Supramolecular Self-Sorting Networks using Hydrogen-Bonding Motifs

A current objective in supramolecular chemistry is to mimic the transitions between complex self-sorted systems that represent a hallmark of regulatory function in nature. In this work, a self-sorting network, comprising linear hydrogen motifs, was created. Selecting six hydrogen-bonding motifs capable of both high-fidelity and promiscuous molecular recognition gave rise to a complex self-sorting system, which included motifs capable of both narcissistic and social self-sorting. Examination of the interactions between individual components, experimentally and computationally, provided a rationale for the product distribution during each phase of a cascade. This reasoning holds through up to five sequential additions of six building blocks, resulting in the construction of a biomimetic network in which the presence or absence of different components provides multiple unique pathways to distinct self-sorted configurations.     

Self‐Sorting of Two Hydrocarbon Receptors with One Carbonaceous Ligand

Non‐directional van der Waals forces in biological and synthetic supramolecular systems play important roles in molecular assembly, particularly in determining the distances of the interacting species. The van der Waals forces are normally used in combination with other directional forces and are considered to play a secondary role in achieving specificity and fidelity in molecular recognition. Using an ideal supramolecular system consisting solely of hydrogen and carbon atoms, we found that the van der Waals interactions enable the high‐fidelity sorting of two homomeric receptors during ligand‐induced assembly. The self‐sorting occurred in a narcissistic manner by repulsion of a competing diastereoisomeric receptor from the assembly. The structure–sorting relationship study with enantiomers further revealed the dominant role of the van der Waals forces in shape recognition for high‐fidelity self‐sorting.     

基于异源自分类串联反应集成策略构筑不对称的1,4-二氢吡啶衍生物

假设不同结构的底物可以同时参与自分类的串联反应,而且各自生成的合适官能化的分子能够进一步发生汇聚反应,将更为有效地制备复杂的产物。在此基础上,我们建立了一个简单的反应模型来验证该策略的可行性。例如,在醋酸铵和间硝基苯甲醛的存在下,两种1,3-二羰基化合物可以经过两个并存的串联反应路径分别生成烯胺和烯酮中间体,二者随后汇聚选择性生成不对称的1,4-二氢吡啶.通过核磁直接检测反应液进一步证实了该反应的高度选择性,即不同底物发生串联反应的高度自分类且汇聚的特性.我们希望该结果能启发化学家通过更为有效的异源自分类串联反应集成策略实现由简单底物来高效制备复杂的分子.     

Influencing the Self-Sorting Behavior of [2.2]Paracyclophane-Based Ligands by Introducing Isostructural Binding Motifs

Two isostructural ligands with either nitrile ( L^nit ) or isonitrile ( L^iso ) moieties directly connected to a [2.2]paracyclophane backbone with pseudo-meta substitution pattern have been synthesized. The ligand itself ( L^nit ) or its precursors ( L^iso ) were resolved by HPLC on a chiral stationary phase and the absolute configuration of the isolated enantiomers was assigned by XRD analysis and/or by comparison of quantum-chemical simulated and experimental electronic circular dichroism (ECD) spectra. Surprisingly, the resulting metallosupramolecular aggregates formed in solution upon coordination of [(dppp)Pd(OTf)₂] differ in their composition: whereas L^nit forms dinuclear complexes, L^iso exclusively forms trinuclear ones. Furthermore, they also differ in their chiral self-sorting behavior as (rac)- L^iso undergoes exclusive social self-sorting leading to a heterochiral assembly, whereas (rac)- L^iso shows a twofold preference for the formation of homochiral complexes in a narcissistic self-sorting manner as proven by ESI mass spectrometry and NMR spectroscopy. Interestingly, upon crystallization, these discrete aggregates undergo structural transformation to coordination polymers, as evidenced by single-crystal X-ray diffraction.     

Regulating Higher‐Order Organization through the Synergy of Two Self‐Sorted Assemblies

The extracellular matrix (ECM) is the natural fibrous scaffold that regulates cell behavior in a hierarchical manner. By mimicking the dynamic and reciprocal interactions between ECM and cells, higher‐order molecular self‐assembly (SA), mediated through the dynamic growth of scaffold‐like nanostructures assembled by different molecular components, was developed. Designed and synthesized were two self‐sorted coumarin‐based gelators, a peptide molecule and a benzoate molecule, which self‐assemble into nanofibers and nanobelts, respectively, with different dynamic profiles. Upon the dynamic growth of the fibrous scaffold assembled from peptide gelators, nanobelts assembled from benzoate gelators transform into a layer‐by‐layer nanosheet, reaching ninefold increase in height. By using light and an enzyme, the spatial–temporal growth of the scaffold can be modified, leading to in situ height regulation of the higher‐order architecture.     

Multicomponent Self-Assembly of PdII/PtII Interlocked Molecular Cages: Cage-to-Cage Conversion and Self-Sorting in Aqueous Medium

Coordination-driven self-assembly is an efficient approach for constructing complicated molecules with the aid of reversible bond formation. However, constructing topologically complicated interlocked systems and their formation studies remain challenging tasks. The formation of two water-soluble hexanuclear interlocked cages by multicomponent self-assembly of a flexible triimidazole donor ( L1 ) and a rigid tripyridyl donor ( L2 ) based on a triazine core in combination with 90° cis-blocked Pd^II and Pt^II acceptors is reported here. Formation of interlocked systems having a composition of M₆( L1 )₂( L2 )₂ (M=Pd or Pt) becomes feasible through cavity-induced self-recognition of two similar units having a composition of M₃( L1 )( L2 ). Self-sorting of two independently prepared cages of [M₃( L1 )₂] and [M₆( L2 )₄] in aqueous medium leads to the formation of interlocked systems, and their formation was monitored by time-dependent ¹H NMR spectroscopy. Self-recognition of L1 by [M₆( L2 )₄] or L2 by [M₃( L1 )₂] leads to the formation of interlocked systems, as confirmed from ¹H NMR spectroscopic titrations of L1 with cages {M₆( L2 )₄} and L2 with {M₃( L1 )₂}, respectively. Both the interlocked cages of Pd and Pt are highly stable, and formation of either system is equally probable as observed from the treatments of Pd₃( L1 )₂ with Pt₆( L2 )₄ or Pt₃( L1 )₂ with Pd₆( L2 )₄, which lead to the formation of two different self-assembled homometallic interlocked cages [Pt₆( L1 )₂( L2 )₂+Pd₆( L1 )₂( L2 )₂] instead of forming any other heterometallic assemblies. Formation of interlocked cages is dependent on the steric bulk of the diamine ligand bound to the metal acceptors. A N-alkyl-substituted blocking amine prefers the non-interlocked cage instead of the interlocked analogue.     

Controlled Orthogonal Self‐Assembly of Heterometal‐Decorated Coordination Cages

Multiple orthogonal coordinative interactions were utilized to construct heterometal‐decorated tetrahedral cages from in situ formed trinuclear Zr^IV clusters through the combination with other metal ions such as Cu^II or Pd^II. Through effective use of the hard/soft acid/base principle, the orthogonal self‐assembly process of Zr‐bpydc‐CuCl₂ (H₂bpydc=2,2‐bipyridine‐5,5‐dicarboxylic acid) can be finely controlled using three strategies: post‐synthetic metallization, a stepwise metalloligand approach, or a one‐pot reaction.     

Polymerization,Stimuli-induced Depolymerization,and Precipitation-driven Macrocyclization in a Nitroaldol Reaction System**

Dynamic covalent polymers of different topology have been synthesized from an aromatic dialdehyde and α,ω-dinitroalkanes via the nitroaldol reaction. All dinitroalkanes yielded dynamers with the dialdehyde, where the length of the dinitroalkane chain played a vital role in determining the structure of the final products. For longer dinitroalkanes, linear dynamers were produced, where the degree of polymerization reached a plateau at higher feed concentrations. In the reactions involving 1,4-dinitrobutane and 1,5-dinitropentane, specific macrocycles were formed through depolymerization of the linear chains, further driven by precipitation. At lower temperature, the same systemic self-sorting effect was also observed for the 1,6-dinitrohexane-based dynamers. Moreover, the dynamers showed a clear adaptive behavior, displaying depolymerization and rearrangement of the dynamer chains in response to alternative building blocks as external stimuli.     

Static and Dynamic Nanosheets from Selective Assembly of Geometric Macrocycle Isomers

In contrast to the significant advances that have been made in the construction of two‐dimensional (2D) nanostructures, the rational modification from static to dynamic 2D sheets remains a great challenge. Static and dynamic sheets formed from selective self‐assembly of geometric macrocycle isomers based on anthracene units are presented. The self‐assembly of the cis isomer generates static planar sheets, whereas the trans isomer forms dynamic rolled sheets which are reversibly unrolled upon stimulation by a thermal signal. Furthermore, the mixed solution of the two isomers exhibits self‐sorting behavior, generating the coexistence of the two independent self‐assembled structures, the planar sheets and the folded scrolls. The self‐sorted supramolecular objects with considerable shape and size differences are able to be readily separated, one isomer from the other.