Heteroatom-bridged molecular belts as containers

Abstract

Hoop-shaped or belt-like molecules have been fascinating not only due to their challenging synthesis, but also unique physical and chemical properties. The incorporation of heteroatoms (N, O, S, etc.) into these belts could alter both molecular structures and electronic properties which will lead to versatile applications, from advanced host-guest systems to functional materials. Despite numerous computational studies, the synthesis and characterization of heteroatom-bridged double-stranded molecular belts remains scarce. Here we report the synthesis, crystal structure, and host-guest chemistry of two novel heteroatombridged belt-like macrocycles composed of phenoxathiin. The bowl-shaped belt demonstrates a strong binding affinity (K a = 3.6 × 10 9 M-2) towards fullerene C 60 and forms a 2:1 capsulelike complex with the aid of C-H•••S hydrogen bonds. The column-like belt can bind the cyclic guest [2,2]paracyclophane to form a ring-in-ring complex. The modular synthesis, structural specificity, and diverse host-guest chemistry of cyclophenoxathiins markedly expands the known chemistry of molecular belts.

Conjugated Nanohoops Incorporating Donor, Acceptor, Hetero‐ or Polycyclic Aromatics

“…Changing to an angular annelation pattern of the sixmembered rings or incorporating ring sizes other than six, on the other hand, successfully led to the synthesis of several conjugated nanobelts to date, as detailed below. [133,134] Heterocyclacenes [135,136] and nanobelts incorporating pentalene units [137] have also been identified as attractive synthetic targets.…”

Oxygen‐ and Nitrogen‐Embedded Zigzag Hydrocarbon Belts

“…For example, pyridine‐ and pyrazine‐containing belt[ n ]arenes were computed previously [23–25] but never synthesized. Very recently, the syntheses of a box‐like pyrazine‐ and 6 H ‐benzo[ c ]chromene‐containing chiral belt molecules have been reported by Miao [26] and Tanaka, [27] respectively, while Zhu disclosed the synthesis and host–guest properties of phenoxathiine‐bearing molecular belts [28] …”

Synthesis of Donor‐Acceptor π‐Conjugated Macrocycles by Post‐Functionalization†

“…Organic macrocyclic compounds as one of the most widely utilized host molecules for molecular recognition have attracted great attention. [ 1‐3 ] Various types of macrocycles have been studied to encapsulate different guest molecules by tuning the units of main frameworks and the size of cavities, which is applied in the fields of adsorption, [ 4‐5 ] separation, [ 6‐7 ] sensing, [ 8‐11 ] drug delivery, [ 12‐13 ] and molecular machines. [ 14‐15 ] The macrocyclic molecules can effectively arrange multiple recognition sites together, reducing the negative entropy effect from the orderly arrangement of recognition sites, thereby achieving the purpose of effectively identifying guest molecules or ions.…”