Synthesis, characterisation and ligand properties of novel bi-1,2,3-triazole ligands

Three 1,1'-disubstituted 4,4'-bi-1H-1,2,3-triazoIs [R-bta; R = Bn (1), Ph (2), CH2COOH (3)] have been synthesised as bidentate, nitrogen-based ligands by a Cu-I-catalysed click reaction between 1,3-butadiyne and organic azides. Their ligand properties were investigated by preparation of the complexes [Run(II)(R-bta)(3)]Cl-2 [R = Bn (4), Ph (5), CH2COOH (6)], [(Bn-bta)Cu-I(DPEPhos)] (7) [DPEPhos = bis(2-(diphenylphosphanyl)phenyl) ether] and [(Bn-bta)Re-I(CO)(3)Cl] (8) following standard reaction procedures. All compounds were analysed by elemental analysis, mass spectrometry and NMR, IR, UV/ Vis and luminescence spectroscopy. In addition, the molecular structures of 1-4, 7, and 8 have been determined by X-ray crystallography. In all complexes the Bn-bta acts as a bidentate ligand with structural features comparable to the analogous 2,2'-bipyridine complexes. In their electronic absorption spectra the Ru-II and Re-I complexes exhibit a lowest energy band at around 300 nm, which is substantially higher in energy than in analogous complexes with bpy ligands. All R-bta ligands yield complexes that are not luminescent in solution or in the solid state, which makes these ligands particularly suited for use as spectator ligands.