Synthesis, optical and electrochemical properties of carbazole sensitizers and their interaction with TiO2

•Carbazole with two different electron withdrawing group were synthesized.•ICT transition is observed by introducing the electron withdrawing anchoring groups.•Carbazole having rhodhanine group shows better electron withdrawing character.•Specific solvent effect in charge transfer transition is observed.•Carboxylate anchoring group have higher binding ability than nitro group with TiO2.

Two carbazole derivatives (CN, CR) were synthesized and characterized by 1H, 13C NMR, Mass, IR and cyclic voltammetry measurements. The absorption of CR appears at higher wavelength than CN. Effect of solvents on the absorption and emission properties of the sensitizers was analyzed. Interaction of these sensitizers with TiO2 was studied by using absorption and fluorescence measurements. Ground state complex formation was observed from steady state measurements. Binding constant (K) was calculated from fluorescence quenching measurements. The possibility of electron transfer from the excited state sensitizers to the conduction band of TiO2 was analyzed using energy levels and Rehm–Weller equation.