Supramolecular [6]Chochin and “Big Mac” Made from Chiral Piedfort Assemblies

Abstract

Facile chemical synthesis of the natural chiral-pool-derived host 1 and its subsequent crystallization ("supramolecular synthesis") from different solvents yielded crystalline assemblies. Crystal structure determinations of five of the so formed solvent-inclusion compounds (1 a-1 e) reveal hexagonal symmetries in four cases. The structural characteristics of these chiral host-guest ensembles with varying stoichiometries can be best described as assemblies formed through intra-pair hydrogen bridges of host molecules into Piedfort pairs of differing complexity. Hitherto undescribed, these Piedfort pairs also form even larger regular assemblies that we designate "Big Mac"-like shapes. In the only nonhexagonal case, six independent host molecules form a huge supramolecular analogue of [6]benzocyclophane, also known as [6]chochin, extending this giant supermolecule through intermolecular hydrogen bonds into macroscopic (mm-size) dimensions. As all these crystals are inherently chiral, and new model systems for solid-state applications can be envisaged.

Halogen bonding and isostructurality in 2,4,6‐tris(2‐halophenoxy)‐1,3,5‐triazines

“…The Piedfort Unit dimer (PU) [30][31][32] is stabilized by π ••• π stacking (3.34Å) and C H ••• O and C H ••• N interactions from the ortho-phenyl donor to the phenoxytriazine group of the next layer. The ortho-halogen on both sides prevents continuous stacks along the PU axis, and so the molecules align with slight offset.…”

Evaluating the electron density model by applying an imaginary modification

“…Czugler et al (Czugler et al 2003). Two data sets at the resolution of 1.0 and 2.5 Å, respectively, are generated.…”

A Quest towards Eccentric Piedfort Pairs

“…Hence, our goal is to design and synthesize 1,3,5‐triazine molecules that can form PPs with sufficient area in between monomers (two disks of PP) to accommodate a small molecule (Figure ) . However, known PPs possess distances (D Cg⋅⋅⋅Cg ) between two six membered rings in the range of 3 to 4 Å due to π⋅⋅⋅π stackings whereas to park a small molecule in between the two disks of PP at least ∼8 Å distance (D Cg⋅⋅⋅Cg ) might be required ,,,,. In order to achieve ∼8 Å of D Cg⋅⋅⋅Cg between disks of PP, we have decided to play with the substituents on the periphery of 1,3,5‐triazine rings.…”