Sensors based on curcumin borondifluoride for naked-eye-detection of cyanide

Abstract

Novel curcumin derivatives containing BF₂-incorporated curcumin, BF₂-CurOH, BF₂-CurOMe, BF₂-CurmonoTs and BF₂-CurdiTs have been synthesized. The photophysical properties of all BF₂-curcumin derivative revealed that electron donating modified on aromatic ring (BF₂-CurOMe) induced the bathochromic shift of the absorption and emission spectra. In contrast, the electron-withdrawing modified on aromatic ring resulted in the hypsochromic shift in both absorptions and emissions. The quantum yields of BF₂-CurOH, BF₂-CurOMe, BF₂-CurmonoTs and BF₂-CurdiTs in dichloromethane were 0.62, 0.61, 0.22 and 0.48, respectively. Interestingly, BF₂-incoorporated curcumin derivatives of BF₂-CurOH and BF₂-CurOMe exhibited solvent-dependent. The solvent dependent maximum absorption band of both compounds were analyzed using Kamlet-Taft relationship, the result showed that BF₂-CurOH and BF₂-CurOMe behaved the positive solvatochromism. Concerning on the anion sensing, BF₂-CurOH have excellent sensitivity and selectivity toward cyanide ion over curcumin. This phenomenon was subjected to deprotonation of hydroxyl group of BF₂-CurOH and curcumin. The negative charge on oxygen atom which can delocalize through π-conjugated bond. The deprotonation abilities by CN- to both compounds measured by UV-visible titration and fluorometric titration exhibited the log β values of 8.8 and 7.7 for BF₂-CurOH and curcumin, respectively. Interestingly, the effect of foreign anions toward cyanide detection for BF₂-CurOH was studied and showed that no effect on the determination of CN̄ except AcŌ, H₂PO₄̄ and F̄ while all anions have an effect for cyanide detection of curcumin in aqueous solution. Furthermore, the detection limit of CN̄ is 9.33 and 0.14 µM for curcumin and BF₂-CurOH, respectively