Selective colorimetric sensing of CN- by dihydropyrazol-3-ol derivative in CH3CN/H2O medium

作者：Ahmad Israr; Sharma Amit; Ghosh Tamal^*

来源：Supramolecular Chemistry, 2012, 24(4): 221-227.

DOI：10.1080/10610278.2011.643796

• colorimetric sensor
• cyclic alcohol
• charge transfer
• hydrogen bond
• selective cyanide ion sensing

The synthesis, characterisation and anion binding studies of 2-(2,4-dinitrophenyl)-3-ethoxy-5-methyl-3,4-dihydro-2H- pyrazol-3-ol (1) have been described. 1, bearing electron withdrawing 2,4-dinitophenyl group in its structure, recognises CN- 2 selectively in CH3CN/H2O (4:1, v/v) medium with a binding constant of 440M(-1) and visible colour change from yellow to red, whereas no colour change is observed in the presence of other anions such as F-, Cl-, Br-, I-, H2PO4-, AcO-, PhCOO-. Interestingly, in CH3CN, 1 is responsive not only to CN- but also to F- , H2PO4-, AcO- and PhCOO- 2 with a binding-induced visible colour change from yellow to reddish-brown. The strongest binding ability of 1 is observed with CN- in CH3CN, the binding constant being 1.34 x 10(5) M-1, whereas the binding constants of F- and oxyanions (H2PO4-, AcO- , PhCOO-) are found to be lower by one order or more in magnitude. H-1 NMR titrations of 1 are carried out with CN- and F-, which not only provide the evidence for the hydrogen-bonding interaction between the alcohol -OH of 1 and anions, but also offer some invaluable information about the structure of the sensor-anion complexes.

• 出版日期2012