Axial Hydration and Adsorption of Chloro (5,10,15,20-tetraphenylporphyrinato)manganese(III) at the Toluene/Water Interface, Studied by External Reflection Spectrophotometry

摘要

Interfacial adsorptoin of chloro(5,10,15,20-tetraphenylprophyrinato)manganese(III), [Mn(tpp)Cl], at the interface of toluene/aqueous sodium hydrogensulfate was studied by means of an UV/vis external reflection (ER) spectroscopy and interfacial tension measurements. The s-polarized ER spectrum showed higher sensitivity than the p-polarized one at the incident angle of 70.8 deg. A linear correlation sililar to Beer's law was obtained between the s-polarized ER absobance and the interfacial concentration determined from the interfacial tension. The molar ER coefficient at the maximum wavelength of 478 nm was determined as -8.41 x 10~5 (mol~(-1) cm~2). The effect of chloride ion concentation on the ER spectra suggested that the interfacial species at toluene/0.1 mol dm~(-3) sodium hydrogensulfate solution (pH 1.7) was mN(tpp)(H_2O)_i~+. The interfacial adsorption could be analyzed according to the Langmuir isotherm; the equilibrium constant for the adsorptoin reaction of Mn(tpp)Cl_0 + H_2O <=> Mn(tpp)(H_2O)_i~+ + Cl~- was determined as 59.6. Furthermore, it was suggsted that cloride ions were preferentially distributing at the diffuse layer under low chloride ion concentrations.