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1,3‐Alternate Calix[4]arene as a Homobinuclear Ditopic Fluorescent Chemosensor for Ag + Ions
Author(s) -
Ho ITing,
Haung KuanChang,
Chung WenSheng
Publication year - 2011
Publication title -
chemistry – an asian journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.18
H-Index - 106
eISSN - 1861-471X
pISSN - 1861-4728
DOI - 10.1002/asia.201100023
Subject(s) - fluorescence , calixarene , ion , chemistry , organic chemistry , molecule , physics , optics
A novel 1,3‐alternate calix‐[4]arene L , containing two different cationic binding sites of bis‐triazoles and bis‐enaminone groups, was synthesized and shown to be a homobinuclear ditopic fluorescent chemosensor for Ag + ions. The fluorescence intensity of L was selectively enhanced by binding with Ag + ions in methanol/chloroform (49:1, v/v) cosolvent. In the presence of most competing metal ions, L retains its selectivity toward Ag + ion. The binding constants K 1 and K 2 of the successive complexation of L with the first and second Ag + ions were calculated to be 4.46×10 3 and 9.20×10 4 M −1 , respectively. The higher K 2 value revealed that a positive allosteric effect participated in the complexation of L with the second equivalent of Ag + . Based on 1 H NMR titration results, we inferred that the two distal bis‐enaminone and bis‐triazole groups on L cooperatively coordinated to Ag + ions with the help of cation–π interactions from the phenoxy rings. Furthermore, the ESI‐MS spectrometry clearly proved the formation of the homobinuclear complex L ⋅(Ag + ) 2 , because a base peak at m / z of 750.1701 was detected and its isotope pattern was in excellent agreement with the calculated one.