CROSSOVER BETWEEN 3-DIMENSIONAL ANTIFERROMAGNETIC AND FERROMAGNETIC STATES IN CO(II)CU(II) FERRIMAGNETIC CHAIN COMPOUNDS - A NEW MOLECULAR-BASED MAGNET WITH T-C=38 K AND A COERCIVE FIELD OF 5.66X10(3) OE

CoCu(pbaOH)(H2O)(3) . 2H(2)O (1) is a Co(II)Cu(II) chain compound in w hich the ferrimagnetic chains interact antiferromagnetically within th e lattice. Removing the two noncoordinated water molecules through a t hermal treatment results in the new chain compound CoCu(pbaOH)(H2O)(3) (2) which exhibits a ferromagnetic ordering of the ferrimagnetic chai ns at T-c = 9.5 K. Removing a third water molecule, occupying the apic al position in the copper coordination sphere, results in CoCu(pbaOH)( H2O)(2) (3) which again exhibits a three-dimensional ferromagnetic ord ering, but at T-c = 38 K. The field dependence of the magnetization fo r 3 reveals a coercive field of 5.66 x 10(3) Oe at 2 K, probably a rec ord in the field of molecular-based magnets. This dehydration process giving rise to a crossover between long-range antiferro- and ferromagn etic states is reversible, and can be repeated.