Chiral crystals formed from achiral molecules have recently received a great deal of attention due to their attractive structural properties and prospective applications in chemistry [1]. For instance, such compounds can be used as ligands in enantioselective reactions or models for investigation of molecular recognition [2]. Understanding the details, which govern the process of formation of chiral crystals, chiral induction, and th mechanism of spontaneous resolution of racemic compounds, is one of the most general questions touching the problem of the origin of life [3].

As a part of our interest in the problem of formation of crystals with planar chirality [4] we presented the structural studies for two diazacoronands 1 and 2 [5] in the solid phase. It was apparent, that crystals of 1 and 2 have to be considered as a two-component system consisting of an organic unit and a water molecule in 1:1 ratio.

Both components play an important role in the crystal structure. The strong (O-H...O, N-H...O) and weak (C-H...O) intermolecular hydrogen bonds are responsible for phase organization and, in consequence, formation of chiral or achiral crystals. The alignment of the water molecule with respect to the macrocycle is different for samples 1 and 2, so the water molecule can be an important achiral cofactor responsible for chiral crystallization. It is worthy to note, that process of removal of water from the crystal lattice of 1 is reversible.

In this work, we report the results of the investigation of the structure and molecular dynamics of two benzodiazacoronads 1 nas 2 in the liquid phase. The major aim of our project is to understand the origin of distinction between these compounds and answer the question what is the role of water molecules in the process of formation of chiral crystals during the preorganization step? For this purpose, NMR spectroscopy and molecular dynamics calculations appear to be a powerful methods. Both, the results of relaxation parameters (T₁, T₂ and NOE) measurements and MD Calculations, will be presented and discussed.

[1] Kondepudi, D. K.; Kaufman, R. J.; Singht, N. Science 1990, 250
[2] a) Dahmen, S.; Brase, S. J. Am. Chem. Soc. 2002, 124, 5940. b) Gibson, S. E.; Knight, J. D. Org. Biomol. Chem. 2003, 1, 1256. c) Brase, S.; Dahmen, S.; Hofener, S.; Lauterwasser, F.; Kreis, M.; Ziegert, R. E., Synlett 2004, 2647
[3] Addali, L.; Lahav, M. In Origins of Optical Activity in Nature; Walker, D. C., Ed.; Elsevier: Amsterdam, 1979.
[4] a) Kalisiak, J.; Jurczak, J. Synlett 2004, 9, 1616-1618. b) Piatek, P.; Kalisiak, J.; Jurczak, J. Tetrahedron Lett. 2004, 45, 3309-3312. c) Kalisiak, J.; Skowronek, P.; Gawronski, J.; Jurczak, J. J. Eur. Chem. 2006, 12, 4397-4406. d) Kalisiak, J.; Jurczak, J. Cryst. Growth Des. 2006, 6, 22-24.
[5] Pacholczyk, J.; Kalisiak, J.; Jurczak, J.; Potrzebowski M.J. J. Phys. Chem. B 2007, 111, 2790-2799.

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1. Anion Recognition by Artificial Polyamide Receptors
2. Molecular Recognition of Nitro- and Cyanoarenes by Podand Diazacoronands