Synthesis and anomalous magnetic properties of heterometal dinuclear Fe(II)–Cr(III) complex bridged by 3,5-bis(pyridin-2-yl)-pyrazolate

A Cr(III)–Fe(II) dinuclear complex [(nta)Cr(μ-bpypz)Fe(dpea)]BF4, where bpypz=3,5-bis(pyridin-2-yl)-pyazolate, nta=nitrilotriacetate and dpea=(2-aminoethyl)-bis(2-pyridylmethyl)amine, has been synthesized and structurally characterized by ESI-MS and 2H NMR spectra. The proposed structure is mostly more planar in the bridging moiety as compared to that of the previously reported [(nta)Cr(μ-bpypz)Fe(picen)]BF4(N,N′-bis-(2-pyridylmethyl)ethylenediamine(picen)). The dpea complex is found to be a high spin state, but to exhibit no spin-crossover by magnetic susceptibility and Mössbauer spectra measurements; showing a large antiferromagnetic interaction, which could make the spin transition temperature lower and/or destroy spin-crossover, suggesting complementarity between spin-crossover and magnetic interaction.