论文部分内容阅读
本文测定了15个一水稀土乙酰丙酮络合物的激光拉曼和红外光谱。结果表明在401、415cm~(-1)附近的拉曼谱带对不同稀土离子表现敏感。它们随原子序数变化呈现“四分组效应”。这是第一次在振动光谱中观察到的镧系递变规律。该系列络合物的振动频率变化也符合镧系“斜W效应”规律。这些特征规律为确认401、415cm~(-1)附近谱带为M-O拉伸振动提供了极好的证据。从络合物M-O振动频率,近似地利用双原子分子关系式计算得到M-O拉伸振动的力常数,当进一步研究力常数与络合物稳定常数对数关系时,发现以Eu为交点得到轻、重稀土斜率显著不同的两条直线。重稀土乙酰丙酮络合物的稳定常数的对数变化很小,而力常数则有显著的变化,可见力常数是描述络合物的更敏感的结构参数。在红外光谱中,随着稀土金属离子与乙酰丙酮的络合,C=O基拉伸频率降低,这意味着络合时伴有电荷迁移发生。从C=O基和C(?)C基红外吸收随原子序数的变化表明,乙酰丙酮大环中,负电荷倾向非定域。虽然通常认为稀土乙酰丙酮络合物是离子型的,但实验结果表明,有一定的共价成份存在。
In this paper, laser Raman and IR spectra of 15 rare earth acetylacetonate complexes were measured. The results show that the Raman bands around 401 and 415 cm -1 are sensitive to different rare earth ions. They exhibit a “quartet effect” as the atomic number changes. This is the first observation of the lanthanide evolution in the vibrational spectrum. Variations of the vibrational frequencies of the series of complexes are also in accordance with the law of “oblique W effect” of lanthanide series. These characteristic laws provide excellent evidence for the confirmation of M-O tensile vibration in the vicinity of 401 and 415 cm -1. From the vibrational frequency of complex MO, the force constant of MO tensile vibration was calculated by using the relation of diatomic molecular approximation. When further studying the logarithm of the relationship between the force constant and the complex stability constant, Heavy Rare Earth slope significantly different from the two straight lines. The change of logarithm of the stability constant of heavy rare earth acetylacetone complex is very small, but the force constant is obviously changed. It can be seen that the force constant is the more sensitive structural parameter to describe the complex. In the infrared spectrum, the C = O group stretching frequency decreases with the complexation of the rare earth metal ions with acetylacetone, which means that charge transfer accompanied by the complexation occurs. The change of infrared absorption from C = O group and C (?) C group with the atomic number indicates that in the acetylacetone macrocycle, the negative charge tends to be non-localized. Although rare earth acetylacetone complexes are generally considered to be ionic, experimental results show that certain covalent components exist.