Vibrational Spectroscopic Study Research Articles

Crystal growth, thermal expansion, pyroelectricity and vibrational spectroscopy of barium antimony tartrate, Ba[Sb2((+)C4H2O6)2]·3H2O

The tetragonal polar barium antimony tartrate trihydrate, Ba[Sb2((+)C4H2O6)2]·3H2O, was grown to large single crystals of optical quality and several cm dimensions. A vibrational spectroscopy study, thermal expansion measurements and a determination of the pyroelectric properties were performed and possibilities for phase matching for second harmonic generation (SHG) were analysed. The crystals show a remarkable high pyroelectric coefficient, a moderate anisotropy of thermal expansion and allow for type I and type II phase matching for collinear SHG. A redetermination of the crystal structure of Ba[Sb2((+)C4H2O6)2]·3H2O at 150 K is given in addition, together with the vibrational spectra and crystal structures of two new related compounds, Ba[As2((+)C4H2O6)2]·3H2O and Ba[Sb2((+)C4H2O6)2]·4H2O, determined at the same temperature.

Synthesis, single crystal X-ray structure and vibrational spectroscopic characterization study of a new hybrid material crystal: Bis(2,4,6-trihydroxy-1,3,5-triazin-1-ium) bischloride monohydrate

A new hybrid material bis(2,4,6-trihydroxy-1,3,5-triazin-1-ium) bischloride monohydrate (2C3H4N3O3+.2Cl-.H2O) as a crystal has been synthesized and its structure was identified by single-crystal X-ray diffraction and studied by UV–Vis, FT-IR, FT-Raman and 1H NMR. The crystal of 2C3H4N3O3+.2Cl-.H2O belongs to monoclinic with C2/m space group system with Z = 4, a = 12.3845 (9) Å, b = 17.6236 (14) Å, c = 7.0260 (5) Å and β = 115.341 (2)°. The UV–Vis spectrum shows that the compound is transparent in visible and UV near visible domains. The FT-IR, FT-RAMAN and 1H NMR spectra of the crystal were discussed on the basis of crystallographic structure and the results were coherent and provides spectroscopic evidence for the crystal formation. In addition, the thermal decomposition of 2C3H4N3O3+.2Cl-.H2O has been also studied by TGA/DTG and DSC techniques and reveals that the material has a good thermal stability with the melting point about 310 °C.

Vibrational spectroscopic study on feed molecular structure properties of oil-seeds and co-products from Canadian and Chinese bio-processing and relationship with protein and carbohydrate degradation fractions in ruminant systems.

The objective of this study was to apply ATR-FTIR spectroscopy to reveal feed molecular structure properties of oil-seeds and co-products and relationship with protein and carbohydrate degradation fractions in ruminant systems. The oil-seeds and co-products were from both various bio-processing industries in Canada and China. The protein and carbohydrate degradation fractions were evaluated with updated CNCPS system. Results showed that in the co-products from canola processing industries there are strong relationship between 1) soluble true protein (PA2) fraction and the following protein molecular structure spectral characteristics; spectral peak area of amide I and amide II (r = 0.56, P = 0.001), area of amide I (r = 0.67, P < 0.001), height of amide I (r = 0.74, P < 0.001), amide I and II ratio (r = 0.57, P = 0.001), α-helix (r = 0.82, P < 0.001), and β-sheet (r = 0.61, P < 0.001), 2) slowly degradable true protein (PB2) fraction and height of amide I (r = -0.60, P = 0.001), α-helix (r = -0.72, P < 0.001), and β-sheet (r = -0.51, P = 0.004), 3) soluble fiber (CB2) fraction and α-helix and β-sheet height ratio (r = -0.63, P < 0.001), and 4) unavailable NDF (CC) fraction and height of amide I (r = 0.55, P = 0.002). These results indicated feed molecular structure spectral properties of the oil-seeds and co-products related to CNCPS protein and carbohydrate degradation fractions in ruminant systems.

Synthesis, thermal stability, vibrational spectra and conformational studies of novel dicationic meta-xylyl linked bis-1-methylimidazolium ionic liquids

In recent years, dicationic ionic liquids have been subject of a strongly growing research effort for their interesting and important properties that suggest them to be potential candidate for many applications. Therefore, the knowledge about the synthesis, thermal stability, vibrational spectra and conformational behavior of these compounds is an important subject of study. The objective of the work presented in this paper is to investigate the influence of the substituent relative meta-position of dicationic ionic liquids (ILs), namely meta-xylyl linked bis-1-methylimidazolium ILs, on thermal stability, vibrational spectra and conformational studies. In the first step, four new meta-xylyl linked bis-imidazolium [m-C6H4(CH2ImMe)2+] ionic liquid (ILs) containing the dichloride [Cl−]2, di(bis(trifluoromethylsulfonyl) Imide) [(CF3SO2)2N−]2, bis(tetrafluoroborate) [BF4−]2 and bis (hexafluorophosphate) [PF6−]2 anions were synthesized. The obtained dicationic ILs were characterized by 1H NMR, 13C NMR, 19F NMR, 31P NMR and FT-IR spectroscopy. Also, their thermal properties were determined and compared. The thermal behavior confirmed that [m-C6H4(CH2ImMe)2+] dicationic ILs containing [(CF3SO2)2N−]2 and [PF6−]2 are more stable that the dichloride [Cl−]2, and bis(tetrafluoroborate) [BF4−]2 dicationic ILs, and they show a good thermal stability up to 340 °C which makes them suitable for thermal application. In the next step, a computational study of the conformers of [m-C6H4(CH2ImMe)2], by means of DFT calculations with the 6-31G** basis set and the B3LYP theory was performed. Additionally, vibrational spectroscopy studies were conducted by infrared (FTIR) and Raman (FT-Raman) spectroscopy on the four dicationic ILs, differing for their anions. Finally a computational investigation of the interactions between anions and cation is presented.

Study of molecular structure and hydrogen bond interactions in dipfluzine-benzoic acid (DIP-BEN) cocrystal using spectroscopic and quantum chemical method.

The purpose of this article is to predict the molecular structure of the cocrystal of dipfluzine-benzoic acid (DIP-BEN) through computational approach (DFT calculations) and validate it using vibrational spectroscopic studies. The molecular structure of the DIP-BEN cocrystal has been predicted by forming models on the basis of the active sites available to form H-bonds between dipfluzine (DIP) and benzoic acid (BEN). Conformational study has been performed and potential energy surface scans are plotted around the flexible bonds of the cocrystal molecule and three stable conformers have been obtained. Quantum theory of atoms in molecules (QTAIM) explains that all the interactions are medium and partially covalent in nature. Natural bond orbital analysis of the second order perturbation theory of the Fock matrix suggests that interactions LP (2) O2 → σ*(O74H75) and LP (2) F1 → σ* (O89H90) are responsible for the stabilization of the molecule. The HOMO and LUMO energies and electronic charge transfer (ECT) confirms that charge flows from BEN to DIP. Global reactivity descriptor parameters suggest that DIP-BEN cocrystal is softer, thus more reactive in comparison to DIP. Local reactivity descriptor parameter is used to predict reactive sites of the cocrystal. The experimental and theoretical results support the formation of cocrystal through strong hydrogen bond (O89H90⋯F1 and O74H75⋯O2) interactions present in cocrystal.

Raman and FTIR Study of a 2, 3'-difluoro-4''-isothiocyanato-4-propyl-1,1':4',1''-terphenyl compound or C3P(3F)P(3F)P-NCS

A vibrational spectroscopy study of a laterally fluorinated terphenyl liquid crystalline (LC) compound is presented in this paper. The study consists of temperature dependent Raman study and room temperature FTIR spectroscopy. The molecular structure was optimized using Density Functional Theory (DFT) with B3LYP functional and 6-31G (d, p) basis set and some structural properties have been noted. From the detailed study of the temperature dependent Raman spectra, the nature of the phase transition of the LC compound was investigated. It was found that the quadrant stretching modes and the CH bending modes of the phenyl rings display significant changes at Cr-N transition and N-I transition. This study therefore throws some light on the nature of transitions. From the FTIR study, it was found that the CC vibrations of the rings and NCS vibrations have large absorptions while the CH bending modes have less absorption.

Optical and vibrational properties of nickel integrated germanium Zintl ion clusters

Vibrational and optical properties of Ni-Ge clusters ([Ni2Ge9(PPh3)]2−, [Ni6Ge13(CO)5]4−) have been investigated via UV–Vis, FTIR, and Fluorescence spectroscopies. Moreover, frequency and time-dependent (TD) electronic transition calculations have been performed to better characterize experimental findings, due to the scarcity of vibrational and optical spectroscopic studies on these type of clusters in the literature. UV–Vis spectroscopic analyses demonstrate a broad absorption band, with a maximum at 270 nm for both Ni-Ge clusters. [Ni6Ge13(CO)5]4− cluster band is broader and has a shoulder around 320 nm. Vibrational modes associated with the clusters appear at low-frequency region of FTIR spectra. [Ni6Ge13(CO)5]4− cluster spectrum is very rich as expected due to higher number of atoms in the cluster structure. Main vibrational modes of [Ni2Ge9(PPh3)]2− are observed at 318(m) cm−1 and 130(w) cm−1, and those of [Ni6Ge13(CO)5]4− appear at 232(s) cm−1 and 155(s) cm−1. Similarities observed between simulated and experimental spectra strongly support a stable, isolated cluster behavior in the crystal structure. Fluorescence spectroscopic analysis demonstrates that excitation of [Ni2Ge9(PPh3)]2− and [Ni6Ge13(CO)5]4− clusters at 260 nm has resulted relatively strong and broad emissions at 400 nm and 410 nm, respectively. [Ni2Ge9(PPh3)]2− and [Ni6Ge13(CO)5]4− clusters are two of the very few examples of Zintl ion clusters that have been characterized with UV–Vis and FTIR spectroscopic analyses, and the only ones that have been studied with fluorescence spectroscopy.

Molecular docking and vibrational spectroscopy studies of (E)-N′-hydroxy-1,3-diphenyl-4,5-dihydro-1H-pyrazole-5-carboximidamide

The experimental (FT-IR and Laser-Raman spectra) and theoretical (DFT studies) vibrational modes of (E)-N′-Hydroxy-1,3-diphenyl-4,5-dihydro-1H-pyrazole-5-carboximidamide were studied in detail. FT-IR and Laser-Raman data were collected in the range 4000-400 cm−1 and 4000-100 cm−1, respectively in solid phase. Optimized structural parameters and frequency values were theoretically calculated using DFT/B3LYP and DFT/M06-2X chemical methods with 6–311++G (d,p) basis set by Gaussian 09W software. Theoretical frequency assignments and potential energy distributions (PED) analysis were performed by VEDA 4 program. With the optimized structures, the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) energies and clouds were obtained and evaluated. Additionally, molecular docking studies for potent pyruvate kinase activators (PDB codes: 4RPP, 4FXJ, 4QG6, 4WJ8) and previously used targets (PDB codes: 2QU5, 2W1G and 2VTO-three different cancers related proteins) were employed for docking by AutoDock Vina program considering Swiss-Target reports and related literature knowledge.

Co-Crystal Formation of Antibiotic Nitrofurantoin Drug and Melamine Co-Former Based on a Vibrational Spectroscopic Study.

The co-crystallization of active pharmaceutical ingredients (APIs) has received increasing attention due to the modulation of the relative physicochemical properties of APIs such as low solubility, weak permeability and relatively inferior oral bioavailability. Crystal engineering plays a decisive role in the systematic design and synthesis of co-crystals by means of exerting control on the inter-molecular interactions. The characterization and detection of such co-crystal formations plays an essential role in the field of pharmaceutical research and development. In this work, nitrofurantoin (NF), melamine (MELA) and their hydrated co-crystal form were characterized and analyzed by using terahertz time-domain spectroscopy (THz-TDS) and Raman vibrational spectroscopy. According to the experimental THz spectra, the hydrated co-crystal form has characteristic absorption peaks at 0.67, 1.05, 1.50 and 1.73 THz, while the THz spectra for the two raw parent materials (NF and MELA) are quite different within this spectral region. Similar observations were made from the experimental Raman vibrational spectra results. Density functional theory (DFT) calculation was performed to help determine the major vibrational modes of the hydrated co-crystal between nitrofurantoin and melamine, as well as identify the structural changes due to inter- and/or intra-molecular hydrogen bonding motifs between NF and MELA. The results of the theoretical frequency calculations corroborate the THz and Raman experimental spectra. The characteristic bands of the NF–MELA-hydrated co-crystal between nitrofurantoin and melamine were also determined based on the DFT simulated calculation. The reported results in this work provide us with a wealth of structural information and a unique vibrational spectroscopic method for characterizing the composition of specific co-crystals and inter-molecular hydrogen bonding interactions upon pharmaceutical co-crystallization.

Structural, Spectroscopic, Electronic and Molecular Docking Studies on (11R,12 S)‐16‐Aminotetracyclo[6.6.2.02,7.09,14]hexadeca‐2(7),3,5,9(14),10,12‐hexaen‐15‐ol

AbstractMolecular structure analysis, vibrational and electronic spectroscopic studies and thermochemical features of (11R,12 S)‐16‐aminotetracyclo[6.6.2.02,7.09,14]hexadeca‐2(7),3,5,9(14),10,12‐hexaen‐15‐ol were investigated via both theoretical and experimental techniques. Experimental investigations were made by using FT‐IR, Raman, 1H and 13C NMR and UV‐Vis. spectroscopies. To support experimental evidences, molecular electronic structure computations were obtained with the DFT/B3LYP method at the 6–311G++(3d,3p) basis set. 2D and 3D Hirshfeld surfaces studies were performed to understand non‐bonding intermolecular interactions in solid phase crystal packing of the compound. MEP surface analysis was performed to investigate nucleophilic and electrophilic reactive sites of the compound. The highest occupied molecular orbitals (HOMOs) and lowest unoccupied molecular orbitals (LUMO) analyses were theoretically used for determination of electronic transitions corresponding to UV‐Vis. electronic absorption wavelengths. Enzyme‐ligand interactions between the compound with BACE1 (Beta‐Secretase1) inhibitor were determined via molecular docking study.

Palladium(II) complexes containing seven halogeno-derivatives of 7-azaindole: molecular structures, vibrational spectra, DFT calculations and in vitro cytotoxic activity

In the present work seven new complexes of Pd(II) containing halogeno-derivatives of 7-azaindole (7AIH), [PdCl2(L)2], where L = 3-chloro-7-azaindole (3Cl7AIH) or 3-bromo-7-azaindole (3Br7AIH) or 4-chloro-7-azaindole (4Cl7AIH) or 4-bromo-7-azaindole (4Br7AIH) or 5-bromo-7-azaindole (5Br7AIH) or 3-bromo-4-chloro-7-azaindole (3Br4Cl7AIH) or 5-bromo-3-chloro-7-azaindole (5Br3Cl7AIH) were prepared and studied by infrared and Raman spectroscopy accompanied by the DFT calculations. Full geometry optimizations and vibrational frequency calculations were performed for the two possible isomers cis and trans of [PdCl2(L)2] using the B3LYP method with the 6–311++G(d,p)/LanL2DZ basis sets. According to the theoretical results, the trans isomers are more stable than cis. As shown by the combined experimental and theoretical vibrational spectroscopic studies, only trans isomers with Ci symmetry are present, in the solid state. The combined experimental and theoretical studies have revealed that in [PdCl2(L)2] complexes, palladium(II) is bound to two pyridine nitrogen atoms of L ligands and to two chloride ions, in a square-planar trans arrangement. Detailed vibrational assignments of the experimental infrared and Raman spectra of these complexes have been made on the basis of the calculated potential energy distributions (PEDs). The antiproliferative activity of selected trans-[PdCl2(L)2] have been tested against human cancer cell lines (T47D, MCF7, A549 and A2780). The obtained IC50 values indicate that the title complexes possess lower cytotoxicity, in comparison to cisplatin.

The Effect of Phosphorous Doping on the Composition and Capacitance Properties of Mesoporous Graphitic Carbon Nitride

The effect of phosphorus doping on the composition and capacitance properties of mesoporous graphitic carbon nitride (MGCN) is investigated systemically and reported in this article. Pristine and phosphorous doped MGCN are synthesized by using a bio-compatible template, carboxymethyl cellulose, and orthophosphoric acid as a dopant. Powder X-ray diffraction and transmission electron microscopic studies confirm the formation of stacked layers of MGCN. Vibrational and X-ray photoelectron spectroscopic studies reveal that phosphorus is doped preferentially on the sites of carbon and, thereby induces defects. The defect and surface area are found to increase on increasing the dopant concentration. Owing to the presence of functionalities, such as P-O and C-P, P-doped MGCN delivers higher specific capacitance than pristine MGCN at all current rates. A symmetrical supercapacitor device fabricated using the electrodes of MGCN synthesized using 0.5 g of dopant delivers an energy density of 17.22 Wh kg−1 at a power density of 500 W kg−1.

The crystal structure of visible light absorbing piezoelectric semiconductor SrNb2V2O11revisited: high-resolution X-ray diffraction, vibrational spectroscopy and computational study

The crystal lattice of piezoelectric semiconductor Sr2Nb2V2O11adoptsCcordering due toΓ2−mode distortion.

Opening 2,2-diphenyl-2H-chromene to infrared light.

Time-resolved vibrational spectroscopy studies are reported on the photoinduced structural dynamics of 2,2-diphenyl-2H-chromene, a prototypical photochromic compound that undergoes ring opening upon UV radiation. The transient IR absorption measurements in combination with (TD-)DFT calculations have been used to understand in detail the life cycle of such compounds. Excited-state decay and ring opening was found to occur on an ultrafast time scale. Three species have been identified in the time-resolved IR spectra with two short-lived species (on a picosecond timescale) and a final long-lived species that remains after the measurable ns delay range. These species have been assigned to various open isomers using quantum chemical calculations of equilibrium structures and force fields. From the experiments and calculations key conclusions can be drawn on previously suggested models for the photocycle of such compounds, as well as on possible ways to controllably influence the performance of these compounds.

Synthesis of microporous silica nanoparticles to study water phase transitions by vibrational spectroscopy.

Silica can take many forms, and its interaction with water can change dramatically at the interface. Silica based systems offer a rich tapestry to probe the confinement of water as size and volume can be controlled by various templating strategies and synthetic procedures. To this end, microporous silica nanoparticles have been developed by a reverse microemulsion method utilizing zinc nanoclusters encapsulated in hydroxyl-terminated polyamidoamine (PAMAM-OH) dendrimers as a soft template. These nanoparticles were made tunable within the outer diameter range of 20–50 nm with a core mesopore of 2–15 nm. Synthesized nanoparticles were used to study the effects of surface area and microporous volumes on the vibrational spectroscopy of water. These spectra reveal contributions from bulk interfacial/interparticle water, ice-like surface water, liquid-like water, and hydrated silica surfaces suggesting that microporous silica nanoparticles allow a way to probe silica water interactions at the molecular scale.

Vibrational spectroscopic study on the phase transition of water in nanospaces and at interfaces

Vibrational spectroscopic study on the phase transition of water in nanospaces and at interfaces

Strong intramolecular hydrogen bonding in protonated β-methylaminoalanine: A vibrational spectroscopic and computational study.

The gas-phase structure of protonated β-methylaminoalanine was investigated using infrared multiple photon dissociation spectroscopy in the C-H, N-H, O-H stretching region (2700-3800 cm-1) and the fingerprint region (1000-1900 cm-1). Calculations using density functional theory methods show that the lowest energy structures prefer protonation of the secondary amine. Formation of hydrogen bonds between the primary and secondary amine, and the secondary amine and carboxylic oxygen further stabilize the lowest energy structure. The infrared spectrum of the lowest energy structure originating with harmonic density functional theory has features that generally match the positions of the experimental spectra; however, the overall agreement with the experimental spectrum is poor. Molecular dynamics calculations were used to generate a gas-phase infrared spectrum. With these calculations a reasonable match with the experimental spectrum, especially in the high-energy region, was obtained. The results of the molecular dynamics simulation support the density functional theory calculations, with protonation of the secondary amine and the formation of a hydrogen bond between the protonated secondary amine and the primary amine. This work shows the importance of accounting for anharmonic effects in systems with very strong intramolecular hydrogen bonding.

Solvation structures formed in the MgCl2:AlCl3-dimethoxyethane system: A look through Raman and IR spectroscopies

A concentration-dependent vibrational spectroscopic study is carried out for the 1:1 MgCl2:AlCl3-DME system and detailed information on the precursor and the electrochemically active species formed in this rechargeable Mg battery electrolyte are presented for the first time in solution. An equilibrium between trans-[MgCl2(DME)2] and cis-[MgCl2(DME)2] isomers is proposed as well as the formation of [Mg2(μ-Cl)2]2+ and [AlCl4]− by using Raman and IR spectroscopies. The combination of the quantitative analysis made at the CO stretching region of DME with the spectral trend exhibited in low wavenumber suggests the existence of the [Mg2(μ-Cl)2(DME)4]2+ complex, similar to structure previously resolved by X-ray diffraction, in which two [AlCl4]− anions maintain the neutrality of the system.

Structural, vibrational and thermal properties of a new inorganic compound: Tl0.92(NH4)0.08(SO4)0.65(SeO4)0.35Te(OH)6

A new compound thallium ammonium sulfate selenate tellurate: Tl0.92(NH4)0.08(SO4)0.65(SeO4)0.35Te(OH)6 (TlNSSeTe) has been synthesized by slow evaporation at room temperature to specify its phase transition temperatures. X-ray diffractometry data revealed crystallization in the monoclinic system with a P21/c space group with these parameters: a = 12.336(2) A, b = 7.2038(14) A, c = 12.017(2) A et β = 110.631(10)°, V = 999.4(3) A3 and Z = 4. Three coexisting anions (TeO\( _{6}^{6 - } \), SO\( _{4}^{2 - } \) and SeO\( _{4}^{2 - } \)) are the main characteristics of these atomic arrangements in the unit cell, related by O–H…O and N–H…O bonds building up the crystal. The cations Tl+ and NH\( _{4}^{ + } \) lie at the same positions between these polyhedra. The new synthesized compound has been characterized by using the differential scanning calorimetry (DSC), thermal analysis [differential thermogravimetric analysis (TG), as well as thermodifference analysis (DTA)], FT-IR and Raman spectroscopy techniques. The DSC results demonstrated phase transitions at 384 K, 465 K and 472 K. DTA and TG proved that decomposition takes place in three steps. The vibrational spectroscopy study at room temperature unveiled not only the occurrence and the independence of anionic and cationic groups, but also the importance of the hydrogen bonds.

A Nuclear Resonance Vibrational Spectroscopic Study of Oxy Myoglobins Reconstituted with Chemically Modified Heme Cofactors: Insights into the Fe-O2 Bonding and Internal Dynamics of the Protein.

The molecular mechanism of O2 binding to hemoglobin (Hb) and myoglobin (Mb) is a long-standing issue in the field of bioinorganic and biophysical chemistry. The nature of Fe-O2 bond in oxy Hb and Mb had been extensively investigated by resonance Raman spectroscopy, which assigned the Fe-O2 stretching bands at ∼570 cm-1. However, resonance Raman assignment of the vibrational mode had been elusive due to the spectroscopic selection rule and to the limited information available about the ground-state molecular structure. Thus, nuclear resonance vibrational spectroscopy was applied to oxy Mbs reconstituted with 57Fe-labeled native heme cofactor and two chemically modified ones. This advanced spectroscopy in conjunction with DFT analyses gave new insights into the nature of the Fe-O2 bond of oxy heme by revealing the effect of heme peripheral substitutions on the vibrational dynamics of heme Fe atom, where the main Fe-O2 stretching band of the native protein was characterized at ∼420 cm-1.