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. 2021 Nov 12:9:766442.
doi: 10.3389/fchem.2021.766442. eCollection 2021.

A Novel Calix[4]Crown-Based 1,3,4-Oxadiazole as a Fluorescent Chemosensor for Copper(II) Ion Detection

Chun Sun  1 , Siyi Du  1 , Tianze Zhang  1 , Jie Han  1
Affiliations

A Novel Calix[4]Crown-Based 1,3,4-Oxadiazole as a Fluorescent Chemosensor for Copper(II) Ion Detection

Chun Sun et al. Front Chem. .

Abstract

The synthesis and characterization of a novel florescent chemosensor 1 with two different types of cationic binding sites have been reported in this work, which is a calix[4]crown derivative in 1,3-alternate conformation bearing two 2-phenyl-5-(4-dimethylaminopyenyl)-1,3,4-oxadiazole units. The recognition behaviors of 1 in dichloromethane/acetonitrile solution to alkali metal ions (Na+ and K+), alkaline earth metal ions (Mg2+ and Ca2+), and transition metal ions (Co2+, Ni2+, Zn2+, Cd2+, Cu2+, Mn2+, and Ag+) have been investigated by UV-Vis and fluorescence spectra. The fluorescence of 1 might be quenched selectively by Cu2+ due to the photo-induced electron transfer mechanism, and the quenched emission from 1 could be partly revived by the addition of Ca2+ or Mg2+; thus, the receptor 1 might be worked as an on-off switchable fluorescent chemosensor triggered by metal ion exchange.

Keywords: 1,3,4-oxadiazole; 1,3-alternate conformation; calix[4]crown; copper (II) detection; fluorescent chemosensor.

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Conflict of interest statement

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Figures

SCHEME 1
SCHEME 1
Synthetic route for 1, reagents, and conditions: (i) 1-iodopropane, K2CO3, CH3CN, reflux, 24 h; (ii) Br2, 0°C, 3 h; (iii) tetraethylene glycol ditosylate, Cs2CO3, CH3CN, reflux, 72 h; (iv) (1) CuCN, NMP, 180°C, 5 h; (2) FeCl3, 2 M HCl, 100°C, 1 h; (v) KOH, ethanol, reflux, 24 h; (vi) (1) SOCl2, toluene, reflux, 5 h; (2) 4-(dimethylamino)benzohydrazide, pyridine, r. t., 12 h; (vii) POCl3, reflux, 12 h.
FIGURE 1
FIGURE 1
X-ray molecular structure of 5.
FIGURE 2
FIGURE 2
UV-vis spectra of 1 (1 × 10−6 mol/L) upon addition of metal ions (10 equiv) in CH2Cl2/CH3CN (1,000:1, v/v).
FIGURE 3
FIGURE 3
Fluorescence spectra (λexc = 334 nm, Slit = 2.5) of 1 (1 × 10−6 mol/L) upon addition of metal ions (10 equiv) in CH2Cl2/CH3CN (1,000:1, v/v).
FIGURE 4
FIGURE 4
Fluorescence spectra (λexc = 334 nm, Slit = 2.5) of 1 (1 × 10−6 mol/L) and Cu2+ (10 equiv) upon addition of other metal ions (10 equiv) in CH2Cl2/CH3CN (1,000:1, v/v).
FIGURE 5
FIGURE 5
Plot of emission intensity versus the concentrations of Cu2+ ion (λem = 405 nm, λex = 334 nm).
FIGURE 6
FIGURE 6
The complexation of 1 with Cu2+ and Mg2+ ions.
FIGURE 7
FIGURE 7
Computational optimized molecular structures of 1 and 1·Mg 2+ .
See this image and copyright information in PMC

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