A general and very straightforward route to the selective N-functionalization of 1,4,7-triazacyclononane with imidazole groups. Crystal structure determinations of nickel(II), copper(II) and zinc(II) complexes

An easy, one-step procedure for the synthesis of the selectively substituted macrocycles 1-(1-methylimidazol-2-ylmethyl)-1,4,7-triazacyclononane, L-1, and 1,4-bis(1-methylimidazol-2-ylmethyl)-1,4,7-triazacyclononane, L-2, is reported. The potentially tetra-, L-1, and pentadentate, L-2, compounds yield nickel(II), copper(II) and zinc(II) complexes which have been isolated in the solid state. The crystal structures of [NiL1(N-3)](2)[PF6](2) (1), [Cu2L21(OH)][PF6](3) (2), [(ZnLCl)-Cl-1]BPh4 (3), [NiL2(H2O)][BPh4](2).C2H5OH (4) and [Ni2L22(N-3)][PF6](3) (5) have been determined by X-ray diffraction studies. The L-1 and L-2 molecules provide four and, respectively, five nitrogens for complexation of the metal ions whose coordination requirements are completed by additional ligands either terminal (Cl, H2O, compounds 3 and 4) or bridging two metal ions (N-3(-), compounds 1 and 5; OH-, compound 2). In its complexes nickel(II) is six-coordinated in an approximately octahedral environment. Both copper(II) and zinc(II) are five-coordinated with geometries approximately square pyramidal and, respectively, trigonal bipyramidal. (C) 2000 Elsevier Science S.A. All rights reserved.