Comparison of theophyllinato Cu(II) complexes of ethanolamine and diethanolamine Part 2. Structure and thermal study of the dimeric complex with diethanolamine

There is now much evidence that anticancer drugs exert biological action by preferred binding of a transition metal to the N7 sites of the guanine res idues of DNA. In our series of theophyllinato copper(II) complexes containi ng amine ligands, the structural effect of changing from ethanolamine to di ethanolamine is examined. A new mixed ligand copper(II) complex, bis(mu-2-( 2-hydroxyethyl) aminoethanolato-O,N,O') bis(theophyllinato-N7) dicopper(II) (C22H34N10O8Cu2) (1) has been synthesized as model compound from aqueous s olutions of CuSO4, theophylline, and diethanolamine (dea). Its distinct Me2 L2L'(2) structure has been determined by single crystal X-ray diffraction. The centrosymmetric binuclear complex contains two strongly distorted squar e pyramidally (or pseudo-octahedrally) coordinated copper ions bound togeth er by two alkoxo-bridges. The bridging O is a deprotonated oxygen of the mo noalcoholate formed from diethanolamine. Both of the theophyllinate anions take part in N7/O6 chelation in the complex 1, while only one of the theoph yllinate anions is able to perform it in the mononuclear complex (SPY-5-12) -(2-aminoethanol-N) (2-aminoethanol-N,O)bis(theophyllinato-N7)copper(II) di hydrate(2). The two copper(II) centres in 1 are found to be antiferromagnet ically coupled. The combined thermogravimetric and evolved gas detection sh ows that the tridentate alcoholate anions are fragmented and evolved betwee n 125 and 275 degrees C, whilst the degradation of theophyllinate anions be gins at 350 degrees C. Structural, spectroscopic and thermal comparison to the previously published analogous monoethanolamine Cu(II) complex (2) is p resented. (C) 2000 Elsevier Science Ltd All rights reserved.