A novel Schiff base fluorescent sensor N,N0-bis(salicylidene)-2,6-bis(4-aminophenyl)-4-phenylpyridine (P3) was synthesized through condensation of 2,6-bis(4-aminophenyl)-4-phenylpyridine and 2- hydroxybenzaldehyde. The obtained results from fluorescence analysis revealed that by excess of Cr3þ to P3, a remarkable increase was observed in the fluorescent intensity of the Schiff base at 663 nm with the ratio of CH3CN/H2O (95/5%), even though the other cations would likely have no impact on the fluorescence intensity. The cause of this trend might be ascribed to the formation of a 1:1 stoichiometric P3-Cr3þ complex, confirmed by Job's plot, which is resulted in preventing the photo-induced electron transfer (PET) process. From fluorescence titration, the association constant Ka was gained 2.28 105 M1 and the limit of detection (LOD) was determined to be 1.3 107 M. Furthermore, the optimized structure together with the electronic spectra of the proposed complex was determined by DFT and TDDFT calculations
