叠氮酸桥联双核铜配合物磁偶合的密度泛函研究

Ab initio Calculation for Magnetostructural Characterization of Azido-Bridged Cu(Ⅱ) Dimers

在密度泛函理论的框架下 ,采用对称性破损态方法 ,对EE ,EO两种连接方式叠氮酸桥联双核铜模型配合物进行计算 ,结果表明 ,EE方式连接为反铁磁偶合 ;EO方式则为铁磁偶合 ,但只发生在θ =91°～ 10 7°区间 ,与实验值96°～ 10 4°基本一致 .研究揭示了其磁偶合构效关系的本质在于SOMOb1g轨道中Nμ 的px 轨道与Cu的dxy轨道间的d -p -d三中心σ反键作用 ,在θ=95°～ 110°区间具有最大的反键重叠 ,因而铁磁偶合最大 .同时发现 ,J值随Cu与配位叠氮酸N原子间距离的增大而减小 。

On basis of the broken symmetry approach and density functional theory (DFT), the magnetostructural characterization of azido-bridged Cu (Ⅱ) dimers is studied which have end-to-end (EE) and end-on (EO) two main coordination modes. The calculating results show that EE mode gives antiferromagnetic interaction, whereas EO mode gives ferromagnetic coupling in which θ is about 91°～107°, basically agreealde with the experimental value 96°～104°. The essence of the magnetostructural characterization lies in d-p-d three centers σ antibonding action between two Cu d_ xy orbitals and bridged N p_x orbital in SOMO b_ 1g. In the θ region of 95°～110° the σ antibonding overlap has the maximum, which leads to the maximum ferromagnetic coupling. It is also shown that τ has no great influence on J, whereas J decreases linearly with increasing r_ Cu-Nμ.