¹⁷O MAS NMR Study of the Bonding Mode of Phosphonate Coupling Molecules in a Titanium Oxo-Alkoxo-Phosphonate and in Titania-Based Hybrid Materials

Abstract

17O-enriched phenylphosphonic acid (PhP*O3H2) was prepared from phosphonic acid dichloride and enriched water. This enriched phosphonic acid was used to prepare the titanium oxo-alkoxo-phosphonate Ti4(μ3-*O)(μ2-OPri)3(OPri)5(PhP*O3)3 (1) as a model compound, and titanium oxide/phenylphosphonate hybrids either by sol−gel processing with Ti(OPri)4 or by surface modification of a titania support. For comparison a gel sample was prepared using nonenriched PhPO3H2 and enriched water. The 17O MAS NMR spectra of these 5 solids have been recorded at various magnetic fields (7, 9.4, and 17.6 T) and the isotropic chemical shifts and quadrupolar constants have been determined for the different oxygen sites: PO, P−O−H, P−O−Ti, and OTi x . These spectra give direct evidence for the presence of extensive Ti−O−P bonding in the hybrid materials.

First principles NMR calculations of phenylphosphinic acid C6H5HPO(OH): Assignments, orientation of tensors by local field experiments and effect of molecular motion

“…Solid state NMR is an invaluable tool of investigation for such organophosphorus derived materials, giving a deep insight into chemical bonding. As an example, it has been shown recently [19] that 17 O parameters were extremely sensitive to the bonding mode of phosphonate molecules in hybrid solids. Here, we find a very good agreement between the experimental and calculated data for all nuclei ( 1 H, 13 C, 17 O, 31 P) of phenylphosphinic acid, confirming results dealing with a phosphonic derivative, C 6 H 5 PO(OH) 2 [5].…”

Self-Assembled Monolayers of 12-Mercaptododecylphosphonic Acid on Titania Particles; Application to the Extraction of Heavy Metals

“…The resonances around 28 ppm confirmed the presence of phosphonate units bonded to the surface. Previous studies on the surface modification of TiO 2 by phosphonic acids indicated that the main binding mode to the surface was tridentate (RP(OTi) 3 sites) [1,6,7]. The absence of a sharp resonance at 8 ppm showed that the formation of a layered titanium phosphonate phase by dissolution-precipitation process did not take place.…”

“…Bonding to the surface involves the formation of M-O-P bonds, arising from the coordination of the phosphoryl oxygen to Lewis acid sites and the condensation of the P-OH groups with surface hydroxyl groups M-OH [6].…”

Sol–gel processing of phosphonate-based organic–inorganic hybrid materials

“…However, the natural abundance of 17 O is very low and the preparation of 17 O-enriched phosphonic acids is mandatory. 34) 3. Sol-gel chemistry of phosphonate-based hybrid materials…”