Synthesis of colorimetric sensors for isomeric dicarboxylate anions: selective discrimination between maleate and fumarate.
Four new colorimetric receptors (1-4) were synthesized and characterized. Upon addition of maleate to receptor in DMSO, the appearance of the solution of receptor 1 showed a color change from dark-blue to dark-red, which can be detected by the naked eye at parts per million. Similar experiments were repeated using receptors 2-4; the solution showed a distinct color change from blue to violet for receptor 2 and from blue-green to purple for both receptors 3 and 4, when they are formed as complexes with maleate. The striking color changes are thought to be due to the deprotonation of the thiourea moiety of the 4-nitronaphthyl chromophore. Whereas, in the addition of fumarate to receptors 1-4, the color of the solution changed from dark-blue to bright yellow for receptor and did not induce any color change for receptors 2-4. Thus, for a distinct color change, receptors 1-4 can act as optical chemosensors for recognition of maleate versus fumarate. Especially, only receptor 1 has a unique color change for the recognition of fumarate, accordingly it can be used for detection of the fumarate anion. In this research it was also found that the performance of the receptor is highly dependent on the substituent group on the phenyl ring; a stronger electron-withdrawing group resulted in a receptor with a higher binding constant with the maleate anion.
Tseng
Yu-Ping
YP
Department of Applied Chemistry, Providence University, 200 Chungchi Road, Sha-Lu, Taichung Hsien 433, Taiwan.
Tu
Guan-Min
GM
Lin
Chia-Hung
CH
Chang
Chi-Tong
CT
Lin
Chi-Yung
CY
Yen
Yao-Pin
YP
D000838:Anions / Q000737:chemistry*; D003124:Colorimetry; D003998:Dicarboxylic Acids / Q000737:chemistry*; D005650:Fumarates / Q000737:chemistry*; D006860:Hydrogen Bonding; D007536:Isomerism; D007700:Kinetics; D009682:Magnetic Resonance Spectroscopy; D008298:Maleates / Q000737:chemistry*; D011522:Protons; D013056:Spectrophotometry, Ultraviolet
D000838:Anions; D003998:Dicarboxylic Acids; D005650:Fumarates; D008298:Maleates; D011522:Protons; C032005:fumaric acid; C030272:maleic acid