Electrochemical Detection of 4‐Chlorophenol Using Glassy Carbon Electrodes Modified with Thulium Double‐Decker Phthalocyanine Salts

This paper presents newly developed electrochemical sensors based on green and blue lanthanide double‐decker phthalocyanines (LnPc 2 ), with the green LnPc 2 derivative referred to as 2 a while the blue counterpart is designated 2 b . The modified glassy carbon electrode ( GCE ) based on the blue LnPc 2 complex is referred to as 2 b‐GCE while that which is based on the green LnPc 2 complex is named 2 a‐GCE . The oxidation of 4‐chlorophenol is extensively investigated and found to differ from one modified electrode to the next. Interestingly, the electrode modified with blue LnPc 2 complex ( 2 b‐GCE ) showed lower peak potential 0.88 V vs Ag|AgCl and higher catalytic current of 593 μA compared to that based on the green LnPc 2 counterpart ( 2 b‐GCE ) which exhibited ∼ 1.05 V vs Ag|AgCl and 65 μA, respectively. Remarkable differences in Tafel slopes were also found to be complimented by high rate constants in the order: 2 b‐GCE > 2 a‐GCE . The lowest limit of detection (LOD) was found for 2 b‐GCE at 4.16 ×10 −8  M in comparison to that for 2 a‐GCE at 6.14 ×10 −6  M. When investigating the electrochemical behavior, it was found that the first one‐electron oxidation minus the first one‐electron reduction differences were very low at 0.36 V and 0.55 V vs Ag|AgCl for 2 b and 2 a , respectively. Such values are comparable to the literature values for lutetium bisphthalocyanines.