Jiu-Sheng Li

[2]Pseudorotaxanes and [2]catenanes constructed by oxacalixcrowns/viologen molecular recognition motifs.

Oxacalix[2]arene[2]pyrazine and functional polyether derived oxacalixcrown-6, -7, and -8 were synthesized, and their host-guest complexation with paraquat to form [2]pseudorotaxanes was studied. The [2]pseudorotaxanes were then successfully used in the construction of two oxacalixcrown-tetracationic cyclophane [CBPQT(4+)] based [2]catenanes.

Negative Cooperativity in the Binding of Imidazolium and Viologen Ions to a Pillar[5]arene-Crown Ether Fused Host.

A pillar[5]arene-crown ether fused bicyclic host 1 was found to be able to recognize an imidazolium ion G1 by its pillar[5]arene subunit and a viologen ion G2 by its crown ether receptor discriminatively. The simultaneous binding of G1 and G2 by 1 resulted in the formation of a three-component host-guest complex G1⊂1⊃G2. Negative heterotropic cooperative effects were displayed by G1 and G2 in their binding to 1 and were investigated by stepwise bindings of G1 and G2 to 1.

A1/A2-Diamino-Substituted Pillar[5]arene-Based Acid–Base-Responsive Host–Guest System

An acid-base-responsive supramolecular host-guest system based on a planarly chiral A1/A2-diamino-substituted pillar[5]arene (1)/imidazolium ion recognition motif was created. The pillar[4]arene[1]diaminobenzene 1 can bring an electron-deficient imidazolium cation into its cylindrically shaped cavity under neutral or basic conditions and release it under acidic conditions.

Multicavity macrocyclic hosts

Multicavity macrocyclic hosts are host molecules comprising more than one macrocyclic guest binding components connected through multipoint linkages. Macrocycles, such as crown ethers, pillar[n]arenes, calix[n]arenes, and calix[4]pyrroles, have been used to fabricate multicavity hosts, either homotopic or heterotopic. This review is mainly focused on the molecular structures and host-guest behaviors of multicavity macrocyclic host molecules and their applications in the assembly of sophisticated supramolecular architectures.

Selectivity and Cooperativity in the Binding of Multiple Guests to a Pillar[5]arene–Crown Ether Fused Tricyclic Host

A novel tricylic host molecule 1 that consists of two pillar[5]arene units and a crown ether ring was found to selectively bind two kinds of guest molecules with different shapes, sizes, and electronic constitutions, namely 1,4-dicyanobutane G1 and paraquat G2, with its two macrocyclic subunits, to form a four-component complex 2G1⊂1⊃G2. An (1)H NMR study of stepwise bindings of G1 and G2 to host 1 in CDCl3/DMSO-d6 revealed that the strength of the association between complex 2G1⊂1 and guest G2 was only one-fourth of that between free 1 and G2, demonstrating a negative heterotropic cooperativity of G1 in the binding of G2 to host 1.

Engineering a pillar[5]arene-based supramolecular organic framework by a co-crystallization method

A supramolecular organic framework, P5-bpy-SOF, made of perhydroxyl-pillar[5]arene (P5) and 4,4-bipyridine (bpy) and prepared by using a co-crystallization approach, showed a different hydrogen bonding pattern and a 3D molecular arrangement from that in the perhydroxyl-pillar[5]arene-based supramolecular organic framework (P5-SOF). TGA analyses, powder X-ray diffraction and gas absorption study confirmed P5-bpy-SOFs structural stability, permanent porosity, and, especially, selectivity of absorption of CO2 over N2.

Tetranitro-oxacalix[4]crown-Based Host–Guest Recognition Motif and a Related [2]Rotaxane-Based Molecular Switch

Different from so far reported oxacalix[4]crown-based host-guest motifs in which oxacalix[4]crowns act only as hydrogen bond acceptors, a [2]pseudorotaxane-type tetranitro-oxacalix[4]crown/urea host-guest recognition motif was developed in which tetranitro-oxacalix[4]crown played a role as both a hydrogen bond donor and an acceptor to stabilize the resulting supramolecular complex. Furthermore, on the basis of a [2]pseudorotaxane complex formed from a tetranitro-oxacalix[4]crown and an axle containing a secondary ammonium ion and a urea group, a [2]rotaxane-based molecular switch was created, in which the oxacalix[4]crown wheel was able to reversibly translocate between the secondary ammonium binding site and the urea binding site of the axle under acid-base stimulation.

A Shape-Persistent Cryptand for Capturing Polycyclic Aromatic Hydrocarbons

A shape-persistent cryptand 1, containing two face-to-face oriented electron-deficient 2,4,6-triphenyl-1,3,5-triazine units separated by approximately 7 Å, and bridged by two rigid 1,8-naphthyridine linkers and a pentaethylene oxide loop, is created for capturing polycyclic aromatic hydrocarbons. Cryptand 1 formed 1:1 complexes with PAH guest molecules, such as phenanthrene (6), anthracene (7), pyrene (8), triphenylene (9), and tetraphene (10). The single-crystal structure of complex 6⊂1 revealed that 6 was included in the cavity of 1 via face-to-face π···π stacking interactions. Soaking crystalline 1 in a toluene solution of anthracene resulted in anthracene from the toluene solution being picked up by the crystalline solid of 1.