Spin crossover behavior in two-dimensional bimetallic coordination polymer Fe II(3-bromo-4-picoline) 2[Au I(CN) 2] 2: Synthesis, crystal structures, and magnetic properties

Abstract

A new novel 2D network bimetallic Fe IIAu I spin crossover coordination compound based on 3-bromo-4-picoline and bridged cyano ligands, {Fe II(3-bromo-4-picoline) 2[Au I(CN) 2] 2} n ( 1), has been synthesized and characterized by elemental analyses and IR, using single-crystal X-ray analysis at 293 K and at 90 K and magnetic measurements. The Fe II ions in 1 have octahedral FeN 6 coordination geometries, which are linked by a [Au I(CN) 2] − unit at the equatorial plane to form a polymeric 2D sheet architecture. The two pyridine rings coordinate at the axial positions. The structure of 1 comprises parallel 2D arrays and the layers interact by pairs, defining bilayers with strong binuclear aurophilic Au⋯Au interactions. Furthermore, intermolecular Au⋯Br and Br⋯Br distances in 1 are significantly smaller than the sums of the van der Waals radii. Variable-temperature (2–300 K) magnetic susceptibility measurements of 1 have been performed to determine behaviors of spin transition. The susceptibility data of 1 indicates that about 50% of the HS states are changed to LS states at 75 K. The Fe–N bond distances at 90 K show that ratio of high spin states agree with the SQUID data.