Characterization of chemical bonds in bimetallic cyanides using X-ray absorption spectroscopy at L(2,3) edges
Characterization of chemical bonds in bimetallic cyanides using X-ray absorption spectroscopy at L(2,3) edges
复制标题
DOI：
10.1021/ja9542698
复制
发表时间：
1996-07-10
影响因子：
15
通讯作者：
Chen, CT
中科院分区：
文献类型：
--
作者：
Arrio, MA;Sainctavit, P;Chen, CT
利用3d过渡金属L（2，3）边的X射线吸收谱研究了居里温度为66 ~ 315 K的分子基磁体的电子结构。这些磁体是普鲁士蓝家族的氰化物，由-NC-Cr-III-CN-A（II）-单元的三维组装构成。X射线吸收光谱的化学选择性允许提取携带自旋矩的两种不同金属过渡离子中的每一种的信息。使用配体场多重计算，其中杂交主要是考虑到通过配置相互作用，我们已经能够很好地再现所有功能的二价3d离子L（2，3）的边缘。从精确基态的知识出发，我们确定了它的电子结构和相关参数，如晶体场强度和自旋轨道耦合。我们已经分离的共价和电荷转移效应发生在3d离子和氰基配体之间的键。从A（II）二价离子的L（2，3）边，我们发现A（II）-NC键具有弱的共价特征，电荷转移为10%。从Cr-III的Lr-2、Lr-3边缘（其中Cr离子与氰基配体的碳原子键合），我们表明配体场多重态模型仍然完全适用于强杂交键。在这种情况下，必须将共价和电荷转移分开，并考虑通过π背键的电荷转移。这些参数的精确知识是必不可少的宏观特征，如磁性的测定。
X-ray absorption spectroscopy at the L(2,3) edges of 3d transition metals has been used to study the electronic structure of molecular-based magnets with Curie temperatures ranging from 66 to 315 K. These magnets are bimetallic cyanides of the Prussian blue family, constructed by a three-dimensional assembling of -NC-Cr-III-CN-A(II)-units. The chemical selectivity of X-ray absorption spectroscopy allows information to be extracted on each of the two different metal transition ions that carry the spin moments. Using Ligand Field Multiplet calculations, where hybridization is mainly taken into account through configuration interaction, we have been able to reproduce nicely all the features of the divalent 3d ion L(2,3) edges. From the knowledge of the exact ground state, we have determined its electronic structure and relevant parameters, such as the crystal field strength and the spin-orbit coupling. We have separated covalence and charge transfer effects occurring in the bond between the 3d ions and the cyano ligand. From the L(2,3) edges of A(II) divalent ions, we found that the A(II)-NC bond has a weak covalent character with a 10% charge transfer. From the Lr-2,Lr-3 edges of Cr-III, where Cr ions are bonded to the carbon atom of the cyano ligand, we have shown that the Ligand Field Multiplet model is still fully applicable for strongly hybridized bonds. In this case it is essential to separate between covalence and charge transfer and to take the charge transfer into account through pi back-bonding. The precise knowledge of these parameters is essential for the determination of macroscopic characters like magnetic properties.