Ab initio study of spectroscopic properties of CuAr, CuAr(+) and CuAr(-)

The spectroscopic properties of CuAr, CuAr(+) and CuAr(-) have been studied in detail using ab initio MP2, CCSD and CCSD(T) methods. The effect of basis set on spectroscopic properties of these molecular systems has also been investigated. Among these molecules, CuAr(+) is found to be more strongly bound than CuAr and CuAr(-). The spectroscopic properties of CuAr and CuAr(-) are calculated in Lennard-Jones potential and the spectroscopic properties of CuAr(+) are calculated in Morse potential. Most of the spectroscopic constants of CuAr, CuAr(+) and all the spectroscopic constants of CuAr(-) are first reported. Our calculated bond length, harmonic frequency and dissociation energy of CuAr and CuAr(+) agree very well with the existing theoretical results.     

Electrochemical, pulsed-field-gradient spin-echo NMR spectroscopic, and ESR spectroscopic study of the diffusivity of molecular probes inside gel-type cross-linked polymers

The permeability of five gel-type synthetic resins, obtained by polymerization of 1-vinylpyrrolidin-2-one cross-linked with N,N'-methylenebisacrylamide (1, 2, 3, 4, and 5 wt %) and swollen by N,N-dimethylformamide (DMF), has been analyzed. The diffusion of 2,2,6,6-tetramethyl-4-oxo-1-piperidinyloxyl (TEMPONE) was studied by ultramicroelectrode voltammetry. Similar measurements were performed for solutions of non-cross-linked poly(vinylpyrrolidone) in DMF. To provide information on the rotational mobility of TEMPONE and the translational mobility of DMF, electron spin resonance (ESR) spectroscopic and pulsed-field-gradient spin-echo nuclear magnetic resonance (PGSE-NMR) spectroscopic experiments, respectively, were carried out. Comparative analysis of the results obtained by electrochemical, ESR spectroscopic, and PGSE-NMR spectroscopic measurements showed that diffusivity inside the polymer framework is significantly affected by the extent of cross-linking, the size of the diffusing probe, and the presence of electrolytes.     

High-throughput spectroscopic viscosity measurement of nanocomposite sols with ETC-effect

A high-throughput method for viscosity measurement was developed and tested for nanocomposite sols with an easy-to-clean (ETC) effect. The method is based on doping of sols with viscosity sensitive fluorescent dye 4,4′-bis-(2-benzoxazolyl)-stilbene (BOS) and acquisition of fluorescence intensity data. The spectroscopic data were correlated with viscosity data derived from mechanical measurements with a rotational viscometer and show an exponential correlation of both mechanical and spectroscopic measurement methods in the relevant data space of 3–5 mPa·s. For application of the spectroscopic viscosity measurement as a high-throughput assay doping of sols with BOS slurry was carried out with an automated liquid handling system, and spectroscopic measurements were performed with a fluorescence microplate reader.     

Effect of isomer geometry on the steady-state absorption spectra and femtosecond time-resolved dynamics of carotenoids

Steady-state absorption and femtosecond time-resolved optical spectroscopic studies have been carried out on all-trans-beta-carotene, 15,15'-cis-beta-carotene, all-trans-spheroidene, and 13,14-locked-cis-spheroidene. We examine in detail the effect of isomer geometry on the spectroscopic properties and photophysics of the low-lying S(1) (2(1)A(g)(-)) and S(2) (1(1)B(u)(+)) excited states of these molecules. The experiments on 13,14-locked-cis-spheroidene, a molecule incapable of undergoing cis-to-trans isomerization, provide a unique opportunity to examine the role of isomer geometry in controlling excited-state deactivation of carotenoids. The kinetic results have been obtained using both single wavelength transient absorption measurements and global fitting procedures. The overall scheme for the deactivation of these molecules after S(0) --> S(2) photon absorption is decay of S(2) to a vibrationally hot S(1) state, followed by vibrational relaxation within S(1), and finally, S(1) --> S(0) internal conversion back to the ground state. Changes in isomer geometry are shown to lead to small but noticeable alterations in the spectroscopic and kinetic behavior of the molecules. The effects are interpreted in terms of minor alterations in excited-state energy and vibrational coupling upon isomerization that bring about changes in the spectroscopic and kinetic behavior of this biologically important class of pigments.     

Potential energy curves and calculations of spectroscopic constants for the ground state of AlC and AlN

The density functional theory method with B3LYP/6-311++G(df,pd), B3LYP/6-311++G(2df, 2pd), and B3LYP/6-311++G(3df,3pd) basis sets is used to compute the geometrics and single point energy of aluminum carbide (AlC) and aluminium nitride (AlN) in their ground state. The Level 8.0 program is used to calculate spectroscopic constants and fit the energy potential curves. The effect of a basis set on the spectroscopic constants is discussed. The results show that the calculated potential curve matches well with the Level 8.0 fitting curve, and the calculated values of spectroscopic constants become more reliable with the improvement of the quality of basis sets. The spectroscopic constants are in good agreement with the existing experimental and theoretical values. For the first time, the reliable anharmonicity constant data of AlC are reported, which agrees so well with the experimental value.     

1H and 13 C spectral assignments of 7beta-(cinnamoyl-substituted)amino-3-acetoxymethyl-cephalosporins

The (1)H and (13)C spectroscopic data for 7beta-(cinnamoyl-substituted)amino-3-acetoxymethyl-cephalosporins were fully assigned by a combination of one- and two-dimensional experiments. Substitution on the aromatic ring and on the double-bond alpha-position of the cinnamoyl moiety has little influence on the spectroscopic properties of the 7beta-aminocephalosporanic acid parent moiety.     

Calculation of equilibrium constants from multiwavelength spectroscopic data--II: SPECFIT: two user-friendly programs in basic and standard FORTRAN 77

A new program (SPECFIT), written in HP BASIC or FORTRAN 77, for the calculation of stability constants from spectroscopic data, is presented. Stability constants have been successfully calculated from multiwavelength spectrophotometric and EPR data, but the program can be equally well applied to the numerical treatment of other spectroscopic measurements. The special features included in SPECFIT to improve convergence, increase numerical reliability, and minimize memory as well as computing time requirements, include (i) elimination of the linear parameters (i.e., molar absorptivities), (ii) the use of analytical instead of numerical derivatives and (iii) factor analysis. Calculation of stability constants from spectroscopic data is then as straightforward as from potentiometric titration curves and gives results of analogous reproducibility. The spectroscopic method has proved, however, to be superior in discrimination between chemical models.     

四取代羧基酞菁锌与白蛋白共价结合物的制备与光谱性质

通过成酰胺键的方式制备了一系列含羧基酞菁和白蛋白(牛血清白蛋白(BSA),人血清白蛋白(HSA))之间的共价结合物,所涉及到的酞菁分别是α-四(4-羧基苯氧基)酞菁锌(1)和α-四[4-(2-羧基乙基)苯氧基]酞菁锌(3),以及它们相应的β位四取代酞菁锌(化合物2和4).比较了游离酞菁以及它们的白蛋白结合物在磷酸盐缓冲溶液(PBS)中的光谱性质.结果表明,当酞菁被共价固定于白蛋白大分子上之后,展现出比游离酞菁更明显的单体特征吸收,而且结合物中的酞菁光谱特征不受体系pH值变化的影响.羧基在酞菁环上的取代位置,对酞菁与白蛋白结合前后的光谱转变幅度有影响,α位取代比β位取代更有利于光谱的变化.化合物1和3的白蛋白共价结合物在PBS溶液中甚至呈现出单体形式为主的光谱特征,Q带最大吸收波长分别位于697和706nm附近.     

A Review of Spectroscopic and Biophysical‐Chemical Studies of the Complex of Cyclobutane Pyrimidine Dimer Photolyase and Cryptochrome DASH with Substrate DNA

Cyclobutane pyrimidine dimer (CPD) photolyase (PL) is a structure‐specific DNA repair enzyme that uses blue light to repair CPD on DNA. Cryptochrome (CRY) DASH enzymes use blue light for the repair of CPD lesions on single‐stranded (ss) DNA, although some may also repair these lesions on double‐stranded (ds) DNA. In addition, CRY DASH may be involved in blue light signaling, similar to cryptochromes. The focus of this review is on spectroscopic and biophysical‐chemical experiments of the enzyme–substrate complex that have contributed to a more detailed understanding of all the aspects of the CPD repair mechanism of CPD photolyase and CRY DASH. This will be performed in the backdrop of the available X‐ray crystal structures of these enzymes bound to a CPD‐like lesion. These structures helped to confirm conclusions that were drawn earlier from spectroscopic and biophysical‐chemical experiments, and they have a critical function as a framework to design new experiments and to interpret new experimental data. This review will show the important synergy between X‐ray crystallography and spectroscopic/biophysical‐chemical investigations that is essential to obtain a sufficiently detailed picture of the overall mechanism of CPD photolyases and CRY DASH proteins.     

New cholestane glycosides from the leaves of Cordyline terminalis

Four new cholestane glycosides (1-4) were isolated from the leaves of Cordyline terminalis (Agavaceae). The structures of the new compounds were determined on the basis of spectroscopic analysis and a few chemical transformations followed by chromatographic and spectroscopic analyses.     

FTIR and circular dichroism spectroscopic study of interaction of 5-fluorouracil with DNA

5-Fluorouracil (5FU) is an anticancer chemotherapeutic drug which exerts cytotoxic effect by inhibiting cellular DNA replication. In the present study, we explore the binding of 5FU with DNA and resulting structural and conformational changes on DNA duplex. UV-visible, Fourier transform infrared (FTIR) and circular dichroism (CD) spectroscopic techniques were employed to explore these interactions. A constant concentration of calf thymus DNA was incubated with varying concentrations of 5FU. UV-visible and FTIR spectroscopic results revealed that intercalation is the primary mode of interaction between 5FU and nitrogenous bases of the nucleic acid. The binding constant was found to be 9.7×10(4); which is indicative of moderate type of interaction between 5FU and DNA duplex. It was also observed that 5FU intercalates slightly more between AT base pairs compared to GC pairs. FTIR and circular dichroism spectroscopic results revealed that 5FU disturbs native B-conformation of DNA though, DNA remains in its B conformation even at higher concentrations of 5FU.     

A simulation of the photoelectron spectrum of pyrazolide

Building on previous theoretical and spectroscopic studies of the pyrazolyl radical, a new three-state quasidiabatic Hamiltonian is reported which reproduces not only the equilibrium geometries and harmonic frequencies of the nominal X (2)A(2) state and low-lying A (2)B(1) excited state, but also the minimum energy points on the lowest two-state (X (2)A(2), A (2)B(1)) and three-state (X (2)A(2), A (2)B(1), B (2)B(2)) seams of conical intersection. The three-state Hamiltonian includes all terms through second order in both the diagonal and off-diagonal blocks. Its construction is accomplished in two steps. First, a nascent Hamiltonian, centered at the lowest energy two-state conical intersection, is determined using ab initio gradients and derivative couplings. Then, the nascent Hamiltonian is improved by optimizing selected contributions to the second-order coefficients to better reproduce relevant minima and harmonic frequencies. This Hamiltonian is then expressed in a basis tailored to describe the neutral states of interest under the multimode vibronic coupling approximation. The vibronic Hamiltonian is diagonalized to obtain negative ion photoelectron spectra for pyrazolide-h(3) and the completely deuterated analog pyrazolide-d(3). The resultant spectra, determined employing vibronic Hamiltonians as large as 500 million terms, compare favorably to recent theoretical and spectroscopic results for pyrazolyl-d(3) and to spectroscopic results for pyrazolyl-h(3), for which no reliable simulations had been available.     

Synthesis,Spectroscopic, and Structural Properties of Organogermanyl(IV) Complexes of Pyridine Oximes

Abstract

Reactions of triorganogermanyl(IV) chlorides and diorganogermanyl(IV) dichlorides with sodium salts of pyridine-2-carbaldehyde oxime and 2-acetylpyridine oxime, respectively, in 1:1 and 1:2 molar ratio produced organogermanyl(IV) oximates. All the derivatives have been characterized by spectroscopic techniques and tetrahedral structures have been proposed on the basis of spectroscopic data and molecular orbital calculations.     

Phytoecdysteroids from the roots of Achyranthes bidentata Blume

Two new phytoecdysteroids, (25S)-20,22-O-(R-ethylidene)inokosterone and 20,22-O-(R-3-methoxycarbonyl)propylidene-20-hydroxyecdysone, together with six known phytoecdysteroids 3-8 were isolated from the roots of Achyranthes bidentata Blume. The new structures were established on the basis of spectroscopic studies and chemical evidences. The absolute configuration at C-25 in the structure of known compound 3 was determined by chemical and spectroscopic means.     

Chemometric Tools to Point Out Benchmarks and Chromophores in Pigments through Spectroscopic Data Analyses

Spectral preprocessing data and chemometric tools are analytical methods widely applied in several scientific contexts i.e., in archaeometric applications. A systematic classification of natural powdered pigments of organic and inorganic nature through Principal Component Analysis with a multi-instruments spectroscopic study is presented here. The methodology allows the access to elementary and molecular unique benchmarks to guide and speed up the identification of an unknown pigment and its recipe. This study is conducted on a set of 48 powdered pigments and tested on a real-case sample from the wall painting in S. Maria Delle Palate di Tusa (Messina, Italy). Four spectroscopic techniques (X-ray Fluorescence, Raman, Attenuated Total Reflectance and Total Reflectance Infrared Spectroscopies) and six different spectrometers are tested to evaluate the impact of different setups. The novelty of the work is to use a systematic approach on this initial dataset using the entire spectroscopic energy range without any windows selection to solve problems linked with the manipulation of large analytes/materials to find an indistinct property of one or more spectral bands opening new frontiers in the dataset spectroscopic analyses.     

Reversible enolization of beta-amino carboxamides by lithium hexamethyldisilazide

The enolization of beta-amino carboxamides by lithium hexamethyldisilazide (LiHMDS) in THF/toluene and subsequent diastereoselective alkylation with CH(3)I are reported. In situ IR spectroscopic studies reveal that beta-amino carboxamides coordinate to LiHMDS at -78 degrees C before enolization. Comparison with structurally similar carboxamides suggests that the beta-amino group promotes the enolization. IR spectroscopic studies also show that the enolization is reversible. Efficient trapping of the enolate by CH(3)I affords full conversion to products. (6)Li and (15)N NMR spectroscopic studies reveal that lithium enolate-LiHMDS mixed dimers and trimers as well as a homoaggregated enolate are formed during the reaction. At ambient temperature, racemization of the beta-position through a putative reversible Michael addition was observed.     

溶液pH对硫堇与DNA相互作用方式的影响

用电化学和光谱方法研究了溶液pH对硫堇(TH)与小牛胸腺脱氧核糖核酸(CT-DNA)相互作用方式的影响.电化学测量结果表明，在pH 7.2的磷酸盐缓冲溶液中, TH与CT-DNA之间的作用方式以嵌入结合为主，在pH 6.5的磷酸盐缓冲溶液中， TH与CT-DNA之间的作用方式既存在嵌入结合也存在静电作用.荧光光谱测量结果表明，TH与DNA结合后其荧光发生猝灭，通过Stern-Volmer方程计算得到pH 6.5时TH-DNA体系的猝灭常数高于pH 7.2时的值，表明在pH 6.5的溶液中两者相互作用更强.圆二色谱(CD)实验结果也证实了这一结论.     

Vibrational spectroscopic encoding of polystyrene-based resin beads: converting the encoding peaks into barcodes

A detailed approach is described for the vibrational spectroscopic encoding of polystyrene-based resin beads by converting the infrared absorption peaks suitable for encoding (encoding peaks) into barcodes. Based on combining the FT-IR measurements and the quantum-chemical computations, the vibrational characteristics of p-tert-butylstyrene monomer, polystyrene and poly(p-tert-butylstyrene) resin beads are analyzed, which are helpful for the selection of encoding peaks. The vibrational spectroscopic encoding of polystyrene-based resin beads could be obtained by converting the wavenumber, intensity and full width at half maximum (FWHM) of the encoding peaks into barcodes automatically through a computer program designed in our laboratory.     

The B 1sigma+ and X 1sigma+ electronic states of hydrogen fluoride: a direct potential fit analysis

All literature pure rotational and vibration-rotational spectroscopic data on the ground X (1)Sigma(+) electronic state of HF and DF, together with the entire set of spectroscopic line positions from analyses of the B (1)Sigma(+) --> X (1)Sigma(+) emission band systems of HF and DF, have been used in a global least-squares fit to the radial Hamiltonian operators, in compact analytic form, for both electronic states. With a data set consisting of 6157 spectroscopic line positions, the reduced standard deviation of the fit was sigma = 1.028. Sets of quantum mechanically significant rotational and centrifugal distortion constants were calculated for both electronic states using Rayleigh-Schr?dinger perturbation theory.     

A Perspective on Studying Electronic Structure of Batteries through Soft X-ray Spectroscopy

Understanding electronic structure is crucial to enhance the battery performance. Soft X-ray spectroscopy(SXS) is one of the most effective methods to provide direct probe of electronic states. Here, spectroscopic measurements of transition metal 3 d and oxygen 2 p states are simply reviewed. Then, we mainly focus on the perspective of the development direction of modern SXS techniques. Although the true power of recently developed high efficiency mapping of resonant inelastic X-ray scattering(m RIXS) has been apparent for materials and chemistry studies, great challenges remain for mRIXS spectroscopic interpretation, and the understanding of the battery materials on novel redox activities remains elusive.