The design of molecule-based systems displaying tunable optical and/or magnetic properties under external stimuli received a great deal of attention in the past few years. This interest is driven by the potential applications in high-performance molecule-based electronics. As an example, 3D Fe/Co Prussian blue compounds exhibit a concomitant change in magnetic and optical properties due to a temperature- or light-induced metal-to-metal electron transfer (ET). The foregoing remarkable properties in Prussian blues prompted us to design soluble molecular fragments of these coordination networks through a rational building-block approach in order to mimic their properties on a single molecule.[1-4] With a judicious choice of the ligands for metal ion molecular precursors, we prepared a octanuclear,[1] tetranuclear[2] and dinuclear[3,4] cyanido-bridged Fe/Co complexes. In the solid state, while an intramolecular ET is observed for the [Co4Fe4][1] and [Co2Fe2][2] complexes, the Co ion of the dinuclear complex[3] exhibits a spin crossover (SCO) involving a [FeIIILS-CN-CoIILS] ground state and a thermally populated [FeIIILS-CN-CoIIHS] state. To our knowledge, this compound is the only example of a heterobimetallic complex exhibiting a CoII SCO. In solution (DMSO), we observed important optical and magnetic changes which are induced by an intramolecular metal-to-metal ET triggered and modulated by a controlled protonation of the complex or by temperature. Rationalizing the ET properties of these [ConFen] complexes, we were able to observe (by combined structural, spectroscopic, magnetic and photomagnetic studies) a thermally and light induced metal-to-metal electron transfer for the first time in a new dinuclear complex.[4] References: [1] D. Li et al., J. Am. Chem. Soc., 2008, 130, 252-258. [2] Y. Zhang et al., Angew. Chem. Int. Ed., 2010, 49, 3752-3756 ; Siretanu, et al., Chem. Eur. J., 2011, 17, 11704-11708 ; Zhang, Y.-Z. et al. J. Am. Chem. Soc. DOI:10.1021/ja508280n. [3] I.-R. Jeon, et al., Chem. Sci., 2013, 4, 2463-2470. [4] E. Koumousi, et al., J. Am. Chem. Soc., DOI: 10.1021/ja508094h

Optical and magnetic molecular switches

249th National Meeting (2015)

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