Mononuclear Cu(II) complexes of novel salicylidene Schiff bases: synthesis and mesogenic properties

Two new Schiff base ligands 1 and 2 (where 1 = 4-(2-hydroxybenzilidenamino)-phenyl-4-(decyloxy)-2-(pent-4-enyloxy)benzoate, 2 = 4-(4-(decyloxy)-2-hydroxybenziliden amino)-phenyl-4-(decyloxy)-2-(pent-4-enyloxy)benzoate) and their copper (Cu)(II) complexes have been synthesised and characterised. The derivatives were fully characterised structurally, and their mesomorphic behaviour was investigated by polarised optical microscopyand differential scanning calorimetry. The structure of Cu(II) complex having 1 as ligand (3) was determined by X-ray diffraction. The Schiff base ligands exhibit enantiotropic nematic phases, the Cu(II) complex 4 shows monotropic nematic phase behaviour, while compound 3 does not show mesomorphism

Chemistry and photochemistry of novel aromatic spiroketals derived from 2,6-bis(5-bromo-2-hydroxybenzylidene) cyclohexanone

Natural colorants such as flavylium and xanthylium derivatives have attracted considerable interest in the last decades due to their potential health effects and replacement of synthetic pigments. In addition, these type of compounds exhibit versatile photochromic properties by switching from a variety of colourswhen submitted to different external stimuli[1-3]. The aim of the present work was to design novel photochromic systems based on xanthylium derivatives. Therefore, we have synthesized and characterized 2,6-bis(5-bromo-2- hydroxybenzylidene)cyclohexanone. The network of chemical reactions when submitted to light and different pH values has been investigated. A new colorless compound 3,11-dibromo7,8-dihydro-6H-chromeno[3,2-d]xanthenes(Scheme 1) isolated from the equilibrated solution of trans-chalcone specie in methanolhave been isolated and fully characterized by NMR and X-ray diffraction. The rate of the reaction increased when the solution of trans-chalcone was exposed to sunlight. The spiroketal form was stable at in neutral and basic conditions, while at low pH values it converts into xantylium cationic form

Behavior of bipyridine derivative Cu(I) complexes in donor solvents

Cu(I) complexes are known as highly emissive compounds having interesting fluorescence applications[1].Theluminescence is generated by more intense metal to ligand charge transfer (MLCT) electronic transitions for Cu(I), affording longer excited-statelifetimes compared to transient d-d excited state of Cu(II)[2].Herein we report the behavior of two bipyridine derivative Cu(I) complexes containing phenanthroline and biquinoline ligands, respectively, in donor solvents as dimethylsulfoxide and acetonitrile.The Cu(I) phenanthroline complex (1) is unstable in solution,due to oxidation of Cu(I) to Cu(II) in time, accompanied by change in coordination geometry from tetrahedral to trigonal bipyramidal. The Cu(I) biquinoline complex (2) is more stable in donor solvents,the stability increasing at low temperatures with the stabilization of tetragonal geometry of Cu(I).In case of biquinoline ligand, this kind of geometry is stabilized by the bulky aryl substituentsatαposition with respect to the pyridine nitrogen

Supramolecular "soft" assemblies based on copper (I) coordination complexes

Copper(I) coordination complexes with N^N chelating oligopyridines are valuable candidates for applications in solar energy conversion1 or lightning technologies2 because of their excellent photophysical and photochemical properties and for the low cost and ready availability of the metal. The most attractive systems are based on ligands able to stabilise their tetrahedral geometry (D2d symmetry) and to hinder the flattening distortions which facilitates oxidation to Cu(II) species.3 Herein we present the synthesis and characterisation of new stable Cu(I) complexes based on functionalised 2,2’-biquinoline ligands (Figure 1) that self-assemble into “soft” supramolecular architectures. The stoichiometry and purity of all compounds were determined using elemental analyses, Atomic Absorption, IR and 1H NMR spectroscopies. The functionalisation of the biquinoline ligand with long alkyl chains yielded thermotropic liquid crystalline systems (CuL1_X and CuL2_X), whereas insertion of hydrophilic groups promoted the assembly in water into supramolecular aggregates (CuL3_X). The thermal behaviour of complexes CuLn_X with n = 1 and 2 was investigated by polarized optical microscopy (POM) and differential scanning calorimetry (DSC). UV-Vis studies on CuL3_X evidenced the presence of supramolecular aggregates in water. Stabilization of Cu(I) systems can be also achieved by building supramolecular assemblies and thus blocking the fluxional process towards a distorted “Cu(II)-like” geometry in concentrated solution of complexes

Детальные геофизические работы с целью поисков меди и железа в провинции Юньнань (Китайская народная республика)

Реферат Выпускная квалификационная работа 106 с., 31 рис., 17 табл., 41 источников, прил. нет Ключевые слова: Китай, провинция Юньнань, железные руды, медные руды, электроразведка, магниторазведка, методика работ, интерпретация результатов. Объектом исследования является: перспективный участок «Е», расположенный в пределах провинции Юньнань в Китайской народной республике. Цель работы – поиски железных и медных руд и оценка перспектив участка Пипин на железные и медные руды. В процессе исследования проводились: выбор участка обоснования, анализ геолого-геофизической изученности района, изучение его геологического строения, анализ результатов ранее проведённых геофизических исследований на участке обоснования Маньхамбо и проектном участке Пипин . В результате исследования: выполнен проеAbstract Final qualifying work: 106 c, 31 rice, 17 Table, 41 sources, no adj. Keywords : China, Yunnan Province, iron ore, copper ore, electromagnetics, magnetic, methods of work, the interpretation of results. The object of the research is: promising area "E", located within the Yunnan Province in the People's Republic of China. The purpose of the work - the search for iron and copper ores and evaluation Pepin area prospects for iron and copper ores. The study was conducted with the choice of study area, analysis of geological and geophysical knowledge of the area, the study of its geological structure, the analysis of the results of previously conducted geophysical research in the area Manhambo study and project site Pepin. As a result of the study: the project is executed to carr

Novel asymmetric benzylidenecyclohexanone photochromic compound as food dye with antioxidant properties

Nature has always been the provider of compounds with unique properties and amazing application within or outside the living organisms [1]. Color is certainly one of the natural features that have always fascinated researchers from almost all fields of knowledge and compounds with such properties have been isolated from raw materials or have been designed and synthesized based thereon [2]. Flavylium derivatives are natural or synthetic compounds responsible for certain color of fruits and flowers and are able to turn from yellow to red and blue depending on the pH of the media [3]. They are also studied for their photochromic behavior when excited with different wavelengths and their network of chemical transformation has been the subject of many research papers [4,5]. We have focused lately on the synthesis of xanthylium derivatives [6], compounds similar in behavior with flavylium ones with symmetrical and asymmetrical substituents on the aromatic rings. The photochromic behavior of the new asymmetric benzylidene cyclohexanone derivative 4-(p-hydroxybenzylidene)-6-hydroxy-1,2,3,4-tetrahydroxanthylium chloride (HTX)in aqueous solution at different pH values was studied using UV-Vis, NMR and fluorescence spectroscopy. In strong acid environment HTX exhibits purple color and a broad absorption band at about 516 nm, corresponding to the presence of the xanthylium cation, while in basic conditions the solutions are red, with an absorption band at about 596 nm. At pH ranging from 9 to 12 HTX is bluish and suffers spontaneous transformations between species involved in the network of chemical reactions. HTX shows good fluorescence behavior at all pH values. HTX has a good antioxidant character of 55.15% determined by DPPH method. The features described above and its curcumin origin would highly recommend it for application in the field of food colorants

Antioxidant activity and photochromic properties of 2,6-bis (2,4- dihydroxybenzylidene) cyclohexanone

Xanthylium derivatives have attracted considerable interest due to their potential health effects and replacement of synthetic pigments. Moreover, these type of compounds exhibit versatile photochromic properties by switching from a variety of colors when submitted to external stimuli (light, temperature, pH). Generally, all these compounds hold the same xanthylium core and follow the same pH-dependent network of reversible chemical reactions as structurally related families such as flavylium [1-4]. In the present study we focused the attention on the isolation and characterisation of of the species involved in the network of chemical reactions of 2,6-bis(2,4- dihydroxybenzylidene)cyclohexanone. The pH-dependent photochromic behavior of the xanthylium derivative has been investigated. In order to identify the species, the NMR spectra were recorded in acidic and basic media. The antioxidant activity was also determined using DPPH assay [5]. The IC50 values of radical scavenging activity for DPPH were found to be 133.68 μg/mL