Bistability of the proposed [(phenanthroline)2FeII/III–(terephthalate)–CoIII/II(phenanthroline)2]3+ binuclear complex, arising from intramolecular FeII/III ↔ CoIII/II charge transfer, is investigated based on energetics, geometries, atomic charges, electric polarizabilities, and IR and UV-Vis spectra obtained computationally at (TD)DFT-B3LYP/LANL2DZ level of theory. Two distinct stable states are obtained which have different characteristics, including structures, charge distributions, and spectroscopic properties. Also, the well-defined first-order saddle point obtained between these two states using the QST3 search method, having a 1.182 eV activation (barrier) energy for the FeIICoIII → FeIIICoII reaction, furthermore approves bistability in this complex. This value of activation energy suggests that switching between the two charge distribution states FeII–CoIII and FeIII–CoII in this complex may be induced by electric field and/or infrared radiation, and thus, it can be candidate as an infrared radiation- or electric field-driven molecular two-state switch.

中文翻译：

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[(菲咯啉)2FeII/III-(对苯二甲酸酯)-CoIII/II(菲咯啉)2]3+双核配合物的计算研究

由分子内 FeII/III ↔ CoIII/II 电荷转移产生的 [(phenanthroline)2FeII/III-(terephthalate)-CoIII/II(phenanthroline)2]3+ 双核复合物的双稳定性基于能量学、几何学、在 (TD)DFT-B3LYP/LANL2DZ 理论水平通过计算获得的原子电荷、电极化率以及 IR 和 UV-Vis 光谱。获得了两种不同的稳定状态，它们具有不同的特性，包括结构、电荷分布和光谱特性。此外，使用 QST3 搜索方法在这两种状态之间获得明确定义的一阶鞍点，FeIICoIII → FeIIICoII 反应的激活（势垒）能量为 1.182 eV，进一步证实了该复合物中的双稳态。