希土冠醚配合物的电子结构

本文用INDO方法计算了希土冠醚配合物的分子构型、电子结构、电荷分布和键级,讨论了配位前后电荷分布特征,以及由于配位引起L→L_n电荷转移跟配合物电子结合能化学位移和配位活化的关系,解释了因冠醚内腔不同希土冠醚配合物呈现不同构型的内在原因。希土冠醚配合物的占据分子轨道以配位体轨道成分为主体(4f轨道除外),低空轨道以希土原子轨道成分为主体。其占据分子轨道可分为六组。冠醚环上引入苯环后配合物前线轨道呈现π键性质。其价键的主要贡献部份是5d轨道,其次是6p和6s。4f轨道基本上不参与成键。讨论了配合物的化学键性质及高配位数时稳定的因素。

ELECTRONIC STRUCTURE OF COMPLEXES OF LANTHANIDE IONS WITH CROWN ETHERS

The total energy of molecules, electronic structure, charge distribution and Mulliken' s bond orders in the complexes of lanthanide nitrate or chloride with crown ethers have been calculated using an INDO method. The cause of structural difference between La(NO3)315-C-5 and La(NO3)318-C-6 is related to the cavity of crown ethers. The configuration with the three nitrate groups on one side and crown ring on the other side of La is energetically the most preferable. At coordination the charge transfer O(Cr) Ln leads to the shift of orbital levels and weakening of the bond of Ln-O(NO3) or Ln-Cl. The ligand constituents are dominant in the occupied MO's (except for 4f), while the Ln constituents are dominant in low unoccupied MO's. The occupied MO's may be classified into six groups. Benzene ring linked with crown ether makes frontier MO's shown n character. The covalent bonding is mainly due to the participation of 5d, and a lesser extent, 6p and 6s. The 4f orbitals almost do not participate in covalent bonding. The chemical bonding and stabilization factors of the complexes at high coordination numbers were discussed.