Coexistence of spin-crossover and antiferromagnetic coupling phenomena in the novel dinuclear Fe(II) complex [Fe(dpa)(NCS)2]2bpym

The iron(II) spin crossover dinuclear compound [Fe(dpa)(NCS)2]2bpym where dpa = 2,2′-dipyridylamine and bpym = 2,2′-bipyrimidine has been synthesized and characterized. Variable-temperature magnetic susceptibility and 57Fe Mössbauer spectroscopy data provide evidence for a rather complete and continuous S=2 (HS)↔S=0 (LS) spin-crossover behavior taking place in the temperature range 400–50 K (T1/2=245 K) without the presence of a plateau at 50% of conversion. The absence of such plateau, which is characteristic of all dinuclear compounds so far studied, is interpreted in terms of synergetic effect between intramolecular and intermolecular interactions.