高浓度LiClO4/丙酮溶液中离子-溶剂和离子-离子的相互作用

利用红外和拉曼光谱技术研究了不同浓度LiClO₄/丙酮溶液中离子-溶剂和离子-离子的相互作用. 红外和拉曼光谱的分析表明, Li^＋与丙酮分子发生了强烈的相互作用, 导致丙酮C—C伸缩振动谱带、C＝O伸缩振动谱带等发生了分裂. Li^＋的溶剂化数随溶液浓度的增加逐渐降低, 在所研究的LiClO₄浓度范围(0.31～3.98 mol•kg^－1)内由3.4减小到1.9. 此外, 根据的谱带变化确定了溶液中存在的多种离子对的形式, 计算了缔合平衡常数, 并与电导实验结果进行了比较, 解释了这两种方法测定的离子缔合常数存在差异的主要原因.     

高浓度LiClO4/丙酮溶液中离子-溶剂和离子-离子的相互作用

利用红外和拉曼光谱技术研究了不同浓度LiClO₄/丙酮溶液中离子-溶剂和离子-离子的相互作用. 红外和拉曼光谱的分析表明, Li^＋与丙酮分子发生了强烈的相互作用, 导致丙酮C—C伸缩振动谱带、C＝O伸缩振动谱带等发生了分裂. Li^＋的溶剂化数随溶液浓度的增加逐渐降低, 在所研究的LiClO₄浓度范围(0.31～3.98 mol•kg^－1)内由3.4减小到1.9. 此外, 根据的谱带变化确定了溶液中存在的多种离子对的形式, 计算了缔合平衡常数, 并与电导实验结果进行了比较, 解释了这两种方法测定的离子缔合常数存在差异的主要原因.     

新型胍盐离子液体剪切粘度性质的预测

[guanidinium]^＋[Tf₂N]^－是一类可应用于锂离子电池电解液的新型胍盐离子液体. 针对该类九种胍盐离子液体, 基于全原子分子力场, 采用非平衡分子动力学(周期性微扰方法)对其剪切粘度进行了计算和预测. 讨论了模拟尺寸、稳态速度场以及力场参数对模拟结果的影响. 计算结果很好的体现出剪切粘度系数随着温度以及分子尺寸大小的变化趋势. 利用周期性微扰线性外推的方法计算得到的粘度系数与实验值吻合良好, 在353 K下的最大偏差在12%以内.     

CIC（O）NCS分子筛振动光谱的理论研究

采用密度泛函理论DFT（B3LYP）方法,以6－31G为基组对CIC（O）NCS的反式和顺式两种构型的几何结构、振动谐性力场和红外光谱进行了研究 。B3LYP／6－31G的理论力场由适用于B3LYP／6－31G计算水平和大多数有机分子的一套固定标度因子进行标度,根据标度后的理论力场进行简正坐标分析得到的势能分布（PED）和红外光谱强度值对CIC（O）NCS分子物顺式和反式两种构型的振动基频进行了理论归属。     

基于BODIPY衍生物的氟离子荧光比例探针的研究

利用有机合成中Si-O键受氟离子（F-）作用断裂形成O-的机理,开展了以荧光染料BODIPY-PhOSi作为荧光探针检测溶液中的微量氟离子的研究。BODIPY-PhOSi受氟离子作用形成BODIPY-PhO-,引起荧光强度变化,从而达到检测微量氟离子的作用。实验通过有机反应合成了荧光探针BODIPY-PhOSi,然后采用荧光光谱仪进行低浓度溶液中微量氟离子滴定实验,得到不同浓度氟离子的荧光光谱曲线,谱图分析表明荧光探针BODIPY-PhOSi对氟离子的响应呈比例比色型,通过数据计算得到荧光探针的最小检测限,在对比实验中氟离子检测表现出了良好的选择性。     

高氯酸锂甲醇溶液中离子溶剂化和离子缔合现象

通过红外光谱技术探讨了高氯酸锂甲醇溶液中离子与溶剂、离子与离子之间的相互作用。红外光谱分析结果表明:锂离子与溶剂发生了相互作用导致甲醇分子的O-H伸缩振动区蓝移,ClO4-的特征谱带的变化表明了溶液中存在离子缔合。根据密度泛函理论,对不同溶剂化数的配合物结构和两种离子对形式进行优化及热力学性质的计算。     

丙酮酸分子结构与振动光谱的密度泛函理论研究

用密度泛函方法BLYP、B3LYP和从头算Hartree-Fock(HF)方法在6-31G*基组水平上对丙酮酸分子的几何结构（甲基的重叠式和交错式两种构象）和振动光谱分别进行了优化和计算,并给出了各种频率所对应的红外强度及拉曼活性,对光谱进行了指认。结果表明：在丙酮酸分子的两种构象中,重叠式比较稳定*B3LYP计算得到的构型参数与实验结果比较一致;在振动频率的计算中,BLYP未标度力场所计算的非CH3伸缩振动基频预测值和实验值的平均绝对偏差为10.4cm-1;而HF标度力场的平均绝对偏差为17.9cm-1。说明两者的结果与实验观测频率比较吻合,但B3LYP的频率计算值偏差（38.3cm-1）较大。根据振动频率的势能分布和红外光谱强度对此分子的振动基频进行了理论归属。     

连续模型处理高剥离态离子在金属表面的能量获得

当高剥离态离子接近清洁金属表面时，表面上的电子由于强库仑相互作用会从金属表面转移到带有高电荷的离子上．这个电子转移过程可以用一速率方程确定，其中速率常数与高剥离态离子所带净电荷数，以及离子与金属表面的距离有关．由于金属表面的镜象势的作用，高剥离态离子在金属表面附近会受到加速作用而获得能量．本文采用经典镜象势，用数值方法处理了确定电子转移的速率方程，计算了高剥离态离子在金属表面的能量获得，计算结果与两组实验数据比较吻合．     

LiF与MgF2晶体中离子簇CoF6^4—的电子光谱和吸收光谱的从头算

用量子化学的从头算方法对ＬｉＦ与ＭｇＦ２晶体中的离子簇ＣＦ６＾２－的电子结构与吸收光谱进行了计算，计算结果与实验基本一致，说明把ＣｏＦ６＾４－放在ＬｉＦ与ＭｇＦ２的马德隆场中进行从头计算的理论模型是可取的；并澄清了文献用Ｘα方法对ＣｏＦ６＾４－的光谱项对称分类不清楚的地方。     

计算化学键离子性的新经验公式

自从Pauling提出键的离子性概念和键离子性的定量标度以来，人们从不同角度相继提出了好几个计算化学键离子性百分率的方法。1932年，Pauling认为化学键的离子性百分率可由下式计算：     

Analysis of Slightly Rough Thin Films by Optical Methods and AFM

 In this paper the analysis of a family of rough silicon single crystal surfaces covered with native oxide layers is performed using a combined optical method based on a multisample treatment of the experimental data obtained using variable angle of spectroscopic ellipsometry and near normal spectroscopic reflectometry. Within this analysis the values of the thicknesses of the native oxide layers are determined together with the values of statistical parameters of roughness, i.e. with the rms values of the heights and the values of the autocorrelation lengths, for all the samples studied. For interpreting experimental data the perturbation Rayleigh–Rice theory and scalar diffraction theory are employed. By means of the results of the analysis achieved using both the theories limitations of the validity of these theories is discussed. The correctness of the values of the statistical parameters determined using the optical method is verified using AFM measurements.     

Ab initio parametrized MM3 force field for the metal-organic framework MOF-5

A new valence force field has been developed and validated for a particular class of coordination polymers known as nanoporous metal-organic frameworks (MOFs), introduced recently by the group of Yaghi. The experimental, structural, and spectroscopic data in combination with density functional theory calculations on several model systems were used to parametrize the bonded terms of the force field, which explicitly treats the metal-oxygen interactions as partially covalent as well as distinguishes different types of oxygens in the framework. Both the experimental crystal structure of MOF-5 and vibrational infrared spectrum are reproduced reasonably well. The proposed force field is believed to be useful in atomistic simulations of adsorption/diffusion of guest molecules inside the flexible pores of this important class of MOF materials.     

分子力场进展

分子力学（简称ＭＭ）是近年来化学家常用的一种计算方法。与量子力学从头计算和半经验方法相比，用分子力学处理大分子可以大大节省计算时间，而且，在大多数情况下，用分子力学方法计算得到的分子几何构型参数与实验值之间的差值可在实验误差范围之内。所以，分子力学是研究生物化学体系的有效和可行的手段。分子力学的核心是分子力场。本文介绍了分子力场的量子力学背景、分子力场和光谱力场之间的关系。分子力场的一般形式、分力     

A combined experimental and theoretical approach for structural study on a new cinnamoyl derivative of 2-acetyl-1,3-indandione and its metal(II) complexes

The synthesis, structure and spectral properties of a new cinnamoyl derivative of 2-acetyl-1,3-indandione (2AID), p-fluoro-cinnamoyl-1,3-indandione, LH and its metal(II) complexes with Cu(II), Zn(II) and Cd(II), are described. In order to verify the molecular structure of the free ligand and its metal complexes, model geometries based on the spectroscopic data were optimized using quantum chemical methods. The experimental spectroscopic data (IR and NMR) of the ligand, LH, complemented by the calculated ones, show that it exists in the exocyclic enolic form in the gas phase, solution and solid state. Good quality single crystals of Cd(II) complex were obtained from a DMSO solution and were studied by means of single-crystal X-ray diffraction. The data show bidentate coordination of the ligand and two DMSO molecules coordinated to the metal centre, thus forming a complex with octahedral geometry. On the contrary, the spectroscopic data on the amorphous samples indicate a square planar geometry of the Cu(II) complex and distorted octahedral geometry for Zn(II) and Cd(II) complexes with two water molecules coordinated to the metal centre. The used quantum chemical method for structure optimization of the transition metal complexes, B3LYP/LANL2DZ, shows very good agreement with the crystallographic data and, therefore, was also employed for structural determination for the non-crystalline complexes. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Formation of luminescent states in polybenzimidazole-based films

Here we present the results of experimental studies and theoretical computations of the spectroscopic parameters of polybenzimidazole (PBI) films formed by casting from a formic acid solution. The kinetics of the polymer luminescence is described, depending on the amount of the residual solvent. We demonstrate the changes in the intensity of the film luminescence with the formic acid release from the film, which is confirmed by the IR data. Based on the quantum chemistry computations, a mechanism is suggested for the formation of absorption and luminescence bands characteristic of the PBI matrix.     

Nonempirical ab initio studies on inner-sphere reorganization energies of M2+(H2O)6/M3+(H2O)6 redox couples at valence basis level

On the basis of the basic feature of the electron transfer reactions, a new theoretical scheme and application of a nonempirical ab initio method in computing the inner-sphere reorganization energies (RE) of hydrated ions in electron transfer processes in solution are presented at valence STO basis (VSTO) level. The potential energy surfaces and the various molecular structural parameters for transition metal complexes are obtained using nonempirical molecular orbital (MO) calculations, and the results agree very well with experimentally observed ones from vibrational spectroscopic data. The results of inner-sphere REs obtained from these calculations via this new scheme give a good agreement with photoemission experimental findings and those from the improved self-exchange model proposed early for M²⁺(H₂O)₆/M³⁺(H₂O)₆(M = V, Cr, Mn, Fe, and Co) redox couple systems and are better than those from semiempirical INDO/II MO method and other classical methods. Further, the observed agreement of the optimized structural data and the results of inner-sphere REs of complexes with experimental findings confirms the following: (1) the validity of nonempirical MO calculation method to get accurate structural parameters and inner-sphere RE for the redox systems for which reliable vibrational spectroscopic data are not available, (2) the validity of the improved self-exchange model proposed early for inner-sphere RE, and (3) the reasonableness of some approximations adopted in this study. © 1997 John Wiley & Sons, Inc.     

Modeling the solvation of peptides. The case of (s)-N-acetylproline amide in liquid water

The structure and properties of (s)-N-acetylproline amide (NAP) in aqueous solution are studied by exploiting a continuum solvation model. The conformational preference of NAP as a function of the environment is discussed as well as data for a number of chiral and non-chiral spectroscopic and response properties (IR/VCD, Raman/VROA, UV/CD, ORD, NMR), whose calculation with the accounting of solvent effects is now possible due to recent developments introduced in the PCM approach. When available, calculated results are compared with experimental data, so as to evaluate the quality of the continuum approach to the solvation of this system.     

Electronic factor in electron self-exchange reaction of hydrated redox ion pairs from thermodynamic data

An accurate scheme for determining the electronic factor of the electron self-exchange reaction in solution is presented in this paper. The used various activation parameters and slopes of potential energy surfaces are obtained in terms of an improved activation model and the accurate potential function determined from the vibrational spectroscopic and thermodynamic data. The coupling matrix elements are determined using numerical integral method over the perturbed double-zeta Slater-type state functions. Theoretical results of electronic factor in this work are found in close agreement with those extracted from experimental rate constant data and to be less than unity. Results indicate that outer-sphere electron transfer reactions in solution involving hydrated transition metal ions are nonadiabatic in nature.     

3-甲基-4-氨基-5-亚硝基尿嘧啶电化学还原反应

我们曾对4-氨基-5-亚硝基尿嘧啶系列物在高超电势下的还原机理做过一些研究^[1,2]。在低超电势下的还原机理尚未见报道。本工作用伏安法及恒电流阶跃法探讨了酸性介质中,3-甲基-4-氨基-5-亚硝基尿嘧啶(简写为3-MU)在低超电势范围内的还原历程。     

Novel methods of automated structure elucidation based on 13C NMR spectroscopy

Three new approaches for automated structure elucidations of organic molecules using NMR spectroscopic data were introduced recently. These approaches apply a neural network 13C NMR chemical shift prediction method to rank the results of structure generators by their agreement of the predicted and experimental chemical shifts. These three existing implementations are compared using realistic example molecules. The applicability and reliability of such approaches is addressed.