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|Title:||Delving into the complex picture of Ti(IV)-citrate speciation in aqueous media: Synthetic, structural, and electrochemical considerations in mononuclear Ti(IV) complexes containing variably deprotonated citrate ligands|
Kefalas, Evangelos T.
Raptopoulou, Catherine P.
|Type:||Journal Article (Scientific Journal article)|
|Abstract:||The aqueous reaction of TiCl(4) with citric acid at pH similar to 4 (KOH), led to the surprising isolation of a species assembly K(3)[Ti(C(6)H(6)O(7))(2)(C(6)H(5)O(7))] center dot K(4)[Ti(C(6)H(5)O(7))(2)(C(6)H(6)O(7))] center dot 10H(2)O (1). The same system at pH similar to 3 (neocuproine), led to the crystalline material (C(14)H(13)N(2))(2)[Ti(C(6)H(6)O(7))(3)] center dot 5H(2)O (2), while at pH 5.0 (NaOH), afforded Na(3)[Ti(C(6)H(6)O(7))(2)(C(6)H(5)O(7))] center dot 9H(2)O (3). Analytical, spectroscopic and structural characterization of 1, 2 and 3 revealed their distinct nature exemplified by mononuclear complexes bearing variably deprotonated citrates bound to Ti(IV). Solid-state (13)C MAS NMR spectroscopy in concert with solution (13)C and (1)H NMR on 3 provided ample evidence for the existence of bound citrates of distinct coordination mode to the metal ion. Cyclic voltammetry defined the electrochemical signature of complex 2, thereby projecting the physicochemical pro. le of the species formulated by the aforementioned properties. Comparison of cyclic voltammetric data on available discrete Ti(IV)-citrate species depicts the electrochemical pro. le and an E(1/2) value trend of the species in that binary system's aqueous speciation, further substantiating the redox behavior of mononuclear Ti(IV)-citrate species in a pH-sensitive fashion. Collectively, the well-defined discrete species in 1-3 reflect and corroborate a synthetically challenging yet complex pH-specific picture of the aqueous Ti(IV) chemistry with the physiological citric acid, and shed light on the pH-dependent speciation in the binary Ti(IV)-citrate system.|
|Journal Title:||Inorganica Chimica Acta (incorporating Inorganica Chimica Acta Reviews)|
|Subject Category:||Science::Chemistry (General)|
|Keywords:||Ti(IV)-citrate speciation; mononuclear species; aqueous complex synthesis; alpha-hydroxycarboxylate ligands; cyclic voltammetry; Chemistry, Inorganic & Nuclear|
|Other Identifiers:||DOI: http://dx.doi.org/10.1016/j.ica.2007.11.015|
|Journal web Location :||http://www.elsevier.com/locate/ica|
|Rights holder:||© 2007 Elsevier B.V. All rights reserved.|