摘要:
The synthesis and characterization of Cu[C6H4(NH)2]2 [C6H4(NH)2 = semi-benzoquinonediiminate, abbreviated s-bqdi] are described and its relevant properties are compared with those of the known d8 and d6 metal bis- or tris-benzoquinonediiminate. The complex is paramagnetic in the solid state with mu-eff = 1.86 BM. The dominant form of Cu(s-bqdi)2 in aliphatic alcohols like methanol, ethanol and n-butanol or in THF is dimeric or oligomeric, but monomeric in acetonitrile, DMSO and DMF, as proved by UV-vis and ESR spectra. The stability of Cu(s-bqdi)2 to oxygen exposure in different solvents parallels the association behaviour and follows the order: ethanol >> DMF >> acetonitrile. The electrochemical (voltammetric) response of the [Cu-N4]z system (z = 0, +/- 1, +/- 2) in acetonitrile consists of two 0 reversible + 1 (E1/2 = -0.10 V vs SCE) and + 1 reversible + 2 (E1/2 = + 0.98 V vs SCE) reversible electron transfers and an irreversible process at E(p.c) = -1.87 V attributed to 0 --> -1 reduction. Iodination of an ethanolic solution of Cu(s-bqdi)2 led to the isolation of polycrystalline Cu(s-bqdi)2I5 which is formulated as Cu(s-bqdi)2(I3)1.66 on the basis of IR, Raman and thermogravimetric analysis. The new material exhibits high, room-temperature conductivity (sigma = 6.6.10(-2) S cm-1) and semiconducting behaviour in the temperature range 70-300 K, with a sharp transition at 215 K. Static magnetic susceptibility measurements provide mu-eff = 1.23 BM for Cu(s-bqdi)2(I3)1.66 at 295 K [calculated from mu-eff = 2.83(chi-T)1/2] which is found to obey the Curie-Weiss law between 70 and 295 K. The electrical and magnetic behaviour of Cu(s-bqdi)2(I3)1.66 is interpreted as being due to strong homomolecular intra- and interstack interactions between donor molecules with radical cationic character.