This submission was created using the RSC Article Template (DO NOT DELETE THIS TEXT) (LINE INCLUDED FOR SPACING ONLY -DO NOT DELETE THIS TEXT)A series of [Ru(bipy) 2 L] + and [Ru(phen) 2 L] + complexes where L is 2-[5-(3,4-dimethoxyphenyl)-4H-1,2,4-triazol-3-yl]pyridine (HL1) and 4-(5-pyridin-2-yl-4H-1,2,4-triazol-3-yl)benzene-1,2-diol (HL2) are reported. The compounds obtained have been characterised using x-ray crystallography, NMR, UV/Vis and emission spectroscopies. Partial deuteriation is used to determine the nature of the emitting state and to simplify the NMR spectra. The acid-base properties of the compounds are also investigated. The electronic structure of the HL1 complex is examined using ZINDO. Electro and spectroelectrochemical studies on [Ru(bipy) 2 (L2)] + suggest that proton transfer between the catechol and triazole moieties on L2 takes place upon oxidation of the L2 ligand.
IntroductionThe hydroquinone/quinone redox couple plays an essential role as electron mediator in the charge separation processes in photosynthesis. 1 As a result there has been extensive interest in the redox properties of quinone containing metal complexes and in their potential to act as electron acceptors or donors. 2 In these studies catechol based ligands are coordinated to a wide range of metals. 3 Much less attention has been paid to the interaction between metal centres and pendent hydroquinone/quinone groupings, although such materials may participate in light induced electron transfer reactions. 4 We are presently involved in a systematic study of the electrochemical and photophysical properties of ruthenium complexes containing pendent hydroquinone/quinones. 5,6 In an earlier study on ruthenium polypyridyl complexes incorporating pyridyltriazole ligands with free hydroquinone groupings, electrochemically induced intramolecular protonation of the ruthenium centre was observed upon oxidation of the hydroquinone moiety. 6 In this contribution the synthesis and deprotection of the methoxy complexes [Ru(bipy) 2 (L1)]PF 6 .5H 2 O and [Ru(phen) 2 (L1)]PF 6 .2H 2 O (where HL1 is 2-[5-(3,4-dimethoxyphenyl)-4H-1,2,4-triazol-3-yl]pyridine) to produce the catechol type complexes with the ligand HL2 4-(5-Pyridin-2-yl-4H-1,2,4-triazol-3-yl)benzene-1,2-diol are described (for ligand structures see Figure 1). The partially deuteriated analogues [Ru(d 8 -bipy) 2 (L1)] + and [Ru(d 8 -phen) 2 (L1)] + are also described. The materials obtained have been characterised by X-ray crystallography and 1 H-NMR spectroscopy. The absorption, emission, photophysical and electrochemical properties of the complexes are also examined. To aid interpretation of the results obtained, semi-empirical calculations using ZINDO were carried out on [Ru(bipy) 2 (HL1)] 2+ and [Ru(bipy) 2 (L1)] + , where the triazole moieties are in the protonated and deprotonated states respectively.
ExperimentalAll synthetic reagents were of commercial grade and used without further purification. The solvents used in spectroscopic measurements were HPLC grade. Perdeute...