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71.
Donzello MP De Mori G Viola E Ercolani C Bodo E Mannina L Capitani D Rizzoli C Gontrani L Aquilanti G Kadish KM D'Angelo P 《Inorganic chemistry》2011,50(23):12116-12125
The solid state and solution structure of 2,3-dicyano-5,6-di(2-thienyl)-1,4-pyrazine, [(CN)(2)Th(2)Pyz], and its Pd(II) derivative, [(CN)(2)Th(2)Pyz(PdCl(2))(2)]·H(2)O, formed by reaction of [(CN)(2)Th(2)Pyz] with [(C(6)H(5)CN)(2)PdCl(2)] were characterized by X-ray, UV-visible, (1)H and (13)C NMR, and extended X-ray absorption fine structure (EXAFS) spectral measurements. The X-ray crystal structure of [(CN)(2)Th(2)Pyz] shows the presence of one thienyl ring positioned orthogonal to the rest of the molecule, with the two vicinal thienyl rings lying orthogonal to each other in a rare arrangement. NMR studies of [(CN)(2)Th(2)Pyz] in the solid state and in solutions of dimethylformamide or dimethyl sulfoxide confirm a nonequivalence of the thienyl rings in the solid state and also in solution. EXAFS results indicate that two distinct Pd(II) coordination sites are formed at the di(2-thienyl)pyrazino moiety of [(CN)(2)Th(2)Pyz(PdCl(2))(2)]·H(2)O, with identical Pd-N(pyz) (2.03(3) ?) and Pd-Cl (2.36(3) ?) bond lengths but with different Pd-S1 (2.25(4) ?) and Pd-S2 (3.21(5) ?) bond distances in an overall asymmetric molecular framework. Density functional theory (DFT) and time-dependent DFT (TDDFT) theoretical studies also provide information about the structure and spectral behavior of the precursor and its metalated Pd(II) derivative. (1)H/(13)C NMR and UV-visible spectral measurements were also carried out on two heteropentametallic porphyrazine macrocycles which were prepared by a reaction of PdCl(2) with [Th(8)TPyzPzM] where Th(8)TPyzPz = tetrakis-2,3-[5,6-di-(2-thienyl)-pyrazino]porphyrazinato dianion and M = Mg(II)(H(2)O) or Zn(II). Spectroscopic data on the newly synthesized [(PdCl(2))(4)Th(8)TPyzPzM] compounds suggest that the binding of PdCl(2) involves coordination sites of the type S(2(th))PdCl(2) with the two thienyl rings of each di(2-thienyl)pyrazino fragment bound to Pd(II) in an equivalent manner ("th-th" coordination). This is similar to what was found for the corresponding octapyridinated analogues ("py-py" coordination). 相似文献
72.
73.
Calorimetric measurements were carried out on ester-solvent systems where the esters were H(CH2)xCOO(CH2)yH, with x and y varying from 1 to 5, and the solvents were n-hexane and 1,2-dichloroethane. Calculation of the enthalpies of cavity formation enabled the enthalpies of interaction to be determined. Both enthalpies correlated with number of carbon atoms N, equal to x+y in the esters, giving for 1,2-dichloroethane
相似文献
74.
Volpi G Garino C Breuza E Gobetto R Nervi C 《Dalton transactions (Cambridge, England : 2003)》2012,41(3):1065-1073
Three new bis-cyclometalated iridium(III) complexes, of general formula [Ir(2-phenylpyridine)(2)(L)](+), are reported. The compounds contain a dipyridine-type ligand (L) derived from di-2-pyridylketone (dipyridin-2-ylmethanol, 2,2'-(hydrazonomethylene)dipyridine and 3-hydroxy-3,3-di(pyridine-2-yl)propanenitrile) and were synthesized through two different reaction pathways. The alternative synthetic pathway herein proposed, namely the direct reactions on the complex [Ir(2-phenylpyridine)(2)(2,2'-dipyridylketone)](+), overcame the inconveniences encountered with the standard reaction between the dimeric precursor [Ir(2-phenylpyridine)(2)(μ-Cl)](2) and the ancillary ligands (L). The photophysical characterization of the iridium complexes reveals that modifications on the ancillary ligand introduce large changes in the photophysical behaviour of the complexes. High emission quantum yield is associated with the presence of a saturated carbon between the two pyridyl moieties: [Ir(2-phenylpyridine)(2)(2,2'-dipyridylketone)](+) and [Ir(2-phenylpyridine)(2)(2,2'-(hydrazonomethylene)dipyridine)](+) are extremely low emissive, while [Ir(2-phenylpyridine)(2)(dipyridin-2-ylmethanol)](+) and [Ir(2-phenylpyridine)(2)(3-hydroxy-3,3-di(pyridine-2-yl)propanenitrile)](+) are good photoemitters. DFT and TD-DFT calculations confirmed the mixed LC/MLCT character of the excited states involved in the absorption and emission processes and highlighted the role of the π-conjugation between the two subunits of the ancillary ligand in determining the nature of the LUMO. 相似文献
75.
Marco Vincenti Claudio Minero Stefania Lago Costanza Rovida 《Journal of separation science》1995,18(6):359-362
A rapid and effective procedure, developed for the determination of polar compounds in water, has been applied to hydroxycarbamates. In few minutes, it is possible to perform a catalyzed derivatization of such compounds directly in the aqueous medium, using n-hexyl chloroformate. Extraction with n-hexane and injection into a benchtop GC-MS system are the only two further steps to complete the analysis. Chemical ionization proved to be more effective than electron impact to produce valuable mass spectra in terms of selectivity and sensitivity. Linear quantitative responses were demonstrated over a two-order-of-magnitude range. The minimum detectable concentration was 3 ppb for acetohydroxamic acid and 10 ppb for hydroxyurethane, obtained from Po river water samples spiked with the two hydroxycarbamate standards. 相似文献
76.
Perusal of literature data and some new results concerning syndiotactic-specific polymerization of styrene suggest a reaction mechanism accounting for the steric control. Key features of the proposed mechanism are stereorigid ηn coordination of the growing chain end and diastereoselective coordination of the monomer imposed by direct interactions with the ancillary ligand of the metal complex, a pseudotetrahedral chiral Ti(III) or Zr(III) cation, which inverts its configuration after every syndiospecific insertion step. 相似文献
77.
Kashyap HK Hettige JJ Annapureddy HV Margulis CJ 《Chemical communications (Cambridge, England)》2012,48(42):5103-5105
Structural patterns that have the same spatial periodicity but a phase offset give rise to peaks and anti-peaks (negative-going peaks) at the same q value in the SAXS structure function S(q). As an example, in ionic liquids we often find charge alternation, and at the distance where one finds a density enhancement of charges of the same type one also finds a depletion of charges of opposite sign. Another such situation arises with polar-apolar densities. At distances where there is enhancement of same-type (polar-polar or apolar-apolar) densities there is also a depletion of opposite-type (polar-apolar) density. This gives rise to prepeaks and what we call same spatial periodicity anti-prepeaks. 相似文献
78.
Hélio A. Stefani Claudio M.P. Pereira Roberta B. Almeida Karla P. Guzen 《Tetrahedron letters》2005,46(40):6833-6837
The 4-halo-3,5-dimethyl pyrazoles have been synthetisized in good yields in short reaction times in the absence of a catalyst by reaction of 3,5-dimethyl pyrazoles with N-halosuccinimides (NBS, NCS and NIS) under ultrasound irradiation. Finally, the halogenation of pyrazoles with Br2, ICl and I2 was showed in similar conditions. 相似文献
79.
JPC – Journal of Planar Chromatography – Modern TLC - 相似文献
80.
Combined Experimental and Multivariate Model Approaches for Glycoalkaloid Quantification in Tomatoes
Gabriella Tamasi Alessio Pardini Riccardo Croce Marco Consumi Gemma Leone Claudia Bonechi Claudio Rossi Agnese Magnani 《Molecules (Basel, Switzerland)》2021,26(11)
The intake of tomato glycoalkaloids can exert beneficial effects on human health. For this reason, methods for a rapid quantification of these compounds are required. Most of the methods for α-tomatine and dehydrotomatine quantification are based on chromatographic techniques. However, these techniques require complex and time-consuming sample pre-treatments. In this work, HPLC-ESI-QqQ-MS/MS was used as reference method. Subsequently, multiple linear regression (MLR) and partial least squares regression (PLSR) were employed to create two calibration models for the prediction of the tomatine content from thermogravimetric (TGA) and attenuated total reflectance (ATR) infrared spectroscopy (IR) analyses. These two fast techniques were proven to be suitable and effective in alkaloid quantification (R2 = 0.998 and 0.840, respectively), achieving low errors (0.11 and 0.27%, respectively) with the reference technique. 相似文献
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