Hydrogen Bonding Effects on the Photophysical Properties of 2,3-dihydro-3-keto- 1H-pyrido[3,2,1-kl] phenothiazine

Time-dependent density functional theory （TDDFT） and femtosecond transient absorption spectroscopy were used to investigate the photophysical properties of 2,3-dihydro-3-keto-lH- pyrido[3,2,1-kl]phenothiazine （PTZ4） and 3-keto-lH-pyrido[3,2,1-kl]phenothiazine （PTZ5）. The calculated results obtained from TDDFT suggest that the red-shifts of the absorption spectra of these two fluorophores in methanol are due to the formation of hydrogen-bonded complexes at the ground state. Four conformers of PTZ4 were obtained by TDDFT. The two fluorescence peaks of PTZ4 in tetrahydrofuran （THF） came from the ICT states of the four conformers. The fluorescence of PTZ4 in THF showed a dependence on the excitation wavelength because of butterfly bending. The excited state dynamics of PTZ4 in THF and methanol were obtained by transient absorption spectroscopy. The lifetime of the excited PTZ4 in methanol was 53.8 ps, and its relaxation from the LE state to the ICT state was completed within several picoseconds. The short lifetime of excited PTZ4 in methanol was due to the formation of out-of-plane model hydrogen bonds between PTZ4 and methanol at the excited state.

Substituent Effects on the Hydrogen Bonding Between Phenolate and HF, H_2O and NH_3

B3LYP/6 31+g( d ) calculations were performed on the hydrogen bonded complexes between substituted phenolates and HF, H 2O as well as NH 3. It was found that some properties of the non covalent complexes, including the interaction energies, donor acceptor (host guest) distances, bond lengths, and vibration frequencies, could show well defined substituent effects. Thus, from the substituent studies we can not only understand the mechanism of a particular non covalent interaction better, but also easily predict the interaction energies and structures of a particular non covalent complex, which might otherwise be very hard or resource consuming to be known. This means that substituent effect is indeed a useful tool to be used in supramolecular chemistry and therefore, many valuable studies remain to be carried out.

EFFECT OF HYDROGEN BONDING ON DIRECTION OF PHOTOISOMERIZATION OF RETINOIDS:THE ORIGIN OF THE SOLVENT POLARITY EFFECT.

Studies of direction of photoisomerization of retinal,retinonitrile,a- retinonitrile and a trienenitrile analog in different solvents with varying wave- lengths of excitation and reaction temperature led to the conclusion that the well known solvent dependent photochemistry of retinoids is due to selective excitation of the hydrogen bonded species.

Effects of Hydrogen-bonding Interaction and Polarity on Emission Spectrum of Naphthalene-Triethylamine in Mixed Solvent

The effects of the protic and aprotic polar solvents on the emission spectrum of the naphthalene-triethyl-amine system in THF were studied under conditions of steady-state illumination. The fluorescence spectrum of the naphthalene-triethylamine system consists of two emission bands, the fluorescence band of naphthalene(band A, 329 nm) and the emission band of the exciplex(band B, 468 nm). The intensities of both the emission bands decrease with increasing the solvent polarity. The intensity of band B also decreases due to the hydrogen-bonding interaction between triethylamine and protic solvent, while that of band A increases. It is thus suggested that the quenching of naphthalene fluorescence by triethylamine in THF occurs through the charge transfer and electron transfer reactions. The spectral changes upon the increase of solvent polarity can be explained by the dependences of the equilibrium constant between exciplex and ion-pair and the rate constant for the electron transfer reaction from triethylamine to the excited naphthalene on the relative permittivity of solvent. It is shown that the formation of intermolecular hydrogen-bonding between triethylamine and protic solvent suppresses the quenching reaction by the decrease in free amine. Acetonitrile has only a polar effect and trichloroacetic acid only a hydrogen-bonding(or protonation) effect, while alcohols have both the effects. The effects of alcohols could be separated into the effects of solvent polarity and intermolecular hydrogen-bonding interaction quantitatively.

Forming of A New Liquid Crystalline through Hydrogen Bonding

A stable Sc phase is formed through hydrogen bonding between side-chain aromatic acid groups of polysiloxane: Bending of polysiloxane with N-Acetyl Latimic acid (NAA) gives a chiral S c * phase; The influence of polymerism and hydrogen bond induction effect over mesophase is discussed. The influence of NAA over mesophase is studied.

Theoretical Studies on Intermolecular Hydrogen-bond Interactions between Hexamethylenetetramine and Nitric Acid

The structures of the complexes generated by hexamethylenetetramine and nitric acid have been fully optimized by B3LYP method at the 6-311＋＋G＊＊ and aug-cc-pVTZ levels. The intermolecular hydrogen-bonding interactions have been calculated by the B3LYP/6-311＋＋G＊＊, B3LYP/aug-cc-pVTZ, MP2（full）/6-311＋＋G＊＊ and CCSD（T）/6-311＋＋G＊＊ methods, respectively. The NBO （nature bond orbital）, AIM （atom in molecule）, temperature effect and solvation effect have been analyzed to reveal the origin of the interactions. The results indicate that the stable hydrogen-bonded complexes could be generated by hexamethylenetetramine and nitric acid. The interactions follow the order of （a）（e）（b）（c）（d）（f）（g）. The C–N bonds which are adjacent to the methylene involving the hydrogen bonds tend to break in the chemical reaction. Due to the exothermic process, low temperature is conducive to the formation of the composition, which tallies with the experimental result.

Role of hydrogen bonding in solubility of poly(N-isopropylacrylamide) brushes in sodium halide solutions

By employing molecular theory, we systematically investigate the shift of solubility of poly（N-isopropylacrylamide）（PNIPAM） brushes in sodium halide solutions. After considering PNIPAM–water hydrogen bonds, water–anion hydrogen bonds, and PNIPAM–anion bonds and their explicit coupling to the PNIPAM conformations, we find that increasing temperature lowers the solubility of PNIPAM, and results in a collapse of the layer at high enough temperatures. The combination of the three types of bonds would yield a decrease in the solubility of PNIPAM following the Hofmeister series： Na Cl＆gt;Na Br＆gt;Na I. PNIPAM–water hydrogen bonds are affected by water–anion hydrogen bonds and PNIPAM–anion bonds. The coupling of polymer conformations and the competition among the three types of bonds are essential for describing correctly a decrease in the solubility of PNIPAM brushes, which is determined by the free energy associated with the formation of the three types of bonds. Our results agree well with the experimental observations, and would be very important for understanding the shift of the lower critical solution temperature of PNIPAM brushes following the Hofmeister series.

Hydrogen Bonding in Thermoplastic Polyurethane Elastomers:IR Thermal Analysis

The hydrogen bond percentage and its temperature dependence of the three TPU samples synthesized from polytetrahydrofuran, 4,4'-diphenylmethane diisocyanate, N -methyl diethanol amine or 1,4-butane diol were studied by means of IR thermal analysis. The enthalpy and the entropy of the hydrogen bond dissociation were determined by the Van't Hoff plot.

Theoretical Investigations into the Intermolecular Hydrogen-bonding Interactions between Azacyclopentane-2-one and N-Methylol Ethanone

The structures of the complexes formed between N-methylol ethanone （model molecule of ceramide） and azacyclopentane-2-one （the model molecule of azone） have been fully optimized at the B3LYP/6-311＋＋G＊＊ level. The intermolecular hydrogen bonding interaction energies have been calculated by using the B3LYP/6-311＋＋G＊＊, B3LYP/6-311＋＋G（2df,2p）, MP2（full）/6-311 ＋＋G＊＊ and MP2（full）/6-311 ＋＋G（2df,2p） methods, respectively. The results show that strong O-H…O=C, N-H…O=C and C-H…O=C hydrogen bonds could exist between azacyclopentane-2-one and N-methylol ethanone. The formation of the complexes might change the conformation of ceramide molecule and thus cause better percutaneous permeation for the drugs. This is perhaps the origin of the permeation enhances the activity of azone for medicament, as is in accordance with the experimental results. The hydrogen-bonding interactions follow the order of （a） 〉 （c） 〉 （b） 〉 （d） 〉 （g） ≈ （e） ≈ （i） 〉 （h） 〉 （f）. The analyses of frequency, NBO, AIM and electron density shift are used to further reveal the nature of the complex formation. In the range of 263.0- 328.0 K, the complex is formed via an exothermic reaction, and the solvent with lower temperature and dielectric constant is favorable to this process.

Theoretical Studies on the Hydrogen Bonds of Different Position Action Mechanisms of Thymine with Uracil

In this research, the hydrogen bonds Y···H-X （X = C, N; Y = N, O） of thymine and uracil have been theoretically studied. The results show that hydrogen bond leads to bond length elongation and stretches the frequency red-shift of N-H···Y. Meanwhile, the C-H···O bonds shorten and stretch the frequency blue-shift. They all belong to traditional hydrogen bonds. The intermolecular charge transfer caused by the intermolecular hyperconjugation s＊（N–H） → n（Y） and intramolecular charge redistribution by intramolecular hyperconjugation σ（C-H） →σ＊（C-N） play important roles in the formation of hydrogen bonds. According to thejudgment standards proposed by Bader and Popelier, these hydrogen bonds have typical electron density topological properties. Electrostatic surface potential （ESP） is a useful physicochemical property of a molecule that provides insights into inter- and intramolecular associations, as well as the prediction of likely sites of electrophilic and nucleophilic metabolic attack.

POLYMER NETWORK-POLY(ETHYLENE GLYCOL)COMPLEXES WITH SHAPE MEMORY EFFECT

The complexes of poly(methacrylic acid-co-methyl methacrylate) network with poly(ethylene glycol) stabilized byhydrogen bonds were prepared. By introducing the poly(ethylene glycol), a large difference in storage modulus below andabove the glass transition temperature occurred and the complexes exhibited shape memory behaviors. The morphology ofcomplexes was studied by using DSC, WAXD, and DMA. The results indicate that the fixed phase of this kind of novelshape memory materials is the network, and the reversible phase is the amorphous state of PEG:PMAA complex phase. Theshape recoverability almost reaches 100%. This type of complexes can be regarded as a novel shape memory network.

Solvent effects on structure and optical properties of a D-π-A azobenzene dye

Time-dependent hybrid density functional theory in combination with Onsager reaction field model and super-molecular model has been applied to study solvent effects on the geometrical and electronic structures, as well as one/two-photon absorption properties, of 4-（N-（2-hydroxyethyl）-N-methyl）-amino-4＇-nitroazobenzene. It is found that the short-range interaction has a large effect on the electronic structure of the solute molecule, namely, large red-shift of the maximum one-photon absorption is induced by hydrogen bonding. The solute molecule has a large two-photon absorption cross section, which is enhanced by the solvent effect. The computational results are in good agreement with measurements.

基于酰基氨基脲和脲键协同作用的自愈合聚脲材料的制备及性能

[目的]制备具有优异力学性能和室温自愈合能力的材料具有极大的挑战性。[方法]以间苯二甲酰肼(IPDH)和硫脲为扩链剂,通过在聚合物硬段中引入酰基氨基脲和脲键基团来制备室温自愈合聚脲材料,分析了不同氢键密度下聚合物的化学结构、热学性能、力学性能和自愈合性能。[结果]以IPDH与硫脲的物质的量比3∶2所制备的材料显示了较好的综合力学性能:拉伸强度19.33 MPa,断裂伸长率929.6%,韧性52.69 MJ/m^(3)。聚合物中存在的多种氢键作用赋予了材料优异的自愈合能力。断裂试样经25℃修补5 h后断裂面基本消失,36 h后拉伸强度和断裂伸长率均恢复了至少80%。[结论]该材料可以在温和的条件下愈合,在智能保护材料方面有潜在的应用前景。

不同含氧官能团对煤润湿性影响的分子动力学模拟研究

为了探究不同含氧官能团对煤润湿性的影响规律,基于分子动力学(molecular dynamics,MD)理论,构建4个不同含氧官能团模拟系统(—COOH、—OH、—CO及—OCH 3),通过模拟接触角、分子相对体积分数、径向分布函数及相互作用能结果,详细分析含氧官能团对煤润湿性的影响规律。研究结果表明:模拟平衡后,在—COOH体系中水团簇的接触角为18.65°,相互作用能为-1049.19 kcal/mol,并形成371.64个氢键。在—OH体系中水团簇的接触角为25.37°,相互作用能为-563.83 kcal/mol,并形成178.03个氢键。在—CO体系中水团簇的接触角为30.10°,相互作用能为-444.25 kcal/mol,并形成58.34个氢键。在—OCH 3体系中水团簇的接触角为59.96°,相互作用能为-149.00 kcal/mol,并形成13.25个氢键。水团簇与不同含氧官能团体系的接触角越小,形成的氢键越多,相互作用能绝对值越大,对煤亲水性增强作用越好,这与分子相对体积分数和径向分布函数分析结果一致;不同含氧官能团对煤亲水性增强作用排序为—COOH>—OH>—CO>—OCH 3。研究结果可为研究煤表面润湿性及其应用提供相关参考。

线性氨基醇分子内氢键相互作用的溶剂效应

采用受激拉曼光谱技术测量4种线性氨基醇NH_(2)(CH_(2))_nOH(n=2,3,4,5)的气相拉曼光谱,同时采用自发拉曼光谱技术测量其液相拉曼光谱.结果表明:气相状态下,除n=5外,n=2,3,4的线性氨基醇分子中观察到显著的O—H…N分子内氢键相互作用;在纯液相和水溶液(摩尔分数为0.5)状态下,由于分子间氢键相互作用的竞争,4种线性氨基醇的分子内氢键相互作用均消失;在非极性CCl4溶液(摩尔分数为0.001)中,除n=2中可观察到微弱的分子内氢键外,其余线性氨基醇中均未观察到分子内氢键相互作用.因此,不管极性还是非极性溶剂均显著影响线性氨基醇的分子内氢键相互作用.

Density Functional Theoretical Studies on Effect of Intramolecular Hydrogen Bonds on Reduction of Nitrophenols

Intramolecular hydrogen bonds（IMHBs） can lead to different physicochemical characteristics of nitro- phenols（NPs） that determine their environmental behavior. In the present work, to reveal the relationship between IMHB and nitrophenol reduction, the effects of IMHB on the molecular geometries and properties of a series of ni- trophenols were investigated with density functional theory（DFT） calculations. The results of the geometry optimiza- tion and atoms-in-molecules（AIM） analysis indicate relatively strong IMHBs in ortho-substituted nitrophenols, whose stability could be significantly improved. In comparing the ELUMO and adiabatic electron affinities（AEA） of the nitrophenol isomers, the presence of IMHBs benefited the reductive degradation of NPs, consistent with a previous study. To gain an insight into the effect mechanism of IMHBs on the reductive degradation behavior of these mole- cules, the condensed electrophilicity Fukui index（f-）, natural charges and Wiberg bond orders of these nitrophenol isomers were calculated. The calculations indicate that the electrophilic reactivity activity of the O atom on the nitro group could be significantly improved due to the formation of IMHBs, which results in the enhanced reductive degradation of ortho-substituted NPs.

Substituent Effects on the Hydrogen Bonding between 4-Substituted Phenols and HF,H_2O,NH_3

Density function theory UB3LYP/6-31+g(d) calculations were performed to study the hydrogen bonds between para -substituted phenols and HF,H_2O,or NH_3. It revealed that many properties of the non-covalent complexes,such as the interaction energies,donor-acceptor distances,bond lengths and vibration frequencies,showed well-defined substituent effects. Therefore,from the substituent effects not only the mechanism of a certain non-covalent interaction can be better understood,but also the interaction energies and structures of a certain non-covalent complex,which otherwise might be very hard or resource-consuming to estimate,can be easily predicted.

Substituent Effects on the Blue-Shifting Hydrogen Bonds between X-C≡C-CF_2-H and Water

MP2/6-31 + g(d) calculations were performed verifying the existences ofblue-shifting X - C ≡ C - CF_2 - H···OH_2 hydrogen bonds. Detailed analyses revealed that theinteraction energy and donor-acceptor distance had good correlations with the substituent Hammettconstants. However, the extent of C―H bond contraction and the blue shift of the C―H stretchingvibration did not show any good correlation with the traditional substituent constants, indicatingthat certain more complicated mechanisms might be involved in the present systems. Nevertheless, itwas found that highly electron-withdrawing susbtituents were not favorable to the C―H bondcontraction, and it was suggested that the attractive interaction between water and the carbon of -CF_2H probably played an important role in the blue shift.

含硫苯衍生物对发光细菌的毒性效应及其定量结构活性相关分析

利用发光细菌法测定了29种氯取代和硝基取代的苯硫(砜、亚砜)基乙酸酯的毒性,通过定量结构活性相关(QSAR)分析发现:此类化合物的毒性主要与其取代基的电荷效应相关,电荷的区域分布对化合物的毒性效应有重要影响.推测该化台物的毒性机理是毒物分子与发光反应中的主要辅酶FMNH_2形成了氢键.还发现:在这类链状毒物分子中,远离活性中心一端的基团具有脱毒作用.

N,N-二甲基乙酰胺与醇分子间相互作用的理论研究

采用密度泛函理论在B3LYP/6-311+G*水平上对乙醇、丙醇、丁醇、戊醇与N,N-二甲基乙酰胺形成的1∶1氢键复合物进行计算研究.结果表明:醇与N,N-二甲基乙酰胺形成的复合物存在强的氢键,表现为羰基氧原子的孤对电子与醇羟基反键σ轨道的相互作用.振动分析显示,分子间C=O…H—O氢键的形成使C=O和H—O伸缩振动频率明显红移.溶剂对氢键产生较大的影响,随着溶剂极性的增加,复合物氢键有蓝移趋势.