Valverde-Muñoz Francisco Javier, Seredyuk Maksym, Meneses-Sánchez Manuel, Muñoz M Carmen, Bartual-Murgui Carlos, Real José A
Departament de Química Inorgànica , Institut de Ciència Molecular (ICMol) , Universitat de València , Valencia , Spain . Email:
On leave from Department of Chemistry , Taras Shevchenko National University of Kyiv , 64/13, Volodymyrska Street , 01601 , Kyiv , Ukraine . Email:
Chem Sci. 2019 Feb 22;10(13):3807-3816. doi: 10.1039/c8sc05256e. eCollection 2019 Apr 7.
A multistable spin crossover (SCO) molecular alloy system [Fe M (Bu-im)(tren)](P As F) (M = Zn, Ni; (Bu-im)(tren) = tris(-butyl-imidazol(2-ethylamino))amine) has been synthesized and characterized. By controlling the composition of this isomorphous series, two cooperative thermally induced SCO events featuring distinct critical temperatures ( ) and hysteresis widths (Δ , memory) can be selected at will. The pristine derivative 100As ( = 0, = 1) displays a strong cooperative two-step SCO and two reversible structural phase transitions (PTs). The low temperature PT and the SCO occur synchronously involving conformational changes of the ligand's -butyl arms and two different arrangements of the AsF anions [1c = 174 K (Δ1c = 17 K), 2c = 191 K (Δ2c = 23 K) (scan rate 2 K min)]. The high-temperature PT takes place in the high-spin state domain and essentially involves rearrangement of the AsF anions [PTc = 275 K (ΔPTc = 16 K)]. This behavior strongly contrasts with that of the homologous 100P [ = 0, = 0] derivative where two separate cooperative one-step SCO can be selected by controlling the kinetics of the coupled PT at ambient pressure: (i) one at low temperatures, = 122 K (Δ = 9 K), for temperature scan rates (>1 K min) (memory channel A) where the structural modifications associated with PT are inhibited; (ii) the other centered at = 155 K (Δ = 41 K) for slower temperature scan rates ≤0.1 K min (memory channel B). These two SCO regimes of the 100P derivative transform reversibly into the two-step SCO of 100As upon application of hydrostatic pressure ( 0.1 GPa) denoting the subtle effect of internal chemical pressure on the SCO behavior. Precise control of AsF ↔ PF substitution, and hence of the PT kinetics, selectively selects the memory channel B of 100P when = 0 and ≈ 0.7. Meanwhile, substitution of Fe with Zn or Ni [ ≈ 0.2, = 0] favors the low temperature memory channel A at any scan rate. This intriguing interplay between PT, SCO and isomorphous substitution was monitored by single crystal and powder X-ray diffractometries, and magnetic and calorimetric measurements.
已合成并表征了一种多稳态自旋交叉（SCO）分子合金体系Feₘ(Bu-im)(tren)（M = Zn，Ni；(Bu-im)(tren) = 三（叔丁基咪唑（2-乙胺基））胺）。通过控制这个同构系列的组成，可以随意选择两个具有不同临界温度（Tc）和滞后宽度（ΔTc，记忆）的协同热诱导SCO事件。原始衍生物100As（x = 0，y = 1）显示出强烈的协同两步SCO和两个可逆的结构相变（PTs）。低温PT和SCO同步发生，涉及配体叔丁基臂的构象变化以及AsF₆阴离子的两种不同排列[1c = 174 K（Δ1c = 17 K），2c = 191 K（Δ2c = 23 K）（扫描速率2 K min⁻¹）]。高温PT发生在高自旋态域，主要涉及AsF₆阴离子的重排[PTc = 275 K（ΔPTc = 16 K）]。这种行为与同源的100P[x = 0，y = 0]衍生物形成强烈对比，在100P中，通过控制常压下耦合PT的动力学可以选择两个独立的协同一步SCO：（i）一个在低温下，Tc = 122 K（ΔTc = 9 K），对于温度扫描速率（>1 K min⁻¹）（记忆通道A），其中与PT相关的结构修饰受到抑制；（ii）另一个以Tc = 155 K（ΔTc = 41 K）为中心，对于较慢的温度扫描速率≤0.1 K min⁻¹（记忆通道B）。100P衍生物的这两种SCO状态在施加静水压力（p > 0.1 GPa）时可逆地转变为100As的两步SCO，这表明内部化学压力对SCO行为有微妙影响。当x = 0且y ≈ 0.7时，精确控制AsF₆ ↔ PF₆取代，从而控制PT动力学，可选择性地选择100P的记忆通道B。同时，用Zn或Ni取代Fe[x ≈ 0.2，y = 0]在任何扫描速率下都有利于低温记忆通道A。通过单晶和粉末X射线衍射、磁性和量热测量监测了PT、SCO和同构取代之间这种有趣的相互作用。
Zotero 插件
