Nanocap-Shaped Tin Phthalocyanines: Synthesis, Characterization, and Corrosion Inhibition Activity

Thermal and microwave reactions between [PcSnIVCl2] (1) and the potassium salts of eight fatty acids (2 a–h) led to cis‐[(RCO2)2SnIVPc] compounds (3 a–h) in yields ranging from 54 to 90 %. Compounds 3 a–h were fully characterized by elemental analysis, spectroscopy (IR, UV/Vis, multinuclear NMR), and seven X‐ray diffraction structures, whereby two different allotropes were observed in two cases. The two carboxylates in 3 have a cis anisobidentate binding mode, octacoordination of the tin atoms with square‐antiprismatic geometry, and π‐electron‐rich nanocap shapes. On account of the latter characteristics, 3 a–h compounds have anticorrosion properties. LPR and Tafel electrochemical methods were used to characterize the behavior of these derivatives in naturally aerated sour brine, which is a common environment in petroleum production and refinery operations. The measurement of the corrosion rate of carbon steel AISI 1018 in the presence of 3 a–h (500 ppm) gave efficiencies of 61–87 % for the inhibitor performance. Of the different derivatives examined, compounds 3 e and 3 h were the most effective corrosion inhibitor prototypes. Thermal and microwave reactions between [PcSnIVCl2] and the potassium salts of fatty acids led to cis‐[(RCO2)2SnIVPc] complexes in good yields. The X‐ray structures of the latter exhibit two cis‐anisobidentate carboxylates, octacoordination of the tin atoms with square‐antiprismatic geometry, and nanocap shapes (see picture). The measurement of the corrosion rate of carbon steel AISI 1018 in the presence of the PcSn compounds indicated highly efficient inhibition.