Binding Modes of Carboxylate- and Acetylacetonate-Linked Chromophores to Homodisperse Polyoxotitanate Nanoclusters

Abstract

The binding of carboxylate- and acetylacetonate-linked chromophores to homodisperse polyoxotitanate nanoclusters with 17 Ti atoms or more are surveyed and found to be limited to chelate-bidentate and the bridging modes, the former being dominant for the acetylacetonate-linked chromophores, the latter for the carboxylate linkers. Chromophores with acetylacetonate linking groups invariably bind in the chelate mode, whereas carboxylic acid terminated chromophores more frequently are observed to have the bridging mode, with the exception of three cases in which a strong electron-donating substituent is present on two different sensitizers. The calculations for isonicotinateand nitrophenylacetylacetonate functionalized Ti17 clusters show the observed binding modes to correspond to the lower energy functionalized clusters, but do not predict the difference between the cinnamic acid and dimethylaminocinnamic acid binding to Ti17, which are bridging and chelate respectively. Both binding modes were never observed to occur for a single chromophore, even when synthetic conditions were varied. Density of state calculations show broadening and splitting of the chromophore LUMO on complexation due to interaction with the cluster's conduction band, as well as frequent penetration of sensitizer orbitals into the bandgap of the functionalized nanoparticle.

Binding Modes of Salicylic Acids to Titanium Oxide Molecular Surfaces

“…Owing to a larger range of Ti−O bond lengths in TOCs than that in the TiO 2 crystalline phases and the versatility of the TOC structures, the binding modes of functional ligands on the TOCs’ surfaces are also versatile and may encompass those available on TiO 2 surfaces. Although there are many differences between TOCs and TiO 2 , the coordination structures of the ligands on TOCs are likely to occur at distorted surface layers of the bulk materials . In this regard, the binding modes of SSA on TiO 2 surfaces may follow some of the binding modes of SSA‐functionalized TOCs summarized in Table .…”

“…These complexes are isolated as intermediates of TiO 2 during solvothermal preparation of TiO 2 nanomaterials . Their structures have features typical for the Ti/O polymorphs of anatase, but also show distortions more likely to occur in surface layers of TiO 2 NPs . Taking advantage of the crystallographic structures, heterometallic TOCs containing transition‐metal ions have been used as models for studying the structures of dopants and the electronic structures of metal‐doped TiO 2 nanomaterials .…”

Mixed‐Ligand Titanium “Oxo Clusters”: Structural Insights into the Formation and Binding of Organic Molecules and Transformation into Oxide Nanostructures on Hydrolysis and Thermolysis

“…Yet one more reason for attention to titanium oxo species is the recent studies on the influence of ligands on the electronic structure of titanium oxo complexes , . This insight, in combination with the large interest in new solar‐driven energy sources and photocatalysts, has led to the present wave of studies on these compounds .…”

Novel properties and potential applications of functional ligand-modified polyoxotitanate cages

“…[7][8][9] Resembling the fragments of bulk TiO 2 , POT cages of the type [Ti x O y (OR) z ] (OR = alkoxide), consisting of Ti x O y inorganic titanium oxide cores encapsulated within an alkoxide ligand periphery, can be considered as models for studying the structural chemistry of bulk TiO 2 , including its crystal growth mechanism, 10,11 the electronic and structural effects of heterometallic doping, [12][13][14][15][16][17][18][19][20][21] and the influence of surface functional ligand modification. [22][23][24][25][26][27][28][29][30][31] While their excellent solubility in common organic solvents allows POTs to be studied using various standard methods (e.g., NMR, 32-34 mass spectrometry 35 ), single-crystal X-ray diffraction is perhaps the preeminent tool for their characterisation (allowing unambiguous characterisation of structural features which can be related to that of bulk TiO 2 itself). We and others have recently reviewed advances in the area of metal-doped cages (M-POTs), with the emphasis on their structures, photochemistry and applications.…”