Spin Crossover in a Series of Non-Hofmann-Type Fe(II) Coordination Polymers Based on [Hg(SeCN)] or [Hg(SeCN)] Building Blocks.

Self-assembly of [Hg(SeCN)] tetrahedral building blocks, iron(II) ions, and a series of bis-monodentate pyridyl-type bridging ligands has afforded the new heterobimetallic Hg-Fe coordination polymers {Fe[Hg(SeCN)](4,4'-bipy)} (), {Fe[Hg(SeCN)](tvp)} (), {Fe[Hg(SeCN)](4,4'-azpy)} (), {Fe[Hg(SeCN)](4,4'-azpy)(MeOH)} (), {Fe[Hg(SeCN)](3,3'-bipy)} () and {Fe[Hg(SeCN)](3,3'-azpy)} () (4,4-bipy = 4,4'-bipyridine, tvp = -1,2-bis(4-pyridyl)ethylene, 4,4'-azpy = 4,4'-azobispyridine, 3,3-bipy = 3,3'-bipyridine, 3,3'-azpy = 3,3'-azobispyridine). Single-crystal X-ray analyses show that compounds and display a two-dimensional robust sheet structure made up of infinite linear [(FeL)] (L = 4,4'-bipy or 4,4'-azpy) chains linked by formed {[Hg(L)(SeCN)]} anionic dimeric bridges. Complexes and - define three-dimensional networks with different topological structures, indicating, in combination with complexes and , that the polarity, length, rigidity, and conformation of the bridging organic ligand play important roles in the structural nature of the products reported here. The magnetic properties of complexes and show the occurrence of temperature- and light-induced spin crossover (SCO) properties, while complexes - are in the high-spin state at all temperatures. The current results provide a new route for the design and synthesis of new SCO functional materials with non-Hofmann-type traditional structures.