Photogeneration of titanium(III) from titanium(IV) citrate in aqueous solution

Current interest in the biochemistry of Ti(IV) arises from its widespread use in white pigments and its potential in therapeutic agents. Citrate is known to form strong complexes with Ti(IV). We show here that Ti(III) citrate is generated in a facile manner and in good yield by the action of UV radiation on Ti(IV) citrate in aqueous solution. The Ti(III)-citrate species formed was isolated and characterised by UV–Visible spectroscopy, showing an absorption at 547 nm (ε = 100 M−1 cm−1), and by electron paramagnetic resonance (EPR) spectroscopy giving a resonance at g = 1.949 (linewidth = 60 G) . An X-ray structure of the parent Ti(IV) complex in the form [TiNa3(C6H6O7)2(C6H5O7)(H2O)6.8] · 2H2O is reported along with a study of the reaction of Ti(IV)-citrate with N,N-ethylenebis(o-hydroxytoluene)glycine (EHTG), which was more rapid than those of other related Ti(IV) complexes.