Unique Axial Imidazole Geometries of Fully Halogenated Iron(II) Porphyrin Complexes: Crystal Structures and Mössbauer Spectroscopic Studies

The synthesis and characterization of several electron-poor iron­(II) porphyrin (FeTFPPBr8) complexes with axial imidazole ligands are reported. The single-crystal X-ray structures have been studied by a combination of crystal packing and Hirshfeld surface calculations, which explained the unusual axial-ligand geometries, e.g., the strong tilt of the Fe–NIm bonds and the imidazole planes. The six-coordinate [Fe­(TFPPBr8)­(1-MeIm)2] was studied by multiple-temperature solid-state Mössbauer spectroscopy, which suggested that it is a low-spin complex with δ ∼ 0.32–0.38 mm/s and ΔEQ ∼ 1.0 mm/s.本研究报告了多种缺乏电子的铁(II)卟啉（FeTFPPBr8）配合物与轴向咪唑配体的合成与表征。通过晶体堆积与Hirshfeld表面计算相结合的研究方法，探讨了其异常轴向配体几何结构，例如Fe–NIm键的强烈倾斜及咪唑平面的独特排列。六配位的[Fe(TFPPBr8)(1-MeIm)2]配合物经多温度固态莫塞巴（Mössbauer）光谱学分析，表明其为低自旋配合物，δ值约为0.32–0.38 mm/s，ΔEQ值约为1.0 mm/s。