catalyzed Suzuki cross-coupling reaction and by increasing the oxidation state of the sulfur atom in the thiazine ring. The effect of various donor entities on the photophysical, electrochemical, thermal, and computational studies of the BODIPY was investigated. The absorption spectra of the push-pull BODIPY BDP 2 show a red shift compared to the rest of the BDPs, due to strong donor-acceptor interaction. The phenothiazine-5,5-dioxide functionalized BODIPY BDP 6 exhibit a blue shift in the UV-vis region compared to the phenothiazine substituted BODIPY BDP 5 due to the weak donor ability of the phenothiazine-5,5-dioxide unit. The electrochemical studies were performed for the push-pull BODIPYs BDP 1-6 to analyze the effect of different donor groups on the redox properties of the BODIPY. The thermogravimetric analysis of the BODIPYs BDP 1-6 shows that BDP 2 exhibits excellent thermal stability compared to BDP 1, 3, 4, 5, and 6. The theoretical studies reveal that the phenothiazine-5,5-dioxide substituted BODIPY BDP 6 exhibits a large HOMO-LUMO gap compared to phenothiazine functionalized BODIPY BDP 5 due to the low donor ability of the phenothiazine-5,5-dioxide unit. The theoretical calculations were consistent with the experimental observations.