Alternating Ferro/Antiferromagnetic Copper(II) Chain Containing an Unprecedented Triple Formato/Hydroxido/Sulfato Bridge

The first example of a triple formato/hydroxido/sulfato (FHS) bridge for any metal is reported in compound [Cu2(bpym)­(OH)­(HCO2)­(SO4)­(H2O)2]·3H2O (1). Its structure shows the presence of alternating triple FHS bridges and 2,2′-bipyrimidine (bpym) ones. Although in the initial synthesis the sulfate anions were introduced accidentally, here we report the rational synthesis and the magnetic properties of this compound. The magnetic properties show that 1 is an alternating ferro/antiferromagnetic (F/AF) chain compound with predominant antiferromagnetic interactions and were fit to an alternating F/AF S = 1/2 chain with g = 2.103, JAF = −139 cm–1, and JF = 116 cm–1 (α = JF/|JAF| = 0.83). The JAF value found corresponds very well to those previously reported for Cu–bpym–Cu bridges (average value of ca. −150 cm–1). The JF value is also very close to the estimated one (ca. 100 cm–1) from magneto-structural correlations in triply Cu–Cu bridged compounds with both hydroxido and carboxylato bridges in equatorial positions.