Pyridylthiazoles: highly luminescent heterocyclic compounds.
Absorption, fluorescence, and fluorescence excitation spectra of two substituted [(5-methyl-2-pyridine-2'-yl-1,3-thiazole-4-yl)oxy]acetic acid and its methyl ester (2,2'-pyridylthiazoles) are studied at various pH values in aqueous solution. The acid exhibits pKa(1)=2.10+/-0.07 and pKa(2)=3.45+/-0.03, whereas the ester pKa=1.93+/-0.03. The protonation site is the pyridyl-nitrogen. When protonated, the cisoid conformer is the most stable; however, the transoid conformer is more stable in the deprotonated form. Fluorescence quantum yields close to unity are found. Large Stokes shift values are explained by the shortening of the inter-ring bond in the excited state. These compounds may be useful for metal sensing and as laser dyes.
Grummt
Ulrich-W
UW
Institut für Physikalische Chemie der Friedrich-Schiller-Universität Jena, Helmholtzweg 4, D 07743 Jena, Germany. cug@uni-jena.de
Weiss
Dieter
D
Birckner
Eckhard
E
Beckert
R
R
D000085:Acetates / Q000138:chemical synthesis / Q000737:chemistry*; D006571:Heterocyclic Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D049449:Luminescence; D011789:Quantum Theory; D012680:Sensitivity and Specificity; D012996:Solutions / Q000737:chemistry; D013050:Spectrometry, Fluorescence / Q000379:methods; D013056:Spectrophotometry, Ultraviolet / Q000379:methods; D013844:Thiazoles / Q000138:chemical synthesis / Q000737:chemistry*; D014867:Water / Q000737:chemistry
C520327:5-methyl-2-pyridine-2'-yl-1,3-thiazole-4-yl-oxyacetic acid; D000085:Acetates; D006571:Heterocyclic Compounds; D012996:Solutions; D013844:Thiazoles; C520328:methyl 5-methyl-2-pyridine-2'-yl-1,3-thiazole-4-yl-oxyacetate; D014867:Water