Issue 9, 2002

Synthesis, structure and spectroelectrochemical properties of a dinuclear ruthenium complex exhibiting a strong electronic interaction across a 1,2,4,5-tetrazine bridging ligand

Abstract

The reaction of [Ru(bpy)2(EtOH)2]2+ (bpy = 2,2′-bipyridine) with the potentially bridging ligand 3,6-bis(3,5-dimethylpyrazol-1-yl)-1,4-dihydro-1,2,4,5-tetrazine) (H2L) results in formation of the diruthenium complex [(bpy)2RuII(L)RuII(bpy)2]4+ ([1]4+) in which the dihydrotetrazine unit of H2L has undergone oxidative dehydrogenation to give an aromatic tetrazine unit connecting the two metal centres [L = 3,6-bis(3,5-dimethylpyrazol-1-yl)-1,2,4,5-tetrazine]. The crystal structures of H2L and [1(ClO4)4]·2H2O have been determined. In MeCN solution, complex [1]4+ undergoes two successive one-electron oxidation processes at 1.25 and 1.70 V versus SCE, corresponding to successive Ru(II)/Ru(III) couples, affording a stable mixed-valence Ru(II)/Ru(III) state (Kc = 4 × 107) at intermediate potentials. Four successive ligand-based reduction processes at −0.13, −0.99, −1.58 and −1.94 V versus SCE are also observed, of which the first two are associated with the bridging tetrazine unit and the other two are reductions of the coordinated bipyridine molecules. A UV/VIS/NIR spectroelectrochemical study was carried out on [1]n+ for n = 3–6; the mixed-valence species [1]5+ displays a narrow π–π* transition at 1534 nm, indicative of a class III mixed-valence state. The chemically generated one-electron-reduced species [1]3+ shows an EPR signal (g = 2.0085) characteristic of a ligand-centred radical. [1]4+ is weakly luminescent at 77 K.

Graphical abstract: Synthesis, structure and spectroelectrochemical properties of a dinuclear ruthenium complex exhibiting a strong electronic interaction across a 1,2,4,5-tetrazine bridging ligand

Supplementary files

Article information

Article type
Paper
Submitted
13 Sep 2001
Accepted
11 Feb 2002
First published
03 Apr 2002

J. Chem. Soc., Dalton Trans., 2002, 2097-2101

Synthesis, structure and spectroelectrochemical properties of a dinuclear ruthenium complex exhibiting a strong electronic interaction across a 1,2,4,5-tetrazine bridging ligand

B. Sarkar, R. H. Laye, B. Mondal, S. Chakraborty, R. L. Paul, J. C. Jeffery, V. G. Puranik, M. D. Ward and G. Kumar Lahiri, J. Chem. Soc., Dalton Trans., 2002, 2097 DOI: 10.1039/B108296E

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