Selective Detection of Fe³⁺, F^–, and Cysteine by a Novel Triazole-Linked Decaamine Derivative of Pillar[5]arene and Its Metal Ion Complex in Water

Abstract

Appropriately functionalized pillar[n]arenes are elegant supramolecular hosts for ion and molecule sensing. A water-soluble decaamine derivative of pillar[5]arene (APA) bearing triazole and amide moieties is synthesized. The ion and molecular recognition properties of APA are studied by fluorescence, UV−visible, and 1 H nuclear magnetic resonance (NMR) spectroscopy. The APA selectively detects Fe 3+ among 11 studied ions, which are important in several biological processes. Moreover, the in situ prepared Fe 3+ complex of APA (FeAPA) exhibits the highest responsiveness toward F − (∼12-fold) among 11 anions and cysteine (∼120-fold) among the 20 naturally occurring amino acids by a fluorescence turn-on mechanism.

Ion recognition by 1,2,3‐triazole moieties synthesized via “click chemistry”

“…A representative image of gradual shifts in the nuclear magnetic resonance (NMR) spectrum of a 1,2,3‐triazole‐based probe on successive addition of metal ions, thereby confirming metal–ligand binding [ 91 ] …”

“…While largely used for structure elucidation, NMR spectroscopy, [88,89] sometimes in addition to UV-Vis or fluorescence spectroscopy, is also instigated for demonstrating metal-ligand binding through the upfield or downfield shifts resulting from the shielding or deshielding effects observed in the NMR spectra of a probe on the addition of metal ions, [90][91][92] as illustrated in Figure 7 [91] and Figure 8. [93] The technique is also used for other applications such as drug analysis, RNA study, and ensemble quantum computing.…”

“…[84] Joseph described amide and triazole containing pillar [5]arene derivative (Table 3a) that had a flexible binding core due to different functional moieties and exhibited 265-fold fluorescence quenching on Fe 3+ addition. [91] Li and co-workers reported polytriazoles (Table 3a) synthesized via copper-based ionic liquid as catalyst that selectively sensed Fe 3+ ions in addition to explosive detection and specific bioimaging. [183] Singh et al synthesized a CuAAC-mediated selective Fe 3+ sensor from 2,7-dihydroxynaphthalene and n-butyl azide (Table 3a) that exhibited threefold decrease in its emission intensity.…”

Pillar[n]arene Derivatives as Sensors for Amino Acids

“…Synthesis of triazole linked pillar [5]arene derivative, P20. [82] Scheme 14. Synthesis of quinolone derivative of pillar [5]arene, P21.…”

“…An Fe 3 + complex of a triazole linked decaamine derivative of pillar [5]arene, P20 detects L-Cys selectively among the twenty amino acids studied was demonstrated using fluorescence spectral techniques conducted in water. [82] The sensor molecule P20 was prepared by a four-step reaction in which propargyl derivative of pillar [5]arene (P20a) was reacted with ethylazidoacetate under click reaction conditions resulted in the formation of a triazole based pillar[n]arene derivative (P20b) in 59 % yield. The deca-substituted ester derivative of pillar[n]arene was treated with excess amount of hydrazine hydrate to form the sensor molecule P20 in 92 % yield (Scheme 13).…”