Electronic properties of hydroquinone-containing ruthenium complexes in different oxidation states

Electronic structures of copper(II) complexes of tetradentate hydroquinone-containing Schiff bases †

“…45 The instability of our complexed ligands to electrooxidation contrasts with other voltammetric studies of σ-hydroquinonate complexes, for which chemically reversible ligand redox cycles have been reported. 4,12 Our results also contrast with the only other electrochemical study of a hydroquinone-containing Schiff base, namely that of Feringa and co-workers, 5 who prepared a dicopper complex of a bicompartmental ligand with a 2,6-di(formaldimino)-4-hydroxyphenoxy bridging group. In this case no ligand oxidation was detected within the window of the MeCN solvent, which they attributed to the presence of 2 electron-withdrawing carbaldimine substituents on the hydroquinonyl group.…”

“…Indeed, we are aware of only three electrochemical studies of parahydroquinonate complexes, one of which appeared during the course of this work. 4,5,12 We note that H 2 L 1 , H 2 L 2 and a small number of their complexes have been briefly described, although in all cases only basic analytical data (IR, CHN) were reported. 7 Since H 2 L 1 can be thought of as a "non-innocent" analogue of the classic Schiff base ligand H 2 salen, we were interested to examine in more detail the co-ordination chemistry of hydroquinone-containing Schiff ligands of this type.…”

Synthesis, spectroscopic and electrochemical properties of mononuclear and dinuclear bis(bipy)ruthenium(ii) complexes containing dimethoxyphenyl(pyridin-2-yl)-1,2,4-triazole ligands

“…In addition, the pH dependent properties of the 1,2,4-triazole ligands are shown to be useful in applications such as molecular switches. 12 † Electronic supplementary information (ESI) available: figures showing the molecular structures and intermolecular interactions for HL1 and H 2 L2; 1 H COSY NMR spectrum of 2. See http://www.rsc.org/ suppdata/dt/b1/b108728m/ Due to its role as redox relay in biological systems, the hydroquinone/quinone redox couple is of particular interest.…”

Redox Behaviour of Pyrazolyl-Substituted 1,4-Dihydroxyarenes: Formation of the Corresponding Semiquinones, Quinhydrones and Quinones

“…The pyrazolyl rings in 3qh are slightly twisted off the hydroquinone plane with a torsion angle N(2)-N(1)-C(4)-C(6) of −18.1 (6) • . In the crystals of the quinhydrone 1qh, the hydrogen bond formation leads to an infinite molecular chain along the molecular axis [21].…”