Quenching of n,?*-excited azoalkanes by amines: structural and electronic effects on charge transfer

Exploiting Long-Lived Molecular Fluorescence

“…The intriguing photophysics of fluorazophores has been worked out in great detail [6][7][8][9][10][11] and the fascinating quenching pathways have been investigated through a combination of experimental and theoretical methods [12][13][14]. On the more applied side, fluorazophores have proven to be useful as sensors for antioxidant activity, both in solution [15][16] as well as in membrane-mimetic systems [17], as probes for measuring the kinetics of association with supramolecular systems [18] [19], as tools to investigate the geometries of cyclodextrin inclusion complexes by means of circular dichroism [20] [21], and as probes for the polarizability inside molecular container molecules [22].…”

“…(7), one may use commonly accepted intermolecular diffusion coefficients of 10 -5 cm 2 s -1 in water (the mutual diffusion coefficient in Eqn. (7) corresponds to twice this value), a van-der-Waals reaction radius of 5 Å, and a chain segment length of 5 Å (typical for one peptide unit). The resulting estimates for the intramolecular collision times (1/k coll ) are 0.2 ns for N = 4 and 2.7 ns for N = 20.…”

“…In the third experiment (Scheme 7), we have left the peptide backbone unchanged, but have added cucurbit [7]uril (CB7) to the aqueous solution of the peptide. As demonstrated by NMR experiments, CB7 complexes selectively and quantitatively the pressing background fluorescence through time-resolved detection (see Fig.…”

“…The record for the longest fluorescence lifetime of an organic chromophore in solution lies currently at 1.03 µs (in aerated H 2 O!) [4] and is held by the supramolecular complex (CB7•DBO) between the par- ent azoalkane and cucurbit [7]uril (CB7), a barrel-like organic host molecule [5]. Over the past six years, we have investigated this interesting chromophore in great detail and have prepared several DBO derivatives, which we refer to as fluorazophores ('fluorescent azo chromophores').…”

Investigation of the fluorescence quenching of 2,3-diazabicyclo[2.2.2]oct-2-ene (DBO) by certain substituted uracils

“…Besides the investigation on photophysical and photochemical properties of azochromophore, some work has been conducted in the past with regard to the photo-induced electron transfer (PET) chemistry of azoalkanes [2][3][4]. Among the azoalkanes, DBO (Graphic 1) was used as a first fluorescent probe for the reactivity of antioxidants by Nau [5].…”