Multinuclear Ni(II), Cu(II) and Zn(II) complexes of chiral macrocyclic nonaazamine

Abstract

The chiral macrocyclic amines R-L and S-L derived from the 3 + 3 condensation of 2,6-diformylpyridine and (1R,2R)-1,2-diaminocyclohexane or (1S,2S)-1,2-diaminocyclohexane form enantiopure trinuclear Ni(ii) and Cu(ii) complexes [Ni3(L)(H2O)2Cl5]Cl and [Cu3(L)Cl4]Cl2 and form the dinuclear complex [Zn2(L)Cl2](ZnCl4) with Zn(ii). The X-ray crystal structures of these complexes indicate remarkably different conformations of the ligand and different binding modes of the chloride anions. The structure of the copper(ii) derivative [Cu3(R-L)Cl4]Cl2·CH3CN·7.5(H2O) indicates unsymmetrical conformation of the macrocycle with three dissimilar pentacoordinate copper(ii) ions bridged by chloride; the structure of [Ni3(R-L)(H2O)2Cl5]Cl·0.4CH3CN·4.2H2O is somewhat more symmetrical, with three Ni(ii) ions of distorted octahedral geometry, also bridged by a common chloride anion. On the other hand, the macrocycle is highly folded in [Zn2(R-L)Cl2](ZnCl4)·CHCl3·0.8CH3OH·3.7H2O, forming a cleft where the third Zn(ii) ion is held via electrostatic interactions as the ZnCl42- anion. The magnetic data for [Cu3(R-L)Cl4]Cl2 indicate the coexistence of antiferromagnetic and ferromagnetic interactions within the quasi isosceles tricopper(ii) core (J = -85.6 cm-1, j = 77.1 cm-1). Compound [Ni3(R-L)(H2O)2Cl5]Cl shows the presence of weak antiferromagnetic coupling (J = -2.56 cm-1, j = -1.54 cm-1) between the three Ni(ii) ions.