Selective synthesis of heteroleptic Pd2A3B-cages:modulating size-preference of supramolecular hosts via endo-functionalization

The size complementarity between a host and a guest is a critical prerequisite for selective molecular recognition.Numerous artificial host systems have been designed to achieve size-selective recognition and chemical transformations.However,the inherent challenge lies in the fixed selectivity governed by a size-exclusion mechanism dictated by the host's structure.Modulating the selectivity necessitates structural modifications of hosts.Examples of host systems with modifiable sizeselectivity are rare.In this study,we present an approach to modulating guest-selectivity via endo-functionalization of supramolecular cavities.Heteroleptic Pd2A3B-cages are constructed with a Pd2A3precursor or directly from palladium ions and relevant ligands.Furthermore,the simultaneous and selective formation of multiple hetero-cages was achieved by simply mixing PdIIand the free ligands in a one-pot reaction.The fidelity of the assembly process relies on cooperative steric control at the periphery and within the cavity of the hetero-cages,respectively.The central steric group also functions as the endohedral moiety.Variations of the endohedral groups facilitate facile and modular derivatization of the microenvironment within the cages,enabling the fine-tuning of guest binding affinities as evidenced by titration experiments.This strategy offers a new solution for the development of customized host structures.

Amide naphthotubes:Biomimetic macrocycles for selective molecular recognition

Selective molecular recognition in water is routine for bioreceptors,but remains challenging for synthetic hosts.This is principally because noncovalent interactions are usually less efficient in aqueous environments.By mimicking the cavity feature of bioreceptors,Prof.Wei Jiang proposed and clarified the concept of“endo-functionalized cavity”.Through situating polar binding sites into a deep hydrophobic cavity,we designed and synthesized several macrocyclic hosts,among which amide naphthotubes are the most representative.The hosts can selectively recognize various polar molecules including organic micropollutants,drug molecules,and chiral molecules in water by employing the hydrophobic effect and shielded hydrogen bonding.In addition,these biomimetic hosts have been applied in spectroscopic analysis,adsorptive separation and self-assembly.In this review,we provide an overview of recent advances on amide naphthotubes with special emphasis on the efforts of Jiang's group.We are convinced that these biomimetic macrocycles will make further contributions to supramolecular chemistry and beyond.

Selective recognition of methyl viologen by an endo-functionalized naphthobox

Highly selective binding of structurally similar substrates is common for biomolecular recognition,but is often challenging to realize in synthetic hosts.Herein,we report highly selective binding of methyl viologen over other analogues by an endo-functionalized naphthobox.X-ray single crystal structure and Density Functional Theory(DFT)calculations revealed that the endo-functionalized groups in the cavity of the naphthobox is important for the high binding selectivity through the formation of multiple C-H…N,C-H…π,andπ…πinteractions with methyl viologen.