C2ν Symmetry Research Articles

Joint quantum sensing of vector magnetic field and temperature with nitrogen-vacancy centers in diamond

Quantum diamond sensors of multiple physical quantities, especially magnetic field and temperature, have great application prospects in materials science, biophysics, and engineering. Here, we demonstrate joint quantum sensing of vector magnetic field and temperature based on ensembles of nitrogen-vacancy (NV) centers in the diamond. Combining the intrinsic C3ν symmetry of diamond crystals and multiple-frequency excitation technique, we can directly measure frequency-modulated optically detected magnetic resonance (ODMR) spectra for three different NV orientations and then obtain the Zeeman splittings and the center frequency movement of the electron spin. An artificially generated underlying external magnetic field is used to eliminate degeneracy and facilitate coordinate transformations. The six-channel phase-locked amplification technology enables simultaneous detection of vector magnetic field and temperature with a sensitivity of about 0.87 nT/Hz1/2 and 0.32 mK/Hz1/2; meanwhile, a 23 dB isolation between magnetic and temperature signals is kept. This technology realizes the simultaneous measurement of arbitrary vector magnetic field and temperature, which can be used to study the temperature-varying magnetic phase transition.

Passive nonreciprocal transmission and optical bistability based on polarization-independent bound states in the continuum

Abstract Free-space nonreciprocal transmission is a crucial aspect of modern optics devices. The implementation of nonreciprocal optical devices through optical nonlinearity has been demonstrated. However, due to the weak nonlinearity of traditional materials, most self-biased nonreciprocal devices are heavily dependent on the high Q strong resonances. In general, these resonances are frequently polarization sensitive. In this work, we propose ultrathin optical metasurface embedding Kerr nonlinearities to achieve nonreciprocal transmission and optical bistability for free-space propagation based on symmetry-protected bound states in the continuum (BICs). Since the structure of the metasurface retains C4ν symmetry, the symmetry-protected BIC is polarization-independent. It is also shown that the nonreciprocal intensity range could be largely tuned by the structure parameters. The demonstrated devices merge the field of nonreciprocity with ultrathin metasurface technologies making this design an exciting prospect for an optical switch, routing, and isolator with optimal performance.

THE SYNTHESIS AND PROPERTIES OF A SODIUM SUPRAMOLECULAR CRYSTAL NETWORK CONSTRUCTED WITH FUNCTIONAL PYRAZINE SULFONIC ACID

Sulfonic acid groups with C3ν symmetry can coordinate with metal ions to produce multidimensional structures due to their flexible coordination modes. They can also penetrate into supramolecular structures through an intriguing bridging pattern and weak interactions. Herein, a novel heterocyclic sodium sulfonate supramolecular structure, namely [Na(Pyr-SO3)(H2O)]n where Pyr-SO3H is pyrazine sulfonic acid, is synthesized by utilizing NaBF4 to coordinate with the P–SO3H ligand through the solvent evaporation method. The single crystal X-ray diffraction (XRD) data indicate that the as-formed structure belongs to the Pbca space group. Additional properties are characterized by powder XRD, thermal analysis, and solid-state fluorescence. In particular, the introduction of a soft alkali metal ion can coordinate with the oxygen atom of the sulfonate ligand and form a Na–O bridging configuration that can not only significantly improve the pyrazine sulfonic acid ligand coordination ability, but also provide a reference for the extended study of functional sulfonate polymers in the future.Electronic supplementary materialSupplementary material is available for this article at 10.1134/S0022476621110172 and is accessible for authorized users.

Excited States Calculation of Some Alkyl Sulfides with Time-Dependent Density Functional Theory

The excited states of mustard and related alkyl sulfides have been calculated using time-dependent density functional theory. Among the seven commonly used density functionals, PBE0 exhibits the most accurate excited energy, while the Pearson-related coefficient of calculated energies and experimental peaks reaches 0.98. Boltzmann average analysis reveals that excited energies of different conformers are almost the same. The calculated excited states of mustard come to 5.56 and 6.00 eV, which are assigned as n → σ* transition by the natural transition orbital visualization. Besides, sulfur ethers with C2ν symmetry show similar ultraviolet properties as mustard, whereas the excited states of simulated agents with the SCH2CH2Cl group differ from mustard.

The structure elucidation of new ionic liquid and its application for the synthesis of a series of novel triazolo[1,5-a]pyrimidine scaffolds

In the present study, the chemical structure of 4,4ʹ-trimethylene-N,Nʹ-dipiperidinium chlorosulfonate is elucidated by 1D NMR, and 2D NMR, FTIR, Raman analyses, and Mass spectra. It was indicated that the chlorosulfonic acid could not act as a sulfonating agent in the reaction with secondary amines like TMDP due to due more steric hindrance of the sulfur atom by chlorine and oxygen atoms. Raman and FTIR spectra are demonstrated as two high-value optical techniques to the elucidation and identification of chemical structures that confirmed C3ν symmetry for chlorosulfonate anion in the ionic liquid. Then, the solvent-catalyst activity of ionic liquid was demonstrated in the one-pot synthesis of a series of novel triazolo-pyrimidines under mild conditions. The ionic liquid was retrieved and reused several times without reducing its catalytic efficiency.

Structural analysis of a calix[4]arene-based Platonic Micelle

We have recently introduced the concept of “Platonic micelles”, the preference of spherical micelles to specific aggregation numbers mostly coinciding with the number of faces of platonic solids. This effect was observed on bulky, mostly calix[4]arene-based surfactant systems with small aggregation numbers. The preferred aggregation numbers result in better sphere coverage, highliting the packing and the “protection” of hydrophobic cores from the aqueous solvent as the most important factor for this preference. In the present study we further explore the interactions that drive the packing of the highly charged PACaL3 surfactant into highly symmetrical hexameric micelles. We performed a series of molecular dynamics simulations that yielded a large set of structures and an ensemble in good agreement with the experimental Small Angle X-ray Scattering data was selected. The geometry and the rigidity of the calix[4]arene group with proper tail length and headgroup volume are the driving forces for the high symmetry and monodispersity of the micelle. The charge of the headgroups is mainly responsible for inhibiting the formation of higher order structures. Sodium, shown to be important for the stability of the micelle, is not directly interacting with the micelle implying that the calix[4]arene ring is a C2ν symmetry conformation.

Investigating the evolution of local structure around Er and Yb in ZnO:Er and ZnO:Er, Yb on annealing using X-ray absorption spectroscopy

The local structure around Er and Yb centre in ZnO favouring upconversion luminescence was studied using EXAFS (Extended X-ray absorption fine structure spectroscopy). Due to the ionic radii difference between Zn and Er, Yb ions, the dopants cannot replace Zn in the ZnO lattice properly. Er2O3 and Yb2O3 impurity phases are formed at the grain boundaries of ZnO. It is found that the local structure around the Er centre in ZnO is modified on annealing in air. The symmetry around both erbium and ytterbium reduces with increase in annealing temperature. Symmetry reduction will favour the intra-4f transition and the energy transitions causing upconversion luminescence. By fitting the EXAFS data with theoretically simulated data, it is found that the Er centre forms a local structure similar to C4ν symmetry which is a distorted octahedron. On annealing the sample to 1200 °C, all the erbium centres are transformed to C4ν symmetry causing enhanced upconversion emission. Yb centre has also been modified on annealing. The decrease in co-ordination number with annealing temperature will decrease the symmetry and increase the near infrared absorption cross section. The decrease in symmetry around both the erbium and ytterbium centre and formation of C4ν symmetry around Er centre is the reason behind the activation of upconversion luminescence with high temperature annealing in both Er doped and Er, Yb co-doped ZnO samples. The study will be useful for the synthesis of high efficiency upconversion materials.

Facet-Dependent Cr(VI) Adsorption of Hematite Nanocrystals.

In this study, the adsorption process of Cr(VI) on the hematite facets was systematically investigated with synchrotron-based Cr K-edge extended X-ray absorption fine structure (EXAFS) spectroscopy, in situ attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy, density-functional theory calculation, and surface complexation models. Structural model fitting of EXAFS spectroscopy suggested that the interatomic distances of Cr-Fe were, respectively, 3.61 Å for the chromate coordinated hematite nanoplates with exposed {001} facets, 3.60 and 3.30 Å for the chromate coordinated hematite nanorods with exposed {001} and {110} facets, which were characteristic of inner-sphere complexation. In situ ATR-FTIR spectroscopy analysis confirmed the presence of two inner-sphere surface complexes with C3ν and C2ν symmetry, while the C3ν and C2ν species were assigned to monodentate and bidentate inner-sphere surface complexes with average Cr-Fe interatomic distances of 3.60 and 3.30 Å, respectively. On the basis of these experimental and theoretical results, we concluded that HCrO4(-) as dominated Cr(VI) species was adsorbed on {001} and {110} facets in inner-sphere monodentate mononuclear and bidentate binuclear configurations, respectively. Moreover, the Cr(VI) adsorption performance of hematite facets was strongly dependent on the chromate complexes formed on the hematite facets.

Solvatochromism of 9,10-phenanthrenequinone: an electronic and resonance Raman spectroscopic study.

Solvent effects play a vital role in various chemical, physical, and biological processes. To gain a fundamental understanding of the solute-solvent interactions and their implications on the energy level re-ordering and structure, UV-VIS absorption, resonance Raman spectroscopic, and density functional theory calculation studies on 9,10-phenanthrenequinone (PQ) in different solvents of diverse solvent polarity has been carried out. The solvatochromic analysis of the absorption spectra of PQ in protic dipolar solvents suggests that the longest (1n-π(1)*; S1 state) and the shorter (1π-π(1)*; S2 state) wavelength band undergoes a hypsochromic and bathochromic shift due to intermolecular hydrogen bond weakening and strengthening, respectively. It also indicates that hydrogen bonding plays a major role in the differential solvation of the S2 state relative to the ground state. Raman excitation profiles of PQ (400-1800 cm(-1)) in various solvents followed their corresponding absorption spectra therefore the enhancements on resonant excitation are from single-state rather than mixed states. The hyperchromism of the longer wavelength band is attributed to intensity borrowing from the nearby allowed electronic transition through vibronic coupling. Computational calculation with C2ν symmetry constraint on the S2 state resulted in an imaginary frequency along the low-frequency out-of-plane torsional modes involving the C=O site and therefore, we hypothesize that this mode could be involved in the vibronic coupling.

Synthesis of a Tri(gold)boride Complex (Cy3P)B[AuP(o-Tol)3]3

A tri(gold)boride of the formula B[AuP(o-Tol)3]3 (2) is generated in the reaction of the silylated phosphine borane Cy3PBH2SiMe3 with the tri(gold)oxonium tetrafluoroborate [(o-Tol)3PAu]3O+ BF4 - and isolated as its stable 1 : 1 complex with tricyclohexylphosphine: Cy3PB[AuP(o-Tol)3]3. The composition of the product has been confirmed by elemental analyses and mass spectrometry. Solution NMR data of 2 indicate a molecular structure with C3ν symmetry which has been confirmed by MP2 calculations for the model system H3PB(AuPH3)3. The compound is a rare case of a trimetallated boride which is isolobal with the simple phosphineborane Cy3PBH3. With reagents bearing less bulky substituents (R3 = iPr3, MePh2, Ph3), the reactions proceed to salts with the tetra-aurated cations [Cy3PB(AuPR3)4]+

A Hexanuclear Cobalt(II) Cluster Incorporated in a Banana‐Shaped Tungstovanadate: [(Co(OH2)Co2VW9O34)2(VW6O26)]17–

AbstractThe hexanuclear cobalt‐containing tungstovanadate complex, Na17[(Co(OH2)Co2VW9O34)2(VW6O26)]·31H2O (1) has been synthesized through reaction of cobalt nitrate, sodium tungstate, and V2O5 in acetate buffer solution. The title compound has been characterized by X‐ray crystallography, elemental analysis, FTIR, UV/Vis, and 51V NMR spectroscopy and by cyclic voltammetry. Complex 1 crystallizes in the monoclinic space group P21/c (a = 15.706(3) Å, b = 21.973(5) Å, c = 35.080(8) Å, α = 90°, β = 97.420(3)°, γ = 90°; V = 12005(5) Å3; Z = 4; based on 192337 independent reflections), which consists of two tri‐CoII substituted B‐α‐[(Co(OH2)Co2VW9O39)] Keggin units bridged by one unique [VW6O16] fragment leading to a banana‐shaped structure with idealized C2ν symmetry. Stability studies show that polyoxoanion 1 ultimately transforms into the tetracobalt‐containing sandwich‐type polyoxoanion, 2, as confirmed by 51V NMR and X‐ray crystallographic analyses. Polyoxoanion 1 shows catalytic activity for the H2O2‐based epoxidation of 1‐hexene and cyclohexene in 1,2‐dichloroethane solvent.

Theoretical study of the structure and analytic potential energy function for the ground state of the PO2 molecule

In this paper, the energy, equilibrium geometry, and harmonic frequency of the ground electronic state of PO2 are computed using the B3LYP, B3P86, CCSD(T), and QCISD(T) methods in conjunction with the 6–311++G(3df, 3pd) and cc-pVTZ basis sets. A comparison between the computational results and the experimental values indicates that the B3P86/6-311++G(3df, 3pd) method can give better energy calculation results for the PO2 molecule. It is shown that the ground state of the PO2 molecule has C2ν symmetry and its ground electronic state is X2A1. The equilibrium parameters of the structure are RP−O = 0.1465 nm, ∠OPO = 134.96°, and the dissociation energy is Ed = 19.218 eV. The bent vibrational frequency ν1 = 386 cm−1, symmetric stretching frequency ν2 = 1095 cm−1, and asymmetric stretching frequency ν3 = 1333 cm−1 are obtained. On the basis of atomic and molecular reaction statics, a reasonable dissociation limit for the ground state of the PO2 molecule is determined. Then the analytic potential energy function of the PO2 molecule is derived using many-body expansion theory. The potential curves correctly reproduce the configurations and the dissociation energy for the PO2 molecule.

ChemInform Abstract: Internal Rotation and Structure of Isobutylene.

Abstract The high-resolution rotational spectrum of isobutylene was measured for transitions with J ≤ 7, using a modified Balle-Flygare Fourier transform microwave spectrometer with a pulsed supersonic nozzle as the sample source. Previously improved by the addition of a computer-based IBM PC-AT controller and averager [C. Chuang et al., Rev. Sci. Instrum. 61, 1629–1635 (1990)], the spectrometer has been fitted with software which provides Autosearch operation. Analysis of the fine structure of the observed transitions, caused by internal rotation of the two methyl groups, gives the V3 barrier to be 2176(3) cal/mole and the angle θ between the methyl top and b-axes to be 58.5(3)°, with the latter perhaps decreasing slightly at higher J. Rotational constants reported previously for six isotopic species of isobutylene and those now obtained for (CH3)2 13CCH2 at natural abundance were fitted to obtain an effective (r0) structure. The results indicate that the methyl groups are distorted slightly from C3ν symmetry. This tilts the CH3 axis 0.8(2)° away from coaxiality with the CC bond axis toward the double bond.

On the nature of Ti(IV)‐pillared layered metal hydroxides prepared from green, water‐soluble Ti‐peroxide

AbstractTi‐peroxide pillared layered double hydroxides (LDHs) have been prepared for the first time using water‐soluble Ti‐peroxide as an intercalating precursor. It is novel and alluring that the whole preparation procedure does not involve any usage of organic or chlorine‐containing hazards. Intercalated into the LDH interlayer region, Ti‐peroxide is prevented partially from condensation in the solvent evaporation. The interlayer TiO2 unit exists in triangular (η2) structure with C2ν symmetry in most cases, giving an interlayer gallery of 0.50–0.60 nm. But in the case of pH 4.0, monodentate (η1) structure is also observed, giving an interlayer gallery of 0.70 nm. All the Ti‐peroxide pillared LDHs prepared in this work show catalytic activity in the selective oxidation of thioether. The Ti‐peroxide introduced into the interlayer regions of Mg/Al LDH with a particle size of around 50–120 nm exhibits better recyclability than Ti‐peroxide gel, either in bulk or adsorbed on the exterior surface of LDH particles. © 2009 American Institute of Chemical Engineers AIChE J, 2010

C4ν Symmetry Crystal Field and Ground State Wavefunction of the VO2+ Ion

The spin-Hamiltonian parameters obtained from EPR studies of the VO2+ ion in different diamagnetic host lattices are used to estimate the ground state wave functions. These are of dxy type with admixture of the excited states dx2−y2, dyz and dxz. The hyperfine interaction parameter and Fermi contact term for the VO2+ doped crystals are determined using the coefficients of the ground state. The various parameters are correlated to the ligand properties of the complexes.

Kinetic Isotope Effects on the Photolysis of C60H18 and C60D18

Fullerane C60H18 and its deuterated analogous C60D18 were synthesized in n‐hexane solution by a reduction reaction of C60 under the action of HCl or DCl on Zn dust. The resulting solutions were subjected to UV irradiation at 245 nm from a low pressure mercury lamp under He. It was found that at 212 nm the photolysis rate constant of C60H18 molecule Hk212 = 8.68 × 10−4 s−1 was significantly higher than that of its deuterated analogous C60D18: Dk212 = 5.93 × 10−4 s−1. Similarly, at 256 nm it was confirmed the result that C60D18 was photolyzed more slowly than C60H18. Also in this case, Hk256 = 6.83 × 10−4 s−1 is significantly higher than that of its deuterated analogous C60D18: Dk212 = 3.74 × 10−4 s−1. Kinetic isotope effect involving the C‐H and C‐D bond activation has been advocated to explain the differences in photodecomposition speed of C60H18 in comparison to C60D18. On the basis of solubility in alkanes and unique electronic absorption spectrum C60H18 with C3ν symmetry prepared under high hydrogen pressure can be easily distinguished from the C60H18 and its deuterated analogous C60D18 synthesized in n‐hexane from Zn/HCl or Zn/DCl. The C3ν ‐ C60H18 displayed also a different evolution of the electronic absorption spectrum under photolysis in comparison to C60H18 and its deuterated analogous C60D18. The pseudofirst rate constant of C3ν ‐C60H18 is k217 = 4.04 × 10−4 s−1 and k255 = 2.25 × 10−4 s−1.

Synthesis and Characterization of 9-Hydroxyphenalenone Using 2D NMR Techniques

9-Hydroxyphenalenone is a planar multicyclic β-keto–enol, which is synthesized via a Friedel–Crafts acylation followed by acid-catalyzed intramolecular Michael addition with the loss of a phenyl group in a one-pot reaction during a four-hour lab period. Tautomerization of the andbeta-keto–enol results in C2ν symmetry on the NMR time scale, which simplifies the spectra and provides a unique structure for teaching 2D NMR spectroscopy. The 1H and 13C assignments can be made using 1D and 2D NMR techniques and data collection can be reduced to less than twenty minutes with optimized parameters.

Cs4Ge9·en: A Novel Compound with [Ge9]4− Clusters – Synthesis, Crystal Structure and Vibrational Spectra

AbstractRed‐orange prismatic crystals of Cs4Ge9·en (en = ethylenediamine) were obtained via metathesis reaction of an en solution of K4Ge9 with a large excess of CsI. The compound is very sensitive to air and moisture. Cs4Ge9·en is not isotypic to Rb4Ge9·en and crystallizes in a new structure type (monoclinic, space group P21/c (No. 14); a = 16.757(3), b = 16.462(3), c = 15.657(2) Å, β = 90.37(1)°; Z = 8; Pearson code mP200). The crystal structure comprises two types (A and B) of discrete [Ge9]4− units arranged in the motif of a distorted hexagonal close‐packing (h.c.p.). In this h.c.p. framework, each tetrahedral hole is filled by one Cs atom and each larger octahedral hole is filled by a group of one en and two Cs atoms. The topology of the two crystallographically distinct [Ge9]4− clusters corresponds to distorted, monocapped tetragonal antiprisms with bond lengths varying in the range 2.551–2.848Å (type A cluster) or in the range 2.538–2.975Å (less regular type B cluster). According to the DTA and TG measurements, Cs4Ge9·en decomposes at 378 K under liberation of gaseous ethylenediamine yielding Cs4Ge9. The Raman spectra of the title compound were interpreted based on the idealized C4ν symmetry of an isolated [Ge9]4− cluster. The characteristic breathing mode was localized at 222 cm−1. The results are analyzed and discussed in context with those of the previously reported compounds Cs4Ge9, K4Ge9 and Rb4Ge9·en.

Theoretical study of electric field‐induced intramolecular electron transfer in donor–acceptor pairs via the rigid space and their suitability as molecular electronic devices

AbstractThe geometries of two reaction systems have been optimized under the constraint of C2ν symmetry, using the UHF/6‐31G method. The potential energy surfaces (PES) of the two systems in different external electric field have been constructed using a linear reaction coordinate. It is concluded that the reorganization energies and electron transfer matrix elements for both systems are almost independent of the external electric field. However, the standard Gibbs energy difference changes remarkably with the change of the external electric field. Hence, the applied electric field leads to the variation of rate constant of electron transfer reaction. The threshold field, where the electron transfer becomes barrier free, is obtained to be 0.0015 a.u. for the anion system 1, and 0.00097 a.u. for the anion system 2. The threshold field for modified system 1, in which the hydrogen atoms linking to benzene rings are replaced by fluorine atom, is 0.0018 a.u. The calculations show that the best way to adjust the threshold field is to adjust the dipole moment of the reaction system by changing the length of the bridge. As the rate constant in field‐free case is taken into account, neither reaction systems could be used as molecular electronic device. But if the bridge consists of three or four HCTDs, the rate constant and threshold field will satisfy the practical demand. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2006

The Totally Symmetric Vibrations of NH3···HF and NH3···HCN: a CCSD(T) Study Including Anharmonicity Effects

Abstract The coupled cluster variant CCSD(T) has been employed to calculate potential energy and dipole moment surfaces for the hydrogen-bonded complexes NH3···HF and NH3···HCN, restricting the treatment to the totally symmetric coordinates. Both complexes have C 3ν symmetry, with equilibrium dissociation energies (D e) predicted to be 52.1 and 27.1 kJ mol−1, respectively. Vibrational term energies and wavefunctions as well as absolute IR intensities are calculated under inclusion of anharmonicity effects. In contrast to previous theoretical work for NH3···HF, the umbrella bending vibration of this complex as well as for NH3···HCN is found to be rather anharmonic. The familiar double harmonic approximation fails to yield reliable values for the IR intensities of the NH3 (ND3) symmetric stretching vibrations of either NH3···HF or ND3···DF. The wavenumbers of the intermolecular stretching vibrations are predicted as ν4 = 277 cm−1 (NH3···HF) and ν5 = 154 cm−1 (NH3···HCN). Owing to a large quadratic coupling term in the electric dipole moment function, the band ν4(NH3···HF) has virtually zero intensity. The effects of deuterium substitution on wavenumbers and IR intensities have been studied for both complexes.