Trifluoropropynyl as a Surrogate for the Cyano Ligand and Intense, Room-Temperature, Metal-Centered Emission from Its Rh(III) Complex

The trifluoropropynyl ligand −CCCF3 was studied as a possible surrogate for the cyano ligand. Complexes of the type trans-[M(cyclam)(CCCF3)2]OTf (where M = Cr3+, Co3+, and Rh3+; OTf = trifluoromethanesulfonate) were prepared and then characterized by electronic spectroscopy and by cyclic voltammetry for the Co3+ complex. The UV–vis spectra for all three bear a remarkable similarity to that of the trans-M(cyclam)(CN)2 + cations. The trifluoropropynyl complex of Co3+ shows electrochemical behavior nearly identical with that of its dicyano analogue. Metal-centered phosphorescence from the Rh(III) complex in room-temperature aqueous solution has a quantum yield of 0.12 and a lifetime of 73 μs, nearly 10 times higher than those of its dicyano analogue.