Syntheses, crystal structure, and photochromic properties of a new stable Ti(iv) complex

Abstract

A novel titanium complex with photochromism, with the formula [Ti(IV)(PDA)₂]·EtOH (Ti–PDA), was synthesized using a one-step in situ solvothermal method with a mixture of Ti(ⁱPrO)₄ and [2,2′-bipyridine]-6,6′-dicarboxylic acid (H₂PDA). Ti–PDA displays a three-dimensional structure due to the comprising π⋯π contacts between the pyridine rings. Additionally, the crystals of Ti–PDA rapidly exhibit a photochromic effect from colourless to dark blue after being exposed to a xenon lamp or UV lamp (365 nm). Interestingly, this reversible transformation of color can be achieved using oxidant H₂O₂. Meanwhile, under the illumination of a xenon lamp and with the assistance of H₂O₂, the microcrystals of Ti–PDA in an aqueous dispersion can rapidly undergo photodegradation of methyl orange.