Copper inorganic-organic hybrid coordination compound as a novel L-cysteine electrochemical sensor: Synthesis, characterization, spectroscopy and crystal structure

Abstract

Dinuclear coordination compound of Cu(II), namely, [Cu2(pydc)2(pz)(H2O)2] 2H2O, where pydc = pyridine-2,6-dicarboxylic acid (dipicolinic acid) and pz = pyrazine has been synthesized and characterized by elemental analysis, spectra (IR, UV-Vis), thermal (TG/DTG) analysis, magnetic measurements and single crystal X-ray diffraction. In the dimeric structure, the planar tridentate pyridine-2,6-dicarboxylic acid dianion coordinates to a Cu(II) ion in a meridional fashion and defines the basal plane of the complex. The fourth equatorial coordination site is then occupied by a pyrazine molecule that functions as a linear bidentate ligand bridging two Cu(II) complexes to form a dimer. The axial positions of each Cu(II) complex are occupied by one water molecule to form a distorted square pyramidal geometry. The complicated hydrogen bonding network accompanied with C-O ⋯π and C-H ⋯π stacking interactions assemble the crystal structure of 1 into a fascinating supramolecular architecture. Electrochemical behavior of [Cu2(pydc)2(pz)(H2O)2] (Cu-PDAP) on the surface of carbon nanotube (CNTs) glassy carbon electrode (GCE) is described. Oxidation of cysteine on the surface of modified electrode was investigated with cyclic voltammetry and electrochemical impedance spectroscopy (EIS). The results show that the Cu-PDAP/CNTs film displays excellent electrochemical catalytic activities towards L-cysteine oxidation.