SUPRAMOLECULAR DONOR-ACCEPTOR COMPLEXES OF DICHLOROFLUORESCEIN ANDcis- ANDtrans-4,4?-(N,N?-DIMETHYLPYRIDINIUM)ETHYLENE

The synthesis, characterization, and X-ray crystal structures of [Re(diimine)(CO)(3)(dpe)](PF(6)) (dpe = 1,2-di(4-pyridyl)ethylene) compounds are reported. The cis-dpe complexes exhibit yellow luminescence after UV excitation, whereas the trans-dpe counterparts are nonluminescent. The luminescence quantum yields of the cis-dpe complexes are strongly dependent on the identity of the diimine ligand. Irradiation (350 nm) of the trans-dpe complexes induces trans --> cis dpe-ligand isomerization with quantum yields on the order of 0.2, and this process leads to an on-switching of yellow luminescence. After long 350-nm irradiation times, a steady state composed of roughly 70% cis- and 30% trans-dpe complexes is reached. The reverse cis --> trans photoisomerization reaction is induced by irradiating the cis-dpe complexes at 250 nm, switching off the yellow luminescence. For 250-nm excitation, photodecomposition of the [Re(diimine)(CO)(3)(dpe)](+) complexes competes efficiently with photoisomerization.

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“…cis-dpe. A solution of trans-dpe (0.05 M) and benzil (0.5 M) in CH 2 Cl 2 was irradiated [75 W Xe lamp (Oriel)] for 4 h under N 2 atmosphere …”

Section: Methodsmentioning

confidence: 99%

Photoswitchable Luminescence of Rhenium(I) Tricarbonyl Diimines

et al. 2004

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“…This is in contrast to known linear fluorescein derivatives that have xanthene-benzyl mean average planes that are between 85 and 901. [40][41][42][43][44] The crystal structure of 1 also shows the aromatic moieties are planar, unlike other crystallographic fluorescein examples in which the xanthene is puckered. 45,46 A weak intramolecular C-HÁ Á Áp interaction is also present in the macrocycle, contributing to the observed conformation.…”

Section: Resultsmentioning

confidence: 95%