Spin Densities in a Ferromagnetic Bimetallic Chain Compound: Polarized Neutron Diffraction and DFT Calculations

详细信息    查看全文

• 作者：Bé ; atrice Gillon ; Corine Mathoniè ; re ; Eliseo Ruiz ; Santiago Alvarez ; Alain Cousson ; Thekkel M. Rajendiran ; and Olivier Kahn
• 刊名：Journal of the American Chemical Society
• 出版年：2002
• 出版时间：December 4, 2002
• 年：2002
• 卷：124
• 期：48
• 页码：14433 - 14441
• 全文大小：258K
• 年卷期：v.124,no.48(December 4, 2002)
• ISSN：1520-5126

文摘

The spin population distribution in the ferromagnetically coupled hetero-bimetallic chain compound[MnNi(NO₂)₄(en)₂] (en = 1,2-ethanediamine) has been investigated by means of polarized neutron diffractionexperiments, and the results compared with those from theoretical estimates obtained via calculationsbased on density functional theory on dinuclear molecular models of the chain. The spin distributions obtainedfrom experiment and from theory are consistent and reflect a larger spin delocalization from the Ni atomdue to the more covalent character of the Ni-N bonds compared to the Mn-O ones. Also a nearly isotropicspin distribution is observed for the more ionic d⁵ Mn²⁺ ion and a clearly anisotropic distribution for the d⁸Ni²⁺ ion. The use of dinuclear molecular models for the calculation of the exchange coupling constantbetween Ni and Mn provide upper and lower limits (+17.6 and -4.2 cm^-1) for the experimentally determinedvalue (+1.3 cm^-1), depending on how the missing part of the chain is simulated, but yield essentially thesame spin distribution. The Mn(II)-Ni(II) weak ferromagnetic coupling in the chain is interpreted in a spindelocalization mechanism as resulting from the weakness of the overlap between the magnetic orbitalscentered on nickel and those centered on manganese which are only weakly delocalized on the ligands.