Rhenium Chalcogenide Clusters Containing para-Substituted Phenylacetylide Ligands: Synthesis, Characterization, and Investigation of Substituent Effects on Spectroscopic and Electrochemical Properties

Four new organometallic Re6Se82+-based cluster complexes containing para-substituted phenylacetylide ligands, Re6Se8 (PEt3) 5 (C≡C–C6H4–X) (SbF6) where X = NO2, CO2Me, CH3, and OMe, have been synthesized and fully characterized using 1H, 13C1H and 31P1H NMR, IR, and UV–vis spectroscopy, HRMS, and elemental analysis. Three of these cluster complexes, Re6Se8 (PEt3) 5 (C≡C–C6H4–NO2) +, Re6Se8 (PEt3) 5 (C≡C–C6H4–CO2Me) +, and Re6Se8 (PEt3) 5 (C≡C–C6H4–CH3) + were also characterized via single-crystal X-ray diffraction. Electrochemical studies of these newly reported complexes, as well as the unsubstituted phenylacetylide complex, Re6Se8 (PEt3) 5 (C≡C–C6H5) (SbF6), reveal a correlation between the Hammett parameter σp and the Re6Se83+/2+ couple. The reversibility of this oxidative process is also significantly impacted by the nature of the para-substituent. The photophysical properties of these phenylacetylide cluster complexes (including cis- and trans-Re6Se8 (PEt3) 4 (C≡C–C6H5) 2) in solution and in the powder-phase are reported. Our findings confirm para-substituent effects on emission; however, the trend is opposite to that found in previous studies involving Re6Se82+ clusters containing para-substituted benzonitrile ligands.