The effect of N-methylation of tetra-aza-alkane copper complexes on the axial binding of anions

The stability constants of the Cu(II) complex of Me(6)tren (Me(6)tren=tris-(2-dimethylaminoethyl)amine) were determined. The axial binding constants of F-, Br-, I- and N-3(-) to Cu(tren)(2+) and Cu(Me(6)tren)(2+) (tren=tris-(2-aminoethyl)amine) were measured. The results obtained are compared with those of the axial binding constants of the isomers, i.e. the complexes Cu(trien)(2+) and Cu(Me(6)trien)(2+) (trien=1,4,7,10-tetraazadecane; Me(6)trien=2,5,8,11-tetramethyl-2,5,8,11-tetraazadodecane). The results point out that N-methylation transforms the Cu(II)L complexes into stronger and harder acids. Properties of the copper complexes with TMC (1,4,8,11-tetramethy-1,4,8,11-tetraazacyclotetradecane) and with Me(6)trpn (tris-(3-dimethylaminopropyl)amine) are also reported.