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Kourkoumelis N Demertzis MA Kovala-Demertzi D Koutsodimou A Moukarika A 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2004,60(10):2253-2259
The reactions of the potent and widely used anti-inflammatory drug diclofenac, HL, with diorganotin(IV) oxides were studied. The dimeric tetraorganodistannoxane complexes [Me(2)LSnOSnLMe(2)](2), [Bu(2)LSnOSnLBu(2)](2), [Ph(2)LSnOSnLPh(2)](2) and the dibutyltin complex [Bu(2)SnL(2)], have been prepared and structurally characterized in the solid state by means of vibrational and 119Sn M?ssbauer spectroscopy. Determination of lattice dynamics by temperature-dependent 119Sn M?ssbauer spectroscopy. From the variable-temperature M?ssbauer effect, the Debye temperature was determined. The complexes have been characterized in solution by NMR (1H and 13C) spectroscopy. Vibrational, M?ssbauer, and NMR data are discussed in terms of the proposed structures. 相似文献
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We discuss the well-known three-centre cation–anion–cation model for superexchange in insulating transition-metal compounds using limiting expansions for the Anderson–Hubbard model. We find that due to the interfering energy scales in the model, a limiting expression for the superexchange J for the idealized Mott–Hubbard (M–H) case t?U?Δ cannot be formally defined. We further show that the decomposition of the superexchange into range-dependent components is formally invalid. The well-known t4 superexchange expression, obtained from path-dependent series expansions, is not unique to these systems as it can also be obtained with many other different expansions, in which either the d–p energy difference Δ or the d-electron correlation U can actually be small. Particularly for milder relationships between the parameters, i.e. t?U?Δ, the reverse from the usual form of the series expansions can yield better agreement with the exact results. This implies that the fitting of experimental data to the simple expressions derived from path-dependent series expansions can lead to qualitatively incorrect relationships between the parameters, fictitiously within the M–H regime. 相似文献
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P. Tavridou U. RussoG. ValleD. Kovala-Demertzi 《Journal of organometallic chemistry》1993,460(2):C16-C18
The results of a single-crystal X-ray diffraction study of the 1:2 adduct between dichlorodimethyltin(IV) and 2-imidazolidone are reported, together with some preliminary IR data. The complex is hexacoordinate and with a distorted cis-octahedral geometry. 相似文献
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Kovala-Demertzi Dimitra Demertzis Mavroudis Yadav Paras Nath Castiñeiras Alfonso West 《Transition Metal Chemistry》1999,24(6):642-647
The synthesis, as well as spectral and structural characterization, of (2-benzoylpyridine-N(4)-methyl-N(4)-phenylthiosemicarbazonato)chloropalladium(II), [Pd(Bz4MePh)Cl], is described. The unit cell contains two crystallographically independent molecules [Pd(1)(Bz4MePh)Cl], (1), and [Pd(2)(Bz4MePh)Cl], (2), stabilized by intra- and intermolecular hydrogen bonding. The distance between the Pd(1) and Pd(2) centres is 3.5038(11) Å. The spectroscopic techniques used in this study are the following: u.v.-visible, i.r. and 1H n.m.r. The protonation constants, determined spectrophotometrically, of the uncoordinated HBz4MePh are pKa1 = 10.82 ± 0.03 and pKa2 = 4.09 ± 0.02. 相似文献
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An J Shade CM Chengelis-Czegan DA Petoud S Rosi NL 《Journal of the American Chemical Society》2011,133(5):1220-1223
Luminescent metal-organic frameworks (MOFs), Ln(3+)@bio-MOF-1, were synthesized via postsynthetic cation exchange of bio-MOF-1 with Tb(3+), Sm(3+), Eu(3+), or Yb(3+), and their photophysical properties were studied. We demonstrate that bio-MOF-1 encapsulates and sensitizes visible and near-infrared emitting lanthanide cations in aqueous solution. 相似文献
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Marios Pittalis Demetra Pitta-Pantazi Constantinos Christou 《Mathematical Thinking and Learning》2018,20(3):222-247
The aim of this study was to propose a new conceptualization of early number sense. Six-year-old students’ (n = 204) number sense was tracked from the beginning of Grade 1 through the beginning of Grade 2. Data analysis suggested that elementary arithmetic, conventional arithmetic, and algebraic arithmetic contributed to the latent construct early number sense, and the invariance of the model over time was validated empirically. Algebraic arithmetic represents the dimension of early number sense that moves beyond conventional arithmetic and encompasses an abstract understanding of the relations between numbers. A parallel process growth model showed that the three components of number sense adopt a linear growth rate. A structural model showed that the growth rate of the algebraic arithmetic component has a direct effect on the growth rate of conventional arithmetic, and subsequently the growth rate of conventional arithmetic predicts the growth rate of elementary arithmetic. 相似文献
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A stability indicating, reversed-phase ion-pair high-performance liquid chromatographic method was developed and validated for the determination of risedronate in pharmaceutical dosage forms. The determination was performed on a BDS C18 analytical column (250 mm × 4.6 mm i.d., 5 μm particle size); the mobile phase consisted of 0.005 M tetrabutylammonium hydroxide and 0.005 M pyrophosphate sodium (pH 7.0) mixed with acetonitrile in a ratio (78:22, v/v) and pumped at a flow rate 1.00 mL min−1. The ultraviolet (UV) detector was operated at 262 nm. The retention times of magnesium ascorbyl phosphate, which was used as internal standard and risedronate were 4.94 and 5.95 min, respectively. The calibration graph was ranged from 2.50 to 20.00 μg mL−1, while detection and quantitation limits were found to be 0.48 and 1.61 μg mL−1, respectively. The intra- and inter-day percentage relative standard deviations, %R.S.D., were less than 5.9%, while the relative percentage error, %Er, was less than 0.4%. The method was applied to the quality control of commercial tablets and content uniformity test and proved to be suitable for rapid and reliable quality control. 相似文献
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This paper investigates the relationship between the creative process in mathematical tasks and spatial, object and verbal cognitive styles. A group of 96 prospective primary school teachers completed the Object-Spatial Imagery and Verbal Questionnaire and took a mathematical creativity test. The results of a multiple regression analysis demonstrated that whereas visual cognitive styles (spatial and object imagery) were statistically significant predictors of participants’ creative abilities in mathematics, verbal cognitive style did not predict these abilities. Further analysis of the data indicated that spatial imagery cognitive style was related to mathematical fluency, flexibility and originality. On the other hand, object imagery cognitive style was negatively related to mathematical originality and verbal cognitive style was negatively related to mathematical flexibility. The study also revealed that individuals with a tendency towards different cognitive styles employed different strategies in the creative mathematical tasks. 相似文献