School of Chemistry, The University of Sydney , Sydney, NSW 2006, Australia.
J Am Chem Soc. 2017 Jan 25;139(3):1330-1335. doi: 10.1021/jacs.6b12465. Epub 2017 Jan 13.
The spin crossover (SCO) phenomenon defines an elegant class of switchable materials that can show cooperative transitions when long-range elastic interactions are present. Such materials can show multistepped transitions, targeted both fundamentally and for expanded data storage applications, when antagonistic interactions (i.e., competing ferro- and antiferro-elastic interactions) drive concerted lattice distortions. To this end, a new SCO framework scaffold, [Fe(bztrz)(Pd(CN))]·n(guest) (bztrz = (E)-1-phenyl-N-(1,2,4-triazol-4-yl)methanimine, 1·n(guest)), has been prepared that supports a variety of antagonistic solid state interactions alongside a distinct dual guest pore system. In this 2-D Hofmann-type material we find that inbuilt competition between ferro- and antiferro-elastic interactions provides a SCO behavior that is intrinsically frustrated. This frustration is harnessed by guest exchange to yield a very broad array of spin transition characters in the one framework lattice (one- (1·(HO,EtOH)), two- (1·3HO) and three-stepped (1·∼2HO) transitions and SCO-deactivation (1)). This variety of behaviors illustrates that the degree of elastic frustration can be manipulated by molecular guests, which suggests that the structural features that contribute to multistep switching may be more subtle than previously anticipated.
自旋交叉（SCO）现象定义了一类优雅的可切换材料，当存在长程弹性相互作用时，它们可以表现出协同转变。当拮抗相互作用（即竞争的铁弹和反铁弹弹性相互作用）驱动协同晶格变形时，这种材料可以表现出多步转变，不仅从根本上而且从扩展的数据存储应用的角度来看都是如此。为此，我们制备了一种新的 SCO 框架支架 [Fe(bztrz)(Pd(CN))]·n(guest)（bztrz = (E)-1-苯基-N-(1,2,4-三唑-4-基)亚甲胺，1·n(guest)），它支持多种拮抗固态相互作用以及独特的双客体孔系统。在这种二维霍夫曼型材料中，我们发现铁弹和反铁弹弹性相互作用之间的固有竞争提供了一种本质上受挫的 SCO 行为。这种挫折通过客体交换得到利用，从而在一个框架晶格中产生非常广泛的自旋转变特性（单步 (1·(HO,EtOH))、两步 (1·3HO) 和三步 (1·∼2HO) 转变和 SCO 失活 (1))。这种多种行为表明，弹性挫折的程度可以通过分子客体来控制，这表明导致多步切换的结构特征可能比预期的更为微妙。
