Reverse micelles coumarin

FIG. 4 Time-resolved fluorescence Stokes shift of coumarin 343 in Aerosol OT reverse micelles, (a) normalized time-correlation functions, C i) = v(t) — v(oo)/v(0) — v(oo), and (b) unnormalized time-correlation functions, S i) = v i) — v(oo), showing the magnitude of the overall Stokes shift in addition to the dynamic response, wq = 1.1 ( ), 5 ( ), 7.5 ( ), 15 ( ), and 40 (O) and for bulk aqueous Na solution (A)- Points are data and lines that are multiexponential fits to the data. (Reprinted from Ref 38 with permission from the American Chemical Society.)... 

Extensive studies in reverse micelles revealed a similar water distribution [127-130], which is consistent with the distinct water model proposed by Finer [150]. For example, when the molar ratio (wo) of water to the surfactant is 6.8 in lecithin reverse micelles with a corresponding diameter of 37 A, three solvation time scales of 0.57 (13%), 14 (25%), and 320 ps (62%) were observed using coumarin 343 as the molecular probe. At w0 = 4.8 with a 30-A water core diameter, only a single solvation dynamic was observed at 217 ps, which indicates that all water molecules are well ordered inside the aqueous pool. The lecithin in these reverse micelles have charged headgroups, which have much stronger interactions with water than the neutral headgroups of monoolein in the... 

Proton transfer dynamics of photoacids to the solvent have thus, being reversible in nature, been modelled using the Debye-von Smoluchowski equation for diffusion-assisted reaction dynamics in a large body of experimental work on HPTS [84—87] and naphthols [88-92], with additional studies on the temperature dependence [93-98], and the pressure dependence [99-101], as well as the effects of special media such as reverse micelles [102] or chiral environments [103]. Moreover, results modelled with the Debye-von Smoluchowski approach have also been reported for proton acceptors triggered by optical excitation (photobases) [104, 105], and for molecular compounds with both photoacid and photobase functionalities, such as lO-hydroxycamptothecin [106] and coumarin 4 [107]. It can be expected that proton diffusion also plays a role in hydroxyquinoline compounds [108-112]. Finally, proton diffusion has been suggested in the long time dynamics of green fluorescent protein [113], where the chromophore functions as a photoacid [23,114], with an initial proton release on a 3-20 ps time scale [115,116]. 

Sarkar, N., Das, K., Datta, A., Das, S., and Bhattacharyya, K. 1996. Solvation dynamics of Coumarin 480 in reverse micelles. Slow relaxation of water molecules. 

Hazra, P. and Sarkar, N. 2002. Solvation dynamics of Coumarin 490 in methanol and acetonitrile reverse micelles. Phys. Chem. Chem. Phys. 4, 1040-1045. 

Hazra, R, Chakrabarty, D., and Sarkar, N. 2002. Intramolecular charge transfer and solvation dynamics of Coumarin 152 in Aerosol-OT, water-solubilizing reverse micelles, and polar organic solvent solubilizing reverse micelles. Langmuir 18, 7872-7879. 

Spectroelectrochemical methods have been used in recent years to study fast-photoinduced electron transfer at the liquid/liquid interface.- "- - Of particular importance is extending the idea of employing solvent (typically N,N-dimethylaniline or DMA) as an electron donor to the liquid/liquid interface.The advantage of this approach is that complications due to ion transfer across the interface and to diffusion are obviated. Several studies of ET between coumarin dyes and electron-donating solvents in micelles, reverse micelles, at the surface of proteins, and in nanocavities have demonstrated ultrafast electron transfer that is faster than solvation due to the close proximity of the redox pair. These experiments provided additional evidence for the existence of the Marcus-inverted region at liquid interfacial sy stems. ... 

P. Setua, C. Ghatak, V. G. Rao, S. K. Das, andN. Sarkar,/. Phys. Chem. B, 116, 3704 (2012). Dynamics of Solvation and Rotational Relaxation of Coumarin 480 in Pure Aqueous-AOT Reverse Micelle and Reverse Micelle Containing Different-Sized Silver Nanoparticles inside Its Core A Comparative Study. 

A. Chakraborty, D. Seth, D. Chakrabarty, P. Hazra, and N. Sarkar, C/tcm. Phys. Lett., 40S, 18 (2005). Photoinduced Electron Transfer from Dimethyl Aniline to Coumarin Dyes in Reverse Micelles. 

In its deprotonated form, cinnamic acid already presents some prerequisites of surfactants and is easily incorporated in reversed micelles, as demonstrated bySawaki and co-workers " " and others.Then-results support the view that increased local concentration and alignment can be achieved at micellar interfaces. Substantially higher conversion of cinnamate to its photodimers is observed upon irradiation of reversed micelles formed by laurylammonium or hexadecyltrimethylammonium cinnamate in carbon tetrachloride. The photoproducts are mainly the P- and 5-truxinates, consistent with the requirements imposed by the assembly for the formation of contact ion pairs. Unfortunately, these are also the main products observed by Reiser upon irradiation of ethyl cinnamate (albeit in different proportions). Interestingly, however, the observed dimer distribution varies as a function of added water that is proposed to He near the ion pair interface. Similar results were also obtained for indene-2-carboxylate and using sodium dodecyl sulfate microemulsions in water. " The photodimerization of coumarin in micelles has been investigated by Ramamurthy and co-workers. ... 

In addition to the irreversible disruption triggered by NIR light, reversible photoisomerization reactions of some chromophores, such as the photodimerization of coumarin, have also been explored in order to design photocontrollable BCP micelles. The use of reversible photoisomerization or irreversible photocleavage reactions of various chromophores helps to design reversible or irreversible light-dissociable BCP micelles. 

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