苯并二呋喃酮类染料及其取代物的密度泛函理论研究

采用密度泛函理论(DFT)方法,在B3LYP/6-31G*的水平上对苯并二呋喃酮类染料及其芳环6,6’-,9,9’-,10,10’-,11,11’-,12,12’-,13,13’-取代衍生物进行理论计算,讨论了CH3、OCH3、Cl、NO2在不同位置取代对分子的几何结构、电子结构和能量的影响。同时采用含时的密度泛函理论(TD-DFT)方法在相同水平下计算其电子光谱。结果表明:母体被取代后能量降低,结构变稳定;苯并二呋喃酮类染料及其芳环取代物的最低单重激发态均主要源自HOMO-LOMO(π-π*)跃迁。     

CH3和CN取代8-羟基喹啉电子光谱性质的含时密度泛函理论研究

对8－羟基喹啉QH及其代衍生物MQH和CNQH用密度泛函方法（DFT）在B3LYP／6－31G＊水平上进行理论计算，探讨了供电子取代基（－CH3）和吸电子取代基（－CN）对分子电子结构，前线分子轨道能和光谱性质等的影响规律，在此基础上采用含时密度泛涵方法（TD－DFT）计算了电子光谱，计算结果表明，MQH，QH和CNQH的最低激发单重态都是A，激发能分别为3．58，3．72和3．74eV，在高激发态，无论是供电子基团（－CH3）还是拉电子基团（－CN），都导致取代衍生物的电子光谱红移。     

靛蓝及其取代物的密度泛函理论研究

运用量子化学中密度泛函理论(DFT)方法，在B3LYP／6-31G^ 水平上对靛蓝及其芳环4，4′-，5，5′-，6，6′-，7，7′-取代衍生物进行理论计算．探讨了F，Cl，Br，NO2，CH3O，CH3在不同位置的取代对分子的几何构型、电子结构和电子光谱的影响，获得与实验结果相一致的结论．还用含时密度泛函理论(TD-DFT)方法在相同水平计算其电子光谱．结果表明靛蓝及其芳环取代衍生物的最低激发单重态(S1)均源自HOMO-LUMO(π-π^*)跃迁．     

烷基取代对罗丹明的电子结构与光谱的影响

在密度泛函理论(DFT)的B3LYP水平对不同烷基在不同位置取代形成的8种罗丹明化合物进行结构优化,并在此基础上应用含时密度泛函理论(TD-DFT)和单激发组态相互作用(CIS)方法分析了取代基对罗丹明的电子结构、前线分子轨道及电子光谱的影响.计算结果表明,前线分子轨道主要分布在罗丹明分子的氧杂蒽环上,罗丹明分子中两个N端的H各只有1个H被烷基取代时,最高占据轨道(HOMO)在主要共轭环分布最多,且HOMO和最低未占据轨道(LUMO)分布比例相差最小,两个N端4个H同时被甲基取代时,能隙最窄,对气相最大吸收波长红移程度最大,两个N端4个H同时被乙基取代时,气相荧光最大,发射波长最长.     

C62及其吡啶衍生物结构与电子光谱的密度泛函理论研究

采用密度泛函理论(DFT)方法, 在TZP基组水平下计算C62及其吡啶衍生物几何与电子结构, 在全优化构型基础上, 采用TD-DFT方法对其低激发态进行计算, 预测其电子吸收光谱. 结果表明, 四种异构体的电子光谱中, 特征吸收来自C62内部的跃迁贡献, 也包括取代基到C62的电子转移. 取代基中N原子位置对490 nm左右吸收带的强度有影响, 两种顺式结构表现较为明显, 而两种反式结构衍生物光谱特征基本相同.     

含三亚吡嗪生色团的有机芳香分子的二阶NLO性质

采用密度泛函理论B3LYP/6-311G**方法,对一系列含三亚吡嗪生色团的有机芳香分子的几何结构、二阶NLO性质和电子光谱进行了理论研究.结果表明:研究分子中两侧取代基的推或拉电子能力和相对位置的变化,以及引入五元芳香杂环都将对分子的二阶NLO系数β值产生重要影响.当左右两侧取代基分别为—NO2和—C(NH2)3以及引入吡咯杂环时可以获得最大的β值,并显示了较好的透光性.该系列化合物在NLO材料领域有着较好的应用前景.     

含咔唑生色团的有机芳香杂环分子的二阶非线性光学性质

采用密度泛函理论B3LYP/6-31G^*方法, 对一系列含咔唑生色团的有机芳香杂环分子进行结构优化, 并采用有限场(FF)和含时密度泛函理论(TD-DFT)方法在6-311G^**水平上探讨了体系的二阶非线性光学(NLO)性质和电子光谱. 结果表明, 咔唑取代基推或拉电子能力的改变和引入芳香杂环对研究分子的极化率α和二阶NLO系数β值都有较大影响. 当取代基分别连有拉电子硝基和推电子羟基, 以及引入呋喃杂环都可以使体系分子的β值随分子的最大吸收波长λ_max的增大而减小(蓝移). 该系列化合物兼具有很大的二阶非线性响应与良好的透光范围, 避免了“非线性-透光性”矛盾, 可能在非线性材料领域中有很大的潜在应用价值.     

呋喃查尔酮结构与电子光谱的密度泛函理论研究

在密度泛函理论的PBE1PBE/6-31G(d)水平上对呋喃查尔酮及其衍生物的几何结构进行优化计算.在获得基态稳定结构的基础上,应用含时密度泛函理论计算其电子吸收光谱,探讨了取代基和溶剂对电子吸收光谱的影响,计算结果与实验结果吻合很好,平均绝对偏差仅为3.3nm(0.04eV).结果表明,取代基的引入和溶剂极性的增大均使光谱发生红移.通过前线轨道分析,揭示了该类化合物的主要吸收峰均源自分子中HOMO→LUMO电子跃迁.     

氟代十二顶点碳硼烷结构和非线性光学性质的理论研究

采用密度泛函理论(DFT)方法,计算并分析了四氟取代十二顶点碳硼烷及其衍生物的结构和非线性光学(NLO)性质.结果表明,改变四氟碳硼烷取代基的共轭性或给吸电子能力,会使分子中碳硼笼原子间距离发生改变.碳硼烷取代基的给吸电子能力越强,其偶极矩越大.分子极化率随取代基共轭性和体积的增加而增大.引入强吸电子基或增加四氟碳硼烷取代基的共轭性,可使其二阶NLO响应明显增强.通过分析分子的电子光谱和对应的分子轨道组成可知,第一超极化率最大的分子4a’发生碳硼笼到并苯取代基的电荷转移.     

三联吡啶铂(Ⅱ)配合物光谱性质的密度泛函研究

采用密度泛函理论方法(DFT),对三联吡啶铂(Ⅱ)配合物的结构与电子光谱进行了系统研究.筛选的PBE/LanL2DZ(6-311+G(d))—BMK/LanL2DZ(6-31+G(d))方法,计算结果能较好地与实验值吻合:对光谱峰波长的计算,吸收光谱和发射光谱平均误差分别为14 nm和17 nm.通过对前线分子轨道的分析,归属了各光谱峰的跃迁类型.计算结果表明,不同推拉电子效应的取代基对配合物光谱峰的位置和跃迁类型具有较大影响,为已有的实验结论提供了有力的理论阐述.     

Substituent Effect on Infrared Spectra and Thermodynamic Properties of Polynitroamino Substituted Cyclopentane and Cyclohexane

Density functional theory method was employed to study the effect of the nitroamino group as a substituent in cyclopentane and cyclohexane, which usually construct polycyclic or caged nitramines. Based on the optimized molecular structures of two groups of monocyclic nitramines at the B3LYP/6-31G** level, the infrared (IR) spectra were obtained and assigned by harmonic vibrational analysis. The calculated results agree reasonably with the available experimental data. According to the principles of statistic thermodynamics, thermodynamic properties were derived from the IR spectra, which were linearly correlated with the number of nitroamino groups as well as the temperature. The.     

Semi-empirical molecular orbital calculations for pyridinealdoximes and acetamidopyridines

Tautomerism of pyridinealdoximes and acetamidopyridines is discussed with regard to their electronic absorption spectra. The spectra of both neutral and ionic forms of the molecules are interpreted by means of the Pariser—Parr—Pople type of calculation in a satisfactory way.The stability of 2- and 4-pyridinealdoxime tautomers is investigated using the CNDO/2 method. The lactim are more stable than the lactam forms of the molecules. The molecules having the substituent group of the syn-configuration are more stable than the molecules with other configurations of the substituent.     

Photocrosslinking of poly(methyl acrylate)s containing the 1,3-dioxolane structure as a pendant group

(2-Ethyl-2-methyl-1,3-dioxolan-4-yl)methyl- and (2-methyl-2-phenyl-1,3-dioxolan-4-yl) methyl acrylates were synthesized and polymerized. The photochemical behavior of the resulting polymers was investigated to determine whether the polymers pending on the 1,3-dioxolane structure were readily crosslinked with ultraviolet (UV) irradiation. The degree of crosslinking was estimated by the weight-loss method by immersion in acetone, with the result that the polymer with an aromatic substituent was more photocrosslinkable than the polymer that bore the aliphatic substituent. The catalytic effect on photocrosslinking of polymers was also studied by using benzoin and cobalt naphthenate. The infrared (IR) spectra of polymers irradiated in air that showed the new band at 3450 cm^?1 were attributed to a hydroxyl group; however, the spectra of polymers irradiated in vacuum displayed little absorption at 3450 cm^?1. To explain the mechanism of crosslinking model compounds were prepared and irradiated with UV light. It was concluded that crosslinking proceeds mainly from the fission of the 1,3-dioxolane ring and the coupling of the yielding radicals, together with autooxidation by atmospheric oxygen.     

N1取代基结构对菲并咪唑荧光色纯度的影响

以1,2-二苯基菲并咪唑(PPI)为模型化合物, 通过改变N1苯环上取代基结构制备了2类PPI衍生物, 并采用核磁共振谱对其化学结构进行了确认. 通过对PPI及其衍生物的单分子荧光光谱精细结构的分析, 比较了取代基位置和结构的变化对菲并咪唑类化合物荧光过程中发射主峰精细振动结构及所占比例的影响. 其中, N1链接苯环中R4位的取代基效应最显著, 当引入推电子或弱的吸电子取代基时, 菲并咪唑类衍生物的低能级发射比例降低, 荧光色纯度提高; 当引入强吸电子取代基时, 低能级发射比例增加, 光谱半峰宽加大. 本文结果为菲并咪唑基“蓝光”材料的设计提供了一定数据的支持与科学依据.     

Theoretical investigation of the π -electronic structure and spectra of protonated aromatic carbonyl compounds

The π-electronic structure and spectra of the protonated aromatic carboxylic acids, aldehydes and ketones have been calculated by the Pariser–Parr–Pople method. An essential modification was that the positive charge has been considered as delocalized within the substituent group. The best agreement for the cation of benzoic acid was obtained using a symmetric carboxy model with equal charges on both oxygen atoms. This model gave equally good results for the protonated fluoro-, chloro- and methylbenzoic acids, as well. The delocalized charge model was successfully applied in the calculation of aromatic aldehydes and ketones. The methyl group was treated both as a one- and as a two-centre substituent.     

Synthesis and NMR spectral studies of N-chloroacetyl-2,6-diarylpiperidin-4-ones

A series of 2,6-diarylpiperidin-4-ones having electron withdrawing chloroacetyl group at the heterocyclic nitrogen were synthesized. Unambiguous characterizations of the synthesized compounds were achieved by one-dimensional ((1)H NMR and (13)C NMR) and two-dimensional (HOMOCOSY, NOESY and HSQC spectra for compounds 8 and 9 and HOMOCOSY spectrum only for 10) NMR spectroscopic data. The conformational preferences of N-chloroacetyl-2,6-diarylpiperidin-4-ones with and without alkyl substituent at C-3 and C-5 (8-14) have also been discussed using the spectral studies. The spectral data and extracted coupling constant values suggest that the compounds 8, 12 and 14 adopt flattened boat conformation whereas the remaining compounds exist in twist-boat conformations in solution with coplanar orientation of the chloroacetyl moiety present at the heterocyclic nitrogen. The substituent parameters for the chloroacetyl moiety on the heterocyclic ring carbons have also been derived and discussed elaborately on the basis of their steric, electronic and gamma-eclipsing interaction. This substituent at the nitrogen causes a substantial change on the chemical shifts of ring carbons and the associated protons.     

Synthesis of 5-hydroxyquinolines

A series of 5-hydroxyquinolines has been prepared via the Skraup reaction. Several regioisomers were made either by selective displacement of a leaving group or by using a bromo substituent as a blocking group. The bromo group was found to be an excellent blocking group due to its stability during the Skraup reaction and easy removal thereafter. Halides at the 5-position of quinoline were found to be much more reactive than those at the 7- and 8-positions. Finally, we have also found a unique method to reduce the pyridyl ring on quinolines, leaving a halogen substituent untouched.     

Genistein complexes with amines. Part II: ab initio study of the complexes with piperazine and triethylamine

The piperazine and triethylamine complexes of genistein, exhibiting high immunosuppressant activity, were ab initio modeled at RHF/6-31G^** level and results were compared with those obtained for genistein–morpholine complexes by X-ray, NMR, and theoretical methods. The most stable genistein–piperazine complex is formed due to hydrogen bonding of genistein's OH group at position C7 to piperazine's nitrogen atom. In the most stable genistein–triethylamine complex genistein's OH group at position C4′ (position para to phenyl substituent) and trimethylamine nitrogen atom are engaged in hydrogen bond formation. The calculations confirmed our previous NMR conclusion that piperazine is more strongly complexed by genistein than is morpholine or triethylamine. The theoretical ¹³C NMR spectra correlate fairly well with the experimental spectra.     

Reaction of Tertiary 2-Chloroketones with Cyanide Ions: Application to 3-Chloroquinolinediones

3-Chloroquinoline-2,4-diones react with cyanide ions in dimethyl formamide to give 3-cyanoquinoline-2,4-diones in small yields due to the strong hindrance of the substituent at the C-3 atom. Good yields can be achieved if the substituent at this position is the methyl group. In the methanol solution, the reaction proceeds by an addition mechanism to form 2-oxo-1a,2,3,7b-tetrahydrooxireno[2,3-c]quinoline-7b-carbonitriles, from which 4-hydroxy-3-methoxy-2-oxo-1,2,3,4-tetrahydroquinoline-4-carbonitriles are subsequently formed by opening of the epoxide ring with methanol. Some minor products of these reactions have also been isolated. The ¹H, ¹³C and ¹⁵N NMR spectra of the prepared compounds were measured, and all resonances were assigned using appropriate two-dimensional spectra.