Rotational diffusion of stilbene in alkane and alcohol solutions

Courtney, S. H.; Kim, Seong K.; Canonica, Silvio; Fleming, Graham R.

doi:10.1039/f29868202065

Cited by 81 publications

(66 citation statements)

References 3 publications

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“…Furthermore, the high pressure limit k ∞ as calculated from k(E) obtained from measurements in supersonic beam expansions of 2 [32][33][34] agrees to within a factor of less than two with rate coefficients k of photoisomerization in low viscosity fluids [35]. These findings seem to indicate that the weak viscosity dependence of k in n-alkane and n-alkanol solvents series (1a) represent a more general phenomenon suggesting that microviscosity effects involving the relative size of solute and solvent molecules [36,37] may be responsible for the deviation of k(η) from η −1 -behavior under these conditions [38][39][40][41]. The absence of phenomena (1b) and (2) in the photoisomerization of 2, however, is an indication that they might be closely connected and that particulars of the potential energy surface of trans-1 could be responsible for its abnormal behavior.…”

Section: Introductionsupporting

confidence: 58%

Fluorescence Excitation Spectrum, Lifetimes and Photoisomerization of Jet-Cooled Conformers of 1,1´-bi(benzocyclobutylidene)

Ernst¹,

Rupp²,

Frank³

et al. 2002

Zeitschrift Für Physikalische Chemie

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Fluorescence Excitation Spectra / 1,1 -bi(benzocyclobutylidene) / PhotoisomerizationFirst measurements of fluorescence excitation spectra of the recently synthesized rigid stilbene analogue 1,1 -bi(benzocyclobutylidene) in a supersonic jet expansion show that, in contrast to the parent compound, both the trans-and the cis-conformer fluoresce under these conditions. The excitation energy dependence of fluorescence lifetimes indicates the onset of an efficient non-radiative decay channel above energy thresholds of 1340 cm −1 and 990 cm −1 for the trans-and cis-form, respectively, which is assigned to photoisomerization in the singlet state. From an RRKM analysis of the microcanonical rate coefficients an estimate of the high pressure limit of the thermal photoisomerization rate coefficient is obtained and compared with photoisomerization rate coefficients measured in low viscosity solution and in thermal vapor. There are strong indications that for this compound there are no dynamic or static solvent induced effects that lead to an anomalous acceleration of the reaction in solution.

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Section: Introductionsupporting

confidence: 58%

Fluorescence Excitation Spectrum, Lifetimes and Photoisomerization of Jet-Cooled Conformers of 1,1´-bi(benzocyclobutylidene)

Ernst¹,

Rupp²,

Frank³

et al. 2002

Zeitschrift Für Physikalische Chemie

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“…Numerous studies carried out with dipolar and non-polar solutes in non-polar solvents indicate that the rotation of a medium-sized solute molecule is close to slip behaviour. 50,[58][59][60][61][62][63][64][65][66][67][68][69] Thus, the rotation of both DMDPP and DPP is in accordance with the predictions based on the literature data. However, structurally these two solutes are similar and their van der Waals volumes are almost the same.…”

Section: Do Organic Solutes Experience Specific Interactions With Ionsupporting

confidence: 90%

“…Quasihydrodynamic theories of Gierer-Wirtz (GW) 71 and Dote-Kivelson-Schwartz (DKS) 72 have often been used to rationalize these kinds of experimental results. [59][60][61][62][63][64][65] According to the GW and DKS theories, the extent of solute-solvent coupling depends on the relative sizes of the solute and solvent, which is not taken into consideration by the SED hydrodynamic theory. The GW theory visualizes the solute to be surrounded by concentric shells of solvent and the boundary condition parameter, C is obtained by considering how the angular velocity of the solvent molecules in the successive shells surrounding the solute decreases as a function of the distance away from it.…”

Section: Interplay Of Size Effects and Specific Interactionsmentioning

confidence: 99%

The role of specific interactions on dynamical processes in a room temperature ionic liquid

Mali

2009

J Chem Sci

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This article describes our ongoing efforts to comprehend the role of specific interactions on the dynamical processes such as rotational diffusion and photoisomerization in a typical room temperature ionic liquid. Rotational diffusion studies carried out with a pair of structurally similar non-dipolar solutes indicate that organic solutes do experience strong specific interactions even with the highly associative ionic liquids such that their rotation is hindered. Similar measurements carried out with a nonpolar and a dipolar solute in an ionic liquid and a conventional solvent reveal that even in ionic liquids, apart from the viscosity of the medium, the important parameters, which govern the solute rotation are the solvent-size and free volume in case of non-polar solutes, whereas for charged and dipolar solutes, it is the solute-solvent interaction strength. Photoisomerization studies dealing with a pair of carbocyanine derivatives have shed light on the influence of solvent viscosity and specific interactions on the rates of photoisomerization. Our results point to the fact that the positively charged as well as the negatively charged cyanine derivatives do not experience specific interactions with the ionic liquid such that the isomerization rates are affected. However, when the isomerization rates are compared with a conventional isoviscous solvent, it has been noticed that the rates of isomerization are solely governed by viscosity of the medium in case of the positively charged cyanine derivative. In contrast, photoisomerization rates of the negatively charged cyanine derivative are significantly faster in a conventional isoviscous solvent compared to the ionic liquid due to the specific interactions between the solute and the former, which lower the barrier height for isomerization.

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“…12,16,32,[41][42][43][44] Although nonpolar, nondipolar, and polar solutes have been used in these investigations, studies involving ionic solutes resulted in very interesting observations. Hartman et al 41 have measured the reorientation times of an anionic probe, resorufin in water and dimethyl sulfoxide (DMSO) at several concentrations of LiNO 3 in the range 0.0-2.0 M. Although they observed no change in the viscosity normalized reorientation times (τ r /η) of resorufin in water with an increase in the electrolyte concentration, they found a 100% increase in the τ r /η value of resorufin in DMSO from 0.0 to 2.0 M LiNO 3 . Upon the addition of LiNO 3 , resorufin anion forms ion pairs with Li + and the significant increase in τ r /η has been rationalized as an enhancement in the mechanical friction due to the association of the solvent molecules with these ion pairs.…”

Section: Introductionmentioning

confidence: 92%

Rotational Diffusion of Coumarins in Electrolyte Solutions: The Role of Ion Pairs

Dutt

Ghanty

2003

J. Phys. Chem. B

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In an attempt to explore how electrolyte ions influence the friction experienced by solutes with different functional groups, rotational diffusion of two structurally similar coumarins, coumarin 343 (C343) and coumarin 334 (C334), has been studied in dimethyl sulfoxide (DMSO) at several concentrations of LiNO 3 . The two coumarins are almost identical except for the different functional groups in the 3-position; C343 has -COOH whereas C334 has -COCH 3 . Because of the presence of the -COOH functional group, C343 exists as both anionic and neutral species in DMSO. Although both anionic and neutral forms of C343 exist in the ground state, C343 predominantly exists as neutral species in the excited state. The measured reorientation time of C343 in DMSO is slower by a factor of 2 compared to that of C334 due to the hydrogen bonding between the -COOH group of the probe and sulfoxide group of the solvent. However, the viscosity normalized reorientation times (τ r /η) of C343 in LiNO 3 /DMSO solutions increase by 60% to 70% compared to that in pure DMSO. Addition of electrolyte ions shifts the equilibrium toward the anionic form of C343, which in turn forms ion pairs with Li + , and the large increase in τ r /η values is due to the association of DMSO solvent molecules with these ion pairs. On the other hand, τ r /η values of the neutral solute, C334, remain invariant in the entire range of the electrolyte concentration. The C343 -Li + ion pairs have been characterized using ab initio molecular orbital methods. Two approaches have been employed to model the friction experienced by the C343 -Li + ion pairs. In the first approach, the complex formed between C343 -Li + and the solvent molecules is treated as a rigid entity and the increase in the viscosity normalized reorientation time has been accounted for solely as an enhancement in the mechanical friction. Alternatively, the solvent association with the C343 -Li + ion pairs has been modeled as dielectric friction using the extended charge distribution theory.

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Rotational diffusion of stilbene in alkane and alcohol solutions

Cited by 81 publications

References 3 publications

Fluorescence Excitation Spectrum, Lifetimes and Photoisomerization of Jet-Cooled Conformers of 1,1´-bi(benzocyclobutylidene)

Fluorescence Excitation Spectrum, Lifetimes and Photoisomerization of Jet-Cooled Conformers of 1,1´-bi(benzocyclobutylidene)

The role of specific interactions on dynamical processes in a room temperature ionic liquid

Rotational Diffusion of Coumarins in Electrolyte Solutions: The Role of Ion Pairs

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