Femtosecond Time-Resolved Spectroscopy of Photoisomerization of Methyl Orange in Cyclodextrins

Takei, Masako; Yui, Hiroharu; Hirose, Yasushi; Sawada, Tsuguo

doi:10.1021/jp011104e

Cited by 40 publications

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“…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.…”

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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).…”

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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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confidence: 99%

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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“…The UTL method was developed by applying a pump‐probe technique to thermal lens spectroscopy (TLS). It monitors the molecular dynamics of a solution through a change in the refractive index of a solution and is able to detect both radiative and nonradiative processes with high sensitivity and subpicosecond time resolution 8–19. In addition, since the refractive index of a solution directly reflects not only the dynamics of solute molecules but also that of nearby solvent molecules, the UTL method enables monitoring the dynamics of solvent molecules that are difficult to detect by time‐resolved fluorescence or transient absorption spectroscopy 12.…”

Section: Introductionmentioning

confidence: 99%

Ultrafast dynamics of a solution in spatially restricted environments studied by photothermal spectroscopies

Hirose

Yui

Sawada

2004

The Chemical Record

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The ultrafast dynamics of a solution in spatially restricted environments was studied by using the ultrafast transient lens (UTL) method. The UTL method is used to monitor the molecular dynamics of a solution by means of a change in the refractive index, which is advantageous for investigating the molecular dynamics of restricted systems. We investigated the photoisomerization of azobenzene derivatives in cyclodextrin nanocavities and revealed how the confinement affects the photoisomerization dynamics and yields. We also studied the relaxation dynamics of photo-excited auramine O (AuO) in a water/aerosol-OT/n-heptane reversed micelle. Both the perturbed properties of the included water and the interactions between AuO and the interface of the reversed micelle strongly appeared to affect the relaxation dynamics. At the same time, we observed a change in the refractive index suggesting a structural change of the micelles in the picosecond region that could not be detected by transient absorption spectroscopy. In addition, we developed the total internal reflection UTL (TIR-UTL) method to monitor the ultrafast molecular dynamics at the liquid interface. The relaxation dynamics of photoexcited AuO at the silica/water interface were observed with subpicosecond time resolution, and it was revealed that the interaction with the interface strongly inhibited the relaxation process. These results demonstrated the advantages of the UTL method for investigating the molecular dynamics of a solution in spatially restricted environments.

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“…However, it is difficult to investigate the change of such properties on an ultrafast time scale by time-resolved fluorescence or transient absorption spectroscopy. On the other hand, it has been reported that temperature increase 8,9 and structural change [10][11][12] of solutions could be sensitively measured by using the ultrafast transient lens ͑UTL͒ method, [8][9][10][11][12][13][14][15][16][17][18][19][20] in which the molecular dynamics of a solution is detected by the refractive index change of the solution. In this study, we investigated the dynamics of water pools ͑AOT/water/n-heptane system͒ induced by a relaxation process of photoexcited auramine O ͑AuO͒ molecules included in the micelles.…”

Section: Introductionmentioning

confidence: 99%

Ultrafast dynamics of aqueous solutions in size-controlled reverse micelles

Hirose

Yui

Fujinami

et al. 2003

Review of Scientific Instruments

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The ultrafast refractive index change in the aerosol OT/water/n-heptane reverse micelle system induced by a relaxation process of photoexcited auramine O (AuO) molecules in the micelles was measured by the ultrafast transient lens (UTL) method. A decrease of the refractive index of the solutions was observed following the photoexcitation of AuO molecules, and it was composed of two decay components. The time constants of these two decay components agreed well with the lifetimes of the intermediate states of the relaxation process of AuO, that is, the locally excited state and the twisted intramolecular charge transfer (TICT) state. The UTL signal of the relaxation process of AuO in bulk water was also measured, from which it was found that the decay component corresponding to the decay of the TICT state was not due to the refractive index change of the AuO molecules themselves. This component seemed to originate from the structural change of the reverse micelles induced by the TICT state.

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Femtosecond Time-Resolved Spectroscopy of Photoisomerization of Methyl Orange in Cyclodextrins

Cited by 40 publications

References 29 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

Ultrafast dynamics of a solution in spatially restricted environments studied by photothermal spectroscopies

Ultrafast dynamics of aqueous solutions in size-controlled reverse micelles

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