Faizan Mohmmad, Behera Debendra, Chakraborty Madhumita, Pawar Ravinder
Laboratory of Advanced Computation and Theory for Materials and Chemistry, Department of Chemistry, National Institute of Technology Warangal (NITW), Warangal, Telangana, 506004, India.
Chemphyschem. 2024 Dec 16;25(24):e202400647. doi: 10.1002/cphc.202400647. Epub 2024 Oct 28.
Sequestering carbon dioxide (CO) from the atmosphere is necessary to achieve a sustainable environment. However, the thermodynamic stability of the CO molecule poses a significant challenge to its capture, necessitating catalysts that can overcome this stability. The emergence of frustrated Lewis pairs (FLPs) has opened a new dimension in the development of organocatalysts for CO capture and utilization. To date, various FLPs have been developed for CO sequestration, yet the quest for robust FLPs continues. Based on the intriguing electronic effects of the carborane polyhedral, o-carboranes can be projected as a versatile bridging unit for intramolecular FLPs (IFLPs). In the present work, o-carborane based IFLPs i. e., 1-Al(CH)-2-P(CH)-1,2-C2BH, 1-B(CH)-2-P(CH)-1,2-CBH, 1-Al(CH)-2-N(CH)-1,2-CBH, 1-P(CH)-2-B(CH)-1,2-CBH abbreviated as AlP, BP, AlN and BN have been proposed for the activation of CO molecule. The density functional theory (DFT) based calculations and thorough orbital analysis have been carried out to extensively study the electronic structure of the o-carborane unit. The proposed IFLPs were systematically compared with their corresponding phenyl bridged analogues to assess the effect of o-carborane bridging unit on the reactivity of the acidic and basic sites. The results show that the o-carborane supported IFLPs are more reactive towards CO than the phenyl bridged IFLPs. Also, placing the basic site on the B atom at the 4 position of the o-carborane bridge rather than the C atom at the 2 position results in more reactive IFLPs.
从大气中封存二氧化碳（CO₂）对于实现可持续环境至关重要。然而，CO₂分子的热力学稳定性对其捕获构成了重大挑战，因此需要能够克服这种稳定性的催化剂。受阻路易斯酸碱对（FLP）的出现为用于CO₂捕获和利用的有机催化剂的开发开辟了新的维度。迄今为止，已经开发了各种用于CO₂封存的FLP，但对强大的FLP的探索仍在继续。基于碳硼烷多面体引人入胜的电子效应，邻碳硼烷可被视为分子内FLP（IFLP）的通用桥连单元。在本工作中，已提出基于邻碳硼烷的IFLP，即1 - Al(CH₃) - 2 - P(CH₃) - 1,2 - C₂B₁₀H₁₀、1 - B(CH₃) - 2 - P(CH₃) - 1,2 - C₂B₁₀H₁₀、1 - Al(CH₃) - 2 - N(CH₃) - 1,2 - C₂B₁₀H₁₀、1 - P(CH₃) - 2 - B(CH₃) - 1,2 - C₂B₁₀H₁₀，简称为AlP、BP、AlN和BN，用于活化CO₂分子。已进行基于密度泛函理论（DFT）的计算和全面的轨道分析，以广泛研究邻碳硼烷单元的电子结构。将所提出的IFLP与其相应的苯基桥连类似物进行系统比较，以评估邻碳硼烷桥连单元对酸性和碱性位点反应性的影响。结果表明，邻碳硼烷负载的IFLP对CO₂的反应性比苯基桥连的IFLP更高。此外，将碱性位点置于邻碳硼烷桥4位的B原子上而非2位的C原子上会产生反应性更高的IFLP。
