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971.
Danuta Frackowiak Ismail Abdourakhmanov Roman Cegielski Roger M. Leblanc 《Photochemistry and photobiology》1993,57(5):877-884
Abstract— Polarized absorption, fluorescence and photoacoustic spectra of bacteriochlorophyll (BChl)-lipoprotein complexes from the purple bacterium Chromatium minutissimum oriented in stretched polyvinylalcohol films were measured at room temperature and 85 K. The preparations contain large amounts of the B800-820 antenna complexes. From polarized absorption spectra taken under various light beam incidence angles with respect to the film plane, conclusions concerning arrangement of pigment molecules in B800-820 complex are obtained. The transition moments of the BChl Qy band are not exactly parallel to the membrane plane. It seems that there are pools of differently oriented BChl chromophores absorbing in both 800 nm and 820 nm regions. Change in temperature strongly influences linear dichroism of carotenoids and BChl Qy bands. The reversible changes in absorption, linear dichroism and photoacoustic spectra caused by the variation in sample temperature suggest strongly the reversible twisting of carotenoid molecules, related probably to modification of the interactions between carotenoids and proteins. Various carotenoids exhibit different yield of thermal deactivation and this yield is also temperature dependent. 相似文献
972.
A simple, rapid, and reliable method is given for determination of As(III) based on arsenite reduction of alcoholic iodine and titration of the equivalent iodide with Hg(II) using silver amalgam as the indicator electrode. Arsenite reduction is applied to the estimation of lead in minium, manganese in duralumin, chromium in zinc chromate, and vanadium and chromium in ilmenite, the excess of arsenite being determined by the same method used for As(III). The endpoints are accurately determined with very satisfactory potential breaks. 相似文献
973.
Ismail I. Fasfous Mustafa M. El‐Abadelah Salim S. Sabri 《Journal of heterocyclic chemistry》2002,39(1):225-227
The synthesis of new pyrazolo[4,3‐c]β‐carbolines ( 8a,b ) is achieved by condensation of the appropriate aldehyde with 3‐(4‐amino‐1,3‐dimethylpyrazol‐5‐yl)indole ( 4 ) under Pictet‐Spengler reaction conditions. Regioselective cyclization occurred at the usual indole C‐2 position as evidenced from the 1H‐and 13C nmr spectra of 8a,b which lack the pyrrolic H‐2 signal, present in 4 (δ 7.26, 1H, d, Jch‐NH = 2‐5 Hz). 相似文献
974.
Three new vic-dioxime ligands, [N-(ethyl-4-amino-1-piperidine carboxylate)-phenylglyoxime (L1H2), N-(ethyl-4-amino-1-piperidine carboxylate)-glyoxime (L2H2), and N,N′-bis(ethyl-4-amino-1-piperidine carboxylate)-glyoxime (L3H2)], and their Co(II) with Cu(II) metal complexes, were synthesized for the first time. Mononuclear complexes of these ligands
with a 1:2 metal-ligand ratio were prepared with Co(II) and Cu(II) salts. The BF2+-capped Co(II) and mononuclear complexes of the vic-dioxime were prepared for [Co(L1·BF2)2] and [Co(L2·BF2)2]. The ligands act in a polydentate fashion bonding through nitrogen atoms in the presence of a base, as do most vic-dioximes. The cobalt(II) and copper(II) complexes are non-electrolytes as shown by their molar conductivities (ΛM) in DMF. The structures of the ligands and complexes were determined by elemental analyses, FT-i.r., u.v.–vis., 1H- and 13C-n.m.r. spectra, magnetic susceptibility measurements, and molar conductivity. The comparative electrochemical studies show
that the stabilities of the reduced or oxidized species and the electrode potentials of the complexes are affected by the
substituents attached on the oxime moieties of the complexes. 相似文献
975.
Four novel 3-alkyl(aryl)-4-(4-methoxycarbonylbenzylidenamino)-4,5-dihydro-1H-1,2,4-triazol-5-ones (2) were synthesized by the reactions of 3-alkyl(aryl)-4-amino-4,5-dihydro-1H-1,2,4-triazol-5-ones (1) with methyl 4-formylbenzoate and characterized by elemental analyses and IR, 1H NMR, 13C NMR and UV spectral data. In addition, isotropic 1H and 13C nuclear magnetic shielding constants of 2 were obtained by the gauge-including-atomic-orbital (GIAO) method at the B3LYP density functional level. The geometry of each compound was optimized using the 6-311G basis set. 相似文献
976.
Hydrazononitriles as Precursors for 4‐aminotriazoles and 3‐aminoisoxazoles: One Pot Synthesis of triazolo[1,5‐a]quinazoline Derivatives 下载免费PDF全文
Ismail A. Abdelhamid Amr M. Abdelmoniem Said A. S. Ghozlan Holger Butenschön 《Journal of heterocyclic chemistry》2016,53(4):1251-1258
The reaction of various hydrazononitriles with hydroxylamine hydrochloride yielded various products, namely, 3‐aminoisoxazolone, 3‐amino‐1,2,4‐triazole and 4‐amino‐1,2,3‐triazole derivatives depending on the nature of substituents. 相似文献
977.
Regioorientation in the Addition Reaction of α‐Substituted Cinnamonitrile to Enamines Utilizing Chitosan as a Green Catalyst: Unambiguous Structural Characterization Using 2D‐HMBC NMR Spectroscopy 下载免费PDF全文
Said A. S. Ghozlan Ahmed Gamal Ahmed Ismail Abdelshafy Abdelhamid 《Journal of heterocyclic chemistry》2016,53(3):817-823
Hexahydroquinolines and their fused derivatives are obtained in good to excellent yields by proceeding through a simple, mild, and efficient procedure including the reaction of enamines with substituted cinnamonitriles using DABCO, piperidine, or chitosan as catalysts. The regioorientation of Michael addition was established with no doubt using the 2D‐HMBC spectroscopy. 相似文献
978.
A sensitive and selective spectrofluorimetric method has been developed for the rapid determination of europium(III). This method is based on the formation of nonluminous complex between Eu(III) and a Schiff base reagent N, N′-bis (salicylidene)-1,2-phenylenediamine (PABD) and measuring the fluorescence quenching of Eu(III)-PABD complex at λex/em = 390/577 nm. The fluorescence intensity complex decreased linearly by increasing the Eu(III) concentration in the range of 1.0–13.0 μM. The optimum conditions for the complex formation were determined such as a pH .0 of borate buffer. The limits of detection (LOD) and quantification (LOQ) of Eu(III) were determined and found to be 0.217 and 0.653 μM, respectively. The maximum relative standard deviation of the method for an europium(III) standard of 6.0 μM was 2.07 % (n = 6). The proposed procedures could be applied successfully for the determination of the investigated metal ion in some spiked water samples with a good precision and accuracy compared to official and reported methods as revealed by t- and F-tests. 相似文献
979.
Ismail Warad Mohammad Azam Saud I. Al-Resayes Mohammad Shahidul Islam Sarfaraz Ahmed Salim F. Haddad 《Research on Chemical Intermediates》2016,42(2):379-389
Two new palladium complexes derived from the di(2-pyridinyl)methanone N-(2-pyridinyl)hydrazone (DPMNPH) ligand are reported. The compounds were characterized by elemental analysis, spectroscopic studies, and, for the DPMNPH ligand, single-crystal X-ray diffraction analysis. The DPMNPH ligand crystallized as orthorhombic with the space group P212121. The H1 atom is intramolecularly bonded to the pyridinic N4 with N1–H1 = 0.92(3) Å, H1···N4 = 1.87(2) Å, N1···N4 = 2.615(2) Å, and N1–H1···N4 = 137(2)°. Both complexes were excellent catalysts in the Heck reaction in the presence of base. 相似文献
980.
This article deals with a quasilinear elliptic equation with variable exponent under a homogenous Dirichlet boundary-value condition, where nonlinearity also depends on the gradient of the solution. By using an iterative method based on Mountain Pass techniques, the existence of a positive solution is obtained. 相似文献