配体对具有三齿ons配位的单核锰-(III)和-(IV)配合物合成和氧化还原方面的控制

R. Mukhopadhyay, Samiran Bhattacharjee, R. Bhattacharyya
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引用次数: 15

摘要

MnCl2·4H2O与苯甲羟肟酸(BHAH2)在水溶液/非水溶液(碱性)中反应形成(PPh4)2[Mn(BHA)3]·3H2O类型的锰(IV)配合物。该配合物在冷冻溶液中表现出强零场分裂的轴向光谱,导致ag≈4的信号比forge≈2的信号更强烈。然而,固体呈现出菱形光谱。给出了造成这种差异的可能原因。三官能团(ONS)希夫碱H2L1和H2L2 (5- r -水杨基醛-4-苯基硫代氨基脲);R=H, Me或Br)生成[MnL2](L=L1或L2)型Mn(IV)配合物,而H2L3和H2L4 (H2L3= s -甲基3-(5-R-2-羟基苯基)亚甲基二硫代氨基甲酸酯;H2L4= s -苄基3-(5- r -2-羟基苯基)亚甲基二硫代氨基甲酸酯;R=H, Me或Br)在空气中与MnII (O2CMe)2·4H2O或[MnIII(acac)3]在乙醇介质中处理后,得到[MnL(O2CMe)]或[MnL(acac)] (acac=乙酰丙酮,L=L3或L4)类型的锰(III)配合物。锰(IV)配合物在冷冻二甲基甲酰胺(dmf)-甲醇溶液中的EPR谱分别在< g >≈4·0和≈2·0处表现为弱信号和强信号,表明存在较小的零场分裂。< g >≈2·0表现出超细(55Mn)线和禁线。在DMF中扫描的循环伏安图显示出可逆和准可逆的MnIV-MnIII偶对,其e2980值受水杨基苯基环上r取代基的电子效应和与碳原子结合的硫代基团的电子效应的显著影响。r -取代基的HammettσP值与e2980值呈线性相关。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
Ligand control on the synthesis and redox aspects of mononuclear manganese-(III) and -(IV) complexes with tridentate ONS-coordination
MnCl2·4H2O reacts with benzohydroxamic acid (BHAH2) in aqueous/non-aqueous solution (alkaline) forming manganese(IV) complexes of the type (PPh4)2[Mn(BHA)3]·3H2O. Its IR data suggest the hydroximato mode of coordination (O, O). This complex in frozen solution exhibits axial spectra with strong zero field splitting giving rise to ag≈4 signal which is more intense than that forg≈2. The solid, however, shows rhombic spectra. A probable reason for this difference is assigned. Trifunctional (ONS) Schiff bases H2L1 and H2L2 (5-R-salicylaldehyde thiosemicarbazone and 5-R-salicyl aldehyde-4-phenyl thiosemicarbazone, respectively; R=H, Me or Br) furnish Mn(IV) complexes of the type [MnL2](L=L1 or L2), whereas H2L3 and H2L4 (H2L3=S-methyl 3-(5-R-2-hydroxyphenyl) methylene dithiocarbazate; H2L4=S-benzyl 3-(5-R-2-hydroxyphenyl) methylene dithiocarbazate; R=H, Me or Br) afford manganese(III) complexes of the type [MnL(O2CMe)] or [MnL(acac)] (acac=acetylacetonate, L=L3 or L4), when treated with MnII (O2CMe)2·4H2O or [MnIII(acac)3] in ethanol medium in air. The EPR spectra of the manganese(IV) complexes in frozen dimethyl formamide (dmf)-methanol solution show weak and strong signals at 〈g〉≈4·0 and ≈2·0 respectively, implying a small zero field splitting. The 〈g〉≈2·0 shows hyperfine (55Mn) as well as forbidden lines. Cyclic voltammograms of these complexes scanned in DMF show reversible and quasi-reversible MnIV-MnIII couple, theE2980 values of which are significantly affected by the electronic effects of the R-substituents in the salicyl phenyl ring and those attached to the carbon atom bound to the thiolate functionality of the ligands. The HammettσP values of the R-substituents are linearly correlated with theE2980 values.
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