Study and biological role of the aqueous chemistry of titanium(IV) in the presence of the physiologically relevant citric acid. Synthetic, structural and spectroscopic characterization

The wide use of titanium in applied materials ranging from surgical orthopedic prosthetics to various industrial alloys has prompted pertinent studies targeting the synthesis, spectroscopic, and structural characterization of species of Ti(IV) with the physiologically relevant citric acid. Furthermore, titanium has been increasingly involved in materials affecting the quality of life in humans, which prompted pertinent studies targeting the requisite chemistry of that metal's biological interactions. In order to understand such interactions as well as the requisite titanium aqueous speciation, we launched investigations on the synthesis and spectroscopic and structural characterization of Ti(IV) species with the physiological citric acid. Our investigations focused on two major areas of interest, peroxo and non peroxo species of titanium(IV) with citric acid. Aqueous reactions of TiCl4 with citric acid in the presence of H2O2 and different counter ions afforded expediently the red crystalline material: (NH4)4[Ti2(O2)2(C6H4O7)]2 2H2O (1), [NH]4[6Ti4(O2)4(C6H4O7)2(C6H5O)7)2].6H2O.H2O2 (2) και Κ[6Ti(4O2)2(C6H4O7)2(C6H5O7)2] . 7H2O . KOH (3). On the other hand, aqueous reactions of TiCl 4with citric acid in the absence of H2O2, using different counter ions afforded expediently the following crystalline material: Na[6Ti(C6H5O7)2(C6H4O7)] . 16H2O (4), Na3(NH4)3[Ti(C6H5O7)2(C6H4O7)] . 9H2O (5), (C14H13N2)2[Ti(C6H6O7)]3 . 5H2O (6), Ti(C6H5O7)(2C6H6O7) K7. 10 H2O (7), [Ti(H4citr)3]Cl4·2H2O·EtOH (8). Another crystalline material (NH4)4[Ti(quinic)3](OH)2·6H2O (9), was the result of the similar chemistry of titanium(IV) with quinic acid (also an α-hydroxy acid). The complexes were further characterized by UV-vis, FT-IR, FT- and laser-Raman, NMR (Solid State and Solution), cyclic voltammetry and finally by X-ray crystallography. Such information is vital in trying to delineate the interactions of soluble and bioavailable Ti(IV) forms promoting biological interactions in humans. To this end, chemical properties, structural attributes and speciation links to potential ensuing biological effects are dwelled on