Influence of the Electric Charge of Spin Probes on Their Diffusion in Room-Temperature Ionic Liquids.

The rotational and translational diffusion of negatively charged and uncharged spin probes in five imidazolium-based room-temperature ionic liquids (RTILs), 1-ethyl-3-methylimidazolium tetrafluoroborate, emimBF4, 1-butyl-3-methylimidazolium tetrafluoroborate, bmimBF4, 1-octyl-3-methylimidazolium tetrafluoroborate, omimBF4, 1-octyl-3-methylimidazolium hexafluorophosphate, omimPF6, and 1-octyl-3-methylimidazolium chloride, omimCl, has been studied by means of electron paramagnetic resonance spectroscopy. Detailed analyses of the spin-Hamiltonian parameters and spin exchange interactions have been carried out. The temperature dependences of the line broadening induced by the electronic dipole-dipole interaction and the electron spin exchange coupling are determined. The translational mobility of spin probes is semiquantitatively characterized and successfully explained in the framework of a hypothesis based on the assumption of polar and unpolar domains within the RTILs.

Rotational Dynamics of Nitroxide Biradical in Room-Temperature Ionic Liquids Measured by Quantitative Simulation of EPR Spectra.

Temperature dependences of electron paramagnetic resonance (EPR) spectra of an imidazoline nitroxide biradical spin probe in a series of room-temperature ionic liquids in the temperature range 124-390 K have been quantitatively simulated. The unusual asymmetric EPR spectrum shape previously observed in these systems [Kokorin et al., Appl. Magn. Res. 48 (2016) 287] is shown to originate from anisotropic rotational diffusion of the probe molecule. All experimental spectra were quantitatively reproduced in simulation using a unified set of geometrical and magnetic parameters of the spin probe, which were found to be fully consistent with the biradical geometry obtained from density functional theory calculations. Temperature dependences of rotation diffusion coefficient of the probe characterize the molecular mobility of the ionic liquid, whereas the temperature dependences of the spin-exchange integral J and of the isotropic hyperfine interaction constant, aN, are shown to reflect the intramolecular conformation motions of the biradical probe.

The Structure and Properties of TiO(2)-Cu(II)-EDTA Ternary Surface Complexes.

The formation, composition, structure, and electrochemical properties of ternary surface complexes between copper(II) and ethylenediaminetetraacetate adsorbed on TiO(2) xerogels and on thin-film TiO(2) electrodes from solutions of varying pH have been studied by potentiometry, EPR spectroscopy, and electrochemical methods. The results strongly indicate that, in contrast to other organic ligands, B-type ternary surface complexes are formed in this system. The organic ligand forms an isolating layer between the surface of the TiO(2) electrode and the redox-active copper ions. Copyright 2001 Academic Press.

[Study of heart valve xenobioprostheses by ESR]. / Izuchenie ksenobioprotezov klapanov serdtsa metodom EPR.

Copper (II) ions were used as paramagnetic labels to study the role of functional groups of structural proteins (SP) of xenobioprosthetic valves in the process of transition metal ions coordination as well as for investigation of changes in complexing properties of these proteins under influence of the recipient media. The dependence of Cu(II) coordination sphere composition in complexes with SP on the pH-value has been determined. Research of influence of the valves' calcification process on the coordination properties of the SP are in progress.

[New method for measuring the distances between the nitroxide spin label and paramagnetic metal ions in macromolecules]. / Novyi sposob izmereniia rasstoianii mezhdu spinovoi metkoi i paramagnitnymi ionami metallov v makromolekulakh.

A new method of estimation of the distance RLM between the nitroxide spin label (NSL) and the paramagnetic metal ions (PMI), such as Co2+, Ni2+, Cu2+, Mn2+, VO2+, Cr3+, Fe3+ is suggested. The influence of the longitudinal relaxation time T1 of the PMI on the line shape of the NSL at 77 degrees K has been studied. It was found that the efficiency of the dipole-dipole interaction between NSL and PMI depends strongly on the T1 value of the PMI. Measurements of the RLM for 4 spin-labelled proteins (haemoglobin, nitrogenase, cytochrome P450 and Ca2+-dependent ATPase) by three various methods have proved the correctness of the new method and also its simplicity.