Synthesis and characterization of redox active cyrhetrene–triazole click products

We report the synthesis and characterization of two new cyclopentadienyl tricarbonyl rhenium(I) (cyrhetrene) complexes modified with a 1,4-disubstituted 1,2,3-triazole moiety. The two compounds, (η5-[4-phenyltriazol-1-yl]cyclopentadienyl) tricarbonyl rhenium(I), and (η5-[4-(4-aminophenyl)triazol-1-yl]cyclopentadienyl) tricarbonyl rhenium(I), were structurally characterized using 1H and 13C NMR, ATR-IR spectroscopy, UV–vis spectroscopy, mass spectrometry and X-ray crystallography where appropriate. The electrochemical behaviour of these two cyrhetrene–triazole complexes was explored using cyclic voltammetry, whereupon we observed that irreversible oxidation of the pendant 4-substituted-triazole moiety occurs before any electron transfer at the metal centre. This redox behaviour is in stark contrast to that of the analogous manganese(I) cymantrene–triazole derivatives, recently reported by our group.