Synthesis and coordination behaviors of 14-membered tetraaza macrocyclic copper(II) complexes bearing two N-propionic acid or N-propionic methyl ester groups

New di-N-functionalized macrocyclic copper(II) complexes [Cu(H2L3)]2+ (R = CH2CH2COOH) and [CuL4]2+ (R = CH2CH2COOMe) as well as [CuL2]2+ (R = CH2CH2CN) are reported. The N-CH2CH2COOH groups of [Cu(H2L3)](ClO4)2 are not coordinated to the metal ion in the solid state, though they are involved in coordination in various solvents. Two stable isomers of [CuL4](ClO4)2, 1 (four-coordinate) and 2 (five-coordinate) have been prepared selectively and structurally characterized.