MII-meso-tetrakis(2,3-dichlorophenyl)porphyrins as catalysts for CO2 cycloaddition reaction under mild conditions: kinetic and theoretical investigation

• Published in: Molecular catalysis 2023-12, Vol.551, p.113593, Article 113593
• Main Authors: Milani, Jorge Luiz Sônego, Bezerra, Werberson de Almeida, Meireles, Alexandre Moreira, da Mata, Álvaro Farias Arruda, Ferreira, Frederico Henrique do Carmo, Costa, Luiz Antônio Sodré, Martins, Felipe Terra, Martins, Dayse Carvalho da Silva, Pavão das Chagas, Rafael
• Format: Article
• Language: English
• Subjects: Carbon dioxide; Cyclic carbonate; Kinetics; Mechanism; Porphyrin
• ISSN: 2468-8231; 2468-8231
• DOI: 10.1016/j.mcat.2023.113593

•M(II)-porphyrins (M= Zn, Co, Cu) catalysts for CO2 conversion.•Active catalysts selectively producing cyclic carbonates under mild conditions.•Kinetic investigations and DFT studies to elucidate the mechanism.•Isolation of a dormant specie bearing two DMAP axially coordinated to CoII. A series of new porphyrins with ZnII, CoII, and CuII (1-3) as a metal center are reported. These complexes were evaluated in the CO2 cycloaddition reaction in epoxides under mild conditions (30-80°C and 1 bar of CO2 pressure) and solvent-free conditions; in optimal conditions, they present high conversion (>99 %) and selectively produce styrene cyclic carbonate. To comprehend the mechanism of the reaction, synchronously, a kinetic approach was carried out using the 1/TBAB system and only TBAB to evaluate the activation energy (Ea) for catalyzed and uncatalyzed reactions. The results support the synergism between the catalyst and the cocatalyst decreasing the Ea in 20.48 kJ mol−1. In addition, the thermodynamics parameters (ΔG‡, ΔH‡, ΔS‡) were also determined using Eyring´s equation. Moreover, a unique example of dormant species for catalyst 3 bearing two DMAP axially coordinated to CoII was determined by X-ray diffractometry. Theoretical studies also supported the experimental data; the catalytic cycle has been revealed at the molecular level and pointed out the best epoxide activation for the ZnII complex. [Display omitted]