Novel synthesized antipyrine derivative based 'Naked eye' colorimetric chemosensors for Al 3+ and Cr 3+

New antipyrine Schiff bases 2,3-dimethyl-4-(3-oxo-1,3-diphenylpropylideneamino)-1-phenyl-1,2-dihydropyrazol-5-one ( AP1 ) and 2,3-dimethyl-4-(2-oxo-1,2-diphenylethylideneamino)-1-phenyl-1,2-dihydropyrazol-5-one ( AP2 ) have been synthesized by simple condensation method and investigated their metal recognition abilities. Different aspects of metal sensing phenomena were extensively studied and results indicated that Schiff base AP1 and AP2 exhibited selective colorimetric and fluorescent sensing behavior towards Al 3+ and Cr 3+ in methanol with high binding nature, which could be directly detected by the naked-eye. Stoichiometry of metal-ligand complexes were determined by job's plots titrations and further verified with HRMS data. Both sensors exhibited excellent fluorescent sensing behavior in acidic and neutral pH with low detection limits 0.49, 0.96 μM for AP1 + Al 3+ , AP1 + Cr 3+ and 0.73, 1.21 μM for AP2 + Al 3+ and AP2 + Cr 3+ , respectively.