Solid-state Raman Spectroscopy Research Articles

Synthesis, XRD and DFT studies on Pb[ChCN]2 (Ch = O, S, Se) and Pb[SeCN][OH

We report on the synthesis of Pb[ChCN]2 (Ch = O, S, Se) and Pb[SeCN][OH] and their hitherto unknown crystal structures. All products were fully characterized by single-crystal and powder X-ray diffraction. Bulk analysis was performed by Rietveld refinement, elemental analysis, differential scanning calorimetry-thermogravimetric analysis (DSC-TGA), and solid-state Raman spectroscopy. Quantum-mechanical calculations based on the density functional theory allowed optimization of the structural parameters of these lead-based compounds, as well as assessment of their electronic structures and detailed assignment and interpretation of the vibrational spectra. In addition, the origin of bands related to difficulties in assigning the exact position of H atoms in the structures was resolved.

Systematic error in conventionally measured Raman spectra of boron carbide-A general issue in solid state Raman spectroscopy.

Solid state Raman spectroscopy requires careful attention to the penetration depth of exciting laser radiation. In cases like semiconducting boron carbide and metallic hexaborides, high fundamental absorption above the bandgap and reflectivity R ≈ 1 beyond the plasma edge respectively prevent the excitation of bulk phonons largely. Thus, correspondingly measured spectra stem preferably from surface scattering. For decades, Raman spectra of boron carbide obtained with different equipment were controversially discussed. Now, common features of icosahedral phonons in Fourier transform-Raman spectra of B4.3C and Raman spectra of α-rhombohedral boron evidence their bulk character, while refuting conventionally measured Raman spectra.

Reversible Gas-Solid Ammonia N-H Bond Activation Mediated by an Organopalladium Complex.

N-H bond activation of gaseous ammonia is achieved at room temperature in a reversible solvent-free reaction using a solid dicyclopalladated azobenzene complex. Monitoring of the gas-solid reaction in real-time by in situ solid-state Raman spectroscopy enabled a detailed insight into the stepwise activation pathway proceeding to the final amido complex via a stable diammine intermediate. Gas-solid synthesis allowed for isolation and subsequent structural characterization of the intermediate and the final amido product, which presents the first dipalladated complex with the PdII-(μ-NH2)-PdII bridge. Gas-solid reaction is readily followed via color changes associated with conformational switching of the palladated azobenzene backbone. The reaction proceeds analogously in solution and was characterized by UV-vis and NMR spectroscopies showing the same stepwise route to the amido complex. Combining the experimental data with density functional theory calculations we propose a stepwise mechanism of this heterolytic N-H bond activation assisted by exogenous ammonia.

Position and Orientation Control of a Photo- and Electrochromic Dithienylethene Using a Tripodal Anchor on Gold Surfaces

A tripodal system for anchoring photochromic dithienylethenes on gold surfaces is reported. The self-assembled monolayers of a tripod-functionalized dithienylethene were characterized by cyclic voltammetry, surface-enhanced Raman spectroscopy (SERS), and X-ray photoelectron spectroscopy (XPS). These data are compared with solution studies, solid state Raman spectroscopy, and density functional theory (DFT) calculations. We show that the tripod-functionalized dithienylethene forms stable monolayers on gold in which all three legs of the tripod are adsorbed via the thiol units, thus providing a fixed position and orientation of the dithienylethene moiety with respect to the surface. Importantly, immobilization in this way allows for retention of both the photochemical and electrochemical functionality of the dithienylethene unit and reduces photochemical fatigue observed in solution.

Mechanochemical C-H bond activation: rapid and regioselective double cyclopalladation monitored by in situ Raman spectroscopy.

The first direct mechanochemical transition-metal-mediated activation of strong phenyl C-H bonds is reported. The mechanochemical procedure, resulting in cyclopalladated complexes, is quantitative and significantly faster than solution synthesis and allows highly regioselective activation of two C-H bonds by palladium(II) acetate in asymmetrically substituted azobenzene. Milling is monitored by in situ solid-state Raman spectroscopy which in combination with quantum-chemical calculations enabled characterization of involved reaction species, direct insight into the dynamics and reaction pathways, as well as the optimization of a milling process.

Photocrystallographic identification of metastable nitrito linkage isomers in a series of nickel(ii) complexes

Single crystal photocrystallographic experiments and solid state Raman spectroscopy have been used to determine the low temperature, metastable structures of the nickel(ii) nitrito complexes [Ni(aep)(2)(η(1)-ONO)(2)] 1#O (aep = 1-(2-aminoethyl)piperidine), [Ni(aem)(2)(η(1)-ONO)(2)] 2#O (aem = 1-(2-aminoethyl)morpholine), and [Ni(aepy)(2)(η(1)-ONO)(2)] 3#O (aepy = 1-(2-aminoethyl)pyrrolidine and where the #O denotes the oxygen-bound nitrito metastable molecule). These linkage isomers of the equivalent nitro complexes [Ni(aep)(2)(η(1)-NO(2))(2)] 1, [Ni(aem)(2)(η(1)-NO(2))(2)] 2 and [Ni(aepy)(2)(η(1)-NO(2))(2)] 3 are formed by LED irradiation at temperatures below 120 K. The behavior of the three complexes upon irradiation is generally similar, but some subtle differences have been observed. From the crystallographic studies all three complexes 1-3 exhibit the endo-nitrito linkage isomer upon irradiation, however, for 3# (a crystal structure that contains components of both 3 and 3#O) an exo-nitrito isomer is also observed. Under conditions of 90-100 K, with blue light, the conversion percentages to the nitrito isomers, 1#O, 2#O and 3#O were 16%, 22% and 30%, respectively. At temperatures below 110 K all three nitrito isomers were stable for over four hours but while 2#O and 3#O could be detected at temperatures down to 30 K, at temperatures below 60 K the metastable structure 1#O appeared to be quenched and only the nitro isomer 1 was identified in the crystal. The solid state Raman spectra for 1#, 2# and 3# confirmed the photocrystallographic results with the nitrito isomers being identified from the O-N-O deformation vibrations.

A quantitative solid-state Raman spectroscopic method for control of fungicides

A new analytical procedure using solid-state Raman spectroscopy within the THz-region for the quantitative determination of mixtures of different conformations of trifloxystrobin (EE, EZ, ZE and ZZ), tebuconazole (1), and propiconazole (2) as an effective method for the fungicide product quality monitoring programmes and control has been developed and validated. The obtained quantities were controlled independently by the validated hybrid HPLC electrospray ionization (ESI) tandem mass spectrometric (MS) and matrix-assisted laser desorption/ionization (MALDI) MS methods in the condensed phase. The quantitative dependences were obtained on the twenty binary mixtures of the analytes and were further tested on the three trade fungicide products, containing mixtures of trifloxystrobin-tebuconazole and trifloxystrobin-propiconazole, as an emissive concentrate or water soluble granules of the active ingredients. The present methods provided sufficient sensitivity as reflected by the metrologic quantities, evaluating the concentration limit of detection (LOD) and quantification (LOQ), linear limit (LL), measurement accuracy and precision, true quantity value, trueness of measurement and more.

On the chemical identification and determination of flavonoids in solid-state

The paper presented with qualitative and quantitative analysis of alkaloids in solid-state, using the excitations within the THz-spectroscopic region of 300–30cm−1 (9.00–0.9THz). Series of nine plant flavonoids (FLs) and their mixtures were analyzed both qualitatively and quantitatively. For first time in the literature was reported the quantitative analysis of alkaloids and their mixtures within the THz-region using the solid-state Raman spectroscopy, and matrix-assisted laser desorption/ionization (MALDI) mass spectrometry (MS). The calibration and validation, concentration limit of detection (LOD), limit of quantification (LOQ), and linearity limit (LL) were obtained. The chemometric nonlinear and linear approaches for analysis and interpretation of the quantities were applied. The results obtained were compared with a parallel QA, using the calibrated and validated HPLC electrospray ionization (ESI) mass spectrometric method, electronic absorption (EAs) and CD spectroscopy. The metrology, including accuracy, measurement repeatability (intra-serial precision condition of measurement), measurement precision, trueness of the measurement, and reproducibility of the measurement, measurement bias and errors of the measurements were discussed.

New Polymorphs of Fluconazole: Results from Cocrystallization Experiments

Fluconazole is known as an antifungal drug since 1983. Its propensity for the formation of new polymorphs and salts has been reported in the literature, mostly by powder X-ray diffraction and solid state Raman spectroscopy. In the present study, we are elucidating the structures of four polymorphs of fluconazole using single crystal X-ray diffraction. Raman spectra of the single crystals of these polymorphs also support our study. These polymorphs were grown in the presence of the cocrystal formers. This indicates that fluconazole interacts with the cocrystal former in the solution, and possibly these interactions result into the generation of new polymorphs of it. These polymorphs of fluconazole exhibit the conformational flexibility of the molecule, and hence we observed seven different conformers of the molecule in the reported polymorphs. Although these forms have strong O–H···N hydrogen bonds, the nature of the packing of the molecules is a cumulative effect of a number of weaker intermolecular forces such as C–H···O, C–H···N, and C–H···F and the strong hydrogen bond.

Physical optical properties and crystal structures of organic 5-sulfosalicylates – Theoretical and experimental study

A discussion on the possible application of the organic 5-sulfosalicylates as organic materials with tunable optical and non-linear-optical (NLO) properties is performed on the basis of the experimental crystallographic and spectroscopic methods such as single crystal X-ray diffraction, electronic absorption, diffuse reflectance and fluorescence spectroscopy in condense phase, conventional and linear-polarized IR- and Raman spectroscopy in solid-state. The model systems 5-sulfosalicylic acid dihydrate ( 1), 4-aminobenzamidinium bis(5-sulfosalicylicilate) monohydrate ( 2) and 5-sulfosalicylicilate salt of glycinamide ( 3), comparing with the as well as theoretical quantum chemical calculations of the systems neutral 5-sulfosalicylic acid ( I), its mono-( Ia) and dianion ( Ib), respectively.

Synthesis of n-type CuInS2 Particles Using N-methylimidazole, Characterization and Growth Mechanism

We report on the growth of CuInS2 n-type semiconductive particles, prepared using N-methylimidazole, as a solvent and/or a complexing agent, as well as their chemical and electrochemical properties. XPS, EDX and ICP-AES have shown that an excess of indium was obtained, which was greater at the surface (CuIn1.19S1.7 at 500 °C) than in the bulk (CuIn1.07S1.9 at 500 °C). Solid state Raman spectroscopy revealed two crystalline phases: chalcopyrite and the so-called copper−gold phase, and by increasing the annealing temperature of the particles, the formation of the chalcopyrite phase is favored. UV−visible measurements showed that the n-type CuInS2 possesses a direct bandgap energy of 1.55 eV. To perform the capacitance measurements on a CuInS2 film by EIS, we used two organic redox couples in nonaqueous media: 5-mercapto-1-methyltetrazolate (T−)/di-5-(1-methyltetrazole) disulfide (T2), and 5-trifluoromethyl-2-mercapto-1,3,4-thiadiazolate (G−)/5,5′-bis(2-trifluoromethyl-1,3,4-thiadiazole) disulfide (G2). Usin...

Synthesis, Characterization, and Growth Mechanism of n-Type CuInS2 Colloidal Particles

We report on the growth of CuInS2 n-type semiconductive particles, prepared using a modified Czekelius’s colloidal method, as well as their chemical and electrochemical properties. Solid state Raman spectroscopy revealed two crystalline phases: chalcopyrite and the so-called copper−gold phase. Increasing the annealing temperature of the particles favors the formation of the chalcopyrite phase. As shown by XPS, EDX, and ICP-AES, an excess of indium was obtained, which was greater at the surface (CuIn1.45S1.9 at 450 °C) than in the bulk (CuIn1.04S1.74 at 450 °C). UV−visible measurements showed that the n-type CuInS2 possesses a direct bandgap energy of 1.45 eV. Two organic redox couples in nonaqueous media were used to perform the capacitance measurements carried out by EIS on a CuInS2 film: 5-mercapto-1-methyltetrazolate (T−)/di-5-(1-methyltetrazole) disulfide (T2) and 5-trifluoromethyl-2-mercapto-1,3,4-thiadiazolate (G−)/5,5′-bis(2-trifluoromethyl-1,3,4-thiadiazole) disulfide (G2). Fermi levels of −3.95 e...

Synthesis, Rietveld Analysis and Solid State Raman Spectroscopy of K4SrSi3O9

AbstractThe crystal structure of K4SrSi3O9 has been determined from laboratory X‐ray powder diffraction data using polycrystalline material prepared from solid state reactions. The compound crystallizes with 16 formula units in a cubic primitive unit cell (a = 16.16957(5) Å, V = 4227.62(2) Å3) and adopts space group $Pa{\bar 3}$. The structure belongs to the group of cyclosilicates and is isotypic with Na4CaSi3O9 and other similar silicates and germanates. It contains puckered twelve‐membered [Si12O36]‐rings centered on the ${\bar 3}\rm -axes$. The rings are connected by seven different M‐sites occupied by potassium or strontium atoms. Five of the seven crystallographically independent alkaline and alkaline earth cations are surrounded by six oxygen ligands in the form of distorted octahedra. The octahedra share opposite triangular faces, building non‐intersecting columns parallel to the body diagonals of the cubic unit cell. The arrangement of these rods corresponds to one of the cubic cylinder or rod packings. The remaining two potassium sites have more irregular coordination environments with eight next oxygen neighbors. Structural investigations are completed by solid state Raman spectroscopy.

Synthesis and Characterization of Two Quaternary Thorium Chalcophosphates: Cs4Th2P6S18 and Rb7Th2P6Se21.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Synthesis and Characterization of Two Quaternary Thorium Chalcophosphates: Cs4Th2P6S18 and Rb7Th2P6Se21

Two new thorium chalcophosphates have been synthesized by the reactive flux method and characterized by single-crystal X-ray diffraction, diffuse reflectance, and Raman spectroscopy: Cs4Th2P6S18 (I); Rb7Th2P6Se21 (II). Compound I crystallizes as colorless blocks in the triclinic space group P1 (No. 2) with a = 12.303(4) A, b = 12.471(4) A, c = 12.541(4) A, alpha = 114.607(8) degrees, beta = 102.547(6) degrees, gamma = 99.889(7) degrees, and Z = 2. The structure consists of (Th2P6S18)(4-) layers separated by layers of cesium cations and only contains the (P2S6)(4-) building block. Compound II crystallizes as red blocks in the triclinic space group P1 (No. 2) with a = 11.531(3) A, b = 12.359(4) A, c = 16.161(5) A, alpha = 87.289(6) degrees, beta = 75.903(6) degrees, gamma = 88.041(6) degrees, and Z = 2. The structure consists of linear chains of (Th2P6Se21)(7-) separated by rubidium cations. Compound II contains both the (PSe4)(3-) and (P2Se6)(4-) building blocks. Both structures may be derived from two known rare earth structures where a rare earth site is replaced by an alkali or actinide metal to form these novel structures. Optical band gap measurements show that compound I has a band gap of 2.8 eV and compound II has a band gap of 2.0 eV. Solid-state Raman spectroscopy of compound I shows the vibrations expected for the (P2S6)(4-) unit. Raman spectroscopy of compound II shows the vibrations expected for both (PSe4)(3-) and (P2Se6)(4-) units. Our work shows the remarkable diversity of the actinide chalcophosphate system and demonstrates the phase space is still ripe to discover new structures.

Synthesis and Characterization of a New Quaternary Lanthanum Oxythioantimonite: La6Sb4O12S3.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Synthesis and characterization of a new quaternary lanthanum oxythioantimonite: La 6Sb 4O 12S 3

A new lanthanum antimony chalcogenide compound has been synthesized by the combination of ZnO–Sb 2S 3–La 2O 3 at 1150 °C and characterized by single-crystal X-ray diffraction. The compound La 6Sb 4O 12S 3 crystallizes in the tetragonal space group I4 1/ amd with a=10.860(3) Å, c=15.316(5) Å, and Z=4. The structure comprises a three-dimensional network of lanthanum oxysulfide polyhedra connected by antimony(III) oxide psi-tetrahedra. The structure forms around channels that are filled with a disordered sulfide anion that appears to be loosely held in the solid. Diffuse reflectance measurements showed that this compound has an optical band gap of 2.2 eV. Solid state Raman spectroscopy of this compound showed the vibrations expected for the [Sb IIIO 3] 3− unit. According to thermal analysis data, this material decomposes at temperatures over 1050 °C.

Selenophosphate phase diagrams developed in conjunction with the synthesis of the new compounds K(2)La(P(2)Se(6))(1/2)(PSe(4)), K(3)La(PSe(4))(2), K(4)La(0.67)(PSe(4))(2), K(9-x)La(1+x/3)(PSe(4))(4) (x = 0.5), and KEuPSe(4).

Five new rare-earth metal polyselenophosphates have been synthesized by the reactive flux method and characterized by single-crystal X-ray diffraction: K(2)La(P(2)Se(6))(1/2)(PSe(4)) (I), K(3)La(PSe(4))(2) (II), K(4)La(0.67)(PSe(4))(2) (III), K(9-x)()La(1+)(x/3)(PSe(4))(4) (x = 0.5) (IV), and KEuPSe(4) (V). Compound I crystallizes in the monoclinic space group P2(1)/n with a = 9.4269(1) A, b = 7.2054(1) A, c = 21.0276(5) A, beta = 97.484(1) degrees, and Z = 4. Compound II crystallizes in the monoclinic space group P2(1)/c with a = 9.5782(2) A, b = 17.6623(4) A, c = 9.9869(3) A, beta = 90.120(1) degrees, and Z = 4. Compound III crystallizes in the orthorhombic space group Ibam with a = 19.0962(2) A, b = 9.1408(1) A, c = 10.2588(2) A, and Z = 4. Compound IV crystallizes in the orthorhombic space group Ccca with a = 18.2133(1) A, b = 38.0914(4) A, c = 10.2665(1) A, and Z = 8. Compound V crystallizes in the orthorhombic space group Pnma with a = 17.5156(11) A, b = 7.0126(5) A, c = 6.9015(4) A, and Z = 4. Optical band gap measurements show that compound V has an optical band gap of 1.88 eV. Solid-state Raman spectroscopy of compounds II-V shows the four normal vibrations expected for the (PSe(4))(3-) unit. The observation of compounds I-V in several reactions has allowed the creation of a quasi-quaternary phase diagram for potassium rare-earth-metal polyselenophosphates. This phase diagram can qualitatively be separated into three regions on the basis of the oxidation state of phosphorus in the crystalline products observed and takes the next step in designing solid-state compounds.

Planar and Nonplanar Conformations of (meso-Tetraphenylporphinato)nickel(II) in Solution As Inferred from Solution and Solid-State Raman Spectroscopy

The coexistence in solution of at least two conformers of (meso-tetraphenylporphinato)nickel(II) [Ni(TPP)] is inferred from solution and single-crystal resonance Raman spectra obtained at different temperatures (170 − 297 K) and excitation wavelengths (413.1 and 457.9 nm). The shapes of the structure-sensitive Raman lines ν8 and ν2 are clearly asymmetric and change with temperature. These broad lines can be decomposed into at least two sublines, a low-frequency (LF) and a high-frequency (HF) component. In contrast, the corresponding single-crystal Raman lines of the nonplanar structure of Ni(TPP) in the crystal are narrow and symmetric. For the line ν2, the broad LF subline results from nonplanar conformers and the narrow HF subline arises from a more planar conformer. This assignment is consistent with the observation that the LF subline of ν2 is more enhanced upon changing the excitation wavelength from 413.1 to 457.9 nm. The selective resonance enhancement is caused by the red shifts of the UV−visible ...