%0 Journal Article %1 Ghumaan.2005 %A Ghumaan, Sandeep %A Sarkar, Biprajit %A Patra, Srikanta %A Parimal, Kumar %A van Slageren, Joris %A Fiedler, Jan %A Kaim, Wolfgang %A Lahiri, Goutam Kumar. %D 2005 %J Dalton Transactions %K acac bipyridine bispyridylpyridazine bispyridylpyridazine;electrochem crystal cyclometalated cyclometalated;EPR cyclometalated;mixed cyclometalated;spectroelectrochem redox ruthenium structure valence %N 4 %P 706--712 %R 10.1039/B417530A %T 3,6-Bis(2'-pyridyl)pyridazine (L) and its deprotonated form (L - H+)- as ligands for (acac)2Run+ or (bpy)2Rum+: Investigation of mixed valency in (acac)2Ru2(m-L - H+)0 and (bpy)2Ru2(m-L - H+)4+ by spectroelectrochemistry and EPR %X Crystallog. characterized 3,6-bis(2-pyridyl)pyridazine (L) forms complexes with (acac)2Ru or (bpy)2Ru2+ via one pyridyl-N/pyridazinyl-N chelate site in mononuclear RuII complexes (acac)2Ru(L), 1, and (bpy)2Ru(L)(ClO4)2, 3(ClO4)2. Coordination of a second metal complex fragment is accompanied by deprotonation at the pyridazinyl-C5 carbon L → (L - H+)- to yield cyclometalated, asym. bridged dinuclear complexes (acac)2RuIII(m-L - H+)RuIII(acac)2(ClO4), 2(ClO4), and (bpy)2RuII(m-L - H+)RuII(bpy)2(ClO4)3, 4(ClO4)3. The different electronic characteristics of the co-ligands, s donating acac- and p accepting bpy, cause a wide variation in metal redox potentials which facilitates the isolation of the diruthenium(III) form in 2(ClO4) with antiferromagnetically coupled RuIII centers (J = -11.5 cm-1) and of a luminescent diruthenium(II) species in 4(ClO4)3. The electrogenerated mixed-valent RuIIRuIII states 20 and 44+ with comproportionation consts. Kc \textgreater 108 are assumed to be localized with the RuIII ion bonded via the neg. charged pyridyl-N/pyridazinyl-C5 chelate site of the bridging (L - H+)- ligand. In spectroelectrochem. expts. they show similar intervalence charge transfer bands of moderate intensity around 1300 nm and comparable g anisotropies (g1-g3 $\approx$ 0.5) in the EPR spectra. However, the individual g tensor components are distinctly higher for the p acceptor ligated system 44+, signifying stabilized metal d orbitals. on SciFinder(R)

@article{Ghumaan.2005, abstract = {Crystallog. characterized 3,6-bis(2-pyridyl)pyridazine (L) forms complexes with {(acac)2Ru} or {(bpy)2Ru2+} via one pyridyl-N/pyridazinyl-N chelate site in mononuclear RuII complexes (acac)2Ru(L), 1, and [(bpy)2Ru(L)](ClO4)2, [3](ClO4)2. Coordination of a second metal complex fragment is accompanied by deprotonation at the pyridazinyl-C5 carbon {L → (L - H+)-} to yield cyclometalated, asym. bridged dinuclear complexes [(acac)2RuIII(\textgreek{m}-L - H+)RuIII(acac)2](ClO4), [2](ClO4), and [(bpy)2RuII(\textgreek{m}-L - H+)RuII(bpy)2](ClO4)3, [4](ClO4)3. The different electronic characteristics of the co-ligands, \textgreek{s} donating acac- and \textgreek{p} accepting bpy, cause a wide variation in metal redox potentials which facilitates the isolation of the diruthenium(III) form in [2](ClO4) with antiferromagnetically coupled RuIII centers (J = -11.5 cm-1) and of a luminescent diruthenium(II) species in [4](ClO4)3. The electrogenerated mixed-valent RuIIRuIII states [2]0 and [4]4+ with comproportionation consts. Kc {\textgreater} 108 are assumed to be localized with the RuIII ion bonded via the neg. charged pyridyl-N/pyridazinyl-C5 chelate site of the bridging (L - H+)- ligand. In spectroelectrochem. expts. they show similar intervalence charge transfer bands of moderate intensity around 1300 nm and comparable g anisotropies (g1-g3 $\approx$ 0.5) in the EPR spectra. However, the individual g tensor components are distinctly higher for the \textgreek{p} acceptor ligated system [4]4+, signifying stabilized metal d orbitals. [on SciFinder(R)]}, added-at = {2019-07-15T13:41:23.000+0200}, author = {Ghumaan, Sandeep and Sarkar, Biprajit and Patra, Srikanta and Parimal, Kumar and {van Slageren}, Joris and Fiedler, Jan and Kaim, Wolfgang and Lahiri, Goutam Kumar.}, biburl = {https://puma.ub.uni-stuttgart.de/bibtex/220b6c88565670094c3bcbef336470681/b_schwederski}, doi = {10.1039/B417530A}, interhash = {bf9642938664666aa010b4b520d95d4c}, intrahash = {20b6c88565670094c3bcbef336470681}, issn = {1477-9226}, journal = {Dalton Transactions}, keywords = {acac bipyridine bispyridylpyridazine bispyridylpyridazine;electrochem crystal cyclometalated cyclometalated;EPR cyclometalated;mixed cyclometalated;spectroelectrochem redox ruthenium structure valence}, number = 4, pages = {706--712}, timestamp = {2019-07-15T11:42:10.000+0200}, title = {3,6-Bis(2'-pyridyl)pyridazine (L) and its deprotonated form (L - H+)- as ligands for {(acac)2Run+} or {(bpy)2Rum+}: Investigation of mixed valency in [{(acac)2Ru}2(\textgreek{m}-L - H+)]0 and [{(bpy)2Ru}2(\textgreek{m}-L - H+)]4+ by spectroelectrochemistry and EPR}, year = 2005 }