Synthesis, molecular structure and reactivity of sodium 5-sulfosalicylate dihydrate and sodium[triaqua(5-sulfosalicylato)copper(II)] 2 hemihydrate

The crystal and molecular structure of sodium 5-sulfosalicylate dihydrate, Na[(H(2)Ssal)(H2O)(2)] (1) (H(3)Ssal = 5-sulfosalicylic acid) has been determined through X-ray diffraction analysis. The 5-sulfosalicylate anion has lost the proton at the -SO3H group but retains the usual intermolecular hydrogen bond between phenolic and carboxylic oxygen. The reaction in water of I with [Cu(II)(H2O)(4)]SO4H2O, gives rise to the green sodium[triaqua(5-sulfosalicylato)copper(II)] 2 hemihydrate, Na[(H2O)(3)(Ssal)Cu(II)] 2 x 0.5H(2)O, (2), The 5-sulfosalicylate anion, (Ssal(3-)), coordinates rather unusually in the syn-syn coordination mode since it binds bidentately the Cu(II) ion through the carboxylic and the phenolic oxygens. with Cu(II)-O-carboxylic = 1.909(4) Angstrom and Cu(II)O-phenolic 1.885(4) Angstrom distances. Copper(II) completes its square-planar coordination with two water molecules and in addition, perpendicularly to the square-planar coordination plane, another two water molecules with long bonds are present (Cu(II)-O = 2.518 and 2.912 Angstrom). The green complex 2 reacts easily with adenine in water at pH 7 giving rise to the violet tetraadeninato(diaqua)-bis(copper(II)) dihydrate, [Cu-2(Ade)(4)(H2O)(2)])]. 2H(2)O. (3) (Ade(-) = adeninato monoanion), This complex, that geometrically resembles copper(II) acetate monohydrate, was already described by Sletten. Finally, on the basis of the present results a possible mechanism for the anticancer activity of complex 2 and of other Cu(II)-salicylate complexes is proposed and discussed. (C) 2001 Elsevier Science Ltd. All rights reserved.