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In this study, the performance of the doubles-corrected higher random-phase approximation [HRPA(D)] has been investigated in calculations of nuclear magnetic resonance spin–spin coupling constants (SSCCs) for 58 molecules with the experimental values used as the reference values. HRPA(D) is an approximation to the second-order polarization propagator approximation (SOPPA) and is, therefore, computationally less expensive than SOPPA. HRPA(D) performs comparable and sometimes even better than SOPPA, and therefore, when calculating SSCCs, it should be considered as an alternative to SOPPA. Furthermore, it was investigated whether a coupled-cluster singles, doubles and perturbative triples [CCSD(T)] or Møller-Plesset second order (MP2) geometry optimization was optimal for a SOPPA and a HRPA(D) SSCC calculation for eight smaller molecules. CCSD(T) is the optimal geometry optimization for the SOPPA calculation, and MP2 was optimal for HRPA(D) SSCC calculations. [ABSTRACT FROM AUTHOR]

Spin properties are intrinsic characters of electrons. Radical molecules contain unpaired electron(s), and their unique chemical and physical properties make them an ideal platform for investigating spin properties in molecular systems. Among them, the burgeoning interest in stable conjugated diradicals is attributed to their distinctive characteristics, notably the dynamic resonance structures between open-shell and closed-shell forms, the malleability of their spin states, and the profound influence of intermolecular spin–spin interactions. A deep understanding of the spin characteristics of unpaired electrons in stable conjugated diradicals provides guidance for the design, synthesis, and characterization of radical-based materials. In this review, we discuss the unique spin delocalization, spin states, and spin–spin coupling characteristics of conjugated diradicals and emphasize how to precisely control these spin characteristics to understand their role in the molecules and as functional radical materials. [ABSTRACT FROM AUTHOR]

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In this study, the interplay between aromaticity and intermolecular hydrogen bonding was investigated in some heterocyclic compounds using quantum mechanical calculations. The NH ... O intermolecular hydrogen bonds between formamide and NH and CO functional groups of the selected compounds enhance the delocalisation of the six-membered ring electron cloud, resulting in an increase in the aromaticity of the ring. The contribution of various factors to the binding energy, including the stabilisation energy of the interplay between aromaticity and H-bonding, was estimated using two model systems. The relative binding energies and the estimated stabilisation energies of the aforementioned interplay can be explained by the weights of resonance structures calculated using the natural resonance theory (NRT) analysis with the natural bond orbitals (NBO) method. These weights reflect the tendency of ring nitrogen lone pairs to contribute to the π electron cloud of the ring. The results of the topological analysis of electron charge densities using the atoms in molecules (AIM) method were used to estimate the aromaticity of the ring. Aromaticity indices, particularly nucleus-independent chemical shifts (NICS) calculated one angstrom above the ring plane, are in good linear correlation with the estimated stabilisation energies and electron density at the H-bond critical points. The sum of the total nuclear spin–spin coupling 1J of adjacent atoms of the ring (Σ1J), and the J values of H-bond donor and H-bond acceptor atoms, 1HJNO, which are in good agreement with the energy data and aromaticity indices, can be used as measures of the interplay between aromaticity and H-bonding. The interplay between H-bonding and the aromaticity of the ring is clearly evident from the changes in the pattern of the molecular electrostatic potential (MEP) contour maps at 1.7 Å above the plane of the molecule upon H-bond complexation. [ABSTRACT FROM AUTHOR]

Hamiltonian formalisms provide powerful tools for the computation of approximate analytic solutions of the Einstein field equations. The post-Newtonian computations of the explicit analytic dynamics and motion of compact binaries are discussed within the most often applied Arnowitt–Deser–Misner formalism. The obtention of autonomous Hamiltonians is achieved by the transition to Routhians. Order reduction of higher derivative Hamiltonians results in standard Hamiltonians. Tetrad representation of general relativity is introduced for the tackling of compact binaries with spinning components. Compact objects are modeled by use of Dirac delta functions and their derivatives. Consistency is achieved through transition to d-dimensional space and application of dimensional regularization. At the fourth post-Newtonian level, tail contributions to the binding energy show up for the first time. The conservative dynamics of binary systems finds explicit presentation and discussion through the fifth post-Newtonian order for spinless masses. For masses with spin Hamiltonians are known through (next-to) 3 -leading-order spin-orbit and spin-spin couplings as well as through next-to-leading order cubic and quartic in spin interactions. Parts of those are given explicitly. Tidal-interaction Hamiltonians are considered through (next-to) 2 -leading post-Newtonian order. The radiation reaction dynamics is presented explicitly through the third-and-half post-Newtonian order for spinless objects, and, for spinning bodies, to leading-order in the spin-orbit and spin1-spin2 couplings. The most important historical issues get pointed out. [ABSTRACT FROM AUTHOR]

Tumor hypoxia plays an important role in the clinical management and treatment planning of various cancers. The use of 2-nitroimidazole-based radiopharmaceuticals has been the most successful for positron emission tomography (PET) and single photon emission computed tomography (SPECT) imaging probes, offering noninvasive means to assess tumor hypoxia. In this study we performed detailed computational investigations of the most used compounds for PET imaging, focusing on those derived from 2-nitroimidazole: fluoromisonidazole (FMISO), fluoroazomycin arabinoside (FAZA), fluoroetanidazole (FETA), fluoroerythronitroimidazole (FETNIM) and 2-(2-nitroimidazol-1-yl)-N-(2,2,3,3,3-pentafluoropropyl)acetamide (EF5). Conformational analysis, structural parameters, vibrational IR and Raman properties (within both harmonic and anharmonic approximations), as well as the NMR shielding tensors and spin-spin coupling constants were obtained by density functional theory (DFT) calculations and then correlated with experimental findings, where available. Furthermore, time-dependent DFT computations reveal insight into the excited states of the compounds. Our results predict a significant change in the conformational landscape of most of the investigated compounds when transitioning from the gas phase to aqueous solution. According to computational data, the 2-nitroimidazole moiety determines to a large extent the spectroscopic properties of its derivatives. Due to the limited structural information available in the current literature for the investigated compounds, the findings presented herein deepen the current understanding of the electronic structures of these five radiopharmaceuticals. [ABSTRACT FROM AUTHOR]

The manuscript discusses the concepts of spin–orbit and spin–spin coupling in atomic physics and Molecular Quantum Similarity (MQS) in molecular clusters. spin–orbit and spin–spin coupling arises from the interaction between an electron's spin and its motion around the nucleus and electron–electron interaction and plays a crucial role in determining energy levels and spectral lines in atoms with heavy nuclei. On the other hand, MQS is a computational approach to compare the electronic density distributions in different molecular systems. In this order of ideas, the study aims to answer questions about electronic and structural differences caused by the spin–orbit and spin–spin coupling from the initial geometry [Steradians (SR) geometry] using the MQS framework. The MQS is based on the Molecular Quantum Similarity Measure (MQSM) using different positive operators such as Dirac delta and Coulomb operators to quantify the similarity between molecular systems. The paper presents tables with MQSM indices and Euclidean distances for different molecular clusters using initial geometry vs. geometry involved spin–orbit and spin–spin coupling. The scalar, spin–orbit and spin–spin relativistic coupling were incorporated using Amsterdam Density Functional code. The results show significant coupling of spin–orbit and spin–spin coupling on the similarity measures between different molecules. The manuscript suggests that understanding the relationship between spin–orbit and spin–spin coupling and quantum similarity could lead to deeper insights into electronic interactions in complex molecular systems and has potential applications in quantum mechanics and molecular physics. [ABSTRACT FROM AUTHOR]

The modular path integral methodology is used to extend the well-known spin-boson dynamics to finite-length quantum Ising chains, where each spin is coupled to a dissipative harmonic bath. The chain is initially prepared in the ferromagnetic phase where all spins are aligned, and the magnetization is calculated with spin–spin coupling parameters corresponding to the paramagnetic phase, mimicking a quantum quench experiment. The observed dynamics is found to depend significantly on the location of the tagged spin. In the absence of a dissipative bath, the time evolution displays irregular patterns that arise from multiple frequencies associated with the eigenvalues of the chain Hamiltonian. Coupling of each spin to a harmonic bath leads to smoother dynamics, with damping effects that are stronger compared to those observed in the spin-boson model and more prominent in interior spins, a consequence of additional damping from the spin environment. Interior spins exhibit a transition from underdamped oscillatory to overdamped monotonic dynamics as the temperature, spin–bath, or spin–spin coupling is increased. In addition to these behaviors, a new dynamical pattern emerges in the evolution of edge spins with strong spin–spin coupling at low and intermediate temperatures, where the magnetization oscillates either above or below the equilibrium value. [ABSTRACT FROM AUTHOR]

Covalently‐linked chromophore‐radical systems with their unique optical and magnetic properties are useful for applications in, e. g., quantum information science. To expand the catalog of molecular systems, we synthesized and characterized six novel chromophore–radical and radical‐chromophore‐radical systems employing derivatives of perylene diimide (PDI) as the chromophore and trityl as the radical. The EPR properties of these compounds were evaluated in solution at cryogenic and room temperatures. In addition, the electron spin‐spin coupling in the two bistrityl systems was investigated using DQC measurements. The presented results serve as a basis for further spectroscopic investigations under photoexcitation of the PDI core. [ABSTRACT FROM AUTHOR]

Theoretical decomposition of "through space" spin–spin coupling constants (SSCCs) in organofluorine compounds signal that intramolecular hydrogen bonds (H-bonds) are not the primary mechanism of transmission for SSCCs. Increasing solvent polarity may disrupt H-bonds, but not necessarily the JFH SSCC. Substituent effects may drastically alter the SSCC transmission pathway. Accurate SSCC analysis requires benchmarking theoretical calculations to support experimental data interpretation. [ABSTRACT FROM AUTHOR]

The class of two-interacting-qubit spin–boson models with vanishing transverse fields on the spin-pair is studied. The model can be mapped exactly into two independent standard single-impurity spin–boson models where the role of the tunneling parameter is played by the spin–spin coupling. The dynamics of the magnetization are analyzed for different levels of (an)isotropy. The existence of a decoherence-free subspace, as well as of different classical regimes separated by a critical temperature, and symptoms of quantum (first-order and Kosterlitz–Thouless type) phase transitions in the Ohmic regime are brought to light. [ABSTRACT FROM AUTHOR]

The multi-configurational short-range (sr) density functional theory has been extended to the calculation of indirect spin–spin coupling constants (SSCCs) for nuclear magnetic resonance spectroscopy. The performance of the new method is compared to Kohn–Sham density functional theory and the ab initio complete active space self-consistent field for a selected set of molecules with good reference values. Two density functionals have been considered, the local density approximation srLDA and srPBE from the GGA class of functionals. All srDFT calculations are of Hartree–Fock-type HF-srDFT or complete active space-type CAS-srDFT. In all cases, the calculated SSCC values are of the same quality for srLDA and srPBE functionals, suggesting that one should use the computationally cost-effective srLDA functionals in applications. For all the calculated SSCCs in organic compounds, the best choice is HF-srDFT; the more expensive CAS-srDFT does not provide better values for these single-reference molecules. Fluorine is a challenge; in particular, the FF, FC, and FO couplings have much higher statistical errors than the rest. For SSCCs involving fluorine and a metal atom CAS-srDFT with singlet, generalized Tamm–Dancoff approximation is needed to get good SSCC values although the reference ground state is not a multi-reference case. For V F 6 − 1 , all other considered models fail blatantly. [ABSTRACT FROM AUTHOR]

A new treatment is presented to account for the extreme anomalous centrifugal distortion displayed by the open-shell methylene radical. This new treatment is based on a four-dimensional approach in which both the overall rotation and the large amplitude bending mode are treated simultaneously. It accounts for the spin–rotation and spin–spin fine couplings, assumed to depend on the large amplitude bending coordinate, as well as for the hyperfine coupling. The new treatment is tested analyzing the available high-resolution data. 336 transitions, involving the ground and first excited vibrational states of the bending mode, are reproduced with a unitless standard deviation of 1.3, using 42 molecular constants. Compared to a previous analysis [S. Brünken et al., J. Chem. Phys. 123, 164315 (2005)], the present analysis is more satisfactory as it accounts for a larger dataset and the ratio of the number of data to the number of varied constants is larger. The present theoretical treatment also allows us to retrieve the bending potential and the main kinetic energy term. [ABSTRACT FROM AUTHOR]

This paper investigates the capability of the anisotropic Heisenberg XY model to generate different anisotropic-two-qubit-Heisenberg nonclassical information resources (as Bell nonlocality, steerability, uncertainty-induced nonlocality as well as the concurrence) under x-projection external magnetic field, spin–spin couplings, anisotropy, and intrinsic decoherence. Based on Milburn's intrinsic decoherence model, a particular dynamics for the anisotropic two-qubit Heisenberg XY model has been found to explore the nonclassical information dynamics. The results show that the anisotropic two-qubit Heisenberg couplings have a high ability to generate different nonclassical correlations. The amplitudes, fluctuations, and regularity of the nonclassical correlation dynamics can be controlled by the increase of the external magnetic field, the spin–spin interaction, the anisotropy, and the decoherence. Increasing the anisotropic two-qubit Heisenberg couplings enhances the generation, acceleration, and preservation of the generated two-qubit nonclassical information resources. For the intrinsic decoherence, the generated information resources decrease. The concurrence, steering, and UIN grow and stabilize to their partial stationary correlations, which depend on the applied external magnetic field, the spin couplings, the anisotropy, as well as the decoherence. [ABSTRACT FROM AUTHOR]

This paper investigates the dynamics of two-spin nonlocality generation in a Heisenberg XXX chain with Dzyaloshinskii-Moriya (DM) and Kaplan-Shekhtman-Entin-Wohlman-Aharony (KSEA) interactions. We analyze the two-spin nonlocality dynamics by using uncertainty-induced nonlocality, maximal Bell function, and log-negativity. We demonstrate that a separable two-spin Heisenberg XXX chain state, induced by two-spin antiferromagnetic interaction as well as x-component of DM and KSEA interactions, could evolve to maximal two-spin nonlocality state. The ability of preserving the maximal uncertainty-induced nonlocality can be enhanced by increasing the coupling strength of the spin-spin interaction coupling. The hierarchy principle is maintained for the two-spin Bell nonlocality and log-negativity entanglement. The two-spin log-negativity dynamics exhibits the phenomena of sudden death and birth. The sudden-death phenomenon is due to the intrinsic decoherence, which also causes a reduction in the two-spin nonlocality. While the sudden-birth phenomenon is due to two-spin antiferromagnetic interaction as well as x-component of DM and KSEA interactions. The two-spin uncertainty-induced nonlocality is more robust, against the intrinsic decoherence, than the other types of the nonlocality. The results indicate that by boosting the two-spin antiferromagnetic interaction, the produced nonlocality (resulting from the DM and KSEA x-component interactions) can be shielded from the intrinsic decoherence effect. [ABSTRACT FROM AUTHOR]

The conformational properties of monosaccharides constitute fundamental features of oligosaccharides. While the energy landscape of monosaccharides can be altered by a specific biochemical environment or by chemical modifications, the analysis of resulting dynamic conformational equilibria is not feasible by experimental means alone. In this work, a series of β‐d‐xylopyranosides is used to outline how a combination of experimental NMR parameters and computed molecular properties can be used to determine conformers and quantify the composition of conformational equilibria. We demonstrate that identifying the most stable conformers using energy calculations is challenging and computing of NMR shieldings is typically not sensitive enough. On the other hand, computed spin‐spin coupling constants for the xyloside ring can be used to unambiguously assign experimental NMR data of dynamic conformational equilibria and quantify the ratio of different conformers in the mixture. As a proof of principle, this procedure allowed to analyze a hitherto unknown dynamic equilibrium of a diamino‐xyloside as a precursor of a molecular switch. [ABSTRACT FROM AUTHOR]

All possible spin–spin coupling constants, 19F–19F, 19F–13C, and 19F–1H, of pentafluorobenzene were calculated at five different levels of theory, HF, DFT, SOPPA (CCSD), CCSD, and the SOPPA (CCSD)‐based composite scheme with taking into account solvent, vibrational, relativistic, and correlation corrections. Most corrections were next to negligible for the long‐range couplings but quite essential for the one‐bond carbon–fluorine coupling constants. Hartree–Fock calculations were found to be entirely unreliable, while DFT results were comparable in accuracy with the data obtained using the wave function‐based methods. [ABSTRACT FROM AUTHOR]

The lace expansion for the Ising two-point function was successfully derived in (Sakai in Commun Math Phys 272:283–344, 2007, Proposition 1.1). It is an identity that involves an alternating series of lace-expansion coefficients. In the same paper, we claimed that the expansion coefficients obey certain diagrammatic bounds which imply faster x-space decay (as the two-point function cubed) above the critical dimension d c ( = 4 for finite-variance models) if the spin-spin coupling is ferromagnetic, translation-invariant, summable and symmetric with respect to the underlying lattice symmetries. However, we recently found a flaw in the proof of (Sakai in Commun Math Phys 272:283–344, 2007, Lemma 4.2), a key lemma to the aforementioned diagrammatic bounds. In this paper, we no longer use the problematic (Sakai 2007, Lemma 4.2), and prove new diagrammatic bounds on the expansion coefficients that are slightly more complicated than those in (Sakai 2007, Proposition 4.1) but nonetheless obey the same fast decay above the critical dimension d c . Consequently, the lace-expansion results for the Ising and φ 4 models in the literature are all saved. The proof is based on the random-current representation and its source-switching technique of Griffiths, Hurst and Sherman, combined with a double expansion: a lace expansion for the lace-expansion coefficients. [ABSTRACT FROM AUTHOR]

Permanently deformed objects in binary systems can experience complex rotation evolution, arising from the extensively studied effect of spin–orbit coupling as well as more nuanced dynamics arising from spin–spin interactions. The ability of an object to sustain an aspheroidal shape largely determines whether or not it will exhibit nontrivial rotational behavior. In this work, we adopt a simplified model of a gravitationally interacting primary and satellite pair, where each body's quadrupole moment is approximated by two diametrically opposed point masses. After calculating the net gravitational torque on the satellite from the primary, as well as the associated equations of motion, we employ a Hamiltonian formalism that allows for a perturbative treatment of the spin–orbit and retrograde and prograde spin–spin coupling states. By analyzing the resonances individually and collectively, we determine the criteria for resonance overlap and the onset of chaos, as a function of orbital and geometric properties of the binary. We extend the 2D planar geometry to calculate the obliquity evolution. This calculation indicates that satellites in spin–spin resonances undergo precession when inclined out of the plane, but they do not tumble. We apply our resonance overlap criteria to the contact binary system (216) Kleopatra, and find that its satellites, Cleoselene and Alexhelios, may plausibly be exhibiting chaotic rotational dynamics from the overlap of the spin–orbit and retrograde spin–spin resonances. While this model is, by construction, generalizable to any binary system, it will be particularly useful for studies of small bodies in the Solar System, whose irregular shapes make them ideal candidates for exotic rotational states. [ABSTRACT FROM AUTHOR]

Purpose: Imaging of [2‐13C]lactate, a metabolic product of [2‐13C]pyruvate, is over considerable interest in hyperpolarized 13C studies. However, artifact‐free imaging of a J‐coupled nuclear spin species can be challenging due to the peak‐splitting induced by the spin‐spin interactions. In this work, two new techniques resolving these J‐modulated artifacts are presented. Theory and Methods: The Product Operator Formalism (POF) of density matrix theory is used to both numerically and analytically derive the coherences arising during radiofrequency excitation and readout of a J‐coupled spin system. A combination of computer simulations and experiments with [2‐13C]lactate and 13C‐formate phantoms are then used to verify the performance of two imaging methods. In the first approach, a quadrature imaging technique is used to eliminate scalar coupling artifacts via the combination of in‐phase and quadrature images acquired at echo times differing by 1/2J with an echoplanar readout. The second approach employs a highly narrowband RF excitation pulse to image a single peak from the J‐coupled doublet. Results: Simulations using a numerical Shepp‐Logan phantom, in vitro experiments using thermally polarized [2‐13C]lactate, thermally and hyperpolarized 13C‐formate phantoms, and in vivo imaging of [2‐13C]lactate produced in rat brain following injection of hyperpolarized [2‐13C]pyruvate show artifact‐free images and demonstrate potential utility of these methods. Conclusion: The quadrature imaging and the narrowband excitation techniques resolve the J‐coupling induced ghosting and blurring artifacts present with conventional MRI of J‐coupled signals such as [2‐13C]lactate. [ABSTRACT FROM AUTHOR]

Dual field driven caloric effect has aroused great interest in recent years. Hydrostatic pressure can shift the temperature zone of magnetocaloric effect(MCE), but seldom enhance its magnitude. Here, a large enhancement of MCE driven by pressure under magnetic field available by permanent magnet has been achieved in HoCuSi compound without introducing hysteresis loss, which is favorable for developing hybrid field driven refrigeration applications at low temperature regions. A distinct mechanism is revealed. Pressure largely regulates non-collinear spin structure and magnetizing process through affecting crystal field interactions and spin-spin coupling, hence resulting in the significant impact on magnetic properties and MCE. Image, graphical abstract [ABSTRACT FROM AUTHOR]

We consider the SU(3) spin–orbit coupled spin-1 Bose–Einstein condensates in a two-dimensional harmonic trap. The competition between the SU(3) spin–orbit coupling and the spin-exchange interaction results in a rich variety of lattice configurations. The ground-state phase diagram spanned by the isotropic SU(3) spin–orbit coupling and the spin–spin interaction is presented. Five ground-state phases can be identified on the phase diagram, including the plane wave phase, the stripe phase, the kagome lattice phase, the stripe-honeycomb lattice phase, and the honeycomb hexagonal lattice phase. The system undergoes a sequence of phase transitions from the rectangular lattice phase to the honeycomb hexagonal lattice phase, and to the triangular lattice phase in spin-1 Bose–Einstein condensates with anisotrpic SU(3) spin–orbit coupling. [ABSTRACT FROM AUTHOR]

Nuclear magnetic resonance (NMR) is a robust method for the analysis of molecular complex structures, and the measurement of the nuclear spin–spin coupling constant is the key. In this paper, based on the 3D coordinates of the atoms in the molecule, the spin–spin coupling constants of atom-pairs are directly predicted using Extreme Gradient Boosting (XGBoost) and Light Gradient Boosting Machine (LightGBM). The calculated result of DFT method is taken as the target value. Experiment shows that LightGBM (R2: 0.93) overall performance is better than XGBoost. In some molecules, the predicted fit (R2) of the coupling constant between atoms even reached 1.00. This research avoids complex quantum mechanics and can assist in NMR to gain insight into the structure and dynamics of molecules, thereby enriching the data information analysis method of nuclear magnetic interaction. [ABSTRACT FROM AUTHOR]

[Display omitted] • Reversible exchange with catalyst induces para–ortho conversion of parahydrogen. • The para–ortho conversion rate non-monotonously depends on magnetic field. • Conversion rate increases with increasing the concentration of catalyst. • Magnetic interactions of nuclei are encoded in field dependence of conversion. • Energy level anti-crossing boosts conversion of parahydrogen. The use of parahydrogen – the isomer of molecular hydrogen with zero nuclear spin – is important for promising and actively developing methods for spin hyperpolarization of nuclei called parahydrogen induced polarization (PHIP). However, the dissolved parahydrogen in PHIP experiments quickly loses its spin order, resulting in the formation of orthohydrogen and reduction of the overall nuclear polarization of the substrate. This process is due to the difference of chemical shifts of hydride protons, as well as spin–spin couplings between nuclei, in the intermediate catalytic complexes, and it has not been rigorously explained so far. We proposed a new experimental technique based on magnetic field cycling for measuring the rate of molecular hydrogen para–ortho conversion in solution and applied it for non-hydrogenative PHIP Signal Amplification By Reversible Exchange (SABRE) experiments. The para–ortho conversion rate was measured over a wide range of magnetic field from 0.5 mT to 9.4 T. It was found that the conversion rate strongly depends on the magnetic field in which the reaction occurs, as well as on the concentrations of reactants. The rate decreases with increasing the concentration of pyridine ligand and increases with increasing the concentration of iridium catalyst. The model, which takes into account the reversible exchange of molecular hydrogen with the catalyst, nuclear spin–spin interaction of hydride protons with nuclei of ligands within catalytic complex and nuclear Zeeman interactions, qualitatively describes the experimental data. Two types of complexes with different spin system symmetry contribute to the molecular hydrogen conversion. In asymmetric complexes possessing hydride protons with different chemical shifts due to the presence of chlorine anion ligand the para–ortho conversion rate increases with magnetic field, while for symmetric complexes this mechanism is not operable. In the magnetic field where level anti-crossing occurs the resonant feature for the rate of para–ortho conversion is found. The results of this work can be utilized for finding the optimal conditions for obtaining the maximum hyperpolarization in the experiments employing parahydrogen. [ABSTRACT FROM AUTHOR]

The design and implementation of a software package for the analysis of single-crystal NMR data is presented. The SCFit software can treat spectra arising from various interactions: (i) chemical shift tensor only; (ii) chemical shift tensor and quadrupolar coupling tensor; (iii) dipolar and indirect nuclear spin-spin coupling tensors; (iv) all four interactions. The software is demonstrated on recently reported 17O and 31P single-crystal NMR data for triphenylphosphine oxide and for two of its halogen-bonded cocrystals. The 17O single-crystal NMR data represent a case where all four above-mentioned interactions simultaneously affect the spectra. SCFit can fit the chemical shift and quadrupolar coupling in two ways: (i) through an unconstrained fitting process where all tensor parameters are freely optimized or (ii) through a constrained fitting process where the principal components of the tensors may be fixed to values known previously with high precision via the analysis of powder samples. The second strategy is explored in an effort to reduce the number of unknowns in the fitting process; an improvement in the precision of the resulting tensor orientations is noted in some cases. Image 1 • SCFit software for analyzing single-crystal NMR data is described. • Chemical shift, quadrupolar, and spin-spin coupling interactions are treated. • The utility of fixing tensor magnitudes to known values is explored. [ABSTRACT FROM AUTHOR]

Experimentally observed with dielectric disk resonator technique, microwave absorption–amplification in liquid He II below λ -point has been interpreted theoretically as a phenomenon in electrically active dielectric medium with low-energy excitations which exist near the ground state of the four-electron He–He interatomic bond due to spin–spin and spin–phonon coupling. The experimentally registered microwave absorption line is f 0 = 180.3 GHz at T = 1.4 K and f 0 = 150.0 GHz at T = 2.1 K which strongly corresponds to the values of roton gap known from neutron diffractometry. Our theoretical estimation gives only an upper limit > 250 GHz for resonant response of the system. We interpret the dielectric 4 He superfluid as a working substance for low-temperature MASER and clarify the atomic mechanism of microwave absorption–amplification in the condensed helium phases. [ABSTRACT FROM AUTHOR]

Through-space spin–spin coupling constants (SSCCs) involving fluorine are computed applying Density Functional Theory and compared with experimental data to benchmark the performance of various functionals. In addition to the most often analysed J(FF) constants, we consider examples of J(FN), J(FP), J(FC) and J(FSe) constants. Basis sets optimised for the study of SSCCs are applied and thus we find the choice of the functional to be more important than the choice of the basis set. Different performance of DFT functionals is observed for different SSCCs, with the hybrid DFT functionals generally superior for the through-space couplings. When all the SSCCs are considered, PBE0 appears to be the most robust functional. [ABSTRACT FROM AUTHOR]

We have found some typing mistakes on p. 3534 in the original article.[1] At the right-hand side of Eq. (24), HT ht should read HT ht . Erratum: "Calculation of nuclear spin-spin couplings. At the right-hand side of Eq. (25), I F i SB I mn i sb and I F i SB I lm i sb should read HT ht and HT ht , respectively. [Extracted from the article]

The J CH fate of acetylene at different roadways. [Display omitted] • The superbasic DMSO/KOH system drastically changes NMR pattern of acetylene. • The coalescence of J CH of acetylene is observed under superbasic conditions. • The possible chemical exchange reactions of hydrogen atoms between acetylene, acetylide, and hydroxyl group were proposed. • The temperature effects and addition of water and acid on the observed chemical exchange were studied. • The observed chemical exchange reaction may assist in understanding the mechanism of addition reactions with acetylene. Acetylene is a key industrial building block with a reach functionalization chemistry under strong basic (i.e., so called, superbasic) conditions in solution. In spite of significance of such acetylene transformations, mechanistic understanding of liquid-phase processes at molecular level under superbasic conditions remains a challenge. In the present study, a detailed comparative analysis of several factors influencing acetylene in solution was performed using NMR spectroscopy. Solvent effects, deuterium isotope effects, and temperature effects were estimated on experimental J CH spin–spin coupling constants and the chemical shift difference of Δδ C , and their possible outcome on acetylene bond length were assessed. Acetylene was studied under superbasic conditions in DMSO/KOH mixtures, and chemical exchange processes were observed, manifesting themselves as a coalescence of J CH. Possible exchange reactions are validated by quantum chemical calculations. The studied phenomenon may shed light on the mechanism of acetylene activation under superbasic conditions and contribute to understanding functionalization chemistry in the liquid phase. [ABSTRACT FROM AUTHOR]

Students analyzed a set of 34 carboxylic esters using ¹H nuclear magnetic resonance (NMR) spectroscopy to examine paradigmatic examples of spin-spin coupling, a foundational concept used to determine molecular structure by NMR spectroscopy. The ester functional group provides excellent chemical shift dispersion so that students were able to analyze well-resolved peaks and to apply concepts of chemical shift, line shape, and integration to the analysis of molecular substructures. A laboratory activity combining molecular models, worksheets, and NMR data collection and analysis provided students with the ability to predict and to analyze spectra representing spin-spin splitting for N = 0-6 (where N is the number of three-bond neighbors that are hydrogens). [ABSTRACT FROM AUTHOR]

We derive expressions for density-density and spin-spin correlation functions in the (greatly enhanced) pseudogap phase of spin-orbit-coupled Fermi gases. Density-density correlation functions are found to be relatively insensitive to the presence of these Rashba spin-orbit effects. To arrive at spin-spin correlation functions we derive new f-sum rules, valid even in the absence of a spin conservation law. Our spin-spin correlation functions are shown to be fully consistent with these f-sum rules. Importantly, they provide a clear signature of the Rashba band structure and separately help to establish the presence of a pseudogap. [ABSTRACT FROM AUTHOR]

A systematic theoretical study of geminal and vicinal 77Se-13C spin-spin coupling constants in the series of the open-chain selenides and selenium-containing heterocycles revealed that relativistic effects play an essential role in the selenium-carbon coupling mechanism, especially when the coupling pathway includes a triple bond, contributing to about 10-15% of their total values and noticeably improving the agreement of the calculated couplings with experiment. Both geminal and vicinal 77Se-13C spin-spin coupling constants show marked stereochemical behavior as documented by their calculated dihedral angle dependence that could be used as a practical guide in stereochemical studies of organoselenium compounds. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The resonance-assisted hydrogen bond (HB) phenomenon has been studied theoretically by a localized molecular orbital (LMO) decomposition of the spin-spin coupling constants between atoms either involved or close to the O-H · · · O system of some β-diketones and their saturated counterparts. The analysis, carried out at the level of the second-order polarization propagator approximation, shows that the contributions in terms of LMO to the paramagnetic spin orbital and the spin dipolar Ramsey terms proof the importance of the delocalized π-electron structure supporting the idea of the existence of the resonance-assisted HB phenomenon phenomenon. The LMO contributions to the Fermi contact term indicate mainly the presence of the HB that may or not be linked to the π-electrons. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Coupling of the spin and orbital degrees of freedom on the surface of a strong three-dimensional insulator, on the one hand, and textured magnetic configuration in an adjacent ferromagnetic film, on the other, is studied using a combination of transport and thermodynamic considerations. Expressing exchange coupling between the localized magnetic moments and Dirac electrons in terms of the electrons' out-of-plane orbital and spin magnetizations, we relate the thermodynamic properties of a general ferromagnetic spin texture to the physics in the zeroth Landau level. Persistent currents carried by Dirac electrons endow the magnetic texture with a Dzyaloshinski-Moriya interaction, which exhibits a universal scaling form as a function of electron temperature, chemical potential, and the time-reversal symmetry breaking gap. In addition, the orbital motion of electrons establishes a direct magnetoelectric coupling between the unscreened electric field and local magnetic order, which furnishes complex long-ranged interactions within the magnetic film. [ABSTRACT FROM AUTHOR]

One-bond spin-spin coupling constants involving selenium of seven different types, 1 J(Se,X), X = 1H, 13C, 15 N, 19 F, 29Si, 31P, and 77Se, were calculated in the series of 14 representative compounds at the SOPPA(CCSD) level taking into account relativistic corrections evaluated both at the RPA and DFT levels of theory in comparison with experiment. Relativistic corrections were found to play a major role in the calculation of 1 J(Se,X) reaching as much as almost 170% of the total value of 1 J(Se,Se) and up to 60-70% for the rest of 1 J(Se,X). Scalar relativistic effects (Darwin and mass-velocity corrections) by far dominate over spin-orbit coupling in the total relativistic effects for all 1 J(Se,X). Taking into account relativistic corrections at both random phase approximation and density functional theory levels essentially improves the agreement of theoretical results with experiment. The most 'relativistic' 1 J(Se,Se) demonstrates a marked Karplus-type dihedral angle dependence with respect to the mutual orientation of the selenium lone pairs providing a powerful tool for stereochemical analysis of selenoorganic compounds. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Long-range coupling constants 5 JH ortho,OMe were measured in series of methoxyindoles, methoxycoumarins, and methoxyflavones by the modified J doubling in the frequency domain method. The COSY and NOESY spectra revealed the coupling of the -OMe group with a specific proton at the ortho position and its preferred conformation. Homonuclear 1H-1H couplings were confirmed by irradiation of the -OMe signal. Density functional theory calculations of 5 JH ortho,OMe using the modified aug-cc-pVTZ basis set evidenced that the Fermi contact term shows good agreement with the experimental J values. Accurate chemical shift and coupling constant values followed after iterative quantum mechanical spectral analysis using the PERCH software. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Pairwise quantum correlations in the ground state of an N-spins antiferromagnetic Heisenberg chain are investigated. By varying the exchange coupling between two neighboring sites, it is possible to reversibly drive spins from entangled to disentangled states. For even N, the two-spin density matrix is written in the form of a Werner state, allowing identification of its single parameter with the usual spin-spin correlation function. The N = 4 chain is identified as a promising system for practical demonstrations of non-classical correlations and the realization of Werner states in familiar condensed matter systems. Fabrication and measurement ingredients are within current capabilities. [ABSTRACT FROM AUTHOR]

Abstract: In this contribution the gas-phase measurements of 19F and 29Si chemical shifts and scalar spin–spin couplings in SiF4 and (SiF3)2O have been reported. The density dependence of silicon and fluorine nuclei chemical shifts is strictly linear for both compounds. An extrapolation of gaseous data to the zero-density limit permitted the measurements of 19F and 29Si absolute nuclear magnetic shielding of isolated molecules at 300K. They were referenced against general accepted standards and are as follows: σ 0(SiF 4)=362.87ppm, σ 0(SiF4)=488.15ppm, σ 0((SiF 3)2O)=356.50ppm, and σ 0((SiF3)2O)=487.95ppm. The direct measurements of shielding constants on the basis of NMR frequencies were also performed. Indeed, we have successfully demonstrated the equivalence of both shielding values refinements. Careful investigation of 19F spectra shows isotope effects connected with the presence of three naturally occurring silicon isotopes: 28Si (92.19%), 29Si (4.70%) and 30Si (3.09%). The isotope effect measured on 19F nuclei does not exceed 0.01ppm. The 1 J(Si,F) indirect spin–spin coupling constants in both molecules were extracted from an experimental spectra of gaseous samples. The intermolecular effects in the gaseous state as well as in coming from gas to organic solutions were also observed. The new experimental results were used for verification of the theoretical evaluations presented earlier. [Copyright &y& Elsevier]

A new method was developed for the investigation of an azido-tetrazole equilibrium based on using a complex analysis of C-N and H-N spin-spin coupling constants. The use of this approach became possible due to the selective inclusion of N isotopes into the structures of 2-azidopyrimidines and their cyclic analogs tetrazolo[1,5- a]pyrimidines. [ABSTRACT FROM AUTHOR]

We present a theoretical approach to use ferromagnetic or ferrimagnetic nanoparticles as microwave nanomagnonic cavities to concentrate microwave magnetic fields into deeply subwavelength volumes ∼10-13 mm³. We show that the field in such nanocavities can efficiently couple to isolated spin emitters (spin qubits) positioned close to the nanoparticle surface reaching the single magnon-spin strong-coupling regime and mediate efficient long-range quantum state transfers between isolated spin emitters. Nanomagnonic cavities thus pave the way toward magnon-based quantum networks and magnon-mediated quantum gates. [ABSTRACT FROM AUTHOR]

Hybrid spin-mechanical setups offer a versatile platform for quantum science and technology, but improving the spin-phonon as well as the spin-spin couplings of such systems remains a crucial challenge. Here, we propose and analyze an experimentally feasible and simple method for exponentially enhancing the spin-phonon and the phonon-mediated spin-spin interactions in a hybrid spin-mechanical setup, using only linear resources. Through modulating the spring constant of the mechanical cantilever with a time-dependent pump, we can acquire a tunable and nonlinear (two-phonon) drive to the mechanical mode, thus amplifying the mechanical zero-point fluctuations and directly enhancing the spin-phonon coupling. This method allows the spin-mechanical system to be driven from the weak-coupling regime to the strong-coupling regime, and even the ultrastrong coupling regime. In the dispersive regime, this method gives rise to a large enhancement of the phonon-mediated spin-spin interactions between distant solid-state spins, typically two orders of magnitude larger than that without modulation. As an example, we show that the proposed scheme can apply to generating entangled states of multiple spins with high fidelities even in the presence of large dissipations. [ABSTRACT FROM AUTHOR]

• Pentaphenylantimony reacts with β-diketones to form tetraphenylantimony diketonates. • Antimony atom in the complexes is hexacoordinated. • The ligand coordinates on the metal atom asymmetrically. • The more the substituent electronegativity difference, the larger the asymmetry degree. The reactions of pentaphenylantimony with fluorinated β-diketones have been studied. The structure of the obtained compounds has been determined by the X-ray diffraction method and confirmed by IR, 1H, 13C and 19F NMR spectroscopy. According to X-ray diffraction analysis data, the reaction products are tetraphenylantimony 1,1,1-trifluoropentane-2,4-dionate (3а), 1,1,1-trifluoro-5,5-dimethylhexane-2,4-dionate (3b) and 6,6,7,7,8,8,8-heptafluoro-2,2-dimethyloctane-3,5-dionate (3c): Ph 4 Sb[OC(R)CHC(R')O] (R = CH 3 (3a), Bu- t (3b , 3c); R' = CF 3 (3a , 3b), C 3 F 7 (3c)), the antimony atoms in the molecules have a distorted octahedral coordination. The CSbC angles equal 158.26(14)°, 157.90(9)°, 157.75(15)° (3 a ‒ c), the CSbO angles are 164.70(12)°, 168.05(12)° (3a); 165.47(9)°, 167.37(7)° (3b); 164.96(14)°, 169.66(13)° (3c). The Sb–C bond lengths vary in the ranges of 2.142(4)–2.164(4) Å, 2.144(2)–2.160(2) Å, 2.142(4)–2.160(4) Å (3 a ‒ c), the Sb–O distances are 2.358(3), 2.333(3) Å (3a); 2.306(2), 2.339(2) Å (3b); 2.376(3), 2.289(3) Å (3c). The 3a and 3b 13C NMR spectra contain short spin-spin interactions between carbon and fluorine atoms with a large direct spin-spin coupling constant, 1 J CF ≈ 286.0 Hz, which are characteristic for fluorinated compounds. [ABSTRACT FROM AUTHOR]

Review: 288 refs. [ABSTRACT FROM AUTHOR]