ACID DISSOCIATION BEHAVIOR OF 2,3-METHYL-SUBSTITUTED AND 2,3,9,10-METHYL-SUBSTITUTED OR CYCLOHEXYL-SUBSTITUTED CYCLAMS, THEIR COMPLEXATION BEHAVIOR WITH COPPER(II) AND THE AXIAL SOLVENT INTERACTION EFFECT ON THE LIGAND-FIELD SPECTRUM OF THEIR COMPLEXES

Stability constants of Cu(IT)-complexes for 1, 4, 8, 11-tetra-azacyclo tetradecane (cyclam) analogs with periphery substituted [14]aneN(4)-ri ng, 2,3-tetramethyl-, 2, 3, 9, 10-octamethyl-, 2, 3-cyclohexyl, and 2, 3, 9, 10-dicyclohexyl-cyclams have been determined at 25 degrees C in aqueous solution. The UV-Vis absorption spectra of their complexes, ( [Cu(L)] (ClO4)(2)), were measured in water and some typical organic so lvents (methanol, acetone, propylene carbonate, formamide, N, N-dimeth ylformamide, and dimethylsulfoxide). A good linear relationship was fo und between the stability constant (logK(CuL)) and the difference betw een the wavenumber of maximum absorption in water and in the organic s olvents (Delta lambda(max)(-1) (W-S)). The value of logK(CuL) at Delta lambda(max)(W-S) = 0 not only shows a linear relation to solvent para meters, donor number and dielectric constant, but also to the enthalpy of transfer of ClO4- from water to the organic solvents. The value is proposed as a new solvent parameter 'K-lambda-value' to be used as an index for solvent-effects on Cu(II)-complexes of cyclam analogs. The increasing order of the new parameter (log scare) is as follows; (27.1 4)>FA(26.82)>MeOH(26.27)>PC(25.75)>AC(24.71). Another meaning of the n ew parameter is assumed from connection of the potentiometric data wit h spectrometric data. The solvent effects on stability and the UV-Vis spectra are assumed to be caused by perturbation of the D-4h or axiall y-elongated ligand field through axial approach of solvent to the Cu(I I)-complexes and by formation of a solvent-separated ion pair between a solvated Cu(II)-complex cation and counter anion (ClO4-).