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Two new isostructural iron(II) complexes 1and 2, with the formula of Fe(1,4-dcb)(N(CN)2)2(1,4-dcb = 1,4-dichlorobenzene), have been prepared and characterized. 1was obtained under the ambient condition, whereas 2was prepared by the application of an external magnetic field with a strength of 0.5 T. Single-crystal X-ray structural analysis and Hirshfeld calculations have revealed that the external magnetic fields have induced the disorder of 1,4-dcb molecules in 2, which strengthened the Cl···N halogen-bonding contacts between 1,4-dcb arrays and one-dimensional (1D) Fe(N(CN)2)2chains. As a consequence, coplane stacking of 1,4-dcb arrays and 1D Fe(N(CN)2)2chains has been observed in 2. Compared with the stepped stacking and paramagnetic character for 1, the coplane stacking in 2has increased the lattice cooperativity and ligand-field strength of N(CN)2, which thus provided partial spin-state transition. While under 1.0 T, the complex was broken and resulted in the formation of crystals Fe(ClO4)·6(H2O), suggesting significantly the different influence of magnetic field strength on paramagnetic ions and antimagnetic organic molecules. These results have provided an effective strategy for molecular design with desired physical–chemical properties.

Organic–inorganic hybrid perovskites have attracted tremendous interest due to their unique properties and promising applications for solar cells and other optoelectronics. Two-dimensional organic–inorganic halide perovskite materials are of essential importance in luminescence fields. The existing methods of regulating optical properties mainly focus on changing the chemical composition and ion doping. Herein, by adopting top-down and dimensional-change strategies, a series of atomically thin organic–inorganic halide perovskites (X-PMA)2PbBr4(R = 2,3,4 substituted, PMA = benzylamine, X = Cl, Br) have been synthesized and characterized. The material characterizations show that they are structurally similar but slightly different. The optical measurements illustrate that the prepared compounds exhibit not only a broad band but also strong fluorescence emission within 400–800 nm. This feature can be explained by their unique structure, with both substitution of halogen and low dimension. This study enables their promising application for next-generation light-emitting materials and devices and provides an effective strategy for the design of novel optical materials.