Structure and thermal behaviour of (SPY-5-12)-(2-aminoethanol-N)(2-aminoethanol-N,O)-bis(theophyllinato)copper(II)dihydrate: A model for DNA-metal interactions

The title compound (1) is obtained by mixing aqueous 2-aminoethanol solutions of theophylline and copper(II) salt. According to the single crystal data the CU2+ ion is pentacoordinated and located in a slightly distorted square pyramidal configuration. Four short Cu-N bonds to two N(7) of the theophyllinate anions and to two nitrogen atoms of a monodentate and a bidentate 2-aminoethanol ligands are almost in the plane, while a longer Cu-O bond to oxygen of the bidentate 2-aminoethanol in the apex at distance 2.350(8) Angstrom A. When heated in air or in an inert atmosphere, 1 undergoes a five-step decomposition process studied by TG, DSC and evolved gas detection (EGD). The solid intermediates of the thermal decomposition were detected by FTIR and powder X-ray diffraction. First the water molecules then the mono-and bidentate 2-aminoethanol ligands are released in the order of their binding energy, showing a strong structure-stability correlation. Afterwards chemical degradation of theophyllinato ligands occurs and is accompanied in air by an intense oxidation process resulting in CuO formation. (C) 1997 Elsevier Science Ltd.