Constructions of external stimuli-induced electron transfer systems

杂价异质金属配合物是表现出熵驱动电子转移的系统的良好候选者，因为电子转移伴随着相对较大的结构变化。本研究制备了具有不同取代基的四核分子方阵[Fe^<III>_2Co^<II>_2(CN)_6(L1)_2(L2)_4] （L1和L2为多齿配体）。分子方阵表现出分子内电子热转移诱导的HS ([Fe^<III>_<LS>(S=1/2)Co^<II>_<HS>(S=3/2)])和LS ([Fe^<II>_<LS> (S=0)Co^<III>_<LS>(S=0)])态自旋跃迁。分子内的电子转移可以通过化学修饰来控制，其中配体上的给电子基团修饰了金属离子的氧化还原电位，从而导致自旋转变温度的微调。此外，氰化物末端氮原子的质子化导致了质子诱导的LS态和HS态之间的自旋跃迁。

Mixed-valence heterometal complexes are good candidates for a system exhibiting entropy-driven electron transfer, because the electron transfer associates relatively large structural changes. In this study, tetranuclear molecular squares with various substituent groups, [Fe^<III>_2Co^<II>_2(CN)_6(L1)_2(L2)_4] (L1 and L2 are multi-dentate ligands), were prepared. The molecular squares exhibited spin transition between HS ([Fe^<III>_<LS>(S=1/2)Co^<II>_<HS>(S=3/2)]) and LS ([Fe^<II>_<LS> (S=0)Co^<III>_<LS>(S=0)]) states induced by thermal intramolecular electron transfer. The intramolecular electron transfer can be controlled by chemical modification, where electron donating groups on the ligands modified the redox potentials of metal ions, leading to fine tuning of spin transition temperatures. In addition, protonation to terminal nitrogen atoms of cyanide lead to a novel protonation-induced spin transition between LS and HS states.