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101.
Mihaela Badea Rodica Olar Valentina Uivarosi Dana Marinescu Victoria Aldea Stefania Felicia Barbuceanu George Mihai Nitulescu 《Journal of Thermal Analysis and Calorimetry》2011,105(2):559-564
Two new complexes having general formula VOL2·nH2O [(1) L: 5-hydroxyflavone, n = 1; (2) L: chrysin, n = 4] were synthesized and characterized. Based on IR and electronic data we concluded that studied flavones act as bidentate
ligands in complexes with metallic ion coordinated in a square-pyramidal stereochemistry. The thermal analysis (TG, DTA) elucidated
the composition and also the number and nature of the water molecules. The thermal behavior also indicated strong interactions
between oxovanadium (IV) and these oxygen donor ligands. 相似文献
102.
103.
Efficient crystallization induced emissive materials based on a simple push-pull molecular structure
Cariati E Lanzeni V Tordin E Ugo R Botta C Schieroni AG Sironi A Pasini D 《Physical chemistry chemical physics : PCCP》2011,13(40):18005-18014
Solid state luminescent materials are the subject of ever growing interest both from a scientific and a technological point of view. Aggregation caused quenching (ACQ) processes however represent an obstacle to the development of most luminogens in the condensed phase. This is why particularly fascinating are those materials showing higher emission intensity in the solid state than in solution. Here we report on three 4-dialkylamino-2-benzylidene malonic acid dialkyl esters, very simple push-pull molecules, which are hardly emissive in solution and in the amorphous phase but become good emitters in the crystalline phase according to what has been indicated as crystallization induced emission (CIE). Thanks to combined emission and NMR spectroscopies at different temperatures on the prototype compound 4-dimethylamino-2-benzylidene malonic acid dimethyl ester in solution, we give full evidence that a restricted intramolecular rotation (RIR) phenomenon, in particular the hindered rotation around the aryl main axis of the compound, is at the origin of this behaviour. In addition, solid state photophysical and X-ray diffraction structural characterization allow us to identify J-dimeric interactions as responsible for the particularly intense emission of two of the three compounds. Moreover, by exploiting the compounds' acidochromic properties, applications in sensors and optoelectronics are envisaged. 相似文献
104.
Valentina Dichiarante Maurizio Fagnoni Angelo Albini 《The Journal of organic chemistry》2008,73(4):1282-1289
N,N-Dimethyl-4-aminophenyl cation is used as an electrophilic probe for determining the relative reactivity of nucleophiles. The singlet state (1 1) of this cation is completely unselective (reaction rates with benzene, MeCN, and trifluoroethanol within a factor of 5). The corresponding triplet (3 1) does not react with alcohols and MeCN. The rates of reaction of the latter intermediate with 23 pi, sigma, and n nucleophiles are measured by competition experiments and found to vary over only 2 orders of magnitude over a range of 22 units of the nucleophilicity parameter N introduced by Mayr. As far as one can judge with the considerable scatter of the data, fitting the data of both amines and pi nucleophiles is possible only by using a modified Mayr's equation: log k = s(E + eN) with e = 0.33. The reduced dependence on N is explained by the fact that in the case of diradicalic triplet 3 1 interaction with the nucleophile involves a half-filled (sigma) orbital, which is empty in singlet 11. It is suggested that Mayr's equation can be extended to quite diverse reactions, but a scaling factor of e < 1 may have to be introduced in some cases, according to the electronic structure of the electrophilic probe used. 相似文献
105.
Maria Teresa Cocco Cenzo Congiu Valentina Onnis 《Journal of heterocyclic chemistry》1995,32(2):463-466
The heterocyclization of 3-aminopropenethioamides 1 and 2 with 2-bromoacetophenone is reported. The p-toluenesulphonic acid catalyzed reaction gives a direct route to 1,4-thiazepines 3 and 5 , while in the presence of triethylamine thiophene 4 and 1,4-thiazepin-5-one 6 are obtained. 相似文献
106.
A new approach to the range conditions for the exponential Radon transform is introduced.
Partially supported by NSF EPSCOR Grant and Wesley Foundation Grant no. 9012019.
Partially supported by NSF Grant 33-1807-231. 相似文献
107.
Garino C Ghiani S Gobetto R Nervi C Salassa L Ancarani V Neyroz P Franklin L Alexander Ross JB Seibert E 《Inorganic chemistry》2005,44(11):3875-3879
The synthesis and physical-chemical characterization of the metal-ligand complex [Os(bpy)2(CO)(enIA)][OTf]2 (where enIA = ethylenediamine iodoacetamide) with a sulfhydryl-specific functional group is described. The UV and visible absorption and luminescence emission, including lifetime and steady-state anisotropy, are reported for the free probe and the probe covalently linked to two test proteins. The spectroscopic properties of the probe are unaffected by chemical modification and subsequent covalent linkage to the proteins. The luminescence lifetime in aqueous buffer is approximately 200 ns and the limiting anisotropy is greater than 0.125, suggesting a potentially useful probe for biophysical investigations. 相似文献
108.
In order to explore the influence of cation substitution on the vibrational dynamics of water molecules in zeolites, the evolution of structural properties of the O-H stretching band of water in fully hydrated Na-A and Mg-exchanged A zeolites has been studied, for different percentages of induced ion exchange, by Fourier transform infrared attenuated total reflection spectroscopy as a function of temperature. The differences revealed in the O-H stretching band shapes have been accounted by fitting the spectra as a sum of four components, corresponding to water molecules exhibiting different types of hydrogen bonding. The dependencies of the relative intensities, peak wave numbers, and bandwidths of the resolved components on temperature and Mg2+ content have been discussed. Evidence of the "structure-maker" role played by a zeolitic surface on physisorbed water, systematically enhanced by increasing the percentage of induced ion exchange, is given in the whole explored temperature range. 相似文献
109.
Isoelectric focusing (IEF) was used to distinguish 4 freshwater fish species that are sold in the European Union under the generic label of "perch": Perca fluviatilis (European perch), Lates niloticus (Nile perch), Stizostedion lucioperca (European pikeperch), and Morone chrysops x saxatilis (Sunshine bass). These species have different commercial values but are easily interchangeable because they are sold already filleted, in view of the numerous bones of the whole fish. IEF of the water-soluble proteins extracted from fish muscle resulted in species-specific patterns. None of the bands was common to all 4 species. Intraspecies polymorphism was low and did not concern the bands identified as characteristic of the species. 相似文献
110.
Rosaria D’Amato Mauro Falconieri Fabio Fabbri Valentina Bello Elisabetta Borsella 《Journal of nanoparticle research》2010,12(5):1845-1858
The preparation of sizeable quantities of luminescent Si nanoparticles (Si-np) with controlled morphology is a challenging
task. Here, we describe two strategies aiming at size reduction of the Si-np produced in a laser-assisted silane pyrolysis
reactor without detrimental effects on the process yield and on the nanoparticle structural and compositional properties.
The first method is based on the addition of a sensitizer gas to dilute silane and consequently reduce the nucleation centres
density without decreasing the reaction temperature. The second consists in the introduction of a collector at a variable
distance from the irradiated region to freeze the particle growth and decrease the inter-particle sintering probability. We
report on the characterization of the produced Si-np, and we show that by combining the two methods, we are able to prepare
4 nm crystalline core size nanoparticles with a productivity of 1 g per hour. We also describe the enhancement effect of the
wet-chemical oxidation processes on the luminescence emission intensity of the Si-np. 相似文献