2-氯-5-三氟甲基苯胺水杨醛Schiff碱的结构及光谱性质研究

Schiff碱及其络合物的合成一直是研究的热点,其在药学、催化等领域有广泛的应用。实验以2-氯-5-三氟甲基苯胺、水杨醛为原料,合成2-氯-5-三氟甲基苯胺水杨醛Schiff碱,测定了Schiff碱的红外光谱和氢谱。利用密度泛函理论（DFT）B3LYP方法在6-311++G**基组上对合成的Schiff碱化合物进行了几何构型的优化和红外光谱的计算,得到了分子的优势构象、频率值及对应的红外强度,并比较了实验和理论计算的光谱数据,对分子的振动模式进行了全面的光谱归属,发现理论计算与实验测试结果吻合的较好。     

2-氯-5-三氟甲基苯胺水杨醛Schiff碱的结构及光谱性质研究

实验以2-氯-5-三氟甲基苯胺、水杨醛为原料,合成2-氯-5-三氟甲基苯胺水杨醛Schiff碱,测定了Schiff碱的红外光谱和氢谱.利用密度泛函理论(DFT)B3LYP方法在6-311++G**基组上对合成的Schiff碱化合物进行了几何构型的优化和红外光谱的计算,得到了分子的优势构象、频率值及对应的红外强度,并比较了实验和理论计算的光谱数据,对分子的振动模式进行了全面的光谱归属,发现理论计算与实验测试结果吻合的较好.     

2-(2-羟基苯亚甲基)胺基-3-氰基吡啶的结构和光谱性质

实验以水杨醛、2-氨基-3-氰基吡啶为原料,合成了Schiff碱2-(2-羟基苯亚甲基)胺基-3-氰基吡啶并测定了Schiff碱的红外和拉曼光谱.利用密度泛函理论B3LYP方法在6-311++G~(**)基组上对合成的Schiff碱进行了几何构型的优化、红外光谱及拉曼光谱的计算,得到了分子的优势构象的结构参数、频率值及对应的强度.对实验和理论计算的光谱数据进行了对比,对分子的振动模式进行了全面归属,结果表明理论计算与实验测试数据相吻合.此外,还计算了其前线分子轨道,得到了HOMO-LUMO能隙相关的数据,为Schiff碱类化合物的结构分析和光谱检测技术提供了参考依据.     

2-三氟甲基吡啶的合成与光谱表征

以2-氯基吡啶为原料,合成2-溴吡啶(收率68%)和2-碘吡啶(收率56%);2-溴吡啶和2-碘吡啶与三氟乙酸钾反应,得2-三氟甲基吡啶(收率56%-72%).通过NMR和元素分析对产物的结构进行了表征.该合成路线的优点是原料易得,反应条件温和,收率较高,总收率为38%-42%.     

5-溴水杨醛缩硫脲Schiff碱及其铜（Ⅱ）配合物的合成与表征

以水杨醛为原料制备了5-溴水杨醛缩硫脲配体及其与铜配合物。并通过红外光谱、紫外光谱、差热-热重、摩尔电导率等方法对配体及配合物的组成和结构进行了测试表征。     

外电场下4-氯-2-三氟甲基噻吩并[3,2-D]嘧啶分子的结构和光谱

4-氯-2-三氟甲基噻吩并[3,2-D]嘧啶(4-chloro-2-(trifluoromethyl)thieno[3,2-d] pyrimidine, CTTP)分子具有很高的生物和医学活性,是重要的医药中间体,因此了解外电场下对其结构和光谱的影响具有重要意义。采用密度泛函理论B3LYP方法和def2-tzvp基组,优化计算了CTTP分子在不同外电场作用下的稳定结构;然后从外电场对其结构、原子电荷分布、前线轨道、静电势、红外和拉曼光谱等方面的影响进行了分析。结果显示：随着外电场强度增加,分子结构和原子电荷分布发生改变,分子极性增强,能隙降低,化学反应活性增强,静电势分布极值点发生了明显改变,红外和拉曼在不同区域内发生振动斯塔克效应,既有蓝移又有红移,峰的强度也出现了复杂的变化。     

5-溴水杨醛缩盐酸氨基脲稀土配合物的合成及光谱研究

由5-溴水杨醛与盐酸氨基脲缩合形成了Schiff碱配体,将其与稀土金属Ce(Ⅲ)、La(Ⅲ)作用合成了两种新型配合物,并通过红外光谱、紫外光谱、元素分析、热重-差热及摩尔电导率等方法,对化合物的组成与结构进行了表征.     

2-巯基-5-甲基苯并咪唑振动光谱的密度泛函理论研究

本文选用密度泛函理论中的B3LYP杂化泛函,在B3LYP/6-311++G(d, p)水平下,优化了2-巯基-5-甲基苯并咪唑分子(MMBI)的结构,优化结果表明,2-巯基-5-甲苯并咪唑分子是一个近平面结构.通过频率计算,获得了2-巯基-5-甲基苯并咪唑分子(MMBI)的拉曼光谱,并和实验获得的拉曼光谱图进行了对比,实验和理论计算获得的拉曼光谱图基本上是一致的,表明本文选取的DFT理论计算方法是可靠的.结合VEDA4软件对2-巯基-5-甲基苯并咪唑分子的拉曼谱带简正振动模式进行了指认.此外,分析并讨论了2-巯基-5-甲基苯并咪唑分子(MMBI)前线轨道,HOMO和LUMO轨道能级差为4.51 eV,电子有从HOMO跃迁到LUMO的趋势.采用含时密度泛函理论(time dependent density functional theory, TDDFT)对2-巯基-5-甲基苯并咪唑分子(MMBI)的激发态进行了计算分析,计算结果表明乙醇溶剂中2-巯基-5-甲基苯并咪唑分子(MMBI)理论计算的吸收波长为226 nm, 288 nm.对研究2-巯基-5-甲基苯并咪唑分子的性质,提供了理论...     

水杨醛缩对乙酰基苯胺希夫碱的合成及其荧光性质的理论研究

以水杨醛和对乙酰基苯胺为原料,首次采用绿色环保的室温固相反应方法制备了水杨醛缩对乙酰基苯胺希夫碱,用元素分析和核磁共振氢谱对产物进行了表征。测定了产物的紫外光谱、荧光光谱和相对荧光量子效率,发现该化合物具有较强的荧光性质。利用密度泛函理论(density functional theory, DFT)方法,在B3LYP/6-311G基组水平上优化了该化合物的基态分子构型。采用相同的方法和基组计算了标题化合物的振动频率,频率数据中没有虚频,即该优化构型是稳定的。分析理论计算结果发现：标题分子具有较强的芳香性和较大共轭体系。在基态优化结构的基础上应用含时密度泛函理论(TD-DFT),在B3LYP/6-31G水平上计算并研究了此化合物的吸收光谱。用单激发组态相互作用(CIS)方法优化了标题分子的激发态构型,并在此基础上用TD-DFT//B3LYP/6-31G方法计算了这种化合物的荧光发射光谱。将理论计算的光谱性质与实验的光谱数据相比较发现二者吻合较好。分析探讨了化合物分子的结构与其荧光性质之间的关系,为进一步寻找具有荧光性质的化合物提供了理论指导。     

光致变色Schiff碱N,N’-双(水杨醛缩)-1,2-环己二胺的荧光光谱

用稳态和时间分辨荧光光谱研究了Ｎ,Ｎ’ 双水杨醛缩 １,２ 环己二胺（Ｎ,Ｎ’ ｂｉｓ（ｓａｌｉ ｃｙｌｉｄｅｎｅ） １,２ ｃｙｃｌｏｈｅｘａｎｅｄｉａｍｉｎｅ,ＢＳＣ）在固态和四氯化碳、氯仿溶液中的光致变色行为。发现经过光照,ＢＳＣ的荧光光谱发生了明显、快速的改变,并且光致变色过程可重复进行。     

Copper(II) and nickel(II) complexes of tetradentate Schiff base ligand: UV-Vis and FT-IR spectra and DFT calculation of electronic,vibrational and nonlinear optical properties

The experimental fourier transform infrared (FT-IR) and ultraviolet-visible (UV-Vis) spectra of copper(II) and nickel(II) complexes of the deprotonated tetradentate Schiff base ligand N,N′-bis(2-hydroxybenzylidene)-2,2-dimethyl-1,3-propanediamine (H₂L) are compared with their corresponding theoretical ones. The applied theoretical method is based on the density functional theory and time-dependent density functional theory at the UPBE0/PBE0 levels using Def2-TZVP basis set. The computational optimised geometric parameters of the complexes are in good agreement with their corresponding experimental data. The FT-IR and UV-Vis spectra of the complexes were reproduced on the basis of their optimised structures. The vibrational assignments of some fundamental modes of the complexes are performed. The highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) energies are calculated. The analyses of the calculated electronic absorption spectra of the complexes are carried out to elucidate the electronic transitions assignments and their characters. Second-order nonlinear optical property of the complexes is evaluated by the above-mentioned theoretical method that implies much greater values for the complexes in comparison with the corresponding value of urea.     

Synthesis,tautomeric stability,spectroscopy and computational study of a potential molecular switch of (Z)-4-(phenylamino)pent-3-en-2-one

The (Z)-4-(phenylamino) pent-3-en-2-one (PAPO) was synthesised applying carbon-based solid acid and described by experimental techniques. Calculated results reveal that its keto-amine form is more stable than its enol-imine form. A relaxed potential energy surface scan has been accomplished based on the optimised geometry of NH tautomeric form to depict the potential energy barrier related to intramolecular proton transfer. The spectroscopic results and theoretical calculations demonstrate that the intramolecular hydrogen bonding strength of PAPO is stronger than that in 4-amino-3-penten-2-one)APO(. In addition, molecular electrostatic potential, total and partial density of stats (TDOS, PDOS) and non-linear optical properties of the compound were studied using same theoretical calculations. Our calculations show that the title molecule has the potential to be used as molecular switch.     

Fluorescence Characteristics of Schiff Bases Derived from Amino- and Aminoalkylpyridines

The fluorescence characteristics of the Schiff bases 2-(3-pyridylmethyliminornethyl)phenol (1), 2-(2 pyridyliminomethyl)phenol (2), N.N-bis(salicylidene)-2,3-pyridinediamine (3), N,N'-bis(salicylidene)-2,6-pyridinediamine (4) and 2-(2-amino-4-methoxymethyl-6-methyl-3-pyridylmethyliminomethyl)phenol (5) were studied in various solvents at different pH values. Corresponding quantum efficiencies were determined. Compound 1, which showed a tendency towards tautomeric mterconversion to ketoamine in polar protic solvents, was not fluorescent at pH < 8. The fluorescence of other compounds was very sensitive to solvent polarity and the pH of the medium. Compounds 2-4, preferably present as enolimines in all solvents, were not fluorescent in non-polar and moderately polar solvents, whereas weak emission was observed in polar solvents, like methanol, dimethylformamide and dioxane/water 1/1 (0.001 < Q < 0.072). A significant increase in Stokes shifts and in quantum efficiencies was noted as a result of increasing polarity of dioxane/water mixtures, indicating specific interactions with polar water molecules. The emission was promoted at acidic pH values where a pyridinium cation was formed (0.061 < Q < 0.519, in dioxane/water 1/1 at pH 3.4). Compound 5, which was a tautomeric mixture of enoiimine and cyclic diamine in all solvents, was fluorescent in polar as well as in non-polar media. The quantum efficiency varied dependent on the solvent and pH (0.023 <Q< 0.435). The cyclic diamine, i. e. the more rigid structure was supposed to be responsible for the fluorescence in non-polar and aprotic solvents as well as at neutral, and weakly basic pH values.     

A first-principle study of Os-based compounds: Electronic structure and vibrational properties

The electronic structure, elastic, and phonon properties of OsM (M=Hf, Ti, Y and Zr) compounds are studied using first-principles calculations. Elastic constants of OsY and specific heat capacity of OsM (M=Hf, Ti, Y, and Zr) are reported for the first time. The predicted equilibrium lattice constants are in excellent agreement with experiment. The calculated values of bulk moduli are considerably high but are much smaller than that of Osmium, which is around 400 GPa. The phase stability of the OsM (M=Hf, Ti, Y and Zr) compounds were studied by DOS calculations and the results suggest that OsY is unstable in the B2 phase. The brittleness and ductility properties of OsM (M=Hf, Ti, Y and Zr) are determined. OsM (M=Hf, Ti, Y and Zr) compounds are predicted to be ductile materials. The electronic structure and phonon frequency curves of OsM (M=Hf, Ti, Y and Zr) compounds are obtained. The position of Fermi level of these systems was calculated and discussed in terms of the pseudo gaps. The finite and small DOS at the Fermi level 0.335, 0.375, 1.063, and 0.383 electrons/eV for OsHf, OsTi, OsY, and OsZr, respectively, suggest that OsM (M=Hf, Ti, Y and Zr) compounds are weak metals.     

Conformational stability and vibrational study of phenylacetyl chloride

The Fourier transform infrared spectroscopy and Fourier transform Raman spectra of phenylacetyl chloride were recorded and analyzed in the range 3500–400 and 3500–200 cm^?1 at room temperature, respectively. In order to obtain the structural information and conformational stabilities, a potential energy surface scan for internal rotation was carried out at the B3LYP/6‐31G(d) level. The potential energy surface reveals that the title compound has two minimal conformers (A and B). The optimized geometries, structural parameters, stabilities, energies, thermodynamic parameters, vibrational wavenumbers, infrared intensities, and Raman activities for the two conformers (A and B) have been obtained by employing B3LYP and MP2 calculations with 6‐311++G (d, p) basis sets. The conformational energy difference between A and B is very small, indicating that the B conformer coexists with the A conformer. The detailed vibrational assignments of vibrational spectra of each conformer have been made on the basis of the potential energy distributions analysis. The highest occupied molecular orbital –lowest unoccupied molecular orbital energy gap and molecular electrostatic potential of the two conformers have been also calculated for comparison of their chemical activities. Copyright © 2015 John Wiley & Sons, Ltd.     

Molecular structure,spectroscopic (FT-IR and UV-Vis) and DFT quantum-chemical studies on 2-[(2,4-Dimethylphenyl)iminomethyl]-6-methylphenol

Density functional calculations of the structure, vibrational spectra, molecular electrostatic potential and thermodynamic functions have been performed at the B3LYP/6-311++G(d,p) level of theory for the Schiff base compound 2-[(2,4-Dimethylphenyl)iminomethyl]-6-methylphenol. Experimental and theoretical Fourier transform infrared (FT-IR) studies of the title compound show the preference of enol form, as supported by X-ray analysis results. Using the time-dependent density functional theory (TD-DFT) method, electronic absorption spectra of the compound have been predicted and a good agreement is determined with the experimental ones. To investigate the tautomeric stability, optimisation calculations at B3LYP/6-311++G(d,p) level were performed for the enol and keto forms of the title compound. Calculated results show that its enol form is more stable than that of the keto form. The predicted non-linear optical properties of the title compound are much greater than those of urea. The changes in thermodynamic properties for the formation of the title compound with the temperature ranging from 200 K to 500 K have been obtained using the statistical thermodynamic method. At 298.15 K the change of Gibbs free energy for the formation reaction of the title compound is 37.03 kJ/mol. The title compound cannot be spontaneously produced from the isolated monomers at room temperature. The tautomeric equilibrium constant is also computed as 1.23×10^?3 at 298.15 K for enol ? keto tautomerisation of the title compound.     

Nuclear resonance vibrational spectroscopy of iron–sulfur proteins

Nuclear inelastic scattering in conjunction with density functional theory (DFT) calculations has been applied for the identification of vibrational modes of the high-spin ferric and the high-spin ferrous iron–sulfur center of a rubredoxin-type protein from the thermophylic bacterium Pyrococcus abysii.     

Retinal in bacteriorhodopsin and related molecular models investigated with Raman spectroscopy and density functional theory calculations

A first‐principles assisted study of the Raman spectrum associated with the photoactive chromophore in bacteriorhodopsin (bR) allowed the elucidation of the effective coupling existing between the π electrons of the retinylidene chromophore and the local environment of the Schiff base. The role of the counter‐ion on the electronic and vibrational structure of the chromophore is investigated by means of density functional theory (DFT) calculations. Several molecular models of the retinylidene chromophore interacting with different counter‐ions facing the Schiff base have been considered. The counter‐ion induces a strong modulation of the position of both the UV–vis absorption maximum and the strong Raman active collective CC stretching mode, related to the effective conjugation coordinate (ECC). Experimental Raman and UV–vis absorption data are interpreted in the light of these theoretical findings. The data collected in this paper provide an interesting accumulation of points along the optical gap versus ECC wavenumber relationship. Copyright © 2011 John Wiley & Sons, Ltd.