Synthesis, Characterization, and Spectroscopic Investigation of New Iron(III) and Copper(II) Complexes of a Carboxylate Rich Ligand and Their Interaction with Carbohydrates in Aqueous Solution

New tetra-iron(III) (K-4[1]center dot 25H(2)O center dot(CH3)(2)CO and K-3[2]center dot 3H(2)O center dot(OH)) and di-copper(II) (Na-3[3]center dot 5H(2)O) complexes as carbohydrate binding models have been synthesized and fully characterized used several techniques including single crystal X-ray crystallography. Whereas K-4[1]center dot 25H(2)O center dot(CH3)(2)CO and Na-3[3]center dot 5H(2)O are completely water-soluble, K-3[2]center dot 3H(2)O center dot(OH) is less soluble in all common solvents including water. The binding of substrates, such as D-mannose, D-glucose, D-xylose, and xylitol with the water-soluble complexes in different reaction conditions were investigated. In aqueous alkaline media, complexes K-4[1]center dot 25H(2)O center dot(CH3)(2)CO and Na-3[3]center dot 5H(2)O showed coordination ability toward the applied substrates. Even in the presence of stoichiometric excess of the substrates, the complexes form only 1:1 (complex/substrate) molar ratio species in solution. Apparent binding constants, pK(app), values between the complexes and the substrates were determined and specific mode of substrate binding is proposed. The pK(app) values showed that D-mannose coordinates strongest to K-4[1]center dot 25H(2)O center dot(CH3)(2)CO and Na-3[3]center dot 5H(2)O. Syntheses, characterizations and detailed substrate binding study using spectroscopic techniques and single crystal X-ray diffraction are reported.