Free Volume Dependence of the Internal Rotation of a Molecular Rotor Probe in Room Temperature Ionic Liquids

Paul, Aniruddha; Samanta, Anunay

doi:10.1021/jp8060575

Cited by 72 publications

(71 citation statements)

References 86 publications

(67 reference statements)

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“…Generally, greater viscosity will result in greater free volume dependence and a greater value of x. [45,59] In [BmPr][NTf 2 ], at both excitation wavelengths, the values of x are almost the same, so it is clear that, for both excitation wavelengths, the free volume experienced by the ThT dye are almost the same and it is expected that the microviscosity faced by ThT at these two excitation wavelengths are almost same. On the other hand, in [N 1888 ][NTf 2 ], the value of x when l exi = 405 nm is higher than that at l exi = 445 nm.…”

Section: Dependence Of Photophysics Of Tht On Viscosity and Temperaturementioning

confidence: 99%

Torsional Dynamics of Thioflavin T in Room‐Temperature Ionic Liquids: An Effect of Heterogeneity of the Medium

2013

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The ultrafast excited-state dynamics of a fibril binding dye, thioflavin T (ThT), has been studied in two room-temperature ionic liquids (RTILs): 1-Butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide and methyltrioctylammonium bis(trifluoromethylsulfonyl)imide. Previously, in most studies, it was observed that the excited-state dynamics of the ThT dye were dependent on the viscosity of the medium. In our study, by using RTILs, we have demonstrated that the excited-state dynamics of ThT are not only viscosity dependent, but also dependent on the heterogeneous nature of the medium. The effect of structural heterogeneity present in neat RTILs on the excited-state dynamics of ThT was observed. For both RTILs, excitation wavelength dependency on the emission properties of ThT was observed.

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Section: Dependence Of Photophysics Of Tht On Viscosity and Temperaturementioning

confidence: 99%

Torsional Dynamics of Thioflavin T in Room‐Temperature Ionic Liquids: An Effect of Heterogeneity of the Medium

2013

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“…These values are in good agreement with the expected literature values for molecular rotors. [24,25] We note here that due to the change in the refractive index of the medium with increasing glycerol content the radiative rate k r will increase according to the Strickler-Berg formula [68,69] [Eq. (16)] by a factor www.chemphyschem.org of 1.2 (for 100 % methanol [n = 1.332 at 22 8C] to 100 % glycerol [n = 1.474 at 22 8C] mixtures).…”

Section: Time-resolved Measurementsmentioning

confidence: 99%

“…[16,17] DCVJ and other malononitriles have been widely used to date, including studies in high-pressure environments, [18][19][20] microviscosity of phospholipid vesicles and micelles as a function of temperature, [21] interaction with proteins in blood plasma, [22] and pharmaceutical systems for microviscosity measurements. [23] DCVJ has also been used as a probe of microviscosity and free volume in phospholipid bilayers [24] and ionic liquids, [25][26][27] for the self-association of tubulin, [28] and the transformation of actin from its monomeric G-state to its polymeric Fstate. [29] It has also been shown that the emission spectrum of DCVJ is dependent on the concentration of the dye, [30] and spectral fluorescence measurements of DCVJ have been used to study liposomes as a function of temperature and cholesterol content.…”

Section: Introductionmentioning

confidence: 99%

Fluorescence Anisotropy of Molecular Rotors

et al. 2011

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We present polarization-resolved fluorescence measurements of fluorescent molecular rotors 9-(2-carboxy-2-cyanovinyl)julolidine (CCVJ), 9-(2,2-dicyanovinyl)julolidine (DCVJ), and a meso-substituted boron dipyrromethene (BODIPY-C(12)). The photophysical properties of these molecules are highly dependent on the viscosity of the surrounding solvent. The relationship between their quantum yields and the viscosity of the surrounding medium is given by an equation first described and presented by Förster and Hoffmann and can be used to determine the microviscosity of the environment around a fluorophore. Herein we evaluate the applicability of molecular rotors as probes of apparent viscosity on a microscopic scale based on their viscosity dependent fluorescence depolarization. We develop a theoretical framework, combining the Förster-Hoffmann equation with the Perrin equation and compare the dynamic ranges and usable working regimes for these dyes in terms of utilising fluorescence anisotropy as a measure of viscosity. We present polarization-resolved fluorescence spectra and steady-state fluorescence anisotropy imaging data for measurements of intracellular viscosity. We find that the dynamic range for fluorescence anisotropy for CCVJ and DCVJ is significantly lower than that of BODIPY-C(12) in the viscosity range 0.6<η<600 cP. Moreover, using steady-state anisotropy measurements to probe microviscosity in the low (<3 cP) viscosity regime, the molecular rotors can offer a better dynamic range in anisotropy compared with a rigid dye as a probe of microviscosity, and a higher total working dynamic range in terms of viscosity.

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“…42 Many specific features, such as the significant difference between the bulk viscosity and microviscosity, have been observed due to this heterogeneous nature in RTILs. 43 Recently, a growing number of studies focused on the investigation of the physicochemical properties of the mixtures of RTILs and conventional solvents because the fine-turning solvent property after adding conventional solvents may broaden the scope of the applications of the RTILs. 44−57 Many studies on the effects of water, alcohols, and other polar or nonpolar organics in RTILs were carried out.…”

Section: Introductionmentioning

confidence: 99%

Spectroscopic Evidence for Unusual Microviscosity in Imidazolium Ionic Liquid and Tetraethylene Glycol Dimethyl Ether Cosolvent Mixtures

Wang

et al. 2012

J. Phys. Chem. B

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The rotational dynamics of coumarin 153 (C153) in imidazolium-based ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim] [PF 6 ]) and tetraethylene glycol dimethyl ether (TEGDME) mixtures across all mole fractions have been investigated to determine the local viscosity of the microenvironment surrounding the probe molecules. The excimer-to-monomer fluorescence emission intensity ratio (I E /I M ) of a well-known microviscosity probe, 1,3-bis(1-pyrenyl)propane (BPP), is also employed to study the microviscosity of the mixtures as a complementary measurement. The rotational dynamics of C153 show that there are incompact and compact domains within the heterogeneous structural [bmim] [PF 6 ], resulting in fast and slow components of C153 rotational dynamics. The microviscosity in different structural domains of [bmim] [PF 6 ] before and after adding cosolvent TEGDME with different mole fractions is further investigated by studying the fluorescence anisotropy decay of probe molecules. The obtained average rotation time constants show that the microviscosity of [bmim] [PF 6 ] is enhanced after mixing with a certain amount of TEGDME, although the bulk viscosity of TEGDME itself is much lower than that of the ionic liquid. This unusual behavior of microviscosity enhancement is further proven by the steady state fluorescence measurement with the microviscosity probe of BPP. The microviscosity enhancement is reasonably demonstrated by the fast time constant of C153 rotational dynamics and the departure between the experimentally observed and calculated ratio of I E /I M of BPP, which shows that this effect is most pronounced at intermediate mole fractions of the [bmim] [PF 6 ] and TEGDME mixtures. The strengthening effects caused by the molecular interactions between TEGDME and structural heterogeneous ionic liquid [bmim] [PF 6 ] are proposed to interpret the unusual microviscosity behaviors.

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Free Volume Dependence of the Internal Rotation of a Molecular Rotor Probe in Room Temperature Ionic Liquids

Cited by 72 publications

References 86 publications

Torsional Dynamics of Thioflavin T in Room‐Temperature Ionic Liquids: An Effect of Heterogeneity of the Medium

Torsional Dynamics of Thioflavin T in Room‐Temperature Ionic Liquids: An Effect of Heterogeneity of the Medium

Fluorescence Anisotropy of Molecular Rotors

Spectroscopic Evidence for Unusual Microviscosity in Imidazolium Ionic Liquid and Tetraethylene Glycol Dimethyl Ether Cosolvent Mixtures

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