金属串配合物[CoMCo(dpa)_4(NCS)_2](M=Co,Ni,Pd,Pt)结构和自旋过滤性质研究  

Theoretical Studies on the Structures and Spin Filtering Property of Metal String Complexes[CoMCo(dpa)_4( NCS)_2]( M = Co,Ni,Pd,Pt)

作　　者：吴子文[1] 周沃华 丁丹丹[1] 陈蓉[1] 许旋[1,2,3] 罗一帆[1,2,3] 徐志广[1,2,3] 

机构地区：[1]华南师范大学化学与环境学院,广州510006 [2]教育部环境理论化学重点实验室,广州510006 [3]广州市能源转化与储能材料重点实验室,广州510006

出　　处：《华南师范大学学报（自然科学版）》2016年第1期58-66,共9页Journal of South China Normal University(Natural Science Edition)

基　　金：广东省自然科学基金项目(S2012010008763);广东省教育部产学研项目(2010B090400184);广州市科技攻关项目(2011J4300063)

摘　　要：应用密度泛函理论B3LYP方法对金属串配合物[Co MCo(dpa)4(NCS)2](1:M=Co,2:M=Ni,3:M=Pd,4:M=Pt;dpa=二吡啶胺)的成键性质和自旋过滤效应进行了研究,结果表明:配合物1的基态为二重态,Co6+3金属链形成三中心三电子σ键(σ2σ1nbσ*0);而配合物2~4的基态均为反铁磁耦合单重态(AF态),对应的最低能量高自旋态(HS态)分别为三重态、七重态和七重态,单电子分布在两端Co原子上,[Co MCo]6+链具有三中心四电子σ键(σ2σ1nbσ*1).配合物1~4均具有自旋过滤效应,电子传输通道主要为β-自旋σnb轨道,与费米能级的距离大小为1<2<3≈4.电场作用下,1~4的高电势端Co2—N4键增长而低电势端Co3—N7键缩短,Co—M平均键长略为缩短,Co—M键增强;电场作用下金属原子的自旋密度和电荷密度变化很小,电磁性质稳定;电场作用下σnb轨道分布仍保持沿金属轴方向离域,LUMO-HOMO能隙减小,有利于电子输运.The bonding and spin filtering properties of metal string complexes [ CoMCo（ dpa）4 （NCS） 2 ] （ M = Co, Ni, Pd, Pt; dpa = dipyridylamine） have been investigated with the density functional theory B3LYP method. The results show that the ground state of complex 1 is doublet, and there is a 3-center-3-electron σ bond （σ2σ1nbσ ＊0） delocalized over the Co6＋3 chain. However, the ground states of complexes 2 - 4 are antiferromagnetic （AF） singlet, corresponded to the high spin configurations with two unpaired, six unpaired and six unpaired electrons, respectively. The unpaired electrons of complexes 2 ^-4 largely localize on the terminal Coll ions and there is a 3-center-4-e- lectron cr bond （ σ2σ1nbσ＊ 1 ） delocalized over the [ CoMCo ] 6 ＋ chain. The molecular orbital energy level diagrams and PDOS diagrams show that the spin-J3 components of singly σnb orbital are the dominant transport channel. Com- plexes 1 - 4 all possess spin filtering effect. The distance between spin-13 components of σnb orbital and Fermi levels is 1 〈2 〈3≈4. Under the electric field, the Co2--N4 bond lengths at the high potential side increase, while the Co3--N7 distances at the low potential side tend are shortened. The average Co--M distances, the spin densities and NPA charge of metal atoms are less affected by electric field, indicating the electromagnetic properties are sta- ble. Under the electric field, the CrnbOrbital still keeps delocalized along the metal chain and the LUMO-HOMO gaps decrease. This is beneficial for electron transfer.

关 键 词：金属串配合物 密度泛函理论 自旋过滤 电场作用 对称破损 

分 类 号：O641[理学—物理化学]