TY - JOUR
T1 - Electronic structure of low-spin six-coordinate iron(III) meso-tetrapropylchlorin complexes
AU - Ikezaki, Akira
AU - Ono, Jyunpei
AU - Ohgo, Yoshiki
AU - Fukagawa, Mari
AU - Ikeue, Takahisa
AU - Nakamura, Mikio
N1 - Funding Information:
This work was supported by the Grant in Aid (No. 21750175 to AI and No. 22550157 to MN) for Scientific Research from Ministry of Education, Culture, Sports, Science and Technology, Japan. This work was also supported by the Research Promotion Grant from Toho University Graduate School of Medicine (No. 11-02 to AI). Thanks are due to the Research Center for Molecular-Scale Nanoscience, the Institute for Molecular Science (IMS), Okazaki, Japan and the Research Center for Materials with Integrated Properties, Faculty of Science, Toho University, Funabashi, Japan.
Publisher Copyright:
Copyright © 2014 World Scientific Publishing Company.
PY - 2014/8
Y1 - 2014/8
N2 - Low-spin iron(III) tetrapropylchlorins [Fe(TnPrC)L2]± (L = HIm, 1-MeIm, DMAP, CN-, 4-CNPy, tBuNC) adopt the dxy-type ground state regardless of the nature of axial ligands. Among the complexes examined, [Fe(TnPrC)(tBuNC)2]+ has shown quite unique spectroscopic properties as described below. (1) 1H NMR signals were extremely broad as compared with those of other complexes. In particular, 5,20-CH2(α) signal was too broad to detect. (2) No signals except Cγ were observed in 13C NMR spectra. (3) Tetragonal splitting parameter (|Δ|) estimated by the EPR g values at 4.2 K reached as much as 12.4 λ, which is the largest |Δ| value among all the low-spin iron(III) porphyrins and porphyrinoids reported previously. On the basis of these results, we have concluded that [Fe(TnPrC) (tBuNC)2]+ adopts the low-spin iron(III) with (dxz, dyz)4(dxy)1 electronic ground state at 4.2-30 K where the EPR spectra are taken, while it should be expressed as the low-spin Fe(II) chlorin π-radical cation [FeII(TnPrC•)(tBuNC)2]+ at ambient temperature where the NMR spectra are taken.
AB - Low-spin iron(III) tetrapropylchlorins [Fe(TnPrC)L2]± (L = HIm, 1-MeIm, DMAP, CN-, 4-CNPy, tBuNC) adopt the dxy-type ground state regardless of the nature of axial ligands. Among the complexes examined, [Fe(TnPrC)(tBuNC)2]+ has shown quite unique spectroscopic properties as described below. (1) 1H NMR signals were extremely broad as compared with those of other complexes. In particular, 5,20-CH2(α) signal was too broad to detect. (2) No signals except Cγ were observed in 13C NMR spectra. (3) Tetragonal splitting parameter (|Δ|) estimated by the EPR g values at 4.2 K reached as much as 12.4 λ, which is the largest |Δ| value among all the low-spin iron(III) porphyrins and porphyrinoids reported previously. On the basis of these results, we have concluded that [Fe(TnPrC) (tBuNC)2]+ adopts the low-spin iron(III) with (dxz, dyz)4(dxy)1 electronic ground state at 4.2-30 K where the EPR spectra are taken, while it should be expressed as the low-spin Fe(II) chlorin π-radical cation [FeII(TnPrC•)(tBuNC)2]+ at ambient temperature where the NMR spectra are taken.
KW - C NMR
KW - EPR
KW - Electronic structure
KW - H NMR
KW - Iron chlorins
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U2 - 10.1142/S1088424614500576
DO - 10.1142/S1088424614500576
M3 - Article
AN - SCOPUS:84908660275
SN - 1088-4246
VL - 18
SP - 778
EP - 791
JO - Journal of Porphyrins and Phthalocyanines
JF - Journal of Porphyrins and Phthalocyanines
ER -