Polar solvation dynamics in water and methanol: search for molecularity

Sajadi, Mohsen; Weinberger, Michael; Wagenknecht, Hans‐Achim; Érnsting, N. P.

doi:10.1039/c1cp21794a

Cited by 76 publications

(101 citation statements)

References 41 publications

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“…The band exhibitsafast blue shift during the first 5psd escribed by two time constants (t 1 and t 2 in Ta ble 2, and EADS Aa nd Bi nF igure 4C). These time constants are consistent with those measured for other CT-type fluorophores in water and can be principally attributedt os olvent relaxation, [61][62][63] although some contribution from structural relaxation cannot be fully excluded (e.g.,p lanarization of the side chain). Stimulated emission can be observeda ta round 550-700 nm as theE SA band shifts to shorter wavelengths, in agreement with the steady-state emission.…”

Section: Broadband Transient Absorptionsupporting

confidence: 86%

Untying the Photophysics of Quinolinium‐Based Molecular Knots and Links

Caprice

Aster

Kumpulainen

2020

Chemistry A European J

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Complex molecular knots and links are still difficult to synthesize and the properties arising from their topology are mostly unknown. Here, we report on ac omparativep hotophysical study carried out on af amily of closely related quinolinium-based knots and links to determine the impact exertedby topology on the molecularb ackbone. Our results indicatet hat topology has an egligible influence on the behavior of loosely braided molecules, which mostly behave like their unbraided equivalents. On the other hand, tightly braided molecules display distinct features. Their higher packing density results in ap ronounceda bility to resist deformation,asignificant reduction in the solvent-accessible surface area and favors close-range p-p interactions betweent he quinolinium units and neighboring aromatics. Finally,t he sharp alteration in behavior between looselya nd tightly braided molecules sheds light on the factorsc ontributingt ob raiding tightness.

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Section: Broadband Transient Absorptionsupporting

confidence: 86%

Untying the Photophysics of Quinolinium‐Based Molecular Knots and Links

Caprice

Aster

Kumpulainen

2020

Chemistry A European J

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“…The EADS represents the spectral evolution with successively increasing lifetime. The time-resolved anisotropic decay r(t) was calculated from the decay curves under the parallel polarizations I || (t) and perpendicular polarizations I ⊥ (t) based on the tail matching correction according to equation (3): [23][24][25] …”

Section: Discussionmentioning

confidence: 99%

Energy transfer and spectroscopic characterization of a perylenetetracarboxylic diimide (PDI) hexamer

Long

Wang

Vdović

et al. 2015

Phys. Chem. Chem. Phys.

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We report a comprehensive study on a newly synthesized perylenetetracarboxylic diimide (PDI) hexamer together with its corresponding monomer and dimer by means of steady-state absorption and fluorescence as well as femtosecond broadband transient absorption measurements. The structure of the PDI hexamer is nearly arranged in a 3-fold symmetry by three identical and separated dimers. This unique structure makes the excited state energy relaxation processes more complex due to the existence of two different intramolecular interactions: a strong interaction between face-to-face PDIs in dimers and a relatively weak interaction between the three separated PDI dimers. The steady-state spectra and the ground state structural optimization show that the steric effect plays a dominant role in keeping the formation of the face-to-face stacked PDI-dimer within the PDI-hexamer, indicating that some level of a pre-associated excimer had formed already in the ground state for the dimer in the hexamer. Femtosecond transient absorption experiments on the PDI hexamer reveal a fast (∼200 fs) localization process and a sequential relaxation to a pre-associated excimer trap state from the delocalized exciton state with about 1.2 ps after the initially delocalized excitation. Meanwhile, excitation energy transfer among the three separated dimers within the PDI-hexamer is also revealed by the anisotropic femtosecond pump-probe transient experiments, where the hopping time is about 2.8 ps. A relaxed excimer state is further formed in 7.9 ps after energy hopping and conformational relaxation.

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“…We compute DE Solv (t) of solvent clusters extracted from our trajectories, partitioning the solvating water molecules into three groups (Figure 3): group a: water molecules that are located in a torus 10 in diameter centered at the NÀO axis of MQ (for details see the Supporting Information); Dynamics of the Stokes shift as obtained by averaging ten trajectories and smoothing by 10 point moving-window averaging (black, left axis), Stokes shift after removal of five random trajectories (gray lines, left axis), experimental data [14] (dashed black line, right axis); data is referenced to n(t=1) in both cases (dotted base line).…”

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confidence: 99%

An Ab Initio Microscope: Molecular Contributions to the Femtosecond Time‐Dependent Fluorescence Shift of a Reichardt‐Type Dye

et al. 2013

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Despite decades of effort, the properties of liquid water are not fully understood. In recent years it was found that geometric confinement has a strong effect on water, making it quite different from the bulk. [1] To understand protein functionality, agglomeration, and folding, as well as DNA stability, it appears to be essential to explicitly consider the presence of water. [2] With current IR-based spectroscopic techniques, it is possible to monitor rapid photochemical reactions. [3] These techniques are, however, severely limited by strong absorption due to water, in addition to spectral crowding. To overcome these limitations, compounds with isotopically substituted carbonyl groups have been used. [4] IR spectroscopy observes the hydrogen-bond network indirectly by its coupling to the vibrational modes. Fluctuations of the hydrogen-bond network can be directly measured by THz spectroscopy which probes the dielectric bulk response. [5] Inside biomolecules or confinements, the absorption background of water can be entirely avoided when the fluorescence of a suitably placed chromophore is monitored. For this purpose, dyes are employed whose fluorescence depends strongly on solvent polarity. [6] In this context, the molecular probe Nmethyl-6-oxyquinolinium betaine (MQ) is especially attractive because of its small size and water solubility, allowing insertion into DNA or proteins. Structurally, it resembles the polarity indicator dye introduced by Reichardt and coworkers. [7] The local THz spectrum, up to the far-IR intramolecular modes, can then be extracted almost quantitatively from the time-dependent Stokes shift (TDSS) of its fluorescence as measured by femtosecond spectroscopy. The connection between TDSS data of MQ and the THz spectrum of its surroundings has been established by simple dipolar continuum theory. [8] It should be noted that the Stokes shift of the chromophore represents only an indirect measurement of the water dynamics. In addition, the presence of the chromophore has the potential of affecting this very water dynamics to a certain extent.However, the time-dependent dielectric response can be traced back to the structure and dynamics around the molecular probe in atomistic detail with the help of molecular dynamics simulations in combination with the experimentally observed evolution of the Stokes shift.Published attempts at describing time-dependent solvation with molecular dynamics used either a quantum mechanics/molecular dynamics (QM/MM) approach, including only the solute and a few water molecules in a quantum mechanical treatment, [9] or a model potential derived from quantum mechanical calculations of the chromophore. [10] In our approach, we use density functional theory (DFT) for solute and solvent, which is known to yield an accurate picture of solvent effects and the dynamics of hydrogen-bond networks, also for excited-state solutes. [11] Instead of the dielectric linear response of the solvent or the time-dependent solvation energy, we compute the time-dependent fluoresce...

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Polar solvation dynamics in water and methanol: search for molecularity

Cited by 76 publications

References 41 publications

Untying the Photophysics of Quinolinium‐Based Molecular Knots and Links

Untying the Photophysics of Quinolinium‐Based Molecular Knots and Links

Energy transfer and spectroscopic characterization of a perylenetetracarboxylic diimide (PDI) hexamer

An Ab Initio Microscope: Molecular Contributions to the Femtosecond Time‐Dependent Fluorescence Shift of a Reichardt‐Type Dye

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