A TD-DFT study on the hydrogen bonding of three esculetin complexes in electronically excited states: strengthening and weakening

Time-dependent density functional theory (TD-DFT) method was used to study the excited-state hydrogen bonding of three esculetin complexes formed with aprotic solvents. The geometric structures, molecular orbitals (MOs), electronic spectra and the infrared (IR) spectra of the three doubly hydrogen-bonded complexes formed by esculetin and aprotic solvents dimethylsulfoxide (DMSO), tetrahyrofuran (THF) and acetonitrile (ACN) in both ground state S(0) and the first singlet excited state S(1) were calculated by the combined DFT and TD-DFT methods with the COSMO solvation model. Two intermolecular hydrogen bonds can be formed between esculetin and the aprotic solvent in each hydrogen-bonded complex. Based on the calculated bond lengths of the hydrogen bonds and the groups involved in the formation of the intermolecular hydrogen bonds in different electronic states, it is demonstrated that one of the two hydrogen bonds formed in each hydrogen-bonded complex is strengthened while the other one is weakened upon photoexcitation. Furthermore, it is found that the strength of the intermolecular hydrogen bonds formed in the three complexes becomes weaker as the solvents change from DMSO, via THF, to ACN, which is suggested to be due to the decrease of the hydrogen bond accepting (HBA) ability of the solvents. The spectral shifts of the calculated IR spectra further confirm the strengthening and weakening of the intermolecular hydrogen bonds upon the electronic excitation. The variations of the intermolecular hydrogen bond strengths in both S(0) and S(1) states are proposed to be the main reasons for the gradual spectral shifts in the absorption and fluorescence spectra both theoretically and experimentally.     

Charge Transfer Complexes of Some Heterocyclic Aromatic Amines with π‐Organic Acceptors in Polar Solvents

A conductometric titration technique has been used to investigate the electron transfer activity of CT molecular complexes formed by arylazopyrimidine and naphthylazopyrimidine derivatives as donors and the organic π‐acceptors p‐nitroaniline, p‐chloroaniline, p‐bromoaniline, anthraquinone, picric acid, α‐nitroso‐β‐naphthol, p‐hydroxybenzaldehyde and maleic anhydride. The study was performed at different degree of temperature and in three different polar solvents namely N,N‐dimethylformamide (DMF), acetonitrile (ACN) and dimethylsulfoxide (DMSO). The stoichiometric ratios of these complexes were found to be 1:1. The dissociation constant (ασ_M) values of the formed complexes have been calculated, and the effects of solvents as well as types of electron donors on their conductance σ_p‐values have been examined.     

Nucleophilic Substitution on Porphyrin Ring： Synthesis of 2-（2-Hydroxynaphthyl）-5,10,15,20-tetraphenylporphyrin

The reactions of 2-nitro-5,10,15,20-tetraphenylporphyrin （1） and its Ni （Ⅱ） （2）, Cu （Ⅱ） （3）, Zn （Ⅱ） （4） complexes with sodium 2-naphthoxide have been investigated in different solvents for preparing 2-substituted porphyrins. 2-（2-Hydroxynaphthyl）-5,10,15,20-tetraphenyl porphyrin （5） and its Ni （Ⅱ） （6）, Cu （Ⅱ） （7）, Zn （Ⅱ） （8） complexes were obtained in 72%, 78%, 81% and 65% yields in 2-naphthol at 150 ℃ respectively. The same products were also obtained in other protic solvents such as diglycol and diglycol monomethyl ether. When the reactions proceeded in aprotic solvent DMF at 150 ℃, besides 5 （70%）, 6 （34%）, 7 （54%） and 8 （50%）, the corresponding 2-（2-naphythoxy）-5, 10,15,20-tetraphenylporphyrin （9）, and its Ni （Ⅱ） （10）, Cu （Ⅱ） （11）, Zn （Ⅱ） （12） complexes were also obtained in minor, 40%, 18% and 2% yields respectively, but only 5, 6, 7, 8 were found at room temperature in DMF or DMSO. These reactions axe much faster than those of 1-4 with sodium phenoxide. The formation of C-coupling products 5-8 was proposed via SRN 1 mechanism.     

一步法合成高T_g可溶含偶氮三嗪发色团的新型侧链含氟聚酰亚胺

采用一步法合成了一系列侧链含偶氮三嗪发色团的新型含氟聚酰亚胺FPI(x),并研究其溶解性能、热性能以及光学性能.该系列聚酰亚胺具有优良的溶解性能,不仅溶于NMP,DMAc,DMF,DMSO等强极性非质子性溶剂,而且还溶于THF和乙二醇单甲醚等低沸点溶剂.FPI(x)系列共聚聚酰亚胺具有较高的玻璃化转变温度(T_g,在544～562K之间),且与主链中染料发色团的含量无关.所有聚酰亚胺都表现出优良的高温稳定性,其5%热失重温度(T₅)比T_g高出100K以上,基本能满足电场极化对聚合物材料热稳定性的要求.另外,FPI(x)系列聚酰亚胺的紫外截止吸收波长小于500nm,即在大于500nm波长范围内基本透明.其面内折光指数n_TE随着染料发色团含量的增加而逐渐增加.     

Synthesis and characterization of thermally stable sulfonated polybenzimidazoles obtained from 3,3′‐disulfonyl‐4,4′‐dicarboxyldiphenylsulfone

A novel sulfonated aromatic diacid, 3,3′‐disulfonyl‐4,4′‐dicarboxyldiphenylsulfone (DSDCDPS), was successfully synthesized from 4,4′‐dimethyldiphenylsulfone by sulfonation and further oxidation. A series of sulfonated polybenzimidazoles (sPBI‐SS) with various sulfonation degrees was prepared from DSDCDPS, 4,4′‐sulfonyldibenzoic acid and 3,3′‐diaminobenzidine by solution copolycondensation in poly(phosphoric acid). The chemical structure of the resulting sPBI‐SS was confirmed by FTIR and ¹H NMR. The DSDCDPS‐based sPBI‐SS with the number‐average molecular weights of 32,000–55,000 were easy to dissolve in polar aprotic solvents such as DMF, DMSO, and DMAc, and could be cast into transparent, tough, and flexible membranes. The membranes presented good thermal stabilities (5% weight loss temperatures higher than 430 °C), and the thermal degradation activation energies of the sulfonic group of sPBI‐SS40 evaluated under N₂ by both Ozawa and Kissinger methods were 266.06 and 264.79 kJ/mol, respectively. The membranes also exhibited high storage moduli, glass transition temperatures (above 238 °C) and tensile strengths (～80 MPa), in addition to water uptakes (22.3–25.2%) and low swelling degrees (<14.0%). © 2005 Wiley Periodicals, Inc. J Polym Sci A: Polym Chem 43: 4363–4372, 2005     

Solvent effects in the absorption spectra of the Ninhydrin chromophore

Visible spectra of the Ninhydrin chromophore, Ruhemann's purple, were studied in dimethyl sulfoxide (DMSO), formamide, N, N-dimethylformamide (DMF), and pyridine, as well as in mixed aqueous-nonaqueous solvent media. Large differences in both the position of absorption maxima and extinction coefficients for the two bands in the visible spectra in the various solvent media were observed. Both the absorption maxima and the extinction coefficients of the Ninhydrin chromophore were a linear function of the composition of dimethyl sulfoxide-H₂O solvent media. The experimental evidence allows predictions of values for the two absorption maxima of Ruhemann's purple as a function of the nature of the solvent medium. In nonaqueous aprotic solvents (i.e., DMSO and DMF), the maxima should be near 605 and 420 mμ; in nonaqueous aprotic solvents capable of undergoing charge-transfer interactions (i.e., pyridine), near 550 and 420 mμ; and in nonaqueous protic solvents (i.e., formamide), near 575 and 410 mμ. The maxima in aprotic media will be displaced to about 575 mμ (higher wavelength band) and 410 mμ (lower wavelength band) on dilution with protic solvents.     

Novel fluorinated poly(aryl ether)s derived from 1,2-bis(4-(4-fluorobenzoyl)phenoxy)-hexafluorocyclobutane

Two novel poly(aryl ether)s were prepared from 1,2-bis(4-(4-fluorobenzoyl)-phenoxy)-hexafluorocyclobutane and aromatic bisphenols by the aromatic nucleophilic substitution reaction in a polar aprotic solvent. These polymers have good thermal stability up to 341 °C with 10% weight loss in inert atmosphere and good solubility in common organic solvents such as THF, DMAc, DMF and DMSO.     

靛蓝-F-组合探针光度法检测非质子有机溶剂中的微量水

以靛蓝-F^-为组合探针,建立了非质子有机溶剂(DMSO、THF、DMF、二恶烷、乙腈)中微量水的比色检测新方法。结果表明,F^-加入靛蓝溶液后体系的颜色由蓝色变为黄绿色,进一步加入微量水之后,体系从黄绿色又变回蓝色,因而可作为一种变色探针实现对有机溶剂中微量水的裸眼识别检测。体系具有较高灵敏度,对DMSO、THF、DMF、二恶烷及乙腈中微量水的检测限分别为0.022%、0.043%、0.016%、0.34% 和0.015%。该方法实验操作简便、快速、灵敏、安全。实验结果表明,靛蓝与F^-的结合比为1:2。利用核磁滴定方法对机理进行了探讨。     

Characterization of superoxide dismutase 1 (SOD‐1) by electrospray ionization‐ion mobility mass spectrometry

In this paper, we report nano‐electrospray ionization‐ion mobility mass spectrometry (nano‐ESI‐IM‐MS) characterization of bovine superoxide dismutase (SOD‐1) and human SOD‐1 purified from erythrocytes. SOD‐1 aggregates are characteristic of amyotrophic lateral sclerosis (ALS), a fatal neurodegenerative disease in humans that could be triggered by dissociation of the native dimeric enzyme (Cu₂,Zn₂‐dimer SOD‐1). In contrast to ESI‐MS, nano‐ESI‐IM‐MS allowed an extra dimension for ion separation, yielding three‐way mass spectra (drift time, mass‐to‐charge ratio and intensity). Drift time provided valuable structural information related to ion size, which proved useful to differentiate between the dimeric and monomeric forms of SOD‐1 under non denaturing conditions. In order to obtain detailed structural information, including the most relevant post‐translational modifications, we evaluated several parameters of the IM method, such as sample composition (10 mM ammonium acetate, pH 7) and activation voltages (trap collision energy and cone voltage). Neutral pH and a careful selection of the most appropriate activation voltages were necessary to minimize dimer dissociation, although human enzyme resulted less prone to dissociation. Under optimum conditions, a comparison between monomer‐to‐dimer abundance ratios of two small sets of blood samples from healthy control and ALS patients demonstrated the presence of a higher relative abundance of Cu,Zn‐monomer SOD‐1 in patient samples. Copyright © 2013 John Wiley & Sons, Ltd.     

Radical polymerization of new functional monomer: Methacryloyl isocyanate containing 4‐chloro‐1‐phenol

New functional monomer methacryloyl isocyanate containing 4‐chloro‐1‐phenol (CPHMAI) was prepared on reaction of methacryloyl isocyanate (MAI) with 4‐chloro‐1‐phenol (CPH) at low temperature and was characterized with IR, ¹H, and ¹³C‐NMR spectra. Radical polymerization of CPHMAI was studied in terms of the rate of polymerization, solvent effect, copolymerization, and thermal properties. The rate of polymerization of CPHMAI has been found to be smaller than that of styrene under the same conditions. Polar solvents such as dimethylsulfoxide (DMSO) and N,N‐dimethyl formamide (DMF) were found to slow the polymerization. Copolymerization of CPHMAI (M₁) with styrene (M₂) in tetrahydrofuran (THF) was studied at 60°C. The monomer reactivity ratio was calculated to be r₁ = 0.49 and r₂ = 0.66 according to the method of Fineman—Ross. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 469–473, 2000     

Ultrafast vibrational dynamics of SCN(-) and N3(-) in polar solvents studied by nonlinear infrared spectroscopy

In this paper, we report on our investigation into the vibrational dynamics of the antisymmetric stretching modes of SCN(-) and N(3)(-) in several polar solvents. We used an infrared (IR) pump-probe method to study orientational relaxation processes. In two aprotic solvents (N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO)), the anisotropy decay shows a bimodal feature, whereas in other solvents the anisotropy decay can be fitted well by a single exponential function. We consider that the relative contribution of fast-decaying components is smaller in the other solvents than in DMF and DMSO. We discuss the possible origins of the different anisotropy decay behavior in different solvents. From the three-pulse IR photon echo measurements for SCN(-) and N(3)(-), we found that the time-correlation functions (TCFs) of vibrational frequency fluctuations decay on two different time scales, one of which is less than 100 fs and the other is approximately 3-6 ps. In aprotic solvents, the fast-decaying components of the TCFs on a <100 fs time scale play an important role in the vibrational frequency fluctuation, although the contribution of collective solvent reorganization in aprotic solvents was clearly observed to have small amplitudes. On the other hand, we found that the amplitude of components that decay in a few picoseconds and/or the constant offset of the TCF in protic solvents is relatively large compared with that in aprotic solvents. With the formation and dissociation of hydrogen bonds between ion solute and solvent molecules, the spectra of different solvated species are exchanged with each other and merged into one band. We considered that this exchange may be an origin of slow-decaying components of the TCFs and that the decay of the TCFs corresponds to the time scales of the exchange for protic solvents such as formamide. The mechanism of vibrational frequency fluctuations for the antisymmetric stretching modes of SCN(-) and N(3)(-) is discussed in terms of the difference between protic and aprotic solvents.     

Kinetics and reactivity of substituted anilines with 2‐chloro‐5‐nitropyridine in dimethyl sulfoxide and dimethyl formamide

The kinetics of the reaction of substituted anilines with 2‐chloro‐5‐nitropyridine were studied in dimethyl sulfonide (DMSO) and dimethyl formamide (DMF) at different amine concentrations and temperatures in the range 45–60°C. In both solvents the reaction was not a base‐catalyzed one. A plot of ΔH^# versus ΔS^# for the reaction in DMSO and DMF gave good straight lines with isokinetic temperatures 128°C and 105°C, respectively. Good linear relationships were obtained from the plots of log k₁ against σ° values at all temperatures with negative ρ values (?1.63 to ?1.28 in DMSO) and (?1.26 to ?0.90 in DMF). © 2002 Wiley Periodicals, Inc. Int J Chem Kinet 34: 645–650, 2002     

Infrared spectra of M+NO 3 − contact ion pairs in aprotic solvents and matrix isolated in the corresponding glasses

Studies of the vibrational spectra of matrix-isolated M⁺NO ₃ ^– ion pairs have been extended to glassy aprotic solvents. The deuterated form of the solvents DMSO, THF, and ACN have windows through the 7- nitrate ionv ₃(e) mode infrared region, so it was possible to clearly observe the splitting of the degeneracy of this mode,v ₃, produced by the contacting, but solvated, alkali metal cation. Primary attention has been directed to the extent to which this splitting is reduced relative to the argon matrix values. This reduction, which reflects electron-density transfer from the solvating molecules to the ion pairs, is comparable to that observed for H₂O and NH₃ matrices as the splitting is reduced to 20–35% of the argon-matrix values. The extent of reduction ofv ₃ for the different solvents has been related to Gutmann's donicity number scale with the correlation holding well for solvent molecules of comparable size, DMSO, THF and DMF, but breaking down for the smaller linear ACN, apparently because of more molecules in the cation solvation sphere. The matrix data have also been used, through comparison with spectra for saturated liquid solutions of Li⁺NO ₃ ^– , to show that the contact ion pair is the dominant species in liquid THF and ACN, whereas the ions are largely solvent separated in DMSO.     

Mechanism of charge-transfer polymerization. V. Photopolymerization and photocyclodimerization of N-vinylcarbazole in the N-vinylcarbazole–oxygen–solvent system

Photochemical reactions of N-vinylcarbazole (VCZ), studied in various solvents, were profoundly influenced by the atmosphere. In the deaerated system radical polymerization of VCZ occurred in various solvents, e.g., tetrahydrofuran, acetone, ethyl methyl ketone, acetonitrile, methanol, sulfolane, N,N-dimethylformamide (DMF), or dimethyl sulfoxide (DMSO). By contrast, when dissolved oxygen was present, cyclodimerization of VCZ occurred exclusively to give trans-1,2-dicarbazole-9-yl-cyclobutane in such polar, basic solvents as acetone, ethyl methyl ketone, acetonitrile or methanol. In stronger basic solvents, i.e., sulfolane, DMF, or DMSO, simultaneous radical polymerization and cyclodimerization of VCZ proceeded, the ratio of the cyclodimerization to the radical polymerization decreasing in the order, sulfolane > DMF > DMSO. In dichloromethane, on the other hand, cationic polymerization of VCZ occurred irrespective of the atmosphere. It is suggested that oxygen acts as an electron acceptor to the excited VCZ, electron transfer occurring in polar solvents from the excited VCZ to oxygen to give transient VCZ cation radical. The effect of solvent basicity on the photocyclodimerization of VCZ is discussed.     

Main‐chain viologen polymers with triflimide counterion exhibiting lyotropic liquid‐crystalline properties in polar organic solvents

The solution‐phase behavior of three main‐chain viologen polymers, which are composed of isomeric xylyl units and triflimide as a counterion, was studied in methanol, dimethylformamide, acetonitrile, and dimethyl sulfoxide as solvents microscopically under crossed polarizers. Each of them exhibited a lyotropic lamellar phase in both polar protic and aprotic solvents. Their C^* for the formation of biphasic solutions (1–5 wt %) and concentrations (20–30 wt %) for the lyotropic solutions in methanol was much lower than those in polar aprotic solvents (20–71 and 60–81 wt %, respectively). Their high solubility, high C^* for the formation of biphasic solutions, and high concentrations for the formation of lyotropic solutions in polar aprotic solvents were related to the significant reduction of strong ionic interactions between triflimide and 4,4′‐bipyridinium ions in each of these viologen polymers. They were the first examples of viologen polymers that exhibited a lyotropic phase in polar aprotic solvents. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2015–2024, 2002     

Soluble poly(amide–imide)s prepared by one‐pot solution condensation

A new one‐pot procedure for imide–acid monomer synthesis and polymerization is reported for four new poly(amide–imide)s. Bisphenol A dianhydride (BPADA) was reacted with twice the molar amount of 3‐aminobenzoic acid (3ABA) or 3‐amino‐4‐methylbenzoic acid (3A4MBA) in 1‐methyl‐2‐pyrrolidinone (NMP) and toluene mixture, and the amic acid intermediates cyclized in solution to give two diimide‐containing dicarboxylic acid monomers. Without isolation, the diacid monomers were then polymerized with either 1,3‐diaminomesitylene (DAM) or 1,5‐diaminonaphthalene (1,5NAPda) using triphenyl phosphite‐activation to give a series of four soluble poly(amide–imide)s, PAI. Isolation and purification of the dicarboxylic acid monomers was not necessary for formation of high molecular weight polymers as indicated by intrinsic viscosities of 0.64–1.04 dL/g determined in N,N‐dimethylacetamide (DMAc). All of the PAI were soluble in polar aprotic solvents such as NMP, DMAc, and dimethyl sulfoxide (DMSO). Glass transition temperatures ranged from 243 to 279°C by DSC, and 5% weight loss temperatures were above 400°C in both air and nitrogen. Flexible films cast from DMAc were light yellow, transparent, and tough. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 1183–1188, 1999     

Solubility and solution thermodynamics of 2, 6-bis (4-hydroybenzylidene) cyclohexanone in pure and binary solvents at various temperatures

Solubility of 2, 6-bis (4-hydroxybenzylidene) cyclohexanone (BHBC) in pure solvents such as 1,4-dioxane, methanol, 1-butanol, 1-propanol, ethyl acetate, acetone, tetrahydrofuran (THF), glacial acetic acid, dimethyl sulphoxide (DMSO) and binary solvents dimethyl formamide (DMF) and (1-Propanol + Tetrahydrofuran) were investigated by gravimetric method at different temperature range. The experiment solubility increases with increase in temperature in both pure and binary solvents. The Maximum solubility is found in DMF at 328.15 K and for binary solvent mixture i.e. 1-propanol and THF (0.9 mol fraction) it was maximum at 318.15 K. Further modified Apelblate and Buchowski-Ksiazczak models were used for the theoretical calculation of solubility of BHBC in pure as well binary solvents. A satisfactory correlation of these models with experimental data was observed. The solution thermodynamics parameters like enthalpies, Gibb's free energy of dissolution and entropy of solutions were calculated using Van't Hoff and Gibb's equation, which reveals the solvation mechanism is non-spontaneous and entropy driven.     

共缩聚型可溶性聚酰亚胺的微波辐射合成

以均苯四甲酸酐(PMDA)、3,3′,4,4′-二苯酮四羧酸二酐(BTDA)和甲苯2,4-二异氰酸酯(TDI)为单体,微波辐射低温溶液聚合生成一种共缩聚聚酰亚胺(PI).通过特性黏度([η])、红外光谱(FT-IR)、热失重分析(TGA)和X衍射分析(XRD)等对聚合物进行了一系列的结构表征和性能测试.结果表明,微波辐射溶液聚合能够提高PI的特性黏数及产率,微波的引入大大缩短了反应时间;FT-IR表明,在1779cm-1和1726cm-1处观察到聚酰亚胺特征峰;TGA表明,PI在氮气中520℃左右开始降解,10%热失重温度为585℃;溶解性测试表明,PI可以溶解在强极性非质子溶剂中,如DMF,DMSO,DMAc及NMP等,甚至部分溶解在THF中.     

Thermally stable polymers based on 1,3,4-oxadiazole rings

<正>In the present work,new thermally stable polymers containing 1,3,4-oxadiazole units have been synthesized through Huisgen reaction of the aromatic bis-tetrazole compounds with the aromatic/aliphatic bis-acid chlorides in pyridine as solvent.The obtained polymers are insoluble or slightly soluble in polar aprotic solvents such as DMSO and DMF. Thermal analyses of the polymers using DSC and TGA techniques showed that the polymers had improved thermal stabilities.The model reaction was also investigated and the resulting bis-l,3,4-oxadiazole compounds were characterized by conventional spectroscopic methods.     

Semidilute solution structure of cellulose in an ionic liquid and its mixture with a polar organic co‐solvent studied by small‐angle X‐ray scattering

Structural and thermodynamic properties of cellulose solutions in the ionic liquid 1‐ethyl‐3‐methylimidazolium acetate (EMIMAc) and its binary mixtures with N,N‐dimethyl formamide (DMF) are studied by small‐angle X‐ray scattering (SAXS). These measurements indicate molecular dissolution of the cellulose chains without any significant aggregation. The power–law relationships of the evaluated correlation length and osmotic modulus to concentration exhibit exponents of ?0.76 and 2.06 for EMIMAc and ?0.80 and 2.14 for DMF/EMIMAc solvent mixture, respectively. Thus, these solvents can be considered to be good solvents for cellulose. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55 , 888–894