胺类杂氮硅三环化合物红外光谱研究

对γ－氨丙基杂氮硅三环，γ－乙二胺基丙基杂的氮硅三环，γ－乙二撑三胺基丙基杂质硅三环３种化合物的红外光谱进行了研究，胺基的特征吸收为：伸缩振动υａｓ（ＮＨ）和υｓ（ＮＨ）；剪式振动δ（ＮＨ２）。三环的特征吸收为：ＣＨ２的弯曲振动ω（ＣＨ２Ｎ）ω（ＣＨ２Ｏ）和τ（ＣＨ２Ｏ）；Ｃ－Ｏ键的伸缩振动υ（Ｃ－Ｏ）；Ｎ－Ｃ键的伸缩振动υ（ＮＣ３）和υ（ＮＣ３），Ｓｉ－Ｏ键的伸缩振动υ（Ｓｉ－Ｏ）和υ（Ｓｉ－Ｏ     

异丙醇的O-H伸缩振动泛频光谱和分子构像

使用高灵敏的光腔衰荡光谱(CavityRingDownSpectroscopy)技术测出了异丙醇的O-H伸缩v=4、5振动泛频光谱,每个振动能级都有三个吸收峰,被归属为分子构像的O-H伸缩泛频吸收.给出了光腔衰荡光谱的振动泛频吸收的谱带强度公式,并求得分子不同构像在不同振动能级的O-H伸缩泛频吸收的谱带强度;同时利用局域模理论,求得分子各O-H伸缩局域模振子的机械频率(X1)、非谐性(X2)以及解离能(D).用密度泛函(DFT)B3LYP/6-31+G*理论方法优化了分子的各种可能构像,验证了分子存在反式(trans)和偏转(gauche)两种稳定构像,计算的分子的O-H伸缩频率及构像稳定性同实验结果是一致的.     

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。     

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。     

CH~2Br~2分子中Fermi共振的研究

本文在分子内坐标表象上构造了CH~2X~2分子的振动量子Hamilton算子,给出了计算CH~2X~2分子的CH伸缩振动与HCH弯曲振动的Fermi共振新方法.结合已有的泛频数据,采用69个变分基组,具体计算了CH~2Br~2和CD~2Br~2分子的泛频谱.理论频率与实验频率符合得很好,并且得到一组包括势能常数f~raa在内的力场拟合值.     

铜分子筛Cu(Ⅰ)物种上吸附CO的漫反射红外光谱

应用漫反射红外光谱测定了不同的铜分子筛经真空自还原后吸附ＣＯ的基频,组频和泛频谱带,结果表明,ＣＯ压力较低时,形成Ｃｕ（Ⅰ）（ＣＯ）吸附物种,其种类与分子筛的结构特性有关。随ＣＯ２压力增高,部分吸附物种转变为Ｃｕ（Ⅰ）（ＣＯ）２,分析Ｃｕ（Ⅰ）（ＣＯ）基频和组频谱带可得到比Ｃ－Ｏ伸缩振动更灵敏的反映Ｃｕ（Ⅰ）和ＣＯ作用的Ｃｕ（Ⅰ）－Ｃ伸缩振动频率。     

InI分子电子态的CCSD-LRT方法研究

使用单双激发耦合簇线性响应理论(CCSD-LRT),和相对论有效核势(RECP)基组对InI分子Λ-S电子态进行了研究.计算得到了12个价态和4个Rydberg态的势能曲线(PEC),以及包括垂直激发能Te、平衡键长Re以及振动频率ωe和ωeχe在内的光谱常数,与实验数据相当符合.另外,计算得出在1Π态之上33 000 cm－1附近有一些密集的浅势阱电子态,将实验上观测到位于31 500 cm－1附近的连续谱带归属为包括1Π态在内的这些电子态到基态的跃迁.     

杯（4）芳烃的红外光谱和拉曼光谱研究

本文研究了对－叔丁基杯（４）芳烃（ｐ－ｔｅｒｔ－ｂｕｔｙｌｃａｌｉｘ（４）ａｒｅｎｅ）的红外和拉曼光谱，杯（４）芳烃中分子内缔合氢键的性质在红外光谱中明显反映，而从拉曼谱图可以得出酚类寡聚物大环振动的分子信息。     

吡虫啉与牛血红蛋白相互作用的光谱研究

利用紫外可见光谱和荧光光谱研究了在生理pH值条件下农药吡虫啉与牛血红蛋白(BHb)的相互作用。实验结果表明:吡虫啉分子与BHb发生反应生成复合物,导致BHb内源荧光的猝灭,该猝灭属于静态猝灭。测定了不同温度下该反应的表观结合常数、结合位点数及结合热力学参数,热力学参数的变化表明上述作用过程是一个熵增加、自由能降低的自发分子间作用过程,吡虫啉与BHb之间以静电和疏水作用力为主;并用同步荧光光谱法探讨了吡虫啉对BHb构象的影响。     

鸟嘌呤红外光谱的密度泛函理论研究：标度量子力学（SQM） …

用密度泛函理论ＤＦＴ（Ｂ３ＬＹＰ）／６－３１Ｇ＾＊方法对鸟嘌呤分子的酮－胺式和醇－胺式异构体的几何结构、振动谐性力场和红外光谱进行了研究。理论力场由迁移自相关分子异胞睡咪唑的力学数标度因子进行标度。     

一水甲酸锂晶体三阶非线性光学性质理论研究

用含时藕合微扰Hartrre一Fork（CPHF）方法，有限场MP2理方法以及有向气 体方法，首次分别在分子和晶体水平上计算了一水甲酸锂晶体三次谐波极化率，表 明超分子γ(一3ω；ω,ω,ω)数值与超分子链长有线性关系；晶体x（一3ω;ω, ω,ω）计算值主要受到电子相关影响，其次受到基组和局域场影响，在非共振 条件下，频率色散的影响甚小'最后，估算了一水甲酸锂的三次谐波系数．     

Duplex formation and the onset of helicity in poly d(CG)n oligonucleotides in a solvent-free environment

The gas-phase conformations of a series of cytosine/guanine DNA duplexes were examined by ion mobility and molecular dynamics methods. Deprotonated duplex ions were formed by electrospray ionization, and their collision cross sections measured in helium were compared to calculated cross sections of theoretical models generated by molecular dynamics. The 4-mer (dCGCG) and 6-mer (dCGCGCG) duplexes were found to have globular conformations. Globular and helical structures were observed for the 8-mer (dCGCGCGCG) duplex, with the globular form being the more favored conformer. For the 10-mer (dCGCGCGCGCG), 14-mer (dCGCGCGCGCGCGCG), and 18-mer (dCGCGCGCGCGCGCGCGCG) duplexes, only helical structures were observed in the ion mobility measurements. Theory predicts that the helical structures are less stable than the globular forms in the gas phase and should collapse into the globular form given enough time. However, molecular dynamics simulations at 300 K indicate the helical structures are stable in aqueous solution and will retain their conformations for a limited time in the gas phase. The presence of helical structures in the ion mobility experiments indicates that the duplexes retain "solution structures" in the gas phase on the millisecond time scale.     

Ab initio studies on the vibrational spectra and conformational isomerism of 2,4-dimethyl-1,3-pentadiene

Ab initio was used to study the structure of various conformational isomers and their vibrational spectra of 2,4-dimethyl-1,3-pentadiene (2,4-PD) in detail. Two stable conformations, s-trans and s-cis, were found in which s-trans is more stable. The geometry of stable conformations and charge distributions were studied, and the effect of different basis sets on geometry optimization is discussed. The results of complete optimization indicate that molecular skeleton is nearly in a plane, its largest deviation is only 0.3 degrees. Therefore, it is reasonable and available to hypothesis that the molecule has Cs symmetry. The thermal dynamics conformations were calculated and compared with experimental values. DeltaH(o) between two conformations of 2,4-PD measured from experiment is 4.36 kJ/mol, deltaS(o) is 2.56 J/mol K., calculated results are slightly different from experimental ones. Vibrational frequencies of 2,4-PD conformers have been studied by ab initio molecular orbital calculations using different basis set. The calculated vibrational frequencies are analyzed and compared with the experimental spectra.     

Effect of branching and molecular weight on the viscoelastic properties of poly(butyl acrylate)

A series of poly(butyl acrylate) samples were prepared by emulsion polymerization with a range of molecular weights and degrees of chain branching. Characterization was performed with NMR (giving the fraction of branching, ranging from approximately 0 to 7%), gel permeation chromatography, viscometry, and determination of the gel fraction. The dynamic mechanical response, that is, the frequency dependence of the storage and loss moduli G′(ω) and G″(ω) was measured from 0.02 to 200 Hz. The occurrence of a significant insoluble fraction in the sample meant that full characterization of the molecular weight distribution was not possible, and so an unambiguous separation of the dependencies of the mechanical response on the degree of long‐chain branching (LCB) and short‐chain branching (SCB) and the molecular weight could not be made; however, trends dependent on the molecular weight alone were insufficient to model the results. At high frequencies, all trends in G′(ω) and G″(ω) could be ascribed to molecular weight dependencies; at low frequencies, the effects of both the molecular weight and total degree of branching could be inferred, with more highly branched samples showing lower storage and loss moduli. Although the relative amounts of SCB and LCB could not be determined, no dynamic features attributable to LCB were observed. The low‐frequency trends could be semiquantitatively fitted with reptation and retraction theory if it was assumed that an increased degree of SCB led to an increased tube size. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3335–3349, 2002     

Ab initio Hartree-Fock and density functional theory study on molecular structures, energies, and vibrational frequencies of conformations of 2-hydroxy-3-nitropyridine and 3-hydroxy-2-nitropyridine

The optimized molecular structures, vibrational frequencies and corresponding vibrational assignments of conformations of 2-hydroxy-3-nitropyridine and 3-hydroxy-2-nitropyridine molecules have been investigated using ab initio Hartree-Fock (HF) and density functional theory (B3LYP) methods with 6-311++G(d,p) basis set. The comparison of the experimental and calculated spectra of the molecules have shown that they exist in two conformations with the two OH bond angles (110 degrees and 250 degrees ) respective to the CO bond in the ground state and their energy curves having two minimums have been drawn.     

液相色谱Z值对溶菌酶分子构象变化的定量表征

目前, 研究蛋白分子的构象变化用得最多的是光谱法, 如荧光光谱、圆二色谱和核磁共振谱等[1]. 由于蛋白质分子构象变化与其在色谱中的保留行为直接相关[2], 所以色谱法也成为研究蛋白质分子构象变化的一种新方法[3]. 此外, 计量置换理论中的Z值也已被成功地用于表征生物大分子的构象变化[4]. 用Z值研究蛋白质分子构象变化的优点是可以使用不纯的样品, 这是因为在测定Z值的过程中会与其它组分相分离. 使用Z值还会对蛋白分子构象变化进行定量表征[5,6]. 本文以溶菌酶(Lys)为目标蛋白, 用色谱法[反相液相色谱(RPLC)和弱阳离子交换色谱(WCX)]系统地研究了Lys在不同变性(胍变非还原、脲变非还原、胍变还原和脲变还原)环境中因疏水性及电荷分布的不同对Lys分子构象变化的影响, 并用Z值进行了定量表征.     

Performance of W4 theory for spectroscopic constants and electrical properties of small molecules

Accurate spectroscopic constants and electrical properties of small molecules are determined by means of W4 and post-W4 theories. For a set of 28 first- and second-row diatomic molecules for which very accurate experimental spectroscopic constants are available, W4 theory affords near-spectroscopic or better predictions. Specifically, the root-mean-square deviations (RMSDs) from experiment are 0.04 pm for the equilibrium bond distances (r(e)), 1.03?cm(-1) for the harmonic frequencies (ω(e)), 0.20?cm(-1) for the first anharmonicity constants (ω(e)x(e)), 0.10?cm(-1) for the second anharmonicity constants (ω(e)y(e)), and 0.001?cm(-1) for the vibration-rotation coupling constants (α(e)). These RMSDs imply 95% confidence intervals of about 0.1 pm for r(e), 2.0?cm(-1) for ω(e), 0.4?cm(-1) for ω(e)x(e), and 0.2?cm(-1) for ω(e)y(e). We find that post-CCSD(T) contributions are essential to achieve such narrow confidence intervals for r(e) and ω(e), but have little effect on ω(e)x(e) and α(e), and virtually none on ω(e)y(e). Higher-order connected triples T(3)-(T) improve the agreement with experiment for the hydride systems, but their inclusion (in the absence of T(4)) tends to worsen the agreement with experiment for the nonhydride systems. Connected quadruple excitations T(4) have significant and systematic effects on r(e), ω(e), and ω(e)x(e), in particular they universally increase r(e) (by up to 0.5 pm), universally reduce ω(e) (by up to 32?cm(-1)), and universally increase ω(e)x(e) (by up to 1?cm(-1)). Connected quintuple excitations T(5) are spectroscopically significant for ω(e) of the nonhydride systems, affecting ω(e) by up to 4?cm(-1). Diagonal Born-Oppenheimer corrections have systematic and spectroscopically significant effects on r(e) and ω(e) of the hydride systems, universally increasing r(e) by 0.01-0.06 pm and decreasing ω(e) by 0.3-2.1?cm(-1). Obtaining r(e) and ω(e) of the pathologically multireference BN and BeO systems with near-spectroscopic accuracy requires large basis sets in the core-valence CCSD(T) step and augmented basis sets in the valence post-CCSD(T) steps in W4 theory. The triatomic molecules H(2)O, CO(2), and O(3) are also considered. The equilibrium geometries and harmonic frequencies (with the exception of the asymmetric stretch of O(3)) are obtained with near-spectroscopic accuracy at the W4 level. The asymmetric stretch of ozone represents a severe challenge to W4 theory, in particular the connected quadruple contribution converges very slowly with the basis set size. Finally, the importance of post-CCSD(T) correlation effects for electrical properties, namely, dipole moments (μ), polarizabilities (α), and first hyperpolarizabilities (β), is evaluated.     

Simulation of vibrational spectra of polydichlorophosphazene by molecular dynamics calculations: A study of the relaxed and stretched polymer

The infrared and Raman spectra (frequencies and intensities) of polydichloro-phosphazene are calculated with the help of molecular dynamics methods; the spectral patterns are analysed in relation to the bond conformations along the backbone. The application of a longitudinal stress to the polymeric chains and the corresponding spectral variations are simulated by the use of an expanded simulation box.