Chiong Meliton R, Paraan Francis N C
Materials Science and Engineering Program, University of the Philippines Diliman Quezon City Philippines
National Institute of Physics, University of the Philippines Diliman Quezon City Philippines.
RSC Adv. 2019 Jul 26;9(40):23254-23260. doi: 10.1039/c9ra01990a. eCollection 2019 Jul 23.
The nucleophilic properties of cobalt salen complexes are examined using density functional theory to investigate its carbon fixing capacity. In particular, carbon dioxide attack on neutral and anionic cobalt salen molecules is considered. Carbon fixation occurs for the anionic cobalt salen complex and is due to the nucleophilic interaction between the cobalt center and carbon dioxide molecule in a Co d -CO π* interaction. A minimum energy path search by a nudged elastic band calculation reveals a lower forward activation energy for the anionic complex than the neutral complex, indicating that the formation of the anionic complex is thermodynamically and kinetically favored. In this case, the CO molecule is chemisorbed as partial charge transfer from the cobalt center to carbon dioxide is observed. Proposed reaction mechanisms explain how the Co-C bond energy of the CO-cobalt salen complex can be tuned by appropriate substitutions of electron donating or withdrawing groups on the phenyl ring.
利用密度泛函理论研究了钴 - 双水杨醛缩乙二胺配合物的亲核性质，以考察其碳固定能力。特别考虑了二氧化碳对中性和阴离子型钴 - 双水杨醛缩乙二胺分子的进攻。阴离子型钴 - 双水杨醛缩乙二胺配合物发生碳固定，这是由于钴中心与二氧化碳分子之间通过Co d -CO π*相互作用产生的亲核相互作用。通过推挤弹性带计算进行的最小能量路径搜索表明，阴离子型配合物的正向活化能低于中性配合物，这表明阴离子型配合物的形成在热力学和动力学上更有利。在这种情况下，观察到CO分子发生化学吸附，因为存在从钴中心到二氧化碳的部分电荷转移。提出的反应机理解释了如何通过在苯环上适当取代供电子或吸电子基团来调节CO - 钴 - 双水杨醛缩乙二胺配合物的Co - C键能。
