Organized by the Institute of Experimental Physics, University of Bialystok and the Institute of Atomic Energy, Swierk under the auspices of the European Crystallographic Association; Committee of Crystallography, the Polish Academy of Sciences; and the Polish Neutron Scattering Society The School is financially supported in part by the International Union of Crystallography; the European Crystallographic Association; the European Office of Aerospace Research & Development; the Ministry of Science and Information Society Technologies; the Warsaw University of Technology; and the University of Bialystok.
		Halogen bonding: An important non-covalent interaction in self-assembly of matter Ashwani Vij, USA Topics Hydrogen bonding to an electronegative heteroatom is an interesting bonding mode: an area which interests chemists, biochemists and biologists. Because of such interactions, various biological processes can be understood, including the structure and assembly of DNA, etc. However, a new non-covalent bonding aspect is becoming increasingly important in the self-assembly of matter. This type of interaction can result from the entire family of halogens; i.e., F, Cl, Br and I. A wide variety of structural forms varying from polynitrogen and high nitrogen species are stabilized by interaction with halogens. In the s-triazene ring system, these can form hexagonal or half-hexagonal networks; whereas in carbaphosphazene ring systems, a stacked honey-comb pattern results via N•••Cl interactions. A more recent report by Resnati et al. on the head-to-tail coupling between fluorocarbon iodides and amines in spontaneous resolution in halogen bonded supramolecular architecture will be discussed. The orientations and helices of long chain fluorocarbon atoms will be highlighted. Time permitting, some experimental difficulties in obtaining good structural data for "small" molecules with about >250 atoms and modeling strategies will be outlined. A tutorial will be conducted for students during this workshop, which will outline crystal growth, disorder, methods for extrapolating geometries resulting from such disorders and issues related to dealing with twinning in crystal structures. Few examples dealing with such problems will be demonstrated using published datasets. Some of such disorders are: NOF2+ cation, scrambling of azide and chlorides in antimony and platinum structures, and some examples of twinned materials.