A New Dinuclear Ti(IV)−Peroxo−Citrate Complex from Aqueous Solutions. Synthetic, Structural, and Spectroscopic Studies in Relevance to Aqueous Titanium(IV)−Peroxo−Citrate Speciation

Abstract

The wide use of titanium in applied materials has 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. Aqueous reactions of TiCl(4) with citric acid in the presence of H(2)O(2) and neutralizing ammonia afforded expediently the red crystalline material (NH(4))(4)[Ti(2)(O(2))(2)(C(6)H(4)O(7))(2)].2H(2)O (1). Complex 1 was further characterized by UV-vis, FT-IR, FT- and laser-Raman, NMR, and finally by X-ray crystallography. Compound 1 crystallizes in the monoclinic space group P2(1)/n, with a = 10.360(4) A, b = 10.226(4) A, c = 11.478(6) A, beta = 107.99(2) degrees, V = 1156.6(9) A(3), and Z = 2. The X-ray structure of 1 reveals a dinuclear anionic complex containing a Ti(IV)(2)O(2) core. In that central unit, two fully deprotonated citrate ligands are coordinated to the metal ions through their carboxylate moieties in a monodentate fashion. The central alkoxides serve as bridges to the two titanium ions. Also attached to the Ti(IV)(2)O(2) core are two peroxo ligands each bound in a side-on fashion to the respective metal ions. NH(4)(+) ions neutralize the 4- charge of the anion in 1, further contributing to the stability of the derived lattice through H-bond formation. The structural similarities and differences with congener vanadium(V)-peroxo-citrate complexes may point out potential implications in the chemistry of titanium with physiological ligands, when the former is present in a biologically relevant medium.

Application of Water-Soluble Titanium Complexes as Precursors for Synthesis of Titanium-Containing Oxides via Aqueous Solution Processes

“…3.3.3 Binuclear Peroxo Titanium Complexes with Citric Acid: A binuclear citratoperoxotitanate(IV) complex can be obtained by adjusting a given aqueous solution containing TiCl 4 , citric acid (H 4 cit*), and H 2 O 2 to pH µ4.5 by addition of ammonia, 28 in accordance with the reaction in eq 25:…”

A Water‐Soluble Titanium Complex for the Selective Synthesis of Nanocrystalline Brookite, Rutile, and Anatase by a Hydrothermal Method

“…In recent years considerable interest has been devoted to the synthesis and structural characterization of water-soluble titanium(iv) compounds [1][2][3][4] with the aim of developing convenient, nontoxic titanium compounds that can be used as environmentally benign precursors for the solution-based synthesis of titanium oxide and multicomponent inorganic materials containing titanium. This need is dictated by the increasing importance of nanoscale materials, in particular nanosized TiO 2 , which can be used for UV-protective and self-cleaning coatings, [5,6] as an electrode material in dyesensitized solar cells, [6,7] and as a photocatalyst for removal of harmful organic compounds.…”

“…Glycolic acid is also favorable as an industrial reagent due to its availability and low toxicity. (1) and (2).…”

Morphology of water-based chemical solution deposition (CSD) lead titanate films on different substrates: Towards island formation

“…The solutions' colour proves the presence of 1:1 titanium(IV):peroxo complexes. 41,42 During the following addition of ammonia, this burgundy solution slowly changes its colour and becomes yellow-orange at pH 7. For the peroxo free solution (B) on the other hand, a colourless solution is obtained at all stages of the synthesis.…”