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Sudies on Structural Chemistry of Neptunyl Complexes by ^<237>Np Mossbauer spectroscopy.

Research Project

Project/Area Number 15550056
Research Category

Grant-in-Aid for Scientific Research (C)

Allocation TypeSingle-year Grants
Section一般
Research Field Inorganic chemistry
Research InstitutionToho University

Principal Investigator

TAKEDA Masuo  Toho University, Faculty of Science, Professor, 理学部, 教授 (80011633)

Co-Investigator(Kenkyū-buntansha) TAKAHASHI Masashi  Toho University, Faculty of Science, Professor, 理学部, 教授 (30171523)
KITAZAWA Takafumi  Toho University, Faculty of Science, Associate Professor, 理学部, 助教授 (60246767)
NAKADA Masami  Japan Atomic Energy Agency, Nuclear Science and Engineering Directorate, Researcher, 原子力基礎工学研究部門, 研究員 (60370441)
Project Period (FY) 2003 – 2005
Project Status Completed (Fiscal Year 2005)
Budget Amount *help
¥3,800,000 (Direct Cost: ¥3,800,000)
Fiscal Year 2005: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 2004: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 2003: ¥2,800,000 (Direct Cost: ¥2,800,000)
Keywords^<237>Np Mossbauer spectroscopy / neptunyl(VI) complex / chemical bonding / uranyl(VI) complex / nitrogen-ligating ligand / pyridine complex / Schiff base complex / macrocvclic complex / ウラニル(VI)錯体 / アセチルアセトン錯体 / ネプツニウム / メスバウアー分光 / ビピリジン錯体 / ^<237>Np
Research Abstract

The aim of this research is to obtain the information on the chemical bonding in the actinide compounds through the ^<237>Np Mossbauer spectroscopic study of neptunyl(VI) complexes containing nitrogen-containing ligands. Mossbauer parameters of the pyridine complex [NpO_2(acac)_2py] and the oxalate NpC_2O_4・3H_2O, both having the pentagonal bipyramidal structure, are compared. The value of isomer shift of [NpO_2(acac)_2py] having a nitrogen donor atom is larger than that of NpC_2O_4・3H_2O, suggesting that the nitrogen atom donates more electrons to the Np 5f orbitals than the oxygen atoms do. The isomer shift of [NpO_2(NO_3)_2(2,2'-bpy)] is larger than that of [NpO_2(acac)_2py], indicating that the increase in the coordination number from 7 (the latter) to 8 (the former) causes the decrease in the contribution of 7s electron. These results show that the electrons from the coordinating nitrogen atom are donated to 5f orbitals rather than 7s one, being in good contrast to the lanthanide complexes where the electrons are directly accommodated in 6s orbital.
Synthetic investigations are also carried out to develop the nitrogen-ligating actinyl(VI) complexes using uranyl(VI) in order to strengthen the Mossbauer spectroscopic data. Several [UO_2(acac)py] derivatives, [UO_2(acac)(4-R-py)] (R=Me,Et,'Bu,CN,Cl,NMe_2) are prepared and their structures are determined. A good correlation between U-N and U=O distances are observed. Six macrocyclic N_6-coordinating Schiff base UO_2 complexes derived from pyrroledicarboaldehyde and diamines are prepared and two of the structurally characterized. Four acyclic Schiff base UO_2 complexes including a heterobinuclear Cu^<2+>-UO_2 complex are also obtained and their structures are determined.

Report

(4 results)
  • 2005 Annual Research Report   Final Research Report Summary
  • 2004 Annual Research Report
  • 2003 Annual Research Report

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Published: 2003-04-01   Modified: 2016-04-21  

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