A highly selective and sensitive chemosensor for l -tryptophan by employing a Schiff based Cu( ii ) complex

A new Cu( ii ) complex C 40 H 38 N 4 CuO 2 ( 1 ) was synthesized and characterized by elemental analysis, mass spectrometry and also authenticated by single crystal X-ray studies. Structural analysis of 1 reveals the distorted square planar geometry around the Cu( ii ) centre and the presence of C–H⋯O and N–H⋯π hydrogen bonding interactions. The sensing behaviour of 1 towards l -tryptophan ( l -Trp) was identified by UV-vis spectroscopic and cyclic voltammetry experiments. In the UV titration of 1 with l -Trp, four distinct isosbestic points were observed. Furthermore, on modifying the surface of the glassy carbon electrode (GCE) by 1 ( 1-GCE ) the oxidation potential of l -Trp at +0.32 V is revealed, which is considerably lower than the values previously reported for other electrodes. Additionally, the 1-GCE can detect l -Trp with a noteworthy detection limit (185 nM), sensitivity (3.156 μA μM −1 cm −2 ) and with distinguished selectivity in the presence of various other amino acids. The 1-GCE also displays excellent reproducibility, repeatability and long term stability. Finally, electrochemical impedance spectroscopy (EIS) investigations were carried out to gauge the effects of modification with 1 on the characteristics of the GCE. Moreover, the molecular docking study of 1 with various proteins reveals the π–π stacking interaction with l -Trp.