Ghumaan, Sandeep ; Sarkar, Biprajit ; Patra, Srikanta ; Parimal, Kumar ; van Slageren, Joris ; Fiedler, Jan ; Kaim, Wolfgang ; Lahiri, Goutam Kumar (2004) 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(μ -L - H+)]0 and [{(bpy)2Ru}2(μ-L - H+)]4+ by spectroelectrochemistry and EPR Dalton Transactions (004). pp. 706-712. ISSN 0300-9246
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Official URL: http://xlink.rsc.org/?DOI=b417530a
Related URL: http://dx.doi.org/10.1039/b417530a
Abstract
Crystallographically characterised 3,6-bis(2'-pyridyl)pyridazine (L) forms complexes with {(acac)2Ru} or {(bpy)2Ru2+} via one pyridyl-N/pyridazyl-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 pyridazyl-C5 carbon {L → (L - H+)-} to yield cyclometallated, asymmetrically bridged dinuclear complexes [(acac)2RuIII(μ -L - H+)RuIII(acac)2](ClO4), [2](ClO4), and [(bpy)2RuII(μ -L - H+)RuII(bpy)2](ClO4)3, [4](ClO4)3. The different electronic characteristics of the co-ligands, s donating acac- and π 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 centres (J = -11.5 cm-1) and of a luminescent diruthenium(II) species in [4](ClO4)3. The electrogenerated mixed-valent RuIIRuIII states 2 and [4]4+ with comproportionation constants Kc > 108 are assumed to be localised with the RuIII ion bonded via the negatively charged pyridyl-N/pyridazyl-C5 chelate site of the bridging (L - H+)- ligand. In spectroelectrochemical experiments they show similar intervalence charge transfer bands of moderate intensity around 1300 nm and comparable g anisotropies (g1 - g3≈ 0.5) in the EPR spectra. However, the individual g tensor components are distinctly higher for the p acceptor ligated system [4]4+, signifying stabilised metal d orbitals.
| Item Type: | Article |
|---|---|
| Source: | Copyright of this article belongs to Royal Society of Chemistry. |
| ID Code: | 88395 |
| Deposited On: | 28 Mar 2012 10:00 |
| Last Modified: | 28 Mar 2012 10:00 |
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