Multicomponent Fluorescence Decay Analysis in Intramolecular Excimer Formation With Dipyrenylalkanes

Intramolecular Electron Transfer in Donor−Spacer−Acceptor Systems with Alkylamide Spacers

“…When n > 4 through-space interactions are thought to dominate the electron-transfer process. − The data for the pyrene−dimethylaniline systems display a continuous increase in τ s with increasing spacer length, with a superimposed odd−even effect for n < 10 . The absence of a minimum for n = 5−8 suggests that electron transfer does not require the formation of a strained medium-sized ring as in the case of pyrene excimer formation . Our lifetimes for n = 5 and n = 9 are similar to those for the pyrene−dimethylaniline systems .…”

“…Exciplex fluorescence has been observed by Sakurai et al for the amide-linked (aminoalkyl)naphthalenes (Chart , system V , n = 2−4). The spacer dependence of intramolecular excimer formation in α,ω-bis(pyrenyl)alkanes in methylcyclohexane solution has been thoroughly investigated by Zachariasse et al They report a maximum in the ratio of excimer/monomer fluorescence intensity when n = 3, a minimum for n = 5−8, a second maximum at n = 13, and a gradual decrease for longer spacers. The minimum for n = 5−8 was attributed to the thermochemical strain associated with the formation of medium-sized rings, which is absent in larger rings.…”

Dynamics of short as compared with long poly(acrylic acid) chains hydrophobically modified with pyrene, as followed by fluorescence techniques

“…S1w), compatible with a decrease in the environment polarizability, i.e., exposure to water. The differences between short-and long-sized polymers practically vanish at high pH values (48), where l max = 342.3 AE 0.1 nm for the four polymers, indicating a similar solvent polarizability in all cases. The degree of pyrene labeling has a comparatively smaller effect on l max (0.5 nm red-shift for the more labeled polymers), as expected if the presence of GSD has minor influence on l max .…”

“…Moreover, the values of k a are in the 1-4 Â 10 7 s À1 range, consistent with the values found for intramole-cular excimer formation with 1,n-di(1,1 0 -dipyrenyl)alkanes (n = 12-16) in solvents of similar viscosity. 48 With a parent model compound with 16 atoms covalently linked to two terminal pyrene by way of identical amide groups, the values of the rate constants obtained using the Birks formalism (modified with the presence of GSD) and assuming a t 0 = 230 ns, were: k a = 4.2 Â 10 7 s À1 and k d = 0.26 Â 10 7 s À1 , t E = 55 ns and a = 0.3 (see the ESIw for further details). A direct comparison of these values with the intermolecular rate constant (diffusion-controlled) is not possible due the strong contribution of the chain to the activation energy and its effect on excimer-forming conformations (Hirayama's rule 49 ).…”

Design of a Hydrophobic Fluorescent Probe: An Amide-Linked Bispyrenyl Alcohol

“…The ratio of excimer to monomer fluorescence intensity ( I E / I M ) is dependent upon molecular structure, temperature, and solvent polarity. Zachariasee and co-workers have investigated the chain-length dependence of I E / I M for α,ω-dipyrenylalkanes (Py(CH 2 ) n Py, n = 2−16, 22) in hydrocarbon solvents. Both monomer and excimer fluorescence are observed for all chain lengths except n = 7, for which chain folding is thermodynamically unfavorable.…”