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81.
Preecha Phuwapraisirisan Serm Surapinit Sitthidesch Sombund Santi Tip-pyang 《Tetrahedron letters》2006,47(22):3685-3688
Three new furanocoumarins, named feroniellins A (1), B (2), and C (3), were isolated from the roots of Feroniella lucida. Compounds 1-3 are novel structures having an oxolane, oxane, and oxepane moiety. Their overall structures and configurations were determined by spectral and chemical methods. The cytotoxicities of 1-3 were evaluated against human KB and HeLa carcinoma cells. 相似文献
82.
Tasinato N Stoppa P Charmet AP Giorgianni S Gambi A 《The journal of physical chemistry. A》2006,110(50):13412-13418
The FTIR spectra of CH2[double bond]CHF have been investigated in the nu(8), nu(10), and nu(11) region between 750 and 1050 cm(-1) at a resolution of about 0.002 cm(-1). The nu(8) vibration of symmetry species A' gives rise to an a/b-type hybrid band, while the nu(10) and nu(11) modes of A' ' symmetry produce c-type absorptions. Due to the proximity of their band origins, the three vibrations perturb each other by Coriolis and high-order anharmonic resonances. In particular, the interactions between the nu(8) and nu(10) modes are very strong and widespread with band origins separated by only 1.37 cm(-1). Besides the expected c-type characteristics, the nu(10) band shows a very intense pseudo a-type component caused by the strong first-order Coriolis resonances with the nu(8) state. Furthermore, the 2nu(9) "dark state" was found to be involved in the interacting band systems. The spectral analysis resulted in the identification of 3144, 3235, and 3577 transitions of the nu(8), nu(10), and nu(11) vibrations, respectively. Almost all the assigned data were simultaneously fitted using the Watson's A-reduction Hamiltonian in the Ir representation and the perturbation operators. The model employed includes nine types of resonances within the tetrad nu(8)/nu(10)/nu(11)/2nu(9) and a set of spectroscopic constants for the nu(8), nu(10), and nu(11) fundamentals as well as parameters for the "dark state" 2nu(9), and fourteen coupling terms have been determined. 相似文献
83.
Flors C Ogilby PR Luis JG Grillo TA Izquierdo LR Gentili PL Bussotti L Nonell S 《Photochemistry and photobiology》2006,82(1):95-103
Experiments were performed to elucidate the excited-state behavior of 9-phenylphenalenones, which are phototoxic plant secondary metabolites involved in mechanisms of light-mediated plant defense. Using a combination of time-resolved and steady-state UV/visible spectroscopies, time-resolved IR absorption spectroscopy, time-resolved singlet oxygen phosphorescence measurements and cyclic voltammetry, we provide evidence of an intramolecular charge-transfer process in the excited singlet and the triplet states of 9-phenylphenalenones that modulates the photosensitized production of singlet oxygen. 相似文献
84.
Maensiri S Nuansing W Klinkaewnarong J Laokul P Khemprasit J 《Journal of colloid and interface science》2006,297(2):578-583
This paper describes the fabrication of barium strontium titanate (Ba0.6Sr0.4TiO3 or BST) nanofibers by electrospinning method using a solution that contained poly(vinylpyrrolidone) and a sol-gel solution of BST. The as-spun and calcined BST/PVP composite nanofibers were characterized by TG-DTA, X-ray diffraction, FT-IR, SEM and TEM, respectively. After calcination of the as-spun BST/PVP composite nanofibers at above 700 degrees C in air for 2 h, BST nanofibers of 188+/-25 nm in diameter having well-developed cubic-perovskite structure were successfully obtained. The crystal structure and morphology of the nanofibers were influenced by the calcination temperature. Calcination at below 700 degrees C resulted in amorphous phase whereas BST with second phase such as barium titanate were formed at above 700 degrees C. Diameters of the nanofibers decreased from 208+/-35 to 161+/-18 nm with increasing calcination temperature between 600 and 800 degrees C. 相似文献
85.
Pietropolli Charmet A Stoppa P Toninello P Baldacci A Giorgianni S 《Physical chemistry chemical physics : PCCP》2006,8(21):2491-2498
Pulsed slit-jet high resolution (up to 0.0009 cm(-1) FWHM) infrared diode laser spectra of CF(3)Br, with natural isotopic abundance, were obtained in the region around 9.2 microm at the rotational temperature of about 50 K. In addition, diode laser spectra at reduced temperature (200 K) were recorded. We present here the rovibrational analysis of the nu(1) fundamental in the range 1075-1090 cm(-1). The fine structure of many P(J) and R(J) clusters has been well resolved for the first time. The assignment of rovibrational transitions has been accomplished up to K = 27, J = 63 for CFBr and K = 33, J = 62 for CFBr. A total of 636 (CFBr) and 880 (CFBr) lines were used in the final fit and a very accurate set of molecular constants, including the quartic centrifugal distortion coefficients for the v(1) = 1 state of both the bromine isotopologues, was obtained. In addition, spectral features belonging to the nu(1) + nu(6)-nu(6) hot band were unambiguously identified and a set of spectroscopic parameters were determined. 相似文献
86.
87.
Marcello Tiecco Silvia Sternativo Francesca Del Verme Claudio Santi Luana Bagnoli Andrea Temperini 《Tetrahedron》2008,64(15):3337-3342
The first example of the enantioselective ring opening of meso-epoxides by (phenylseleno)silanes using salen(Cr)complexes as catalyst is described. This desymmetrization reaction constitutes a simple and convenient approach to synthetically versatile optically active β-hydroxy selenides. 相似文献
88.
Calderazzo F Englert U Pampaloni G Santi R Sommazzi A Zinna M 《Dalton transactions (Cambridge, England : 2003)》2005,(5):914-922
Titanium tetrachloride reacts with 2,6-bis[(1-phenylimino)ethyl]pyridine, 1, and 2,6-bis[1-(2,6-diisopropylphenylimino)ethyl]pyridine, 2, giving the adducts of general formulae [Ti1Cl3]Cl, 3, and [Ti2Cl3]Cl, 6, the latter through the intermediacy of the covalently bonded [Ti2Cl4], 4. Heating 6 leads to reduction to the titanium(III) derivative [Ti2Cl3], 12, the latter characterized by X-ray diffraction methods. The reaction of [Ti1Cl3]Cl with a toluene solution of MAO proceeds with methylation at the ortho-position of the pyridine ring to give the titanium(iv) derivative [Ti(C22H21N3)Cl3], 8. The reaction of [Ti2Cl3]Cl with MAO gives a mixture of products containing [Ti2Cl2(OAlCl3)], 9. Compound 9, which has been prepared independently by reacting 6 with AlOCl, is a rare case of a compound containing the -OAlCl3 moiety, as shown by a single-crystal X-ray diffraction study. From the tetrachlorides of zirconium and hafnium with 1 or 2, the corresponding adducts [M(L)Cl4] have been obtained in high yields. These derivatives of Group 4 metals act as ethylene polymerization catalytic precursors: the substitution of the phenyl ring of the imino fragment strongly influences the catalytic activity which is 5,544 kg(PE) mol(Ti)(-1) h(-1) in the case of 3 and 267 kg(PE) mol(Ti)(-1) h(-1) with 6. Catalytic activity has been observed for zirconium and hafnium too, the activity decreasing from zirconium to hafnium, under comparable conditions. 相似文献
89.
90.
Summary An ion-beam-assisted deposition (IBAD) technique, based on reactive evaporation using hydrogen/ methane gas mixture, has been
used for the preparation ofa-Si1−x
C
x
: H films. Measurements are reported on the composition, optical gap, infra-red vibrational absorption bands and on the electrical
dark-conductivity temperature dependence to verify the reliability of this deposition method. On increasing the compositional
parameterx up to 0.35, the IR results show an increasing hydrogenation and the presence of Si-CH3 units in addition to the ones with the carbon fully coordinated with the silicon, while the optical-gap and the dark-conductivity
activation energies reached the values of 2.44 eV and 0.77 eV, respectively.
The authors of this paper have agreed to not receive the proofs for correction 相似文献