Magnetic behaviour of the molecular sponge CoCu(pba)(H₂O)₃.2H₂O, where pba = 1,3-propylene bis(oxamato)

Abstract

We report the synthesis of the magnetic molecular compound CoCu(pba)(H₂O)³.2H₂O, where pba = 1,3-propylenebis(oxamato), which is blue in colour. Its X _M T against T behaviour suggests antiferromagnetic correlations between the Co(II)Cu(II)-based ferrimagnetic chains below about 7K. Heating this compound at 130°C in vacuum yields the dehydrated purple compound CoCu(pba).1H₂O, which exhibits a transition to the bulk ferromagnetic state at about 33 K, as confirmed by the dc and ac susceptibility measurements. The dehydrated compound is a relatively hard molecular magnet showing a coercive field of 0.3 T at 5 K. The most interesting aspect is its ‘sponge’-like characteristics, that is a complete reversibility of the magnetic properties, as well as the colour change, under a simple dehydration-rehydration process.