METAL-COMPLEXES OF THE NEW LIGAND 1,2,6,7-TETRACYANO-3,5-DIIMINO-3,5-DIHYDROPYRROLIZINIDE, MII(C11N7H2)2, AS BASIC UNITS FOR MOLECULAR MATERIALS - ELECTROCHEMICAL AND METAL PHTHALOCYANINE-LIKE ELECTRONIC-PROPERTIES OF THE NICKEL(II) COMPLEX AND X-RAY CRYSTAL-STRUCTURES OF ITS ADDUCTS WITH DIOXANE AND TETRATHIAFULVALENE

The synthesis, characterization, and electrochemical behavior of the bis(1,2,6,7-tetracyano-3,5-diimino-3,5-dihydropyrrolizinido)nickel(II) complex, Ni(beta-dtpy)2, have been investigated. In solution it is square planar and shows a metalphthalocyanine-like electronic structure. In the solid state it incorporates oxygenated solvent of crystallization and the nickel is hexacoordinated, as from the results of the reported X-my crystal structure of Ni(C11N7H2)2.2H2O.3diox (3) (diox = 1,4-dioxane). The crystal structure of the TTF and THF adduct, Ni(C11N7H2)2.TTF.2THF (4), is also reported: it is a charge-transfer complex, consisting of infinite stacks of alternate donor and acceptor molecules. Both complexes crystallize in the monoclinic system. Crystal data are as follows: for 3, C34H32N14NiO8, space group P2(1)/n, a = 11.184 (3) angstrom, b = 15.682 (4) angstrom, c = 11.720 (4) angstrom, beta = 110.77 (2)degrees, Z = 2; for 4, C36H24N14NiO2S4, space group P2(1)/c, a = 11.920 (3) angstrom, b = 21.612 (8) angstrom, c = 7.979 (2) angstrom, beta = 109.68 (2)degrees, Z = 2. The cyclic voltammetry of Ni(beta-dtpy)2 shows multistep, overlapping reduction waves from 0 to -1.5 V vs SCE. A very small concentration of the radical monoanion Ni(beta-dtpy)2.- can be generated in solution, as detected by EPR spectroscopy during in situ electrolysis in DMF with LiClO4 as supporting electrolyte (unresolved structure signal, g = 2.0057). Nevertheless the radical monoanion can be quantitatively isolated in the solid state as Ni(beta-dtpy)2.-Et4N+.3CH3OH (6) when the electrolysis of Ni(beta-dtpy)2 is carried out in methanol with TEAP as supporting electrolyte. 6 is a semiconductor (sigma = 1.062 X 10(-4) S cm-1; E(a) = 0.024 eV) with the unpaired electrons partially antiferromagnetically coupled at room temperature (mu-eff = 1.36-mu-B). As far as the delocalization of the odd electron in Ni(beta-dtpy)2.- anion is concerned, both the ESR and ESCA data of 6 show that it is confined mainly to the ligand system.