Aminobenzopyranoxanthene based salicylhydrazone probe for colorimetric detection of Cu2+

A new colorimetric probe aminobenzopyranoxanthene salicylhydrazone (ABPX-Sal) has been synthesized by condensation of salicylaldehyde with aminobenzopyranoxanthene hydrazide (ABPX-hy). Owing to its spirohydrazone structure, this probe showed a significant absorption enhancement at 419 ​nm in the presence of Cu²⁺, and the color changed from colorless to yellow. There was a good linear relationship between the absorption intensity of ABPX-Sal and the amount of Cu²⁺ (R² = ​0.9928), and the detection limit was calculated to be 0.912 ​μM. The binding mode between ABPX-Sal and Cu²⁺ was 1:2, which was proved by ESI-MS. The sensing mechanism was revealed to be a spiro-ring enacted coordination process by DFT calculation. The desired level of selectivity, sensitivity (within 30 ​s), and reusability made this probe very practical in acidic samples.