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Issue 1, 2011
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Unravelling the fine structure of stacked bipyridine diamine-derived C3-discotics as determined by X-ray diffraction, quantum-chemical calculations, Fast-MAS NMR and CD spectroscopy

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Abstract

An in depth investigation of the fine structure adopted by the helical stacks of C3-discotics 1 incorporating three 3,3′-diamino-2,2′-bipyridine units is described. In the bulk the molecules display liquid crystalline behaviour in a temperature window of >300 K and an ordered rectangular columnar mesophase (Colro) with an inter-disc distance of 3.4 Å is assigned. X-Ray diffraction on aligned samples has also revealed a helical superstructure in the liquid crystalline state, and a rotation angle of 13–16° between consecutive discs. The proposed superstructure in the bulk phase has been further substantiated by a combination of quantum-chemical calculations and solid-state NMR spectroscopy. Dilute solution NMR spectroscopy and elaborate CD spectroscopy on aggregated samples have revealed an isodesmic growth pattern of the C3-discotics. From the combined results it has become evident that the fine tuning interaction responsible for the highly ordered helical architectures is not weak intermolecular hydrogen bonding, but rather rigidification, due to propeller formation after preorganisation by π–π interactions. Although all the techniques used underpin the structural features proposed, none of them individually is able to point to a unique structure. However, together the techniques give very strong evidence for a confined ship-screw arrangement in which all amidic carbonyl oxygens point in one direction.

Graphical abstract: Unravelling the fine structure of stacked bipyridine diamine-derived C3-discotics as determined by X-ray diffraction, quantum-chemical calculations, Fast-MAS NMR and CD spectroscopy

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Publication details

The article was received on 05 May 2010, accepted on 03 Aug 2010 and first published on 09 Sep 2010


Article type: Edge Article
DOI: 10.1039/C0SC00292E
Citation: Chem. Sci., 2011,2, 69-76
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    Unravelling the fine structure of stacked bipyridine diamine-derived C3-discotics as determined by X-ray diffraction, quantum-chemical calculations, Fast-MAS NMR and CD spectroscopy

    T. Metzroth, A. Hoffmann, R. Martín-Rapún, M. M. J. Smulders, K. Pieterse, A. R. A. Palmans, J. A. J. M. Vekemans, E. W. Meijer, H. W. Spiess and J. Gauss, Chem. Sci., 2011, 2, 69
    DOI: 10.1039/C0SC00292E

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