cis-[PtBr2{PPh2(4-catechol)}2]: synthesis, crystal structure, and computational modelling of its binding to nanocrystalline TiO2

Abstract

The complex cis-[PtBr₂{PPh₂(4-catechol)}₂] 1 has been synthesized by cleavage of the four methyl groups from cis-[PtCl₂{PPh₂(4-veratrole)}₂] using BBr₃, followed by work-up in the presence of excess bromide. An X-ray crystal structure of 1·(ethanol)₂ confirms that the two catechol rings are adjacent to each other and approximately parallel, and therefore well structured to act as double bidentate ligands for adjacent metal atoms on the surface of a nanocrystal. The crystal packing of 1·(ethanol)₂ involves intermolecular hydrogen-bonding interactions and a parallel fourfold phenyl embrace between PPh₂ moieties. Density functional calculations have demonstrated that conformational variability of the aryl rings in cis-[PtBr₂{PPh₂(4-catechol)}₂] is energetically feasible, and two conformations of cis-[PtBr₂{PPh₂(4-catechol)}₂] as a complex ligand for Ti atoms on the various surfaces of the anatase and rutile structures of TiO₂ have been assessed for geometrical commensurability. Three structural models for adsorbates of cis-[PtBr₂{PPh₂(4-catechol)}₂] on TiO₂ are developed for anatase (110), anatase (101), and rutile (001).