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1.
Birch SJ Boss SR Cole SC Coles MP Haigh R Hitchcock PB Wheatley AE 《Dalton transactions (Cambridge, England : 2003)》2004,(21):3568-3574
Dimethylzinc reacts with an excess of N-2-pyridylaniline 6 to give the homoleptic species, Zn[PhN(2-C(5)H(4)N)](2) 8. Single crystal X-ray diffraction reveals a solid-state dimer based on an 8-membered (NCNZn)(2) core motif. Zn[CyN(2-C(5)H(4)N)]Me (Cy =c-C(6)H(11)) 10, prepared by the combination of ZnMe(2) with the corresponding cyclohexyl-substituted pyridylamine, is also dimeric in the solid state but reveals a central (ZnN)(2) metallacycle. Employment of (p-Tol)NH(2-C(5)H(4)N)(p-Tol = 4-MeC(6)H(4)) 11 yielded the tris(zinc) adduct Zn(3)[(p-Tol)N(2-C(5)H(4)N)](4)Me(2) 12, which incorporates a central chiral molecule of 'Zn[(p-Tol)N(2-C(5)H(4)N)](2)' 12a, that bridges two 'Zn[(p-Tol)N(2-C(5)H(4)N)]Me' 12b units. A similar trimetallic structure is noted when the pyridylaniline substrate 11 is replaced with the bicyclic guanidine 1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidine (hppH), affording Zn(3)(hpp)(4)Me(2) 13. Spectroscopic studies point to retention of the solid-state structure of in hydrocarbon solution. Reaction of 13 with dimesityl borinic acid, Mes(2)BOH (Mes = mesityl), affords Zn(3)(hpp)(4)(OBMes(2))(2) 14 in which the trimetallic core is retained. This reactivity is in contrast to the closely related reaction of dimeric Zn[Me(2)NC[N(i)Pr](2)]Me 15 with Mes(2)BOH, which yielded Zn[Me(2)NC[N(i)Pr](2)][OBMes(2)].Me(2)NC[N(i)Pr][NH(i)Pr] 16 as a result of protonation at the guanidine ligand in addition to the Zn-Me bond. 相似文献
2.
The lifetimes of 9,10-diphenylanthracene in dilute solutions of cyclohexane and benzene at 25°C have been found to be 7.58 ± 0.04 and 6.95 ± 0.04 ns respectively. Measurements of the relative quantum yields show that the dependence on the solvent is caused by an increased probability for non-radiative decay in benzene compared with cyclohexane. This behaviour is shown to partly reconcile previous conflicting data on the radiative properties of this molecule. 相似文献
3.
B.M.Ratnayake Bandara Arthur J. Birch Brian Chauncy Lawrence F. Kelly 《Journal of organometallic chemistry》1981,208(2):C31-C35
Complexation commencing with some substituted 1,3- or 1,4-cyclohexadienes with Fe(CO)5 indicates that the steric direction is controlled by classical hindrance with groups such as alkyl, but probably involves transmission of the entering group through intermediate complexation with CO2Me. The results help to define methods of obtaining desired stereoisomers in the series. 相似文献
4.
DETECTION OF DNA-PSORALEN PHOTOADDUCTS in situ 总被引:1,自引:0,他引:1
ZOFIA ZAREBSKA† MARIA JARZABEK-CHORZELSKA ‡ GENOWEFA RZSA WIESLAW GLISKI MARIA PAWIKA TADEUSZ CHORZELSKI STEFANIA JABLOKA 《Photochemistry and photobiology》1984,39(3):307-312
Abstract— An immunological method, with the use of specific immune serum, has been developed for detection of 8-methoxypsoralen (8-MOP) photoadducts to DNA, formed in situ in cell nuclei, after combined treatment with 8MOP and UV-A irradiation (Zarçbska et al. , 1978). Lymphocytes fixed on slides or in suspension, and cryostat sections of different mammalian tissues, served as antigenic substrate, after treatment with 8-MOP and UV-A in vitro. Specific fluorescence in these substrates was detected in the nuclei after treatment with 30 ˜ 140 kJ/m2 UV-A in the presence of 0.1-0.3 μg/cm2 8-MOP. PHA-stimulated-lymphocytes appeared to be the most sensitive substrate.
However, hairless mice treated with high doses of UV-A in vivo , 70 ˜ 360 kJ/m2 did not reveal a specific fluorescence of epidermal nuclei, unless a high local concentration of 8-MOP was attained.
The apparent discrepancy in the level of photoadduct detection between the in vitro and in vivo treated specimens was explained by the low number of DNA-8-MOP-photoadducts formed in vivo under these experimental conditions. The relevance of these findings to the role of DNA-8-MOP-photoadducts formed during PUVA photochemotherapy is discussed. 相似文献
However, hairless mice treated with high doses of UV-A in vivo , 70 ˜ 360 kJ/m
The apparent discrepancy in the level of photoadduct detection between the in vitro and in vivo treated specimens was explained by the low number of DNA-8-MOP-photoadducts formed in vivo under these experimental conditions. The relevance of these findings to the role of DNA-8-MOP-photoadducts formed during PUVA photochemotherapy is discussed. 相似文献
5.
The fluorescence lifetime of trans-stilbene in dilute methylcyclohexane/iso-hexane solution has been measured and the mean S1 radiative (kF), radiationless (kI) and cis-isomerization (kC) rate parameters have been determined from ?90 to 60°C. Si consists of a fluorescent trans (1Bu*) state (kF0 = 6.0 × 108 s?1) which undergoes reversible thermal-activated rotational internal conversion (ΔH = 1.75 kcal mole?1, ΔS = 10.6 cal deg?1 mole?1) to a non-fluorescent perp (1Ag*) state. p(1Ag*) lies 610 cm?1 above t (1Bu*) with an intermediate S1 potential maximum. p(1Ag*) undergoes internal conversion(kI.∞ = 5.8 × 108 s?1) to p (1Ag) leading to cis-isomerization. This is the main isomerization channel over the whole temperature range. 相似文献
6.
A. J. Birch D. Van Os V. Dykstra und I. Herold 《Fresenius' Journal of Analytical Chemistry》1943,125(1-2):57-58
Ohne Zusammenfassung 相似文献
7.
This report describes a gated sampling approach for studying the initial formation of sol-gel glasses prepared from sodium silicate solution (water glass) and sulphuric acid. Previously described were how changes in particle size and subsequently how sol-gel formation dynamics can be tracked using time-resolved fluorescence anisotropy, by labeling growing silica nanoparticles with suitable fluorescence probes. One limiting factor of this approach was the 2 minute measurement time, which limits this technique for studying the initial sol formation dynamics and limits the measurement precision. Using a continuous flow system and delaying sol flow through different tubing lengths overcomes this problem and allows monitoring of the very early stages of sol formation, second by second after sol preparation, irrespective of the anisotropy measurement time. This technique was applied to studying the initial formation dynamics, within the first 30 seconds, of a 12.01% SiO2 (w/w), pH 0.66 sol-gel, finding that silica particles of 1.5 nm mean radius are formed within 10 seconds of mixing the sol-gel. 相似文献
8.
Birch P Tan S Young R Koukoulas T Claret-Tournier F Budgett D Chatwin C 《Optics letters》2001,26(8):494-496
We present the implementation of a clutter-tolerant filter in a hybrid correlator system. Wiener filters were mapped with a complex encoding technique onto a smectic A(*) liquid-crystal spatial light modulator (SLM). The technique overcomes the problem of representing high-dynamic-range data on SLM's that have limited modulation capabilities. It also provides a compact image recognition system that is robust enough for many real-world applications. Experimental results are presented. 相似文献
9.
Sasidhar Chavali Philip M. Birch Rupert Young Chris Chatwin 《Optics and Lasers in Engineering》2007,45(3):413
Achieving phase only modulation from a spatial light modulator (SLM) is useful for many optical processing tasks. In this paper, we demonstrate a simple method of decoupling phase and amplitude modulation in a twisted nematic liquid crystal (TNLC) SLM using a double pass technique. A Jones calculus model is developed which matches our experimental data. 相似文献
10.