Femtosecond to nanosecond solvation dynamics in pure water and inside the γ-cyclodextrin cavity

Vajda, Štefan; Jimenez, Ralph; Rosenthal, Sandra J.; Fidler, Vlastimil; Fleming, Graham R.; Castner, Edward W.

doi:10.1039/ft9959100867

Cited by 264 publications

(340 citation statements)

References 31 publications

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“…4 ͑The solvent relaxation dynamics for Coumarin 480 in bulk aqueous solution takes place in 310 fs. 20 ͒ In the case of reverse micelles they investigated two water pool sizes and found S(t) exhibits a single 8 ns decay for the smaller water pool and a biexponential decay of 1.7 and 12 ns for the larger pool. 6 ͑Their time resolution is ϳ80 ps.͒ Sarkar and co-workers have investigated the solvation dynamics of Coumarin 490 in aqueous reverse micelles and Coumarin 152A in acetonitrile and methanol reverse micelles.…”

Section: Experimental Workmentioning

confidence: 99%

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Simulations of time-dependent fluorescence in nano-confined solvents

Thompson

2004

The Journal of Chemical Physics

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The time-dependent fluorescence of a model diatomic molecule with a charge-transfer electronic transition in confined solvents has been simulated. The effect of confining the solvent is examined by comparing results for solutions contained within hydrophobic spherical cavities of varying size ͑radii of 10-20 Å͒. In previous work ͓J. Chem. Phys. 118, 6618 ͑2002͔͒ it was found that the solute position in the cavity critically affects the absorption and fluorescence spectra and their dependence on cavity size. Here we examine the effect of cavity size on the time-dependent fluorescence, a common experimental probe of solvent dynamics. The present results confirm a prediction that motion of the solute in the cavity after excitation can be important in the time-dependent fluorescence. The effects of solvent density are also considered. The results are discussed in the context of interpreting time-dependent fluorescence measurements of confined solvent systems.

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Section: Experimental Workmentioning

confidence: 99%

“…20 In this case only a single solvation shell of water is contained with the solute inside the cavity and the size-dependence is not considered.…”

Section: Theoretical Workmentioning

confidence: 99%

Simulations of time-dependent fluorescence in nano-confined solvents

Thompson

2004

The Journal of Chemical Physics

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“…[9][10][11][12][13] The key feature of liquid water is its formation of dynamic hydrogen-bond networks that are responsible for water's unique properties. 14 Bulk water dynamics occur over a range of time scales, from tens of femtoseconds to several picoseconds.…”

Section: Introductionmentioning

confidence: 99%

Dynamics of Nanoscopic Water: Vibrational Echo and Infrared Pump−Probe Studies of Reverse Micelles

2005

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The dynamics of water in nanoscopic pools 1.7-4.0 nm in diameter in AOT reverse micelles were studied with ultrafast infrared spectrally resolved stimulated vibrational echo and pump-probe spectroscopies. The experiments were conducted on the OD hydroxyl stretch of low-concentration HOD in the H 2 O, providing a direct examination of the hydrogen-bond network dynamics. Pump-probe experiments show that the vibrational lifetime of the OD stretch mode increases as the size of the reverse micelle decreases. These experiments are also sensitive to hydrogen-bond dissociation and reformation dynamics, which are observed to change with reverse micelle size. Spectrally resolved vibrational echo data were obtained at several frequencies. The vibrational echo data are compared to data taken on bulk water and on a 6 M NaCl solution, which is used to examine the role of ionic strength on the water dynamics in reverse micelles. Two types of vibrational echo measurements are presented: the vibrational echo decays and the vibrational echo peak shifts. As the water nanopool size decreases, the vibrational echo decays become slower. Even the largest nanopool (4 nm, ∼1000 water molecules) has dynamics that are substantially slower than bulk water. It is demonstrated that the slow dynamics in the reverse micelle water nanopools are a result of confinement rather than ionic strength. The data are fit using time-dependent diagrammatic perturbation theory to obtain the frequency-frequency correlation function (FFCF) for each reverse micelle. The results are compared to the FFCF of water and show that the largest differences are in the slowest time scale dynamics. In bulk water, the slowest time scale dynamics are caused by hydrogen-bond network equilibration, i.e., the making and breaking of hydrogen bonds. For the smallest nanopools, the longest time scale component of the water dynamics is ∼10 times longer than the dynamics in bulk water. The vibrational echo data for the smallest reverse micelle displays a dependence on the detection wavelength, which may indicate that multiple ensembles of water molecules are being observed.

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“…2,[9][10][11][12][13][14][15][16] Following this seminal work, researchers have begun to apply coumarin fluorescence dynamics to probe local environment fluctuations in a wide variety of chemical environments. [17][18][19][20][21][22][23][24][25][26][27][28][29] Although the energetics and dynamics of solvation for many coumarins have been well-characterized experimentally, there are still many open questions concerning the nature of the S 1 state, as well as its evolution from the Franck-Condon region following photoexcitation from the ground state. (See Table 1 for a collection of previous experimental and theoretical results on C151 and C120.…”

Section: Introductionmentioning

confidence: 99%

Theoretical Investigation of the Ground and Excited States of Coumarin 151 and Coumarin 120

2002

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We present calculations of various properties of the ground and excited states of Coumarins 151 and 120. These and related coumarins are important in investigating ultrafast solvation processes in liquids and complex solutions as well as being important acceptors in model electron-transfer systems. We calculate the following: (1) the electronic excitation energies to several low-lying singlet states, (2) ground and excitedstate dipole moments, (3) solvation effects on excitation energies, and (4) the properties of single Coumarin 151-water complexes. We test our Time-Dependent Density Functional Theory (TDDFT) calculations against CASSCF, CASPT2 (both single and multistate versions), CIS, and ZINDO. Using TDDFT, we find excellent agreement with experimental S 1 r S 0 excitation energies. On the basis of these results, we address several outstanding questions for these systems and find: (1) that TICT-formation is unlikely upon photexcitation for gas-phase C151, (2) a greater tendency toward a planar amine group for the S 1 state than for the ground state, (3) significant differences between our gas-phase ground-state dipole moment and the experimental value, and (4) TDDFT results for water-Coumarin 151 complexes are in good agreement with the experimental results of Topp and co-workers.

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Femtosecond to nanosecond solvation dynamics in pure water and inside the γ-cyclodextrin cavity

Cited by 264 publications

References 31 publications

Simulations of time-dependent fluorescence in nano-confined solvents

Simulations of time-dependent fluorescence in nano-confined solvents

Dynamics of Nanoscopic Water: Vibrational Echo and Infrared Pump−Probe Studies of Reverse Micelles

Theoretical Investigation of the Ground and Excited States of Coumarin 151 and Coumarin 120

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