Electronic Effects in 12-Metallacrown-3 Complexes. A Theoretical and Experimental Study

The Mulliken charges of the 12-metallacrown-3 complex [(C6H6)Ru(C5H3NO2)]3 were determined by a single point
analysis at the HF level. For comparison, a Mulliken population analysis was carried out for the organic analogue
12-crown-3. The partial negative charges on the O-donor atoms of the metallamacrocycle were found to be larger
than those on the O-donor atoms of 12-crown-3. The 12-metallacrown-3 complex [(cymene)Ru(C5H2ClNO2)]3 with
chloro-substituents in position 5 of the pyridonate ligand was synthesized to determine the effect of electron
withdrawing groups on the structure and the host−guest properties of the receptor. The chloro-substituents were
found to have only a small influence on the structures, but they reduce the binding affinity for LiCl and NaCl by
approximately 2 orders of magnitude.

本研究通过哈特雷克-福克（Hartree-Fock，HF）水平下的单点分析，测定了12-金属冠醚-3（12-metallacrown-3）配合物[(C₆H₆)Ru(C₅H₃NO₂)]₃的密立根电荷（Mulliken charges）。为进行对比分析，我们同时对有机类似物12-冠-3（12-crown-3）开展了密立根布居分析（Mulliken population analysis）。结果表明，该金属大环的氧供体原子所带的部分负电荷，高于12-冠-3的氧供体原子。为探究吸电子基团（electron withdrawing groups）对该受体的结构与主客体性质（host−guest properties）的影响，我们合成了在吡啶酮配体5位带有氯取代基的12-金属冠醚-3配合物[(伞花烃(cymene))Ru(C₅H₂ClNO₂)]₃。研究发现，氯取代基对配合物结构的影响较为微弱，但可使该受体对氯化锂（LiCl）与氯化钠（NaCl）的结合亲和力（binding affinity）降低约两个数量级。