Ultrafast Guest Dynamics in Cyclodextrin Nanocavities

Douhal, Abderrazzak

doi:10.1021/cr020669j

Cited by 274 publications

(152 citation statements)

References 266 publications

(701 reference statements)

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“…Because of CD and HSA confinement, the time scale for the C-N and C-C coupling may change when compared with that in free OII; the space restriction makes the twisting͞rotation channel less favorable, and, therefore, the trans isomer may take longer time to enter the isomerization region, and thus the phenyl inversion occurs. This kind of delay in reactivity due to nanocavity restriction of nuclear rearrangement has been observed in a molecule showing IPT and twisting motion at S 1 (4,8,9).…”

Section: Femtochemistry In Solutionmentioning

confidence: 61%

“…Therefore, simple and complex (in concept) molecular systems have been studied using cyclodextrins (CDs), proteins, micelles, pores, and zeolites as nanohosts, demonstrating the confinement effect of the hydrophobic nanocavities on the spectroscopy and dynamics of the guests (2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13). Relevant information on the ultrafast dynamics of caged wavepackets involving breaking͞making chemical bonds, and solvation has been acquired.…”

mentioning

confidence: 99%

“…The inclusion complexes of OII and CDs have been studied by several groups showing the formation of a 1:1 entity (24)(25)(26)(27)(28)(29)(30)(31)(32)(33)(34)(35). So far, the CD inclusion complex studies have considered that OII in water solutions exists under AZO tautomer, contrary to many studies in solutions where OII coexists under AZO and HYZ forms (5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20). Recently, ultrafast transient lens technique with a response function of Ϸ300 fs has been used to study the dynamics of OII in CD (36).…”

mentioning

confidence: 99%

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Femtochemistry of orange II in solution and in chemical and biological nanocavities

Douhal

Sanz

Tormo

2005

Proc. Natl. Acad. Sci. U.S.A.

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In this work, we report on studies of the nature of the dynamics and hydrophobic binding in cyclodextrins and human serum albumin protein complexes with orange II. With femtosecond time resolution, we examined the proton-transfer and trans-cis isomerization reactions of the ligand in these nanocavities and in pure solvents. Because of confinement at the ground state, the orientational motion in the formed phototautomer is restricted, leading to a rich dynamics. Therefore, the emission lifetimes span a large window of tens to hundreds of picoseconds in the cavities. Possible H-bond interactions between the guest and cyclodextrin do not affect the caged dynamics. For the protein-ligand complexes, slow diffusional motion (Ϸ630 ps) observed in the anisotropy decay indicates that the binding structure is not completely rigid, and the embedded guest is not frozen with the hydrophobic pocket. The ultrafast isomerization and decays are explained in terms of coupling motions between N-N and C-N stretching modes of the formed tautomer. We discuss the role of confinement on the trans-cis isomerization with the cavities and its relationships to frequency and time domains of nanostructure emission.cyclodextrins ͉ protein ͉ H-bond ͉ twisting ͉ anisotropy F emtosecond (fs) studies of caged molecules in nanocavities provide direct information on the relationship between time and space domains of molecular relaxation (1). Therefore, simple and complex (in concept) molecular systems have been studied using cyclodextrins (CDs), proteins, micelles, pores, and zeolites as nanohosts, demonstrating the confinement effect of the hydrophobic nanocavities on the spectroscopy and dynamics of the guests (2-13). Relevant information on the ultrafast dynamics of caged wavepackets involving breaking͞making chemical bonds, and solvation has been acquired.Orange II (OII) (Fig. 1), also called acid orange 7, is a molecule that has O-H . . . N and NAN bonds and may show photoinduced intramolecular proton-transfer (IPT) and transcis isomerization reactions. It is widely used in the dyeing of textiles, food, and cosmetics and thus is found in the wastewaters of the related industries (14). It has been reported that it exists under azoenol (AZO) and ketohydrazone (HYZ) forms (Fig. 1) (15-20). In a water solution, for example, the H-atom within the O-H . . . N intramolecular H-bond is shifted to the nitrogen site, making HYZ structure the most stable one (Ϸ95%) (20). In DMSO, the HYZ population decreases to 70%, and in solid state it becomes the only populated structure (20). Recent x-ray studies of phenyl substituted 1-(arylazo)-2-naphthols showed that this kind of molecules displaying HYZ-AZO tautomerism can form intramolecular resonance-assisted H-bonds from pure N-H . . . O to pure N . . . H-O structures, depending on the phenyl derivative (21, 22). Furthermore, a recent photophysical study of similar molecules in solution has shown the occurrence of a photoinduced proton-transfer reaction in AZO to give HYZ structure with a very low emission qu...

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Section: Femtochemistry In Solutionmentioning

confidence: 61%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Femtochemistry of orange II in solution and in chemical and biological nanocavities

Douhal

Sanz

Tormo

2005

Proc. Natl. Acad. Sci. U.S.A.

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“…6 The host-guest chemistry is emerging as an important way to study how binding of molecules into space-restricted environments can mediate their chemical reactivity. 7 The size, shape, and chemical environment of the aggregated host help in controlling the recognition and reactivity of guest molecules, offering the potential for entirely new types of synthetic catalysts. The formation of confined and protected hydrophobic environment in the aggregated structure has played a vital role for the study of various hydrophobic ligands.…”

Section: Introductionmentioning

confidence: 99%

Aggregated CdS Quantum Dots: Host of Biomolecular Ligands

Narayanan

Pal

2006

J. Phys. Chem. B

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In this contribution, we have studied structural and photophysical properties of aggregated CdS quantum dots (QDs) capped with 2-mercaptoethanol in aqueous medium. The hydrodynamic diameter of the nanostructures in aqueous solution was found to be ∼160 nm with the dynamic light scattering (DLS) technique, which is in close agreement with atomic force microscopy (AFM) studies (diameter ∼150 nm). However, the UVvis absorption spectroscopy, powder X-ray diffraction (XRD), and transmission electron microscopy (TEM) studies confirm the average particle size (QD) in the nanoaggregate to be 4.0 ( 0.5 nm. The steady-state and time-resolved photoluminescence studies on the QDs further confirm preservation of electronic band structure of the QDs in the nanoaggregate. To study the nature of the nanoaggregate we have used small fluorescent probes, which are widely used as biomolecular ligands (2,6-p-toluidinonaphthalene sulfonate (TNS) and Oxazine 1), and found the pores of the aggregate to be hydrophobic in nature. The significantly large spectral overlap of the host quantum dots (donor) with that of the guest fluorescent probe Oxazine 1 (acceptor) allows us to carry out Förster resonance energy transfer (FRET) studies to estimate average donor-acceptor distance in the nanostructure, found to be ∼25 Å. The quantum dot aggregate and the characterization techniques reported here could have implications in the future application of the QD-nanoaggregate as host of small ligand molecules of biological interest.

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“…The ability of CDs to encapsulate organic and inorganic molecules in aqueous solution has led to intensive studies of their inclusion complexes. (Douhal, 2004) We intuitively imagined that the confinement of a guest molecule within the CD nanocavity will reduce perturbations from the surrounding environment which causes decoherence. Several studies on CD complexes with aromatic compounds using steady-state and ultrafast time-resolved spectroscopy have been reported (Hamai, 1991;Vajda et al, 1995;Chachisvilis et al, 1998;Matsushita et al, 2004;Pistolis &Malliaris, 2004;Sato et al, 2006).…”

Section: Cyclodextrin Nanocavity Caging Effect On Electronic Dephasinmentioning

confidence: 99%

Quantum Interference Signal from an Inhomogeneously Broadened System Excited by an Optically Phase-Controlled Laser-Pulse Pair

Sato¹,

Kiba²

2010

Coherence and Ultrashort Pulse Laser Emission

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Ultrafast Guest Dynamics in Cyclodextrin Nanocavities

Cited by 274 publications

References 266 publications

Femtochemistry of orange II in solution and in chemical and biological nanocavities

Femtochemistry of orange II in solution and in chemical and biological nanocavities

Aggregated CdS Quantum Dots: Host of Biomolecular Ligands

Quantum Interference Signal from an Inhomogeneously Broadened System Excited by an Optically Phase-Controlled Laser-Pulse Pair

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