Fluorescence quenching profiles

Fig. 16 EM-profile for intramolecular fluorescence quenching in Me2N(CH2)m NMe2 in hexane. (Data from Halpern et al., 1979)...

The two reactions upon which the above comparison was made belong to the Sn2 mechanistic type. There are good indications, however, that the same conclusion applies as well to reactions belonging to different mechanistic types. We have already commented (p. 60) on the close similarity between the EM-profile for intramolecuar fluorescence quenching in... 

A novel approach to determine the solvent concentration profile in a photoresist undergoing dissolution via fluorescence quenching and laser interferometry is introduced. Fluorescence arising from phenanthrene dye labels in a l-/im-thick polymethylmethacrylate)... 

Figure S.6. Schematic representation of So and Si energy profiles for DEWAR formation in TB9A and TB9ACN. 2 The excited state funnel F is very close to the ground stale surface and therefore leads to fluorescence quenching (identifiable with rate constant k). Most of the molecules return to the anthracene form via pathway a, while only a few proceed to the Dewar form (pathway b), because F is placed to the left of the ground state barrier. The steric effect of the tert-butyl substituent is indicated by the broken line. Without this prefolding" of the anthracence form. Dewar formation is not observed. The top part of the figure contains a schematic description of the butterfly-type folding process, while the bottom part contains examples of actual molecules.

The fluorescent behaviour of 6 is quite similar to that observed with the parent non-cyclic system 4. In particular, in the presence of equimolar amounts of either Cu or Ni", sigmoidal /p vs. pH profiles were observed on titration with standard base and complete fluorescence quenching was observed at pH > 4 and pH > 7, respectively. However, 6 presents some unfavourable features that preclude its use as a sensor. 

Bimolecular quenching reactions of excited states are typically represented by the pseudo-first-order reaction kinetics, equation 6a. When a distribution of probe environments exists, the difference between the macroscopic fluorescence decay profile observed and microscopic fluores-... 

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