Intermetallic communication through a 1,3,5-triethynylbenzene connector

The electrochemical behavior of two series of homo- and heterometallic 1,3,5-triethynylbenzene-based transition metal complexes containing [(η²-dppf)(η⁵-C₅H₅)Ru], [(PPh₃)₂(η⁵-C₅H₅)Os], [(^tBu₂bpy)(CO)₃Re], and [(bpy)(CO)₃ClRe] (dppf = 1,1′-bis(diphenylphosphino)ferrocene; ^tBu₂bpy = 4,4′-di-tert-butyl-2,2′-bipyridyl; bpy = 2,2′-bipyridyl-5-yl) building blocks have been studied, showing that there is electronic interaction between the appropriate metal atoms. The electronic absorption spectra reveal high energy bands corresponding to intraligand π → π∗ transitions (bpy, alkynyl) and low energy absorptions which are attributed to MLCT transitions; replacement of ruthenium by osmium results in a blue-shift of the MLCT bands. The associated radical cations of three complexes were in situ generated by chemical oxidation and characterized by continuous wave electron paramagnetic resonance (EPR) investigations in X-band performed at low temperatures.