共查询到20条相似文献,搜索用时 15 毫秒
1.
Remon M. Zaki Adel M. Kamal El-Dean Jehan A. Mickey Nermin A. Marzouk Rasha H. Ahmed 《合成通讯》2017,47(24):2406-2416
Ethyl 4,6-dimethyl-3-(pyrrol-1-yl) selenolo[2,3-b]pyridine-2-carboxylate (2) was synthesized by the reaction of previously prepared ethyl 3-amino-4,6-dimethyl selenolo[2,3-b]pyridine-2-carboxylate (1) with 2,5-dimethoxytetrahydrofuran in acetic acid. The pyrrolyl ester (2) was converted into the corresponding carbohydrazide 3 which reacted with acetyl acetone, aromatic aldehydes, carbon disulfide in pyridine, and sodium nitrite to afford the corresponding dimethyl pyrazolyl 4, arylidene carbohydrazides 5a–d, oxadiazolyl thiole 6, and caboazide compound 8, respectively. The carboazide 8 reacted with different alcohols and amines to give the corresponding carbamates 9a–c and the aryl urea derivatives 10a–d. Heating of carboazide 8 in dry xylene afforded the pyridoselenolo-pyrrolopyrazinone 11. The latter compound was used as a versatile starting precursor for synthesis of other pyridoselenolo-pyrrolopyrazine compounds. The newly synthesized compounds and their derivatives were characterized by elemental analysis and spectroscopy (IR, 1H-NMR, and mass spectra). Some of the newly synthesized pyrrolyl selenolopyridine compounds showed remarkable antioxidant activity compared to ascorbic acid. 相似文献
2.
Dr. Amit Kumar Sarnali Sanfui Dr. Giuseppe Sciortino Prof. Jean-Didier Maréchal Prof. Eugenio Garribba Prof. Sankar Prasad Rath 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(35):7869-7880
cis and trans-copper(II) porphyrin dimers have been synthesized, in which two CuII porphyrin macrocycles are bridged through a rigid ethene linker for possible through-space and through-bond spin-couplings between the paramagnetic CuII centers. It has been found that the two macrocycles come closer after 1 e− oxidation, however, they move far apart upon further 1 e− oxidation leading to transformation of the cis to the trans isomer. Detailed investigations are performed here on the interactions between the two porphyrin macrocycles, between two unpaired spins of closely spaced CuII centers, and also between the unpaired spins of metal and porphyrin π–cation radicals. Spectroscopic investigations along with the X-ray structure of the 2 e−-oxidized complex displayed strong electronic communications through the bridge between two porphyrin π–cation radicals. The counterion I9− is stabilized in an unusual trigonal-pyramidal structure in the 2 e−-oxidized complex in which the central iodide ion is bound with four iodine (I2) molecules. Variable-temperature magnetic study revealed strong antiferromagnetic coupling between the two porphyrin π–cation radical spins (Jr–r) in the 2 e−-oxidized complex. DFT calculations suggest stabilization of the triplet state, which is also in good agreement with the experiment. Ab initio molecular dynamics allowed the variation of the structural details to be followed upon stepwise oxidations and also the final isomerization process including its associated energy barrier. 相似文献
3.
Ole Swang Knut Faegri Odd Gropen Ulf Wahlgren 《International journal of quantum chemistry》1996,57(1):105-111
The chemisorption of atomic hydrogen and oxygen on a cobalt surface has been studied on a five-atom cluster model using one-electron effective core potential (1e−ECP) and all-electron calculations at the ab initio SCF and MCPF levels. Also, density functional calculations have been carried out. The different approaches are evaluated. The 1e−ECP has been compared to similar ECPS for nickel and copper. Our results indicate that this approach is valid also for cobalt. Different contributions to the cluster-adsorbate bonding energy are discussed. © 1996 John Wiley & Sons, Inc. 相似文献
4.
Elisabeth Parman Dr. Märt Lõkov Robert Järviste Dr. Sofja Tshepelevitsh Dr. Nikolay A. Semenov Dr. Elena A. Chulanova Dr. Georgy E. Salnikov Dr. Darya O. Prima Dr. Yuri G. Slizhov Prof. Dr. Ivo Leito Prof. Dr. Andrey V. Zibarev 《Chemphyschem》2021,22(22):2329-2335
The influence of fluorination on the acid-base properties and the capacity of structurally related 6–5 bicyclic compounds – 1,3-benzodiazole 1 , 1,2,3-benzotriazole 2 and 2,1,3-benzoselenadiazole 3 to σ-hole interactions, i. e. hydrogen ( 1 and 2 ) and chalcogen ( 3 ) bondings, is studied experimentally and computationally. The tetrafluorination increases the Brønsted acidity of the diazole and triazole scaffolds and the Lewis acidity of selenadiazole scaffold decreases the basicity. Increased Brønsted acidity facilitates anion binding via the formation of hydrogen bonds; particularly, tetrafluorinated derivative of 1 (compound 4 ) binds Cl−. Increased Lewis acidity of tetrafluorinated derivative of 3 (compound 10 ), however, is not enough for binding with Cl− and F− via chalcogen bonds in contrast to previously studied Te analog of 10 . It is suggested that the maximum positive values of molecular electrostatic potential at the σ-holes, VS,max, can be a reasonable metric for design and synthesis of new anion receptors with selenadiazole-diazole/triazole hybrids as a special target. Related chlorinated compounds are also discussed. 相似文献
5.
The electronic structure and stability of pyrrolyl are investigated using CASSCF, CASPT2 and G2(MP2) techniques. The ground state of pyrrolyl is found to be 2A2, with five π-electrons, as in cyclopentadienyl. The computed N–H bond energy of pyrrole is 94.8 kcal mol−1, while the heat of formation ΔfH298o of pyrrolyl is deduced to be 70.5±1 kcal mol−1. The Arrhenius parameters of N–H and C–H bond fission in pyrrole and cyclopentadiene and hydrogen abstraction reactions (by hydrogen) were also computed, indicating that pyrrolyl forms predominantly by C–H bond fission of pyrrolenine rather than by direct N–H bond fission. 相似文献
6.
Remon M. Zaki Adel M. Kamal El-Dean Shaban M. Radwan Mokhtar A. Abd ul-Malik 《中国化学会会志》2020,67(4):658-673
In the present investigation, a simple and straightforward methodology for the preparation of novel bifunctional thienopyrazolopyrazines 4a–d has been reported. Synthesis of thieno or furopyrazolopyrazines 5a , b , e , f was achieved by the reaction of o-amino-esters 4a , b , e , f with 2,5-dimethoxytetrahydrofuran. The latter pyrrolyl derivatives 5a , b , e , f were used as starting intermediates for the synthesis of new pyrimido, pyrido, and pyrazino heterocycles fused to the thieno or furopyrazolopyrazine moiety. Furthermore, alkaline hydrolysis of the o-amino-ester 4a followed by acidification afforded the corresponding o-amino carboxylic acid 15 , which was used as a versatile precursor for the synthesis of other heterocyclic compounds fused to the thienopyrazolopyrazine ring system, namely: pyrimidine, oxazine, oxazepine, and pyridine derivatives 16–23 . The chemical structures of the synthesized compounds were confirmed on the basis of elemental and spectral analyses (Fourier-transform infrared spectroscopy [FT-IR], 1H nuclear magnetic resonance [NMR], and mass spectroscopy [MS] in addition to 13C NMR for some of them). Moreover, from the biological screening, we found that most of the tested compounds exhibited promising antifungal, antibacterial, and anti-inflammatory activities compared with the corresponding reference drugs. 相似文献
7.
Dr. Marcin Jasiński Katarzyna Szymańska Anita Gardias Dr. Damian Pociecha Dr. Hirosato Monobe Dr. Jacek Szczytko Prof. Piotr Kaszyński 《Chemphyschem》2019,20(4):636-644
A homologous series of disc-like 1,3,6-trisubstituted benzo[e][1,2,4]triazin-4-yls 1[n] was synthesized and their structural, thermal, optical, magnetic, and electric properties were investigated. The results demonstrate that all members of the series display a Colh phase with clearing temperatures depending on the length of the alkoxy chains at the N(1) position, hence the shape of the disc. Powder XRD and magnetic data indicate a gradual change in the column diameter and magnetic behavior in the series in transition from half-disc in 1[0] (antiferromagnetic interactions) to full-disc geometry in the 1[12] homologue (ferromagnetic interactions with J/kB=+7.5 K). Studies of binary systems revealed that a 1 : 1 mixture of 1[0] and 1[12] exhibits modest stabilization of the Colh phase with an expanded range, and magnetic behavior typical for 1[0] in the rigid phase obtained from the melt. Electric measurements demonstrated hole mobility of ∼10−3 cm2 V−1 s−1 and dark conductivity of ∼10−11 Scm−1 in the mixture and individual compounds. The latter is enhanced up to 4 times by simultaneous illumination with UV light. 相似文献
8.
Methyl 131‐(di)cyanomethylene‐pyropheophorbides were synthesized by Knoevenagel reactions of the corresponding 131‐oxo‐chlorins prepared from modifying chlorophyll‐a with malononitrile or cyanoacetic acid. Alternatively, methyl 131‐cyanomethylene‐pyropheophorbides were produced by Wittig reactions of 131‐oxo‐chlorins with Ph3P=CHCN. Self‐aggregation of zinc complexes of the semi‐synthetic chlorophyll derivatives possessing a hydroxy or methoxy group at the 31‐position was examined in 1%(v/v) tetrahydrofuran or dichloromethane and hexane by electronic absorption and circular dichroism spectroscopy. Although intermolecular hydrogen‐bonding between the 31‐hydroxy and 131‐oxo groups of bacteriochlorophylls‐c/d/e/f was essential for their self‐aggregation in natural light‐harvesting antenna systems (=chlorosomes), zinc 31‐hydroxy‐131‐di/monocyanomethylene‐chlorins self‐aggregated in the less/lesser polar organic solvents to form chlorosome‐like large oligomers in spite of lacking the 131‐oxo moiety as the hydrogen‐bonding acceptor. Zinc 31‐methoxy‐131‐dicyanomethylene‐chlorin gave similar self‐aggregates regardless of lack of both the 31‐hydroxy and 131‐oxo groups. The present self‐aggregation was ascribable to stronger coordination of the 31‐oxygen atom to the central zinc than the conventional systems, where the electron‐withdrawing cyano group(s) increased the coordinative ability of the central zinc through the chlorin π‐system. 相似文献
9.
10.
The mass spectral fragmentation of dimethyl glutamate ( 1 ) and its deuterated derivatives 1a , 1b and 1c has been investigated. By loss of a methoxycarbonyl group from the molecular ion an ion of m/e 116 is generated. The latter splits off methanol (m*), the resulting fragment of m/e 84 giving raise to the base peak of the spectrum. Only part of the hydrogen transferred to the leaving group originates from thc amino group, as was suggested earlier [2] [3]. Basing on experiments with deuterated compounds we propose an additional mechanism for the reaction, i.e. hydrogen transfer from C(3) to methoxyl. The fragment generated by both processes is most likely to be a pyrrolinonium ion. Thermal side reactions in the mass spectrometer (formation of pyroglutamic acid ester) followed by fragmentation may lead to the same ion. – The mechanisms discussed are supported by the mass spectral fragmentation of N-acetyl-glutamic acid diesters 3 , 3a , 3b and 3d and of the N, N-dimethyl derivatives 4 and 4a . – The fragmentation reactions investigated are similar to some of 1,3-trimethylenediamine derivatives [7]. This means that there are parallels in the mass spectral fragmentation of difunctional compounds irrespective of the nature of the functional groups. 相似文献
11.
《Journal of polymer science. Part A, Polymer chemistry》2018,56(1):116-124
Perylene diimides (PDIs) and their derivatives are excellent semiconductors, while conjugated polymers based on PDIs have limited applications because of their low electron mobility (μe) derived from low molecular weight. The reported maximum number‐average molecular weight (Mn) of related polymers is only 21 kDa because PDIs have very poor solubility due to strong π–π stacking of their big planar conjugated cores. Herein, it is found that suitable semi‐perfluoroalkyl groups could enhance the solubility of PDIs significantly, and a series of semi‐perfluoroalkyl modified conjugated polymers with high molecular weight and electron mobility were synthesized. The maximum Mn reaches 94.8 kDa [P(4CF8CH‐PDI‐T2)HW]. In their space‐charge‐limited current (SCLC) devices, all polymers exhibit typical characters of electron transporting semiconductors, and the highest μe is up to 8.40 × 10−3 cm2 V−1 s−1 [P(4CF8CH‐PDI‐T2)HW], which is similar as that of widely used electron transporting semiconductor PC61BM (6.41 × 10−3 cm2 V−1 s−1). © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 116–124 相似文献
12.
Four alternatives are compared for estimating vibrational anharmonicity constants without explicitly calculating the expensive fourth derivatives of the potential curves. In the first, semiempirical approach, fourth derivatives for 53 diatomic molecules are estimated from ab initio second and third derivatives by using the Morse model potential. Vibrational anharmonicities ωexe are then computed from the third and fourth derivatives. The second approach invokes a purely empirical linear correlation between ωexe and the harmonic frequencies ωe. The third and fourth empirical approaches suppose that the effective harmonic and anharmonic force constants are proportional (with an additive constant in the fourth approach). Experimental values for ωexe are compared with empirical predictions and with semiempirical estimates based upon Hartree–Fock (HF), Møller–Plesset (MP2), and local, nonlocal, and hybrid density-functional theories (DFT), using the small 6-31G* basis set. Ab initio values of ωe and bond lengths re are also compared against experiment. The (U)MP2 results are the worst and include several anomalies. The other semiempirical methods yield results of comparable accuracy for ωexe of hydrides, although the DFT methods are markedly better for ωe and re and for ωexe of nonhydrides. The empirical estimates are nearly as good as the semiempirical ones. We conclude that: (1) both empirical and semiempirical approximations are useful for predicting stretching anharmonicity constants ωexe to precisions of σ≈5 cm−1 for hydrides and σ≈1.5 cm−1 for nonhydrides; and (2) MP2 theory is relatively unreliable for such calculations. In addition, we find the following tests to be useful when evaluating the reliability of vibrational constants calculated at the UMP2 level: (a) the calculated values of ωe and ωexe should not deviate substantially from the empirical relations; (b) harmonic frequencies and intensities calculated at the MP2 level should be smaller than those calculated at the corresponding HF level; (c) a large distance-dependence of the spin contamination, d〈S2〉/dR≳0.05 Å−1, suggests that calculated constants are too large. © 1998 John Wiley & Sons, Inc. J Comput Chem 19: 1315–1324, 1998 相似文献
13.
John L. Graves 《International journal of quantum chemistry》1997,65(1):1-8
Two variants of the double exponential potential function and their virial modifications are proposed and tested. The first in reduced variables is F(t)=e−mt{[m(m2−1)−1/2−1]exp[−(m2−1)1/2t]−[m(m2−1)−1/2+1]exp[(m2−1)1/2t]} where t=κs=κ(R−Re))/Re, κ is a scaling constant, and m is a parameter. The second is G(t)=e−mt{e−mt−exp[(m2−1)1/2t]+exp[−(m2−1)1/2t]}. For m<1, F(t) and G(t) are expressible in terms of trigonometric functions. A new procedure [multiplication by es/(1+s)] is illustrated that modifies potential functions so that they necessarily satisfy the molecular virial theorem. The generalized double exponential functions generate scaled first and second Dunham coefficients that well describe the experimental results for both ground and excited states. © 1997 John Wiley & Sons, Inc. Int J Quant Chem 65 : 1–8, 1997 相似文献
14.
Calix[4]arene derivatives containing ferrocene units at the upper rim have been synthesized and their anion‐binding and sensing investigated towards anions such as chloride, bromide and hydrogen sulfate by cyclic voltammetry. Electrochemical studies show that these redox‐active ligands electrochemically recognize chloride and bromide anions. These compounds have excellent selectivity for chloride and bromide ions, in the comparison with hydrogen sulfate anion. With ferrocenyl Schiff base calix[4]arene 1 an anodic shift as large as 302 mV is observed on addition of four equivalents of Cl− anion. Also electrochemical and UV–vis spectroscopic titrations ferrocenyl calix[4]arene derivatives 1 with chloride and bromide ions and 2 (only with Cl−) indicate a 1:1 binding‐stiochiometry. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
15.
Jakkarin Limwongyut Dr. Alex S. Moreland Dr. Chenyao Nie Prof. Javier Read de Alaniz Prof. Guillermo C. Bazan 《ChemistryOpen》2022,11(2):e202100260
Cationic conjugated oligoelectrolytes (COEs) are a class of compounds that can be tailored to achieve relevant in vitro antimicrobial properties with relatively low cytotoxicity against mammalian cells. Three distyrylbenzene-based COEs were designed containing amide functional groups on the side chains. Their properties were compared to two representative COEs with only quaternary ammonium groups. The optimal compound, COE2−3C−C3-Apropyl , has an antimicrobial efficacy against Escherichia coli with an MIC=2 μg mL−1, even in the presence of human serum albumin low cytotoxicity (IC50=740 μg mL−1) and minimal hemolytic activity. Moreover, we find that amide groups increase interactions between COEs and a bacterial lipid mimic based on calcein leakage assay and allow COEs to readily permeabilize the cytoplasmic membrane of E. coli. These findings suggest that hydrogen bond forming moieties can be further applied in the molecular design of antimicrobial COEs to further improve their selectivity towards bacteria. 相似文献
16.
为了寻找高效低毒的农药, 从3-甲基-1-取代苯基-5-吡唑酮出发, 经过几步反应得到5-氯-3-甲基-1-取代苯基-4-吡唑羰基异硫氰酸酯. 5-氯-3-甲基-1-取代苯基-4-吡唑羰基异硫氰酸酯分别与对三氟甲基苯胺和2,6-二氯-4-三氟甲基苯胺反应得到10个未见文献报道的N-(取代对三氟甲基苯基)-N'-(1,3,5-三取代)吡唑-4-羰基硫脲类化合物, 其结构经元素分析, IR, 1H NMR确证. 初步生物活性测试结果表明部分化合物有一定的杀菌活性. 相似文献
17.
Dr. Christoph Sonnenschein Christopher P. Ender Faxing Wang Dr. Dieter Schollmeyer Prof. Dr. Xinliang Feng Dr. Akimitsu Narita Prof. Dr. Klaus Müllen 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(36):8007-8011
Higher homologues of dibenzo[c,e][1,2]dithiin were synthesized from oligophenyls bearing multiple methylthio groups. Single-crystal X-ray analyses revealed their nonplanar structures and helical enantiomers of higher meta-congener 6 . Such dibenzo[1,2]dithiin homologues are demonstrated to be applicable to lithium-ion batteries as cathode, displaying a high capacity of 118 mAh g−1 at a current density of 50 mA g−1. 相似文献
18.
Zhixin Song Dr. Xiao Chi Shu Dong Biao Meng Dr. Xiaojiang Yu Dr. Xiaoling Liu Prof. Dr. Yu Zhou Prof. Dr. Jun Wang 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2024,136(7):e202317267
The electrosynthesis of hydrogen peroxide (H2O2) via two-electron (2e−) oxygen (O2) reduction reaction (ORR) has great potential to replace the traditional energy-intensive anthraquinone process, but the design of low-cost and highly active and selective catalysts is greatly challenging for the long-term H2O2 production under industrial relevant current density, especially under neutral electrolytes. To address this issue, this work constructed a carboxylated hexagonal boron nitride/graphene (h-BN/G) heterojunction on the commercial activated carbon through the coupling of B, N co-doping with surface oxygen groups functionalization. The champion catalyst exhibited a high 2e− ORR selectivity (>95 %), production rate (up to 13.4 mol g−1 h−1), and Faradaic efficiency (FE, >95 %). The long-term H2O2 production under the high current density of 100 mA cm−2 caused the cumulative concentration as high as 2.1 wt %. The combination of in situ Raman spectra and theoretical calculation indicated that the carboxylated h-BN/G configuration promotes the adsorption of O2 and the stabilization of the key intermediates, allowing a low energy barrier for the rate-determining step of HOOH* release from the active site and thus improving the 2e− ORR performance. The fast dye degradation by using this electrochemical synthesized H2O2 further illustrated the promising practical application. 相似文献
19.
Angla Schwartz Zoltn Pl Lszl Szab Istvn Hermecz Zoltn Mszros 《Journal of heterocyclic chemistry》1987,24(3):651-654
Infrared and 1H nmr spectra of 4-oxo, 1 , and 4-imino, 2 , quinolizine derivatives or their monocyclic tautomers 3, 4 have been comparatively studied. The number of ethoxycarbonyl groups, the signals of the hetero proton, the C(9)-H, and the C(6)-CH3 group in the 1H nmr spectrum, moreover the N-H stretching vibration bands proved to be diagnostically important for monocyclic or bicyclic as well as for 4-oxo or 4-imino structures. A weak intramolecular hydrogen bridge in compounds 2b and 2f , a strong chelate type hydrogen bridge in 4E and 4F=G could have been demonstrated as well. 相似文献