%0 Journal Article %1 Das.2011 %A Das, Amit %A Scherer, Thomas %A Maji, Somnath %A Mondal, Tapan Kumar %A Mobin, Shaikh M. %A Urbanos, Francisco A. %A Jimenez-Aparicio, Reyes %A Kaim, Wolfgang %A Lahiri, Goutam Kumar. %D 2011 %J Inorganic Chemistry %K DFT;prepn acetylacetonate complex complex;ESR complex;electrochem complex;mixed crystal dinuclear pyrazinedicarboxylate reaction redox ruthenium structure valence %N 15 %P 7040--7049 %R 10.1021/ic200530u %T Reductive Approach to Mixed Valency (n = 1-) in the Pyrazine Ligand-Bridged (acac)2Ru(m-L2-)Ru(acac)2n (L2- = 2,5-Pyrazine-dicarboxylate) through Experiment and Theory %V 50 %X The diruthenium(III) complex (acac)2Ru(m-L2-)Ru(acac)2 (1) with acac- = acetylacetonato = 2,4-pentanedionato and a L2- = 2,5-pyrazine-dicarboxylato bridge, has been obtained and structurally characterized as the rac (DD,LL) diastereomer. The RuIIIRuIII configuration in 1 (dRu-Ru = 6.799 \AA) results in a triplet ground state (m = 2.82 mB at 300 K) with a d. functional theory (DFT) calcd. triplet-singlet gap of 10840 cm-1 and the metal ions as the primary spin-bearing centers (Mulliken spin densities: Ru, 1.711; L, 0.105; acac, 0.184). The paramagnetic 1 exhibits broad, upfield shifted 1H NMR signals with d values ranging from -10 to -65 ppm and an anisotropic EPR spectrum (〈g〉 = 2.133, g1 - g3 = Dg = 0.512), accompanied by a weak half-field signal at g = 4.420 in glassy frozen acetonitrile at 4 K. Compd. 1 displays two closely spaced oxidn. steps to yield labile cations. In contrast, two well sepd. reversible redn. steps of 1 signify appreciable electrochem. metal-metal interaction in the RuIIRuIII mixed-valent state 1- (Kc $\approx$ 107). The intermediate 1- shows a weak, broad RuII$\rightarrow$RuIII intervalence charge transfer (IVCT) band at $\sim$1040 nm (e = 380 M-1 cm-1); the DFT approach for 1- yielded Mulliken spin densities of 0.460 and 0.685 for the two metal centers. The monitoring of the nC=O frequencies of the uncoordinated C:O groups of L2- in 1n by IR spectroelectrochem. suggests valence averaging (Ru2.5Ru2.5) in 1- on the vibrational time scale. The mixed-valent 1- displays a rhombic EPR signal (〈g〉 = 2.239 and Dg = 0.32) which reveals non-negligible contributions from the bridging ligand, reflecting a partial hole-transfer mechanism and being confirmed by the DFT-calcd. spin distribution (Mulliken spin d. of -0.241 for L in 1-). The major low energy electronic transitions in 1n (n = 0, 1-, 2-) have been assigned as charge transfer processes with the support of TD-DFT anal. on SciFinder(R)

@article{Das.2011, abstract = {The diruthenium(III) complex [(acac)2Ru(\textgreek{m}-L2-)Ru(acac)2] (1) with acac- = acetylacetonato = 2,4-pentanedionato and a L2- = 2,5-pyrazine-dicarboxylato bridge, has been obtained and structurally characterized as the rac (\textgreek{DD},\textgreek{LL}) diastereomer. The RuIIIRuIII configuration in 1 (dRu-Ru = 6.799 {\AA}) results in a triplet ground state (\textgreek{m} = 2.82 \textgreek{m}B at 300 K) with a d. functional theory (DFT) calcd. triplet-singlet gap of 10840 cm-1 and the metal ions as the primary spin-bearing centers (Mulliken spin densities: Ru, 1.711; L, 0.105; acac, 0.184). The paramagnetic 1 exhibits broad, upfield shifted 1H NMR signals with \textgreek{d} values ranging from -10 to -65 ppm and an anisotropic EPR spectrum (〈g〉 = 2.133, g1 - g3 = \textgreek{D}g = 0.512), accompanied by a weak half-field signal at g = 4.420 in glassy frozen acetonitrile at 4 K. Compd. 1 displays two closely spaced oxidn. steps to yield labile cations. In contrast, two well sepd. reversible redn. steps of 1 signify appreciable electrochem. metal-metal interaction in the RuIIRuIII mixed-valent state 1- (Kc $\approx$ 107). The intermediate 1- shows a weak, broad RuII$\rightarrow$RuIII intervalence charge transfer (IVCT) band at $\sim$1040 nm (\textgreek{e} = 380 M-1 cm-1); the DFT approach for 1- yielded Mulliken spin densities of 0.460 and 0.685 for the two metal centers. The monitoring of the \textgreek{n}C=O frequencies of the uncoordinated C:O groups of L2- in 1n by IR spectroelectrochem. suggests valence averaging (Ru2.5Ru2.5) in 1- on the vibrational time scale. The mixed-valent 1- displays a rhombic EPR signal (〈g〉 = 2.239 and \textgreek{D}g = 0.32) which reveals non-negligible contributions from the bridging ligand, reflecting a partial hole-transfer mechanism and being confirmed by the DFT-calcd. spin distribution (Mulliken spin d. of -0.241 for L in 1-). The major low energy electronic transitions in 1n (n = 0, 1-, 2-) have been assigned as charge transfer processes with the support of TD-DFT anal. [on SciFinder(R)]}, added-at = {2022-06-15T11:26:56.000+0200}, author = {Das, Amit and Scherer, Thomas and Maji, Somnath and Mondal, Tapan Kumar and Mobin, Shaikh M. and Urbanos, Francisco A. and Jimenez-Aparicio, Reyes and Kaim, Wolfgang and Lahiri, Goutam Kumar.}, biburl = {https://puma.ub.uni-stuttgart.de/bibtex/2edc3943ce642be6ad60616a6bc8b6c3d/huebleriac}, doi = {10.1021/ic200530u}, interhash = {d354aaa2e69bd834cab89c22563b2be5}, intrahash = {edc3943ce642be6ad60616a6bc8b6c3d}, issn = {0020-1669}, journal = {Inorganic Chemistry}, keywords = {DFT;prepn acetylacetonate complex complex;ESR complex;electrochem complex;mixed crystal dinuclear pyrazinedicarboxylate reaction redox ruthenium structure valence}, number = 15, pages = {7040--7049}, timestamp = {2022-06-15T09:26:56.000+0200}, title = {Reductive Approach to Mixed Valency (n = 1-) in the Pyrazine Ligand-Bridged [(acac)2Ru(\textgreek{m}-L2-)Ru(acac)2]n (L2- = 2,5-Pyrazine-dicarboxylate) through Experiment and Theory}, volume = 50, year = 2011 }