Ultrafast dynamics of solvation: the story so far

Abstract

A presença de moléculas de solvente na vizinhança de um soluto afeta uma variedade de processos em química e biologia, e por isso é interessante obter uma descrição física de como funciona a solvatação. Embora existam muitas ferramentas espectroscópicas estruturalmente sensíveis para a investigação do papel de moléculas de solvente em processos químicos, a medida em tempo real da dinâmica de solvatação somente tornou-se possível após o desenvolvimento de espectroscopias a laser pulsado com resolução temporal de femtossegundos. Esta revisão descreve aplicações da espectroscopia ultra-rápida ao estudo da dinâmica de solvatação. A nível de terceira ordem, discutimos a dinâmica de solvatação com técnicas ressonantes e não-ressonantes, com um foco no estudo de líquidos simples e complexos. Espectroscopias Raman de quinta ordem também são apresentadas, sendo que o enfoque dá-se no novo entendimento que estas técnicas fornecem com relação ao papel do solvente em reações químicas e à natureza anarmônica do estado líquido.The presence of solvent molecules in the vicinity of a solute affects a variety of processes in chemistry and biology, and thus one would like to have a physical picture of how solvation works. Although there are many structurally sensitive spectroscopic tools to investigate the role of solvent molecules in chemical processes, real time measurements of the dynamics of solvation had to wait for the development of pulsed laser spectroscopies with femtosecond time-resolution. This review describes applications of ultrafast spectroscopy to the study of solvation dynamics. At third order, we review resonant and non-resonant probes of solvation dynamics, with a focus on the study of simple and complex liquids. Fifth-order Raman spectroscopies are also reviewed, focusing on the insights these techniques give into the role of the solvent in chemical reactions and the anharmonic nature of the liquid state.

Solvation dynamics: improved reproduction of the time-dependent Stokes shift with polarizable empirical force field chromophore models

“…The investigation of solvent properties via calculation or measurement of the time-dependent Stokes shift (TDSS) has been of high interest during the last decades. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] The TDSS probes the timescale of solvent rearrangement by excitation of a dissolved chromophore, which causes the solvent to reorganize and the wavelength of the emitted fluorescence light of the chromophore to change. Upon excitation, both the dipole moment and the polarizability of the chromophore change, so that both the electrostatic and dispersion interactions change.…”

Altered relaxation dynamics of excited state reactions by confinement in reverse micelles probed by ultrafast fluorescence up-conversion

“…In most liquids C(t) reveals quite complex dynamics including an ultrafast (ca 100 fs) impulsive response, which can be connected to librational dynamics in the liquid, as well as slower diffusive solvent reorganisation. 39,40 A detailed discussion is beyond the present scope, but it is sufficient to note that solvation dynamics plays an important, and sometimes controlling, role in the dynamics of many reactive systems in the condensed phase. This becomes more apparent in the next section, where the solvation time correlation function is an important input to the theoretical modelling of reaction dynamics.…”

Ultrafast Dynamics of a Fluorescent Tetrazolium Compound in Solution

“…These may comprise intramolecular vibrational redistribution( IVR),s tructurala nd vibrational relaxation, and solvation, that is, solvent molecules reorient after excitation of as olute molecule to minimize its overall free energy. [73,76] Therefore, disentanglingt hese different contributions, which all add to the Stokes shift, is often not possible. [74,75] Solvation also gives rise to dynamics that are not describedm onoexponentially,b ut can be composed of ar apid decay followed by a slowero ne, which can last up to nanosecondsi ft he solvent viscosity is high.…”

“…[74,75] Solvation also gives rise to dynamics that are not describedm onoexponentially,b ut can be composed of ar apid decay followed by a slowero ne, which can last up to nanosecondsi ft he solvent viscosity is high. [73,76] Therefore, disentanglingt hese different contributions, which all add to the Stokes shift, is often not possible.…”