67368-93-8Relevant articles and documents
Linkage Isomers of 4-Methylimidazolate Mn(II) Porphyrinates: Hindered or Unhindered?
Zhao, Jianping,Qian, Fei,Guo, Wenping,Li, Jianfeng,Lin, Zeyuan
, p. 7465 - 7474 (2021/05/26)
Three different manganese(II) porphyrins have been exploited to react with 4-methylimidazolate (4-MeIm-), and the five-coordinate products are characterized by ultraviolet-visible, single-crystal X-ray, and electronic paramagnetic resonance spectroscopies. Interestingly, 4-MeIm- is found to bond to the metal center through either of the two N atoms (N1 or N3), which yielded two linkage isomers with either an unhindered or a hindered ligand conformation, respectively. Investigations revealed it is the large metal out-of-plane displacements (Δ24 and Δ4 ≥ 0.59 ?) that have rendered the equivalence of two isomers with a small energy difference (5.2-8.3 kJ/mol). The nonbonded intra- and intermolecular interactions thus become crucial factors in the balance of linkage isomerization. All of the products in both solution and solid states show the same characteristic resonances of high-spin Mn(II) (S = 5/2) with g⊥ ≈ 5.9 and g⊥ ≈ 2.0 at 4 K, consistent with the weak effects of the axial ligand on core conformation and metal electronic configurations. Zero-field splitting parameters obtained through simulations are also reported.
Efficient and selective oxidation of tertiary benzylic C[sbnd]H bonds with O2 catalyzed by metalloporphyrins under mild and solvent-free conditions
Hu, Meng-Yun,Liu, Lei,Qi, Bei,She, Yuan-Bin,Shen, Hai-Min,Ye, Hong-Liang
, (2020/05/19)
The direct and efficient oxidation of tertiary benzylic C[sbnd]H bonds to alcohols with O2 was accomplished in the presence of metalloporphyrins as catalysts under solvent-free and additive-free conditions. Based on effective inhibition on the unselective autoxidation and deep oxidation, systematical investigation on the effects of porphyrin ligands and metal centers, and apparent kinetics study, the oxidation system employing porphyrin manganese(II) (T(2,3,6-triCl)PPMn) with bulkier substituents as catalyst, was regarded as the most promising and efficient one. For the typical substrate, the conversion of cumene could reach up to 57.6% with the selectivity of 70.5% toward alcohol, both of them being higher than the current documents under similar conditions. The superiority of T(2,3,6-triCl)PPMn was mainly attributed to its bulkier substituent groups preventing metalloporphyrins from oxidative degradation, its planar structure favoring the interaction between central metal with reactants, and the high efficiency of Mn(II) in the catalytic transformation of hydroperoxides to alcohols.
Investigation by pulse radiolysis of the redox transformations of manganese tetra(n-tolyl)porphyrin and the effect of molecular oxygen on them
Revina,Volod'ko,Radyushkina
, p. 1156 - 1162 (2008/10/08)
Pulse radiolysis has been used to investigate the intermediate stages of the radiolytic transformations of Mn(III)TTP in acetonitrile and the effect of oxygen upon them. It is shown that in the initial stages Mn(III)TTP reacts with the anion radicals CH3CN-· and O2-· to give the complexes Mn(III)TTP...CH3CN-· and Mn(III)TTP...O2-· respectively. Mn(II)TTP is formed with a rate constant k = (4.0 ± 0.5) × 104 sec-1 as a result of electron transfer within the complex Mn(III)TTP...CH3CN-·. The electrochemical or radiolytic reduction of Mn(III)TTP in the presence of oxygen gives the complexes Mn(II)TTP...O2, Mn(III)TTP...O2-· and Mn(IV)TTP...O22- in equilibrium with one another.
