An azido-bridged [Fe4II] grid-like molecule showing spin crossover behaviour

The supramolecular self-assembly synthetic strategy provides a valid tool to obtain polynuclear Fe(II) complexes having effective communication between the metal centres and distinct spin crossover behaviour. Despite the great success in constructing various magnetic molecules, progress has not been made in SCO complexes based on azido bridges. In this article, the coordination-driven supramolecular assembly based on 3,6-substituted pyridazine and azide is presented to afford two Fe(ii) grid-like complexes: [(L)(4)Fe-4(II)(N-3)(4)][BPh4](4).sol (1, L = 3,6-bis(3,5-dimethyl-1H-pyrazol-1-yl)pyridazine and 2, L = 3,6-di(pyridin-2-yl)pyridazine). The substitution of pyridinyl groups in 2 instead of pyrazolyl ones in 1 led to the only example exhibiting spin-crossover behaviour (T-1/2 = 230 K) among the azido-bridged complexes. In addition, a temperature-dependent photoluminescence study of 2 demonstrates a visible synergetic effect between the SCO event and the luminescence.

Automated summary

The study successfully obtained two Fe(ii) grid-like complexes using a coordination-driven supramolecular assembly strategy, demonstrating spin-crossover behavior in azido-bridged complexes. By substitution of the ligand, the complex showed a synergistic effect between spin-crossover behavior and luminescence.