Department of Chemistry, University of Belgrade, Studentski trg 16, 11000 Belgrade, Serbia.
J Inorg Biochem. 2012 Dec;117:157-63. doi: 10.1016/j.jinorgbio.2012.09.002. Epub 2012 Sep 8.
CH/π interactions in metal porphyrinato complexes were studied by analyzing data in crystal structures from the Cambridge Structural Database (CSD) and by quantum chemical calculations. The analysis of the data in the CSD shows that both five-membered pyrrole and six-membered chelate rings form CH/π interactions. The interactions occur more frequently with five-membered rings. The analysis of distances in crystal structures and calculated energies show stronger interactions with six-membered chelate rings, indicating that a larger number of interactions with five-membered rings are not the consequence of stronger interactions, but better accessibility of five-membered pyrrole rings. The calculated energies of the interactions with positions in six-membered rings are -2.09 to -2.83 kcal/mol, while the energies with five-membered rings are -2.05 to -2.26 kcal/mol. The results reveal that stronger interactions of six-membered rings are the consequence of stronger electrostatic interactions. Substituents on the porphyrin ring significantly strengthen the interactions. Substituents on the six-membered ring strengthen the interaction energy by about 20%. The results show that CH/π interactions play an important role in molecular recognition of metalloporphyrins. The significant influence of the substituents on interaction energies can be very important for the design of model systems in bioinorganic chemistry.
通过分析剑桥结构数据库（CSD）中的晶体结构数据和量子化学计算，研究了金属卟啉配合物中的 CH/π 相互作用。CSD 中数据的分析表明，五元吡咯环和六元螯合环都形成 CH/π 相互作用。五元环的相互作用更频繁。晶体结构中距离和计算能量的分析表明，六元螯合环的相互作用更强，表明与五元环的相互作用较多不是由于相互作用更强，而是五元吡咯环的可及性更好。与六元环位置的相互作用计算能量为-2.09 至-2.83 kcal/mol，而与五元环的能量为-2.05 至-2.26 kcal/mol。结果表明，六元环更强的相互作用是由于更强的静电相互作用。卟啉环上的取代基显著增强了相互作用。六元环上的取代基使相互作用能增强约 20%。结果表明，CH/π 相互作用在金属卟啉的分子识别中起着重要作用。取代基对相互作用能的显著影响对于生物无机化学中模型系统的设计非常重要。
