Thermodynamic Study on Dioxygen Binding of Diiron(II) and Dicobalt(II) Complexes Containing Various Dinucleating Ligands

• Hideki Sugimoto

  Department of Chemistry, Faculty of Science, Kanazawa UniversityKanazawa 920-1192

• Toshihiko Nagayama

  Department of Chemistry, Faculty of Science, Kanazawa UniversityKanazawa 920-1192

• Sachihito Maruyama

  Department of Chemistry, Faculty of Science, Kanazawa UniversityKanazawa 920-1192

• Shuhei Fujinami

  Department of Chemistry, Faculty of Science, Kanazawa UniversityKanazawa 920-1192

• Yuichi Yasuda

  Department of Chemistry, Faculty of Science, Kanazawa UniversityKanazawa 920-1192

• Masatatsu Suzuki

  Department of Chemistry, Faculty of Science, Kanazawa UniversityKanazawa 920-1192

• Akira Uehara

  Department of Chemistry, Faculty of Science, Kanazawa UniversityKanazawa 920-1192

抄録

A new dinucleating ligand containing a sterically bulky imidazolyl group, Ph-Htidp (N,N,N′,N′-tetrakis[(1-methyl-4,5-diphenyl-2-imidazolyl)methyl]-1,3-diamino-2-propanol), and its μ-alkoxo-diiron(II) complexes [Fe2(Ph-tidp)(RCO2)](ClO4)2, (RCO2 = C6H5CO2 (1), C6F5CO2 (2), CF3CO2 (3), and C2H5CO2 (4)), were synthesized. The structure of complex 1 was determined by X-ray crystallography. Complex 1 crystallizes in the monoclinic space group P21/c with a = 13.464(2), b = 19.223(4), c = 31.358(4) Å, β = 92.84(2)°, and Z = 4. The complex has a doubly-bridged structure with μ-alkoxo of Ph-tidp and μ-benzoate; the two iron centers have a distorted five-coordinate structure with N3O2 donor set. All the complexes showed fairly good reversible oxygenation below −30 °C in CH2Cl2, which was monitored by UV-vis and NMR spectroscopies, and dioxygen up-take measurements. Introduction of 4,5-diphenyl substituents into 2-imidazolyl group stabilized the μ-peroxo diiron species against irreversible oxidation, just as introduction of 6-methyl substituent into 2-pyridyl group did. Phenyl substituents appear to weaken the electron donor ability of a dinucleating ligand to stabilize divalent oxidation state of iron and to form a hydrophobic cavity for a O2 binding site, which would suppress the irreversible oxidation and facilitate the reversible oxygenation. Dioxygen affinities of the Ph-tidp and Me4-tpdp diiron(II), and the tpdp and bpmp dicobalt(II) complexes were measured, [Fe2(Me4-tpdp)(RCO2)]2+ (RCO2 = C6H5CO2 and RCO2 = CF3CO2) and [Co2(L)(RCO2)]2+ (L = tpdp, RCO2 = CH3CO2, and L = bpmp, RCO2 = C6F5CO2, and CF3CO2), where Me4-tpdp, tpdp, and bpmp are N,N,N′,N′-tetrakis[(6-methyl-2-pyridyl)methyl]-1,3-diamino-2-propanolate, N,N,N′,N′-tetrakis(2-pyridylmethyl)-1,3-diamino-2-propanolate, and 2,6-bis[bis(2-pyridylmethyl)aminomethyl]-4-methylphenolate, respectively. Within a series of the Ph-tidp diiron(II) complexes, dioxygen affinity is well correlated with electron donor ability of bridging carboxylates (1 (C6H5CO2) > 2 (C6F5CO2) > 3 (CF3CO2)). In contrast to the above trend, dioxygen affinities of the Ph-tidp complexes are lower than those of the Me4-tpdp complexes, although electron donor abilities of the Me4-tpdp complexes are weaker than those of the Ph-tidp complexes. Significant enhancement of dioxygen affinity was observed for both iron and cobalt complexes with 2,6-bis(aminomethyl)phenolate bridging skeleton compared to the complexes with a 1,3-diamino-2-propanolate bridging one. Thermodynamic study suggested that the observed enhancement is mainly attributable to a favorable entropy effect along with a steric effect.

収録刊行物

• Bulletin of the Chemical Society of Japan

  Bulletin of the Chemical Society of Japan 71 (10), 2267-2279, 1998-10-01

  Oxford University Press (OUP)

キーワード

• General Chemistry

詳細情報

• CRID: 1360002219104511232
• NII論文ID: 130004149935
• DOI: 10.1246/bcsj.71.2267
• ISSN: 13480634
• ISSN: 00092673
• Web Site: https://academic.oup.com/bcsj/article-pdf/71/10/2267/56196737/bcsj.71.2267.pdf
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