"Nutation" of electron spins in biradicals.

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.

Experimental confirmation of the formation of collective modes of the magnetization motion of paramagnetic particles in dilute solutions due to spin exchange.

Experimental confirmation of the manifestations of new spin exchange paradigm in EPR spectra of N 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.

From a humorous post to a detailed quantum-chemical study: isocyanate synthesis revisited.

Isocyanates play an essential role in modern manufacturing processes, especially in polyurethane production. There are numerous synthesis strategies for isocyanates both under industrial and laboratory conditions, which do not prevent searching for alternative highly efficient synthetic protocols. Here, we report a detailed theoretical investigation of the mechanism of sulfur dioxide-catalyzed rearrangement of phenylnitrile oxide into phenyl isocyanate, which was first reported in 1977.

Low-temperature motion of the scandium bimetal in endofullerene Sc@C(CHPh).

The spin decoherence of the scandium bimetal in Sc@C(CHPh) is studied at low temperatures (20-120 K) by the electron spin echo technique. The correlation between the magnetic quantum number of the total spin state of the scandium nuclei and the decay rates is established. For the total spin = 5, a decrease of the phase relaxation time by a factor of two is observed by changing the transition from = -1 to = +1 and = -3 at 120 K.

Experimental confirmation of the formation of a spin polariton in dilute solutions of paramagnetic particles.

Spin exchange during random bimolecular collisions of paramagnetic particles in dilute solutions leads to a surprising effect. Collective modes of motion of the average values of the transverse magnetization components (spin coherences) of subensembles of radicals with different resonant frequencies are formed. The elementary excitations of these modes can be considered as quasiparticles.

Scandium dimetallofullerene with a single-electron metal-metal bond as a spectroscopic ruler for EPR measurements.

Measurements of electron paramagnetic resonance (EPR) close to the saturation region of iron-core electromagnets ( 1 Tesla) require precise magnetic field calibration due to nonlinear effects. Endohedral fullerenes Sc@C(CHPh) have unique spectral features due to the large hyperfine interaction (509 MHz) of the delocalized electron with two scandium nuclei ( = 7/2), resulting in a maximum spectral width of 0.25 Tesla.

Temperature-dependent dynamics of endohedral fullerene Sc@C(CHPh) studied by EPR spectroscopy.

Endohedral fullerenes are promising materials for the quantum information and quantum processing due to the unique properties of the electron-nuclear spin system well isolated from the environment inside the fullerene cage. The endofullerene Sc@C(CHPh) features a strong hyperfine interaction between one electron spin 1/2 localized at the Sc dimer and two equivalent Sc nuclear spins 7/2, which yields 64 well resolved EPR transitions. We report a comprehensive analysis of the temperature dependence of the EPR spectrum of Sc@C(CHPh) dissolved in d-toluene measured in a wide temperature range above and below the melting point.

The Viscoelastic Swirled Flow in the Confusor.

A two-dimensional mathematical model for a steady viscoelastic laminar flow in a confusor was developed under the condition of swirled flow imposed at the inlet. Low density polyethylene was considered as a working fluid. Its behavior was described by a two-mode Giesekus model.

Unusually large hyperfine structure of the electron spin levels in an endohedral dimetallofullerene and its spin coherent properties.

We report the synthesis, ESR spectroscopic and spin coherent properties of the dimetallofullerene Sc2@C80(CH2Ph). The single-electron metal-metal bond of the Sc2 dimer inside the fullerene's cage is stabilized with the electron spin density being fully localized at the metal bond. This results in an extraordinary strong hyperfine interaction of the electron spin with the 45Sc nuclear spins with a coupling constant a = 18.

Ferromagnetically Coupled Copper(II) Clusters Incorporated in Functionalized Boltorn H30 Hyperbranched Polymer Architecture: ESR, Magnetic Susceptibility Measurements, and Quantum-Chemical Calculations.

The unusual temperature behavior of the electron spin resonance (ESR) spectra and magnetic properties are experimentally observed in copper(II) complexes with a dendritic ligand based on the Boltorn H30 polymer (Perstorp Specialty Chemicals AB, Sweden) functionalized with fumaric acid residues in a molar ratio of 1:6. The ESR spectra at low temperatures show signs of transition to higher spin states at temperatures below 8-10 K, and the temperature dependences of the integral ESR signal intensities and magnetic susceptibility show the positive deviation from the Curie-Weiss law, thereby pointing to the presence of ferromagnetic exchange interactions in the system under study. The values of the exchange interaction parameters are calculated by quantum-chemical simulation of the possible structure of the copper(II) complex when assuming the formation of trinuclear coordination sites embedded in the hyperbranched polymer structure.

Effect of the Diamagnetic Single-Crystalline Host on the Angular-Resolved Electron Nuclear Double Resonance Experiments: Case of Paramagnetic [BuN][Cu(opba)] Embedded in Diamagnetic [BuN][Ni(opba)].

The electron spin resonance (ESR) and electron nuclear double resonance (ENDOR) spectroscopies are frequently used to determine hyperfine () and quadrupole () tensors for the paramagnetic transition-metal complexes, which knowledge enables estimation of the spin density distribution in the complex and the assessment of magnetic exchange pathways in polynuclear molecular networks. The most accurate results can be obtained if paramagnetic complexes are isolated in a single-crystalline diamagnetic host. In this work we were able to detect angle-resolved ESR/ENDOR spectra of the paramagnetic [BuN][Cu(opba)] (opba = -phenylenebis(oxamato) complex hosted by the single crystal of diamagnetic [BuN][Ni(opba)], which allow recovery of , , and -tensors, all at once.

Deposition of polydisperse gas suspensions with nonlinear resonance oscillations in a closed tube.

The characteristics of the deposition of a polydisperse gas suspension (tobacco smoke) in a closed tube in the mode of transition to shock waves at the first natural frequency are studied experimentally. The natural deposition of tobacco smoke continues for a long time. When the oscillations are excited, the process occurs hundreds of times faster.

Tuning the spin coherence time of Cu(II)-(bis)oxamato and Cu(II)-(bis)oxamidato complexes by advanced ESR pulse protocols.

We have investigated with the pulsed ESR technique at X- and Q-band frequencies the coherence and relaxation of Cu spins = 1/2 in single crystals of diamagnetically diluted mononuclear [-BuN][Cu(opba)] (1%) in the host lattice of [-BuN][Ni(opba)] (99%, opba = -phenylenebis(oxamato)) and of diamagnetically diluted mononuclear [-BuN][Cu(opbo-Pr)] (1%) in the host lattice of [-BuN][Ni(opbo-Pr)] (99%, opbo-Pr = -phenylenebis((propyl)oxamidato)). For that we have measured the electron spin dephasing time at different temperatures with the two-pulse primary echo and with the special Carr-Purcell-Meiboom-Gill (CPMG) multiple microwave pulse sequence. Application of the CPMG protocol has led to a substantial increase of the spin coherence lifetime in both complexes as compared to the primary echo results.

Electron Spin Density on the N-Donor Atoms of Cu(II)-(Bis)oxamidato Complexes As Probed by a Pulse ELDOR Detected NMR.

We have applied the pulse ELDOR detected NMR (EDNMR) technique to determine the tensors of the transferred Cu (S = 1/2) - (14)N (I = 1) hyperfine (HF) interaction in single crystals of diamagnetically diluted mononuclear o-phenylenebis(N(R)-oxamide) complexes of [(n)Bu4N]2[Cu(opboR2)] (R = Et 1, (n)Pr 2) (1%) in a host lattice of [(n)Bu4N]2[Ni(opboR2)] (R = Et 3, (n)Pr 4) (99%) (1@3 and 2@4)). To facilitate the analysis of our EDNMR data and to analyze possible manifestations of the nuclear quadrupole interaction in the EDNMR spectra, we have treated a model electron-nuclear system of the coupled S = 1/2 and I = 1 spins using the spin density matrix formalism. It appears that this interaction yields a peculiar asymmetry of the EDMR spectra that manifests not only in the shift of the positions of the EDNMR lines that correspond to the forbidden EPR transitions, as expected, but also in the intensities of the EDNMR lines.

Magnetic superexchange interactions: trinuclear bis(oxamidato) versus bis(oxamato) type complexes.

The diethyl ester of o-phenylenebis(oxamic acid) (opbaH2Et2) was treated with an excess of RNH2 in MeOH to cause the exclusive formation of the respective o-phenylenebis(N(R)-oxamides) (opboH4R2, R = Me , Et , (n)Pr ) in good yields. Treatment of with half an equivalent of [Cu2(AcO)4(H2O)2] or one equivalent of [Ni(AcO)2(H2O)4] followed by the addition of four equivalents of [(n)Bu4N]OH resulted in the formation of mononuclear bis(oxamidato) type complexes [(n)Bu4N]2[M(opboR2)] (M = Ni, R = Me , Et , (n)Pr ; M = Cu, R = Me , Et , (n)Pr ). By addition of two equivalents of [Cu(pmdta)(NO3)2] to MeCN solutions of , novel trinuclear complexes [Cu3(opboR2)(L)2](NO3)2 (L = pmdta, R = Me , Et , (n)Pr ) could be obtained.

Anisotropic pseudorotation of the photoexcited triplet state of fullerene C60 in molecular glasses studied by pulse EPR.

Spin-polarized echo-detected electron paramagnetic resonance (EPR) spectra and the transversal relaxation rate T2(-1) of the photoexcited triplet state of fullerene C60 molecules were studied in o-terphenyl, 1-methylnaphthalene, and decalin glassy matrices. The model is composed of a fast (correlation time approximately 10(-12) s) pseudorotation of (3)C60 in a local anisotropic potential created by interaction of the fullerene molecule with the surrounding matrix molecules. In simulations, this potential is assumed to be axially symmetric around some axis of a preferable orientation in a matrix cage.

[Endovascular embolization of arteriovenous fistulas of the lungs (a review of the literature and our own data)].

The authors analyze the literature data and their own experience in endovascular closure of arteriovenous lung fistulas: 20 fistulas were closed in 12 patients, in whom transcutaneous catheterization of the pulmonary artery was performed. Large-frame angiopulmonography made it possible to reveal 10 common arteriovenous lung fistulas (7 single and 3 multiple ones). Afterwards the diagnostic procedure was turned into a therapeutic one.

[Endovascular embolization of arteriovenous lung fistulas (review of literature and own results)].

The authors analyze the literature data on and their own experience in endovascular closure of arteriovenous lung fistulas: 20 fistulas were closed in 12 patients, in whom transcutaneous catheterization of the pulmonary artery was performed. Large-frame angiopulmonography made it possible to reveal 10 common arteriovenous lung fistulas (7 single and 3 multiple ones). Afterwards the diagnostic procedure was turned into a therapeutic one.