mirror symmetry breaking in the synthesis of cis-[CoBr(NH3)(en)2]Br2
- Paper number
IAC-13,A1,P,38.p1,x19983
- Author
Prof. Hui Zhang, Xiamen University, China
- Year
2013
- Abstract
In 1990, Asakura accidentally discovered the fantastic phenomenon of mirror symmetry breaking in the preparation of cis-[CoBr(NH3)(en)2]Br2[1-2]. Different from the “asymmetric autocatalysis” mechanism held by Asakura, we have proposed a new mechanism to explain the phenomenon of mirror symmetry breaking for some systems similar to such inert Co(III) complexes., which could be simply summarized as the racemization of the Δ- or Λ-Co(III) complex catalyzed by the electron transfer between Co(II) and Co(III) species in combination with the preparation of the single enantiomer induced by chiral crystals[3], i.e., “catalysis-crystal induction” mechanism. Fortunately, we have successfully observed the mirror symmetry breaking in the synthesis of cis-[CoBr(NH3)(en)2]Br2. Interestingly, the statistical results of repeated experiments over 376 times were 71 times for Δ-configuration, 164 times for Λ-configuration, and 141 times for rac-configuration respectively. According to the above mechanism, we have also further improved the preparation methods of chiral cis-[CoBr(NH3)(en)2]Br2, by adding the chiral crystal seeds to induce the chiralselective synthesis of chiral products without any resolution agents. And the chiral crystals of cis-[CoBr(NH3)(en)2]Br2 were prismatic, while the achiral crystals are needle-like or flake. Hopefully, these results could provide some usefully evidence for exploring the origin of chirality. Reference [1] Asakura, K.; Kobayashi, K.; Mizusawa, Y.; Ozawa, S.; Osanai, S.; Yoshikawa, S. Physica, D., 1995, 84(1-2): 72-78. [2] Asakura, K.; Kondepudi, D. K.; Martin, R. Chirality, 1998, 10(4): 343-348. [3] Zhang, H.; Wang, X.Y.; Chen L. Q.; Fang, X. M.; Gao, J.X.; Xu, Z.G. Acta Phys. –Chim. Sin., 2006, 22(5): 608-615.
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