<i>ortho</i>-Functionalization of Pillar[5]arene: An Approach to Mono-<i>ortho</i>-Alkyl/Aryl-Substituted A1/A2-Dihydroxypillar[5]arene

Despite the fact that the rim and lateral functionalizations of pillar­[n]­arenes have been well explored, ortho-functionalization has rarely been realized. In this work, we report a facile method of introducing a single functionality ortho to the hydroxyl group in A1/A2-dihydroxypillar[5]­arene via a Grignard addition to pillar[4]­arene[1]­quinone followed by a dienone–phenol rearrangement. The described ortho-alkylation/arylation method allowed formation of various mono ortho-alkyl/aryl-substituted A1/A2-dihydroxypillar[5]­arenes previously difficult to obtain

Total Synthesis of (±)-Minfiensine via a Formal [3+2] Cycloaddition

(±)-Minfiensine (<b>1</b>) was synthesized in 10 steps in 26% overall yield with the 1,2,3,4-tetrahydro-9a,4a-iminoethanocarbazole core constructed through a [3+2] cycloaddition reaction between indole and an azaoxyallylic cation

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

Hydroxy-Rich Pillar[5]arene-Based Nanoporous Aromatic Frameworks (PAFs) for Efficient CO₂ Uptake under Ambient Conditions

In this letter, we report our fabrication of a three-dimensional hydroxy-rich pillar[5]arene-extended nanoporous aromatic framework PAF-P5-OH for CO2 uptake. CO2 adsorption study demonstrated that PAF-P5-OH exhibited excellent CO2 uptake capacity (88 cm3 g–1 at 273 K and 76 cm3 g–1 at 298 K) under atmospheric pressure, which could be attributed to the favored dipole interactions between the adsorbed CO2 molecules and the hydroxy groups in PAF-P5-OH

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

[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 [CBPQT⁴⁺] based [2]­catenanes

A facile method for the synthesis of free-standing pillar[5]arene-based two-dimensional covalent organic monolayers in solution

This report describes a facile method by which, without using any surface-assisted growth or pre-organisation, free-standing two-dimensional (2D) covalent organic monolayers (COMs) were synthesised through condensation reactions of planar tri-aldehydes with A1/A2-diamino-substituted pillar[5]arene (DAP5). In the as-formed monolayers (DAP5-COM-1 and DAP5-COM-2), the tubular pentagonal pillar[5]arene units positioned out of the 2D polymer planes suppress efficiently the interlayer π-π stacking interactions. Both DAP5-COM-1 and DAP5-COM-2 can be transferred onto solid surfaces for further characterisation and were found to possess unusual fluorescence up-conversion property.</p

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

<i>s</i>-Tetrazine-Bridged Photochromic Aromatic Framework Material

Integrating fluorescent chromophores in aromatic frameworks could not only prevent aggregation-induced quenching caused by the π–π stacking interaction between the chromophore components but also confer new fluorescence properties. Herein, we report the fabrication of s-tetrazine-bridged aromatic frameworks TzAF by the incorporation of the smallest aromatic fluorophore, s-tetrazine (Tz), into the skeleton of a tetrahedrally connected lattice of aromatic frameworks. The thin films of TzAF coated on silica gel plates were found to exhibit reversible photoswitching fluorescence characteristics under alternate UV and visible-light irradiations with excellent fluorescence stability and high on/off contrast. The repeatable “on/off”fluorescence photoswitchability of the TzAF thin films was mechanistically attributed to light-induced reversible transformation between TzAF’s neutral and radical states

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 (<b>1</b>)/imidazolium ion recognition motif was created. The pillar[4]­arene[1]­diaminobenzene <b>1</b> can bring an electron-deficient imidazolium cation into its cylindrically shaped cavity under neutral or basic conditions and release it under acidic conditions