Department of Chemistry, University of Kansas, 1567 Irving Hill Road, Lawrence, KS 66045, USA.
Molecules. 2020 Jul 13;25(14):3189. doi: 10.3390/molecules25143189.
4,5-diazafluorene (daf) and 9,9'-dimethyl-4,5-diazafluorene (Medaf) are structurally similar to the important ligand 2,2'-bipyridine (bpy), but significantly less is known about the redox and spectroscopic properties of metal complexes containing Medaf as a ligand than those containing bpy. New complexes Mn(CO)Br(daf) (), Mn(CO)Br(Medaf) (), and Ru(Medaf) () have been prepared and fully characterized to understand the influence of the Medaf framework on their chemical and electrochemical properties. Structural data for , , and from single-crystal X-ray diffraction analysis reveal a distinctive widening of the daf and Medaf chelate angles in comparison to the analogous Mn(CO)(bpy)Br () and [Ru(bpy)] () complexes. Electronic absorption data for these complexes confirm the electronic similarity of daf, Medaf, and bpy, as spectra are dominated in each case by metal-to-ligand charge transfer bands in the visible region. However, the electrochemical properties of , , and reveal that the redox-active Medaf framework in and undergoes reduction at a slightly more negative potential than that of bpy in and . Taken together, the results indicate that Medaf could be useful for preparation of a variety of new redox-active compounds, as it retains the useful redox-active nature of bpy but lacks the acidic, benzylic C-H bonds that can induce secondary reactivity in complexes bearing daf.
4,5-二氮菲（daf）和 9,9'-二甲基-4,5-二氮菲（Medaf）在结构上与重要配体 2,2'-联吡啶（bpy）相似，但人们对含 Medaf 作为配体的金属配合物的氧化还原和光谱性质的了解远少于含 bpy 的配合物。我们已经制备并充分表征了新的配合物 Mn(CO)Br(daf) ()、Mn(CO)Br(Medaf) ()和Ru(Medaf) ()，以了解 Medaf 骨架对其化学和电化学性质的影响。来自单晶 X 射线衍射分析的数据表明，与类似的 Mn(CO)(bpy)Br ()和[Ru(bpy)] ()配合物相比，daf 和 Medaf 螯合角明显变宽。这些配合物的电子吸收数据证实了 daf、Medaf 和 bpy 的电子相似性，因为在每种情况下，光谱都由可见区域中金属到配体电荷转移带主导。然而，、和的电化学性质表明，在和中，氧化还原活性的 Medaf 骨架的还原电位比在和中 bpy 的还原电位略负。总之，这些结果表明 Medaf 可用于制备各种新的氧化还原活性化合物，因为它保留了 bpy 的有用氧化还原活性，但缺乏酸性、苄基 C-H 键，这些键在含有 daf 的配合物中会引起次级反应性。
