847050-84-4Relevant academic research and scientific papers
Effect of intramolecular π-π and CH-π interactions between ligands on structure, electrochemical and spectroscopic properties of fac-[Re(bpy)(CO)3(PR3)]+ (bpy = 2,2′-bipyridine; PR3 = trialkyl or triarylphosphines)
Tsubaki, Hideaki,Tohyama, Shigeki,Koike, Kazuhide,Saitoh, Hideki,Ishitani, Osamu
, p. 385 - 395 (2007/10/03)
Intramolecular π-π and CH-π interactions between the bpy and PR, ligands fac-[Re(bpy)(CO)3(PR3)]+ affect their structure, and electrochemical and spectroscopic properties. Intramolecular CH-π interaction was observed between the alkyl groups on the phosphine ligand (R = Bu, Et) and the bpy ligand, and intramolecular π-π and CH-π interactions were both observed between the aryl group(s) on the phosphorus ligand (R = p-MeOPh, p-MePh, Ph, p-FPh, OPh) and the bpy ligand, while no such interactions were found in the trialkylphosphite complexes (R = O′Pr, OEt, OMe). The intramolecular interactions distort the pyridine rings of the bpy ligand as long as 3.7 × 10-2 A in crystals. Molecular orbital calculations of the bpy ligand suggest that this distortion decreases the energy gap between its and * orbitals. An absorption band attributed to the π-π*(bpy) transition of the distorted rhenium complexes, measured in a K Br pellet, was red-shifted by 1-5 nm compared to the complexes without the distorted bpy ligand. Even in solution, similar red shifts of the π-π*(bpy) absorption were observed. The redox potential E1/2(bpy/bpy-) of the complexes with the trialkylphosphine and triarylphosphine ligand are shifted positively by 110-120 m V and 60-80 m V respectively, compared with those derived from the electron-attracting property of the phosphorus ligand. In contrast with these properties, three vCO IR bands, which are sensitive to the electron density on the central rhenium because of π-back bonding, were shifted to higher energy, and a Re(I/II)-based oxidation wave was observed at a more positive potential according to the electron-attracting property of the phosphorus ligand.
