物理化学学报 >> 2013, Vol. 29 >> Issue (07): 1396-1400.doi: 10.3866/PKU.WHXB201304163

热力学,动力学和结构化学 上一篇    下一篇

D-和L-丙氨酸晶体的突现顺磁性: 准一维N+H…O-氢键的自旋-轨道分离

王文清1, 沈新春1,2, 张玉凤1,3, 龚1,3   

  1. 1 北京大学化学与分子工程学院应用化学系, 北京分子科学国家实验室, 北京 100871;
    2 山东大学化学与分子工程学院, 济南 250061;
    3 北京服装学院材料科学与工程学院, 北京 100029
  • 收稿日期:2013-02-21 修回日期:2013-04-15 发布日期:2013-06-14
  • 通讯作者: 王文清 E-mail:wangwqchem@pku.edu.cn
  • 基金资助:

    国家自然科学基金(21002006, 20452002)和国家科技部基础研究重大项目(2004-973-36)资助

Emergent Paramagnetism in D- and L-Alanine Crystals: Spin-Orbital Separation in Quasi-One-Dimensional N+H…O? Bonds

WANG Wen-Qing1, SHEN Xin-Chun1,2, ZHANG Yu-Feng1,3, GONG Yan1,3   

  1. 1 Beijing National Laboratory for Molecular Sciences, Department of Applied Chemistry, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, P. R. China;
    2 School of Chemistry and Chemical Engineering, Shandong University, Jinan 250061, P. R. China;
    3 Beijing Key Laboratory of Clothing Materials R&D and Assessment, School of Materials Science & Engineering, Beijing Institute of Fashion Technology, Beijing 100029, P. R. China
  • Received:2013-02-21 Revised:2013-04-15 Published:2013-06-14
  • Supported by:

    The project was supported by the National Natural Science Foundation of China (21002006, 20452002) and Special Program for Key Basic Research of the Ministry of Science and Technology, China (2004-973-36).

摘要:

研究了与磁场强度相关的手性丙氨酸晶体的电子轨道运动的磁性质. 根据丙氨酸单晶的两性离子(+NH3-C(CH3)H-CO2-)模型的手性和蛋白质中肽键晶格结构的螺旋性, 当外加磁场为5 T, 磁场方向平行于丙氨酸晶轴(c)的极性N+H…O-氢键, 观察到D-丙氨酸晶格中, 氢原子的电子自旋翻转, 在297.6 K直接突现顺磁性. L-丙氨酸则先发生电子自旋转向, 然后在303.9 K突现顺磁性. 实验发现: 外加强磁场可以分裂手性丙氨酸晶格中氢键的简并顺磁态, 并测出能差. 本文进一步证明了准一维极性N+H…O-氢键在晶格中可以发生自旋-轨道分离, 表现出一维物理的基本特征.

关键词: D-和L-丙氨酸晶格, N+H…O?氢键, 突现顺磁性, 电子自旋翻转, 电子自旋转向, 简并顺磁态能差, 自旋-轨道分离

Abstract:

We investigated the field-dependent magnetic properties of chiral alanine crystals, especially associated with the electronic orbital motions. Based on the chirality of the zwitterionic model (+NH3-C(CH3)H-CO2-), and the helicity of the lattice structure of peptide bond in proteins, when an external field of +5 T was applied parallel to the preferred axis c(z) of the N+H…O- hydrogen bond in D-alanine, the electron spin-flip manifested emergent paramagnetism at 297.6 K. Because the spin magnetic dipole moment of hydrogen in L-alanine was originally aligned antiparallel to the field, the electron spins flipped firstly perpendicular to the field then manifested paramagnetism at 303.9 K. The magnetic field of 5 T split a degenerate energy level in the paramagnetic state of chiral alanine. Furthermore, the spin-orbital separation of the quasi-one dimensional N+H…O- hydrogen bond in the crystal lattice provided evidence for the hallmark of one-dimensional physics.

Key words: D- and L-alanine crystal lattices, N+H…O? hydrogen bond, Emergent paramagnetism, Electron spin-flip, Electron spin-flop, Energy difference of degenerate paramagnetic state, Spin-orbital separation

MSC2000: 

  • O641