New Metal Phthalocyanines/Metal Simple Hydroxide Multilayers: Experimental Evidence of Dipolar Field-Driven Magnetic Behavior

A series of new hybrid multilayers has been synthesized by insertion-grafting of transition metal (Cu^II, Co^II, Ni^II, and Zn^II) tetrasulfonato phthalocyanines between layers of Cu^II and Co^II simple hydroxides. The structural and spectroscopic investigations confirm the formation of new layered hybrid materials in which the phthalocyanines act as pillars between the inorganic layers. The magnetic investigations show that all copper hydroxide-based compounds behave similarly, presenting an overall antiferromagnetic behavior with no ordering down to 1.8 K. On the contrary, the cobalt hydroxide-based compounds present a ferrimagnetic ordering around 6 K, regardless of the nature of the metal phthalocyanine between the inorganic layers. The latter observation points to strictly dipolar interactions between the inorganic layers. The amplitude of the dipolar field has been evaluated from X-band and Q-band EPR spectroscopy investigation (<i>B</i>_dipolar ≈ 30 mT)

Electrocatalytic Properties of Metal Phthalocyanine Tetrasulfonate Intercalated in Metal Layered Simple Hydroxides (Metal: Co, Cu, and Zn)

A series of hybrid metal (Zn, Cu, and Co) layered simple hydroxides (LSH) functionalized by surfactants, namely, dodecylsulfonate (DS₀) or dodecylsulfate (DS^–) and by tetrasulfonato metal (Cu, Co)-phthalocyanines, was synthesized by anionic exchange reactions and characterized by ancillary techniques. The electrochemical properties of these compounds were investigated by cyclic voltammetry in phosphate buffer solutions over a wide potential range including that suitable for oxygen reduction. The electroactivity of intralayer metal cations (Cu and Co) was evidenced as a function of the phosphate buffer pH. The redox properties of Co- and Cu-PcTS₀ grafted in LSH (Zn, Co, and Cu) were also investigated in neutral pH solution, under argon, air, or O₂ atmospheres. Interestingly, these hybrid compounds display an electrocatalytic behavior toward the reduction of oxygen. In particular with CoPcTS₀-LSH, a sharp electrocatalytic reduction wave is observed at −0.40 V/Ag-AgCl with an intensity that depends on the oxygen concentration. The formation of a CoPc-O₂ grafted species in the presence of oxygen was confirmed by electron paramagnetic resonance spectroscopy