Synthesis and evaluation of a novel fluorescent sensor based on hexahomotrioxacalix[3]arene for Zn2+ and Cd2+

Fluorescent homooxacalixarenes: recent applications in supramolecular systems

This review covers recent advances (from 2006 to date) in supramolecular systems based on fluorescent homooxacalixarenes, namely hexahomotrioxacalix[3]arenes, dihomooxacalix[4]arenes and tetrahomodioxacalix[4]arenes, focusing on fluorescence sensing using their intrinsic fluorescence (built-in mesitol-like groups) or the extrinsic fluorescence of organic fluorophores, either covalently linked to the calixarenes or forming supramolecular complexes with them. Sensing applications of ions, ion pairs and neutral molecules are discussed, as well as the potential measurement of temperature based on thermally activated delayed fluorescence.

Functionalized Calixarenes as Promising Antibacterial Drugs to Face Antimicrobial Resistance

Since the discovery of polyphenolic resins 150 years ago, the study of polymeric compounds named calix[n]arene has continued to progress, and those skilled in the art perfectly know now how to modulate this phenolic ring. Consequently, calix[n]arenes are now used in a large range of applications and notably in therapeutic fields. In particular, the calix[4]arene exhibits multiple possibilities for regioselective polyfunctionalization on both of its rims and offers researchers the possibility of precisely tuning the geometry of their structures. Thus, in the crucial research of new antibacterial active ingredients, the design of calixarenes finds its place perfectly. This review provides an overview of the work carried out in this aim towards the development of intrinsically active prodrogues or metallic calixarene complexes. Out of all the work of the community, there are some excellent activities emerging that could potentially place these original structures in a very good position for the development of new active ingredients.

Argentivorous Molecules with Chromophores in Side Arms: Silver Ion-Induced Turn On and Turn Off of Fluorescence

The synthesis of argentivorous molecules (L¹ and L²) having two chromophores (4-(anthracen-9-yl)benzyl or 4-(pyren-1-yl)benzyl groups) and two benzyl groups and the fluorescence properties of their silver complexes in a solution and the solid state are reported. A crystallographic approach for the Ag⁺ complexes with L¹ and L² revealed that the observed fluorescence changes stem from the excimer formation and extinction of fluorescent. Furthermore, binding stabilities of L¹ and L² toward Ag⁺ ions were estimated by the Ag⁺-induced UV-vis and PL spectral changes.

Recognition of silver cations by multifarene[2,2] chemosensors with unexpected fluorescence response

Fluorescent chemosensors based on a new macrocyclic compound, multifarene[2,2], with modification by triazole-linked pyrene or anthracene were synthesized. These macrocyclic sensors exhibited high affinity and selectivity toward Ag⁺ over other metal ions, with ratiometric or enhanced response of their fluorescence emissions depending upon the substituent species for coordination to Ag⁺, and an unexpected response to a concentration threshold of the metal cations was discovered. The experimental evidences of fluorescence spectra, ¹H NMR titration, IR spectra, and high-resolution mass spectra suggested the coordination behaviors of the sensors with Ag⁺, that is, the 1:1 complexes were formed with moderate association constants of about 10⁵ L·mol^-1, and the sulfur atoms on macrocyclic ligand should affinite to the metal cations. Energy-minimized structures and frontier orbitals were estimated by quantum chemical calculations with a view to rationalizing the fluorescence response of the multifarene[2,2] sensors upon binding to Ag⁺.

A novel and fast responsive turn-on fluorescent probe for the highly selective detection of Cd2+ based on photo-induced electron transfer

A novel, highly sensitive and fast responsive turn-on fluorescence probe ADMPA for Cd²⁺ was successfully developed based on 2,9-dimethyl-1,10-phenanthroline and o-aminophenol.

A Hexahomotrioxacalix[3]arene-Based Ditopic Receptor for Alkylammonium Ions Controlled by Ag⁺ Ions

A receptor cone-1 based on a hexahomotrioxacalix[3]arene bearing three pyridyl groups was successfully synthesized, which has a C₃-symmetric conformation and is capable of binding alkylammonium and metal ions simultaneously in a cooperative fashion. It can bind alkylammonium ions through the π-cavity formed by three aryl rings. This behaviour is consistent with the cone-in/cone-out conformational rearrangement needed to reorganize the cavity for endo-complexation. As a C₃-symmetrical pyridyl-substituted calixarene, receptor cone-1 can also bind an Ag⁺ ion, and the nitrogen atoms are turned towards the inside of the cavity and interact with Ag⁺. After complexation of tris(2-pyridylamide) derivative receptor cone-1 with Ag⁺, the original C₃-symmetry was retained and higher complexation selectivity for n-BuNH₃⁺ versus t-BuNH₃⁺ was observed. Thus, it is believed that this receptor will have a role to play in the sensing, detection, and recognition of Ag⁺ and n-BuNH₃⁺ ions.

A fluorescence-enhanced chemosensor based on multifarene[2,2] and its recognition of metal cations

A selective and sensitive fluorescent chemosensor based on an anthracene-functionalized triazole-linked multifarene[2,2] was successfully synthesized and investigated with regard to the recognition of metal ions.

2,3-Ethylene-bridged dihomooxacalix[4]arenes: synthesis, X-ray crystal structures and highly selective binding properties with anions

Three novel 2,3-ethylene-bridged p-tert-butyldihomooxacalix[4]arenes 3a–3c were selectively synthesized by direct O-alkylation of p-tert-butyldihomooxacalix[4]arene 1 with excess of 1,2-dibromoethane in controlled basic systems.