Stereospecific assembly of chiral heterometallic dinuclear (3d - 4f) complexes

用[Ln(HfAc)3(H2O)2](Ln(Ⅲ)=Y，NdLu)与IM-2py(2-(2-pyridyl)-4，4，5，5-tetramethyl-4，5-dihydro-1H-imidazolyl-1-oxyl)反应，合成了一系列新型的稀土或稀土自由基配合物[Ln(HfAc)3(Im-2py)]。用X-射线衍射法测定了Sm、Gd、Dy、Er和Yb配合物的分子结构，确定了它们的分子结构为双帽三方吡咯。[Gd(HFAc)3(IM-2py)]的磁化率数据表明，Gd-IM-2py相互作用是弱反铁磁性的，交换耦合常数J=-3.00 cm-1，与Gd(III)-硝基氮氧化物的铁磁相互作用相反。发现IM-2py的n-π*跃迁与强度增强和振动结构有关，向较低的频率移动。Eu(III)和Tb(III)的发光测量表明，IM-2py(SOMOπ*)→Ln(III)(4f))的能量传递是发射猝灭的结果，这取决于Ln(III)中心和IM-2py中激发能级的能隙。这些结果表明，金属-自由基相互作用在磁相互作用中很弱，但在能量转移中相对较强。

The treatment of [Ln(hfac)3(H2O)2] (Ln(III) = Y, Nd - Lu) and IM-2py (2-(2-pyridyl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazolyl-1-oxyl) readily gave a series of the novel rare earth or lanthanide radical complexes [Ln(hfac)3(IM-2py)]. The molecular structures of the Sm, Gd, Dy, Er and Yb complexes have been determined to be bis capped trigonal pyrism(TPRS) by the X-ray diffraction. The magnetic susceptibility data for [Gd(hfac)3(IM-2py)] show that the Gd-IM-2py interaction is weakly antiferromagnetic with an exchange coupling constant J = -3.00 cm-1 in contrast to the ferromagnetic interaction in the Gd(III)-nitronyl nitroxide complexes. The n-π* transition of the IM-2py is found to shift to the lower frequency associated with intensity enhancement and vibronic structure. The luminescence measurement of the Eu(III) and Tb(III) demonstrated the energy transfers for the IM-2py(SOMO π*) → Ln(III)(4f) as a result of the emission quenching which depends on the energy gap of the excited levels in Ln(III) centers and IM-2py. These results reveal that the metal-radical interactions are very weak in the magnetic interaction but are relatively strong in the energy transfer.