Synthesis and characterization of a new molecular magnet, [Ni(ampy)2]3[Fe(CN)6]2•6H2O, and synthesis, crystal structure and magnetic properties of its mononuclear precursor, trans-[Ni(ampy)2(NO3)2] (ampy=2-aminomethylpyridine)

The reaction of trans-[Ni(ampy)(2)(NO3)(2)] (1) (ampy = 2-aminomethylpyridine) with K-3[Fe(CN)(6)] affords a cyano-bridged bimetallic system, (Ni(ampy)(2)](3)[Fe(CN)(6)](2). 6H(2)O (2). The crystal structure of compound 1 has been solved. It crystallizes in the monoclinic space group P121/c1 and consists of neutral mononuclear entities with the nickel atom located on an inversion center. The nickel atom exhibits a (pseudo)octahedral stereochemistry with the two nitrate ligands coordinated in trans positions. The Ni-N bond distances vary from 2.0690(15) to 2.0811(15) Angstrom, while the trans-Ni-O distances are 2.1665(13) Angstrom. The cryomagnetic investigation of compound 1 reveals an intermolecular ferromagnetic coupling (theta = + 3.7 K), which is mediated by the pi-pi stacking interactions between the mononuclear entities. Compound 2 is a soft ferromagnet with T-c = 7.5 K and a coercive field of 330 G at 2 K. (C) 2000 Elsevier Science Ltd. All rights reserved.