Title: Synthesis of upper-rim allyl- and p-methoxyphenylazocalix[4]arenes and their efficiencies in chromogenic sensing of Hg2+ ion
Authors: Ho, I-Ting
Lee, Gene-Hsiang
Chung, Wen-Sheng
Department of Applied Chemistry
Issue Date: 30-Mar-2007
Abstract: A series of upper-rim p-allyl and p-methoxyphenylazocalix[4]arenes (6, 8, 9a, b, and 10a,b) were synthesized and shown to exhibit substantial color changes upon complexation with Hg2+ ion. Both the upper-rim p-allyl- and p-methoxyphenylazo groups on calix[4]arenes are proven to be key components in the recognition of Hg2+ ion. Job's plots revealed 1:1 binding stoichiometry for all these p-allyl- and p-arylazo-coupled calix[4]arenes with Hg2+ ions and Benesi-Hilderbrand plots were used for determination of their association constants. Our results also demonstrated that two p-methoxyphenylazo groups prefer to bind Hg2+ in a distal orientation rather than a proximal one, and if there are three p-methoxyphenylazo groups, the third flanking p-methoxyphenylazo group plays a role in disturbing the binding of the two distal diazo groups. Furthermore, it should be noted that triazocalix[4]arenes (6, 9a, and 9a) responded to all 14 metal ions without showing much preference among the eight transition-metal ions screened in this work (Cr3+, Ni2+, Cu2+, Ag+, Cd2+, Hg+, Hg2+, and Pb2+).
URI: http://dx.doi.org/10.1021/jo062280s
ISSN: 0022-3263
DOI: 10.1021/jo062280s
Volume: 72
Issue: 7
Begin Page: 2434
End Page: 2442
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