1：Experimental Design and Method Selection:

The study involved synthesizing a novel cobalt phthalocyanine complex with imine substituents, characterizing it using various spectroscopic and analytical techniques, and immobilizing it on a glassy carbon electrode for electrochemical sensing of L-cysteine. Methods included cyclic voltammetry, amperometry, and impedance spectroscopy.

2：Sample Selection and Data Sources:

The complex was synthesized from precursors like 4-nitrophthalonitrile and p-bromoaniline. L-cysteine solutions were prepared in phosphate buffer (pH 7.4) for electrochemical measurements.

3：4) for electrochemical measurements. List of Experimental Equipment and Materials:

3. List of Experimental Equipment and Materials: Equipment included Vario EL III CHNS elemental analyzer, Ocean optics spectrometer, FTIR Perkin Elmer Spectrum-Two spectrophotometer, Bruker D8 Advance X-ray diffractometer, STA6000 thermal analyzer, 500 MHz Varian NMR instrument, Agilent 6100 GC/MS, CHI620E electrochemical analyzer, and a three-electrode cell with glassy carbon, Ag/AgCl, and platinum electrodes. Materials included cobalt(II) chloride, 4-nitrophthalonitrile, DBU, p-bromoaniline, sodium hydroxide, salicylaldehyde, potassium carbonate, L-cysteine, potassium ferrocyanide, TBAP, n-pentanol, methanol, ethanol, acetone, n-hexane, DMF, DMSO, hydrochloric acid, sulphuric acid, and nafion binder.

4：Experimental Procedures and Operational Workflow:

Synthesis involved refluxing precursors, purification, and characterization. Electrode modification was done by drop-casting the complex ink on GCE. Electrochemical experiments were performed in N2 atmosphere with cyclic voltammetry, amperometry, and impedance measurements for L-cysteine detection.

5：Data Analysis Methods:

Data were analyzed using linear regression for calibration curves, equivalent circuit fitting for impedance, and standard formulas for capacitance and surface coverage calculations.