ⅢA族环分子GnHnm环伸缩振动拉曼光谱频率与分子芳香性关系的研究

本研究使用量子化学软件Gaussian09,选用杂化密度泛函B3LYP方法,选取6-311G+(d,p)基组,对ⅢA族环分子GnHnm(G=B、Al、Ga,n=3,5-8,m=-2,0)进行几何结构优化,并计算其独立核化学位移(NICS)以及环伸缩振动拉曼光谱频率(RSVRSF)。分析NICS与RSVRSF之间的相关性,探索RSVRSF与分子芳香性的关系。     

苯六甲酸的密度泛函研究

采用密度泛函理论的B3LYP/6-311+G(d,p)方法,对苯六甲酸单体进行了分子结构优化.在此基础上,对苯六甲酸的自然键轨道(NBO)、前线轨道(FMO)、均苯四甲酸的制取机理、红外光谱(IR)、核磁共振谱(NMR)和紫外-可见吸收光谱(UV-Vis)等进行了模拟计算.根据分子的键长、键级等,讨论了分子的断键位置和...     

卟吩芳香性的理论研究

使用B3LYP/6-31+G(d,p)方法对卟吩进行几何优化,表明卟吩分子是一个平面结构,吡咯环和去氢吡咯环的结构不同。使用核独立化学位移(Nucleus-Independent Chemical Shifts,NICS)和AICD(Anisotropy of the Induced Current Density)方法研究卟吩的芳香性,卟吩的芳香性是内共轭途径和外共轭途径芳香性的叠加,且外环共轭途径芳香性要更强一些。     

荷叶中黄酮类化合物的缓蚀性理论研究

用DFT中的B3LYP方法,在3-21G和6-311G水平上,研究荷叶黄酮类分子的分子结构及电子结构,并用Fukui指数分析活性。综合结论：槲皮素3-O-D-吡喃木糖基（1→2）-β-D-吡喃半乳糖苷、异鼠李素、槲皮素-3-丙酯、紫云英苷、山奈酚和异鼠李素-3-O-β-D-葡萄糖苷与金属吸附作用较强。Fukui指数表明：分子的亲核进攻和亲电进攻点主要位于羰基氧原子和与独立苯环连接的羟基氧原子上。     

皮质甾酮光谱的密度泛函理论研究

根据密度泛函理论(DFT),选择B3LYP方法,在6-31G(d,p)基组水平上优化得到了皮质甾酮分子的稳定构型,从键长、键角和二面角入手,分析探讨了皮质甾酮分子的结构特点。在优化的稳定构型的基础上,用含时密度泛函理论方法计算了皮质甾酮分子的紫外光谱,得到了其最大吸收波长、跃迁能等理论数据。采用B3LYP/6-31G方法计算了该分子的红外光谱和核磁共振碳谱。分析了红外吸收峰出现的区域及其振动模式,结合计算数据对得到的13C NMR化学位移进行了归属。计算结果为甾体类有机化合物的结构鉴定提供了理论基础。     

Cl原子与CH3COCH3抽氢反应的动力学研究

采用QCISD(T)/6-311++G(d,p)//B3LYP/6-31G(d,p)双理论方法研究了Cl原子与CH3COCH3的抽氢反应过程.在B3LYP/6-31G(d,p)水平上优化了反应物、产物、过渡态的几何构型,并作了最小能量路径分析.在从头算的基础上,用变分过渡态理论加小曲率隧道效应方法计算200～2500 ...     

酸催化青蒿素异构体转化的理论研究

采用密度泛函理论MP2/6-311++G(d,p)//B3LYP/6-311G(d,p)分别对青蒿素反应机理进行理论研究。研究结果表明:从热力学角度分析,该计算方法水平下,无论在气相还是液相酸性条件下,青蒿素的异构体相互转化均不能进行。     

次黄嘌呤和黄嘌呤的结构和振动光谱理论研究

次黄嘌呤和黄嘌呤是人体内嘌呤代谢的中间产物,它们在黄嘌呤氧化酶的催化作用下最终生成尿酸。在B3LYP/6-311++G(d,p)水平对次黄嘌呤和黄嘌呤的两种酮式异构结构h1-h2和x1-x2进行了结构优化和振动光谱计算。在310.15 K的水溶液中,在MP2/6-311++G(d,p)//B3LYP/6-311++G(d,p)水平计算了它们的相对自由能,计算考虑了电子相关效应、溶剂效应和温度校正。在水溶液中酮式结构的次黄嘌呤h1-h2、黄嘌呤x1-x2应为主要存在结构。     

1-丁基-3-甲基咪唑四氟硼酸盐分子结构理论研究

采用密度泛函理论,在B3LYP／6—311＋＋G（d,p）水平下,计算得阳离子1-丁基-3-甲基咪唑[Bmim]＋与阴离子四氟硼[BF4]-分子内结合能-338．03kJ／mol,同时运用AIMNBO理论探究其分子内成键原理。     

呋喃与CHF3和CClF3构成的分子间卤键的理论研究

用MP2方法,在6-31G（d,p）Tfll6-311G（d,p）基组下对复合物呋喃-CHF,体系和呋喃-CCIF,体系进行优化,研究了其分子间作用力的本质。计算结果表明,CXF3与呋喃分子之间的相互作用使c—x键长缩短,振动频率增大（蓝移）。自然键轨道（NBO）分析表明,在MP2／6—31G＊＊（6—311＊＊）水平上,由于键收缩效应处于优势地位导致c—x键形成蓝移。     

Experimental and Theoretical Study of O-Substituent Effect on the Fluorescence of 8-Hydroxyquinoline

The synthesis and characterization of different ether and ester derivatives of 8-hydroxyquinoline have been made. UV-visible and fluorescence spectra of these compounds have revealed spectral dependence on both solvent and O-substituent. The fluorescence intensity of ether derivatives revealed higher intensity for 8-octyloxyquinoline compared with 8-methoxyquinoline, whereas those of ester derivatives had less fluorescence than 8-hydroxyquinoline. Theoretical calculations based on Time-dependent density functional theory (TD-DFT) were carried out for the quinolin-8-yl benzoate(8-OateQ) compound to understand the effect of O-substituent on the electronic absorption of 8-hydroxyquinaline (8-HQ). The calculations revealed comparable results with those obtained from the experimental data. Optimized geometrical structure was calculated with DFT at B3LYP/6-311++G** level of theory. The results indicated that 8-OateQ is not a coplanar structure. The absorption spectra of the compound were computed in gas-phase and solvent using B3LYP and CAM-B3LYP methods with 6-311++G ** basis set. The agreement between calculated and experimental wavelengths was very good at CAM-B3LYP/6-311++G** level of theory.     

Furoxan Derivatives of Pyrene – A DFT Study

Furoxan-fused pyrenes and their dinitroso derivatives (obtained by furoxan ring opening) are considered for density functional treatment at the level of B3LYP/6-31G(d,p). Embedded benzofuroxan moiety in the furoxan-fused pyrene system is thought to undergo ring opening and reclosure process analogously to benzofuroxan itself. The stabilities, structural features, NICS(0) values, IR, and UV-VIS spectral aspects, etc., are investigated comparatively for these isomeric furoxan-fused pyrenes and their isomeric dinitroso derivatives.     

Cl原子与CH_3COCH_3抽提反应机理的密度泛函理论研究

QCISD(T)/6-311++G(d,p)//B3LYP/6-31G(d,p)双理论方法研究了Cl原子与CH3COCH3的抽提反应过程。该反应包括两个反应通道:即Cl原子从CH3COCH3上直接抽氢(R1)和抽取CH3基团(R2)。在B3LYP/6-31G(d,p)水平上优化了反应物、产物、过渡态的几何构型,并作了最小能量路径分析,计算了反应的焓值和反应势垒,结果表明R1势垒比R2势垒低109.48 kJ/mol,说明反应R1是主反应通道。     

咪唑苦味酸盐C3N2H5＋C6N3O7H2^-的合成、晶体结构和量子化学

利用咪唑的醇溶液与苦味酸的醇溶液合成了咪唑的苦味酸盐C_3N_2H_5~+C_6N_3O_7H_2~-,并培养出单晶,通过X射线单晶结构分析法测定了其晶体结构.结果表明,晶体属于正交晶系,空间群为Pbca,晶胞参数为:a=0.895 0 nm,b=1.347 4(3)nm,c=2.016 4 nm,α=β=γ=90°,V=2.431 7(3) nm~3,D_c=1.624 g/cm~3,Z=8,F(000)=1 216.运用Gaussian 03程序,在6-311+G(d)的基组上,用HF和B3LYP两种方法对标题化合物进行了理论研究,并对原子净电荷及原子间布局进行了分析.     

Nucleus-Independent Chemical Shift Criterion for Aromaticity in Some of the Corannulene Derivatives as Carbon Nanostructure: Effect of Substituent Groups on Aromaticity

Substitution of the peripheral H atoms in the corannulene molecule as a carbon nanostructure by OH, CH₃, NH₂, and NO₂ groups was done and the obtained structures were optimized employing MP2/6-31G(d) level of theory. Calculations of the nucleus-independent chemical shift (NICS) were performed to analyze the aromaticity of the corannulene rings and its derivatives upon substitution at B3LYP/6-311+G(d) level of theory. Comparison of NICS(1)_zz for concave and convex sides of corannulene derivatives indicated that substitution of H atoms in the corannulene molecule with OH, CH₃, NO₂, and NH₂ groups leads to decreasing of the aromaticity character of corannulene. We discussed about two efficient factors on the aromaticity and antiaromaticity of polycyclic aromatic compounds: electron donating or withdrawing and resonance effects. We showed that NICS values in all structures are strongly dependent on the type, number, and position of the substituted groups.     

席夫碱基咪唑啉缓蚀剂的密度泛函理论研究

用量子化学密度泛函理论(DFT)中的B3LYP方法,在6-31G(d)和6-311G(d,P)基组水平上,研究了席夫碱基咪唑啉化合物BIA、BIOHA、BIMHA和BIMMA的缓蚀性能与分子结构及电子结构的关系,讨论了计算结果与缓蚀性能的关系。结果表明缓蚀性能与电负性χ、亲电指数ω等亲电反应参数相关性良好,最后用Fukui指数分析了分子中原子的反应性。可以认为缓蚀剂分子通过离域于苯环平面LUMO接受电子发生亲电作用与金属表面形成吸附膜。     

Controlling the tacticity in the polymerization of N-isopropylacrylamide: A computational study

In this study, the effect of alcohols as solvents on the kinetics and the tacticity of poly(N-Isopropylacrylamide) (PNIPAM) is investigated with a combined static and molecular dynamics set of computational tools. Classical molecular dynamics calculations have been carried out to determine the location of the solvent molecules in the proximity of the monomer and the dimer. A combined implicit/explicit solvent model was used for the evaluation of the kinetics of the dimeric polymer chains. Rate constants are calculated with the B3LYP/6-311 + G(d,p)//B3LYP/6-31 + G(d), BMK/6-311 + G(d,p)//B3LYP/6-31 + G(d), and MPWB1K/6-311 + G(d,p)//B3LYP/6-31 + G(d) methodologies via the standard transition state theory. We show that due to the proximity of the -NH and carbonyl groups on the syndiotactic propagating dimeric and trimeric chains, the alcohol can stabilize the corresponding transition states by forming a bridge between these functionalities and accelerate this path more than its isotactic counterpart. In agreement with experiment, the increase in the syndiotactic PNIPAM and the acceleration of the reaction in the presence of t-BuOH is predicted with all the DFT functionals utilized in this study.     

Structural and Molecular Orbital Studies of Si-Phenyl Silaanthracenes

The Si-phenyl derivatives of 1-, 2-, 9- silaanthracenes have been subjected to theoretical analysis with density functional theory (B3LYP/6-31G(d)) to obtain their molecular orbital properties. 2-silaanthracene has been found to be thermodynamically the most stable derivative among the trio. Moreover, the effects of the position of the Si substitution and phenyl attachment on the aromaticity of the parent anthracene have been investigated by NICS calculations at ring centers. The structures have been found to be less aromatic with respect to their unsubstituted counterparts.