稀土配合物(RE(DBM)_(3),RE=Nd、Sm、Gd)分子内能量弛豫过程的光声光谱研究

A Study of Intramolecular Energy Relaxation Processes of Rare Earth Complexes(RE(DBM)_(3),RE=Nd,Sm,Gd)

利用光声振幅谱和位相谱对稀土配合物(Nd(DBM)3、 Sm(DBM)3和Gd(DBM)3分子内弛豫过程进行了研究。Sm(DBM)3、 Gd(DBM)3和Nd(DBM)3的配体π-π*跃迁的光声振幅强度依次增强，而Gd、 Sm和Nd的配合物在配体吸收波段内位相依次减小，反映分子内的弛豫过程。对于Gd(DBM)3，配体最低三重态能量不能传递到中心离子4f激发态能级上而直接弛豫回基态；对于Sm(DBM)3和Nd(DBM)3，配体三重态能量有效地传递到中心离子上， Nd3+各能级间隔小且相互重叠，激发态能量几乎全部以无辐射跃迁回基态； Sm3+为荧光离子，激发态上的部分能量以荧光形式发射。由此并结合荧光光谱的结果建立了分子内能量弛豫模型。

Intramolecular energy relaxation processes of rare earth complexes (RE(DBM)3, RE=Nd, Sm, Gd) have been studied by the photoacoustic amplitude and phase spectra. The amplitude intensities of π-π* transition of ligand in Sm(DBM)3, Gd(DBM)3 and Nd(DBM)3 increase gradually, but the phase data within the region of ligand absorption in the complexes of Gd, Sm and Nd decrease gradually, which shows intramolecular energy relaxation processes. For Gd(DBM)3 energy can't transfer from the lowest triplet state of ligand to the 4f excited state of Gd3+, the triplet state relaxes to the ground state directly. For Sm(DBM)3 and Nd(DBM)3 energy can effectively transfer from the lowest triplet state of ligands to the 4f excited states of the central ions. The 4f excited states of Nd3+ almost relax nonradiatively to the ground state because the gap among the levels in Nd3+ is small. The energy of excited state in Sm3+ radiates partly because Sm3+ is a fluorescent ion. Combined these with the results of fluorescence spectra the models of intramolecular energy relaxation processes are established.