Reversible Thermally and Photoinduced Electron Transfer in a Cyano‐Bridged {Fe₂Co₂} Square Complex

Abstract

4 pagesInternational audienceFlip to be square: Structural, spectroscopic, magnetic, and photomagnetic studies conclusively demonstrate that a tetranuclear cyanometalate {Fe2Co2} complex undergoes reversible thermally and light-induced changes in optical and magnetic properties. This instability is induced by an intramolecular electron transfer, as oberved in three-dimensional Co/Fe Prussian blue compounds (see picture)

Thermochromic and Photoresponsive Cyanometalate Fe/Co Squares: Toward Control of the Electron Transfer Temperature

“…244 and 230 K for 2 and 3, respectively ( Figures S24 and S25). These values are significantly higher than found for {[(Tp*)Fe(CN) 3 ] 2 [Co-(bpy) 2 ] 2 [OTf] 2 } (4; T 1/2 = 177 K), 8 which exhibits a first-order phase transition between the low and high temperature diamagnetic and paramagnetic states, respectively. Interestingly, complexes 2 and 3 display quantitatively different behavior than Figure 7.…”

“…At high temperatures (240 K) compounds 2 and 3 are brown, while at lower ones both adopt a green appearance at 100 and 79 K, respectively. Based on these observations and previous reports for structurally related complexes 8,11 it can be concluded that thermally-induced electron transfer readily converts {Fe II LS (μ-CN)Co III LS } into {Fe III LS (μ-CN)Co II HS } units in both 2 and 3. Unlike previous reports, the average Co−N distances for 2 and 3 ( (Table 2).…”

“…We now describe the magnetic and optical behavior of these two {Fe 2 Co 2 } complexes and compare their properties to others assembled from different pyrazolylborate building blocks. 8,11 ■ EXPERIMENTAL SECTION Materials. The preparation of potassium hydridotris (3-methylpyrazol-1-yl) ,7.26;N,25.22.…”

“…We prepared a new building block, [(Tp Me )Fe III (CN) 3 ] − , where Tp Me = hydridotris(3-methylpyrazol-1-yl)borate, 17 with the expectation that it would possess intermediate steric and electronic donor properties in comparison to those seen for Tp and Tp* analogues. 8,11,17 To further explore solid state interactions, which may also tune the temperature-and lightdependent properties, we prepared two anion-substituted {(Tp Me )Fe(CN) 3 ] 2 [Co(bpy) 2 ] 2 [X] 2 } squares. We now describe the magnetic and optical behavior of these two {Fe 2 Co 2 } complexes and compare their properties to others assembled from different pyrazolylborate building blocks.…”

Cyanide‐Bridged Molecular Squares – The Building Units of Prussian Blue

“…[47] In 2010, the same group published a paper reporting the ob-servation of this behavior in a cyanide-bridged molecular square. [48] It should be noted that all previously reported cases of the phenomenon, in molecular and bulk species, have shown one-step transitions. However, the Oshio group recently reported the first example of an ETCST-active complex that showed two-step behavior, and a metastable intermediate state.…”