Filling gaps in the series of noninnocent hetero-1,3-diene chelate ligands: ruthenium complexes of redox-active α-azocarbonyl and α-azothiocarbonyl ligands RNNC(R')E, E = O or S.
Inorg Chem
; 51(11): 6237-44, 2012 Jun 04.
Article
em En
| MEDLINE
| ID: mdl-22594925
ABSTRACT
The series of 4-center unsaturated chelate ligands AâB-CâD with redox activity to yield (-)A-BâC-D(-) in two steps has been complemented by two new combinations RNNC(R')E, E = O or S, R = R' = Ph. The ligands N-benzoyl-N'-phenyldiazene = L(O), and N-thiobenzoyl-N'-phenyldiazene = L(S), (obtained in situ) form structurally characterized compounds [(acac)(2)Ru(L)], 1 with L = L(O), and 3 with L = L(S), and [(bpy)(2)Ru(L)](PF(6)), 2(PF(6)) with L = L(O), and 4(PF(6)) with L = L(S) (acac(-) = 2,4-pentanedionato; bpy = 2,2'-bipyridine). According to spectroscopy and the N-N distances around 1.35 Å and N-C bond lengths of about 1.33 Å, all complexes involve the monoanionic (radical) ligand form. For 1 and 3, the antiferromagnetic spin-spin coupling with electron transfer-generated Ru(III) leads to diamagnetic ground states of the neutral complexes, whereas the cations 2(+) and 4(+) are EPR-active radical ligand complexes of Ru(II). The complexes are reduced and oxidized in reversible one-electron steps. Electron paramagnetic resonance (EPR) and UV-vis-NIR spectroelectrochemistry in conjunction with time-dependent density functional theory (TD-DFT) calculations allowed us to assign the electronic transitions in the redox series, revealing mostly ligand-centered electron transfer [(acac)(2)Ru(III)(L(0))](+) â [(acac)(2)Ru(III)(L(â¢-))] â [(acac)(2)Ru(III)(L(2-))](-)/[(acac)(2)Ru(II)(L(â¢-))](-), and [(bpy)(2)Ru(III)(L(â¢-))](2+)/[(bpy)(2)Ru(II)(L(0))](2+) â [(bpy)(2)Ru(II)(L(â¢-))](+) â [(bpy)(2)Ru(II)(L(2-))](0). The differences between the O and S containing compounds are rather small in comparison to the effects of the ancillary ligands, acac(-) versus bpy.
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Coleções:
01-internacional
Base de dados:
MEDLINE
Idioma:
En
Revista:
Inorg Chem
Ano de publicação:
2012
Tipo de documento:
Article
País de afiliação:
Alemanha