Preparation, properties and crystal structure of two isomers of R, R, S, S- and R, S, R, S-[chloro(1,3,10,12,16,19-hexaazatetracyclo[17,3,1,1 12,16,0 4,9]tetracosane)copper(II)] +

Abstract

Two isomers ( R, S, R, S- and R, R, S, S-) of five coordinate complex [Cu(L)Cl] + have been separated and characterised. These two isomers have significantly different spectrochemical and electrochemical properties. Absorption maximum of R, S, R, S-[Cu(L)Cl] + shifts to longer wavelength and its reduction potential shifts to more positive direction comparing those of R, R, S, S-[Cu(L)Cl] +. R, S, R, S-[Cu(L)Cl] + is significantly distorted to trigonal-bipyramidal structure, whereas R, R, S, S-[Cu(L)Cl] + retains almost square-planar geometry. The average bond distance of Cu–N in basal plane of R, S, R, S-[Cu(L)Cl] + is longer by 0.024 Å than that of R, R, S, S-[Cu(L)Cl] +, whereas the bond distance of Cu–Cl in former is shorter by 0.200 Å than that in latter. The isolated square-planar complexes of R, R, S, S- and R, S, R, S-[Cu(L)](ClO 4) 2 are converted to the R, R, S, S- and R, S, R, S-[Cu(L)Cl] + by the addition of Cl − in nitromethane solution with the rate constants, k=1.70 (±0.02) and 8.31 (±0.07) M −1 s −1, respectively.