Dimerization of 5,10,15,20-tetrakis(6-N-methylquinolinyl)porphyrin in aqueous solutions was studied in the range 274–343 K using absorption and fluorescence spectroscopy. The dimerization equilibrium constant KD was shown to vary over a wide range as the temperature changed. The enthalpy ΔH‡ and entropy ΔS‡ of dimerization in solutions of different ionic strengths were measured. The dimerization was found to be enthalpy driven in all cases. The proposed explanation for the large negative enthalpies of dimerization ΔH‡ was the optimal overlap of porphyrin macrocycles due to minimization of Coulombic repulsion of ionized peripheral substituents located at large distances from the macrocycle.
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Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 87, No. 5, pp. 700–705, September–October, 2020.
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Klenitsky, D.V., Vershilovskaya, I.V. & Kruk, M.M. Spectroscopic Study of the Dimerization of 5,10,15,20-Tetrakis(6-N-Methylquinolinyl)Porphyrin in Aqueous Solutions. J Appl Spectrosc 87, 784–788 (2020). https://doi.org/10.1007/s10812-020-01070-7
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DOI: https://doi.org/10.1007/s10812-020-01070-7