Substituted 2,2′-bipyridines as ligands. preparation and characterization of 4,4′-disubstituted 2,2′-bipyridine derivatives of the hexacarbonyls of chromium, molybdenum and tungsten

Electrocatalytic CO2 reduction by M(bpy-R)(CO)4 (M = Mo, W; R = H, tBu) complexes. Electrochemical, spectroscopic, and computational studies and comparison with group 7 catalysts

Group 6 M(bpy-R)(CO)₄ (M = Mo, W; R = H, tBu) complexes have been found to be competent electrocatalysts for CO₂ reduction to CO.

Photophysical Properties of Ruthenium Bipyridine (4-Carboxylic acid-4‘-methyl-2,2‘-bipyridine) Complexes and Their Acid−Base Chemistry

Photophysical properties such as absorption and emission spectra, lifetimes, and redox potentials of eight ruthenium complexes, Ru(LL)2(MebpyCOOH)2+, where LL represents bpy, phen, Me2bpy, Me4bpy, (MeO)2bpy, (EtO)2bpy, Cl2bpy, and NO2phen, have been measured. The acid dissociation constants of ground and excited states have been determined. The ground-state pKa values were obtained from the pH dependence of the complex absorbance changes. The excited-state pKa* values were extracted from the emission titration curve and corrected for the excited-state lifetime of both protonated and deprotonated species. The largest DeltapKa, pKa*-pKa, found for Ru(Me2bpy)2(MebpyCOOH)2+ and Ru(Me4bpy)2(MebpyCOOH)2+ of 1.7 indicate that MebpyCOOH gains most of the MLCT excited-state electron. The big negative DeltapKa found for Ru(Cl2bpy)2(MebpyCOOH)2+, -4.2, clearly indicates the metal-to-ligand charge transfer to the Cl2bpy ligands.

Spectroscopy and electrochemistry of new 6,6′-disubstituted-4,4′-bipyrimidine molybdenum(0) and tungsten(0) tetracarbonyl complexes

A new family of tetracarbonyl molybdenum(0) and tungsten(0) complexes based on new 6,6′-disubstituted-4,4′-bipyrimidine ligands was synthesized and characterized. The visible region of the absorption spectrum of each complex is dominated by a metal-to-ligand charge transfer band significantly lower in energy than the corresponding transition in 2,2′-bipyridine tetracarbonyl metal complexes. The 6,6′-substituents create a larger π-electronic system in the substituted bipyrimidines and are consequently better π acceptors than even the parent 4,4′-bipyrimidine. The absorption bands are shifted bathochromically with a decrease in solvent polarity.Key words: molybdenum and tungsten, nitrogen ligands, tetracarbonyl metal complexes, absorption spectroscopy, electrochemistry.

Synthesis of 4,4′-di(mercaptomethylthio)-2,2′-bipyridine and in situ spectroscopic characterization of its electropolymerized films

Reported are the synthesis of 4,4 ‘-di(mercaptomethylthio)-2,2 ‘-bipyridine and its electrochemical polymerization in acetonitrile, producing films which are strongly adsorbed onto gold electrodes.

A, Butler IS. Article

Pressure-tuning infrared and Raman spectroscopic studies were performed on (2,2'-bipyridine)tetracarbonyl-chromium(0), Cr(CO)4(bpy). Previous bpy ring mode assignments were confirmed with new assignments offered by examination of the pressure-induced alterations in the vibrational spectra. The electron-density distribution of the bipyridyl ligand (and consequently, the electron-donating ability to the central metal) is modulated by the application of pressure. The pressure dependence of the carbonyl moieties reveals that the bipyridyl ligand can accommodate a significant portion of the molecular compressibility at higher pressures.Key words: infrared, Raman, pressure, Cr(CO)4(bpy), metal carbonyl.