Pressure-Selective Magnetic Switching via Spatially Separated Soft Interlayer and Rigid Charge-Transfer Intralayer

Abstract

We report a pressure-responsive molecule-based magnet featuring a layered cyanido-bridged Co–W assembly, [{CoII(4-phenoxypyridine)4}3{WV(CN)8}2], exhibiting a distinct pressure-selective magnetic behavior. The compound forms two-dimensional charge-transfer layers with large interlayer separation induced by bulky ligands, enabling a dimensional crossover of magnetization from two-dimensional to three-dimensional behavior at low temperatures. Applying moderate pressure up to 0.27 GPa selectively compresses the layers, eliminating the dimensional crossover and enhancing ferromagnetic interactions, increasing both the Curie temperature and coercive field. Upon further compression, the interlayer distance reaches a limit, triggering a pressure-induced charge-transfer phase transition from the high-spin CoII–WV to the low-spin CoIII–WIV state, which weakens ferromagnetism and eventually leads to complete paramagnetic behavior at higher pressures. The difference in the compressibility between the soft interlayer regions and the rigid charge-transfer intralayer enables two-step magnetic control solely by pressure, a rare feature in molecule-based magnets. High-pressure X-ray diffraction and microscopic imaging confirm the structural sensitivity of the interlayer regions and correlate the pressure-induced phase transitions with the sequential pressure-induced color changes. These findings demonstrate that the interlayer distance and its rigid layer are key parameters for designing pressure-responsive magnetic materials, offering a new strategy for controllable molecular magnetism via external stimuli.