Co–NC–W and Fe–NC–W Electron‐Transfer Channels for Thermal Bistability in Trimetallic {Fe₆Co₃[W(CN)₈]₆} Cyanido‐Bridged Cluster

Abstract

The design and construction of switchable materials attracts tremendous interest owing to the potential in information storing and processing or molecular sensing. [1][2][3][4] The archetypal examples involve a diversity of Fe II -, [5,6] Fe III - [7] or Co IIbased [8][9][10] spin-crossover (SCO) compounds, Co III/II -catecholate/semiquinone systems, [1,11] as well as d-d bimetallic and sd-d trimetallic cyanide-bridged systems revealing chargetransfer-induced spin transitions (CTIST). [12][13][14][15][16][17][18] Some of these compounds, for example Prussian blue analogues, are particularly promising from the point of view of photoswitching between nonmagnetic and magnetized (that is, T B , T C ) states, owing to magnetic coupling through molecular bridges in discrete species [14,15] and extended networks. [17,18] Such bistability also emerged in the magnetochemistry of octacyanidometalates, exploiting metal-to-metal electron transfer in HS Co II L[W V (CN) 8 ] 3À (L = pyrimidine, 4-methylpyridine) [19,20] or canonical SCO in Fe II L[Nb IV (CN) 8 ] 4À extended networks [21] (L = 4-pyridinealdoxime). A magnetic hysteresis loop with a coercivity of 1-3 T were observed in an optically excited low-temperature metastable phase.

Dynamic molecular crystals with switchable physical properties

“…5a) 29 Charge transfer coupled with spin transition has also been observed in several other cyanide-bridged heterobimetallic complexes [79][80] . In particular, unusual charge transfer was observed in a trimetallic cyanide-bridged cluster, {Co II 3 Fe II 6 [W V (CN) 8 ] 6 (MeOH) 24 }·xMeOH (Fig.…”

“…In particular, unusual charge transfer was observed in a trimetallic cyanide-bridged cluster, {Co II 3 Fe II 6 [W V (CN) 8 ] 6 (MeOH) 24 }·xMeOH (Fig. 5b) 80 , which has two active electron-transfer channels. One is the transition W IV ( (HT phase).…”

FeII Spin‐Crossover Phenomenon in the Pentadecanuclear {Fe9[Re(CN)8]6} Spherical Cluster

“…This selective spin-crossover effect was achieved by rational design based on our previous results with the analogous {Fe 9 W 6 } and {Fe 6 Co 3 W 6 } clusters. [41,42] Our molecule potentially opens the way for a new class of SCO polynuclear systems. The challenge now is to induce the SCO effect on external Fe sites of a cluster core, which may be achieved by the coordination of appropriate N-donor ligands to replace labile, coordinated solvent molecules, as was reported for other members of the family of {M 9 M' 6 } clusters.…”

“…[34] Among such materials, bimetallic [M(CN) 8 ]-based clusters have great potential, [35] as demonstrated by a family of {M 9 M' 6 } pentadecanuclear clusters {M II 9 [M' V (CN) 8 ] 6 (MeOH) 24 } (M= 3d metal; M ' = Mo, W; MeOH = methanol) which show a diverse range of magnetic functionalities, including high spin, [36][37][38] SMM, [39,40] and thermally induced charge transfer. [41,42] In this regard, the application of the spin-crossover (SCO) effect to polynuclear molecules is rare. SCO was broadly investigated for mononuclear complexes, based mainly on the Fe II ion, [43,44] and coordination polymers offering efficient intramolecular interactions giving thermal hysteresis loops, crucial for applications such as memory devices.…”

“…Figure 1 and Table 1 and Figures S2-S3 and Tables S1-S3 in the Supporting Information). [36][37][38][39][40][41][42] This molecule comprises one [Fe II The average FeÀN/O bond lengths at high (1 HT ) and low temperature (1 LT ) are given in Table 1. In 1 HT , the average Fe À N distance for Fe1 is close to 2.06 , whereas for the Fe2-Fe5 centers the mean lengths of Fe À N/O bonds are in the range 2.13-2.14 .…”