Freezing of an Isomerization Reaction at Phase Transition

Korppi-Tommola, Jouko; Hakkarainen, Aulis; Hukka, Terttu I.; Subbi, Juhan

doi:10.1007/978-3-642-83644-2_147

Cited by 2 publications

(3 citation statements)

References 7 publications

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“…This observation has been interpreted in terms of frictional effects on the photoisomerization reaction of the unrestrained cyanines. 23,25 In contrast, k nr values do not correlate with solvent viscosity for either 1 or 2 (Figure 3A). Most dramatically, k nr values for 1 are almost the same in glycerol (η = 1412 cp) and methanol (η = 0.54 cp), and the differences between 1 and 2 are very small.…”

Section: Resultsmentioning

confidence: 91%

“…Indeed, the excited-state lifetime of 1 does not increase with increasing solvent viscosity as has been observed for many trimethine and penthamethine cyanines (Figure S9B and Table S1). 23 For example, while the fluorescence lifetime of trimethine indocyanine is ca. 18-fold greater in glycerol than in water, the fluorescence lifetime of 2 is shorter in glycerol (τ F = 0.83 ns) than in all measured solvents except water.…”

Section: Resultsmentioning

confidence: 99%

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Impact of Cyanine Conformational Restraint in the Near-Infrared Range

et al. 2020

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Appending conformationally restraining ring systems to the cyanine chromophore creates exceptionally bright fluorophores in the visible range. Here, we report the application of this strategy in the near-infrared range through the preparation of the first restrained heptamethine indocyanine. Time-resolved absorption spectroscopy and fluorescence correlation spectroscopy verify that, unlike the corresponding parent unrestrained variant, the restrained molecule is

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Section: Resultsmentioning

confidence: 91%

Section: Resultsmentioning

confidence: 99%

Impact of Cyanine Conformational Restraint in the Near-Infrared Range

et al. 2020

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“…The activation energy has an electronic contribution and a medium dependent component, which can be influenced by viscosity, polarity, or both. 4,7,9,11,20,21 For symmetric carbocyanines, the medium influence on photoisomerization is exclusively through the viscosity (y). 5.9,12,14,15.22,23 The first approach to a quantitative description of the isomerization rate constant (ki,,) is based on Kramers' derivation,20 which in its hydrodynamic limit adopts the form: (1) in which EO is the electronic energy barrier to isomerization, and A and B are constants related to the curvature of the energy surface at the bottom of the well and the top of the barrier, respectively.…”

Section: Introductionmentioning

confidence: 99%

Rotational Relaxation of Carbocyanines. Comparative Study with the Isomerization Dynamics

Levitus¹,

Negri²,

Aramendı́a³

1995

J. Phys. Chem.

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Steady-state fluorescence anisotropy was measured for a series of carbocyanines in normal primary aliphatic alcohols as a function of temperature. From these values, rotational correlation times (&) were obtained.They were compared with the ones calculated by modeling each molecule by a prolate rotor or an asymmetric rotor, under stick or slip boundary conditions for rotation. The two types of rotor render very similar results.The smaller carbocyanines show a stick rotation regime at low viscosity (7) and a contribution of dielectric friction to the total friction. One dicarbocyanine has a substick behavior at low 7 and reaches the stick limit at high y. The other dicarbocyanines follow the stick regime in the whole viscosity range. The dependence of on y is compared with literature values of the isomerization rate constant's (/cis,,) dependence on 7. Both processes involve large movements of molecular fragments of similar sizes, which are influenced by the solvent viscosity. However, while q5r is proportional to 7, ki,, shows a different behavior. The analysis of the data obtained for different carbocyanines in primary alcohols allows us to conclude that the different viscosity dependencies of ki,, and of r $f arise in the different time scales in which the molecule experiences the solvent friction opposite to the motion.

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Freezing of an Isomerization Reaction at Phase Transition

Cited by 2 publications

References 7 publications

Impact of Cyanine Conformational Restraint in the Near-Infrared Range

Impact of Cyanine Conformational Restraint in the Near-Infrared Range

Rotational Relaxation of Carbocyanines. Comparative Study with the Isomerization Dynamics

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