1. Spontaneous resolution of a Δ/Λ-chiral-at-metal pseudo-tetrahedral Schiff-base zinc complex to a racemic conglomerate with C–H…O organized 41- and 43-helices.
- Author
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Enamullah, Mohammed, Vasylyeva, Vera, Quddus, Mohammad Abdul, Islam, Mohammad Khairul, Höfert, Simon-Patrick, and Janiak, Christoph
- Subjects
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CHIRALITY , *SCHIFF bases , *ISOMORPHOUS structures - Abstract
The Schiff-base ligand N-2-(pyridyl)salicylaldimine (HL) reacts with zinc(ii) acetate or nitrate to obtain the enantiomorphous chiral-at-metal compound Δ/Λ-bis[N-2-(pyridyl)salicylaldiminato-κ2N,O]zinc(ii), [Zn(L)2] (1), which crystallizes as a racemic conglomerate via spontaneous resolution. Two deprotonated N,O-chelate ligands form a pseudo-tetrahedral N2O2-coordination sphere with a Δ/Λ-configured zinc atom. The Δ- and Λ-configured molecular complexes in 1 assemble in P (right)- and M (left)-handed 41- and 43-helical chains in the chiral space groups P41212 and P43212, respectively, through weak C–H…O hydrogen bonding between neighbouring molecules along the chain axis. Only molecules of the same Δ- or Λ-configuration combine into a helical chain and only chains of the same P- or M-handedness combine to form homochiral crystals. According to the analyses of intermolecular interactions with the Hirshfeld surface, the supramolecular packing features C–H…O bonding as the most apparent significant contribution. This is a rare example of solely weak C–H…O hydrogen bonding interaction leading to spontaneous resolution to a racemic conglomerate. This case also supports the notion of less repulsive packing interactions between homochiral molecules because of spin polarization. Optimized structures and excited state properties by DFT/TD-DFT calculations are comparable to experimental results. [ABSTRACT FROM AUTHOR]
- Published
- 2018
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