Quinoxaline-calix[4]pyrrole conjugates as tunable colorimetric receptor models for anions

ORGN 698

Chang-Hee Lee, chhlee@kangwon.ac.kr and Min-Soo Kim. Department of Chemistry, Kangwon National University, Hyo Ja 2 Dong 192-1, Chun-Cheon, 200-701, South Korea
Calix[4]pyrroles bearing diametrically crossing dipyrrolylquinoxaline moiety have been synthesized and fully characterized. Since the chromogenic properties of quinoxalines and anion-binding properties of calix[4]pyrroles have been well documented, we tried to utilize both properties in one molecule. The synthesis was accomplished by utilizing nucleophilic substitution of alkyl halides with pyrrole (as C-nucleophile). The receptors bearing different functional groups at the quinoxaline moiety were also synthesized and the colorimetric responses were studied. The chromogenic response of the quinoxaline moiety was studied systematically with spectroscopic means. Anion binding properties of the synthesized host molecules studied by proton NMR, UV-vis and isothermal titration calorimetry (ITC) indicated that electron-withdrawing group on the quinoxaline show enhanced colorimetric responses. The detailed studies for the colorimetric responses and for the binding affinity will be discussed.