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>

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

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

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

Low-Viscosity Tetramethylguanidinum-Based Ionic Liquids with Different Phenolate Anions: Synthesis, Characterization, and Physical Properties

A new series of low-viscosity tetramethylguanidinum-based ionic liquids (ILs) with various substituted phenolate anions were prepared and characterized using nuclear magnetic resonance and Fourier transform irnfrared spectroscopy, elemental analysis, differential scanning calorimetry analysis, and thermogravimetry. Their densities, viscosities, refractive indices, and electrical conductivities were measured and correlated with thermodynamic and empirical equations in the temperature range of (298.15 to 343.15) K under ambient conditions. The effects of substituent groups in phenolate anions on these physical properties were then discussed on the basis of structure. Furthermore, the thermal expansion coefficient was calculated from the experimental values of density, and the correlation between the viscosity and the molar conductivity was proposed by the Walden rule. These ILs are classified as “poor ionic liquids” and have a poor temperature dependency of the thermal expansion coefficient

A Shape-Persistent Cryptand for Capturing Polycyclic Aromatic Hydrocarbons

A shape-persistent cryptand <b>1</b>, 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 <b>1</b> formed 1:1 complexes with PAH guest molecules, such as phenanthrene (<b>6</b>), anthracene (<b>7</b>), pyrene (<b>8</b>), triphenylene (<b>9</b>), and tetraphene (<b>10</b>). The single-crystal structure of complex <b>6⊂1</b> revealed that <b>6</b> was included in the cavity of <b>1</b> via face-to-face π···π stacking interactions. Soaking crystalline <b>1</b> in a toluene solution of anthracene resulted in anthracene from the toluene solution being picked up by the crystalline solid of <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>

A Trigonal Prismatic Ligand in the Metal-Mediated Self-Assembly of One- and Two-Dimensional Metallosupramolecular Polymers

A novel trispyrazine-pillared prismatic bicycooxacalixaromatic ligand <b>L</b> is synthesized, and its application in metal-mediated self-assembly is described. Under self-assembly conditions, single chain, double-stranded cross-linked coordination polymer and two-dimensional (2D) coordination polymeric networks were formed via <b>M</b>-<b>L</b> (Ag⁺, Cu²⁺, and Zn²⁺) coordinative interactions. Structural analyses revealed that the antiparallelly arranged one-dimensional coordination polymers (Cu²⁺ and Zn²⁺) are arranged to generate well-defined voids to host aromatic guests (benzene) via C–H···π and π···π interactions, while the double-stranded cross-linked coordination polymer (Ag⁺) contains a rhomboidal [<b>Ag</b>_<b>2</b><b>(L</b>^<b>3</b><b>)</b>_<b>2</b>] (<b>L</b>^<b>3</b>: tridentate ligand) cage motif to include a benzene guest; the “thicker” (thickness: <i>ac</i> 5 Å) 2D coordination polymeric networks (Ag⁺, Cu²⁺, and Zn²⁺), however, are all formed by connection of one or two kinds of topologically different metallomacrocyclic cage units. These unique metallomacrocyclic cage units in the 2D coordination polymeric networks are capable of hosting different guest species. For instance, the rhomboidal [<b>M</b>_<b>2</b><b>(L</b>^<b>3</b><b>)</b>_<b>2</b>] (M = Ag⁺, Cu²⁺) cage units were found to host a benzene or a nitrate anion; a hexahedral [<b>M</b>_<b>3</b><b>(L</b>^<b>3</b><b>)</b>_<b>3</b>] (M = Ag⁺) cage was found to host a ligand <b>L</b> or a DMF molecule; the hexahedral [<b>M</b>_<b>4</b>(<b>L</b>^<b>3</b><b>)</b>_<b>4</b>] (M = Cu²⁺) cage was found to host four solvent molecules of benzene; and the rectangular [<b>M</b>_<b>3</b>(<b>L</b>^<b>3</b><b>)</b>_<b>3</b>] (M = Cu²⁺, Zn²⁺) cage units, however, were found to host two THF molecules. The results highlight the potential of ligand <b>L</b> for applications in the construction of “thicker” 2D coordination polymeric networks with well-defined metallomacrocyclic cage units capable of hosting various guest species

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>