Single-crystal Spectra Research Articles

Studying of the structure diverse and photocatalytic activities of two 1,4-bis(imidazole-1-methyl)-benzene-based coordination polymers

Two new coordination polymers, namely, [Zn(Bix)Cl2]n(1) and [Cu(Bix)0.5(o-phen)Cl2]n(2) (Bix = 1,4-bis(imidazole-1-methyl)-benzene and/; o-phen = o-phenanthroline), have been prepared by the hydrothermal method and characterized by the X-ray single crystal diffraction, element analysis, FTIR spectra and UV–vis spectra. Owing to the coordination of Cl ion in the mineralizer-NaCl, coordination polymer 1 only links into the 1D chain by the main ligand-Bix. However, coordination polymer 2 shows the binuclear oligomer not only the coordination of Cl ion but also the coordination of the auxiliary ligand-o-phen. UV–vis aborption spectra experiments of 1 and 2 demonstrate that 1 and 2 are the potential ultraviolet photo-catalytic materials. In order to research the photo-catalytic activities of 1 and 2, we choose the methylene blue(MB) as the object pollutants, 1 and 2 attained highly catalytic efficiency.

Thiazolo[5,4-b]pyridine Alkaloid and Seven ar-Bisabol Sesquiterpenes Produced by the Endophytic Fungus Penicillium janthinellum.

We investigated the secondary metabolites present in Penicillium janthinellum MPT-25, an endophytic fungus isolated from Taxus wallichiana var. chinensis (Pilger) Florin. Chemical characterization of the solid cultured extract resulted in the isolation of 11 compounds, including eight previously undescribed metabolites: a thiazolo[5,4-b]pyridine alkaloid, janthinedine A (1), and seven ar-bisabol sesquiterpenes, janthinepenes A–G (2–8). Their structures were elucidated by a combination of extensive spectroscopic methods, including single-crystal X-ray diffraction and ECD spectra. The antimicrobial activities of these compounds were evaluated against seven agricultural pathogenic fungi and eight clinically drug-resistant bacteria.

Growth, physico-chemical properties, opto-electrical characteristics, thermo-mechanical and DFT studies of 4-aminoantipyrine single crystals

The aim of this work was to grow organic single crystals of 4-Aminoantipyrine (4-AAP) under ambient conditions, using a solvent slow evaporation method, and then to investigate the crystal structure, optical band gap, optical transmittance behavior, second harmonic generation efficiency, thermal stability, material rigidity, and dielectric responses for opto-electrical based device applications. The powder X-ray diffraction (XRD) and single crystal XRD analyzes revealed the hexagonal crystal structure and lattice parameter values of the as-grown 4-AAP. The respective molecular vibration bands and functional groups of the as-grown 4-AAP were identified using the experimental and theoretical FT-IR analysis. The optical absorption and transmittance spectrum of the 4-AAP single crystals revealed good transparency throughout the visible region. The non-linear optical (NLO) characteristics of the 4-AAP crystals were tested using the Kurtz and Perry powder technique. Thermal gravimetric (TGA) and differential thermal analysis (DTA) were used on the as-grown crystals, to determine their weight loss and heat absorption/release process. The hardness vs load plot can be used to determine the hardness values and response of the hard as-grown 4AAP crystals under the influence of load. The electrical conductivity and dielectric behavior of the 4-AAP crystals changed as the applied frequency increased. Computational techniques were used to investigate the 4-AAP's optimized geometrical structure, theoretical optical band, molecular electrostatic potential, and Mulliken atomic charge population.

Oxygen out, sulfur in: The alkali metal sulfidotungstates K2[WS4] and novel Na2[WS4] ⋅ 4 H2O

AbstractAn attempt to synthesize a holmium sulfidotungstate using potassium polysulfides as reactive flux resulted in orange single crystals of K2[WS4], isotypic to K2[MoS4] (orthorhombic; Pnma; a=935.10(3), b=694.22(2), c=1221.85(4) pm; Z=4). A similar attempt to obtain a neodymium sulfidotungstate with sodium polysulfide yielded a violet substance, which underwent hydrolysis yielding orange‐yellow single crystals of Na2[WS4] ⋅ 4 H2O (monoclinic, C2/c, a=1098.08(4), b=904.46(3), c=1144.27(4) pm, β=101.577(3)°, Z=4). Further attempts to synthesize these products deliberately as single phase materials only proved to be successful for K2[WS4] but not for Na2[WS4] ⋅ 4 H2O. Both compounds contain non‐condensed [WS4]2− tetrahedra, which surround the alkali metal cations with coordination numbers of nine and eight in K2[WS4]. In Na2[WS4] ⋅ 4 H2O, the sodium cations are coordinated by two sulfide anions plus four water molecules, resulting in a coordination number of six. Besides crystal structure determination, infrared and single crystal Raman spectra were collected and the optical band gap of K2[WS4] was determined.

Elucidating the Infrared Spectral Properties of Succinic Molecular Acid Crystals: Illustration of the Structure and the Hydrogen Bond Energies of the Crystal and Its Deuterated Analogs.

Herein, the infrared spectroscopic properties of molecular succinic acid crystals (SA) and their four isotopic analogs [C2H4(COOH)2, h6-SA; C2H4(COOD)2, d2-SA; C2D4(COOH)2, d4-SA; C2D4(COOD)2, d6-SA] are reported. The correlation between the structure of succinic acid molecules and their corresponding hydrogen bond energies is elucidated. The effects related to the isotopic dilution as well as the changes in the spectrum recording temperature on the fine structures of the vO-H and vO-D bands are interpreted. The infrared spectral anomalies detected in the spectra of isotopically neat succinic nanocrystal acids are confirmed by theoretical calculations using density functional theory (DFT). According to previous spectroscopic studies of succinic acid and those carried out for α,ω-dicarboxylic acids, a decent agreement between the experimental results and the theoretical DFT simulations is obtained. Moreover, the spectra of single crystals of the h6 and d4 succinic acid variants prove that the vibrational coupling mechanism between the (COOH)2 cycles is rigorously convergent to that detected in the spectra of aromatic carboxylic acids, suggesting thereby that the promotion of symmetry-forbidden high stretching IR transitions plays a crucial role. Furthermore, the obtained experimental results reveal that the succinic acid shows a spectral behavior significantly different from that characteristic of hydrogen associations of other acids of homologous series, such as the glutaric, adipic, malonic, and pimelic acid crystals. The results obtained herein shed light on the way to explore the revealed structure of isotopic derivatives of succinic acid crystals and may prove to be useful results for understanding the nature of unconventional interactions as well as the macroscopic energy effects directing the development of hydrogen associations.

Raman activity of the longitudinal optical phonons of the LiNbO3 crystal: Experimental determination and quantum mechanical simulation

AbstractIn this study, the and the two equivalent / polarized Raman spectra of a LiNbO3 single crystal have been recorded and used as a benchmark test for the density functional theory (DFT) calculation of the longitudinal modes and of their Raman activity. The theoretical approach, based on periodic boundary conditions and a linear combination of atomic orbitals (LCAO), provides excellent predictions of phonon wavenumbers and relative bands intensities for both A1 and E Longitudinal Optical (LO) modes and complements a previous paper limited to the study of Transverse Optical (TO) modes. Overall, the present investigation demonstrates that the LCAO approach, as implemented in the CRYSTAL software, gives results of similar accuracy for the TO and the LO phonons features. By means of a band deconvolution scheme applied to the experimental spectra, we present, for the first time, a quantitative comparison between experimental and theoretically predicted polarized Raman band intensities of LiNbO3 LO modes. This analysis highlights the role of the suitable determination of the static and high‐frequency dielectric matrices that are needed for the prediction of the TO/LO frequency split but also the first nonlinear electric susceptibility tensor for an accurate description of the Raman intensity pattern.

A new polyoxometalate-based silver-organic framework as environmental-friendly catalyst for solvent-free cyanosilylation of aldehydes

A new polyoxometalate-based silver-organic framework Ag4(imbta)4(PWVWVI11O40) (1) (imbta=1-imidazol-1-ylmethyl-1H-benzotriazole) was synthesized as heterogeneous catalysts for cyanosilylation, and characterized by infrared spectroscopy, elemental analysis, single-crystal X-ray diffraction and X-ray photoemission spectra. The results of single crystal X-ray indicate that in compound 1, Ag ions, imbta ligands and PW12O403- construct a 2D layers by covalent bonds. The adjacent 2D layers are further connected together through numerous π‧‧‧π interactions and C–H‧‧‧O hydrogen bonding interactions to achieve a 3D supramolecular architecture. More importantly, compound 1 is able to act as a highly efficient heterogeneous Lewis acid-base catalyst for cyanosilylation of various aldehydes at room temperature under solvent-free condition. The conversion of anisaldehyde to the product of cyanohydrin trimethylsilyl ether reaches up to 99.9% within 4 h by catalyzing of compound 1. Also, it is observed that there is no obvious decrease of catalytic activity after three cycles. Therefore, the compound 1 has significant potential as environmental-friendly catalyst for widely practical application in cyanosilylation reactions.

Physicochemical and DFT studies of organic NLO single crystal 4-methoxy-N-(2-methyl-5-nitrophenyl) benzamide

4-methoxy-N-(2-methyl-5-nitrophenyl) benzamide (4MNMNPB) was synthesized by benzoylation method. 4MNMNPB is grown slowly evaporation technique DMSO as solvent and grown at ambient temperature. The molecular geometry of the 4MNMNPB molecule was optimized using DFT with the B3LYP/6-311++G (d, p) basis group and theoretical assessments were provided. The optical transmittance was measured within the 350–1000 nm regions and was found to be in good agreement with optical applications. The structural identification was performed by single crystal XRD, 1H-NMR and 13C-NMR spectra investigations. TGA/DTA was used to confirm the crystal's thermal stability. Kurtz-Perry powder approach has applied to determine the relative SHG efficiency.

Pressure-Dependent Structure of BaZrO3 Crystals as Determined by Raman Spectroscopy.

The structure of dielectric perovskite BaZrO3, long known to be cubic at room temperature without any structural phase transition with variation in temperature, has been recently disputed to have different ground state structures with lower symmetries involving octahedra rotation. Pressure-dependent Raman scattering measurements can identify the hierarchy of energetically-adjacent polymorphs, helping in turn to understand its ground state structure at atmospheric pressure. Here, the Raman scattering spectra of high-quality BaZrO3 single crystals grown by the optical floating zone method are investigated in a pressure range from 1 atm to 42 GPa. First, based on the analyses of the infrared and Raman spectra measured at atmospheric pressure, it was found that all the observed vibrational modes could be assigned according to the cubic structure. In addition, by applying pressure, two structural phase transitions were found at 8.4 and 19.2 GPa, one from the cubic to the rhombohedral Rc phase and the other from the rhombohedral to the tetragonal I4/mcm phase. Based on the two pressure-induced structural phase transitions, the true ground state structure of BaZrO3 at room temperature and ambient pressure was corroborated to be cubic while the rhombohedral phase was the closest second.

Resonant inelastic soft x-ray scattering on LaPt2Si2

X-ray absorption and resonant inelastic x-ray scattering spectra of LaPt2Si2 single crystal at the Si 2p and La 4d edges are presented. The data are interpreted in terms of density functional theory, showing that the Si spectra can be described in terms of Si s and d local partial density of states (LPDOS), and the La spectra are due to quasi-atomic local 4f excitations. Calculations show that Pt d-LPDOS dominates the occupied states, and a sharp localized La f state is found in the unoccupied states, in line with the observations.

Optical absorption spectra of MgO single crystals under shock compression between 50 and 132 GPa

Optical properties of transparent windows at high pressures are of essential importance in dynamic experiments. To investigate the effects of plastic deformation-induced defects on optical transparency of MgO single crystals, real-time absorption spectra are measured via impact experiments and fast multi-color pyrometry. Shock pressure ranges from 50 to 132 GPa. Optical transmission histories are measured in each experiment via an on-board light source generated by shock-wave, from which absorption coefficient α is determined as a function of the wavelength λ. The resultant real-time absorption spectrum (α vs λ) peaks around 520 nm (∼2.39 eV), which blueshifts with increasing pressure. These featured spectra are possibly attributed to defective absorption at defect-centers (color-centers) in MgO single crystals generated by shock-waves. Plasticity-induced defects are most likely responsible for the decrease in transparency. MgO single crystals are not suited to be used as an optical window for thermometric in the visible light spectrum under shock pressures above 129 GPa.

Hybrid Diterpenic Meroterpenoids from an Endophytic Penicillium sp. Induced by Chemical Epigenetic Manipulation.

Cultivation of an endophytic fungus Penicillium sp. KMU18029 with suberanilohydroxamic acid (SAHA), a histone deacetylase inhibitor, led to the isolation of two pairs of diterpenic meroterpenoids with a unique natural product framework combining features of pyripyropenes and decaturins/oxalicines, pyrandecarurins A (1) and B (2), pileotin A (3) and B (4), along with their potential precursor decaturenoid (5). Compounds 1, 2, 4, and 5 were new. The structures of 1-5 were elucidated by extensive spectroscopic analyses. The absolute configurations of 1-4 were determined by single-crystal X-ray diffraction, NOESY spectra, ECD calculations, and biogenetic considerations. The absolute configuration of compound 3 was confirmed for the first time. Compound 5 showed moderate activity against AChE with an IC50 value of 13.9 ± 1.1 μM.

Wavelength modulation optical spectra of Ag3AsS3 crystals in the energy gap

Absorption spectra of Ag3AsS3 single crystals in E||c and E⊥c polarizations were investigated at temperatures 10 and 300 K. The edge absorption temperature dependence was analyzed in temperature range 300 - 10 K in E⊥c and E||c polarizations. Transmission spectra in crossed polarizers for single crystal plates with different thicknesses were studied. Indirect energy intervals (Eg1ind. and Eg2ind.) for both polarizations were found out in wavelength modulation transmission spectra (ΔT/Δλ) measured at 10 K. In photoluminescence spectra at 11 K an emission maximum associated with indirect excitonic transitions was discovered. Temperature dependences of photoconductivity of Au–Ag3AsS3–Au structure were researched.

Synthesis, structure and properties of two complexes based on N and S heterocyclic dicarboxylic acid ligands

The 3,4-ethylenedioxyethiophene-2,5-dicarboxylic acid (H2L1) and 4-chloropyridine-2, 6-dicarboxylic acid (H2L2) were used as the main ligands and 4,4' -bipyridine (L3) as the auxiliary ligand and the complexes {[Ni(L1)2(L3)(H2O)]·[(DMF)2(H2O)]}n(I), {[Cu(L2)(L3)H2O]·H2O}(II) were synthesized by solvent thermal reaction. The structure and properties of the complexes were characterized by X-ray single crystal diffraction, infrared spectroscopy (IR), fluorescence spectrum and thermogravimetric analysis. The results showed that complex I is a three-dimensional network structure. Complex II is formed with Cu(II) ions as the metal nodes and ligands as connecters, and a one-dimensional chain structure is further formed by intermolecular hydrogen bonding interaction.

Anomalous LO-TO splitting observed by combined IR reflectance and Raman scattering in KTiOPO4 (KTP) single crystal

A comprehensive study of vibrational spectra of a KTP single crystal is presented using both Raman scattering and Infrared (IR) reflectance. The 196 mode frequencies are listed according to a revised group theoretical analysis, which addresses the different atomic clusters comprising the crystal unit cell and their symmetry. Inverse LO-TO splitting is suggested to interpret the ν3 vibrational spectra of the PO43- clusters of the A1 symmetry. Theoretical account invokes a proximity between strong and weak polar vibrations and Lyddane-Sachs-Teller’s model of LO-TO splitting in a dielectric medium [1]. Many other mode frequencies appear too close to allow unequivocal interpretation of their LO-TO splitting sign.

Raman and optical absorption spectra of oriented Se8 and Se12 rings formed in zeolites: Dependence on the Se loading density

We encapsulated selenium (Se) into AFI and LTA zeolites via Se vapour adsorption at ∼450 °C and studied Raman and optical absorption spectra (RS and OAS, respectively) of zeolite single crystals with incorporated Se. At high Se loading density (D), Se8 rings are formed in the AFI channels along with Se chains. The rings are oriented by their 4-fold axis parallel to channels. Se8 is also formed in the LTA large cavities with its 4-fold axis oriented parallel to the 4-fold axis of LTA at any D up to ∼8 Se atoms per cavity (at/c). However, at D > 0.5 at/c, nearly unexplored Se12 rings oriented by their 3-fold axis parallel to the LTA 3-fold axis are formed along with Se8 in neighboring cavities. We discriminate between Se8 and Se12 rings via 1) RS frequencies; 2) RS and OAS band intensities vs. D; 3) RS band intensities vs. excitation wavelength and light polarization configuration. With an increase in D, the number of Se12 rings grows faster than that of Se8. We extract OAS of Se8 and Se12 from the experimental AFI-Se and LTA-Se OAS and show that the 3.0–3.3 eV absorption of Se12 is enhanced compared to that of Se8. This absorption is responsible for the observed resonant Raman effect of Se12 at the 514.5 nm wavelength excitation. Both LTA-confined Se8 and Se12 display rather high thermal stability.

Neritriterpenols A-G, euphane and tirucallane triterpenes from Euphorbia neriifolia L. and their bioactivity

Euphorbia neriifolia L. is widely distributed in India, Thailand, and China and has been used to treat diseases such as rotten sores and asthma as well as for its antidiabetic and anticancer effects. In this study, seven undescribed triterpenes, including six euphanes, neritriterpenols A-B and D-G, and a tirucallane, neritriterpenol C, together with four known triterpenes, were isolated from ethanolic extracts of E. neriifolia stems. Their structures with absolute configurations were determined through detailed spectroscopic data, including 1D and 2D NMR data analyses, single-crystal X-ray diffraction analysis, ECD spectra, and DP4+ NMR data calculations as well as Mo2(OAc)4-induced ECD analysis. Furthermore, preliminarily evaluation of the anti-inflammatory and anti-proliferative effects of the isolated triterpenes leads to the structure-activity relationship (SAR) studies implying that the unsaturated functional group at the end of the C17 side chain on euphane-type triterpenes may be correlated with the increase of anti-inflammatory and anti-proliferative activities.

On the issue of textured crystallization of Ba(NO3)2 in mesoporous SiO2: Raman spectroscopy and lattice dynamics analysis

The lattice dynamics of preferentially aligned nanocrystals formed upon drying of aqueous Ba(NO3)2 solutions in a mesoporous silica glass traversed by tubular pores of approximately 12 nm are explored by Raman scattering. To interpret the experiments on the confined nanocrystals polarized Raman spectra of bulk single crystals and X-ray diffraction experiments are also performed. Since a cubic symmetry is inherent to Ba(NO3)2, a special Raman scattering geometry was utilized to separate the phonon modes of Ag and Eg species. Combining group-theory analysis and ab initio lattice dynamics calculations a full interpretation of all Raman lines of the bulk single crystal is achieved. Apart from a small confinement-induced line broadening, the peak positions and normalized peak intensities of the Raman spectra of the nanoconfined and macroscopic crystals are identical. Interestingly, the Raman scattering experiment indicates the existence of comparatively large,∼10–20 μm, single-crystalline regions of Ba(NO3)2 embedded in the porous host, near three orders of magnitude larger than the average size of single nanopores. This is contrast to the initial assumption of non-interconnected pores. It rather indicates an inter-pore propagation of the crystallization front, presumably via microporosity in the pore walls.

The phosphorescence emission in undoped lead-halide Cs4PbBr6 single crystals at low temperature

Recently, all-inorganic cesium lead-halide perovskites have shown their promise for light emission applications, due to the excellent optical performance. Herein, we report that the initially nonphosphorescent undoped lead-halide Cs4PbBr6 single crystals (SCs) exhibit an ultralong phosphorescence emission under X-ray excitation at low temperatures. It is shown that the dramatic change has been taken place in radioluminescence spectra and the broad-band emission gradually appeared with the decrease of temperature. Below 210 K, the radioluminescence spectra can be deconvoluted into one narrow peak located at 530 nm and two broad peaks centered at 595 nm and 672 nm respectively. Subsequently, the time-dependent radioluminescence spectra in undoped lead-halide Cs4PbBr6 SCs were investigated. The ultralong phosphorescence emission can persist over 120 min at 70 K. We consider that ultralong phosphorescence originates from defect-related emission. To the best of our knowledge, our finding is the first time that undoped Cs4PbBr6 SCs exhibit the phosphorescence emission, which will offer a paradigm to motivate revolutionary applications on perovskite.

Electron Paramagnetic Resonance Study of the Radiation Damage Centers in Menadione Single Crystal

The radiation damage centers in the 60Co- rays irradiated menadione (2-methyl-1,4-naphthoquinone; Vitamin K3; C11H8O2 ) single crystals were examined at 120 K by Electron Paramagnetic Resonance (EPR) spectroscopy. The presence of two radicals was detected in the compound. Both radicals are carbon centered radicals. Analysis of the EPR spectra of gamma-irradiated menadione single crystals along three different axes showed that the C(11)-H(19) bond of the compound was broken. It was determined that the unpaired electron located on the C(11) atom. The g values and the hyperfine structure constants of the radiation damage centers observed in menadione single crystal were obtained. Accuracy of experimental data was observed by simulation study.