<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

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>

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

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

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

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

Covalent Triazine-Based Polymers with Controllable Band Alignment Matched with BiVO₄ To Boost Photogeneration of Holes for Water Splitting

To promote the charge carrier utilization for efficient photoelectrochemical (PEC) water splitting, we design novel covalent triazine-based polymers (CTPs) with a controllable energy band alignment to construct hybrid heterojunction photoanodes with BiVO4 based on energy band matching conception. The energy bands of CTPs with the same triazine backbone can match well with BiVO4 by lengthening the aryl groups as electron donors through a convenient aromatic nucleophilic substitution reaction to enhance charge separation and transfer capacity. Typically, a CTP with a naphthyl group, that is, CTP2 hybridized with BiVO4 indicates a distinctly reinforced PEC performance profiting from the quick hole extraction from BiVO4 via an efficient built-in electric field. Accordingly, the hybrid BiVO4/CTP2 electrode with the aid of iron/nickel hydroxyl oxide realizes a prominent photocurrent density of 4.05 mA cm–2 and the corresponding H2/O2 amounts of 676/338 μmol cm–2 after the stability test of 10 h at 1.23 V versus a reversible hydrogen electrode, which is ca. sevenfold as large as the pristine BiVO4 electrode. Hence, the energy band modulation and matching could be one of the conducive references to design hybrid heterojunctions from the aspect of organics

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

A novel tricylic host molecule <b>1</b> 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 <b>G1</b> and paraquat <b>G2</b>, with its two macrocyclic subunits, to form a four-component complex <b>2G1⊂1⊃G2</b>. An ¹H NMR study of stepwise bindings of <b>G1</b> and <b>G2</b> to host <b>1</b> in CDCl₃/DMSO-<i>d</i>₆ revealed that the strength of the association between complex <b>2G1⊂1</b> and guest <b>G2</b> was only one-fourth of that between free <b>1</b> and <b>G2</b>, demonstrating a negative heterotropic cooperativity of <b>G1</b> in the binding of <b>G2</b> to host <b>1</b>

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

A novel tricylic host molecule <b>1</b> 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 <b>G1</b> and paraquat <b>G2</b>, with its two macrocyclic subunits, to form a four-component complex <b>2G1⊂1⊃G2</b>. An ¹H NMR study of stepwise bindings of <b>G1</b> and <b>G2</b> to host <b>1</b> in CDCl₃/DMSO-<i>d</i>₆ revealed that the strength of the association between complex <b>2G1⊂1</b> and guest <b>G2</b> was only one-fourth of that between free <b>1</b> and <b>G2</b>, demonstrating a negative heterotropic cooperativity of <b>G1</b> in the binding of <b>G2</b> to host <b>1</b>

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

A novel tricylic host molecule <b>1</b> 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 <b>G1</b> and paraquat <b>G2</b>, with its two macrocyclic subunits, to form a four-component complex <b>2G1⊂1⊃G2</b>. An ¹H NMR study of stepwise bindings of <b>G1</b> and <b>G2</b> to host <b>1</b> in CDCl₃/DMSO-<i>d</i>₆ revealed that the strength of the association between complex <b>2G1⊂1</b> and guest <b>G2</b> was only one-fourth of that between free <b>1</b> and <b>G2</b>, demonstrating a negative heterotropic cooperativity of <b>G1</b> in the binding of <b>G2</b> to host <b>1</b>