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Amidofluorene-appended lower rim 1,3-diconjugate of calix[4]arene: synthesis, characterization and highly selective sensor for Cu 2+

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ABSTRACT

Llll: Functionalization of calix[4]arene with amidofluorene moieties at the lower rim led to formation of the 1,3-diconjugate of calix[4]arene as a novel fluorescent chemosensor for Cu2+. The receptor molecule exhibited a pronounced selectivity towards Cu2+ over other mono and divalent ions. The formation of the complex between and Cu2+ was evaluated by absorption, fluorescence and 1H NMR spectroscopy. The sensor showed a remarkable color change from colorless to purple and a fluorescence quenching only upon interaction with Cu2+. The 1:1 stoichiometry of the obtained complex has been determined by Job’s plot. The association constant determined by fluorescence titration was found to be 1.8 × 106 M−1. The sensor showed a linear response toward Cu2+ in the concentration range from 1 to 10 µM with a detection limit of 9.6 × 10−8 M.

No MeSH data available.


1 H NMR (400 MHz, CD3CN) spectra of L upon addition of (a) 0.0 equiv, (b) 0.2 equiv, (c) 0.4 equiv, (d) 0.6 equiv, (e) 0.8 equiv, (f) 1.0 equiv, (g) 1.2 equiv and (h) 1.5 equiv of Cu2+.
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Figure 7: 1 H NMR (400 MHz, CD3CN) spectra of L upon addition of (a) 0.0 equiv, (b) 0.2 equiv, (c) 0.4 equiv, (d) 0.6 equiv, (e) 0.8 equiv, (f) 1.0 equiv, (g) 1.2 equiv and (h) 1.5 equiv of Cu2+.

Mentions: In order to understand the mode of complexation of L with Cu2+, 1H NMR titrations were carried out (Fig. 7). Upon the initial addition of Cu2+ into the CD3CN solution of L, signals related to OH phenolic groups (Hb) and amidic protons (Ha) were first broadened and then finally disappeared. Furthermore, the signals of Ar–CH2 (Hd, He) and –O–CH2 (Hf) porotons, which are close to the binding site of receptor L were affected and downfield shifted by the complexation of L with Cu2+. A detailed analysis of the 1H NMR spectra reveals the significant changes of almost all the other proton signals in the ligand. For instance, the peak of aromatic ring hydrogen atoms (Hc, resonated at 7.35 ppm) was converted to two distinct peaks at 7.20 and 6.95 ppm (Hc1, Hc2). In addition, signals belonging to the fluorene moieties and tert-butyl groups, which are quite far away from binding site, were also affected by complex formation. For example, the peaks of the tert-butyl groups of receptor L resonated at 1.29 (Hh1) and 1.22 ppm (Hh2) turned to one signal at 1.20 ppm during the titration.


Amidofluorene-appended lower rim 1,3-diconjugate of calix[4]arene: synthesis, characterization and highly selective sensor for Cu 2+
1 H NMR (400 MHz, CD3CN) spectra of L upon addition of (a) 0.0 equiv, (b) 0.2 equiv, (c) 0.4 equiv, (d) 0.6 equiv, (e) 0.8 equiv, (f) 1.0 equiv, (g) 1.2 equiv and (h) 1.5 equiv of Cu2+.
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Related In: Results  -  Collection

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Figure 7: 1 H NMR (400 MHz, CD3CN) spectra of L upon addition of (a) 0.0 equiv, (b) 0.2 equiv, (c) 0.4 equiv, (d) 0.6 equiv, (e) 0.8 equiv, (f) 1.0 equiv, (g) 1.2 equiv and (h) 1.5 equiv of Cu2+.
Mentions: In order to understand the mode of complexation of L with Cu2+, 1H NMR titrations were carried out (Fig. 7). Upon the initial addition of Cu2+ into the CD3CN solution of L, signals related to OH phenolic groups (Hb) and amidic protons (Ha) were first broadened and then finally disappeared. Furthermore, the signals of Ar–CH2 (Hd, He) and –O–CH2 (Hf) porotons, which are close to the binding site of receptor L were affected and downfield shifted by the complexation of L with Cu2+. A detailed analysis of the 1H NMR spectra reveals the significant changes of almost all the other proton signals in the ligand. For instance, the peak of aromatic ring hydrogen atoms (Hc, resonated at 7.35 ppm) was converted to two distinct peaks at 7.20 and 6.95 ppm (Hc1, Hc2). In addition, signals belonging to the fluorene moieties and tert-butyl groups, which are quite far away from binding site, were also affected by complex formation. For example, the peaks of the tert-butyl groups of receptor L resonated at 1.29 (Hh1) and 1.22 ppm (Hh2) turned to one signal at 1.20 ppm during the titration.

View Article: PubMed Central - HTML - PubMed

ABSTRACT

Llll: Functionalization of calix[4]arene with amidofluorene moieties at the lower rim led to formation of the 1,3-diconjugate of calix[4]arene as a novel fluorescent chemosensor for Cu2+. The receptor molecule exhibited a pronounced selectivity towards Cu2+ over other mono and divalent ions. The formation of the complex between and Cu2+ was evaluated by absorption, fluorescence and 1H NMR spectroscopy. The sensor showed a remarkable color change from colorless to purple and a fluorescence quenching only upon interaction with Cu2+. The 1:1 stoichiometry of the obtained complex has been determined by Job’s plot. The association constant determined by fluorescence titration was found to be 1.8 × 106 M−1. The sensor showed a linear response toward Cu2+ in the concentration range from 1 to 10 µM with a detection limit of 9.6 × 10−8 M.

No MeSH data available.