Abstract
The title host compound, C62H84N4O4, designed to self-assemble to form a new type of extended core Piedfort unit reminiscent of an eight-legged spider host, forms a number of crystalline inclusion compounds favouring oxygen-containing guest mol-ecules. We have established the presence of this unit in the unsolvated mol-ecular crystal at 100 K, which is monoclinic, space group P21/n, with Z = 8. The new Piedfort unit is chiral and its core structure closely approximates to D 2 symmetry, with both enanti-omers present in the crystal. Rather than being superposed with a staggered arrangement of nitro-gen atoms, the rings are rotated by an angle of approximately 45° with respect to each other, and the shortest contact between them is 3.181 (2) Å. The compound's significant inclusion properties may be taken to suggest the participation of an extended Piedfort unit in the microcrystalline adducts formed. The presence of such a dimeric host unit in the clathrates has, however, not yet been established because of the current lack of suitable single crystals for X-ray analysis.
Highlights
Was anticipated, that a judicious choice of side chain would be critical
It is likely that the energy does not vary greatly among all these forms. This view is supported by the observation of situations significantly rotated away from a staggered arrangement in existing Piedfort units formed by 1,3,5-triazenes such as 1b and 1c, the latter unit, among others, has almost perfectly eclipsed nitrogen atoms (Henderson et al, 1995; Thalladi et al, 1998)
The introduction of a single meta-methyl group to the side-chain rings of 2a, to give 2b promoted no host properties and likewise 2c, which shares a common side chain with host 1a, showed no evidence of inclusion behaviour
Summary
Following its introduction in 1990 (Jessiman et al, 1990) the Piedfort concept is widely recognised to correspond to an effective supramolecular synthon (Desiraju, 1995; Bombicz et al, 2015 and references therein; Xu et al, 2016; Mooibroek & Gamez, 2007; Saha et al, 2005; Thalladi et al, 1998) We employed this idea to construct a composite hexahost molecule (MacNicol, 1984). It is likely that the energy does not vary greatly (for link Z = O) among all these forms This view is supported by the observation of situations significantly rotated away from a staggered arrangement in existing Piedfort units formed by 1,3,5-triazenes such as 1b and 1c, the latter unit, among others, has almost perfectly eclipsed nitrogen atoms (Henderson et al, 1995; Thalladi et al, 1998).
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