Heat Capacity and DC-Magnetic Susceptibility Evidence for the Asymmetry of Electron Spin-Flip Phase Transition of N+H center dot center dot center dot O- Bond in Chiral Alanine Crystal
文献类型：期刊论文
| 作者 | Wang Wen-Qing1; Shen Xin-Chun1,2; Wu Ji-Lan1; Gong Yan1; Shen Guo-Hua1; Zhao Hong-Kai1 |
| 刊名 | ACTA PHYSICO-CHIMICA SINICA
 |
| 出版日期 | 2012-04-01 |
| 卷号 | 28期号:4页码:773-780 |
| 关键词 | Heat Capacity Dc-magnetic Susceptibility n+Center Dot Center Dot Center Dot O- Bonding Electron Spin-flip Asymmetry Transition D- And L-alanine Crystals |
| ISSN号 | 1000-6818 |
| DOI | 10.3866/PKU.WHXB201202132 |
| 英文摘要 | With a view to understanding the argument of phase-transition mechanisms of D- and L-alanine at around 270 K, the temperature dependence of heat capacity measurements was investigated, for single crystals, ground powders, and polycrystalline products, using differential scanning calorimetry (DSC). The C-p (heat capacity under constant pressure) values of D- and L-alanine were calibrated with standard sapphire by the triple-curve method; these values coincide with the standard C-p values in the literature. Endothermic transition peaks were observed at T-c=272.02 K, Delta H=10.87 J.mol(-1) and Tc=271.85 K, Delta H=1.46 J.mol(-1) for D- and L-alanine, respectively, and T-c=273.59 K, Delta H=1.75 J.mol(-1) and T-c=273.76 K. Delta H=1.57 J.mol(-1) for the reference crystals D- and L-valine, respectively. The energy differences of 0.41 J.mol(-1) for D-and L-alanine and 0.18 J.mol(-1) for D- and L-valine, which were observed from pre-aligned molecules in the single crystals and vanished in the ground powders and polycrystalline products, show that the phase transition is related to the crystal lattice. Neutron diffraction results exclude the possibility of a D -> L configuration change, and show that the hydrogen bonds run antiparallel to the c-axis in the D- and L-crystals. Polarized Raman vibrational spectroscopy shows that the transition mechanism may be related to the electronic orbital angular momentum and magnetic dipole moments of N+H center dot center dot center dot O- in the crystals. External magnetic fields, H=+1, -1 T, were applied parallel to the c(z)-axis of the D- and L-alanine crystalline lattices, respectively. The DC-magnetic susceptibilities show electron spin-flip transitions at around 270 K in D- and L-alanine. The spin is "up" or "down" relative to the direction of N+H center dot center dot center dot O- bond along the c(z)-axis. Based on spin rigidity and magnetic anisotropy, the results help to explain the discrepancies among heat capacity and magnetic susceptibility data for single crystals and polycrystalline powders of D- and L-alanine. |
| 语种 | 英语 |
| WOS记录号 | WOS:000302764400005 |
| 出版者 | PEKING UNIV PRESS |
| 源URL | [http://ir.iccas.ac.cn/handle/121111/47109]  |
| 专题 | 中国科学院化学研究所 |
| 通讯作者 | Wang Wen-Qing |
| 作者单位 | 1.Peking Univ, Coll Chem & Mol Engn, Dept Appl Chem, Beijing Natl Lab Mol Sci, Beijing 100871, Peoples R China 2.Shandong Univ, Sch Chem & Chem Engn, Jinan 250061, Peoples R China |
| 推荐引用方式 GB/T 7714 | Wang Wen-Qing,Shen Xin-Chun,Wu Ji-Lan,et al. Heat Capacity and DC-Magnetic Susceptibility Evidence for the Asymmetry of Electron Spin-Flip Phase Transition of N+H center dot center dot center dot O- Bond in Chiral Alanine Crystal[J]. ACTA PHYSICO-CHIMICA SINICA,2012,28(4):773-780. |
| APA | Wang Wen-Qing,Shen Xin-Chun,Wu Ji-Lan,Gong Yan,Shen Guo-Hua,&Zhao Hong-Kai.(2012).Heat Capacity and DC-Magnetic Susceptibility Evidence for the Asymmetry of Electron Spin-Flip Phase Transition of N+H center dot center dot center dot O- Bond in Chiral Alanine Crystal.ACTA PHYSICO-CHIMICA SINICA,28(4),773-780. |
| MLA | Wang Wen-Qing,et al."Heat Capacity and DC-Magnetic Susceptibility Evidence for the Asymmetry of Electron Spin-Flip Phase Transition of N+H center dot center dot center dot O- Bond in Chiral Alanine Crystal".ACTA PHYSICO-CHIMICA SINICA 28.4(2012):773-780. |
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来源：化学研究所
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