Calix[4]arene based chemosensor for selective complexation of Cd(II) and Cu(II)

Synthesis of Core-Shell Magnetic Supramolecular Nanocatalysts based on Amino-Functionalized Calix[4]arenes for the Synthesis of 4H-Chromenes by Ultrasonic Waves

One of the most common phenol-formaldehyde cyclic oligomers from hydroxyalkylation reactions that exhibit supramolecular chemistry are calixarenes. These macrocyclic compounds are qualified to act as synthetic catalysts due to their specific features including being able to form host-guest complexes, having unique structural scaffolds and their relative ease of chemical modifications with a variety of functions on their upper rim and lower rim. Here, a functional magnetic nanocatalyst was designed and synthesized by using a synthetic amino-functionalized calix[4]arene. Its catalytic activity was evaluated in a one-pot synthesis of 2-amino-4H-chromene derivatives. Besides, this novel magnetic nanocatalyst was characterized by spectroscopic and analytical techniques such as FT-IR, EDX, FE-SEM, TEM VSM, XRD analysis.

pH-controlled preferential binding of cucurbit[7]uril-coated iron-oxide nanoparticles to 6-mercaptonicotinic acid for fluorescent detection of cadmium ions in the solid state

A host-guest complex of 6-mercaptonicotinic acid (MNA) and cucurbit[7]uril (CB7) was prepared and conjugated to γ-Fe₃O₄ nanoparticles (NPs) to detect toxic cadmium ions in water as a solid-state sensor. The formation of an inclusion host-guest complex with CB7 was confirmed by UV-vis absorption and proton NMR spectroscopy. CB7 preferentially binds the protonated MNA form compared to the neutral form, demonstrated by a binding constant for the protonated form that is four orders of magnitude higher than that of the neutral form. An increase in the pK_a of MNA by 1.2 units was demonstrated after the addition of CB7, which further supports preferential binding between MNA and CB7. The NMR results confirm binding to cadmium via the carboxylic acid moiety. Stationary and time-resolved fluorescence results, in solution and in the solid state, indicate that cadmium and CB7 cause a blue shift in the MNA emission bands and extend its excited-state lifetime due to dissociation of the MNA dimer. In the solid state, switching the emission signals between Cd²⁺-MNA/CB7NPs (ON state) and MNAH⁺/CB7NPs (OFF state) was achieved by controlling the pH. An efficient, regenerable, and stable sensor device was fabricated for sensitive and selective detection of Cd²⁺ in contaminated water samples. Graphical abstract Regeneration of MNA/CB7 nanoparticles for the detection of cadmium ions in the solid state by a visible blue emission signal upon suppression of photoinduced electron transfer (PET).

Functionalized calix[4]arene as a colorimetric dual sensor for Cu(ii) and cysteine in aqueous media: experimental and computational study

The sensors developed detect Cu²⁺and the metal complex recognizes cysteine, detectable by the naked eye, and DFT calculations corroborate the experimental results.

Optical sensor arrays for chemical sensing: the optoelectronic nose

A comprehensive review is presented on the development and state of the art of colorimetric and fluorometric sensor arrays. Optical arrays based on chemoresponsive colorants (dyes and nanoporous pigments) probe the chemical reactivity of analytes, rather than their physical properties. This provides a high dimensionality to chemical sensing that permits high sensitivity (often down to ppb levels), impressive discrimination among very similar analytes and exquisite fingerprinting of extremely similar mixtures over a wide range of analyte types, both in the gas and liquid phases.

2,2′-(Hydrazine-1,2-diylidenedimethylylidene)bis(6-isopropyl-3-methylphenol) based selective dual-channel chemosensor for Cu2+ in semi-aqueous media

A novel receptor based on a substituted salicylaldehyde derivative, 2,2′-(hydrazine-1,2-diylidenedimethylylidene)bis(6-isopropyl-3-methylphenol) (1), was synthesized and characterized using various spectroscopic techniques.

Interaction of para-tert-butylcalix[6]arene molecules in Langmuir films with cadmium ions and their effects on molecular conformation and surface potential

The SFG data show the orientation of Calix6 molecules at the air/water interface, and their interaction with Cd ions.

An excellent copper selective chemosensor based on calix[4]arene framework

The article depicts a detailed study regarding copper selective chemosensing and complexation nature of 5,11,17,23-tetrakis[(N,N-diphenylamino)methyl]-25,26,27,28-tetrahydroxycalix[4]arene (PAC4). Its photophysical characteristics in various solvents of different polarities along with the influence of acid and base on its spectral properties in these solvents are also discussed. The complexation affinity of PAC4 with regard to its latent applications as Cu(II) selective colorimetric and fluorescent sensor among the selected series of various cations such as Li(I), Na(I), K(I), Rb(I), Ba(II), Sr(II), Al(III), Fe(III), Cd(II), Co(II), Hg(II), Mn(II), Ni(II), Pb(II) and Zn(II) was examined by UV-visible and fluorescence emission spectroscopy in dichloromethane:acetonitrile (DCM:MeCN) solvent system. In addition, the process of complexation has been investigated through Job's plot and it has been observed that the complex between PAC4 and Cu(II) is formed in 1:1 stoichiometric ratio. The complex formation between PAC4 and Cu(II) has also been confirmed by FT-IR spectroscopy and thermal gravimetric analysis (TGA).