Studies on a new type of surface-active copper(II) complexes, acetylacetonatochloro(N,N,N′-trimethyl-N′-alkylethylenediamine) copper(II): An ESR, spectrophotometric, and kinetic investigation

Surface-active mixed copper (II) chelates of the type [Cu(R-tmed)(acac)Cl], where R = C₁₀H₂₁, C₁₂H₂₅, and C₁₆H₃₃, were prepared and characterized by elemental analysis and IR spectroscopy. Critical micelle concentration value was obtained by surface tensiometry for each of the complexes. From the ESR and UV-visible spectrophotometric studies, a structure in which the square planar copper(II)-containing head groups position themselves in a face-to-face manner with the chloride ions/water molecules located between them is proposed. The observation of separate ESR signals for the monomers and micelle implies that the rate of exchange between them is slow on the ESR time scale, i.e., <1 × 10⁸ s^-1. The linewidth broadening on increasing the concentration and on addition of sodium chloride is caused by an increase in the size of the micelle. The micelles of these mixed copper(II) chelates exhibit good catalytic activities toward the hydrolysis of p-nitrophenyl diphenylphosphate. In general for a given chain length, however, the rate is roughly 10 times slower than that of [Cu(R-tmed)Cl₂]. The rate maximum in the rate vs concentration plot decreases as the chain length increases. This is attributed to a decrease in the degree of ionization of the micelle as the chain length increases.