Molecular dynamics calculation of spectral characteristics of water clusters in the presence of ozone molecules and chlorine ions

Simultaneous interaction of the (H₂O)₅₀ cluster with O₃ molecules and Cl⁻ ions was studied by the molecular dynamics method. Six O₃ molecules located near the cluster were absorbed by the aqueous aggregate, and Cl⁻ ions in turn left the zone of the interaction with the cluster. Some of Cl⁻ ions penetrated inside the formed (O₃)₆(H₂O)₅₀ cluster and come into collision with O₃ molecules that split the ozone molecule into atoms. When Cl⁻ ions were removed sufficiently far away from the cluster, the water cluster with absorbed O₃ molecules and O atoms was observed for 15.6 ps. The interaction of water molecules with Cl⁻ ions gives rise to an increase in the integral intensity of absorption and emission IR spectra, and also to an essential decrease in the analogous characteristics of the Raman spectrum in the frequency range of 0 ≤ ω ≤ 1000 cm⁻¹. The presence of Cl⁻ ions did not affect essentially the location of the main band in the IR spectra, but considerably changed the shape of the bands in the Raman spectrum.     

黄曲霉素B2分子吸附在银团簇的表面增强拉曼散射机理

采用密度泛函理论（DFT）B3LYP方法,6-311G（d,p）（C,H,O）/LANL2DZ（Ag）基组,计算了黄曲霉素B₂（AFB₂）分子吸附在Ag₂团簇的表面增强拉曼散射（SERS）光谱和预共振拉曼光谱,并与实验结果比较. 结果显示：AFB₂分子在基态Ag₂团簇表面吸附时,增强因子最大达到10²,对应吡喃（pyrane）环C=O伸缩振动,主要是由AFB₂分子周围化学环境改变而引起的基态静极化率改变导致的化学增强. 不同激发波长下的AFB₂分子预共振拉曼光谱的增强强度不同：电荷转移态激发波长为1144 和544 nm时拉曼信号增强了10²倍,而选择电荷转移预共振波长432和410 nm作为入射光时,其拉曼信号增强了10⁴倍,增强机理为银团簇和黄曲霉素分子之间的电荷转移共振增强. 因此通过改变入射光波长,选择电荷转移共振激发波长,更有利于强致癌物AFB₂分子的痕量检测.     

Cobalt(II) Chloride Complex Formation in Acetamide–Calcium Nitrate Tetrahydrate Melts

The absorption spectra of Co(II) chloride complexes, containing variable concentrations of chloride ligand, in a molten mixture of 80 mol% acetamide–20 mol% calcium nitrate tetrahydrate, were studied at 313, 333, 353, and 363 K, in the wavelength range 400-800 nm. The melt contains three possible ligands (CH₃CONH₂, H₂O, and NO₃ ^-) for competition with added chloride ligand. Addition of chloride caused a shift of the absorption maximum of octahedral cobalt(II) nitrate towards lower energies and pronounced changes in the shape of the initial spectrum of cobalt(II) nitrate. The effect of temperature changes on the molar absorption coefficient of the Co(II) species was dependent on the chloride concentration and was attributed to the structural changes occurring in the cobalt(II) species. The STAR and STAR FA programs were applied to identify the complex ionic species and to calculate the stability constants of Co(II) complexes formed in this solvent. The results indicate the highest probability of formation of the following complex species: Co(NO₃)₄ ^2-, Co(NO₃)₂Cl₂ ^2-, and CoCl₄ ^2-. Stability constants of each complex were presented for the equilibria occurring at 313, 333, 353, and 363 K. Distribution of the Co(II) species was also calculated over the ranges of chloride concentration and temperature investigated.     

A DFT Investigation of Surface‐Enhanced Raman Scattering of Adenine and 2′‐Deoxyadenosine 5′‐Monophosphate on Ag20 Nanoclusters

We present a detailed analysis of the surface‐enhanced Raman scattering (SERS) of adenine and 2′‐deoxyadenosine 5′‐monophosphate (dAMP) adsorbed on an Ag₂₀ cluster by using density functional theory. Calculated Raman spectra show that spectral features of all complexes depend greatly on adsorption sites of adenine and dAMP. The complexes consisting of adenine adsorbed on the Ag₂₀ cluster through N3 reproduce the measured SERS spectra in silver colloids, and thus demonstrated that adenine interacts with the silver surface via N3. We also investigate the SERS spectrum of adenine at the junction between two Ag₂₀ clusters and demonstrate that adenine can bind to the clusters through N3 and the external amino group, while dAMP can be adsorbed on the cluster in an end‐on orientation with the ribose and phosphate groups near to or away from the silver cluster. In contrast to the adenine–Ag₂₀ complexes, the dAMP–Ag₂₀ complexes produce new and strong bands in the low‐ or high‐wavenumber region of the Raman spectra, due to vibrations of the ribose and phosphate groups. Furthermore, the spectrum of dAMP bound to the Ag₂₀ cluster via N7 approaches the experimental SERS spectra on silver colloids.     

Probing Charge-Transfer Processes in a Covalently Linked [Ge9]-Cluster Imine Dyad

C₆₀ donor dyads in which the carbon cage is covalently linked to an electron-donating unit have been discussed as one possibility for an electron-transfer system, and it has been shown that spherical [Ge₉] cluster anions show a close relation to fullerenes with respect to their electronic structure. However, the optical properties of these clusters and of functionalized cluster derivatives are almost unknown. We now report on the synthesis of the intensely red [Ge₉] cluster linked to an extended π-electron system. [Ge₉{Si(TMS)₃}₂{CH₃C=N}-DAB(II)^Dipp]⁻ ( 1⁻ ) is formed upon the reaction of [Ge₉{Si(TMS)₃}₂]²⁻ with bromo-diazaborole DAB(II)^Dipp-Br in CH₃CN (TMS=trimethylsilyl; DAB(II)=1,3,2-diazaborole with an unsaturated backbone; Dipp=2,6-di-iso-propylphenyl). Reversible protonation of the imine entity in 1⁻ yields the deep green, zwitterionic cluster [Ge₉{Si(TMS)₃}₂{CH₃C=N(H)}-DAB(II)^Dipp] ( 1-H ) and vice versa. Optical spectroscopy combined with time-dependent density functional theory suggests a charge-transfer excitation between the cluster and the antibonding π* orbital of the imine moiety as the cause of the intense coloration. An absorption maximum of 1-H in the red region of the electromagnetic spectrum and the corresponding lowest-energy excited state at λ=669 nm make the compound an interesting starting point for further investigations targeting the design of photo-active cluster compounds.     

Raman study of halogen exchange equilibria in low melting mixtures consisting of sodium tetrachloroaluminate and tetrabromoaluminate

The halogen-redistribution reactions between [AlCl₄]^? and [AlBr₄]^? in molten mixtures of NaAlCl₄ and NaAlBr₄ with widely varying mole ratios have been studied by Raman spectroscopy at 160–300°C and the melting points have been measured. By monitoring the intensities of the totally symmetric stretching a₁-modes of both the parent tetrahalides as well as those of the mixed halides [AlCl₃Br]^?, [AlCl₂Br]^? and [AlClBr₃]^? it is concluded that the mixtures equilibrate very fast and consist of an almost random distribution of the five species. NaAlCl₄ and NaAlBr₄ form an eutectic mixture with a molar ratio near to 4:1, with a melting point of ca 142°C.     

Importance of weak interactions and conformational equilibrium in N-butyl-N-methylpiperidinium bis(trifluromethanesulfonyl) imide room temperature ionic liquids: Vibrational and theoretical studies

Piperidinium cation-based room temperature ionic liquids (RTILs) constitute an important class of ILs because of their unique electrochemical properties as well as non-aromatic nature of the cation. However, detailed structural studies are yet to be done. In this paper, we discuss the molecular structure and vibrational spectra of N-butyl-N-methylpiperidinium bis(trifluromethanesulfonyl) imide, (PIP₁₄NTf₂; where, PIP₁₄ is N-butyl-N-methylpiperidinium and NTf₂ is bis(trifluromethanesulfonyl) imide), obtained with a combined approach of infrared (IR) and Raman spectroscopies in the liquid state and density functional theory (DFT) and Hartree–Fock (H–F) based theoretical calculations. DFT calculations, which are found to produce the most stable geometry compared to other two methods (MP2 and H–F), reproduce the experimental IR and Raman spectra reasonably well. Our findings reveal structural properties that profoundly influence intermolecular interactions and melting point. There exists a large variation in the melting point of the ILs studied. While the bromide salt of the piperidinium derivative (PIP₁₄Br) is solid with very high melting point (241 °C), the corresponding NTf₂ salt is low viscous liquid at room temperature (mp: −25 °C). bmimBr (bmim = 1-butyl-1-methylimidazolium) exhibits a substantially lower melting point of 79 °C than PIP₁₄Br, suggesting that more number of strong classical hydrogen bonding interactions in the latter is primarily responsible for the much higher melting point. In addition, involvement of the alkyl group in PIP₁₄ in H-bonding interaction provides additional rigidity in n-butyl chain which is otherwise absent in bmimBr. Interaction energy for PIP₁₄Br is found to be higher than PIP₁₄NTf₂, showing a positive correlation between interaction energy and melting point. A blue shift in CH stretching wavenumber as evident from IR and Raman spectra of PIP₁₄Br IL is a clear indication of the stronger hydrogen bonding as compared to PIP₁₄NTf₂ IL. Furthermore, we experimentally observe the existence of cisoid–transoid conformational equilibrium of NTf₂⁻ anion in the Raman spectrum of PIP₁₄NTf₂ for the first time and determined that transoid NTf₂⁻ anion to be more stable than the corresponding cisoid conformer by 1.04 kcal/mol using DFT. Examination of various conformational possibilities of the cation shows that the butyl group preferentially exists in gauche conformation.     

Ein- und zweikernige MoII-Phthalocyaninate(2–): Darstellung und Eigenschaften von Bis(cyano)phthalocyaninato(2–)molybdat(II) und Bis(phthalocyaninato(2–)molybdän(II))

Mono- and Dinuclear Mo^II Phthalocyaninates(2–): Syntheses and Properties of Bis(cyano)phthalocyaninato(2–)molybdate(II) and Bis(phthalocyaninato(2–)molybdenum(II)) Blue diamagnetic bis(phthalocyaninato(2–)molybdenum(II)) is synthezied by reduction of oxophthalocyaninato(2–)molybdenum(IV) with boiling triphenylphosphine. The Mo–Mo stretching vibration ist observed in the resonance Raman spectrum at 374 cm^–1. It is chemically inert and dissolves in conc. sulfuric acid without decomposition. It reacts with molten tetra(n-butyl)ammonium cyanide to yield redbrown paramagnetic bis[tetra(n-butyl)ammonium] biscyanophthalocyaninato(2–)molybdate(II) (μ_eff = 3.15 μ_B; S = 1). The complex salt is very instable and demetallizes in solution. In the extraordinary UV-VIS-NIR spectrum an intense trip-triplet transition at 7780 cm^–1 together with a very structured B region between 14000 and 21000 cm^–1 of comparable absorbance is observed.     

Raman spectra of crystalline and molten MgCl2

The Raman active phonon frequencies have been assigned in crystalline magnesium chloride and are found consistent with that expected for the D_3d⁵ space group. Residual lattice bands are observed in the melt, just above the melting point of MgCl₂, which strongly suggests it is structurally similar to the solid layer lattice.     

Bi4B2O9晶体及其熔体结构的高温原位拉曼光谱研究

利用密度泛函理论计算了Bi₄B₂O₉晶体的常温拉曼光谱, 并通过与实验拉曼光谱对比, 对其振动模式进行了归属. 利用高温原位拉曼光谱研究了Bi₄B₂O₉从常温到750 ℃升温过程中微结构的变化. 随着温度的升高, 晶体的平均键长变长, 键角分布变宽, 熔化后晶体中的BiO₄和BiO₅多面体解体, BO₃构型则保持三配位不变. 运用量子化学从头算法模拟了Bi₄B₂O₉的熔体结构并与实验拉曼光谱进行了对比分析, 发现在Bi₄B₂O₉熔体中B原子团簇为孤立的BO₃构型, Bi ³⁺游离于BO₃之间, 并结合未参与形成BO₃的O原子起到平衡电荷的作用.     

Trace Amounts of Aqueous Copper(II) Chloride Complexes in Hypersaline Solutions: Spectrophotometric and Thermodynamic Studies

Knowledge of the thermodynamic properties of aqueous copper(II) chloride complexes is important for understanding and quantitatively modeling trace copper behavior in hydrometallurgical extraction processing. In this paper, UV–Vis spectra data of Cu(II) chloride solutions with various salinities (NaCl, 0–5.57 mol·kg^?1) are collected at 25 °C. The concentration distribution of Cu–Cl species is in good agreement with those calculated by a reaction model (RM). The simple hydrated ion, Cu²⁺, is dominant at low concentration, whereas [CuCl]⁺, [CuCl₂]⁰ and [CuCl₃]^? become increasingly important as the chloride concentration rises. Moreover, the RM calculation suggests the present of a small amount of [CuCl₄]^2?. The de-convoluted molar spectrum of each species is in excellent agreement with our previous theoretical results predicted by time-dependent density functional theory treatment of aqueous Cu-containing systems. The formation constants for these copper chloride complexes have been reported and are to be preferred, except log₁₀ K ₂ ([CuCl₂]⁰).     

Structural, optoelectronic, infrared and Raman spectra of orthorhombic SrSnO3 from DFT calculations

Orthorhombic SrSnO₃ was investigated using density functional theory (DFT) considering both the local density and generalized gradient approximations, LDA and GGA, respectively. The electronic band structure, density of states, complex dielectric function, optical absorption, and the infrared and Raman spectra were computed. Calculated lattice parameters are close to the experimental measurements, and an indirect band gap (2.27 eV) was obtained within the GGA (LDA) level of calculation. Effective masses for holes and electrons were estimated, being very anisotropic in comparison with similar results for orthorhombic CaSnO₃. The complex dielectric function and the optical absorption of SrSnO₃ were shown to be sensitive to the plane of polarization of the incident light. The infrared spectrum between 100 and 600 cm⁻¹ was obtained, with its main peaks being assigned, and a nice agreement between experimental and theoretical peaks of the Raman spectrum of orthorhombic SrSnO₃ was achieved.     

Reaction of 1-chloro-2-phenylethane-2,2-dithiol with divalent metal (Cu, Hg, Pb, Fe, Co, and Ni) salts

Reactions of 1-chloro-2-phenylethane-2,2-dithiol with lead(II) acetate and mercury(II) chloride lead to 1-chloro-2-phenylethane-2,2-dithiolates of lead and mercury. The reactions with copper(II) chloride, iron(II) sulfate hydrate, cobalt (II) chloride hydrate, and nickel(II) acetate give metal-containing compounds C₁₆H₁₈S₄M. The¹H NMR, IR, and ESR spectra of the obtained compounds were recorded; their specific dark electroconductivities and activation energies of dark conductivity were determined, and their film-forming ability was studied. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1224–1226, June, 1997.     

IR and Raman Vibrational Assignments for Metal-free Phthalocyanine from Density Functional B3LYP／6-31G（d） Method

Vibrational (IR and Raman) spectra for the metal-free phthalocyanine (H2Pc) have been comparatively investigated through experimental and theoretical methods. The frequencies and intensities were calculated at density functional B3LYP level using the 6-3 IG(d) basis set. The calculated vibrational frequencies were scaled by the factor 0.9613 and compared with the experimental result. In the IR spectrum, the characteristic IR band at 1008.cm^-1 is interpreted as C-N (pyrrole) in-plane bending vibration, in contrast with the traditional assigned N-H in-plane or out-of-plane bending vibration. The band at 874 cm^-1 is attributed to the isoindole deformation and aza vibration. In the Raman spectrum, the bands at 540, 566, 1310, 1340, 1425, 1448 and 1618 cm^-1 are also re-interpreted. Assignments of vibrational bands in the IR and Raman spectra are given based on density functional calculations for the first time. The present work provides valuable information to the traditional empirical assignment and will be helpful for further investigation of the vibration spectra of phthalocyanine analogues and their metal complexes.     

DFT Study on Methanofullerene Derivative [6,6]-Phenyl-C61 Butyric Acid Methyl Ester

Density functional theory (DFT) and time-dependent density functional theory (TDDFT) with hybrid functional B3LYP were used to investigate several physical and chemical properties of [6,6]-phenyl-C₆₁ butyric acid methyl ester (PCBM), including the geometry, electron structure, charge population, bond properties, as well as IR, Raman and electronic absorption spectra. The analysis of the natural bond orbital (NBO) suggested that there were about 0.11 electrons transferred from moiety phenyl and butyric acid methyl ester group of PCBM to fullerene cage. The strongest IR and Raman peaks came from different modes with the frequencies of 1773 and 1492 cm⁻¹, respectively. The calculated isotropic polarizability, polarizability anisotropy invariant, and hyperpolarizability were 577.7, 96.9, and −22.8 a.u., respectively. Based on TDDFT, the electronic absorption spectra of PCBM were calculated and analyzed. The calculated absorption band near 349 nm agreed well with the experimental measurement.     

Cobalt(II) chloride complexes in molten acetamide

The absorption spectra of Co(II) chloride species were studied in molten acetamide containing variable concentration of chloride ligand, in the wavelength range 400–800 nm, at 90°C. The stepwise formation of CoCl_j^(2-j) complexes (J = 1–4) was observed. Addition of chloride ligand (up to 4 molar) dramatically changed Co(II) absorption spectra due to change in co-ordination from octahedral through a severely distorted octahedral to tetrahedral co-ordination. Overall equilibrium constants β_j and consecutive stability constants K_j(j = 1–4) were calculated using SPELMA program for simultaneous computation of equilibrium constants and molar absorption coefficients for each complex species. Distribution of the Co(II) species was also calculated in the studied ligand concentration range.     

Oxadiazole‐2‐thiol Adsorption on Gold Nanorods: A Joint Theoretical and Experimental Study by Using SERS,XPS, and DFT

The chemisorption of 1,3,4‐oxadiazole‐2‐thiol (ODT) on gold nanorods has been investigated by using surface‐enhanced Raman spectroscopy (SERS) and density functional theory (DFT). Although most of the SERS spectra have remarkable similarity to the normal Raman spectra of the pure analyte, the adsorption of ODT on a gold surface leads to a drastic change in its Raman spectrum and distinct vibrational features are obtained with gold nanorods and spherical nanoparticles. Simulated Raman spectra for hybrid systems that consist of an oxadiazole moiety coordinated to a Au₂₀ gold cluster provided valuable information about the coordination mode and enabled us to assign vibration modes.     

Phonon spectra and phonon-dependent properties of AgSO4, an unusual sulfate of divalent silver

Phonon spectra of recently synthesized Ag(II)SO₄ have been measured using infrared absorption and Raman scattering spectroscopy, and theoretically predicted using density functional theory calculations. Excellent agreement between experimental and theoretical results with correlation coefficient of 1.05 allowed for full assignment of the experimentally observed vibrational bands, as well as calculation of standard vibrational entropy of AgSO₄ (118.2 J mol⁻¹ K⁻¹), vibrational heat capacity at constant volume (99.1 J mol⁻¹ K⁻¹), zero-point energy (48.3 kJ mol⁻¹). The experimental cut-off frequency of the phonon spectrum equals 1116 cm⁻¹ which translates to the Debye temperature of 1606 K. High frequencies of S–O stretching modes render sulfate connections of Ag(II) attractive precursors of high-T_C superconductors.     

Solid-state characterization of chloroprocaine hydrochloride

Summary Chloroprocaine hydrochloride (2-CPCHC) is a local anaesthetic agent of the ester type preferentially used for epidural anaesthesia. The compound, official in the USP, was found to exist in two polymorphic crystal forms which have been characterized by thermomicroscopy, differential scanning calorimetry (DSC), pycnometry, FTIR-, FT-Raman-spectroscopy as well as X-ray powder diffractometry. Based on these data the relative thermodynamic stability of the two forms was determined and is represented in a semi-schematic energy/temperature diagram. Mod. I° is the thermodynamically stable form at room temperature. This form is present in commercial products and can be crystallized from ethanol. Mod. II can be obtained by annealing the supercooled melt in a temperature range between 100 and 130°C. Upon heating mod. II exhibits an exothermic phase transition (Δ_trsH_II-I: -5.0±0.5 kJ mol^-1) at about 134°C to mod. I° (melting point 175°C, Δ_fusH_I: 46.6±0.6 kJ mol^-1). The exothermic transformation of mod. II to mod. I° confirms that mod. I° is thermodynamically stable in the entire temperature range (heat of transition rule) whereas mod. II is monotropically related to mod. I°, i.e. is metastable at all temperatures below its melting point. Mod. II is of low kinetic stability at room temperature and the transformation to mod. I° starts within a few minutes at room temperature. The N-H band in the infrared spectrum of mod. I° (3433 cm^-1) lies at significantly higher wavenumbers than that of mod. II (3413 cm^-1) indicating differences in the hydrogen bonding arrangement. Furthermore, the measured density of mod. I° is lower than the density of mod. II and thus both, the IR- and the density-rule are violated in this polymorphic system.     

Ruthenium(II)-Phthalocyanine: Darstellung und Eigenschaften von Di(halogeno)phthalocyaninatoruthenat(II)

Ruthenium(II) Phthalocyanines: Preparation and Properties of Di(halo)phthalocyaninatoruthenate(II) [Ru(Py)₂Pc^2?] reacts with molten (ⁿBu₄N)X forming stable, green (ⁿBu₄N)₂[Ru(X)₂Pc^2?] (X = Cl, Br). The cyclovoltammogram shows a quasireversible redoxprocess for the metal oxidation at E_1/2(I) = ?0.02 V (X = Cl) resp. 0.05 V (X = Br) and for the first ringoxidation at E_1/2(II) = 0.70 V. The typical π-π*-transitions (B < Q < N) of the phthalocyanine dianion (Pc^2?) are observed in the uv-vis spectrum. With respect to Ru^III phthalocyanines B is shifted significantly to higher, Q, N to lower energy. The strong extra-band at 24.2 kK is diagnostic for these Ru^II phthalocyanines. The vibrational spectra are typical for the Pc^2? ligand with D_4h symmetry, too, and bands at 513, 909, 1 171 und 1 329 cm^?1 in the m.i.r. spectrum are specific for hexa-coordinated low spin Ru^II. In the Raman spectrum with excitation at ～480 nm the intensity of the totally symmetrical Ru? X stretching vibration at 266 cm^?1 (X = Cl) resp. 168 cm^?1 (X = Br) together with a progression of up to three overtones is selectively resonance Raman enhanced. The asymmetrical Ru? X stretching vibration is observed in the f.i.r. spectrum at 272 cm^?1 (X = Cl) resp. 215 cm^?1 (X = Br).