The paramagnetic NMR study of saddled metalloporphyrins- 1. Characterization of Saddled Nickel(III) Porphyrin Cation Radical :The NMR Explicative Model for Ferromagnetically Coupled Metalloporphyrin Radical. 2. Saddle-shaped six-coordinate iron(III) porphyrin complex with unusual intermediate-spin electronic structure

• Main Authors: Chiao-Han Ting, 丁橋瀚
• Format: Others
• Language: zh-TW
• Published: 2014
• Online Access: http://ndltd.ncl.edu.tw/handle/81564703375984847254

博士 === 國立中興大學 === 化學系所 === 102 === The two-electron oxidized NiII(OETPP)( 2,3,7,8,12,13,17,18-Octaethyl-5,10,15,20-tetraphenylporphyrin), which had merely been generated by eletrooxidation, is first chemically synthesized by addition of one equiv. of Br2 in benzene solution. The detailed magnetic properties are well characterized by EPR zero-field splitting (D), paramagnetic NMR analyses and DFT calculations to elucidate the electron configuration from two plausible states with similar spin distributions in ring macrocycle to be Ni(III) low-spin (dxy2dxz,yz4dz21dx2-y20, S =1/2) orthogonally coupled with a1u radical to form a triplet state. The spin state of iron(III) porphyrin complexes could be modulated by the axial ligand and the deformation of macrocycle ring. The 4-CNPy ligand, which acts as a weak base, has been reported to be the axial ligand in the [FeIII(OETPP)(4-CNPy)2]+ complex with pure intermediate-spin state (S = 3/2). However, the electronic configuration for this complex is controversial, there are four conjectures 4 in E the literatures, including 4 E (dxz,yz3dxy1dz21), 4 4 A1 (dxy2dxz,yz2dz21),(anti,dxy2dxz,yz2dz21dx2-y21a2u1) and A1 (anti,dxz,yz3 dxy1dz21dx2-y21a2u1). In our report, Density function theory (DFT) calculations combined with paramagnetic NMR analyses have shown the Fermi contact spin densities of 4E are more consistent with experimental data. Furthermore, through the decomposition energy composed of two fragments, containing iron porphyrin and axial cyanopyridines, the bonding interaction between iron-dxyand porphyrin-a1u orbitals stabilizes the intermediate spin electronic structure. Aside from the σ donating , the axial 4-CNPy also acts mainly as a π-donor instead of a π-acceptor.