Theoretical Study on the Structures and Magnetic Properties of Metal String Complexes Containing Rigid Equatorial Ligands Ni3(L)4(NCS)2 (L=dzp-, mpmpa-, mppda-, mptpa-)

摘要

Density functional theory at the BP86 level was used to investigate the influence of equatorial ligands on the Ni-Ni interactions and magnetic coupling properties of metal string complexes [Ni3(L)4(NCS)2] (L represents the rigid equatorial ligands;L =dzp (1),mpmpa-(2),mppda-(3),mptpa-(4)).The following conclusions can be drawn.(1) With increasing the radius of the connecting atom in the eental ring in equatorial ligands,the two pyridine rings bend down,resulting in the decreasing distance between the two pyridine-nitrogen atoms and the Ni-Ni distance.Therefore,the strength order of the Ni-Ni interaction is 4 ＞ 2 ＞ 3 ＞ 1.The Ni-Ni interactions in 2 and 4 are stronger than those in Ni3(dpa)4(NCS)2 containing no-rigid equatorial ligands.(2) The calculated-Jab is 4 ＞ 2 ＞ 3 ＞ 1.There are two types of magnetic exchange pathways in these complexes:the σ-type pathway through the Ni36+ chains and the δ-type pathway through the equatorial ligands.The magnetic coupling through the metals is the dominant part.Hence,the magnetic coupling strength increases with increasing the Ni-Ni interaction.Modifying the radius of the connecting atom may be one of the means to frne tuning of magnetic coupling strength of this kind of metal string complexes.