Unusual, Bifurcated Photoreactivity of a Rhenium(I) Carbonyl Complex of Triethynylphosphine

Preparations of the first metal complexes of triethynylphosphine
(TEP) are described. They are of the type fac-Re(bpy)(CO)3(TEP)+
(1) and cis,trans-[Re(bpy)(CO)2(TEP)L]n+ (CH3CN, n = 1, complex
2; Cl, n = 0, complex 3), where bpy is 2,2‘-bipyridine. Complex
1 displays unusual photochemical behavior compared to analogous
fac-[Re(bpy)(CO)3(PR3)]+ complexes in that it emits from a state
that has π−π* character but undergoes competitive photosubstitution of both TEP and CO. Density functional theory (DFT)/time-dependent DFT calculations predict that the lowest emitting state
should, in fact, have π−π* character.