| Multifunctional Co(II)–Calix[4]arene Catalyst for Green Homogeneous Synthesis of Nitriles and Benzothiazoles |
| کد مقاله : 1271-ICOC |
| نویسندگان |
|
reza sandaroos *1، Danial Mohammadi2 1عضو هیات علمی 2Chemistry department, University of Birjand, Birjand, Iran |
| چکیده مقاله |
| A stable, multifunctional Co(II)-based homogeneous catalyst was designed and synthesized by integrating calix[4]arene units with a flexible ligand framework. This architecture was intended to enhance complex stability, facilitate charge transfer, and promote host–guest interactions, providing a well-defined microenvironment for oxidation reactions. The stepwise synthesis of the TSPIC ligand followed by coordination with Co(II) afforded the Co(II)–TSPIC complex [1].The Co(II)–TSPIC complex was thoroughly characterized using FT-IR, ¹H and ¹³C NMR, CHN elemental analysis, ICP metal quantification, and UV–Vis spectroscopy. These analyses indicate a robust coordination environment with suitable electronic properties for homogeneous oxidation reactions. The catalyst was applied in two green oxidation processes. First, the oxidative conversion of benzylic alcohols to benzonitriles under solvent-free conditions at 60 °C, using 0.3 mmol H₂O₂ and trace Co(II), gave 95% yield. Electron-donating substituents on the aromatic ring accelerated the reaction, while electron-withdrawing groups slowed it, consistent with a rate-determining electrophilic oxidation of the alcohol to aldehyde. Second, the catalyst facilitated a one-pot synthesis of benzothiazoles, which proceeded optimally in aqueous media, where water acted as a proton shuttle during condensation and cyclization, achieving up to 95% yield under mild conditions (45 °C, 30 min, minimal oxidant). Substrate trends mirrored those observed in nitrile formation, confirming that initial alcohol oxidation is the rate-limiting step in both reactions. The calix[4]arene units enhance molecular organization and bring the oxidant closer to the metal center, improving catalytic efficiency and oxygen activation. This structural feature contributes to high selectivity, turnover, and overall reaction sustainability. The catalyst exhibited excellent recyclability, maintaining 90% yield after four consecutive cycles, and spectroscopic analyses confirmed retention of structural integrity. These results indicate that the calix[4]arene scaffold effectively prevents metal leaching and protects the coordination framework from degradation. |
| کلیدواژه ها |
| Co(II) Catalyst, Calix[4]arene, Catalyst Stability, Benzonitriles Synthesis |
| وضعیت: پذیرفته شده |