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

The aim of this research 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。[NpO_2（acac）_2py]和oxalate NpC_2O_4·3H_2O的Mossbauer参数，两者都具有五角形双金字塔结构， 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 Np5f orbitals than the oxygen atoms do。[NpO_2（NO_3）_2的异构体位移（2，2'-bpy）]大于[NpO_2（acac）_2py]，表示协调数的增加为7（拉丁文）至8（前）导致降解在7s电子的贡献中的作用，这些结果显示，从协调的硝酸原子中的电子被捐赠到5 f轨道比7s一个，与镧复合体形成良好的对比，使电子直接被安装在6个轨道上。合成研究也被用于开发硝基配体活性素（VI）复合体使用铀（VI），以加强莫斯鲍尔光谱学数据。[UO_2（acac）py]衍生物， [UO_2（acac）（4-R-py）] （R=Me，Et，'Bu，CN，Cl，NMe_2）已准备好并确定其结构。U-N和U=O距离之间有很好的联系。六大环N_6-协调Schiff基UO_2复合体从幽门螺杆菌和钻石中衍生出来，并有两个结构性特征化。Four acyclic Schiff base UO_2 complexes including a heterobinuclear Cu^&lt;2+\-UO_2 complex are also obtained and their structures are determined。

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.