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1.
2.
Laser photolysis of benzoyl radical precursors (such as PhCOC[OH]R2 ) in oxygen-containing solutions leads to a laser-specific cascade of oxidative events in which benzoyl peroxyl radicals undergo self-reaction, ultimately leading to the sequential formation of benzoyloxyl, phenyl and phenyl peroxyl radicals. Thus, photoreactions producing benzoyl (PheO) radicals lead to PhĊO under conditions where benzoyl radicals do not decarbonylate. These reactions require the high-intensity conditions that can only be achieved under pulsed laser excitation; yet, they do not involve any multiphoton processes. Type I mechanisms of this type may be of importance as new laser-based therapeutic technologies are developed. 相似文献
3.
Shearer J Jackson HL Schweitzer D Rittenberg DK Leavy TM Kaminsky W Scarrow RC Kovacs JA 《Journal of the American Chemical Society》2002,124(38):11417-11428
Nitrile hydratase (NHase) is an iron-containing metalloenzyme that converts nitriles to amides. The mechanism by which this biochemical reaction occurs is unknown. One mechanism that has been proposed involves nucleophilic attack of an Fe-bound nitrile by water (or hydroxide). Reported herein is a five-coordinate model compound ([Fe(III)(S(2)(Me2)N(3)(Et,Pr))](+)) containing Fe(III) in an environment resembling that of NHase, which reversibly binds a variety of nitriles, alcohols, amines, and thiocyanate. XAS shows that five-coordinate [Fe(III)(S(2)(Me2)N(3)(Et,Pr))](+) reacts with both methanol and acetonitrile to afford a six-coordinate solvent-bound complex. Competitive binding studies demonstrate that MeCN preferentially binds over ROH, suggesting that nitriles would be capable of displacing the H(2)O coordinated to the iron site of NHase. Thermodynamic parameters were determined for acetonitrile (DeltaH = -6.2(+/-0.2) kcal/mol, DeltaS = -29.4(+/-0.8) eu), benzonitrile (-4.2(+/-0.6) kcal/mol, DeltaS = -18(+/-3) eu), and pyridine (DeltaH = -8(+/-1) kcal/mol, DeltaS = -41(+/-6) eu) binding to [Fe(III)(S(2)(Me2)N(3)(Et,Pr))](+) using variable-temperature electronic absorption spectroscopy. Ligand exchange kinetics were examined for acetonitrile, iso-propylnitrile, benzonitrile, and 4-tert-butylpyridine using (13)C NMR line-broadening analysis, at a variety of temperatures. Activation parameters for ligand exchange were determined to be DeltaH(+ +) = 7.1(+/-0.8) kcal/mol, DeltaS(+ +) = -10(+/-1) eu (acetonitrile), DeltaH(+ +) = 5.4(+/-0.6) kcal/mol, DeltaS(+ +) = -17(+/-2) eu (iso-propionitrile), DeltaH(+ +) = 4.9(+/-0.8) kcal/mol, DeltaS(+ +) = -20(+/-3) eu (benzonitrile), and DeltaH(+ +) = 4.7(+/-1.4) kcal/mol DeltaS(+ +) = -18(+/-2) eu (4-tert-butylpyridine). The thermodynamic parameters for pyridine binding to a related complex, [Fe(III)(S(2)(Me2)N(3)(Pr,Pr))](+) (DeltaH = -5.9(+/-0.8) kcal/mol, DeltaS = -24(+/-3) eu), are also reported, as well as kinetic parameters for 4-tert-butylpyridine exchange (DeltaH(+ +) = 3.1(+/-0.8) kcal/mol, DeltaS(+ +) = -25(+/-3) eu). These data show for the first time that, when it is contained in a ligand environment similar to that of NHase, Fe(III) is capable of forming a stable complex with nitriles. Also, the rates of ligand exchange demonstrate that low-spin Fe(III) in this ligand environment is more labile than expected. Furthermore, comparison of [Fe(III)(S(2)(Me2)N(3)(Et,Pr))](+) and [Fe(III)(S(2)(Me2)N(3)(Pr,Pr))](+) demonstrates how minor distortions induced by ligand constraints can dramatically alter the reactivity of a metal complex. 相似文献
4.
Kariuki NN Luo J Maye MM Hassan SA Menard T Naslund HR Lin Y Wang C Engelhard MH Zhong CJ 《Langmuir : the ACS journal of surfaces and colloids》2004,20(25):11240-11246
This paper reports findings of an investigation of the synthesis of monolayer-capped binary gold-silver (AuAg) bimetallic nanoparticles that is aimed at understanding the control factors governing the formation of the bimetallic compositions. The synthesis of alkanethiolate-capped AuAg nanoparticles was carried out using two related synthetic protocols using aqueous sodium borohydride as a reducing agent. One involves a two-phase reduction of AuCl(4)(-), which is dissolved in organic solution, and Ag(+), which is dissolved in aqueous solution. The other protocol involves a two-phase reduction of AuCl(4)(-) and AgBr(2)(-), both of which are dissolved in the same organic solution. AuAg nanoparticles of 2-3 nm core sizes with different compositions in the range of 0-100% Au have been synthesized. The two synthetic routes were compared in terms of bimetallic composition and size properties. Our new findings have allowed us to establish the correlation between synthetic feeding of metals and metal compositions in the bimetallic nanoparticles, which have important implications to the exploration of gold-based bimetallic nanoparticles for constructing sensing and catalytic nanomaterials. 相似文献
5.
L. K. Kostov W. Andrejtscheff L. G. Kostova A. Dewald G. Böhm K. O. Zell P. von Brentano 《Zeitschrift für Physik A Hadrons and Nuclei》1994,348(2):79-86
Applying delayed- r.f. coincidences and generalized centroid-shift analysis, nanosecond isomers in some odd-A iodine isotopes are studied in-beam. The reactions106Cd(12C,p2n) and116,118Sn(6Li,3n) have been used. The following half-lives were determined:T
1/2(565 keV)=0.50±0.10 ns andT
1/2(837 keV) =0.90±0.20 ns in115I,T
1/2(687 keV)=5.50±0.50 ns andT
1/2(2418 keV)=4.0±0.50 ns in119I as well asT
1/2(812 keV)=0.35±0.20 ns andT
1/2(445 keV)<0.10 ns=">0.10>121I. A systematics of the absolute probabilities for the transitions deexciting theg
9/2 9/2+ and
11/2 11/2
1
–
band heads in115–125I is presented and discussed.Partly supported by the Bulgarian National Research Foundation under contracts PH14, and PH31 and Kernforschungszentrum Karlsruhe, Stabsabteilung Internationale Beziehungen 相似文献
6.
L. G. Kostova W. Andrejtscheff L. K. Kostov L. Funke E. Will A. I. Vdovin 《Zeitschrift für Physik A Hadrons and Nuclei》1992,342(2):145-148
Using the (,n) reaction, the half-life of the first 11/2– level in97Mo has been determined as T1/2(1437.0 keV)=2.5±0.3 ns by means of the pulsed beam method. The experimentally obtainedB(M2) value between theh
11/2 andg
7/2 configurations in97Mo has been satisfactorily described within the quasiparticle-phonon model usingg
s
eff
=0.6g
s
free
. Similar calculations and comparisons with experminental data have been performed also for95,99Mo as well as for99Ru and101Pd.This work is partly supported by the Bulgarian National Research Foundation 相似文献
7.
Quinazoline is a heterocyclic compound having biological activities. It is aromatic in nature having bicyclic structure containing benzene ring and pyrimidine ring. Quinazoline and its derivatives are found to have wide range of biological activities that is anticancer, analgesic, antimicrobial, antihypertensive, anticonvulsant, antimalarial, antitumor, and anti-tubercular activities. The purpose of this review is to highlight the recent researches made by researchers on various biological activities of quinazoline derivatives on different targets. 相似文献
8.
9.
The reactions of N-alkylaryl-and N, N′-dialkylarylureas with aldehydes in acidic medium leads to the synthesis of N-carbamoyltetrahydro-isoquinolines and tetrahydro-1,3,5-oxadiazin-4-ones (urons) depending on the structure of starting compounds and the reaction conditions. 相似文献