Acta Phys. -Chim. Sin. ›› 2013, Vol. 29 ›› Issue (07): 1396-1400.doi: 10.3866/PKU.WHXB201304163

• THERMODYNAMICS, KINETICS, AND STRUCTURAL CHEMISTRY • Previous Articles     Next Articles

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).

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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