Intramolecular Energy Transfer to trans-Stilbene

Abstract

This study examines the photophysics of a series of transition-metal complexes that contain a (diimine)Re I -(CO) 3 (py) chromophore covalently linked to trans-stilbene via a semirigid amide spacer. In this series of complexes moderately exothermic triplet-triplet energy transfer from the 3 dπ* charge-transfer excited state of the diimine-Re chromophore to trans-stilbene is competitive with "normal" radiative and nonradiative decay of the 3 dπ* state. The rate constant for intramolecular energy transfer (k EnT ) was determined as a function of temperature from 190 to 290 K for three complexes in which the driving force (∆E EnT ) varies from ca. -29 to -38 kJ mol -1 . The temperature-dependence data indicate that energy transfer is characterized by a low activation energy (E a e2 kJ mol -1 ) and a low-frequency factor (A ≈10 6 s -1 ). The results are interpreted by a mechanism in which energy transfer from the 3 dπ* state to trans-stilbene occurs at nearly the optimal driving force (i.e., ∆E EnT ≈λ, where λ is the reorganization energy). However, owing to the moderate separation distance between the Re(I) center and trans-stilbene, the exchange coupling matrix element (V TT ) is small, leading to low A values.

Inorganic photoisomerization: the case study of rhenium(i) complexes

“…Slow trans to cis isomerization of the stilbene unit in [Re-(CO) 3 (bpy)(stilbene-amido-pyridine)] + (bpy = 2,2′-bipyridine) has been observed after excitation to the MLCT band 15 whereas efficient isomerization was found upon irradiation at 366 nm (ϕ > 0.5) of fac-[Re(CO) 3 Cl(stpy) 2 ] (stpy = 4-styrylpyridine). 16 Low isomerization quantum yields have been reported for a number of fac-[Re(CO) 3 (stpy)(NN)] + or fac-[Re(CO) 3 (bpe)(NN)] complexes with NN = bpy or phen = 1,10-phenanthroline and bpe = 1,2-bis(4-pyridylethylene).…”

Quenching of Excited Triplet State Hypericin with Energy Acceptors and Donors and Acceptors of Electrons

“…Though comparatively rare in the literature, both unimolecular and bimolecular examples of the inverted region in energy transfer have been reported. [77][78][79][80][81][82][83] There have been theoretical and experimental efforts to link triplet energy transfer and electron transfer. 77,[83][84][85][86] In the weak coupling limit, both are nonadiabatic processes that should follow the golden rule and rates of energy transfer are usually predicted by some variation of eq 11.…”

Attachment of Luminescent Neutral “Pt(pq)(C≡CtBu)” Units to Di and Tri N-Donor Connecting Ligands: Solution Behavior and Photophysical Properties

“…As has been noted before, both species afford similar low energy absorption features. Not unexpectedly, the bpe complex (4b) is not emissive in fluid, probably due to easy nonradiative relaxation by forming a twisted triplet state ( 3 p) [49,[59][60][61]. The remaining complexes display a rather similar intense broad emission centered around 595 nm with negligible influence of the N-donor auxiliary ligand, suggesting a similar emissive state ( Figure 8A, Table 3).…”