849337-67-3Relevant academic research and scientific papers
3,6-Bis(2′-pyridyl)pyridazine (L) and its deprotonated form (L H +)- as ligands for {(acac)(2)Run+} or {(bpy)2Rum+}: Investigation of mixed valency in [{(acac)(2)Ru}(2)(μ-L - H+)]0 and [{(bpy)2Ru}2(μ-L - H+)]4+ by spectroelectrochemistry and EPR
Ghumaan, Sandeep,Sarkar, Biprajit,Patra, Srikanta,Parimal, Kumar,Van Slageren, Joris,Fiedler, Jan,Kaim, Wolfgang,Lahiri, Goutam Kumar
, p. 706 - 712 (2007/10/03)
Crystallographically characterised 3,6-bis(2′-pyridyl)pyridazine (L) forms complexes with {(acac)2Ru} or {(bpy)2Ru 2+} via one pyridyl-N/pyridazyl-N chelate site in mononuclear Ru II 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](ClO 4), and [(bpy)2RuII(μ-L - H +)RuII(bpy)2](ClO4)3, [4](ClO4)3. The different electronic characteristics of the co-ligands, σ 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 > 10 8 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 - g 3 ≈ 0.5) in the EPR spectra. However, the individual g tensor components are distinctly higher for the π acceptor ligated system 4+, signifying stabilised metal d orbitals. The Royal Society of Chemistry 2005.
