engleski

Supramolecular solid state synthesis: Isostructurality and halogen-bonded cocrystals

Halogen bonds are similar to hydrogen bonds both in terms of length (typically 2.7-3.0 A) and directionality, involving an electron-deficient halogen atom and an electron donor (e.g. N or O). For this reason, halogen bonding provides an additional opportunity for the crystal engineer to design functional solid-state architectures [1]. In comparison to hydrogen bonds, which usually involve a modest number of acceptor atoms (typically O or N), the set of halogen-bond acceptors is larger, encompassing, among others, O, N, S, and Se. We describe a mechanism for the mechanochemical synthesis of halogen-bonded cocrystals [2] and demonstrate the supramolecular and structural equivalence of halogen-bond donors (e.g. I and Br) and acceptors (e.g. O, NH and S). We synthesised via grinding seven isostructural halogen-bonded cocrystals, involving six different molecules: 1, 4-dibromo- and 1, 4-diiodotetrafluorobenzene as donors and thiomorpholine, thioxane, morpholine, and piperazine as acceptors. The formation of isostructural cocrystals indicates how cocrystallization may be used to overcome shape and functional group dissimilarities that affect molecular arrangement in the solid state [3]. Also, we demonstrate the potential and the possibilities of a cocrystal-based strategy to systematically construct isostructural materials with controllable properties [4, 5]. This strategy utilises cocrystal formation to combine structurally equivalent functionalities in the solid. [1] P. Metrangolo, H. Neukirch, T. Pilati, G. Resnati, Acc. Chem. Res. 38 (2005) 386-395. [2] D. Cinčić, T. Friščić, W. Jones, J. Am. Chem. Soc. 130 (2008) 7524– 7525. [3] D. Cinčić, T. Friščić, W. Jones, Chem. Eur. J. 14 (2008) 747-753. [4] D. Cinčić, T. Friščić, W. Jones, New. J. Chem. 32 (2008) DOI: 10.1039/b805816d. [5] D. Cinčić, T. Friščić, W. Jones, Chem. Mater. (2008) DOI: 10.1021/cm800923r.

Halogen bond; mechanochemical synthesis; cocrystals; isostructural materials

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