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

Abstract

Isoxazolo‐pyrene tethered calix[4]arenes selectively detect copper(II) ions without interference from related perchlorate ions. The fluorescence emission of the probes, synthesised by nitrile oxide alkyne cycloaddition, and characterised by spectroscopic and crystallographic data, is rapidly reduced by Cu(II) ions. Detection limits are in the micromolar or sub‐micromolar range (0.3–3.6 μM) based on a 1 : 1 sensor:analyte interaction. Voltammetric behaviour and 1H NMR data provide new insights into the sensing mechanism which is dependent on the calixarene substitution pattern. When the calixarene lower rim is fully substituted, Cu(II) detection occurs through a traditional chelation mechanism. In contrast, for calixarenes 1,3‐disubstituted on the lower rim, detection takes place through a chemodosimetric redox reaction. The isolation of a calix[4]diquinone from the reaction with excess Cu(ClO4)2 provides confirmation that the sensor–analyte interaction culminates in irreversible sensor oxidation.

Highly Sensitive and Selective Fluorescent Probes for Cu(II) Detection Based on Calix[4]arene-Oxacyclophane Architectures

“…It is worth mentioning that in several previous works using calix [4]arene-based ionophores, particularly those relying in dansyl groups [49] sensitivities for Cu(II) and Pb(II) are of the same order of magnitude, whereas for Hg(II) the affinity was in general even higher, overall making the attained selectivity for Cu(II) in these systems rather poor. In other works [50], a good selectivity was achieved for Cu(II) in comparison, for instance, with Pb(II) or Hg(II), although in a lower sensitivity when compared to polymer 5.…”

“…For non-polymeric probes, a calix [4]arene containing two pyrenyl amine groups showed a K sv of 1.49 × 10 4 M −1 [48], while a series of calixarene receptors with appended dansyl groups display association constants ranging from 1.45 × 10 3 − 6.31 × 10 4 M −1 [49]. Pyrenyl-isoxazolo-tethered calix [4]arenes also display significant responses to Cu(II) with K a in the range 6.00 × 10 3 − 4.71 × 10 4 M −1 [50]. When considering conjugated polymers, either fluorene-alt-phenylene and phenyleneethynylene-alt-thienyleneethynylene type polymers, containing attached, respectively, N-cyclohexyl carbamates (K sv = 1.10 × 10 4 M −1 ) [51] and tolylterpyridyl (K sv = 2.01 × 10 5 M −1 ) [52] groups as recognition elements, have been used for Cu(II) detection.…”

A highly selective chromogenic and fluorogenic chemodosimeter for dual detection of Cu2+ based on a redox-active calix[4]arene with isoxazolylchloroanthracene

“…While some sensing systems do not involve counterion participation, there is precedence for an anion dependence on cation sensing across a range of mechanisms. 35 It is suggested that anion effects can be due to their pH 40 and in another case, the Cu 2+ detection by means of oxidation behavior toward a ferrocene unit is reported to be profoundly influenced by the counterion. 41 The apparent difference between the lower-rim propyl substituted 2 (no-response in UV/vis or fluorescence) and the unsubstituted analogue 1 (∼88% fluorescence quenching) to 10 equivalents of Cu(ClO 4 ) 2 can be understood by considering the sensing mechanism shown in Scheme 2.…”

“…24 Recently, Heaney and co-workers also reported the synthesis of p-t-butylcalix [4]arene with lower-rim 1,3-bisisoxazolylpyrene units showing high selectivity toward Cu 2+ ions in CH 3 CN with fluorescence turn-off. 34,35 However, there has been no report on the synthesis of lower-rim isoxazole-functionalized calix [4]arenes with both chromogenic and fluorogenic properties for Cu 2+ sensing.…”

Colorimetric chemosensor for Cu(II) from electrospun nanofibrous mat mixed with 5‐methoxy‐salicylaldehyde azine

“…However, most of these studies were conducted in the solution phase. [17][18][19][20][21] Recently, research using chemosensing materials mixed with polymer-based solid supports was initiated due to an anticipated enhanced stability, the convenience of on-site analysis, easily usable platforms, ease of disposal and reversibility. [22][23][24][25][26][27][28][29] Practically, the solid nanomaterial capacity for adsorbing metal ions can establish the sensitivity and selectivity of the probes.…”