%0 Journal Article %1 Roy.2012 %A Roy, Sayak %A Sarkar, Biprajit %A Imrich, Hans-Georg %A Fiedler, Jan %A Zalis, Stanislav %A Jimenez-Aparicio, Reyes %A Urbanos, Francisco A. %A Mobin, Shaikh M. %A Lahiri, Goutam Kumar %A Kaim, Wolfgang. %D 2012 %J Inorganic Chemistry %K acac alkylazodicarboxylato bridged crystal diastereoisomer dinuclear isomer;ruthenium isopropylazodicarboxylato meso prepn ruthenium spectroelectrochem structure %N 17 %P 9273--9281 %R 10.1021/ic300809w %T Charged, but Found \dqNot Guilty\dq: Innocence of the Suspect Bridging Ligands RO(O)CNNC(O)OR2- = L2- in (acac)2Ru(m-L)Ru(acac)2n, n = +,0,-,2- %V 51 %X Neutral diastereoisomeric diruthenium(III) complexes, meso-(3) and rac-(acac)2Ru(m-adc-OR)Ru(acac)2 (4; acac- = 2,4-pentanedionato and adc-OR2- = dialkylazodicarboxylato = RO(O)CNNC(O)OR2-, R = tert-Bu or isopropyl), were obtained from electron transfer reactions between Ru(acac)2(MeCN)2 and azodicarboxylic acid dialkyl esters (adc-OR). Isomer 3 (R = iPr) was structurally characterized, revealing two deprotonated and N-N coupled carbamate functions in a reduced dianionic bridge with dN-N = 1.440(5) \AA. A rather short distance of 4.764 \AA was detd. between the two oxidized, antiferromagnetically coupled RuIII centers. The rac isomer 4 (R = iPr) exhibited stronger antiferromagnetic coupling. While the oxidn. of the neutral compds. was fully reversible only for 3 and 4, two well-sepd. (108 \textless Kc \textless 1010) reversible 1-electron redn. steps produced monoanionic intermediates 1--4- with intense (e $\approx$ 3000 M-1 cm-1), broad (Dn1/2 $\approx$ 3000 cm-1) absorptions in the near-IR (NIR) region around 2000 nm. The absence of EPR signals even at 4 K favors the mixed-valent formulation RuII(adc-OR2-)RuIII with innocently behaving bridging ligands over the radical-bridged alternative RuII(adc-OR.bul.-)RuII, a view which is supported by the metal-centered spin as calcd. by d. functional theory (DFT) for the Me ester model system. The 2nd redn. of the complexes causes the NIR absorption to disappear completely, the EPR silent oxidized forms 3+ and 4+, calcd. with asym. spin distribution, do not exhibit near IR (NIR) activity. Azo-bridged diruthenium complex redox systems (acac)2Ru(m-adc-R)Ru(acac)2n (n = +,0,-,2-), (bpy)2Ru(m-adc-R)Ru(bpy)2k (k = 4+,3+,2+,0,2-), and (acac)2Ru(m-dih-R)Ru(acac)2m (m = 2+,+,0,-,2-; dih-R2- = 1,2-diiminoacylhydrazido(2-)) is being compared in terms of electronic structure and identity of the odd-electron intermediates, revealing the dichotomy of innocent vs. non-innocent behavior. on SciFinder(R)

@article{Roy.2012, abstract = {Neutral diastereoisomeric diruthenium(III) complexes, meso-(3) and rac-[(acac)2Ru(\textgreek{m}-adc-OR)Ru(acac)2] (4; acac- = 2,4-pentanedionato and adc-OR2- = dialkylazodicarboxylato = [RO(O)CNNC(O)OR]2-, R = tert-Bu or isopropyl), were obtained from electron transfer reactions between Ru(acac)2(MeCN)2 and azodicarboxylic acid dialkyl esters (adc-OR). Isomer 3 (R = iPr) was structurally characterized, revealing two deprotonated and N-N coupled carbamate functions in a reduced dianionic bridge with dN-N = 1.440(5) {\AA}. A rather short distance of 4.764 {\AA} was detd. between the two oxidized, antiferromagnetically coupled RuIII centers. The rac isomer 4 (R = iPr) exhibited stronger antiferromagnetic coupling. While the oxidn. of the neutral compds. was fully reversible only for 3 and 4, two well-sepd. (108 {\textless} Kc {\textless} 1010) reversible 1-electron redn. steps produced monoanionic intermediates 1--4- with intense (\textgreek{e} $\approx$ 3000 M-1 cm-1), broad (\textgreek{Dn}1/2 $\approx$ 3000 cm-1) absorptions in the near-IR (NIR) region around 2000 nm. The absence of EPR signals even at 4 K favors the mixed-valent formulation RuII(adc-OR2-)RuIII with innocently behaving bridging ligands over the radical-bridged alternative RuII(adc-OR.bul.-)RuII, a view which is supported by the metal-centered spin as calcd. by d. functional theory (DFT) for the Me ester model system. The 2nd redn. of the complexes causes the NIR absorption to disappear completely, the EPR silent oxidized forms 3+ and 4+, calcd. with asym. spin distribution, do not exhibit near IR (NIR) activity. Azo-bridged diruthenium complex redox systems [(acac)2Ru(\textgreek{m}-adc-R)Ru(acac)2]n (n = +,0,-,2-), [(bpy)2Ru(\textgreek{m}-adc-R)Ru(bpy)2]k (k = 4+,3+,2+,0,2-), and [(acac)2Ru(\textgreek{m}-dih-R)Ru(acac)2]m (m = 2+,+,0,-,2-; dih-R2- = 1,2-diiminoacylhydrazido(2-)) is being compared in terms of electronic structure and identity of the odd-electron intermediates, revealing the dichotomy of innocent vs. non-innocent behavior. [on SciFinder(R)]}, added-at = {2022-06-15T11:26:56.000+0200}, author = {Roy, Sayak and Sarkar, Biprajit and Imrich, Hans-Georg and Fiedler, Jan and Zalis, Stanislav and Jimenez-Aparicio, Reyes and Urbanos, Francisco A. and Mobin, Shaikh M. and Lahiri, Goutam Kumar and Kaim, Wolfgang.}, biburl = {https://puma.ub.uni-stuttgart.de/bibtex/209ff5a56f27dac60ba879a0f2d824240/huebleriac}, doi = {10.1021/ic300809w}, interhash = {026ed3be66080dd93f0fb000fb40df4c}, intrahash = {09ff5a56f27dac60ba879a0f2d824240}, issn = {0020-1669}, journal = {Inorganic Chemistry}, keywords = {acac alkylazodicarboxylato bridged crystal diastereoisomer dinuclear isomer;ruthenium isopropylazodicarboxylato meso prepn ruthenium spectroelectrochem structure}, number = 17, pages = {9273--9281}, timestamp = {2022-06-15T09:26:56.000+0200}, title = {Charged, but Found {\dq}Not Guilty{\dq}: Innocence of the Suspect Bridging Ligands [RO(O)CNNC(O)OR]2- = L2- in [(acac)2Ru(\textgreek{m}-L)Ru(acac)2]n, n = +,0,-,2-}, volume = 51, year = 2012 }