Center for Materials Crystallography, Department of Chemistry and iNANO, Aarhus University, Langelandsgade 140, DK-8000 Aarhus C, Denmark.
Inorg Chem. 2013 Jan 7;52(1):297-305. doi: 10.1021/ic301918x. Epub 2012 Dec 10.
We present a combined experimental and theoretical charge density study of the coordination polymer Zn(HCOO)(2)(H(2)O)(2), which serves as a nonmagnetic reference for the isostructural magnetic compounds containing 3d transition metals. The charge density has been modeled using the multipole formalism against a high-resolution single-crystal X-ray diffraction data set collected at 100 K. The theoretical model is based on periodic density functional theory calculations in the experimental geometry. To gauge the degree of systematic bias from the multipole model, the structure factors of the theoretical model were also projected into a multipole model and the two theoretical models are compared with the experimental results. All models, both experiment and theory, show that the Zn atom densities are highly spherical but show small accumulations of charge toward the negative ligands. The metal-ligand interactions are found to be primarily ionic, but there are subtle topological indications of covalent contributions to the bonds. The source function calculated at the bond critical points reveals a rather delocalized picture of the density in the bridging carboxylates, and this presumably reflects the exchange pathway in the magnetic analogues.
我们呈现了配位聚合物 Zn(HCOO)(2)(H(2)O)(2) 的实验和理论电荷密度研究，该聚合物作为含有 3d 过渡金属的同构磁性化合物的非磁性参比物。电荷密度是使用多极子形式理论针对在 100 K 下收集的高分辨率单晶 X 射线衍射数据集进行建模的。理论模型是基于实验几何形状的周期性密度泛函理论计算。为了衡量多极子模型的系统偏差程度，理论模型的结构因子也被投影到多极子模型中，并将两个理论模型与实验结果进行比较。所有模型，包括实验和理论，都表明 Zn 原子密度高度呈球形，但向负配体聚集少量电荷。发现金属-配体相互作用主要是离子性的，但键上有细微的拓扑迹象表明存在共价贡献。在键临界点计算的源函数揭示了桥连羧酸根中密度的相当弥散图像，这大概反映了磁性类似物中的交换途径。
