Crystals of molecular rings, cages and rotors [1] display various kinds of packing peculiarities such as pseudosymmetry, intra- and intermolecular inclusion, porosity, etc. that result not only from the specific shape of these molecules but also from the deliberate presence in their skeleton of chiral and sterically demanding fragments. We will demonstrate that chiral, triangular-shape, methylene bridged amine (called trianglamine) is capable to include in its inner cavity linear or branched alcohol molecules belonging to the homologous series from ethanol to octanol. Solvent controlled grow of porous apohost crystals, their stability and inclusion ability will be discussed together with modifications of the host framework that accompany the uptake and loss of solvent molecules. Covalent cage compounds will be exemplified by the cuboctahedral-shape imine molecule containing 24 imine bonds. The molecule possesses unprecedentedly large inner cavity and displays both intra- and intermolecular inclusion in crystals. The family of rotor molecules will be represented by compounds that contain triphenylacetamide fragments attached to the chiral aliphatic backbone. The large triphenylmethyl rotors prevent the molecules from packing closely and are therefore a source of microporosity and intermolecular inclusion in crystals. Modifications of the host framework stimulated by included solvent molecules will be illustrated. A noteworthy observation from the crystal engineering point of view is a particular role of triphenylmethyl group as supramolecular protector responsible for the total absence of the classical amide…amide hydrogen bonds and rare involvement of the NH amide group in intermolecular interactions.
The work is partially sponsored by the Polish National Science Centre, grant MAESTRO 2012/06/A/ST5/00230.
[1] Samples for X-ray analysis have been obtained from a group led by prof. Jacek Gawroński, Faculty of Chemistry, Adam Mickiewicz University, Poznań, Poland