A non-toxic, hemocompatible, fluorescent probe as cobalt(II) based complex [Co(PS)4](ClO4)2 (1) (PS: N-pyridylsalicylaldimine) was successfully synthesized and characterised by single crystal X-ray diffraction studies. The structural analysis revealed that 1 exhibits intramolecular π–π interaction. The recognition ability of 1 towards various amino acids and proteins were studied by UV-vis and fluorescence spectroscopy. The titled complex selectively sense the Trp by reducing its internal fluorescence quenching. It also sense BSA with a detection limit of 56 nM. The binding constant of 1 was analysed by Hill's equation and it was found that it binds to Trp and BSA in the order of 103 and 104 respectively.
