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101.
Hulme AT Johnston A Florence AJ Fernandes P Shankland K Bedford CT Welch GW Sadiq G Haynes DA Motherwell WD Tocher DA Price SL 《Journal of the American Chemical Society》2007,129(12):3649-3657
The predictions of the crystal structure of 3-azabicyclo[3.3.1]nonane-2,4-dione submitted in the 2001 international blind test of crystal structure prediction (CSP2001) led to the conclusion that crystal structures containing an alternative hydrogen bonded dimer motif were energetically competitive with the known catemer-based structure. Here we report an extensive search for a dimer-based crystal structure. Using an automated polymorph screen a new catemer-based metastable polymorph (form 2) and two new catemer-based solvates were found, and concurrent thermal studies reproduced form 2 and identified a plastic phase (form 3), whose powder X-ray diffraction pattern was consistent with the cubic space group I23 (a = 7.5856(1) A). Computational studies on the monomer showed that the imide N-H was a weak hydrogen bond donor, rationalizing the occurrence of the plastic phase which involved the breaking of all hydrogen bonds, and modeling of small clusters showed that dimers could easily reorganize to give the catemer. FTIR spectra confirmed the weakness of the hydrogen bond, with the solute showing no self-assembly in solution. It is concluded that the weakness of the N-H donor, coupled with the globular shape of the molecule, allows unusually facile transformation between alternative hydrogen bonding motifs during aggregation and nucleation. 相似文献
102.
Devkota KP Lenta BN Choudhary MI Naz Q Fekam FB Rosenthal PJ Sewald N 《Chemical & pharmaceutical bulletin》2007,55(9):1397-1401
Bioguided phytochemical investigation of Sarcococca hookeriana with respect to the cholinesterase enzyme inhibitory assay yielded two new pregnane-type steriodal alkaloids hookerianamide H (1) and hookerianamide I (2), along with three known alkaloids N(a)-methylepipachysamine D (3), sarcovagine C (4) and dictyophlebine (5). Their structures were determined with the aid of extensive spectroscopic analysis. All compounds showed good inhibitory activities against the enzymes acetylcholinesterase (IC(50) 2.9-34.1 microM) and butyrylcholinesterase (IC(50) 0.3-3.6 microM). These compounds also showed moderate antiplasmodial activity (IC(50) 2.4-10.3 microM) against the Plasmodium falciparum chloroquine resistant W2 strain. 相似文献
103.
104.
Tayyaba Ghani Mohammad Mujahid Mazhar Mehmood Gengmin Zhang Sumaira Naz 《Journal of Saudi Chemical Society》2019,23(8):1231-1240
Combined structure of anodic TiO2 nanotubes and TiO2 nanoparticles (TiNTs-TiNPs) has been synthesized by a facile combination of hydrothermal and chemical vapor deposition methods. Ordered TiO2 nanotubes with smooth walls were fabricated by two step anodization method in ethylene glycol containing NH4F at 50 V. This nanotubular array after annealing at 450 °C was subjected to the hydrothermally produced gaseous environment in an autoclave with diluted TiCl4 solution at its bottom. Vapors of TiCl4 were allowed to react chemically with water vapors for predefined time durations at 180 °C that resulted in the deposition of TiO2 nanoparticles on tubes’ surface and side walls. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) confirmed that for one hour reaction duration, nanoparticles were evenly coated on the walls of nanotubes, whereas, longer durations tend to deteriorate the tubular structure. Consequently, the ordered TiNTs-TiNPs array produced after one hour coating has shown better performance for dye-sensitized solar cell DSSC) in back illumination mode with 130% increase in efficiency as compared to the device based on bare TiO2 nanotubes. The same photoanode has higher reflective properties with higher scattering ability. The solar cell based on this photoanode exhibits higher external quantum efficiency and effective charge transport properties. This study shows that porous ordered 1D structures based on TiO2 are of crucial importance for the high performance of DSSCs. 相似文献
105.
Ravinder Kumar Dr. Shagufi Naz Ansari Rakesh Deka Praveen Kumar Dr. Mohit Saraf Dr. Shaikh M. Mobin 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(55):13669-13698
Covalent-organic frameworks (COFs), being a new member of the crystalline porous materials family, have emerged as important materials for energy storage/conversion/generation devices. They possess high surface areas, ordered micro/mesopores, designable structures and an ability to precisely control electro-active groups in their pores, which broaden their application window. Thanks to their low weight density, long range crystallinity, reticular nature and tunable synthesis approach towards two and three dimensional (2D and 3D) networks, they have been found suitable for a range of challenging electrochemical applications. Our review focuses on the progress made on the design, synthesis and structure of COFs and their composites for various energy applications, such as metal-ion batteries, supercapacitors, water-splitting and solar cells. Additionally, attempts have been made to correlate the structural and mechanistic characteristics of COFs with their applications. 相似文献
106.
Shama Sehar Iffat Naz Abdul Rehman Wuyang Sun Saleh S. Alhewairini Muhammad Nauman Zahid Adnan Younis 《应用有机金属化学》2021,35(1)
Herein, two‐shaped cerium oxide nanoparticles (NPs), that is, spherical and cubical, were synthesized through hydrothermal approach by tuning reaction temperatures. The morphology and structural and chemical composition of both samples were characterized by transmission electron microscopy (TEM), high‐resolution TEM (HRTEM), X‐ray diffraction (XRD), and X‐ray photoelectron spectroscopy (XPS), respectively. Both types of NPs were subjected to photodegradation of industrial dye, methylene blue, under dark, sunlight, and UV irradiation, and their recyclability and reusability were also assessed. Besides, the effect of pH, concentration of NPs, and dye on degradability was also analyzed. The cubical‐shaped NPs demonstrated superior degradation of ~70% under UV irradiation than the spherical ones (<50%). The antibacterial activities of both NPs were also examined, and cubical‐shaped NPs were found to exhibit superior antimicrobial potential (zone of inhibition [ZOI]: 25.75 ± 0.25, 18.83 ± 0.76, 15.75 ± 0.66, and 15.75 ± 0.25 mm) in comparison with the spherical ones (ZOI: 19.41 ± 0.94, 14.25 ± 0.66, 12.58 ± 1.01, and 9.91 ± 1.01 nm) for Escherichia coli, Pseudomonas aeruginosa, Bacillus subtilis, and Staphylococcus aureus respectively with reduced growth and viable count. This difference in performance may be attributed to the higher surface areas of cubical‐shaped NPs and higher content of oxygen vacancies. The results presented in this study suggest that cubical NPs are excellent candidates for treating industrial wastewater with greater reproducibility. Moreover, they can be used as active growth inhibitors against different microorganisms and thus can be extremely useful in developing medical devices and to design various antimicrobial systems. 相似文献
107.
Davey RJ Sadiq G Back K Wilkinson L Seaton CC 《Chemical communications (Cambridge, England)》2012,48(14):1976-1978
While the use of additives to control the crystallization of polymorphs is well known, similar methodology to promote the crystallization of a metastable conglomerate over a stable racemic compound in enantiomeric systems has not been reported. Here we demonstrate this phenomenon in the case of 2-chloromandelic acid. 相似文献
108.
Subuhi Khan Ghazala Yasmin Nader Ali Makboul Hassan 《Applied mathematics and computation》2010,215(11):3769-3776
This paper is an attempt to stress the usefulness of the operational methods in the theory of special functions. Using operational methods, we derive summation formulae and generating relations involving various forms of Hermite-base polynomials and functions. 相似文献
109.
By employing concerted 1 and 2D NMR techniques, exact NMR spectral assignments have been made of the acyl (2-7) and methyl (8 and 9) derivatives of mangiferin (1) isolated from the leaves of Bombax ceiba. Derivatives 2, 8 and 9 have been reported in literature, while 3-7 represent new compounds. The acetates 2 and 3 were found to be unstable and were converted into the same penta-acetate 4 at room temperature. Extensive NMR studies on mangiferin (1) and its derivatives showed that H-4 exchanges with deuterium of the solvent molecule more easily. This exchange under acidic conditions occurred at that position (C-4) where electrophilic substitution reactions can easily take place. This is the first report describing the exchange of C-4 proton of mangiferin (1), or any other xanthone, with deuterium of solvent molecules. 相似文献
110.
The kinetics of photooxidation of pyruvate was investigated in presence of zinc oxide catalyst under illumination of visible light. The influence of different parameters such as concentrations of reactants, amount of catalyst and irradiation time was studied on the redox reaction under pseudo‐first order conditions. The results indicated that amount of catalyst, presence of electron accepter in solution and irradiation time was the key factors influencing the efficiency of photo‐oxidation of pyruvate to acetyl. 相似文献