SYNTHESIS, CRYSTAL-STRUCTURE AND PROPERTIES OF THE NICKEL(II) COMPLEXOF A NEW DIOXOCYCLAM BEARING 2-METHYLFURAN PENDANTS

A new dioxocyclam ligand, bearing two 2-methylfuran pendants, has been synthesized and its nickel(II) complex isolated as a single crystal. The crystal structure of the complex has been determined by X-ray diff raction analysis. The complex adopts an unusual cis-configuration. The square-planar N-4 coordination of the four basal nitrogen atoms with Ni-II is evident, with the dioxocyclam moiety composed of two tertiary amine Ns and two deprotonated amide N(-)s; the latter nitrogens have stronger coordination bonds than those in the tertiary amines. There i s a hydrogen bond between O(1) and a water molecule [O(1) ... H2O = 2. 698 Angstrom]. The solution behaviour of NiL (1) has been further stud ied by u.v.-vis. and cyclic voltammetric techniques. A remarkable red- shift was observed for the maxima absorption band of the electronic sp ectra of NiL (1) in comparison to that of NiL(0) (H(2)L(0), dioxocycla m = 1,4,8,11-tetraazacyclo-tetradecane-5,7-dione).