2D magnetic materials offer unprecedented opportunities for fundamental and applied research in spintronics and magnonics. Beyond the pioneering studies on 2D CrI₃ and Cr₂Ge₂Te₆, the field has expanded to 2D antiferromagnets exhibiting different spin anisotropies and textures. Of particular interest is the layered metamagnet CrSBr, a relatively air‐stable semiconductor formed by antiferromagnetically‐coupled ferromagnetic layers (T_c∼150 K) that can be exfoliated down to the single‐layer. It presents a complex magnetic behavior with a dynamic magnetic crossover, exhibiting a low‐temperature hidden‐order below T*∼40 K. Here, the magneto‐transport properties of CrSBr vertical heterostructures in the 2D limit are inspected. The results demonstrate the marked low‐dimensional character of the ferromagnetic monolayer, with short‐range correlations above T_c and an Ising‐type in‐plane anisotropy, being the spins spontaneously aligned along the easy axis b below T_c. By applying moderate magnetic fields along a and c axes, a spin‐reorientation occurs, leading to a magnetoresistance enhancement below T*. In multilayers, a spin‐valve behavior is observed, with negative magnetoresistance strongly enhanced along the three directions below T*. These results show that CrSBr monolayer/bilayer provides an ideal platform for studying and controlling field‐induced phenomena in two‐dimensions, offering new insights regarding 2D magnets and their integration into vertical spintronic devices.

Studies have revealed how pressure influences the path of one photochemical reaction in crystals. The single-crystal-to-single-crystal Norrish–Yang reaction of 4-(2,4,6-triisopropylbenzoyl)benzoate benzylammonium, compound 1, was studied at high pressures of 0.3 and 0.9 GPa. X-ray structure analysis was used in order to monitor the kinetics of the reaction and the structural changes induced by UV radiation and pressure. The reaction rate is lower at higher pressure: the rate constants are 5.3 × 10⁻⁵ s⁻¹ and 4.3 × 10⁻⁶ s⁻¹ at 0.3 and 0.9 GPa, respectively. This was rationalized by: (a) the decrease in the size of voids near the reaction centre and in the unit cell with pressure, (b) the increase of intermolecular interactions in which the photoreactive o-isopropyl group takes part along with pressure and (c) the structural changes brought about by the photochemical reaction itself, for example, the increase of the unit cell volume. Pressure significantly reduced these structural changes and even halted some of them.

Crystals undergoing tandem reactions where the first transformation enables the second one are rare. Using photoreactive Dewar benzene 3,4,5,6-tetramethyl-1,2-dicarboxylic diacid (DB) as a hydrogen-bonding template for the [2π+2π] photodimerization of trans-4,4'-bipyridyl-ethenes (BPE), we obtained crystals DB-BPE-NT with a DB:BPE = 2:1 stoichiometry with double bonds at a nonreactive distance of 5.957 Å. Exposure to UV light resulted in valence bond isomerization to Hückel benzene 3,4,5,6-tetramethyl-1,2-dicarboxylic acid (HB) by a quantum chain reaction that triggered the sought-after topochemical [2π+2π] photodimerization reaction. Notably, crystals HB:BPE-T with the Hückel benzene isomer and BPE adopted a 2:2 stoichiometry and displayed an efficient topochemically templated photodimerization reaction.

The [2 + 2] photodimerization of 2,6-difluorocinnamic acid was gradually induced in crystals by UV radiation at 0.5, 1.1 and 2.1 GPa. The crystal and molecular structures were determined before the photochemical reaction and for many of its steps. For the pure monomer structures, the following parameters were analyzed in order to gain knowledge of the influence of pressure on the reaction environment: (a) the volume of free space, (b) the geometry of close intermolecular interactions, including hydrogen bonds and (c) the geometry of intermolecular reactivity parameters. The following structural changes brought about by the [2 + 2] photodimerization at high pressure were monitored step-by-step: (a) the cell parameters and the cell volume, (b) the content of the monomer and the dimer, (c) the distance between the reactive carbon atoms in adjacent monomer molecules and (d) the geometry of mutual orientation of molecules in the crystals. The rate of the [2 + 2] photodimerization of 2,6-difluorocinnamic acid increased as follows: 0.1 MPa < 0.5 GPa < 1.1 GPa ≤ 2.1 GPa. This was rationalized by the decrease in the volume of free space columns protecting the intermolecular geometry suitable for the reaction and by the decrease of the distance between the reactive carbon atoms of adjacent monomer molecules.