Tailoring fluorescent ZIF-8 nanostructures through calix[4]pyrrole modification: tunable size and enhanced organic micropollutant removal capacity.

Whitish-blue light emitting fluorescent ZIF-8 structures were synthesized by means of bis-carboxylate functional calix[4]pyrrole (BCCP) modification. The calix[4]pyrrole concentration was also manipulated to tune the sizes of the ZIF-8 structures. Moreover, the BCCP-modified ZIF-8 samples exhibited enhanced organic micropollutant removal capacity from aqueous solutions.

A poly-pseudorotaxane constructed by threading pillar[5]arene onto an ion-pair recognition-based calix[4]pyrrole supramolecular polymer.

The ion-pair recognition ability of calix[4]pyrrole was utilized to form a multicomponent monomeric assembly and a linear supramolecular polymer via concurrent anion and bis-cation complexation. The inherent dynamic interactions of these assemblies were further used to construct pseudorotaxanes in monomeric and supramolecular polymer forms with pillar[5]arene.

An AB2 -Type Hyperbranched Supramolecular Polymer Based on Calix[4]Pyrrole Anion Recognition: Construction, Stimuli-Responsiveness, and Morphology Tuning.

An AB2 -type monomer comprised of a calix[4]pyrrole skeleton and alternating bis-carboxylate units is reported and used for the construction of a novel supramolecular hyperbranched polymer based on anion recognition ability of calix[4]pyrrole. 1 H-, DOSY-NMR spectroscopy, viscosity measurements, and dynamic light scattering techniques are used for the characterization of the supramolecular hyperbranched polymer exhibiting thermo-, pH-, and chemical responsiveness, as well as concentration dependent morphology tune as inferred from electron microscopy analyses. The present study enriches the field of supramolecular polymers with a new construction motif, building block, and provides a simple approach for the fabrication of smart polymer material with multi-responsiveness and -morphologies.

Development of Highly Luminescent Water-Insoluble Carbon Dots by Using Calix[4]pyrrole as the Carbon Precursor and Their Potential Application in Organic Solar Cells.

Carbon dots (CDs) are carbon-based fluorescent nanomaterials that are of interest in different research areas due to their low cost production and low toxicity. Considering their unique photophysical properties, hydrophobic/amphiphilic CDs are powerful alternatives to metal-based quantum dots in LED and photovoltaic cell designs. On the other hand, CDs possess a considerably high amount of surface defects that give rise to two significant drawbacks: (1) causing decrease in quantum yield (QY), a crucial drawback that limits their utilization in LEDs, and (2) affecting the efficiency of charge transfer, a significant factor that limits the use of CDs in photovoltaic cells. In this study, we synthesized highly luminescent, water-insoluble, slightly amphiphilic CDs by using a macrocyclic compound, calix[4]pyrrole, for the first time in the literature. Calix[4]pyrrole-derived CDs (CP-DOTs) were highly luminescent with a QY of over 60% and size of around 4-10 nm with graphitic structure. The high quantum yield of CP-DOTs indicated that they had less amount of surface defects. Furthermore, CP-DOTs were used as an additive in the active layer of organic solar cells (OSC). The photovoltaic parameters of OSCs improved upon addition of CDs. Our results indicated that calix[4]pyrrole is an excellent carbon precursor to synthesize highly luminescent and water-insoluble carbon dots, and CDs derived from calix[4]pyrrole are excellent candidates to improve optoelectronic devices.

A calix[4]pyrrole-based linear supramolecular polymer constructed by orthogonal self-assembly.

A calix[4]pyrrole having a ureidopyrimidinone unit was successfully synthesized from its alcohol-functionalized congener and further used for the first time to obtain a thermo- and chemical-responsive linear supramolecular polymer via orthogonal self-assembly comprising a combination of quadruple hydrogen bonding and anion recognition.

Supramolecular calix[4]pyrrole polymers from a complementary pair of homoditopic host-guest molecules.

A triazole bridged bis-calix[4]pyrrole was successfully synthesized and further used for the first time to construct AABB type linear thermoresponsive supramolecular polymers by utilizing the host-guest interaction between calix[4]pyrroles and carboxylate units of tetrabutylammonium suberate.

A thermoresponsive supramolecular polymer gel from a heteroditopic calix[4]pyrrole.

Supramolecular polymerization of calix[4]pyrroles bearing tethered carboxylate functional groups was reported in the form of their tetrabutylammonium salts. At high concentrations one of the calix[4]pyrroles with a shorter linker between the calixpyrrole core and the carboxylate unit was found to give a thermoresponsive supramolecular polymer gel.

Reversible assembly and disassembly of receptor-decorated gold nanoparticles controlled by ion recognition.

The controlled assembly of randomly dispersed colloidal particles can provide access to materials with advanced optical and electronic properties while providing fundamental insights into self-assembly processes in nature and nanotechnology. Typically, self-assembled nanoparticles are prepared by exploiting electrostatic interactions, lithographic techniques, and covalently linked molecular scaffolds. This results in static morphologies that cannot be disassembled easily. On the other hand, having access to systems that can be assembled or disassembled in a controlled manner could allow for in-depth understanding of the nanoparticles as well as rational control over the morphology and fundamental properties of the resulting constructs. If the changes in aggregation are induced by a specific external chemical stimulus, it could also permit the development of new chemosensors. Here we demonstrate the reversible assembly and disassembly of gold nanoparticles achieved by modulating the noncovalent interactions between surface-bound calix[4]pyrroles and added bis-imidazolium cations. We also demonstrate the use of these nanoparticles in the selective sensing of anions.

An imidazolium-functionalized self-assembling calix[4]pyrrole.

A calixpyrrole bearing a tethered imidazolium functional group was prepared in the form of its bromide salt. This compound was found to undergo self-assembly to produce supramolecular polymers, wherein both the bromide anion and the imidazolium cation are bound to the calixpyrrole core.

EDOT-functionalized calix[4]pyrrole for the electrochemical sensing of fluoride in water.

A new calix[4]pyrrole compound bearing an electropolymerizable EDOT substituent (1) was synthesized, and its electrochemical behavior was investigated. The anion sensor ability of 1 was also studied in solution and in the solid state. Compound 1 interacts with halide ions selectively in solution, which illustrates its possible application as an anion sensor. To test possible practical applications, 1 and EDOT were electropolymerized on an ITO electrode, and this electrode was used as an effective fluoride anion sensor in the solid state.

Decoration of gold nanoparticles by a double-armed calix[4]pyrrole: a receptor-decorated nanoensemble for anion sensing and extraction.

Gold nanoparticles decorated with a double-armed, deep-cavity calix[4]pyrrole were prepared and fully characterized. Transmission electron microscopy imaging revealed that the average diameter of the particles was approximately 4 nm both before and after attachment of the receptor to the surface. The calix[4]pyrrole-functionalized nanoparticles exhibited highly elevated sensing behavior (approximately 1000 times in dichloromethane) relative to its monomeric congener while maintaining its guest selectivity. The receptor-nanoparticle conjugate (nanoreceptor) showed significant aggregation upon addition of the biphenolate anion, an effect ascribed to anion-mediated interparticle linking. The receptor-nanoparticle conjugate is also capable of extracting the fluoride anion (as its tetrabutylammonium salt) from an aqueous layer to an organic medium. Control experiments revealed that this extraction is not possible when using the analogous monomeric receptor.

Tri- and pentacalix[4]pyrroles: synthesis, characterization and their use in the extraction of halide salts.

Calixpyrrole-based oligomeric compounds were synthesized by "click chemistry" from the corresponding alkyne- and azide-functionalized calix[4]pyrroles. Calix[4]pyrrole 3, possessing an alkyne functional group, was prepared through a mixed condensation of pyrrole with acetone and but-3-ynyl 4-oxopentanoate. Another alkyne-group-containing calix[4]pyrrole 5 was obtained by treatment of 4'-hydroxyphenyl-functionalized calixpyrrole 4 with propargyl bromide. Tetrakis(azidopentyl)-functionalized calix[4]pyrrole 7 was synthesized by reacting NaN(3) with tetrabromopentyltetraethylcalix[4]pyrrole 6, which was prepared through a condensation reaction of pyrrole and 7-bromohept-2-one. Oligomeric calixpyrrole compounds were found to be capable of extracting tetrabutylammonium chloride and fluoride salts from aqueous media. Extraction abilities of the oligomeric compounds were monitored by NMR and UV/Vis spectroscopy and thermogravimetric analysis.

5,10,10,15,20,20-Hexamethylcalix[4]pyrrole 5,15-diethyl diester.

In the title compound, C(32)H(40)N(4)O(4), the pyrrole rings and ester groups adopt a 1,3-alternate conformation in which the alternating pyrrole and ester units are in opposite directions. The structure displays N-H⋯O hydrogen bonding and exhibits disorder [site occupancies of 0.81(2) and 0.71(2)] in the peripheral ethyl groups.

Poly(methyl methacrylate)s with pendant calixpyrroles: polymeric extractants for halide anion salts.

Poly(methyl methacrylate)s containing pendant octamethylcalix[4]pyrrole subunits were prepared and demonstrated to be capable of extracting tetrabutylammonium chloride and fluoride salts from aqueous media.