Unusual resonance lines have been observed for a dimer associate of impurity 63Cu2+ ions in a BaF2 single crystal in continuous-wave electron paramagnetic resonance spectra recorded using a dielectric resonator. The phase of these lines is orthogonal to the phase of magnetic field modulation. The appearance of such lines is attributed to the features of the spin dynamics of high-spin electron systems resonantly interacting with a microwave electromagnetic field. The magnetic dipole moment of the spin system is transformed into the electric quadrupole moment under the sufficiently intense resonant excitation of magnetic dipole transitions. In this case, the interaction of the magnetic dipole and electric quadrupole oscillators occurs in the spin system. The simultaneous excitation of magnetic dipole and electric quadrupole resonant transitions in the dielectric resonator of a spectrometer leads to the appearance of phase-shifted resonance lines.

The reaction of [NiBr2(bpy)2] (bpy = 2,2 '-bipyridine) with 2,2 '-bibenzimidazole or 5,5 ',6,6 '-tetramethyl-2,2 ' bibenzimidazole (bbim) in the presence of AgBF4 and Et3N results in the formation of dinuclear nickel(II) complexes with bridging bbim ligands. The crystal structures of the obtained complexes [Ni2(mu-bbim)(bpy)4] [(BF4)2] have been determined. Variable-temperature EPR as well as magnetometry experiments indicate antiferromagnetic interactions between the nickel atoms in the complex molecule at low temperatures. Density functional theory (DFT) calculations confirm these findings. Cyclic voltammetry and in situ EPR spectroelectrochemistry demonstrated that these complexes can be electrochemically reduced resulting in the formation of Ni(I) and Ni(0) derivatives. This can be considered as a strategy for controlling the electronic state of these dinuclear nickel complexes, thus providing a way to design magnetic materials with switchable properties.

The synthesis, X-ray structure, and results of magnetic properties study of a new Fe(III) complex with tridentate NNO donors beta-enaminone of the composition [FeL2]SbF6 (L = 1-phenyl-3-(quinolin-8-ylamino)prop-2-en-1onato) are presented. In the complex molecule, Fe(III) is octahedrally coordinated by four nitrogen atoms and two oxygen atoms from two ligands in the donor environment of N4O2. The presence of a smooth spin transition in solid samples above 120 K has been demonstrated by the EPR method. The values of splitting of energy levels of the ground state obtained from the analysis of g-factor values of low-spin Fe(III) centers for vitrified solutions allowed to assume the presence of spin transition in the system above 160 K. Electron spectroscopy data confirmed this assumption by demonstrating a spin transition for the complex in solution at temperature range 288-333 & Kcy;. Molecular docking of Helicobacter pylori urease (PDB ID: 1E9Z) and B-DNA (PDB ID: 1BNA) with Fe (III) complex yielded minimum binding affinity of -9.1 kcal/mol and -8.1 kcal/mol, respectively.

The study of exchange-coupled [Fe+–Fe2+] pairs that we previously found in X-ray–irradiated BaF2:Fe crystals was continued by the EPR method. It was confirmed that the ground state of the studied pairs is the electron spin multiplet S = 7/2 split by the anisotropic part of the exchange interaction and by the crystal field so that the ground state turned out to be the Kramers doublet | ± 1/2⟩ . It was found that the energy interval to the next spin doublet is 125 GHz. It was established that the nearest ligands of iron ions in the exchange-coupled [Fe+–Fe2+] pair are eight fluorine ions detected in the EPR spectra as structurally equivalent. The parameters of the superhyperfine interaction with the magnetic moments of the nuclei of these ligand ions were determined. It was shown that the observed experimental facts clearly indicate that the exchange between iron ions in the studied pairs occurs mainly by Zener’s double exchange mechanism.

Impurity paramagnetic complexes [NiF4F4Fint]6–(C4v), stable associates of the trivalent nickel ion with the interstitial fluorine ion F_int^- , were synthesized in BaF2 ionic crystals with the fluorite structure. The molecular structure of the synthesized complexes was studied by electron paramagnetic resonance at frequencies of 9.39 and 34.25 GHz in the temperature range from 5 to 250 K. It was shown that, in the studied complex, the Ni3+ ion (3d7, 4F, S = 3/2) replaces the lattice cation Ba2+ but, under the influence of F_int^- in the neighboring interstice of the octahedral type, is shifted toward it from the center of the coordination cube occupied by it. Under the influence of the crystal field of tetragonal symmetry, the electron spin levels of the complex are split into two Kramers doublets, of which the ground state Kramers doublet turned out to be | ± 1.2⟩ . The energy interval between doublets is approximately 114 GHz. The EPR spectra exhibit a superhyperfine structure caused by the interactions of the electron spin moment of the nickel ion with the nuclei of nine ligand fluorine ions. The parameters of these interactions were determined.

In this work, the nutation of the spins of unpaired electrons in the nitroxide biradical of bis-methano[60] fullerene was experimentally studied. Nutation frequencies were found in a wide range of microwave field power. To interpret the obtained results, numerical calculations of the nutation of biradicals were carried out for a set of parameters of the spin-spin interaction of a pair of unpaired electrons and for different values of the Rabi frequency of the microwave field. At comparing numerical results with experimental data, we also used the results of analytical calculations of nutation for some model situations. As a result of the analysis of experimental data on nutation, an estimate of the exchange and dipole-dipole interactions for the studied biradical was obtained. They are consistent with the results obtained from analysis of the shape of the EPR spectrum for a given biradical.

A long-range forecast system based on the improved version of the SLAV072L96 global atmosphere model has been verified at the Hydrometcenter of Russia. The model has the horizontal resolution of 0.9° × 0.72° in longitude and latitude and 96 vertical levels and includes modern parametrizations for the subgrid-scale processes in the atmosphere and active soil layer. Main features and particularities of this model version are presented along with a brief description of ensemble long-range meteorological forecast technology using this model. Some verification scores for long-range forecasts based on the archive data from ERA5 reanalysis for 1991–2015 and on the data for 2023 are presented.

Lanthanide-based endohedral metallofullerenes (EMFs) form a special class of molecular magnets, in which magnetic anisotropy and metal-metal interactions can be varied in a broad range by judicious choice of the structure of endohedral species. Nonetheless, the influence of metal-cage interactions on the magnetic anisotropy, which should pertain to all types of EMFs, has not been studied yet in necessary detail. In this work, an interplay between magnetic anisotropy, Er & ctdot;Er coupling, and bonding interactions in erbium mono- and dimetallofullerenes is studied by EPR, photoluminescence, SQUID magnetometry, and ab initio calculations. We analyzed the ligand field created solely by metal-fullerene interactions in the mono-EMFs Er@C80,82(CH2Ph) and showed how it changes when Er-Er bonding kicks in for di-EMFs Er2@C82 and Er2@C80(CH2Ph). X-band and Q-band EPR spectroscopy is used to precisely describe the ground-state doublets of Kramers mono-Er EMFs and Er2@C80(CH2Ph). For Er2@C82, which is a non-Kramers system, X-band measurement in the parallel mode was used. The EPR signals of di-Er EMFs were observed at large g-values exceeding 20, which unambiguously assigns them to the coupled states of Er2 dimers rather than single-ion transitions. Ab initio calculations revealed that the moderate cage-induced magnetic anisotropy of mono-EMFs is enhanced by the Er-Er bond in di-EMFs. Magnetization studies augmented with effective spin Hamiltonian modelling showed that the Er & ctdot;Er coupling in Er2@C82 with a two-electron Er-Er bond is weakly antiferromagnetic, while Er2@C80(CH2Ph) with a single-electron Er-Er bond features a strong ferromagnetic interaction between Er moments and unpaired electron spin. An interplay between magnetic anisotropy, Er & ctdot;Er coupling, and bonding interactions in erbium mono- and dimetallofullerenes is studied by EPR, photoluminescence, SQUID magnetometry, and ab initio calculations.

Experimental confirmation of the manifestations of new spin exchange paradigm in EPR spectra of 14N nitroxide radical solutions is presented. It was shown that in the region of relatively low concentrations of radicals, the two side components of the spectrum have a mixed shape (the sum of the absorptive line and dispersive line). The dispersion contributions in these two lines have opposite signs. As the concentration of radicals increases, the contribution of dispersion passes through an extremum and in the region of maximum contribution of dispersion, the contribution of absorption to these two lines changes sign. In the region of high concentrations of radicals, when one homogeneously broadened line is practically observed, it turns out that these side components have resonant frequencies that do not coincide with the frequency of the center of gravity of the spectrum.

The reaction of [NiBr(aryl)(bpy)] organonickel complexes with sodium 1,2-diphospholide leads to unknown 1-aryl-1,2-diphospholes by aryl group transfer.

The electronic system of molecular-based magnets is promising for use in quantum computing devices. Magnetic resonance techniques are used for magnetization manipulation and coherence tracking. The complexes [n-Bu4N]2[Cu(opba)] and [n-Bu4N]2[Ni(opba)] have been studied by 1H NMR technique using different pulse protocols. It is shown that the interpulse delay shift and phase cycling approaches are applicable in 1H NMR, but it’s not as efficient as they are in EPR. Since many nuclei positions completely suppress the unwanted echo contribution, the subensembles including the longitudinal magnetization evolution should be considered.

Properties of two lowest electron levels of the Fe2+ impurity ion in a natural amethyst are studied by continuous wave electron paramagnetic resonance spectroscopy in the Q-band. It is established that the these levels present quasi-doublet | ± 2⟩ with zero-field splitting of 30.9 ± 0.2 GHz. Orientation of principal magnetic axes and value of g-factor of this paramagnetic center are determined.

In this work, a comparative study of the properties of polyethylene composites filled with the residue of solvent deasphalting of tar and asphaltenes isolated from it was carried out. Scanning electron microscopy analysis found that the compatibility of petroleum residue with the matrix was better than for asphaltenes. The observed effect was related to the present of petroleum resins, which have less polarity and long alkyl substituents that can improve molecular distribution asphaltenes in the nonpolar environment of polyethylene. Fourier transform infrared, thermo-gravimetric analysis, differential scanning calorimetry, and electron paramagnetic resonance methods have shown that asphaltenes play a key role in the thermal stabilization of composites. It is assumed that the radical traps in asphaltenes are free stable radicals, particles with unpaired electrons strongly delocalized on the pi-system of polyaromatic molecules. Their antiradical action was associated to interactions with radicals formed during the thermal and thermo-oxidative decomposition of polyethylene result in the recombination and inhibition of further free-radical destruction. An analysis of the properties showed that the addition of a petroleum residue to the polyethylene makes it possible to maintain good mechanical properties after thermal-oxidative aging of composites. Thus, such asphaltene concentrates can be recommended as promising fillers for polyolefins in the polymer industry.

The electrochemical properties of bis[2-(di-i-propylphosphino)-4-methylphenyl]amido complexes [(PNP)MCl] of Ni, Pd and Pt have been investigated by experimental electrochemical methods involving cyclic voltammetry (CV), in situ UV-vis- and EPR-spectroelectrochemistry, and density functional theory (DFT) calculations. A combination of spectroscopic and theoretical techniques suggests the formation of aminyl-radical complexes as a result of the electrooxidation process. The photophysical behavior of the electrochemically generated species was studied by in situ EPR measurements with photoexcitation, which revealed the formation of free aminyl radical through the cleavage of the ligand-metal bonds. Finally, the electrochemical generation and spectroelectrochemical studies of the hydride derivative [(PNP)PdH] allow the determination of the aminyl-radical hydride complex [(PNP)PdH][BF4], which has been generated with 33 % yield.

Abstract The unusual resonance lines were observed in continuous wave electron paramagnetic resonance spectra of dimer associate of Cu2+ ions in BaF2 single crystal. The phase of these lines was significantly shifted from the phase of magnetic field modulation. We associate the appearance of these lines with special features of the high-spin electron systems under resonance interaction with microwave electromagnetic field. We take in to account that under resonance excitation of the high-spin electron spin magnetic dipole orientation transforms to quadrupole alignment, and there is the reversible mutual transformation of the dipole and quadrupole degrees of freedom. Simultaneous excitation of magnetic dipole and electric quadrupole resonance transitions in a dielectric resonator of an electron paramagnetic resonance spectrometer results in appearance of the phase shifted resonance lines.

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We present the optical and magneto-optical spectroscopy and electron paramagnetic resonance (EPR) investigations of CaMoO4 single crystals doped with the erbium ions. Telecom-wavelength resonance transition inhomogeneous line width of Er3+ is relatively narrow for oxide crystals which makes this material promising for quantum technologies applications. The hyperfine structure in optical spectra of 167Er3+ isotope is well resolved. Energies and symmetries of wavefunctions of 39 energy levels of Er3+ ions in the crystal-field (CF) of S4 symmetry and g-factors of some CF Kramers doublets were measured and successfully simulated on the basis of CF calculations. The obtained set of CF parameters was used for modeling the hyperfine structure profiles observed in the optical absorption spectra.

The possibility of coding the response of the electron–nuclear system of the tetracyanoethylene radical under microwave pulse irradiation in combination with a pulsed magnetic field gradient in the nanosecond timescale by a binary code is demonstrated. To this end, the tetracyanoethylene radical, which has a well-resolved equidistant electron paramagnetic resonance spectrum due to the interaction of the electron with equivalent magnetic nuclei, is used. The aim is to demonstrate the possibility of implementing this procedure physically rather than to encode the longest possible sequence.

The Carr–Purcell–Meiboom–Gill (CPMG) pulse sequence is actively used in magnetic resonance to measure the relaxation time T2. The refocusing pulses in this sequence are 180° by default. In this study, numerical calculations of the echo amplitudes were carried out. If T1 > T2, then applying refocusing pulses with rotation angle 90° or less increases the effective relaxation time. It becomes longer than T2 and tends to T1. To demonstrate this effect, NMR and EPR experiments were performed using the CPMG pulse sequence.

The EPR spectra of Czochralski grown Y2SiO5:Cr and Y2SiO5:53Cr crystals have been studied. In addition to the previously known spectra of Cr3+, the spectrum of the Cr4+ ion was detected and studied for the first time. The fine structure parameters of tetravalent chromium in Y2SiO5 host were obtained based on the analysis of the angular and frequency-field dependences of the EPR spectra. The conclusion about tetrahedral coordination of Cr4+ ion in this host was made. The concentrations ratio of c(Cr3+)/c(Cr4+) ions in the crystal has been evaluated.