3d4f Heterobimetallic Dinuclear and Tetranuclear Complexes Involving Tetrathiafulvalene as Ligands: X-ray Structures and Magnetic and Photophysical Investigations

Six new 3d4f heterobimetallic dinuclear complexes, [(L1)­MLn­(hfac)3] [M = CuII, NiII; Ln = YIII, ErIII, YbIII; L1 = 4,5-bis­(propylthio)­tetrathiafulvalene-N,N′-phenylenebis­(salicylideneimine)
and hfac– = 1,1,1,5,5,5-hexafluoroacetylacetonate],
and one tetranuclear complex, [(L2)­Cu­(OH)­Er­(hfac)3]2 (where L2 = 4,5-bis­(propylthio)­tetrathiafulvalene-N,N′-phenyleneaminosalicylideneimine),
have been synthesized. All of the X-ray structures of the coordination
complexes have been resolved from single-crystal diffraction. A quantitative
magnetic approach has allowed one to determine the Cu–Ln ferromagnetic
interaction for GdIII (1.29 cm–1) and
TbIII (0.40 cm–1) and the antiferromagnetic
interaction for DyIII (−0.46 cm–1) and YbIII (−2.25 cm–1), while
in the case of ErIII, the magnetic interactions are negligible.
The UV–visible absorption properties have been studied in a
chloroform solution and rationalized by DFT and TD-DFT calculations.
Upon oxidation, intramolecular SOMO → LUMO (20800 cm–1) and SOMO–n → SOMO (11350 cm–1) charge transfers appear, while the HOMO →
LUMO charge transfers (20750 cm–1) disappear. The
reversibility of the oxidation has been confirmed by electrochemistry
and absorption properties upon the addition of a reducing agent. Irradiation
at the HOMO → LUMO charge-transfer energy of the dinuclear
complex [(L1)­NiY­(hfac)3] induces a ligand-centered fluorescence at 14450 cm–1.

本研究成功合成了6种新型3d4f异双金属双核配合物[(L1)MLn(hfac)₃]（其中M为CuII、NiII；Ln为YIII、ErIII、YbIII；L1为4,5-双(丙硫基)四硫富瓦烯-N,N′-亚苯基双(水杨醛亚胺)（4,5-bis(propylthio)tetrathiafulvalene-N,N′-phenylenebis(salicylideneimine)），hfac⁻为1,1,1,5,5,5-六氟乙酰丙酮根（1,1,1,5,5,5-hexafluoroacetylacetonate)），以及1种四核配合物[(L2)Cu(OH)Er(hfac)₃]₂（其中L2为4,5-双(丙硫基)四硫富瓦烯-N,N′-亚苯基氨基水杨醛亚胺（4,5-bis(propylthio)tetrathiafulvalene-N,N′-phenyleneaminosalicylideneimine)）。所有上述配位配合物的X射线晶体结构均通过单晶衍射法得以解析。通过定量磁学表征手段，我们得以确定：对于GdIII（1.29 cm⁻¹）与TbIII（0.40 cm⁻¹）体系，Cu-Ln间存在铁磁相互作用；对于DyIII（-0.46 cm⁻¹）与YbIII（-2.25 cm⁻¹）体系，Cu-Ln间为反铁磁相互作用；而ErIII体系的磁相互作用可忽略不计。本研究对该类配合物在氯仿溶液中的紫外-可见吸收性能开展了表征，并借助密度泛函理论（Density Functional Theory，DFT）与含时密度泛函理论（Time-Dependent Density Functional Theory，TD-DFT）计算对其光谱行为进行了合理化阐释。氧化过程中，体系出现分子内单电子占据分子轨道（Singly Occupied Molecular Orbital，SOMO）→最低未占据分子轨道（Lowest Unoccupied Molecular Orbital，LUMO）（20800 cm⁻¹）以及SOMO-n→SOMO（11350 cm⁻¹）的电荷转移过程，而最高占据分子轨道（Highest Occupied Molecular Orbital，HOMO）→LUMO（20750 cm⁻¹）的电荷转移过程则消失。通过电化学测试与加入还原剂后的吸收光谱变化，证实了该氧化过程的可逆性。在双核配合物[(L1)NiY(hfac)₃]的HOMO→LUMO电荷转移能级处进行辐照，可在14450 cm⁻¹处观测到配体中心荧光发射。