Nonequivalent Atoms Research Articles

Origins of multi-sublattice magnetism and superexchange interactions in double–double perovskite CaMnCrSbO6

The multi-sublattice magnetism and electronic structure in double–double perovskite compound CaMnCrSbO6 is explored using density functional theory. The bulk magnetization and neutron diffraction suggest a ferrimagnetic order ( TC∼ 49 K) between between Mn2+ and Cr3+ spins. Due to the non-equivalent Mn atoms (labelled as Mn(1) and Mn(2) which have tetrahedral and planar oxygen coordinations, respectively) and the Cr atom in the centre of distorted oxygen octahedron in the unit cell, the exchange interactions are more complex than that expected from a two sublattice magnetic system. The separations between the on-site energies of the d-orbitals of Mn(1), Mn(2) and Cr obtained from Wannier function analysis are in agreement with their expected crystal field splitting. While the DOS obtained from non spin-polarized calculations show a metallic character, starting from Hubbard U = 0 eV the spin-polarized electronic structure calculations yield a ferrimagnetic insulating ground state. The band gap increases with Ueff (U − J), thereby showing a Mott–Hubbard nature of the system. The inclusion of anti-site disorder in the calculations show decrease in band-gap and also reduction in the total magnetic moment. Due to the ∼90∘ superexchange, nearest neighbour exchange constants obtained from DFT are an order of magnitude smaller than those reported for various magnetic perovskite and double-perovskite compounds. The Mn(1)–O–Mn(2) (out of plane and in-plane), Mn(1)–O–Cr and Mn(2)–O–Cr superexchange interactions are found to be anti-ferromagnetic, while the Cr–O–O–Cr super-superexchange is found to be ferromagnetic. The Mn(2)–O–Cr superexchange is weaker than the Mn(1)–O–Cr super-exchange, thus effectively resulting in ferrimagnetism. From a simple 3-site Hubbard model, we derived expressions for the antiferromagnetic superexchange strength JAFM and also for the weaker ferromagnetic JFM . The relative strengths of JAFM for the various superexchange interactions are in agreement with those obtained from DFT. The expression for Cr–O–O–Cr super-superexchange strength ( J~SS ), which has been derived considering a 4-site Hubbard model, predicts a ferromagnetic exchange in agreement with DFT. Finally, our mean field calculations reveal that assuming a set of four magnetic sub-lattices for Mn2+ spins and a single magnetic sublattice for Cr3+ spins yields a much improved T C , while a simple two magnetic sublattice model yields a much higher T C .

Role of Doping Effect and Chemical Pressure Effect Introduced by Alkali Metal Substitution on 1144 Iron-Based Superconductors.

CaAFe4As4 with A = K, Rb, and Cs are close to the doped 122 system, and the parent material can reach a superconducting transition temperature of 31-36 K without doping. To study the role of alkali metals, we investigated the induced hole doping and chemical pressure effects as a result of the introduction of alkali metals using density-functional-based methods. These two effects can affect the superconducting transition temperature by changing the number of electrons and the structure of the FeAs conductive layer, respectively. Our study shows that the dxz and dyz orbitals, which are degenerate in CaFe2As2, become nondegenerate in CaAFe4As4 due to two nonequivalent arsenic atoms (As1 and As2). The unusual oblate ellipsoid hole pocket at Γ point in CaAFe4As4 results from a divalent cation Ca2+ replaced by a monovalent cation A+. It shows one of the main differences in fermiology compared to a particular form of CaFe2As2 with reduced 1144 symmetry, due to the enhancement of As2-Fe hybridization. The unusual band appears in CaFe2As2 (1144) and gradually disappears in the change of K to Cs. Further analysis shows that this band is contributed by As1 and has strong dispersion perpendicular to the FeAs layer, suggesting that it is related to the peculiar van Hove singularity below the Fermi level. In addition, various aspects of CaFe2As2 (1144) and CaAFe4As4 in the ground state are discussed in terms of the influence of hole doping and chemical pressure.

Evaluation of Thermal Neutron Scattering Law and Cross Sections for Calcium Hydride

Presented here are the calculated thermal scattering law (TSL) and thermal neutron scattering cross sections for Calcium Hydride, hereafter referred to by its chemical symbol CaH2. The only other such data prior to this evaluation are thermal neutron scattering libraries in the JEFF database, which do not fully capture the scattering physics of the CaH2 system. The data in this evaluation are calculated from first principles; Density Functional Theory (DFT) is used to calculate the phonon density of states (DOS), which is the primary input required to derive the TSL. The TSL and cross sections have been evaluated for the three non-equivalent atom cites in the CaH2: Ca, H1, and H2. Each evaluation has been submitted to the NNDC for consideration in the next ENDF/B database release.

Comparative performance of theoretical tools in order to quantify the effect of the electric potential on the vibrational wavenumbers and intensities of the SERS of 2‐methylpyrazine adsorbed on a nanostructured silver electrode

AbstractThe effect of the electrode potential in surface‐enhanced Raman scattering (SERS) intensities and wavenumbers of 2‐methylpyrazine (2MP) was analyzed on the basis of a resonant charge transfer (CT) mechanism by using a simple theoretical model in which the metallic surface and its charge density were simulated by atomic silver clusters of different size (n) and charge (q), [Agn]q. Two linear silver atoms (n = 2) with zero charge (q = 0) and three linear silver atoms (n = 3) with positive and negative charges (q = ±1) linked to the two nonequivalent aromatic nitrogen atoms in 2MP were taken into account. The wavenumber shifts of the most intense bands and the SERS‐CT spectra of these two types of metal‐adsorbate supermolecule, [Agn‐N1]q and [Agn‐N4]q, were calculated by using a time‐dependent density functional theory (TD‐DFT) method and the independent mode displaced harmonic oscillator (IMDHO) approximation. A comparison of the effect of different levels of calculation, ab initio/DFT, on the predictions from the two theoretical models (isolated adsorbate/supermolecule) is also performed. Only DFT theoretical results of the metal‐adsorbate supermolecule allow to explain the main role of the pair of bands assigned to totally symmetric ring‐stretching 8a,b modes. The 8a vibration is the strongest band at any electrode potential, whereas the 8b mode reaches a maximum enhancement at −0.50 V and then decreases at −0.75 V. This model of a charged metal‐adsorbate interface allows for detecting the presence of a CT mechanism in a SERS record.

Origin of strong Coulomb interactions in borophene: First-principles Wannier function analysis

We report the first-principles Wannier function study of the electronic structure of two polymorphs of borophene: 8-Pmmn and 6-P6/mmm (henceforth denoted as 6-Pmmm) borophene, where 8 and 6 depict the number of nonequivalent atoms per unit cell. Both structures are found to be anisotropic metals with electronic structures dominated by weak inter- and intra-hopping physics, suggesting strongly correlated metallic ground states. Our findings could aid in explaining the recently observed strong Coulomb interaction in related materials such as graphene bilayer.

Binding of Gold(III) from Solutions by the [Ag6{S2CN(CH2)6}6] Cluster: Synthesis, Thermal Behavior, and Self-Organization of the Supramolecular Structure of the Double Complex [Au{S2CN(CH2)6}2]2[AgCl2]Cl\xb72CHCl3 (Role of Secondary Au\u22c5\u22c5\u22c5Cl, Ag\u22c5\u22c5\u22c5S, and Cl\u22c5\u22c5\u22c5Cl Interactions)

The capability of silver(I) cyclo-hexamethylenedithiocarbamate to concentrate gold(III) from solutions characterized by a high level of salinity (5.15 M NaCl) into the solid phase has been established. The double chloroform-solvated Au(III)–Ag(I) complex [Au{S2CN(CH2)6}2]2[AgCl2]Cl·2CHCl3 (I) was preparatively isolated as an individual form of binding of [AuCl4]– anions. The composition of the ionic structural units of compound I indicates that gold(III) binding from a solution to the solid phase is accompanied by the complete redistribution of the HmDtc ligands between the coordination spheres of Ag(I) and Au(III). Complex I characterized by IR spectroscopy, simultaneous thermal analysis, and X-ray structure analysis (CIF file CCDC no. 2051654) exhibits the supramolecular structure containing two oppositely charged pseudo-polymeric subsystems. Complex cations [Au{S2CN(CH2)6}2]+ and anions [AgCl2]– (in a ratio of 2 : 1) form a complicatedly organized cation-anionic pseudo-polymeric ribbon ({[Au(HmDtc)2]⋅⋅⋅[AgCl2]⋅⋅⋅[Au(HmDtc)2]}+)n due to secondary interactions Ag⋅⋅⋅S (3.2613 Å) and Au⋅⋅⋅Cl (3.2765 Å). The pseudo-polymeric ribbon consists of two rows of cations and a row of anions. The outer-sphere chloride ions combine the solvate chloroform molecules by two equivalent hydrogen bonds Cl⋅⋅⋅H–C yielding anion-molecular triads [Cl3CH⋅⋅⋅Cl⋅⋅⋅HCCl3]–, which are involved in the formation of the supramolecular ribbon due to the secondary Cl⋅⋅⋅Cl interactions (3.4058 Å) between the nonequivalent chlorine atoms of the nearest solvate molecules. The study of the thermal behavior of complex I makes it possible to determine the character of thermolysis and conditions for the quantitative regeneration of bound gold.

Unraveling peculiar magnetism and band topology in Mn3Sb

Magnetic, pseudogap, topological, magnetostructural, and elastic behaviors of Mn3Sb have been unraveled. The ferrimagnetism (FIM) is described by localized and delocalized electron magnetism resulting in different magnetic moments on Mn atoms, confirming the neutron diffraction data. The identified magnetostructural properties are due to the non-equivalent Mn atoms in its lowest symmetry structure. The electronic structure is also unique due to variable valance states of Mn atoms. The magnetic moment (4.10 μB) of non-equivalent Mn1 atom is antiparallely aligned with the magnetic moments (2.34 μB) of Mn2 and Mn3 atoms. The estimated Curie temperature, TC, is higher than the room temperature, which may have above the room temperature applications in spintronic devices. The band structure and density of states (DOS) show the characteristics of band topology (opening of a gap in Dirac-like band features) and pseudo-gap, respectively, around the Fermi level. While expanding the unit cell, the tetragonal FIM ground state transforms to the cubic primitive FIM phase, however, the contraction transforms it to the L12 ferromagnetic (FM) phase. The estimated elastic constants, bulk to shear modulus ratio, and elastic anisotropy factor indicate that Mn3Sb exhibits mechanically stable, ductile, and anisotropic behaviors, respectively.

Effect of Electron Doping on the Crystal Structure and Physical Properties of an n = 3 Ruddlesden–Popper Compound La4Ni3O10

The physical properties of La4Ni3O10 with a two-dimensional (2D)-like Ruddlesden–Popper-type crystal structure are extraordinarily dependent on temperature and chemical substitution. By introducing Al3+ atoms randomly at Ni sites, the average oxidation state for the two nonequivalent Ni cations is tuned and adopts values below the average of +2.67 in La4Ni3O10. La4Ni3–xAlxO10 is a solid solution for 0.00 ≤ x ≤ 1.00 and is prepared by the citric acid method, with attention paid to compositional control and homogeneity at low Al level (x) concentrations. The samples adopt a slightly distorted monoclinic structure [P21/a (Z = 4)], evidenced by peak broadening of the (117) reflection. We report a remarkable effect on the electronic properties induced by tiny amounts of homogeneously distributed Al cations, with clear correspondence between resistivity, magnetization, diffraction, and density functional theory (DFT) data. DFT shows that electronically, there is no significant difference between the nonequivalent Ni atoms and no tendency toward any Ni3+/Ni2+ charge ordering. The resistivity changes from metallic to semiconducting/insulating with increasing band gap at higher Al levels, consistent with results from DFT. The metal-to-metal (M-T-M) transition reported for La4Ni3O10, which is often interpreted as a charge density wave, is maintained until x = 0.15 Al level. However, the temperature characteristics of the resistivity change already at very low Al levels (x ≤ 0.03). A coupling of the M-T-M transition to the lattice is evidenced by an anomaly in the unit cell dimensions. Moreover, there is an excellent correlation between the resistivity and magnetization data shown by the metallic and Pauli paramagnetic regime for La4Ni3–xAlxO10 with x < 0.25. The introduction of the fixed +3 oxidation state of Al atoms randomly at the Ni sites reduces the overall oxidation state of Ni2.67+ by keeping the oxygen stoichiometry unchanged. In addition, the nonmagnetic Al3+ for Ni is likely to block Ni–O–Ni exchange pathways through −Ni–O–Al–O–Ni– fragments into the network of corner-shared octahedra with the emergence of possible short-range ferromagnetic ordering of the ferromagnetic domains/clusters that are formed due to Al substitutional disorder in a paramagnetic insulating matrix.

Halogen bonding in uranyl and neptunyl trichloroacetates with alkali metals and improved crystal chemical formulae for coordination compounds.

The structures of the single crystals of compounds K2UO2(tca)4(tcaH)2 (I), K4NpO2(tca)6(tcaH)(H2O)3 (II), Rb4UO2(tca)6(tcaH)(H2O)3 (III), and Cs3UO2(tca)5(tcaH)2·H2O (IV), where tca is the trichloroacetate ion, were established by X-ray diffraction analysis. The crystals of II-IV have a framework structure, whereas in the layered crystals of I, neighboring layers are connected to each other via halogen bonds. In this regard, the crystals of I possess perfect cleavage along the (001) plane: the crystals are easily cut into stacks of very thin layers. Halogen bonds in the structures of all title compounds were characterized using the method of molecular Voronoi-Dirichlet polyhedra. The donor-acceptor halogen bond synthon, where the same halogen atom is both the donor towards one halogen atom and the acceptor from the second halogen atom, is recognized for its usefulness in the crystal design. The description of the ligand coordination modes and crystal chemical formulae of complexes is adapted for cases when ligands have chemically non-equivalent and unobvious donor atoms (for example, oxygen and halogen atoms in halogen-substituted carboxylate anions).

Large Polyhedral Oligomeric Silsesquioxane Cages: The Isolation of Functionalized POSS with an Unprecedented Si18 O27 Core.

The synthesis of organo-functionalized polyhedral oligomeric silsesquioxanes (POSS, (R-SiO1.5 )n , Tn ) is an area of significant activity. To date, T14 is the largest such cage synthesized and isolated as a single isomer. Herein, we report an unprecedented, single-isomer styryl-functionalized T18 POSS. Unambiguously identified among nine possible isomers by multinuclear solution NMR (1 H, 13 C, and 29 Si), MALDI-MS, FTIR, and computational studies, this is the largest single-isomer functionalized Tn compound isolated to date. A ring-strain model was developed to correlate the 29 Si resonances with the number of 6-, 5-, and/or 4-Si-atom rings that each non-equivalent Si atom is part of. The model successfully predicts the speciation of non-equivalent Si atoms in other families of Tn compounds, demonstrating its general applicability for assigning 29 Si resonances to Si atoms in cage silsesquioxanes and providing a useful tool for predicting Si-atom environments.

The effect of the impurities on the magnetic, electronic and optical properties of Mn5Ge3

Earlier, we experimentally showed a significant effect of oxygen on the magnetic and structural properties of Mn5Ge3 due to the formation of a Nowotny phase of Mn5Ge3Ox. Here, in continuation of this study, we present a theoretical study of the magnetic and electronic properties of Mn5Ge3 and Mn5Ge3Dx (D = B, C, O). It was found that hexagonal Mn5Ge3 is a ferromagnetic metal with two nonequivalent manganese atoms in the structure. Our ab initio calculations also predict the existence of a spin-crossover in Mn5Ge3 under pressure. Impurities reduce saturation magnetization and electrical and thermal conductivity; however, the magnetic susceptibility and Curie temperature increase. Microscopic mechanisms of the effect of the impurities on the magnetic and electronic properties Mn5Ge3 are discussed.

Computational Protocols for the 19F NMR Chemical Shifts. Part 1: Methodological Aspects

The DFT calculation of 19F NMR chemical shifts was performed for two benchmark compounds, perfluoroquinoline and perfluoroisoquinoline, each involving seven non-equivalent fluorine atoms, with using a variety of functionals and basis sets. Performed calculations provided a markedly good correlation of calculated fluorine chemical shifts with experiment. Best result was achieved for the BHandHLYP functional in combination with the quadruple zeta Jensen’s segmented basis set pcSseg-3 characterized by a mean absolute error of 2.5 ppm in the range of about 120 ppm, corresponding to a 2% error in the percentage terms. Proposed computational protocol BHandHLYP/pcSseg-3 showed a remarkably good performance on a benchmark series of eight fluorinated condensed heteroaromatic compounds.

Uniaxial negative thermal expansion and band renormalization in monolayer Td−MoTe2 at low temperature

The temperature-induced structure variation and its effect on physical properties is pivotal in material preparation for devices application. Motivated by surface scanning tunnel microscope (STM) measurement of ${T}_{d}\ensuremath{-}{\mathrm{MoTe}}_{2}$ single crystal at low temperature, temperature dependent electronic structure, lattice dynamics, and topological properties are explored to understand the microscopic origin of the observed anisotropic negative thermal expansion and abnormal STM images below 70 K. Remarkably, we find that the nonequivalent Te atoms in ${T}_{d}\ensuremath{-}{\mathrm{MoTe}}_{2}$ have qualitatively different contributions to both phonon spectra and electronic structures. The in-plane longitudinal acoustic mode and the ${\mathrm{Te}}_{(2)}$ atoms are found to play an important role in uniaxial negative thermal expansion and the temperature dependent electronic phase transition, respectively. Interestingly, under the scalar relativistic approximation, a band renormalization occurs, accompanied by a Dirac phase transition from type II to type I, upon cooling below 70 K. Introducing spin-orbit coupling induces a temperature dependent semimetal--semiconductor transition. Our results explain the experimental phenomena very well: abnormal surface STM image below 70 K does not originate from the displacement of the Te atoms but the band renormalization owing to strong electron-lattice coupling.

Coordination Polymeric Ensemble of Silver with Nitrate and 4-(Aminomethyl)benzoate: Synthesis, Crystal Structure, and Luminescence Properties

Prismatic crystals of Ag3(4-Amba)2(NO3)2 (I) and Ag(4-AmbaH)NO3 (II) are isolated from the reaction mixture of aqueous solutions of 4-aminomethylbenzoic acid (4-AmbaH) and AgNO3 at Т ≈ 70°C. The crystal structure of compound I (СIF file CCDC no. 1851513) and the luminescence properties of compounds I and II are studied. The structure of compound I contains two crystallographically nonequivalent silver atoms Ag(1) and Ag(2) with the octahedral coordination mode (with allowance for Ag···Ag contacts) with different compositions of the internal spheres of the central atoms. Owing to the contacts, the silver atoms are joined into infinite cluster ribbons (Ag···Ag 3.06−3.27 A). The carboxylate group of the 4-Amba anion exhibits the bridging properties and binds the silver atoms of both types. The Ag(2) atoms also contact with the oxygen atom of the $${\text{NO}}_{{\text{3}}}^{-}$$ ion and coordinate the NH2 group of 4-Amba. The photoluminescence spectra of compounds I and II are of the same type and show the presence of two groups of emission bands with centers at 484 and 543 nm shifted to the red range of the spectrum relative to the band of 4-AmbaH.

On the Calculation of an X-Ray Natural Circular Dichroism Signal

The sequential derivation of an expression that describes an X-ray natural circular dichroism (XNCD) signal in the most general case is performed. The obtained expression is used as a basis to consider XNCD signals and their structural origins in copper metaborate CuB2O4 crystals at an incident radiation energy near the K absorption edge of copper and lanthanum–gallium silicate La3Ga5SiO14 crystals at an incident radiation energy near the K absorption edge of gallium. It has been demonstrated that the measurements of circularly polarized X-ray absorption spectra in combination with corresponding first-principle calculations provide an efficient method for studying the contributions of crystallographically non-equivalent atoms to the X-ray optical activity of crystals.

Single-layer 1T′-MoS2 under electron irradiation from ab initio molecular dynamics

Irradiation with high-energy particles has recently emerged as an effective tool for tailoring the properties of two-dimensional transition metal dichalcogenides. In order to carry out an atomically-precise manipulation of the lattice, a detailed understanding of the beam-induced events occurring at the atomic scale is necessary. Here, we investigate the response of -MoS2 to the electron irradiation by ab initio molecular dynamics means. Our simulations suggest that an electron beam with energy smaller than 75 keV does not result in any knock-on damage. The displacement threshold energies are different for the two nonequivalent sulfur atoms in -MoS2 and strongly depend on whether the top or bottom chalcogen layer is considered. As a result, a careful tuning of the beam energy can promote the formation of ordered defects in the sample. We further discuss the effect of the electron irradiation in the neighborhood of a defective site, the mobility of the sulfur vacancies created and their tendency to aggregate. Overall, our work provides useful guidelines for the imaging and the defect engineering of -MoS2 using electron microscopy.

Solid state NMR and XPS of ternary fluorido-zirconates of various coordination modes

Extended information is provided about 19F MAS NMR and XPS spectroscopic data on 11 ternary fluorido-zirconates (Li2ZrF6, Rb2ZrF6, Cs2ZrF6, Na3ZrF7, (NH4)3ZrF7, K3ZrF7, Li4ZrF8, K2ZrF6, Na5Zr2F13, Na7Zr6F31, and (NH4)2ZrF6), which display different coordination numbers of the zirconium atom as well as different modes of fluorine atom bonding. XPS data show that binding energies on fluorine 1s electrons are sensitive to its coordination properties (ionic, terminal or bridging coordination mode) while the binding energies of zirconium orbitals are not sensitive to its coordination properties (six-, seven- or eightfold coordination). 19F chemical shifts correlate with the ionic radii of counter cations along the series Li2ZrF6, Rb2ZrF6, Cs2ZrF6 and K3ZrF7, (NH4)3ZrF7 and Na3ZrF7. This reflects the polarizability properties and shielding potential of the cations surrounding the fluorine atoms. Additionally, calculations of NMR parameters for the compounds were also carried out using the CASTEP DFT code. The correlation between the experimental isotropic chemical shifts and calculated isotropic chemical shieldings established for the studied compounds allows us to predict the 19F NMR spectrum of crystalline compounds with good accuracy. A unique technique of low temperature 19F MAS NMR experiments combined with CASTEP calculation on (NH4)2ZrF6 enabled the assignment of all 12 crystallographically non-equivalent fluorine atoms to NMR signals.

Nonadiabatic exchange-correlation kernel for strongly correlated materials

We formulate a rigorous method for calculating a nonadiabatic (frequency-dependent) exchange-correlation (XC) kernel appropriate for accurate description of both equilibrium and nonequilibrium properties of strongly correlated systems within the time-dependent density functional theory (TDDFT) via the charge susceptibility, which is in turn obtained from dynamical mean field theory (DMFT) based on the effective multi-orbital Hubbard model. Application to the simple case of the one-orbital Hubbard model already shows the importance of the nonadiabatic kernel as it leads to significant modification of the excitation spectrum—shifting the (adiabatic) peak and disclosing another that is reminiscent of the solution from DMFT. The impact of dynamical effects, naturally included through the nonadiabaticity of the XC kernel, becomes even more transparent in our consideration of the nonequilibrium charge-density response of a multi-orbital perovskite, YTiO3, to a perturbation by a femtosecond (fs) laser pulse. These initial results indicate that electron–electron correlations and nonadiabatic features may significantly affect the spectrum and nonequilibrium properties of strongly correlated systems. We also propose an algorithm for extension of the approach to non-linear response. The transparency and computational efficiency of this non-adiabatic TDDFT+DMFT approach opens the door to examination of the spectra and response of multi-orbital systems with many nonequivalent atoms—bulk material, films and nanostructures.

1-D calcium, 2-D zinc and 3-D manganese coordination polymers derived from pyrazine-2,3,5,6-tetracarboxylic acid

Three coordination polymers were synthesized from pyrazine-2,3,5,6-tetracarboxylic acid (H4pztc) in combination with calcium, zinc and manganese ions under hydrothermal conditions and their structures were determined by single crystal X-ray diffraction, powdered X-ray diffraction, Fourier transformed infrared spectroscopy, thermogravimetric and elemental analyses. Structure 1, {(Ca(H2pztc)(H2O)3)n, crystallizes as 1-D chains, with the partially deprotonated ligand in –O,N,O– coordination mode and with the Ca atoms in an uncommon nine coordinate environment. Structure 2, {Zn1(pztc)(H2O)2Zn2(H2O)4}n, is an infinite, 2-D coordination network that contains two nonequivalent Zn atoms, each with octahedral geometry, and the fully deprotonated pztc4− in bis-bridging chelating coordination mode. The stacked 2-D layers are stabilized by extensive inter-layer water-carboxylate hydrogen-bonding with an inter-layer distance of 4.9Å. Structure 3, {(Mn2(pztc)(H2O)2)}n, is a covalently bonded 3-D network containing two nonequivalent Mn atoms, each with octahedral geometry, and the fully deprotonated pztc4− units. Structure 3 exhibits paramagnetic behavior at room temperature, and weak antiferromagnetic properties at very low temperature, which is consistent with their nearest Mn…Mn separation distance of 4.9Å.

14N NMR Spectroscopy Study of Binding Interaction between Sodium Azide and Hydrated Fullerene

Our study is the first attempt to study the interaction between NaN3 and hydrated fullerenes C60 by means of a non-chemical reaction-based approach. The aim is to study deviations of signals obtained by 14N NMR spectroscopy to detect the binding interaction between sodium azide and hydrated fullerene. We considered 14N NMR spectroscopy as one of the most suitable methods for the characterization of azides to show resonance signals corresponding to the three non-equivalent nitrogen atoms. The results demonstrate that there are changes in the chemical shift positions and line-broadening, which are related to the different molar ratios of NaN3:C60 in the samples.