Synthesis and characterization of bis bipyridyl ruthenium(II) and osmium(II) complexes with 5,5′-bis-tetrazolate and N,N-bis(tetrazol-5-yl)-amine

• New mixed ligand bis-bipyridyl Ru(II) and Os(II) bound with the five membered di-anionic ligands 5,5′-bis-tetrazolate (bt) and N,N-bis(tetrazol-5-yl)-amine (bta) have been synthesized and characterized.
• 1H; 13C and 2-D NMR techniques are used to verify symmetric coordination of the bidentate bt and bta ligands.
• Compared with the respective [M(bpy)3]+2 species, the lower energy M dπ → bpy π* MLCT absorption spectra and less positive metal centered oxidation potentials are consistent with the bt and bta ligands being π donor ligands.
• The result is corroborated by DFT calculations that show M(bt) and M(bta) centered HOMO and M(bpy) centered LUMO.

New monometallic bis-bipyridyl Ru(II) and Os(II) complexes bonded with high nitrogen content five membered aromatic dianionic ligands 5,5′-bis-tetrazolate (bt) and N,N-bis(tetrazol-5-yl)-amine (bta) have been prepared. NMR results presented are consistent with N1-N1 bidentate chelate bonding to the metal. Absorption spectra display lower energy M dπ → bpy π∗ metal to ligand charge transfer transitions than the respective tris bipyridyl complexes, and the results are consistent with the π donating ability of the bt and bta dianions. Density function theory calculations for all complexes show the HOMO are predominately M dπ-bt π and M dπ-bta π character while the LUMO are M dπ-bpy π∗ character. The M+2/+3 oxidation potentials are less positive, and bpy0/−1 reduction potentials are at more negative potentials than the respective tris bipyridyl complexes, which is consistent with increased electron donation from the bt and bta dianionic ligands to the metal.

New mixed ligand bis-bipyridyl Ru(II) and Os(II) bound with the five membered di-anionic ligands 5,5′-bis-tetrazolate (bt) and N,N-bis(tetrazol-5-yl)-amine (bta) have been synthesized and characterized. Electronic absorption and emission, electrochemical and NMR results are consistent with the bt and bta ligands being π donor ligands.Figure optionsDownload as PowerPoint slide