An investigation of decomposition stages of a ruthenium polypridyl complex by non-isothermal methods
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Thermal properties of [cis-(dithiocyanato)(4,5-diazafluoren-9-one)(4,4′-dicarboxy-2,2′-bipyridyl)ruthenium(II)], [Ru(L 1)(L 2)(NCS)2] (where the ligands L 1 = 4,5-diazafluoren-9-one, L 2 = 4,4′-dicarboxy-2,2′-bipyridyl) have been investigated by DTA/TG/DTG measurements under inert atmosphere in the temperature range of 30–1155 °C. The mass spectroscopy technique has been used to identify the products during pyrolytic decomposition. The pyrolytic final products have been analyzed by X-ray powder diffraction technique. A decomposition mechanism has been also suggested for the cis-[Ru(L 1)(L 2)(NCS)2] complex based on the results of thermogravimetrical and mass analysis. The values of the activation energy, E* have been obtained by using model-free Kissenger–Akahira–Sunose and Flyn–Wall–Ozawa non-isothermal methods for all decomposition stages. Thirteen kinetic model equations have been tested for selecting the best reaction models. The best model equations have been determined as A2, A3, D1, and D2 which correspond to nucleation and growth mechanism for A2 and A3 and diffusion mechanism for D1 and D2. The optimized average values of E* are 31.35, 58.48, 120.85, and 120.56 kJ mol−1 calculated by using the best model equations for four decomposition stages, respectively. Also, the average Arrhenius factor, A, has been obtained as 2.21, 2.61, 2.52, and 2.21 kJ mol−1 using the best model equation for four decomposition stages, respectively. The ΔH*, ΔS*, and ΔG* functions have been calculated using the optimized values.
KeywordsRuthenium complex Thermal behavior Dye sensitized solar cell Polypyridyl complexes Photosensitizer Charge transfer sensitizer
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