Dual-supramolecular contacts induce extreme Hofmann framework distortion and multi-stepped spin-crossover
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Date
2021-01-13
Journal Title
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Publisher
Royal Society of Chemistry
Abstract
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[thin space (1/6-em)]:[thin space (1/6-em)]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[thin space (1/6-em)]:[thin space (1/6-em)]1) and spin-state (1[thin space (1/6-em)]:[thin space (1/6-em)]1) periodicity at the HS[thin space (1/6-em)]:[thin space (1/6-em)]LS step provides key insight into the competition (frustration) between elastic interactions and crystallographically driven order. © The Royal Society of Chemistry 2021
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Keywords
Crystal lattices, Monocrystals, Ligands, X-ray diffraction, Hydrogen, Interactions
Citation
Ahmed, M., Brand, H. E. A., Peterson, V. K., Clegg, J. K., Kepert, C. J., Price, J. R., Powell, B., J. & Neville, S. M. (2021). Dual-supramolecular contacts induce extreme Hofmann framework distortion and multi-stepped spin-crossover. Dalton Transactions, 50(4), 1434-1442. doi:10.1039/D0DT04007J