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首页> 外文期刊>Dalton transactions: An international journal of inorganic chemistry >Cu(HCO_2)_2L {L = pyrazine, 4,4'-bipyridine}: employing the formate anion as a building block in three-dimensional coordination polymers
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Cu(HCO_2)_2L {L = pyrazine, 4,4'-bipyridine}: employing the formate anion as a building block in three-dimensional coordination polymers

机译：Cu（HCO_2）_2L {L =吡嗪，4,4'-联吡啶}：在三维配位聚合物中使用甲酸根阴离子作为结构单元

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摘要

The formate anion, HCO_2~-, has been used infrequently as a building block in molecular magnetic materials. We have synthesized and structurally and magnetically characterized two new Cu(HCO_2)_2L compounds, where L represents pyrazine (pyz) and 4,4'-bipyridine (bipy). The single crystal structure of Cu(HCO_2)_2(pyz), 1, has been established by both X-ray (295 K) and neutron diffraction (20 K). The compound consists of tetragonally-elongated CuN_2O_4 octahedra made up of four bridging formate anions and two neutral pyz ligands. The 3D polymeric network is comprised of 2D Cu(HCO_2)_2 layers that are fused together by the linear pyz spacers, which form Cu-pyz-Cu chains. Cu(HCO_2)_2(bipy), 2, is chiral and has a more complex framework than 1. The CuO_4N_2 octahedra align in two unique orientations relative to one another, owing to the 4_1 and 2_1 screw axes that lie along the a and b-axes. The octahedra are connected via four birdging HCO_2~- anions and two bridging bipy ligands, resulting in a unique 3D scaffold structure. The magnetic behavior of 1 and 2 indicates antiferro- and ferromagnetic interactions, respectively, and the exchange couplings in both 1 and 2 are well reproduced by a 1D spin Hamiltonian. Spin dimer analysis was carried out to evaluate the relative strengths of the various spin exchange paths. It is found that the interaction through HCO_2~- is comparatively weak, and the strong Cu~(2+) spin exchange interactions are mediated by the pyz and bipy ligands via the σ-pathway. A possible reason as to why 2 displays ferromagnetic coupling is proposed.
机译：甲酸酯阴离子HCO_2〜-很少用作分子磁性材料的基础材料。我们已经合成并在结构和磁性上表征了两种新的Cu（HCO_2）_2L化合物，其中L代表吡嗪（pyz）和4,4'-联吡啶（bipy）。 Cu（HCO_2）_2（pyz），1的单晶结构已通过X射线（295 K）和中子衍射（20 K）建立。该化合物由四边形延伸的CuN_2O_4八面体组成，该八面体由四个桥连的甲酸根阴离子和两个中性的pyz配体组成。 3D聚合物网络由2D Cu（HCO_2）_2层组成，这些2D Cu（HCO_2）_2层通过线性pyz间隔基融合在一起，形成Cu-pyz-Cu链。 Cu（HCO_2）_2（bipy），2，是手性的，比1具有更复杂的框架。由于沿a和b的4_1和2_1螺钉轴，CuO_4N_2八面体相对于彼此以两个唯一的方向对齐。 -轴。八面体通过四个鸟状HCO_2〜-阴离子和两个桥联的Bipy配体连接，从而形成独特的3D支架结构。 1和2的磁行为分别表示反铁磁相互作用和铁磁相互作用，并且1D和2中的交换耦合通过一维自旋哈密顿量很好地再现。进行自旋二聚体分析以评估各种自旋交换路径的相对强度。发现通过HCO_2〜-的相互作用相对较弱，并且强的Cu〜（2+）自旋交换相互作用是由pyz和bipy配体通过σ途径介导的。提出了关于为什么2显示铁磁耦合的可能原因。

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