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K. Anbalagan, L. Devaraj Stephen
Influence of Water–Methanol Solvation Assembly and the Key Consequences on the Photo Reduction of CoIII(L)33+ (L = (NH3)2, en, pn) Complexes via Ion-Pair Formation
Keywords: Solvation Effect, Photoreduction in Binary Solvents, Regression Analysis, Cobalt(III)-Am(m)ine Complexes, Photoreaction of Cobalt(III) Complexes
Cobalt(III) complexes of general formulae Co(L)33+, where L refers to (NH3)2, en (1,2-diamino ethane) and pn (1,2-diamino propane) have been subjected to photolysis (excitation wavelength; λ = 254 nm) in water-methanol mixtures (0, 5, 10, 15, 20, 25 and 30% (v/v) methanol). In each mixture as the mole fraction of water surpassed, the observed quantum yield values were triggered. Therefore, ΦCo(II) measured in the binary solvents were subjected to Linear Solvation Energy Relationship (LSER) to model the ΦCo(II) data using the measured empirical solvent parameters in order to break open the solvation effects of excited state reactivities. The photo reduction is solvent dependent; has the form logΦCo(II) = a0 + a1X1 (X1 = xMeOH or εr−1). Effect of solvent polarity in Grunwald–Winstein correlations (r2 = 0.950) is discussed by linear regression analysis incorporating solvent ionizing power (YGW) scale and ΦCo(II) profile. Major causes for these phenomena are investigated in terms of long range solvation effects, in conjunction with short range solvation effects. Distinct border lines between the two are derived from photolysis yields in six solvent mixtures using the results of logΦCo(II) = a0 + a1X1 + a2X2 + ... plots, where X1, X2 etc. are independent variables (like ETN, DNN, α, β, and π*) representing physicochemical characteristics of solvent. These plots show appreciable correlation of data, which were quantified to unravel solvation effects.
Zeitschrift für Physikalische Chemie, Oldenbourg Wissenschaftsverlag
Print ISSN: 0942-9352
Volume: 220, 03/2006
Pages: 335 - 348