On-off switchable binuclear chemosensor based on thiacalix[4]crown armed with pyrene moieties

A new fluorescent “on–off” switchable chemosensor 2 based on a thiacalix[4] arene with a 1,3‐alternate conformation and two different types of cation binding sites has been synthesized. Two pyrene moieties linked to a cation recognition unit composed of two imine groups form a strong excimer in solution. Of the metal ions tested, the fluorescence of 2 was strongly quenched by Hg²⁺, Pb²⁺ and Cu²⁺ ions. The fluorescence was revived by the addition of only K⁺ to the Cu²⁺ ligand complex. Thus, metal‐ion exchange triggers an “on–off” switchable fluorescent chemosensor

Molecular trafficking based on latch circuit

A new fluorescent chemosensor 3 based on calix[4]arene of partial cone conformation possessing dansyl moieties has been synthesized. The chemosensor demonstrates selective optical recognition of Hg2+ ions in mixed aqueous media and mimics the operation of a traffic signal based on the R–S Latch Logic circuit with pH, Hg2+ and Cl−/Br−/I− as chemical inputs

Regulation of metal ion recognition by allosteric effects in thiacalix[4]crown based receptors

Three new ditopic receptors 3a–c based on thiacalix[4]arene of 1,3 alternate conformation possessing two different complexation sites have been designed and synthesized for both soft and hard metal ions. The imino nitrogens bind soft metal ion (Ag+/Pb2+/Cu2+) and the crown moiety binds K+ ion. The preliminary investigations show that 3a–c behave as ditopic receptors for Ag+/K+, Pb2+/K+, and Cu2+/K+ ions, respectively. In all the three receptors it was observed that the formation of 3a·Ag+/3b·Pb2+/3c·Cu2+ complex triggers the decomplexation of K+ ion from crown moiety and acts as a gateway, which regulates the binding of alkali metal to crown moiety. Thus, allosteric binding between metal ions ‘switch off’ the recognition ability of crown ether ring

Ratiometric sensing of Hg²⁺ based on the calix[4]arene of partial coneconformation possessing a dansyl moiety

A new fluorescent chemosensor based on the calix[4]arene of partial cone conformation possessing a dansyl moiety has been synthesized. The chemosensor demonstrates selective optical recognition of Hg2+ and Cu2+ in two contrasting modes. The receptor exhibited ratiometric sensing of Hg2+ and “ON−OFF” type of fluorescence behavior in the presence of Cu2+. The compound behaves as a fluorescent molecular switch upon chemical inputs of Hg2+ and Cu2+ ions

Ratiometry of monomer/excimer emissions of dipyrenyl thiacalix[4]arene for Cu²⁺ detection: A potential Cu²⁺ and K⁺ switched INHIBIT logic gate with NOT and YES logic functions

A new thiacalix[4]arene derivative 2 of 1,3-alternate conformation possessing two pyrene groups has been synthesized and examined for its cation recognition abilities towards different cations such as lithium, sodium, potassium, nickel, zinc, cadmium, silver, mercury, lead and copper by fluorescence spectroscopy. In CH₃CN/CH₂Cl₂ (1:1), the presence of Cu(II) induces the formation of a 1:2 ligand/metal complex, which exhibits increasing monomer emission at 376 nm at the expense of the fluorescent excimer emission of 2 centered at 476 nm. In the presence of K⁺, the intensity of the excimer emission increases along with the formation of a new blue shifted band at 435 nm which corresponds to a static dimer. The compound behaves as a fluorescent molecular switch upon chemical input of Cu²⁺ and K⁺

Switching and fluorescence signal amplification with metal ions in allosteric systems based on 1, 3-alternate thiacalix[4]crown

New thiacalix[4]crown derivatives 4 and 5 of 1,3-alternate conformation possessing anthracene and quinoline moieties respectively were synthesised and examined for their cation recognition abilities toward different cations by fluorescence spectroscopy. Selective optical recognition with fluorescence amplification was observed for Fe³⁺/K⁺ and Hg²⁺/K⁺ in chemosensors 4 and 5 respectively. Further it was observed that the formation of 4·Fe³⁺ complex triggers the decomplexation of K⁺ ion. Similar allosteric behaviour between Hg²⁺ and K⁺ was observed in chemosensor 5

Bifunctional fluorescent thiacalix[4]arene based chemosensor for Cu²⁺ and F⁻ ions

A new thiacalix[4]arene based fluorescent sensor bearing two dansyl groups has been synthesized in cone conformation. In CH3CN:CH2Cl2 (1:1), the presence of Cu (II) induces the formation of a 1:1 metal:ligand complex, which exhibits increasing emission at 433 nm at the expense of the fluorescent emission of 1 centered at 504 nm. The detection limit of the sensor for Cu2+ is 2×10−7 mol L−1. For anion sensing, 1 shows a high selectivity for fluoride ions over other anions tested

Hetero-oligophenylene-based AIEE material as a multiple probe for biomolecules and metal ions to construct logic circuits: Application in bioelectronics and chemionics

New hetero‐oligophenylene derivative (2) was synthesized which exhibits aggregation‐induced emission enhancement (AIEE) in H2O/THF (80:20). The aggregates serve as a biological probe for three different proteins, that is bovine serum albumin (BSA), cytochrome c, and lysozyme, and DNA in contrasting modes. Further, among 29 metal ions tested, the contrasting fluorescence behavior of aggregates of 2 is observed with only Pb2+ and Pd2+ ions. Multiple output logic circuits based upon the fluorescence behavior between BSA and cytochrome c and between Pb2+ and Pd2+ ions are constructed

Chromogenic sensing of Cu(II) by imino linked thiacalix[4]arene in mixed aqueous environment

Thiacalix[4]arene based imino receptors 4–5 carrying azophenol appendage have been synthesized and studied for their binding abilities towards different metal ions (Li+, Na+, K+, Cd2+, Ni2+, Cu2+, Zn2+, Ag+, Pb2+ and Hg2+). Receptor 4 showed selective chromogenic sensing for Cu2+ ions in mixed aqueous conditions (THF:H2O, 9:1 v/v)