Ahmed Manan, Brand Helen E A, Peterson Vanessa K, Clegg Jack K, Kepert Cameron J, Price Jason R, Powell Benjamin J, Neville Suzanne M
School of Chemistry, The University of New South Wales, Sydney, 2052, Australia.
The Australian Synchrotron, 800 Blackburn Road, Clayton, Victoria, Australia.
Dalton Trans. 2021 Feb 2;50(4):1434-1442. doi: 10.1039/d0dt04007j.
An extended nitro-functionalised 1,2,4-triazole ligand has been used to induce considerable lattice distortion in a 2-D Hofmann framework material via competing supramolecular interactions. Single crystal X-ray diffraction analyses on [Fe3(N-cintrz)6(Pd(CN)4)3]·6H2O (N-cintrz: (E)-3-(2-nitrophenyl)acrylaldehyde) reveal a substantial deviation from a regular Hofmann structure, in particular as the intra- and inter-layer contacts are dominated by hydrogen-bonding interactions rather than the typical π-stacking arrays. Also, the 2-D Hofmann layers show an assortment of ligand conformations and local FeII coordination environments driven by the optimisation of competing supramolecular contacts. Temperature-dependent magnetic susceptibility measurements reveal a two-step spin crossover (SCO) transition. Variable temperature structural analyses show that the two crystallographically distinct FeII centres, which are arranged in stripes (2 : 1 ratio) within each Hofmann layer, undergo a cooperative HS ↔ HS/LS ↔ LS (HS = high spin, LS = low spin) transition without periodic spin-state ordering. The mismatch between crystallographic (2 : 1) and spin-state (1 : 1) periodicity at the HS : LS step provides key insight into the competition (frustration) between elastic interactions and crystallographically driven order.
一种扩展的硝基官能化1,2,4-三唑配体已被用于通过竞争性超分子相互作用在二维霍夫曼骨架材料中诱导相当大的晶格畸变。对[Fe3(N-cintrz)6(Pd(CN)4)3]·6H2O（N-cintrz：(E)-3-(2-硝基苯基)丙烯醛）进行的单晶X射线衍射分析表明，其与规则的霍夫曼结构存在显著偏差，特别是层内和层间接触以氢键相互作用为主，而非典型的π-堆积阵列。此外，二维霍夫曼层显示出由竞争性超分子接触的优化所驱动的各种配体构象和局部FeII配位环境。变温磁化率测量揭示了两步自旋交叉（SCO）转变。变温结构分析表明，在每个霍夫曼层内以条纹形式排列（比例为2∶1）的两个晶体学上不同的FeII中心经历了协同的HS ↔ HS/LS ↔ LS（HS = 高自旋，LS = 低自旋）转变，且没有周期性的自旋态有序。在HS∶LS步骤中晶体学（2∶1）和自旋态（1∶1）周期性之间的不匹配为弹性相互作用和晶体学驱动的有序之间的竞争（受挫）提供了关键见解。
