An algebraic solution for determining overall rotational correlation times from cross-correlated relaxation rates

SummaryAn accurate rotational correlation time is critical for quantitative analysis of fast timescale NMR dynamics. As molecular weights increase, the classic derivation using transverse and longitudinal relaxation rates becomes increasingly unsuitable due to the non-trivial contribution of dipole-dipole and chemical exchange processes. Derivation using cross-correlated relaxation experiments, such as TRACT, overcome these limitations but are erroneously calculated in at approximately 50% of the citing literature. The goals of this study are to 1) investigate the potential sources of the error, 2) provide an algebraic solution, and 3) highlight that future inaccuracies can be minimized by requiring publication of sufficient raw data and computational routes for re-evaluation.

Фотофизические процессы в молекулах галогенпроизводных флуоресцеина в анионных обратных мицеллах

Studies of photophysical processes in aqueous micellar solutions of halogen derivatives of fluorescein: Eosin( E), Erythrosin (ER) and Bengal Rose (BR) by methods of dynamic light scattering, stationary and time-resolved fluorescence spectroscopy were carried out. It was found that the introduction of dye molecules into reverse AOT micelles causes an increase in their hydrodynamic radii Rh. The time-resolved fluorescence of the studied dye molecules in reverse micelles was measured. A decrease in the average time of the excited state with an increase in Rh for E, ER, and BR was found, which is associated with an increase in the mobility of water molecules and a decrease in the effect of geometric restriction of dye molecules. The degrees of anisotropy of the fluorescence r of dye molecules in reverse micelles were measured. It was shown that in micellar systems r is greater than in aqueous solutions and decreases with increasing Rh. The rotational correlation time for the studied dye molecules in micellar systems is determined, which decreases for all the studied dyes with an increase in Rh, indicating a decrease in the microviscosity of the confined aqueous medium inside the micelle. In this case , i.e., the value of the time of the rotational correlation is affected by the "heavy atom effect".

The influence of like-charge attraction on the structure and dynamics of ionic liquids: NMR chemical shifts, quadrupole coupling constants, rotational correlation times and failure of Stokes–Einstein–Debye

The formation of clusters of like-charge influences the structure and dynamics of ionic liquids.