2005 Fiscal Year Final Research Report Summary
Synthesis and Properties of Iron(III) and Iron(II) Porphyrinates with Novel Electron Configuration and Magnetic Characteristics
| Project/Area Number |
16550061
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Inorganic chemistry
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| Research Institution | TOHO UNIVERSITY |
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Principal Investigator |
NAKAMURA Mikio Toho University, Department of Chemistry, School of Medicine, Professor, 医学部, 教授 (20112914)
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| Co-Investigator(Kenkyū-buntansha) |
OHGO Yoshiki Toho University, Department of Chemistry, School of Medicine, Assistant Professor, 医学部, 講師 (40287496)
IKEZAKI Akira Toho University, Department of Chemistry, School of Medicine, Research Associate, 医学部, 助手 (80297639)
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| Project Period (FY) |
2004 – 2005
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| Keywords | Porphyrin / Iron Complexes / Electron Configuration / Spin State / Spin Crossover / NMR Spectroscopy / EPR Spectroscopy / Mossbauer Spectroscopy |
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| Research Abstract |
Nonplanar deformation of porphyrin ring makes some specific metal-porphyrin interactions possible. As a result, the nonplanar porphyrin complexes could exhibit some characteristic electronic and magnetic properties that can not be observed in the corresponding planar complexes. In the present study, we have prepared a series of highly deformed meso-tetraalkylporphyrins(TRP) and octaethyltetraphenylporphyrin(OETPP) complexes and have examined the electronic structures and magnetic behaviors.
The intermediate-spin(S=3/2) state of iron(III) porphyrin complexes are stabilized by the axial ligands with weak field strength. Thus, we can rank the field-strength of the weak axial ligands on the basis of the pyrrole-H chemical shifts, since the upfield shift of the pyrrole-H directly correlates with the population of the intermediate-spin complex. We have determined the weakness of a wide variety of oxygen ligands as given below on the basis of the pyrrole-H chemical shifts of a series of planar
… More
, ruffled, and saddled porphyrin complexes.
4-MePyNO,3,5-Me_2PyNO>PyNO>4-ClPyNO>DMSO>DMF>MeOH>THF>Dioxane
We have also confirmed the presence of two types of intermediate-spin complexes with different electron configurations, (d_<xy>)^2(d_<xz>,d_<yz>)^2(d_z2))^1 and (d_<xz>,d_<yz>)^3(d_<xy>)^1(d_z2)^1, on the basis of the ^1H and ^<13>C chemical shifts of a wide variety of iron(III) porphyrin complexes.
Magnetic behaviors of iron(III) porphyrin complexes could be affected by the crystal packing. By the introduction of bulky groups at the 3,5-positions of meso-phenyl groups of OMTPP, we were able to prepare the crystals where each molecule is supposed to be loosely packed. The SQUID and Mossbauer measurements have revealed that these complexes actually exhibit spin-crossover phenomena in the solid state. We have also found the unprecedented example showing the spin-crossover process between S=5/2 and S=3/2 in five-coordinate highly saddled complexes at extremely low temperature.
The iron(III) porphyrinates carrying alkyl isocyanide always adopt the low-spin state with the (d_<xz>,d_<yz>)^4(d_<xy>)^1 electron configuration. In the present study, we have found for the first time that the alkyl isocyanide complexes of diazaporphyrin exhibit the low-spin state with the (d_<xy>)^2(d_<xz>,d_<yz>)^3 electron configuration. Since the alkyl isocynide ligands are frequently used as probes to reveal the electronic structures of naturally occurring heme proteins, the present results are quite useful to reveal the functions of heme proteins. Less
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