Anion‐ and Spacer‐Directed Host–Guest Complexes of Bipyridine with Pyrogallol[4]arene

New oval‐shaped capsular and bilayer‐type hydrogen‐bonded arrangements of C‐propyl‐ol‐pyrogallol[4]arene (PgC3‐OH) with bipyridine‐type spacer complexes are reported here. These complexes are engineered by virtue of derivatization of C‐alkyl tails of pyrogallol[4]arene and the use of divergent spacer ligands. Complexes of PgC3‐OH, PgC3‐OH with bpy (4,4′‐bipyridine) and PgC3‐OH with bpa (1,2‐bis(4‐pyridyl)acetylene) have bilayer type arrangements; however, the use of hydrogen chloride causes protonation of bpy molecule, which is then entrapped flat within an offset oval‐shaped dimeric hydrogen‐bonded PgC3‐OH nanocapsule. The presence of chloride anion in the crystal lattice controls the geometry of the resultant nanoassembly.     

Synthesis, crystal structure and configuration of acetylated aryl Pyrogallol[4]arenes

A series of aryl and ferrocenyl pyrogallol[4]arenes have been synthesized by the HCl-catalyzed condensation reactions of pyrogallol with aromatic aldehydes and ferrocenecarbaldehyde. The fully acetyl and ethoxycarbonylmethoxy derivatives were also prepared and fully characterized. The crystal structures show that acylated phenyl pyrogallol[4]arene exists in rctt (cis-trans-trans) configuration, while the corresponding ferrocenyl pyrogallol[4]arene in rccc (all cis) configuration.     

Pyrogallol[4]arenes show highly variable amphiphilic behavior at the air-water interface dependent upon side chain length and branching

The behavior of pyrogallol[4]arenes (Pgs) substituted with normal and branched alkyl side chains at the air-water interface was examined on a Langmuir trough. The amphiphilic systems studied form stable monolayers when the straight chains are as short as n-propyl. Remarkably, n-propylpyrogallol[4]arene shows a behavior at the air-water interface that is indistinguishable from that of pyrogallolarenes bearing n-hexyl, n-nonyl, and n-dodecyl side chains. There is no report of amphiphilic side-chain-length dependence or Langmuir trough behavior for families of branched alkyl chain calixarenes or resorcinarenes. In the Pg family reported here, Pgs with straight chains (except for methyl and ethyl) behave very similarly to each other and very differently from symmetrical branched chain analogues having the same total number of carbon atoms. For example, the shortest possible branched side chain of a Pg, isopropyl-Pg, forms stable monolayers by a unique molecular subduction mechanism. Isopropyl-Pg (dimethylmethyl side chain, iPrPg) and 3-pentyl-Pg (diethylmethyl side chain, 3-pentylPg) both show high levels of organization, albeit by quite different mechanisms, at the air-water interface. Both iPrPg and 3-pentylPg differ in behavior from 4-heptylPg. Brewster angle microscopy revealed differences in organization of the Pgs that supports the mechanistic suggestions offered herein.     

X-Ray Structure of an Inclusion Compound of 5,5'-Biscalix[4]arene-hexabenzoate with Toluene

The structure of the 1:3 complex between 5,5'-biscalix[4]arene-hexabenzoateand toluene has been determined by a single crystal X-ray diffraction study. Thetwo calix[4]arene subunits of the 5,5'-biscalix[4]arene system are related by aninversion center and are joined by an eclipsed biphenyl para-para linkage. Each calix[4]arene moiety displays a 1,3-alternate conformation and includes a toluene molecule within two opposite benzoate groups, while a third toluene molecule lies close to a crystallographic inversion center.     

Microwave-assisted synthesis of resorcin[4]arene and pyrogallol[4]arene macrocycles

A series of resorcin[4]arene and pyrogallol[4]arene macrocycles have been synthesized efficiently within 5 min, affording crystalline products suitable for single crystal X-ray diffraction, utilising microwave irradiation in a ‘one-pot’ reaction whilst controlling the selective formation of the rccc cone stereoisomer.     

Microwave Assisted Efficient Synthesis and Crystal Structures of O-Hexadecalkylated Pyrogallol[4]arenes

Under microwave irradiation alkylation reactions of sixteen phenolic hydroxyl groups in tetra(p‐hydroxyphenyl)pyrogallol[4]arene with alkylating reagents such as n‐butyl iodide, benzyl chloride, and ethyl α‐chloroacetate were finished quickly in one step to give the fully O‐alkylated products. The X‐ray single crystal diffraction showed that the three peralkylated pyrogallol[4]arenes existed in rctt (cis‐trans‐trans) configuration.     

Ionic galleries: a bilayered host-guest cocrystal of C-propyl pyrogallol[4]arene with an ionic liquid

We report on a cocrystal between C-propyl pyrogallol[4]arene and the ionic liquid 1-ethyl-3-methylimidazolium ethylsulfate exhibiting a remarkable bilayer topology comprising two unique host-guest complexes resulting from the ionic liquid cation binding in two distinctive orientations relative to the macrocycle.     

Evidence of Hydrogen Bonding in Stabilizing the Cone Conformation of a Monoalkylated Calix[4]arene. X-ray Structure of 25-[2-(ethoxy-1-p-toluene-sulfonate)phenyl]-26,27,28-trihydroxy calix[4]arene

The synthesis of25-[2-(ethoxy-1-p-toluene-sulfonate)phenyl]-26,27,28-trihydroxy calix[4]arene3 as a byproduct of the preparation of 1,3-dialkylated25,27-di-[2-(ethoxy-1p-toluene-sulfonate)phenyl]-26,28-dihydroxy calix[4]arene 2 is reported. Compound 3 is a monoalkylatedcalix[4]arene in the cone conformation. The X-ray structure of 3 showed that this conformation is stabilized by intramolecular hydrogen bonding.     

Synthesis,crystal structure and complexation behaviour of a thiacalix[4]arene bearing 1,2,3-triazole groups

The structure and complexation behaviour of 1,3-alternate-1,2,3-triazole based on thiacalix[4]arene,1,3-alternate-1 and 2 have been determined by means of X-ray analysis, fluorescence and ¹H NMR spectroscopy. The X-ray results suggested that the nitrogen atom N3 on triazole ring can act as hydrogen bond acceptors in the self-assembly of a supramolecular structure. The fluorescence spectra changes indicated that the thiacalix[4]arene bearing 1,2,3-triazole groups were highly selective for Ag⁺ in comparison with other tested metal ions by enhancement of the monomer emission of pyrene. The ¹H NMR results suggested that Ag⁺ can be strongly bonded by the triazole groups with the cooperation of the ionophoric cavity formed by the two inverted benzene rings and the sulfur atoms of the thiacalix[4]arene.     

An Indium‐Seamed Hexameric Metal–Organic Cage as an Example of a Hexameric Pyrogallol[4]arene Capsule Conjoined Exclusively by Trivalent Metal Ions

A hexameric metal–organic nanocapsule is assembled from pyrogallol[4]arene units, which are stitched together with indium ions. This indium‐seamed capsule is the first instance of a M₂₄L₆ type hexameric coordination cage held together exclusively by trivalent metal ions. Explicitly, unlike previously reported pyrogallol[4]arene‐based metal‐seamed capsules, the current In³⁺ seamed capsule is entirely supported by O→In coordinate bonds. This work demonstrates the important proof of concept of the ability of pyrogallol[4]arene to react with metals in higher oxidation states to assemble into atomically‐precise hexameric coordination cages. As such, these results open up exciting avenues toward the assembly of previously unanticipated metal–organic capsules, for example offering inspiration for tackling metals exhibiting high valence states such as in the lanthanide and actinide series.     

Synthesis and structural characterization of a binuclear zirconium complex of tetraanionic p-tert-butylthiacalix[4]arene bridged by methanol

A zirconium complex with the p-tert-butylthiacalix[4]arene anion was synthesized and its crystal structure was determined by single-crystal X-ray analysis. The complex [Zr(μ₂-CH₃OH)(p-tert-butylthiacalix[4]arene)]₂·9H₂O (1) belongs to the orthorhombic system, space group Pnnm, with a?=?20.436(16), b?=?12.160(8), c?=?20.305(12)?Å, V?=?6774(7)?ų and Z?=?2. In Complex 1 zirconium coordinates to four phenolic anions of the deprotonated p-tert-butylthiacalix[4]arene and is bridged by two methanol molecules; the p-tert-butylthiacalix[4]arene adopts a cone conformation.     

An Indium-Seamed Hexameric Metal–Organic Cage as an Example of a Hexameric Pyrogallol[4]arene Capsule Conjoined Exclusively by Trivalent Metal Ions

A hexameric metal–organic nanocapsule is assembled from pyrogallol[4]arene units, which are stitched together with indium ions. This indium-seamed capsule is the first instance of a M₂₄L₆ type hexameric coordination cage held together exclusively by trivalent metal ions. Explicitly, unlike previously reported pyrogallol[4]arene-based metal-seamed capsules, the current In³⁺ seamed capsule is entirely supported by O→In coordinate bonds. This work demonstrates the important proof of concept of the ability of pyrogallol[4]arene to react with metals in higher oxidation states to assemble into atomically-precise hexameric coordination cages. As such, these results open up exciting avenues toward the assembly of previously unanticipated metal–organic capsules, for example offering inspiration for tackling metals exhibiting high valence states such as in the lanthanide and actinide series.     

Synthesis and properties of potassium salts of per-<Emphasis Type="Italic">O</Emphasis>-carboxymethyl-calix[4]pyrogallols and their complexes with Cu<Superscript>2+</Superscript>, Fe<Superscript>3+</Superscript>, and La<Superscript>3+</Superscript>

Synthesis of water-soluble potassium salts of carboxymethyl derivatives of calix[4]pyrogallols and dodeca(carboxylatomethyl)tetramethylcalix[4]pyrogallol (L) complexes with transition metal ions (Cu²⁺, Fe³⁺, La³⁺) is described. Their structures in the solid state and in solution were characterized by NMR spectroscopy, ESR, and IR spectroscopy. Calix[4]pyrogallol dodecacarboxylates exist in the rccc-configuration. Calix[4]pyrogallol with methyl substituents at the lower rim in a wide range concentrations exists in water predominantly in the dimeric form. The obtained polynuclear transition metal complexes possess less symmetric structure than potassium salt of calix[4]pyrogallol (K₁₂L). All studied complexes contain water molecules bound by rather strong hydrogen bonds. At room temperature the Fe₄L complex is characterized by the environment of the Fe³⁺ ions close to octahedral. The absence of signals in the ESR spectrum of the Cu₆L complex indicates the strong antiferromagnetic interaction Cu²⁺-Cu²⁺.     

Water as a building block in solid-state acetonitrile-pyrogallol[4]arene assemblies: structural investigations

Under various conditions, water molecules dramatically affect a number of solid-state C-alkylpyrogallol[4]arene assemblies. In the absence of water, hydrogen-bonded hexameric capsules are formed for the C-butyl, pentyl, hexyl, and heptyl pyrogallol[4]arenes. Introduction of water to acetonitrile solutions containing C-propyl-C-octylpyrogallol[4]arenes resulted in the formation of markedly different bilayer structures and the structural identification of two new dimer-type motifs.     

Second-sphere coordination in the complex [Mn(H2O)6]2[thiacalix[4]arene tetrasulfonate]

The title calixarene, dimanganese thiacalix[4]arene tetrasulfonate, was prepared and its crystal structure was determined. [Mn(H₂O)₆]₂[thiacalix[4]arene tetrasulfonate]·0.5H₂O crystallizes in the monoclinic system, P2(1)/m space group, with a=13.014 (6), b=14.146 (9), c=13.184 (7) Å, β=113.307 (10)°, V=2229 (2) Å³ and Dc=1.710 gcm⁻³, Z=2. The title calixarene exists in the solid state as bilayer structure. The hydrophobic organic layer consists of thiacalix[4]arene tetrasulfonate in an up-down fashion, whereas, the hydrophilic inorganic layer consists of hexaaquamanganese (II) which is linked to the former through a second-sphere coordination.     

p-tert-Butylcalix[5]arene: a New Synthetic Pathway and Crystal Structure of the N,N-Dimethylformamide Complex

The formation of p-tert-butylcalix[5]arene by the opening ofp-tert-butyldihomooxacalix [4]arene and the addition of a monomer has beenstudied. Various facets, including the effects of bases and the nature ofthe monomer added to the p-tert-butyldihomooxacalix[4]arene, have beeninvestigated. p-tert-Butylcalix[5]arene can be prepared in yields up to30%. The structure of its 1 : 2 complex with DMF has been determinedby X-ray crystallography. Crystals are triclinic, space group P¯1, a =1428.2(3) pm, b = 1837.3(3) pm, c = 1276.1(2) pm, = 108.98(1)°, = 105.02(2)°, = 95.21(1)°, Z = 2, D _c = 1.059 kg m^-3,final R value = 0.087. The macrocycle adopts a cone conformation, one guestenclosed inside the cavity, the other one outside.     

Ion channel formation from a calix[4]arene amide that binds HCl

The ion transport activity of calix[4]arene tetrabutylamide 1,3-alt 2 was studied in liposomes, planar lipid bilayers, and HEK-293 cells. These experiments, when considered together with (1)H NMR and X-ray crystallography data, indicate that calix[4]arene tetrabutylamide 2 (1) forms ion channels in bilayer membranes, (2) mediates ion transport across cell membranes at positive holding potential, (3) alters the pH inside liposomes experiencing a Cl(-) gradient, and (4) shows a significant Cl(-)/SO(4)(2)(-) transport selectivity. An analogue, calix[4]arene tetramethylamide 1, self-assembles in the presence of HCl to generate solid-state structures with chloride-filled and water-filled channels. Structureminus signactivity studies indicate that the hydrophobicity, amide substitution, and macrocyclic framework of the calixarene are essential for HCl binding and transport. Calix[4]arene tetrabutylamide 2 is a rare example of an anion-dependent, synthetic ion channel.     

Non-covalent expansion of an organic bilayer involving exo-cavity interplay of tetraphenylphosphonium with para-sulfonato-calix[4]arene

Reaction of equimolar amounts of sodium para-sulfonato-calix[4]arene, tetraphenylphosphonium chloride and ytterbium chloride in water results in the formation of a mineral clay-like structure, where the hydrophobic tetraphenylphosphonium cations interpose a bilayer arrangement based on a 2D coordination polymer of (calix[4]arene)5-/Na+/Yb3+.     

Acridine N-Heterocyclic Carbene Gold(I) Compounds: Tuning from Yellow to Blue Luminescence

The synthesis and the luminescence features of three gold(I)-N-heterocyclic carbene (NHC) complexes are presented to study how the n-alkyl group can influence the luminescence properties in the crystalline state. The mononuclear gold(I)-NHC complexes, [( L¹ )Au(Cl)] ( 1 ), [( L² )Au(Cl)] ( 2 ), and [( L³ )Au(Cl)] ( 3 ) were isolated from the reactions between [(tht)AuCl] and corresponding NHC ligand precursors, [N-(9-acridinyl)-N’-(n-butyl)-imidazolium chloride, ( L¹ .HCl)], [N-(9-acridinyl)-N’-(n-pentyl)-imidazolium chloride, ( L² .HCl)] and [N-(9-acridinyl)-N’-(n-hexyl)-imidazolium chloride, ( L³ .HCl)]. Their single-crystal X-ray analysis reveals the influence of the n-alkyl groups on solid-state packing. A comparison of the luminescence features of 1 – 3 with n-alkyl substituents is explored. The molecules 1 – 3 depicted blue emission in the solution state, while the yellow emission (for 1 ), greenish-yellow emission (for 2 ), and blue emission (for 3 ) in the crystalline phase. This paradigm emission shift arises from n-butyl to n-pentyl and n-hexyl in the crystalline state due to the carbon-carbon rotation of the n-alkyl group, which tends to promote unusual solid packing. Hence n-alkyl group adds a novel emission property in the crystalline state. Density Functional Theory and Time-Dependent Density Functional Theory calculations were carried out for monomeric complex, N-(9-acridinyl)-N’-(n-heptyl)imidazole-2-ylidene gold(I) chloride and dimeric complex, N-(9-acridinyl)-N’-(n-heptyl)imidazole-2-ylidene gold(I) chloride to understand the structural and electronic properties.     

Synthesis and photochemical reaction of cyclic oligomers: Synthesis and photopolymerization of novel C‐methylcalix[4]resorcinarene and p‐alkylcalix[n]arene derivatives containing spiro ortho ether groups

New photoreactive calixarene derivatives containing spiro ortho ester groups (calixarenes 3a–3c ) were synthesized by the reaction of 2‐bromomethyl‐1,4,6‐trioxaspiro[4.4]nonane with 2,8,14,20‐tetramethyl‐4,6,10,12,16,18,22,24‐octakis(carboxymethoxy)calix[4]resorcinarene, 5,11,17,23,29,35‐hexamethyl‐37,38,39,40,41,42‐hexakis(carboxymethoxy)calix[6]arene, and 5,11,17,23,29,35,41,47‐octa‐tert‐butyl‐49,50,51,52, 53,54,55,56‐octakis‐(carboxymethoxy)calix[8]arene, which were prepared by the reaction of C‐methylcalix[4]resorcinarene, p‐methylcalix[6]arene, and p‐tert‐butylcalix[8]arene, respectively. The thermal stability of the obtained calixarene derivatives containing spiro ortho ester groups was examined with thermogravimetric analysis, and it was found that these calixarene derivatives had good thermal stability. The photoinitiated cationic polymerization of spiro ortho ester groups in calixarene derivatives 3a–3c was examined with certain photoacid generators in the film state. Interestingly enough, the reaction of calixarene derivatives did not proceed with only photoirradiation; however, the reaction proceeded smoothly when the photoirradiation was followed by heating. Furthermore, calixarene 3a , composed of a C‐methylcalix[4]resorcinarene structure, showed the highest photochemical reactivity in this reaction system. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1293–1302, 2002