title: A helical structure with Z' = 10.
abstract: The structure of N''-cyano-N,N-diisopropylguanidine, a push-pull nitrile that includes the H(2)N-C=N-CN fragment, has been determined. Although the number of molecules in the asymmetric unit is exceptionally high (Z' = 10), there were no special crystallographic difficulties associated with data collection, structure solution or structure refinement because the individual molecules are small (12 non-H atoms) and because there is no important crystallographic pseudosymmetry. A complete set of N-H...N bonds is formed. Pairs of molecules form dimers, which associate to form ribbons that twist into a helix having five dimers per turn. The helices lie parallel to [101] and fit together with close contacts in three different directions perpendicular to that axis. The problems with optimizing so many different intermolecular contacts lead to a loosely packed structure.
authors.affiliation: Department of Chemistry, University of Kentucky, Lexington, KY 40506-0055, USA.
authors.forename: Xiang
authors.initials: X
authors.lastname: Hao
authors.forename: Jing
authors.initials: J
authors.lastname: Chen
authors.forename: Arthur
authors.initials: A
authors.lastname: Cammers
authors.forename: Sean
authors.initials: S
authors.lastname: Parkin
authors.forename: Carolyn Pratt
authors.initials: CP
authors.lastname: Brock