Spin Crossover in [Fe(qsal-5-Br)] Complexes with a Quinoline-Substituted Qsal Ligand.

Using a quinoline substituted Qsal ligand, Hqsal-5-Br (Hqsal-5-Br = N-(5-bromo-8-quinolyl)salicylaldimine), four Fe complexes, [Fe(qsal-5-Br)]A·CHOH (Y = NO (), BF (), PF (), OTf (), were prepared and characterized. Structure analysis revealed that complex contained two species ((̅) and ()). In these compounds except , the [Fe(qsal-5-Br)] cations form 1D chains through π-π interactions and other weak interactions. Adjacent chains are connected to form the 2D "Chain Layer" structures and 3D structures through various supramolecular interactions. For , a "Dimer Chain" structure is formed from the loosely connected dimers. Magnetic studies revealed that compounds and (̅) displayed abrupt hysteretic SCO with the transition temperature ↓ = 235 K, ↑ = 240 K for and ↓ = 230 K, ↑ = 235 K for (), while compounds and are in the HS state. Desolvation of the complexes significantly modifies their SCO properties: the desolvated and show a gradual SCO, desolvated undergoes a two-step SCO, and desolvated exhibits a hysteretic transition. Overall, this work reported the Fe-SCO complexes of the quinoline-substituted Hqsal ligand and highlighted the potential of these ligands for the development of interesting Fe-SCO materials.