The Photokinetics of Electron Transfer Reaction of Methylene Blue with Titanium Trichloride in Aqueous–Alcoholic Solvents

• Published in: Journal of the Chinese Chemical Society (Taipei) 2017-10, Vol.64 (10), p.1147-1155
• Main Authors: Nadeem, Syed Muhammad Saqib, Saeed, Rehana
• Format: Article
• Language: English
• Subjects: Electron transfer; Electron transfer reactions; Enthalpy; Free energy; kinetics; Methylene blue; Polarity; Reaction kinetics; Solvents; Titanium; titanium trichloride
• ISSN: 0009-4536; 2192-6549
• DOI: 10.1002/jccs.201700112

The kinetics of photoinduced electron transfer reaction of methylene blue (MB) and titanium trichloride was investigated in water and different aqueous–alcoholic solvents. The reaction is pseudo‐first order, dependent only on the concentration of titanium trichloride at a fixed concentration of MB. The effect of water and aqueous–alcoholic solvents was studied in the acidic pH range (4–7). It was observed that the quantum yield (ϕ) of the reaction increased with increase in polarity of the reaction medium. The quantum yield was high under acidic conditions and decreased with further increase in acidity. The addition of ions and increase in temperature increased the rate and quantum yield of the reaction. The absence of any reaction intermediate was confirmed by spectroscopic investigations. A mechanism for the reaction has been proposed in accordance with the kinetics of the reaction. The activation energy (Ea) was calculated by the Arrhenius relation. Thermodynamic parameters such as Ea, enthalpy change (ΔH), free energy change (ΔG), and entropy change (ΔS) were also evaluated. The photokinetics of electron transfer reaction of methylene blue with titanium trichloride was studied in water and different aqueous–alcoholic solvents. The rate of reaction was evaluated by determining the quantum yield of reaction, and the effect of different reaction parameters on the quantum yield was evaluated. A reaction mechanism was proposed for the electron transfer reaction; the associated thermodynamic changes were also evaluated.