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41.
Gaballah ST Hussein YH Anderson N Lian TT Netzel TL 《The journal of physical chemistry. A》2005,109(48):10832-10845
Femtosecond, picosecond, and nanosecond transient absorbance (TA) and picosecond emission kinetics results are presented for three 5-(1-pyrenyl)-2'-deoxyuridine nucleosides each with a different two-atom linker joining pyrenyl C-1 to uracil C-5. The linkers are respectively -NHCO-, -(CH(2))(2)-, and -C[triple bond]C- for PAdU, PEdU, and PYdU. For all three nucleoside conjugates, most conformers undergo intramolecular charge transfer (CT) from their pyrenyl (1)(pi,pi) excited states to form Py(*+)/dU(*-) CT products in ultrashort times: 相似文献
42.
We present a study of single color (2 + 1) resonance-enhanced multiphoton ionization (REMPI) of H2O, D2O, and HDO via several Rydberg states lying in the energy range from 80 000 to 86 000 cm−1. Photoelectron spectra (PES) show that the corresponding cations can be vibrationally state-selected for most vibrational states. The exception is the bend of H2O+ and HDO+, where mixing in the REMPI intermediate level results in weak ion intensity and only 50% state purity. 相似文献
43.
The first intermolecular Friedel-Crafts acylation of a variety of aromatic substrates with azetidinones is described. The Friedel-Crafts acylations are performed under very mild conditions, using trifluoromethanesulfonic acid to produce beta-amino aromatic ketones in excellent yields. 相似文献
44.
Ivanova SM Nolan BG Kobayashi Y Miller SM Anderson OP Strauss SH 《Chemistry (Weinheim an der Bergstrasse, Germany)》2001,7(2):503-510
The relative Lewis basicities of six Al(ORF)4- ions, Al[OC(CH3)(CF3)2]4-, Al(OC(CF3)3]4-, Al(OCPh(CF3)2]4-, Al[OC[4-C6H4(tBu)](CF3)2]4-, Al(OC(Cy)(CF3)2]4-, and Al(OCPh2(CF3)]4-, have been determined by measuring their relative coordinating abilities towards Li+ in dichloromethane. The relative Li- Lewis basicities of the Al(ORF)4- ions are linearly related to the aqueous pKa values of the corresponding parent HORF fluoroalcohols. The Lewis basicity of Al[OCH(CF3)2]4- could not be measured because two of these anions can coordinate to one Li+ cation. The structures of LiAl[OCH(CF3)2]4 and [1-Et-3-Me-1,3-C3H3N2][Li[Al[OCH(CF3)2)4]2] were determined. 相似文献
45.
T. P. Cheng H. D. Anderson D. S. Mills V. L. Spate C. K. Baskett J. S. Morris 《Journal of Radioanalytical and Nuclear Chemistry》1997,217(2):171-174
An instrumental neutron activation analysis (INAA) technique, based on the19F(n,)20F reaction, has been development for the determination of fluoride in bone. The purpose was to study fluoride distribution in different kinds of bone samples using a rabbit model. The rationale for the study stems from the posible correlation between fluoride in bone and osteoporosis. The sodium concentration in the bone was used to correct the20F peak area for the23F(n,)20F contribution. Two secondary standards, teflon tape and teflon coated dacron line, were used to quantify fluoride concentration. They proved to be stable and consistent with respect to their fluoride concentration. Bone specimens from 10 sites and two tooth samples were analyzed for fluoride. Fluoride concentration ranged from 305 ppm in the tibia long bone to 585 ppm in the humerus trochanter end and the magnitude of fluoride concentration levels is age depdentent. The detection limit of the fluoride is approximately 5 ppm using a 100 mg bone sample. 相似文献
46.
M. V. Shimanskaya Ya. F. Oshis A. A. Anderson 《Chemistry of Heterocyclic Compounds》1983,19(12):1249-1262
The process of the catalytic synthesis of a number of nitrogenous heterocyclic compounds based on the utilization of reactions involving the amination of oxygen-containing heterocycles, the dehydration cyclization of amino alcohols, the deamination of di- and polyamines, and the intermolecular dehydration cyclization of glycols with diamines have been considered. 相似文献
47.
Investigations to eliminate defects in the incommensurate phase BaMnF4, led to a method of preparation at a temperature lower than the melting point of BaMnF4. Qualitative studies of the systems BaF2 -H2O -HF and MnF2 -H2O -HF showed that very pure single crystals of BaMnF4 could be grown at a temperature lower than 300°C. Several new phases could be isolated as single crystals, in particular: BaF2′HFSingle crystal X-ray analysis revealed the compound to be monoclinic (Space Group P21 and Z = 2) and confirmed the formula found by chemical analysis. However, because of the difficulty to distinguish between fluorine and oxygen atoms, some problems remain, which will be solved by neutron diffraction studies. Infrared analysis indicate the presence of HF?2 and suggest the following representation: (Ba2+)2(HF?2)2(F?)2.It is possible to extend this method of synthesis to the preparation of other fluorides and related compounds, in particular to those of europium and strontium. 相似文献
48.
Photophysics of monodisperse platinum-acetylide oligomers: delocalization in the singlet and triplet excited states 总被引:1,自引:0,他引:1
Liu Y Jiang S Glusac K Powell DH Anderson DF Schanze KS 《Journal of the American Chemical Society》2002,124(42):12412-12413
A series of monodisperse Pt-acetylide polymers that contain the [-CC-(p-C6H4)-CC-(t-Pt(PBu3)2)-]n repeat unit has been prepared for n = 1, 2, 3, 4, 5, and 7. The photophysical properties of the series provide information concerning the relationship between the oligomer length and delocalization in the singlet and triplet excited states of the pi-conjugated electron system. The results imply that the singlet excited state is delocalized over approximately 6 repeat units; however, the triplet state is considerably more localized. The triplet energy is almost invariant with oligomer length, but the phosphorescence spectra and triplet nonradiative decay rates indicate that the electron-vibrational coupling in the triplet state decreases with increasing oligomer length. 相似文献
49.
Kenneth J. Miller Robert J. Hinde Janet Anderson 《Journal of computational chemistry》1989,10(1):63-76
Matrix elements for the first and second derivatives of the internal coordinates with respect to Cartesian coordinates are reported for stretching, linear, nonlinear, and out-of-plane bending and torsional motion. Derivatives of the energy with respect to the Cartesian coordinates are calculated with the chain rule. Derivatives of the energy with respect to the internal coordinates are straightforward, but the calculation of the derivatives of the internal coordinates with respect to the Cartesian coordinates can be simplified by the following two steps outlined in this article. First, the number of terms in the analytical functions can be reduced or will vanish when the derivatives of the bond length, bond angle, and torsion angle are reported in a local coordinate system in which one bond lies on an axis and an adjacent bond lies in the plane of two axes or is projected onto perpendicular planes for linear and out-of-plane bending motion. Second, a simple rotation transforms these derivatives to the appropriate orientation in the space-fixed molecular coordinate system. Functions of the internal coordinates are invariant with respect to translation and rotation. The translational invariance and the symmetry of the second derivatives for a system with L atoms are used to select L-1- and L(L-1)/2-independent first and second derivatives, respectively, of which approximately half of the latter vanish in the local coordinate system. The rotational invariance permits the transformation of the simplified derivatives in the local coordinate system to any orientation in space. The approach outlined in this article simplifies the formulas by expressing them in a local coordinate system, identifies the most convenient independent elements to compute, from which the dependent ones are calculated, and defines a transformation to the space-fixed molecular coordinate system. 相似文献
50.
Plastic microchannels (4.5 cm long) fabricated from an etched glass master were tested for high-resolution single-stranded DNA analysis. Using replaceable denaturing linear polyacrylamide as sieving matrix, one-color separation of a fragment sizing standard with single-base resolution (R > 0.5) was achieved up to 275 bases. Two-color sizing analysis of four loci short tandem repeat (STR) allelic ladder (CSF1PO, TPOX, TH01, vWA) with single-base resolution (R = 0.62) on TH01 alleles 9.3 (198 bp) and 10 (199 bp) was demonstrated. An average standard deviation of +/- 0.06 bp and +/-0.11 bp in sizing 32 alleles of the CTTv ladder was attained between runs and between channels, respectively. Four-color sequencing separation of a terminator sequencing standard showed a base-calling accuracy of 99.1% out to 320 bases in 13 min. 相似文献