A new mononuclear high-spin complex, trans-[Fe(pzCN)₄Cl₂] (1), was prepared from the reaction of FeCl₂.4H₂O and 2-cyanopyrazine (pzCN) in acetonitrile as a solvent. Suitable crystals of this complex for crystal structure determination were collected by slow evaporation of the produced pale orange solution. Complex 1 was characterized by elemental analysis (CHN), spectral methods (IR and UV–Vis), and single-crystal X-ray diffraction. The X-ray structural analysis indicated that the iron(II) is six-coordinated in an octahedral configuration by four N atoms from four 2-cyanopyrazine ligands and two chloride anions. Furthermore, the average of Fe–N bond lengths is 2.284(1)Å. It is well known that in the high-spin iron(II) phenanthroline and bipyridine complexes, the Fe–N bond lengths are around 2.2 Å. So, due to the Fe–N bond length in this complex, the iron(II) is unambiguously high-spin. The experimental evaluations on 1 have been complemented theoretically by the density functional theory (DFT) and TD-DFT calculations. The character of the Fe–N and Fe–Cl bonds was investigated using quantum theory of atoms in molecules. Additionally, electron delocalization and hyper-conjugative interactions of the synthesized complex were evaluated by natural bond orbital calculations.

由FeCl ₂ .4H ₂ O和2-氰基吡嗪（pzCN）在乙腈为溶剂中反应制备了一种新的单核高自旋络合物反式[[Fe（pzCN）₄ Cl ₂ ]（1）。通过缓慢蒸发产生的浅橙色溶液，收集用于晶体结构确定的该络合物的合适晶体。综合大楼 1 通过元素分析（CHN），光谱方法（IR和UV-Vis）以及单晶X射线衍射进行表征。X射线结构分析表明，铁（II）在八面体构型中由来自四个2-氰基吡嗪配体和两个氯化物阴离子的四个N原子进行六配位。此外，Fe–N键的平均长度为2.284（1）Å。众所周知，在高旋转铁（II）菲咯啉和联吡啶配合物中，Fe–N键的长度约为2.2Å。因此，由于该复合物中Fe–N键的长度，铁（II）无疑是高自旋的。1的实验评价密度泛函理论（DFT）和TD-DFT计算在理论上得到了补充。使用分子中原子的量子理论研究了Fe–N和Fe–Cl键的特征。此外，通过自然键轨道计算评估了合成配合物的电子离域和超共轭相互作用。