Complex Formation of Phenothiazine with Bivalent Metal Ions in the Presence of Micelles

Abstract

The complex formation of phenothiazine with bivalent metal ions was examined spectrophotometrically in the surfactant micellar solutions of bivalent metal alkyl sulfates (M(C₁₂H₂₅OSO₃)₂; M=Cu²⁺, Mg²⁺, Mn²⁺, Co²⁺, Ni²⁺), where the bivalent metals constituted the counter ions of micelles. Every counter ion formed a complex with phenothiazine. The complexation reaction of Cu²⁺ ion was much faster than the others and the reaction obeyed the apparent first-order kinetics whose rate constant (k₁) was 3.0×10^-5 sec^-1. The characteristic wavelengths at absorption maxima of the M-phenothiazine complexes were in the ranges of 460-470nm and of 650-670nm, the respective molecular extinction coefficient (ε) being 4.35×10² at 650nm and 6.15×10²m²mol^-1 at 660nm for Cu²⁺- and Mn²⁺-complexes. From spectral changes of phenothiazine in the micellar solutions, the location of solubilized phenothiazine was found to be in the outer hydrophobic part near the micellar surface so called the palisade layer rather than in the micellar interior.