Anthryl‐1,2,4‐oxadiazole‐Substituted Calix[4]arenes as Highly Selective Fluorescent Chemodosimeters for Fe³⁺

Abstract

Fluorescent chemosensors 1 and 2, with 1,2,4-oxadiazoles as the binding ligands and anthracene as the fluorophore, were synthesized through sequential 1,3-dipolar cycloaddition reactions of 25,27-dioxyacetonitrilecalix[4]arenes 8 and 11. The fluorescence of 1 was severely quenched by both Fe(3+) and Cu(2+) , whereas that of 2 was selectively quenched only by Fe(3+) . Control compound 4 was also selectively quenched by Fe(3+) , which implied the importance of anthryl-1,2,4-oxadiazole core; furthermore, it was shown to give various oxidation products such as oxanthrone 13, anthraquinone 14, and imidazolyl oxanthrone 15. In addition to product separation and identification, the fluorescent quenching mechanism of these 9-anthryl-1,2,4-oxadiazolyl derivatives by Fe(3+) is also discussed. Furthermore, it should be noted that the oxadiazole-substituted anthracene 4 and calix[4]arene 2 are Fe(3+) -selective fluorescent chemodosimeters without the interference by Cu(2+) .

Competition of Intra- and Intermolecular Forces in Anthraquinone and Its Selected Derivatives

“…In the current study, we present quantum-chemical results for 9,10-anthraquinone ( 1 ) [ 20 ] and its two derivatives (1,8-dihydroxy-9,10-anthraquinone ( 2 ) [ 21 ] and 1,8-dinitro-4,5-dihydroxy-anthraquinone ( 3 ) [ 22 ]), (see Figure 1 and Figure S1 ). The chemical composition of anthraquinone (rigid part consisting of three fused rings) makes the molecule an interesting object for structure modification based on various substituents.…”

Highly Selective Fluorimetric Turn‐Off Detection of Copper(II) by Two Different Mechanisms in Calix[4]arene‐Based Chemosensors and Chemodosimeters

“…TLC‐MS analysis of the solution of S3 plus excess Cu(ClO 4 ) 2 after an NH 4 Cl wash and filtration through a silica pad shows m/z 1177 consistent with the sodium ion of the calixdiquinone, S3‐Q 2 . Oxidative routes to calixdiquinones generally involve thallium or lead reagents and whilst Chung's Fe 3+ sensing by a 1,2,4‐oxadiazole‐substituted calixarene provides precedence for redox mediated, transition metal ion sensing promoting calix[4]diquinone generation, as far as we can tell this work represents the first isolation of a Cu(II) generated calix[4]diquinone.…”

“…[13] To understand the sensing mechanism a series of molecules related to S1 but each differing in one key structural feature have been studied: S2 incorporates a propyl spacer between the pyrene and isoxazole moieties whilst a two carbon linker separates the calix [4]arene lower rim and the heterocycle in S3, finally, the lower rim phenolic OH groups are fully substituted in S4, Figure 1. In a series of elegant papers Chung and coworkers report calixarene framed Cu(II) sensors related to S1-4 with β-amino α,β-unsaturated ketone, [14] amide [15] isoxazole [14,16] or 1,2,4-oxadiazole [17] as metal ion binding motifs, paired with naphthyl, anthryl or chloroanthryl reporting units. Chung's data suggests a Cu(II) detection mechanism sensitive to the calixarene substitution pattern, specifically, when there are unprotected phenolic groups, and where the large rim is unsubstituted a metal-ligand charge transfer band in the UV spectrum implicates a Cu(I)-phenoxy radical complex.…”

9-Anthraldehyde oxime: a synthetic tool for variable applications

“…The 9-anthracenenitrile oxide (8a), prepared according to the well-established methodology already reported, was allowed to react with the calix [4]arenes 32a, 32b to give the corresponding bis-3-(9-anthryl)-1,2,4-oxadiazolyl-5-methylcalix [4]arenes 33a and 33b in 43 and 53% yield, respectively (Scheme 17) [30]. These compounds were employed as chemosensors selective for Fe 3+ without interference by other metals and Cu 2+ in particular.…”