Browsing by Author "Ahmed, M"
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- ItemDual-supramolecular contacts induce extreme Hofmann framework distortion and multi-stepped spin-crossover(Royal Society of Chemistry, 2021-01-13) Ahmed, M; Brand, HEA; Peterson, VK; Clegg, JK; Kepert, CJ; Price, JR; Powell, BJ; Neville, SMAn 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
- ItemHierarchical spin-crossover cooperativity in hybrid 1D chains of Fe(II)-1,2,4-triazole trimers linked by [Au(CN)2]− bridges(John Wiley & Sons, Inc, 2021-02-04) Ezzedinloo, L; Zenere, KA; Xie, Z; Ahmed, M; Scottwell, S; Bhadbhade, MM; Brand, HEA; Clegg, JK; Hua, C; Sciortino, NF; Parker, LC; Powell, BJ; Kepert, CJ; Neville, SMForemost, practical applications of spin-crossover (SCO) materials require control of the nature of the spin-state coupling. In existing SCO materials, there is a single, well-defined dimensionality relevant to the switching behavior. A new material, consisting of 1,2,4-triazole-based trimers coordinated into 1D chains by [Au(CN)2]− and spaced by anions and exchangeable guests, underwent SCO defined by elastic coupling across multiple dimensional hierarchies. Detailed structural, vibrational, and theoretical studies conclusively confirmed that intra-trimer coupling was an order of magnitude greater than the intramolecular coupling, which was an order of magnitude greater than intermolecular coupling. As such, a clear hierarchy on the nature of elastic coupling in SCO materials was ascertained for the first time, which is a necessary step for the technological development of molecular switching materials. © 2021 Wiley-VCH GmbH
- ItemLiquid-metal-assisted deposition and patterning of molybdenum dioxide at low temperature(American Chemical Society, 2021-11-10) Wang, Y; Mayyas, M; Yang, J; Ghasemian, MB; Tang, J; Mousavi, M; Han, J; Ahmed, M; Baharfar, M; Mao, G; Yao, Y; Esrafilzadeh, D; Cortie, DL; Kalantar-Zadeh, KMolybdenum dioxide (MoO2), considering its nearmetallic conductivity and surface plasmonic properties, is a great material for electronics, energy storage devices and biosensing. Yet to this day, room-temperature synthesis of large area MoO2, which allows deposition on arbitrary substrates, has remained a challenge. Due to their reactive interfaces and specific solubility conditions, gallium-based liquid metal alloys offer unique opportunities for synthesizing materials that can meet these challenges. Herein, a substrate-independent liquid metal-based method for the room temperature deposition and patterning of MoO2 is presented. By introducing a molybdate precursor to the surrounding of a eutectic gallium-indium alloy droplet, a uniform layer of hydrated molybdenum oxide (H2MoO3) is formed at the interface. This layer is then exfoliated and transferred onto a desired substrate. Utilizing the transferred H2MoO3 layer, a laser-writing technique is developed which selectively transforms this H2MoO3 into crystalline MoO2 and produces electrically conductive MoO2 patterns at room temperature. The electrical conductivity and plasmonic properties of the MoO2 are analyzed and demonstrated. The presented metal oxide room-temperature deposition and patterning method can find many applications in optoelectronics, sensing, and energy industries. © 2021 American Chemical Society