Complexation of croconate violet with copper(II). Crystal structures, spectroscopic characterizations and redox studies

The crystal structures of two copper(II) complexes of croconate violet (3,5 -bis(dicyanomethylene)cyclopentane-1,2,4-trionate = L2-) have been determin ed by X-ray methods. Complex 1 consists of mononuclear [CuL2(H2O)(2)](2-) i ons, potassium cations and two crystallisation water molecules. Complex 2 c onsists of mononuclear [CuL3](4-) ions, (NBu4)(+) cations and one half crys tallisation water molecule. In these two complexes, the ligand is coordinat ed in a chelating mode by two adjacent oxygen atoms. The electrochemical be haviour of these complexes is discussed and compared to that of the free cr oconate violet. (C) 2001 Elsevier Science B.V. All rights reserved.