%0 Journal Article %1 Das.2013 %A Das, Dipanwita %A Agarwala, Hemlata %A Chowdhury, Abhishek Dutta %A Patra, Tuhin %A Mobin, Shaikh M. %A Sarkar, Biprajit %A Kaim, Wolfgang %A Lahiri, Goutam Kumar. %D 2013 %J Chemistry - A European Journal %K NIR benzoquinoneimine cationic complex crystal ligand neutral noninnocent phenylazopyridine prepn;electrochem redox ruthenium structure %N 23 %P 7384--7394 %R 10.1002/chem.201204620 %T Four-Center Oxidation State Combinations and Near-Infrared Absorption in Ru(pap)(Q)2n (Q = 3,5-Di-tert-butyl-N-aryl-1,2-benzoquinonemonoimine, pap = 2-Phenylazopyridine) %V 19 %X The complex series Ru(pap)(Q)2n (1n-4n; n = +2, +1, 0, -1, -2) contains four redox non-innocent entities: one Ru ion, 2-phenylazopyridine (pap), and two o-iminoquinone moieties, Q = 3,5-di-tert-butyl-N-aryl-1,2-benzoquinonemonoimine aryl = C6H5 (1+); m-(Cl)2C6H3 (2+); m-(CH3O)2C6H3 (3+); m-(tert-Bu)2C6H3 (4+). A crystal structure detn. of the representative compd., 1ClO4, established the crystn. of the ctt-isomeric form, i.e., cis and trans with respect to the mutual orientations of O and N donors of two Q ligands, and the coordinating azo N atom trans to the O donor of Q. The sensitive C-O (av.: 1.299(3) \AA), C-N (av.: 1.346(4) \AA) and intra-ring C-C (meta; av.: 1.373(4) \AA) bond lengths of the coordinated iminoquinone moieties in corroboration with the N:N length (1.292(3) \AA) of pap in 1+ establish RuIII(pap0)(Q.bul.-)2+ as the most appropriate electronic structural form. The coupling of three spins from one low-spin Ru(III) (t2g5) and two Q.bul.- radicals in 1+-4+ gives a ground state with one unpaired electron on Q.bul.-, as evident from g = 1.995 radical-type EPR signals for 1+-4+. Accordingly, the DFT-calcd. Mulliken spin densities of 1+ (1.152 for two Q, Ru: -0.179, pap: 0.031) confirm Q-based spin. Complex ions 1+-4+ exhibit two near-IR absorption bands at about l = 2000 and 920 nm in addn. to intense multiple transitions covering the visible to UV regions; compds. 1ClO4-4ClO4 undergo one oxidn. and three sep. redn. processes within $\pm$2.0 V vs. SCE. The crystal structure of the neutral (1-electron reduced) state (2) was detd. to show metal-based redn. and an EPR signal at g = 1.996. The electronic transitions of the complexes 1n-4n (n = +2, +1, 0, -1, -2) in the UV, visible, and NIR regions, as detd. by using spectroelectrochem., were analyzed by TD-DFT calcns. and reveal significant low-energy absorbance (lmax\textgreater1000 nm) for cations, anions, and neutral forms. The exptl. studies in combination with DFT calcns. suggest the dominant valence configurations of 1n-4n in the accessible redox states to be RuIII(pap0)(Q.bul.-)(Q0)2+ (12+-42+)$\rightarrow$RuIII(pap0)(Q.bul.-)2+ (1+-4+)$\rightarrow$RuII(pap0)(Q.bul.-)2 (1-4)$\rightarrow$RuII(pap.bul.-)(Q.bul.-)2- (1--4-)$\rightarrow$RuIII(pap.bul.-)(Q2-)22- (12--42-). on SciFinder(R)

@article{Das.2013, abstract = {The complex series [Ru(pap)(Q)2]n ([1]n-[4]n; n = +2, +1, 0, -1, -2) contains four redox non-innocent entities: one Ru ion, 2-phenylazopyridine (pap), and two o-iminoquinone moieties, Q = 3,5-di-tert-butyl-N-aryl-1,2-benzoquinonemonoimine [aryl = C6H5 (1+); m-(Cl)2C6H3 (2+); m-(CH3O)2C6H3 (3+); m-(tert-Bu)2C6H3 (4+)]. A crystal structure detn. of the representative compd., [1]ClO4, established the crystn. of the ctt-isomeric form, i.e., cis and trans with respect to the mutual orientations of O and N donors of two Q ligands, and the coordinating azo N atom trans to the O donor of Q. The sensitive C-O (av.: 1.299(3) {\AA}), C-N (av.: 1.346(4) {\AA}) and intra-ring C-C (meta; av.: 1.373(4) {\AA}) bond lengths of the coordinated iminoquinone moieties in corroboration with the N:N length (1.292(3) {\AA}) of pap in 1+ establish [RuIII(pap0)(Q.bul.-)2]+ as the most appropriate electronic structural form. The coupling of three spins from one low-spin Ru(III) (t2g5) and two Q.bul.- radicals in 1+-4+ gives a ground state with one unpaired electron on Q.bul.-, as evident from g = 1.995 radical-type EPR signals for 1+-4+. Accordingly, the DFT-calcd. Mulliken spin densities of 1+ (1.152 for two Q, Ru: -0.179, pap: 0.031) confirm Q-based spin. Complex ions 1+-4+ exhibit two near-IR absorption bands at about \textgreek{l} = 2000 and 920 nm in addn. to intense multiple transitions covering the visible to UV regions; compds. [1]ClO4-[4]ClO4 undergo one oxidn. and three sep. redn. processes within $\pm$2.0 V vs. SCE. The crystal structure of the neutral (1-electron reduced) state (2) was detd. to show metal-based redn. and an EPR signal at g = 1.996. The electronic transitions of the complexes 1n-4n (n = +2, +1, 0, -1, -2) in the UV, visible, and NIR regions, as detd. by using spectroelectrochem., were analyzed by TD-DFT calcns. and reveal significant low-energy absorbance (\textgreek{l}max{\textgreater}1000 nm) for cations, anions, and neutral forms. The exptl. studies in combination with DFT calcns. suggest the dominant valence configurations of 1n-4n in the accessible redox states to be [RuIII(pap0)(Q.bul.-)(Q0)]2+ (12+-42+)$\rightarrow$[RuIII(pap0)(Q.bul.-)2]+ (1+-4+)$\rightarrow$[RuII(pap0)(Q.bul.-)2] (1-4)$\rightarrow$[RuII(pap.bul.-)(Q.bul.-)2]- (1--4-)$\rightarrow$[RuIII(pap.bul.-)(Q2-)2]2- (12--42-). [on SciFinder(R)]}, added-at = {2022-06-15T11:26:56.000+0200}, author = {Das, Dipanwita and Agarwala, Hemlata and Chowdhury, Abhishek Dutta and Patra, Tuhin and Mobin, Shaikh M. and Sarkar, Biprajit and Kaim, Wolfgang and Lahiri, Goutam Kumar.}, biburl = {https://puma.ub.uni-stuttgart.de/bibtex/270fce824fda0f6fb774acace025492ac/huebleriac}, doi = {10.1002/chem.201204620}, interhash = {7b26d93de9d61542310b56969fb5a18d}, intrahash = {70fce824fda0f6fb774acace025492ac}, issn = {0947-6539}, journal = {Chemistry - A European Journal}, keywords = {NIR benzoquinoneimine cationic complex crystal ligand neutral noninnocent phenylazopyridine prepn;electrochem redox ruthenium structure}, number = 23, pages = {7384--7394}, timestamp = {2022-06-15T09:26:56.000+0200}, title = {Four-Center Oxidation State Combinations and Near-Infrared Absorption in [Ru(pap)(Q)2]n (Q = 3,5-Di-tert-butyl-N-aryl-1,2-benzoquinonemonoimine, pap = 2-Phenylazopyridine)}, volume = 19, year = 2013 }