325818-81-3Relevant academic research and scientific papers
Tuning the excited-state properties of [M(SnR3)2(CO)2(α-diimine)] (M = Ru, Os; R = Me, Ph)
Van Slageren,Stufkens
, p. 277 - 285 (2001)
The influences of R, the α-diimine, and the transition metal M on the excited-state properties of the complexes [M(SnR3)2(CO)2(α-diimine)] (M = Ru, Os; R = Ph, Me) have been investigated. Various synthetic routes were used to prepare the complexes, which all possess an intense, sigma-bond-to-ligand charge-transfer transition in the visible region between a σ(Sn-M-Sn) and a π*(α-diimine) orbital. The resonance Raman spectra show that many bonds are only weakly affected by this transition. The room-temperature time-resolved absorption spectra of [M(SnR3)2(CO)2(dmb)] (M = Ru, Os; R = Me, Ph; dmb = 4,4′-dimethyl-2,2′-bipyridine) show the absorptions of the radical anion of dmb, in line with the SBLCT character of the lowest excited state. The excited-state lifetimes at room temperature vary between 0.5 and 3.6 μs and are mainly determined by the photolability of the complexes. All complexes are photostable in a glass at 80 K, under which conditions they emit with very long lifetimes. The extremely long emission lifetimes (e.g., τ = 1.1 ms for [Ru(SnPh3)2(CO)2(dmb)]) are about a thousand times longer than those of the 3MLCT states of the [Ru(Cl)(Me)(CO)2(α-diimine)] complexes. This is due to the weak distortion of the former complexes in their 3SBLCT states as seen from the very small Stokes shifts. Remarkably, replacement of Ru by Os hardly influences the absorption and emission energies of these complexes; yet the emission lifetime is shortened because of an increase of spin - orbit coupling. The quantum yield of emission at 80 K is 1-5% for these complexes, which is lower than might be expected on the basis of their slow nonradiative decay.
