Thermally and photochemically induced co-ordination change in ruthenium(II) bis(2,2′-bipyridine) complexes containing pyridyltriazole ligands

Homo- and Heteronuclear Ruthenium and Osmium Complexes Containing an Asymmetric Pyrazine-Based Bridging Ligand

“…In addition, the redox potential reported by Meyer and co-workers of 0.88 V for the [Ru(bpy) 2 (pyz)Cl] + moiety and of 0.89 V in the corresponding dinuclear compound is in line with the value observed for the (bpy) 2 RuCl center in this investigation. The only value reported in the literature for a [(bpy) 2 Ru(triazole)Cl] + moiety is substantially lower at 0.66 V . This again indicates that the monodentate unit is coordinated through the pyrazine rather than the triazole ring.…”

“…For this compound evidence for the presence of the coordinated chloride anion is obtained from the H6-bpy proton resonance at 9.73 ppm. A resonance at such low field is indicative of the presence of nonaromatic ligands and is caused by the absence of through-space interaction of this H6 proton with an adjacent aromatic ring . The spectra obtained for this compound were shown to be temperature dependent (see Figure ), and spectra were therefore recorded between 203 and 403 K. At 323 K the H3 and H5 pyrazine-based resonances are broadened considerably and are ill-defined.…”

“…We were however unable to isolate RuCl . Even in the absence of water, a reaction condition that normally favors the formation of species with a [Ru(N 5 )Cl] coordination mode, only Ru was obtained. The osmium analog OsCl was obtained in small yield.…”

Unexpected reversible pyrazine based methylation in a Ru(ii) complex bearing a pyrazin-2′-yl-1,2,4-triazolato ligand and its effect on acid/base and photophysical properties

“…However, the purple colour of the complexes (vide infra) suggests that this is not the case as N-methylated 1,2,4-triazole based complexes of this type are typically orange. 7,18,19 Furthermore, the chemical shifts for the hydrogens of the pyrazine ring were at 9.13 (H 3 ), 7.97 (H 5 ) and 8.32 (H 6 ) ppm for 2a whereas they were at 9.29 (H 3 ), 7.60 (H 5 ) and 8.25 (H 6 ) ppm for 1a (Fig. 3).…”