%0 Journal Article %1 Poppe.1993b %A Poppe, Juergen %A Kaim, Wolfgang %A Ben Altabef, Aida %A Katz, Nestor E. %D 1993 %J Journal of the Chemical Society, Perkin Transactions 2: Physical Organic Chemistry %K ESR ammineruthenium complex ligand radical %N 11 %P 2105--2108 %T EPR characteristics of radical complexes with coordinated ammineruthenium(II) fragments. Evidence for the metal-to-ligand charge transfer (MLCT) nature of the low-lying excited states in precursor complexes %X The 1st EPR study of 1-electron reduced ammineruthenium(II) complexes is reported, based on the reversible redn. of the following precursors: [(mpz)Ru(NH3)5]3+ (mpz = N-methylpyrazinium),[(bpym)Ru(NH3)4]2+ (bpym = 2,2'-bipyrimidine), [(bptz)Ru(NH3)4]2+ and (μ-bptz)[Ru(NH3)4]24+[bptz = 3,6-bis(2-pyridyl)-1,2,4,5-tetrazine]. The partially resolved EPR spectra of [(mpz·)-Ru(NH3)5]2+ and [(bptz)Ru(NH3)4]+ confirm unambiguously that the unpaired electron resides mainly in the p system of the unsatd. ligand, however, the spin distribution and the 99,101Ru isotope coupling reveal nonnegligible contributions from the metal 4d orbitals to the singly occupied MO. The 2 other 1-electron reduced compds. exhibit less well-resolved EPR spectra but are also RuII complexes of radical ligands as judged by their g anisotropy in comparison to the RuIII contg. oxidized forms. Distinctly different EPR characteristics of the oxidized and reduced forms support the MLCT formulation of low-lying excited states in the precursor compds. The effect of the RuII ammine complex fragments on the EPR characteristics of the org. radical ligands is compared to that of other low spin d6 systems. [on SciFinder(R)]

@article{Poppe.1993b, abstract = {The 1st EPR study of 1-electron reduced ammineruthenium(II) complexes is reported, based on the reversible redn. of the following precursors: [(mpz)Ru(NH3)5]3+ (mpz = N-methylpyrazinium),[(bpym)Ru(NH3)4]2+ (bpym = 2,2'-bipyrimidine), [(bptz)Ru(NH3)4]2+ and {(μ-bptz)[Ru(NH3)4]2}4+[bptz = 3,6-bis(2-pyridyl)-1,2,4,5-tetrazine]. The partially resolved EPR spectra of [(mpz·)-Ru(NH3)5]2+ and [(bptz)Ru(NH3)4]+ confirm unambiguously that the unpaired electron resides mainly in the \textgreek{p} system of the unsatd. ligand, however, the spin distribution and the 99,101Ru isotope coupling reveal nonnegligible contributions from the metal 4d orbitals to the singly occupied MO. The 2 other 1-electron reduced compds. exhibit less well-resolved EPR spectra but are also RuII complexes of radical ligands as judged by their g anisotropy in comparison to the RuIII contg. oxidized forms. Distinctly different EPR characteristics of the oxidized and reduced forms support the MLCT formulation of low-lying excited states in the precursor compds. The effect of the RuII ammine complex fragments on the EPR characteristics of the org. radical ligands is compared to that of other low spin d6 systems. [on SciFinder(R)]}, added-at = {2022-06-15T11:26:56.000+0200}, author = {Poppe, Juergen and Kaim, Wolfgang and {Ben Altabef}, Aida and Katz, Nestor E.}, biburl = {https://puma.ub.uni-stuttgart.de/bibtex/2f7903cf022f6cd92106e1e69abd9884e/huebleriac}, interhash = {22a7c46ebdbdeeb8f89865d765091465}, intrahash = {f7903cf022f6cd92106e1e69abd9884e}, issn = {0300-9580}, journal = {Journal of the Chemical Society, Perkin Transactions 2: Physical Organic Chemistry}, keywords = {ESR ammineruthenium complex ligand radical}, number = 11, pages = {2105--2108}, timestamp = {2022-06-15T09:26:56.000+0200}, title = {EPR characteristics of radical complexes with coordinated ammineruthenium(II) fragments. Evidence for the metal-to-ligand charge transfer (MLCT) nature of the low-lying excited states in precursor complexes}, year = 1993 }