Spectroscopic Probing of Solvation Interactions

Abstract

Three spectroscopic methods have been developed to probe structures of solvation environments in organic solutions: electronic band broadening measurements, two-photon perturbation studies, and fluorescence depolarization experiments. The results of each spectroscopic study indicate that the method does sense solvation structural effects rather than a completely amorphous liquid. The application of these probes is especially promising for investigations of liquid chromatographic retention mechanisms, and a preliminary study of the separation of aromatic isomers is discussed.

Time-resolved fluorescence intensity and anisotropy decays of 2,5-diphenyloxazole by two-photon excitation and frequency-domain fluorometry

“…It is well known that two-photon absorption has different selection rules than one-photon absorption. 18,[20][21][22] However, we are unaware of a description of the anisotropy 23 values expected for two-photon excitation with linearly polarized light. We now show for randomly oriented molecules with a single transition, that photoselection by two-photon absorption can excite a population of molecules with a higher orientation than for one-photon absorption.…”

“…where α i are the preexponential factors and τ i are the decay times. For a single-exponential decay the phase and modulation are related to the decay time (τ) by tan ϕ ω = ωτ (13)…”

“…6,11,12 The polarization and symmetry parameters of solutes excited by two photons were described by Wirth and co-workers. 13,14 Two-photon spectroscopy has also been applied for steady-state measurements of biomolecules. 15 In particular, Callis and co-workers used two-photon excitation to study the 1 L a and one 1 L b excited states of indole derivatives.…”

Light quenching and fluorescence depolarization of rhodamine B and applications of this phenomenon to biophysics

“…We compared the extent of depolarization caused by light quenching with that predicted by our theory (eqs [11][12][13][14]. Forth is comparison we used the anisotropies of RhB in glycerol at 5 °C.…”

“…While there were earlier reports of TPE, these studies were designed to reveal the symmetry of the electronic states. [8][9][10][11] In contrast, the more recent reports used TPE to provide localized excitation in fluorescence microscopy, 1213 improved resolution of anisotropy decays, 14,15 or resolution of overlapping electronic spectra. [16][17][18] The surprising observation that TPE can be observed with widely available picosecond laser sources [14][15][16] is likely to result in the more widespread use of this nonlinear process.…”