The syntheses and Ag+-selective electrode properties of benzothiazolylthiaalkoxy functionalized calix[4]arenes: an investigation of the structure–selectivity relationship in the ionophore-based ISEs

Assembling triazolated calix[4]semitubes by means of copper(i)-catalyzed azide–alkyne cycloaddition

Calix[4]arene-based bis(alkynes) and bis(azides) react with each other under thoroughly tuned CuAAC conditions and produce diverse biscalixarene semitube assemblies linked by two triazole units, which are capable of binding transition metal cations.

A self-assembled nanotube supported by halogen bonding interactions

Upper-rim halogenation of a calix[4]arene modulates the packing of self-assembled nanotubes through the formation of complementary halogen bonding interactions.

Novel styrylbenzothiazolium dye-based sensor for mercury, cyanide and hydroxide ions

We report the design and synthesis of a novel styrylbenzothiazolium (3) derivative developed as a fluorescent and colorimetric chemodosimeter with high selectivity toward Hg(2+), CN(-) and OH(-) ions. An obvious loss of pink color in the presence of Hg(2+) and CN(-) ions could make it a suitable "naked eye" indicator. We propose a sensing mechanism whereby the benzenoid form is changed to a quinoid form upon Hg(2+) binding in a 1:1 stoichiometric ratio. More significantly, the styrylbenzothiazolium-Hg(2+) and styrylbenzothiazolium-CN(-) complexes exhibited a dual-channel chromo-fluorogenic response. The sensors exhibit remarkable Hg(2+)-, CN(-)-, and OH(-)-selective red fluorescence but remain dark-green in the presence of a wide range of tested metal ions and anions.

Triazolophanes: a new class of halide-selective ionophores for potentiometric sensors

Triazolophanes, cyclic compounds containing 1,2,3-triazole units, are a new class of host molecules that demonstrate strong interactions with halides. These molecules are designed with a preorganized cavity that interacts through hydrogen bonding with spherical anions, such as chloride and bromide. We have explored the use of one such triazolophane as a halide-selective ionophore in poly(vinyl chloride) (PVC) membrane electrodes. Different membrane compositions were evaluated to identify concentrations of the ionophore, plasticizer, and lipophilic additive that give rise to the best chloride and bromide selectivity. The lipophilicity of the plasticizer was found to have a great impact on the electrode response. Additionally, the concentration of the lipophilic additive was found to be critical for optimal response. The utility of a triazolophane-based electrode was demonstrated by quantification of bromide in horse serum samples.

Synthesis and properties of calix[4]arene telluropodant ethers as Ag+ selective sensors and Ag+, Hg2+ extractants

Three novel phenyltelluroalkoxyl functionalized tweezer-like calix[4]arenes 6-8 and two monophenyltelluropropoxyl functionalized calix[4]arenes 10 (cone conformer) and 12 (partial cone conformer) were synthesized and characterized. They are good Ag(+)-selective ionophores in ion-selective electrodes evaluated by electromotive force measurements of polymer membrane electrodes. The tweezer-like ionophores 6-8 showed excellent extraction ability towards Ag(+) and Hg(2+).

5,11,17,23-Tetra-tert-butyl-25,27-bis-[2-(4-nitro-phen-oxy)eth-oxy]calix[4]arene-26,28-diol acetonitrile tetra-solvate

In the crystal structure of the title compound, C₆₀H₇₀N₂O₁₀·4CH₃CN, the calix[4]arene mol­ecule adopts an open-cone conformation with two intra­molecular O—H⋯O hydrogen bonds. The four benzene rings of the calix[4]arene are twisted to the mean plane defined by four methyl­ene C atoms bridging the benzene rings, with dihedral angles ranging from 57.74 (10) to 65.99 (12)°. Two pendant nitro­phenyl rings are nearly perpendicular to each other, the dihedral angle being 70.9 (3)°. The asymmetric unit of the crystal structure contains four acetonitrile solvent mol­ecules, one of which lies in the calix cavity and makes C—H⋯π inter­actions and another links with the calix[4]arene via C—H⋯O hydrogen bonding. One tert-butyl group is disordered over two sets of sites, with a 0.736 (13):0.264 (13) occupancy ratio.

Synthesis of calix[4]arenes bearing benzothiazolyl, benzoxazolyl and benzoimidazolyl heterocycles

A novel series of calix[4]arenes bearing benzothiazole, benzoxazole, and benzoimidazole groups were obtained by the reaction of the corresponding 2-mercaptoheterocycle with 5,11,17,23-tetra- tert-butyl-25,27-bis[2-(chloroacetamido) ethoxy]-26,28-di-hydroxycalix[4]arene and structurally characterised by IR, 1H NMR, 13C NMR, Mass spectra and elemental analyses. From their analytical data, it was found these compounds had cone conformations.

Silver(i) N-heterocyclic carbene-bridged calix[4]arene analogues as efficient [60]fullerene receptors

Two silver(I) N-heterocyclic carbene-bridged calix[4]arene analogues 4 and 5 were synthesized by a fragment-coupling approach; the preliminary inclusion properties of 5 with [60]fullerene shows that it is a novel efficient [60]fullerene fluorescent sensor.

Novel potentiometric and optical silver ion-selective sensors with subnanomolar detection limits

Ten Ag+-selective ionophores have been characterized in terms of their potentiometric selectivities and complex formation constants in solvent polymeric membranes. The compounds with pi-coordination show much weaker interactions than those with thioether or thiocarbamate groups as the coordinating sites. Long-term studies with the best ionophores show that the lower detection limit of the best Ag+ sensors can be maintained in the subnanomolar range for at least 1 month. The best ionophores have also been characterized in fluorescent microspheres. The so far best lower detection limits of 3 x 10(-11) M (potentiometrically) and 2 x 10(-11) M Ag+ (optically) are found with bridged thiacalixarenes.

Studies on a Pb2+ - selective electrode with a macrocyclic liquid membrane: Potentiometric determination of pb2+ ions

This paper presents experimental and theoretical data regarding the design, characterization and analytical applications of a non-expensive, liquid-membrane ion-selective electrode for Pb2+ ions. The membrane is a solution of the active complex formed by Pb2+ ions with dibenzo-18-crown-6-ionophore (DB-[18]-C-6) extracted in propylene carbonate (PC). The successful application of the developed electrode for the determination of Pb2+ ions in aqueos solution samples by direct potentiometry and potentiometric titration is presented. For the presented analytical results, there are insignificant systematic errors between the direct potentiometric method with the developed ion-selective electrode and atomic absorption spectrometry. .