The synthesis and characterisation of Rh(III) complexes with pyridyl triazole ligands

A series of Rh(III) mixed ligand polypyridine type complexes have been prepared. Complexes of the form [Rh(L)2(L′)]n+, where n=2/3, L=2,2′-bipyridine (bpy)/1,10-phenanthroline (phen) and L′=3-(pyridin-2-yl)-1,2,4-triazole (Hpytr), 1-methyl-3-(pyridin-2-yl)-1,2,4-triazole (1M3pytr), 4-methyl-3-(pyridin-2-yl)-1,2,4-triazole (4Mpytr), 3,5-bis(pyridin-2-yl)-1,2,4-triazole (Hbpt), 4-amino-3,5-bis(pyridin-2-yl)-1,2,4-triazole (NH2bpt) and 3-(pyridin-2-yl)-5-phenyl-1,2,4-triazole (HPhpytr), have been prepared and their synthesis and characterisation are reported. Crystals of [Rh(bpy)2(Phpytr)](PF6)2 and [Rh(phen)2(NHbpt)](PF6)2 were obtained and their structures determined. Analysis of X-ray crystallographic data showed that coordination of the metal centre in [Rh(phen)2(NHbpt)](PF6)2 occurs via the amine moiety and a nitrogen of the pyridine ring. NMR studies illustrated that coordination to the NH2bpt ligand was also possible via a nitrogen of the triazole ring and the pyridine ring forming the complex [Rh(phen)2(NH2bpt)](PF6)3. The absorption and emission properties of the complexes studied were found to be π–π* in nature and preliminary evidence suggests that all complexes with the exception of [Rh(phen)2(NHbpt)](PF6)2 and [Rh(bpy)2(NHbpt)](PF6)2 are dual emitting at 77 K.