Synthesis and crystal structure determination of some asymmetrical and symmetrical CR-type macrocyclic schiff base complexes, with a single pendant coordinating 2-aminoethyl arm

A novel, totally asymmetrical tripodal 2,3′,4″-tetraamine ligand, N{(CH2)2NH2} {(CH2)3NH2} {(CH2)4NH2}, epb, has been synthesized. In the presence of copper(II) and nickel(II) ions it condenses with 2,6-diacetylpyridine in 1:1 ethanol - water solution, producing some new CR-type complexes with a pendant primary amino group. The X-ray crystal structure of the resulting copper(II) complex, [Cu(3,4(2)-CR)](PF6)2 (1), and two other related complexes, [Cu(2,4(2)-CR)](ClO4)2 (2) and [Cu(3,3(2)-CR)](ClO4)2 (3), are reported. Crystal data: complex 1, monoclinic, p21/n, a = 8.366(3) Å, b = 15.549(3) Å, c = 20.283(2) Å, β = .98.73(2)°, V = 2607.8(11) Å3, Z = 4, R1 = 0.0621, wR2 = 0.1615; complex 2, monoclinic, P21/c, a = 7.981(10) Å, b = 18.882(3) Å, c = 15.185(3) Å, β = 96.40(2)°, V = 2275.7(6) Å3, Z = 4, R1 = 0.0773, wR2 = 0.1635; complex 3, monoclinic, P21/n, a = 7.8764(10) Å, b = 15.361(2) Å, c = 19.370(2) Å, β = 100.330(10)°, V = 2305.7(5) Å3, Z = 4, R1 = 0.0537, wR2 = 0.1397. In all of these, copper atoms are bonded to four nitrogens of a macrocyclic ring and a nitrogen of the pendant arm. The arrangements are slightly distorted square-pyramidal in which the primary amino groups occupy apical positions and have the longest Cu - N distances. For all isomers, copper(II) ions are somewhat above the plane of the imino - pyridine system of the macrocyclic ring in the direction of the pendant coordinated primary amino group.