Ultraviolet photolysis of CH2I2 in methanol: O-H insertion and HI elimination reactions to form a dimethoxymethane product

Ultraviolet photolysis of low concentrations of CH2I2 in methanol solution found that CH2I2 is converted into dimethoxymethane and some H+ and I- products. Picosecond time-resolved resonance Raman (ps-TR3) experiments observed that the isodiiodomethane (CH2I-I) photoproduct decayed faster as the concentration of methanol increases, suggesting that isodiiodomethane is reacting with methanol. Ab initio calculations indicate isodiiodomethane is able to react with methanol via an O-H insertion/HI elimination to form an iodoether (ICH2-O-CH3) and HI products. The iodoether can then further react via another O-H insertion/HI elimination reaction to form the dimethoxymethane (CH3-O-CH2-O-CH3) observed in the photochemistry experiments. A reaction mechanism consistent with these experimental and theoretical observations is proposed.     

Comparison of the dehalogenation of dihalomethanes (CH2XI, where X = Cl, Br, I) following ultraviolet photolysis in aqueous and NaCl saltwater environments

The ultraviolet photolysis of low concentrations of CH(2)XI (X = Cl, Br, I) were investigated in water and saltwater solutions by photochemistry and picosecond time-resolved resonance Raman spectroscopy. Photolysis in both kinds of solutions formed mostly CH(2)(OH)(2) and HI and HX products. However, photolysis of the CH(2)XI molecules in saltwater resulted in production of some CH(2)XCl products not observed in aqueous solutions without salt present. The appearance of these new products in saltwater solutions is accompanied by a decrease in the amount of CH(2)(OH)(2), HI, and HX products compared to photolysis in aqueous solutions without salt present. The possible implications for photolysis of CH(2)XI and other polyhalomethanes in seawater and other salt aqueous environments compared to nonsaltwater solvated environments is briefly discussed.     

GaAs(100)解理面的能带弯曲

在真空中解理后,用XPS测得了GaAs样品（110）断面能带弯曲的动态过程．两组重掺杂n型和p型GaAs样品的费米能级分别向禁带中间的方向移动了0.4eV和0．3eV.实验测得重掺杂n型和p型GaAs样品费米能级之差为1．3eV,它们的禁带宽度理论值为1．42eV,这说明结果是合理的．根据实验结果,对引起GaAs表面能带弯曲的可能原因进行了分析讨论．排除了本征表面态、真空中残留气体和X射线辐射等原因,认为解理过程在表面产生的缺陷和解理后表面晶格弛豫过程中产生的缺陷可能是导致能带弯曲的主要原因．     

A circular ferrofluid driven microchip for rapid polymerase chain reaction

In the past few years, much attention has been paid to the development of miniaturized polymerase chain reaction (PCR) devices. After a continuous flow (CF) PCR chip was introduced, several CFPCR systems employing various pumping mechanisms were reported. However, the use of pumps increases cost and imposes a high requirement on microchip bonding integrity due to the application of high pressure. Other significant limitations of CFPCR devices include the large footprint of the microchip and the fixed cycle number which is dictated by the channel layout. In this paper, we present a novel circular close-loop ferrofluid driven microchip for rapid PCR. A small ferrofluid plug, containing sub-domain magnetic particles in a liquid carrier, is driven by an external magnet along the circular microchannel, which in turn propels the PCR mixture through three temperature zones. Amplification of a 500 bp lambda DNA fragment has been demonstrated on the polymethyl methacrylate (PMMA) PCR microchip fabricated by CO(2) laser ablation and bonded by a low pressure, high temperature technique. Successful PCR was achieved in less than 4 min. Effects of cycle number and cycle time on PCR products were investigated. Using a magnet as the actuator eliminates the need for expensive pumps and provides advantages of low cost, small power consumption, low requirement on bonding strength and flexible number of PCR cycles. Furthermore, the microchip has a much simpler design and smaller footprint compared to the rectangular serpentine CFPCR devices. To demonstrate its application in forensics, a 16-loci short tandem repeat (STR) sample was successfully amplified using the PCR microchip.     

A theoretical investigation of P-hydroxyphenacyl caged phototrigger compounds: how water induces the photodeprotection and subsequent rearrangement reactions

Complete active-space self-consistent field (CASSCF) calculations with a (14,11) active space and density functional theory calculations followed by Car-Parrinello molecular dynamic simulations are reported for the p-hydroxyphenacyl acetate, diethyl phosphate, and diphenyl phosphate phototrigger compounds. These calculations considered the explicit hydrogen bonding of water molecules to the phototrigger compound and help reveal the role of water in promoting the photodeprotection and subsequent rearrangement reactions for the p-hydroxyphenacyl caged phototrigger compounds experimentally observed in the presence of appreciable amounts of water but not observed in neat nonproton solvents like acetonitrile. The 267 nm excitation of the phototrigger compounds leads to an instantaneous population of the S3(1pipi*) state Franck-Condon region, which is followed by an internal conversion deactivation route to the S1(1npi*) state via a 1pipi*/1npi* vibronic coupling. The shorter lifetime of the S1(1npi*) state (approximately 1 ps) starting from the FC geometry is terminated by a fast intersystem crossing at a 3pipi*/3npi* intersection with a structure of mixed pipi*/npi* excitation in the triplet state. The deprotection reaction is triggered by a proton (or hydrogen atom) transfer assisted by water bridges and emanates from this pipi*/npi* triplet state intersection. With the departure of the leaving group, the reaction evolves into a water-mediated post-deprotection phase where the spin inversion of pQM (X, 3A) leads to a spiroketone in the ground state by a cyclization process that is followed by an attack of water to produce a 1,1'-di-hydroxyl-spiroketone. Finally, the H atom of the hydroxyl in 1,1'-di-hydroxyl-spiroketon transfers back to the p-O atom aided by water molecules to generate the p-hydroxyphenyl-acetic acid final rearrangement product.     

A falling body problem through the air in view of the fractional derivative approach

Recent studies have revealed that the fractional derivative can behave as a dissipative term. The analysis of a simple fractional oscillator has supported this point of view. However, other physical aspects related to fractional derivative are also important to be explored. For this purpose, in this work, we employ the fractional approach and guide ourselves by the above property to investigate the falling body problem. We show that the velocity of a falling body, in the fractional approach, can be greater (t<1) or less (t>1) than that velocity of free-fall obtained by the usual approach. Moreover, we show that the fractional derivative alone is not sufficient to attain a terminal speed. In order to provide a terminal speed into the fractional system a term, proportional to velocity, must be introduced.     

Effect of Heavy‐Atom (Br) at the Phenyl Rings of Schiff‐Base Ligands on the NIR Luminescence of their Bimetallic Zn‐Nd Complexes

Two heterobimetallic Zn‐Nd phenylene‐bridged Schiff‐base ligands complexes [ZnNd L¹ (Py)(NO₃)₃] ( 1 ) and [Zn L² Nd(Py)(NO₃)₃]·MeCN ( 2 ) (Py = pyridine, H₂L¹ = N,N′‐bis‐ (3‐methoxy‐salicylidene)phenylene‐1,2‐diamine, H₂L² = N,N′‐bis‐5‐bromo‐3‐methoxy‐salicylidene)phenylene‐1,2‐diamine) were obtained. Both 1 and 2 were structurally characterized by X‐ray crystallography, and their near‐infrared (NIR) luminescent properties were determined. For the two complexes, the occupation of pyridine at the axial position of 3d Zn²⁺ ions could effectively prevent luminescent quenching arising from OH‐, NH‐ or CH oscillators of the solvates around the 4f Nd³⁺ ions, and the heavy‐atom (Br) effect of the Schiff‐base ligands on their NIR luminescent properties is also discussed.     

Crystal structure of a non-stoichiometric channel inclusion complex of 1-benzyl-6-phenylpiperidin-2-one-5-carboxylic acid with acetonitrile

C₁₉H₁₉NO₃·x CH₃CN (x=0.3),M _r=643.35, hexagonal, space groupP6₁ (No. 169),a=23.027(5),c=5.775(1) Å,V=2652(1) ų,Z=6. The structure was solved by direct methods and refined toR=0.077 for 1562 observed MoK reflections. The title heterocyclic carboxylic acid was established as thetrans isomer, with the phenyl and carboxyl substituents occupying pseudo-equatorial and equatorial positions, respectively, of the piperidin-2-one ring in a half-chair conformation. Acid host molecules related by the 6₁ screw operation are linked by intermolecular O–H...O (cyclic amide) hydrogen bonds to generate an open channel bounded by coaxial intertwined helices each having a pitch of 5c. Within each channel of free diameterca. 6.0 Å the acetonitrile molecules partially occupy highly disordered sites which do not lie on thec axis. Supplementary Data relating to this article are deposited with the British Library as Supplementary Publication No. SUP 82067 (13 pages).