Crystal structure and magnetic property of spin crossover complex FeII(3-phenylpyridine)2[AuI(CN)2]2

A novel two-dimensional network bimetallic Fe Au spin crossover coordination polymer based on 3-phenylpyridine-coordinated iron centers and linear gold cyanide bridges {Fe(3-phenylpyridine)2[Au(CN)2]2}n (1), has been synthesized. The compound is characterized by elemental analysis, IR, single-crystal X-ray analysis at 300 and 90 K and magnetic measurements. The FeII ions in 1 have octahedral FeIIN6 coordination geometries, which are linked by [Au(CN)2]− units at the equatorial plane to form a polymeric 2D sheet architecture. The two pyridine rings coordinate in axial position. Variable-temperature (2–300 K) magnetic susceptibility measurements of 1 were performed to determine the spin transition behavior. SQUID data show that high and low spin states exist in a 1:1 ratio at 90 K. However, only one kind of FeII atom is apparent crystallographically at 90 K, indicating that the high and low spin sites are disordered in the polymeric 2D framework.

Graphical abstractCoordination structure of the Fe and Au ions in 1 (300 K) containing its asymmetric unit and atom numbering. The structure of 1 at 90 K is almost identical to that of 1 at 300 K. Consequently, we have used the same representation for these compounds. In this picture, hydrogen atoms are omitted for clarity. Atom code: Fe(purple), Au(yellow), and N(blue), C(black).Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► A new spin crossover compound {Fe(3-phenylpyridine)2[Au(CN)2]2}n{Fe(3-phenylpyridine)2[Au(CN)2]2}n has been synthesized. ► The Fe(II) ions are linked by a [Au(CN)2]− unit at the equatorial plane to form a polymeric 2D sheet. ► SQUID data show that 50:50% high and low spin states exist at 90 K.