A New Organic-Inorganic Hybrid Oxyfluorotitanate [Hgua](2)center dot(Ti(5)O(5)F(12)) as a Transparent UV Filter - Archive ouverte HAL Accéder directement au contenu
Article Dans Une Revue Inorganic Chemistry Année : 2011

A New Organic-Inorganic Hybrid Oxyfluorotitanate [Hgua](2)center dot(Ti(5)O(5)F(12)) as a Transparent UV Filter

Résumé

A new generation UV absorber is obtained by microwave-heating-assisted hydrothermal synthesis: [Hgua]2*(Ti5O5F12). The structure of this hybrid titanium(IV) oxyfluoride is ab initio determined from powder X-ray data by combining a direct space method, Rietveld refinement [orthorhombic, Cmm2, a = 22.410(1) Å, b = 11.191(1) Å, c = 3.802(1) Å], and density functional theory geometry optimization. The three-dimensional network is built up from infinite inorganic layers ∞(Ti5O5F12) separated by guanidinium cations. The theoretical optical gap (3.2 eV) estimated from density of state calculations is in good agreement with the experimental gap (3.3 eV) obtained by UV-vis diffuse reflectivity. The optical absorption is mainly due to O(2p) → Ti(3d) and F(2p) → Ti(3d) transitions at higher energies. The refraction index is low in the visible range (n ≈ 1.9) compared to that of TiO2 and, consequently, [Hgua]2*(Ti5O5F12) shows a good transparency adapted to UV shielding. Under UV irradiation at 254 nm for 40 h, the white microcrystalline powder turns to light purple-gray. This color change is caused by the reduction of TiIV to TiIII, confirmed by magnetic measurements.
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hal-00849350 , version 1 (30-07-2013)

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Jérôme Lhoste, X. Rocquefelte, K. Adil, Remi Dessapt, Stéphane Jobic, et al.. A New Organic-Inorganic Hybrid Oxyfluorotitanate [Hgua](2)center dot(Ti(5)O(5)F(12)) as a Transparent UV Filter. Inorganic Chemistry, 2011, 50 (12), pp.5671. ⟨10.1021/ic200407h⟩. ⟨hal-00849350⟩
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