Polynuclear nickel(II) and copper(II) complexes of hexaazamacrocycles incorporating pairs of diethylenetriamine subunits separated by aromatic spacers

A series of Ni(II) and Cu(II) complexes of the hexaaza macrocycles, 3,6,9,17,20,23-hexaazatricyclo[23.3.1.1(11,15)]triaconta-1(29),11(30),12,14,25,27-hexaene (L-1) and 3,6,9,16,19,22-hexaazatricyclo[22.2.2.2(11,14)]triaconta-1(26),11(29),12,14(30),24(28),25-hexaene (L-2), have been prepared and the crystal structures determined for [Ni2L1(O2CCH3)(2)(H2O)(2)](ClO4)(2) (1), [Ni2L2(DMF)(6)] (ClO4)(4) (.) 2H(2)O (2), {[(Cu2LBr)-Br-2(O2CCH3)](ClO4)(2)}(n) (3), [Cu2L2(mu-CO3)(H2O)(2)](2)(ClO4)(4) (.) 8H(2)O (4), [Cu2L2(O2CCH3)(2)](BF4)(2) (5), and [Cu2L1(mu-imidazolate)Br](2)Br-4 (.) 6H(2)O (6). In these complexes, two metal centers are bound per ligand; in 1 and 3-6, the N-3 subunits of L-1 or L-2 coordinate meridionally to the metal centers, whilst in 2, each N-3 subunit in L 2 adopts a facial mode of coordination. The binuclear cations in 1 and 2 have chair-like conformations, with the distorted octahedral Ni(II) coordination spheres completed by terminal water and a bidentate acetate ligand in 1 and three DMF ligands in 2. The Cu(II) centers in 3-6 generally reside in square planar environments, although a weakly binding ligand enters the coordination sphere in some cases, generating a distorted square pyramidal geometry. The binuclear [Cu2L2](4+) units in 3, 4 and 5 adopt similar bowl-shaped conformations, stabilized by H-bonding interactions between pairs of amine groups from L-2 and a perchlorate or tetrafluoroborate anion. In 3, the binuclear units are linked through acetate groups, bridging in a syn-anti fashion, to produce a zig-zag polymeric chain structure, whilst 4 incorporates a tetrameric cation consisting of two binuclear units linked via a pair of carbonate bridges. Compound 6 features an imidazolate bridge between the two Cu(II) centers bound by L-1. Pairs of [Cu2L1(mu-imidazolate)](3+) units are then weakly linked through a pair of bromide anions. (c) 2005 Elsevier B.V. All rights reserved.