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This content will become publicly available on October 1, 2026

Title: Chelating 5′-(p-hydroxyphenyl)pyridylthiazoles as ratiometric fluorescence probes for d10 metal ions
Three fluorescent 5’-(p-hydroxyphenyl)pyridylthiazoles (HPPT) with different chelating groups at the 4’ position were synthesized and evaluated for their ability to detect transition metal ions in acetonitrile and aqueous buffers, based on changes in fluorescence intensity and intramolecular charge transfer (ICT). Both 4’-O-picolyloxy-HPPT (Pic-HPPT) and 4’-O-(o-carboxypicolyl)-HPPT (CPic-HPPT) respond strongly to Zn(II), Cd(II), and Pb(II) in CH3CN with a bathochromic shift in emission up to 68 nm, whereas 4’-O-carboxymethyl-HPPT (CM-HPPT) is unresponsive. Only CPic-HPPT responds to d10 metal ions in aqueous phosphate buffered solution (PBS, pH 7.4), attributable to the added chelating power of the ortho-carboxylate. CPic-HPPT forms a 2:1 complex with Zn(II) and a 1:1 complex with Cd(II) and Pb(II) in CH3CN, whereas a 1:1 complex forms with Zn(II), Cd(II), and Hg(II) ions in PBS. X-ray structural analysis of 1:1 Pic-HPPT–metal ion complexes reveals a planar tridentate binding motif with Zn(II) but a nonplanar tridentate geometry with the larger Cd(II) ion. Fluorescence titration of CPic-HPPT in PBS with Zn(NO3)2 established sub-micromolar sensitivity with a limit of quantitation at 50 nM. These results show that CPic-HPPT has promise as a fluorescent probe for d10 metal ions in physiologically relevant media.  more » « less
Award ID(s):
2204206
PAR ID:
10638050
Author(s) / Creator(s):
; ; ;
Publisher / Repository:
Elsevier
Date Published:
Journal Name:
Tetrahedron Letters
Volume:
169
Issue:
C
ISSN:
0040-4039
Page Range / eLocation ID:
155743
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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