高聚合度Ⅱ-型聚磷酸铵的合成

用聚合反应-热处理两段工艺合成了高聚合度的聚磷酸铵（APP）阻燃材料,其结构经XRD,粒度及平均聚合度表征。优化反应条件为：磷酸氢二铵1mol,n（磷酸氢二铵）：n（五氧化二磷）：n（脲）：1．0：1．0：0．3．干燥氨气氛下于290℃反应30min,再经250℃-280℃后处理100min-110min。APP的平均聚合度大于150,粒度小于50μm。     

Multiphonon energy gap law in rare-earth doped chalcogenide glass

The parameters for multiphonon relaxation of rare earth (RE) ions in the sulfide glass Ge₂₅As_8.33Ga_1.67S₆₅ have been re-evaluated using the temperature dependence of the fluorescence lifetime to separate out true multiphonon decay from other non-radiative processes. It is found that for energy gaps to the next lowest level greater than 2500 cm⁻¹, other non-radiative processes become dominant over multiphonon decay. The most likely process for this additional non-radiative decay is energy transfer to vibrational impurities such as OH and SH. The newly derived parameters lead to an electron–phonon coupling parameter ε=0.058, which is more in line with other glass types than the previously accepted value of ε=0.36. These new multiphonon relaxation parameters and the existence of additional non-radiative decay mechanisms has implications for the modeling of chalcogenide-based active devices.     

The X-ray Structures of (R)-2,2′-Dimethyl-1,1′-binaphthyl and (±)-2-Bromomethyl-2′-dibromomethyl-1,1′-binaphthyl

Journal of Chemical Crystallography - Molecular structures of (R)-2,2′-dimethyl-1,1′-binaphthyl [monoclinic, a?=?11.24420 (11), b?=?10.56190 (9),...     

Chemical repercussions of orbital interactions through bond and through space The reactivity of the double bond in unsaturated cyclic sulphones towards aziridine formation and epoxidation

The ease of formation of aziridine and/or epoxides from a series of bicyclic olefins, where distant sulphonyl groups are present, is very variable. There is some correlation between reactivity of the vinyl group and its π-ionisation potential which is high in the present molecules relative to comparison olefins. This increase is thought to be due to the presence of orbital interactions through bonds and/or through space between the sulphone group and the double bond, making the latter electron deficient. The ionisation potentials were determined by UV-photoelectron spectroscopy and the assignments made by recourse to ab initio configuration interaction methods.     

Bonding in HNO-myoglobin as characterized by X-ray absorption and resonance raman spectroscopies

The EXAFS and resonance Raman spectra on the HNO-myoglobin adduct, 1, are consistent with the presence of HNO bound to a heme center. The three-dimensional structure about the heme center of 1 obtained from multiple-scattering (MS) analysis of the EXAFS of the heme protein yielded an Fe-N-O bond angle of 131 degrees and an Fe-N bond length of 1.82 A, which compare well with published values for model complexes containing RNO ligands. Resonance Raman spectra identified the nu(N=O) stretch at 1385 cm-1 (confirmed by 15N labeling), which corresponds well with those reported for small molecule HNO complexes. The wavelength of the nu(Fe-N) at 636 cm-1 of 1 is significantly higher than those of MbIINO and MbIIINO (554 and 595 cm-1, respectively). The XAFS, XANES, and resonance Raman data are all consistent with the structure deduced from the NMR experiments, providing more detail on the bonding between HNO and the metal center.