Lead and Mercury Sensing by Calixarene‐Based Fluoroionophores Bearing Two or Four Dansyl Fluorophores

Abstract

A detailed study on the photophysical and complexing properties of calixarenes bearing two and four dansyl derivatives (Calix-DANS2 and Calix-DANS4) in a CH3CN/H2O mixture (60:40 v/v) is reported. Calix-DANS2 shows a high selectivity towards Hg2+ over interfering cations (Na+, K+, Ca2+, Cu2+, Zn2+, Cd2+ and Pb2+) and a sensitivity in the 10(-7) mol L(-1) concentration range. The complexation of mercury ion induces a strong fluorescence quenching due to a well-defined electron transfer process from the fluorophore to the metal center. Calix-DANS4 exhibits an extremely high affinity for Pb2+ with a high selectivity over various competing ions. The unprecedented detection limit (4 microg L(-1)) is fully compatible with the level defined by the World Health Organisation. The affinity of Calix-DANS4 for Pb2+ can be rationalized by the activation of the inert pair of electrons on Pb2+. The number of fluorophores involved in the complexation can be determined from a careful time-resolved fluorescence characterization.

Calixarene-Based Receptors for Molecular Recognition

“…This review will only consider calix [4]arene, calix [6]arene, and calix [8]arene and especially their derivatives, which are initially derivatized at the lower or upper rim. …”

“…The side-on binding of the macrocycle to the metal complex, its low binding constant, and its inability to provide steric hindrance to attack of the metal complex by guanosine indicate that 11 may not be a suitable drug delivery vehicle for multinuclear anticancer drugs. Xue et al 59 have reported synthesis of amphoteric calix [8]arene 12 with a negatively charged upper rim and a positively charged lower rim based on water-soluble p-sulfonato-calix [8]arene. In view of the potential application of antibacterial drug loaded complexes formed by such calix [8]arenes as drug carriers or for hygiene paper products, they selected a hydrophobic antimicrobical drug of ciprofloxacin (CPF) as a model drug and investigated the pH-sensitive complexation of amphoteric calix [8]arenes in detail ( Figure 8).…”

“…Xue et al 59 have reported synthesis of amphoteric calix [8]arene 12 with a negatively charged upper rim and a positively charged lower rim based on water-soluble p-sulfonato-calix [8]arene. In view of the potential application of antibacterial drug loaded complexes formed by such calix [8]arenes as drug carriers or for hygiene paper products, they selected a hydrophobic antimicrobical drug of ciprofloxacin (CPF) as a model drug and investigated the pH-sensitive complexation of amphoteric calix [8]arenes in detail ( Figure 8). The pH-sensitive amphoteric calix [8]arenes exhibit not only a good hydrophobic drug loading capacity but also pH-triggered drug releasing behavior.…”

Synthesis of a Series of Novel Tetra-tert-butylcalix[4]arene Linked to 1,2,4-Triazole and 1,3,4-Oxadiazole Derivatives

“…Calix [4]arenes have been investigated for their biological proprieties; for example hydrophilic derivatives have shown interesting levels of activity against bacteria, cancerous cell, fungi, enveloped virus thrombosis, and fibrosis diseases. [8][9][10][11][12][13][14] 1,2,4-Triazole-5-thiones and 1,3,4-oxadiazole-5-thiones scaffolds are heterocyclic compounds containing five membered rings and their derivatives have been studied due to their diverse pharmacological proprieties, such as antibacterial and antifungal, [15][16][17][18][19][20][21][22] antimicrobial, [23][24][25] anti-inflammatory, 22,26 and antiviral activities. 27,28 Calix [4]arenes represent a third generation of supramolecular hosts after cyclodextrins and crown ethers, with unique three-dimensional structures.…”

Rapid colorimetric detection of Hg2+ ion by green silver nanoparticles synthesized using Dahlia pinnata leaf extract

“…Exposure to this heavy metal at even very low concentration (~1 μm/ml) may cause digestive disorders [26], kidney dysfunction [27] and various neurological disorders as well [28,29]. The sensors now available for detecting Hg 2+ are either based on organic compounds [30] and fluorophores [31] or functionalized nanorods [32]. However, the biosynthesized silver nanoparticles were rarely tested for their ability to detect Hg 2+ ions.…”