Thiocyanato Coordination Polymers with Isomeric Coordination Networks – Synthesis, Structures, and Magnetic Properties

Abstract

Abstract The reactions of M(NCS) 2 (M = Mn, Fe, and Ni) with 4‐acetylpyridine (4‐Acpy) in water lead to the formation of discrete complexes of composition M(NCS) 2 (4‐Acpy) 2 (H 2 O) 2 , in which the metal cations are coordinated only N‐terminally to the thiocyanato anions. When heated, these precursors dehydrate, and some of them transform into compounds of composition [M(NCS) 2 (4‐Acpy) 2 ] n , in which the metal cations are linked by pairs of μ‐1,3‐bridging anionic ligands into chains (1D isomer). In contrast, the thermal decomposition of Ni(NCS) 2 (4‐Acpy) 4 or crystallization from solution leads to the formation of an isomeric 2D network of the same composition, which is thermodynamically more stable than the 1D isomer. Temperature‐dependent magnetic measurements of the 1D isomer [Fe(NCS) 2 (4‐Acpy) 2 ] n at 200 Oe reveal antiferromagnetic ordering at T N = 4.5 K. Field‐dependent measurements show a metamagnetic transition into a saturated paramagnetic phase at a critical field of ca. 700 Oe. In contrast, magnetic measurements of the 2D isomer [Ni(NCS) 2 (4‐Acpy) 2 ] n at 1000 Oe show a ferromagnetic transition at T C = 8.6 K, whereas only paramagnetic behavior is observed for the Ni 1D isomer.