A series of 2‐(hydroxyphenyl)‐1H‐benzodimidazols bearing readily oxidizable 2,6‐di‐tert‐butyl‐phenol substituents and bis‐chelate Cu(II) complexes based on these ligands were synthesized. The ...structure of the compounds was characterized by NMR, IR, mass spectroscopy and X‐ray crystallographic analysis and redox behavior explored using ESR spectra and cyclic voltammetry. Under oxidation with PbO2 in toluene solution both the ligands and Cu(II) complexes form stable phenoxyl‐type radicals. As shown by ESR measurements and DFT calculations, no exchange interaction exists between unpaired electrons located on metal and oxygen centers in the biradical Cu (II) complexes. The ligands and complexes reveal antioxidant radical scavenging activity measured spectrophotometrically and using ESR and DPPH‐tests.
A series of 2‐hydroxyphenyl‐1H‐benzodimidazols bearing readily oxidizable 2,6‐di‐tert‐butyl‐phenol substituents and bis‐chelate Cu(II) complexes based on these ligands were synthesized. Under oxidation both the ligands and Cu(II) complexes form stable phenoxyl‐type radicals. As shown, no exchange interaction exists between unpaired electrons located on metal and oxygen centers in the Cu(II) complexes.
In 2001-2002 and 2006-2007, the author conducted two comparative surveys among the students of a number of higher educational institutions in Moscow. The main purpose of the surveys was to study ...processes of the modernization of higher education and also to determine what attitudes students hold toward these processes. Of the many aspects of modernization the author focused on the following: (1) college and university education on a tuition basis and nontuition basis; (2) stipends and benefits for students; (3) students' attitudes toward the unified state examination; and (4) how well informed college students are about the Bologna Convention on Higher Education. This article presents the analysis of the author on the findings of her surveys. (Contains 1 note.)
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
This article develops an expert-analytical model for assessing the quality of process-oriented management of construction companies. The model differs in a two-tier approach to object evaluation by ...pre-evaluating the characteristics of objects and their parameters. Assessments were made in connection with the time and financial costs of resources that allow to forming an expert group, conduct a survey and analyzing its results. These results were conducted by the method of written questionnaires, which are divided into three groups: general information about the expert (age, experience, specialty, etc.), the main questions related to the problems being analyzed or evaluated, additional questions to determine the rationale for answers , competence of experts, etc. The list of possible linguistic estimations of characteristics and parameters and their numerical equivalents is formed that will give the chance to provide quality of process-oriented management on the basis of the analyzed integrated indicators of quality of management of the building enterprise. A generalized assessment of the characteristics of each of the experts of the formed group in the expert-analytical model is also formed. The list of objects, parameters and their components which are intended for an estimation of quality of management at the building enterprise is generalized. The dynamic analysis of the integrated indicator of management quality allows the institutional level of contractors to rationally plan the activities of the construction company and adjust the work in sectors (financial, production, resource, etc.) for which negative evaluations were obtained.
A series of 2‐(hydroxyphenyl)‐1H‐benzodimidazols bearing readily oxidizable 2,6‐di‐tert‐butyl‐phenol substituents and bis‐chelate Cu(II) complexes based on these ligands were synthesized. The ...structure of the compounds was characterized by NMR, IR, mass spectroscopy and X‐ray crystallographic analysis and redox behavior explored using ESR spectra and cyclic voltammetry. Under oxidation with PbO2 in toluene solution both the ligands and Cu(II) complexes form stable phenoxyl‐type radicals. As shown by ESR measurements and DFT calculations, no exchange interaction exists between unpaired electrons located on metal and oxygen centers in the biradical Cu (II) complexes. The ligands and complexes reveal antioxidant radical scavenging activity measured spectrophotometrically and using ESR and DPPH‐tests.
Reducing the water content of crude oil is a necessary step in preparing oil for transportation and processing. This task is complicated by the presence of stable water-in-oil emulsions. The most ...widely used approach to oil demulsification is exploring chemical demulsifiers. However, the high cost and impossibility of regenerating the latter require the search for new ways to destroy water-oil emulsions. One of the promising areas is the use of ultrasound. This paper presents the results of studies on the ultrasonic treatment of four samples of emulsions with different water content (8.74; 15; 25 and 30 vol.%) based on oil from the Kumkol oilfield (Kazakhstan). Samples of emulsions were subjected to ultrasonic action at a frequency of 40 kHz for 5-60 min at a temperature of 70±1°C, followed by settling for 40 min at the indicated temperature. The influence of the initial water content in the emulsion, the acoustic intensity, as well as the duration of ultrasonic treatment on the dewatering ratio was investigated. It was found that the residual water content in the oil was 5.04- 7.82 vol.%. Ultrasonic treatment of crude oil from the Kumkol oilfield can be used for preliminary dewatering, to subsequently reduce the consumption of chemical demulsifiers.
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•New method for preparation of derivatives of 3H-phenoxazin-3-one was studied.•The condensation reaction of 3H-phenoxazin-3-one with arylamines was studied.•Redox activity of ...3H-phenoxazin-3-one studied by cyclic voltammetry.•Reduction of 3H-phenoxazin-3-one affords its stable radical anion and dianion.•Very rare for radical anions intense fluorescence was detected.
A sterically crowded 6,8-di-(tert-butyl)-3H-phenoxazin-3-one 3 was prepared by coupling 3,5-di-(tert-butyl)-o-benzoquinone with p-aminophenol. The molecular structure of 3 was established with the aid of X-ray crystallography and the redox activity studied using cyclic voltammetry and ESR spectroscopy. The reduction of 3 with a potassium mirror led to the formation of persistent radical anion 3a and dianion 3b which were characterized by their absorption and luminescence spectra.
A series of pseudo-octahedral metal (M = Mn, Fe, Co, Ni, Cu, Zn) complexes 4 of a new redox-active ligand, 2,4,6,8-tetra(tert-butyl)-9-hydroxyphenoxazin-1-one 3, have been synthesized, and their ...molecular structures determined with help of X-ray crystallography. The effective magnetic moments of complexes 4 (M = Mn, Fe, Co, and Ni) measured in the solid state and toluene solution point to the stabilization of their high-spin electronic ground states. Detailed information on the electronic structure of the complexes and their redox-isomeric forms has been obtained using density functional theory (DFT) B3LYP*/6-311++G(d,p) calculations. The energy disfavored low-spin structures of manganese, iron, and cobalt complexes have been located, and based on the computed geometries and distribution of spin densities identified as MnIV(Cat-N-SQ)2, FeIICat-N-BQ)2, and CoIICat-N-BQ)2 compounds, respectively. It has been shown that stabilization of the high-spin structures of complexes 4 (M = Mn, Fe, Co) is caused by the rigidity of the molecular framework of ligands 3 that sterically inhibits interconversions between the redox-isomeric forms of the complexes. The calculations performed on complex 4 (M = Co) predict that a suitable structural modification that might provide for stabilization of the low-spin electromeric forms and create conditions for the valence tautomeric rearrangement via stabilization of the low-spin electromer and narrowing energy gap between the low-spin ground state tautomer and the minimal energy crossing point on the intersection of the potential energy surfaces of the interconverting structures consists in the replacement of an oxygen in the oxazine ring by a bulkier sulfur atom.
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