An unprecedented DDQ-nickel(II)Salen complex interaction and X-ray crystal structure of nickel(II)Salen.DDH co-crystal

The charge transfer interaction between DDQ(2,3-dichloro-5,6-dicyano-1,4-benzoquinone) and [Ni(Salen)] (Salen = bis(salicylaldehyde)ethylenediimine) complex was studied in the solution and solid state. The yellow color of [Ni(Salen)] dissolved in dichloromethane or chloroform was changed to green in the presence of the DDQ The green precipitates of [Ni(Salen)](+)IDDQ(-) charge transfer complex were collected via adding the n-hexane to the solution. Crystallization of charge transfer solid from dichloromethane/chloroform resulted in [Ni(Salen)] and DDH (DDH = 2,3-dichloro-5,6-dicyano-1,4-dihydroxybezene), in which DDH was obtained from the catalytic reduction of DDQ via the oxidation of water. The structure of the new solid was determined by the X-ray crystallography. In this solid, DDH was combined with [Ni(Salen)] to create co-crystals, in which there were the DDH molecules, were bonded to each other as a chain and bonded to the phenolic group of Salen Schiff base by the hydrogen bonding. (C) 2014 Elsevier Ltd. All rights reserved.