Cyanido-Bridged FeII–MI Dimetallic Hofmann-Like Spin-Crossover Coordination Polymers Based on 2,6-Naphthyridine

Article abstract of DOI:10.1002/ejic.201700920

Two new 3D spin-crossover (SCO) Hofmann-type coordination polymers {Fe(2,6-naphthy)[Ag(CN)₂][Ag₂(CN)₃]} (1; 2,6-naphthy = 2,6-naphthyridine) and {Fe(2,6-naphthy)[Au(CN)₂]₂}·0.5PhNO₂ (2) were synthesized and characterized. Both derivatives are made up of infinite stacks of {Fe[Ag(CN)₂]₂[Ag₂(CN)₃]}_n and {Fe[Au(CN)₂]₂}_n layered grids connected by pillars of 2,6-naphthy ligands coordinated to the axial positions of the Fe^II centers of alternate layers. The in situ generated [Ag₂(CN)₃]^– linkers define wide rectangular windows that favor the interpenetration of three identical 3D networks, strong argentophilic interactions between them, and the generation of a densely packed structure without accessible void spaces. In contrast, the smaller rhombus-shaped window in 2 affords a structure made up of doubly interpenetrated 3D networks with strong aurophilic interactions between them and accessible voids partially occupied by nitrobenzene molecules. Compound 1 displays a relatively abrupt two-step SCO in the temperature interval 150–215 K, whereas 2 features an incomplete one-step SCO behavior (T_1/2 = 166 K) that extends over 150 K.