The Rise and Promise of Molecular Nanotopology

Molecular nanotopology—a term we coined recently—is a rapidly developing field of research that is emerging out of the confluence of chemical topology with the mechanical bond.When perusing the increased research activities in this field,it is clear that a new discipline is ready to receive recognition in its own right.In this Mini-Review,we address the historical development of chemical topology and describe how the rational design and practical synthesis of molecular links and knots with mechanical bonds.

Synthesis of O6-Corona[3]arene[3]pyridazines and Their Molecular Recognition Property in Organic and Aqueous Media

O6-Corona[3]arene[3]pyridazines were synthesized from the one-pot macrocyclic condensation reaction of 3,6-dichlorotetrazine with 1,4-dihydroquinone derivatives followed by the inverse electron demand Diels-Alder reaction of the tetrazine rings with a cyclopentanone-derived enamine. Conversion of six ester groups within macrocycle into all sodium acetate moieties afforded a water soluble O6-corona[3]arene[3]pyridazine. The coronary macrocycle host formed complexes selectively with organic ammoniums and dinitrile guests in a 1 ： 1 stoichiometric ratio in organic solvents with association constants ranging from （2.96± 0.10）× 10^1 to （2.53±0.33）× 10^5 L·mol^-1. Water soluble O6-corona[3]arene[3]pyridazine was also able to complex strongly with organic ammoniums in water to give an association constant up to （2.67 ± 0.21） × 10^4 L·mol^-1. The pseudo-rotaxane and inclusion structures of the host-guest complexes were revealed by the X-ray crystallography.

Inherently Chiral and Symmetrical Heteroatom-Doped Zigzag-Type Hydrocarbon Belts

hydrocarbon belts due to their potential applications in carbon nanotechnology.By contrast,heteroatomembedded zigzag hydrocarbon belts as advanced design strategies with fascinating structures and desirable,unique properties have remained largely unexplored,and inherently chiral ones are unknown.Herein,we report the synthesis of a diversity of symmetric and highly enantiopure inherently chiral O-and N-doped zigzag-type hydrocarbon belts starting from strainless macrocycles based on fjord-stitching strategy.The readily available pertriflated resorcin[6]arene underwent partial hydrolyses and intramolecular S_(N)Ar reactions to form a calix[3](9H-xanthene)derivative and a prochiral half-belt selectively.Straightforward transformations of calix[3](9H-xanthene)into C_(3v)-symmetric molecular belts were achieved by closing the rest of the fjords with triple intramolecular S_(N)Ar reactions and Yamamoto homo coupling reactions,as well as palladiumcatalyzed intermolecular acridination reactions with primary amines.The prochiral half-belt underwent enantioselective desymmetrizative mono-acridination to afford an inherently chiral N,O_(4)-bridged pseudo-belt with an enantiomeric excess(ee)value of>99%under the catalysis of Pd(OAc)_(2)and(R)-Antphos.Ring closure reactions of the pseudo-belt produced diverse heteroatom-inlayed zigzag-type hydrocarbon belts of inherent chirality.Further,we showed the unique cavity structures of the belts and demonstrated interesting chiroptic properties of the inherently enantiopure chiral belts.This research opens the door for the exploration of novel and sophisticated symmetric and inherently chiral molecular nanobelt structures with outstanding physical and chemical properties,as well as potential applications.