%0 Journal Article %1 Das.2012d %A Das, Amit %A Scherer, Thomas Michael %A Mobin, Shaikh M. %A Kaim, Wolfgang %A Lahiri, Goutam Kumar. %D 2012 %J Chemistry - A European Journal %K azobispyridine complex complex;ruthenium crystal electron ligand noninnocent oxidn prepn relationship ruthenium state structure;structure transfer %N 35 %P 11007-11018, S11007/1-S11007/28 %R 10.1002/chem.201201049 %T Application of a Structure/Oxidation-State Correlation to Complexes of Bridging Azo Ligands %V 18 %X Based on data from \textgreater40 crystal structures of metal complexes with azo-based bridging ligands (2,2'-azobispyridine, 2,2'-azobis(5-chloropyrimidine), azodicarbonyl derivs.), a correlation between the N-N bond lengths (dNN) and the oxidn. state of the ligand (neutral, neutral/back-donating, radical-anionic, dianionic) was derived. This correlation was applied to the anal. of four Ru compds. of 2,2'-azobispyridine (abpy), i.e., the new asym. rac-(acac)2Ru1(m-abpy)Ru2(bpy)2(ClO4)2 (1(ClO4)2), Ru(acac)2(abpy) (2), Ru(bpy)2(abpy)(ClO4)2 (3(ClO4)2), and meso-(bpy)2Ru(m-abpy)Ru(bpy)2(ClO4)3 (4(ClO4)3; acac- = 2,4-pentanedionato, bpy = 2,2'-bipyridine). In agreement with DFT calcns., both mononuclear species 2 and 32+ can be described as Ru(II) complexes of unreduced abpy0, with 1.295(5) \textless dNN \textless 1.320(3) \AA, thereby exhibiting effects from p back-donation. However, the abpy ligand in both the asym. diamagnetic compd. 12+ (dNN = 1.374(6) \AA) and the sym. compd. 43+ (dNN = 1.360(7), 1.368(8) \AA) must be formulated as abpy.bul.-. Remarkably, the addn. of RuII(bpy)22+ to mononuclear RuII(acac)2(abpy0) induces intracomplex electron-transfer under participation of the noninnocent abpy bridge to yield rac-(acac)2Ru1III(m-abpy.-)Ru2II(bpy)22+ (12+) with strong antiferromagnetic coupling between abpy.bul.- and RuIII (DFT (B3LYP/LANL2DZ/6-31G*)-calcd. triplet-singlet energy sepn. ES=1-ES=0 = 11739 cm-1). Stepwise 1-electron transfer was studied for compd. 1n, n = 1-, 0, 1+, 2+, 3+, by UV/visible/NIR spectroelectrochem., EPR spectroscopy, and by DFT calcns. Whereas the first oxidn. of compd. 12+ was found to mainly involve the central ligand to produce an (abpy0)-bridged Class I mixed-valent Ru1IIIRu2II species, the first redn. of compd. 12+ affected both the bridge and Ru1 atom to form a radical complex (1+), with considerable metal participation in the spin-distribution. Further redn. moves the spin towards the Ru2(bpy)2 entity. on SciFinder(R)

@article{Das.2012d, abstract = {Based on data from {\textgreater}40 crystal structures of metal complexes with azo-based bridging ligands (2,2'-azobispyridine, 2,2'-azobis(5-chloropyrimidine), azodicarbonyl derivs.), a correlation between the N-N bond lengths (dNN) and the oxidn. state of the ligand (neutral, neutral/back-donating, radical-anionic, dianionic) was derived. This correlation was applied to the anal. of four Ru compds. of 2,2'-azobispyridine (abpy), i.e., the new asym. rac-[(acac)2Ru1(\textgreek{m}-abpy)Ru2(bpy)2](ClO4)2 ([1](ClO4)2), [Ru(acac)2(abpy)] (2), [Ru(bpy)2(abpy)](ClO4)2 ([3](ClO4)2), and meso-[(bpy)2Ru(\textgreek{m}-abpy)Ru(bpy)2](ClO4)3 ([4](ClO4)3; acac- = 2,4-pentanedionato, bpy = 2,2'-bipyridine). In agreement with DFT calcns., both mononuclear species 2 and 32+ can be described as Ru(II) complexes of unreduced abpy0, with 1.295(5) {\textless} dNN {\textless} 1.320(3) {\AA}, thereby exhibiting effects from \textgreek{p} back-donation. However, the abpy ligand in both the asym. diamagnetic compd. 12+ (dNN = 1.374(6) {\AA}) and the sym. compd. 43+ (dNN = 1.360(7), 1.368(8) {\AA}) must be formulated as abpy.bul.-. Remarkably, the addn. of [RuII(bpy)2]2+ to mononuclear [RuII(acac)2(abpy0)] induces intracomplex electron-transfer under participation of the noninnocent abpy bridge to yield rac-[(acac)2Ru1III(\textgreek{m}-abpy.-)Ru2II(bpy)2]2+ (12+) with strong antiferromagnetic coupling between abpy.bul.- and RuIII (DFT (B3LYP/LANL2DZ/6-31G*)-calcd. triplet-singlet energy sepn. ES=1-ES=0 = 11739 cm-1). Stepwise 1-electron transfer was studied for compd. 1n, n = 1-, 0, 1+, 2+, 3+, by UV/visible/NIR spectroelectrochem., EPR spectroscopy, and by DFT calcns. Whereas the first oxidn. of compd. 12+ was found to mainly involve the central ligand to produce an (abpy0)-bridged Class I mixed-valent Ru1IIIRu2II species, the first redn. of compd. 12+ affected both the bridge and Ru1 atom to form a radical complex (1+), with considerable metal participation in the spin-distribution. Further redn. moves the spin towards the {Ru2(bpy)2} entity. [on SciFinder(R)]}, added-at = {2022-06-15T11:26:56.000+0200}, author = {Das, Amit and Scherer, Thomas Michael and Mobin, Shaikh M. and Kaim, Wolfgang and Lahiri, Goutam Kumar.}, biburl = {https://puma.ub.uni-stuttgart.de/bibtex/2106961bb18332f052a0814c4d97ea1de/huebleriac}, doi = {10.1002/chem.201201049}, interhash = {4285e963fd167cc13199d9358a5905cb}, intrahash = {106961bb18332f052a0814c4d97ea1de}, issn = {0947-6539}, journal = {Chemistry - A European Journal}, keywords = {azobispyridine complex complex;ruthenium crystal electron ligand noninnocent oxidn prepn relationship ruthenium state structure;structure transfer}, number = 35, pages = {11007-11018, S11007/1-S11007/28}, timestamp = {2022-06-15T09:26:56.000+0200}, title = {Application of a Structure/Oxidation-State Correlation to Complexes of Bridging Azo Ligands}, volume = 18, year = 2012 }