Diverse coordination of two ligands in ferromagnetic [Cu(μ-HCO2)2(3-pyOH)]n and [Cu2(μ-HCO2)2(μ-3-pyOH)2(3-pyOH)2(HCO2)2]n

Two novel polynuclear complexes with methanoate anions and 3-hydroxypyridine ligands [Cu(l-HCO 2 ) 2 (3-pyOH)] n (1) and [Cu 2 -(l-HCO 2 ) 2 (l-3-pyOH) 2 (3-pyOH) 2 (HCO 2 ) 2 ] n (2), respectively, were synthesized and characterized. The central copper atom in 1 is sur-rounded by four methanoates and a 3-pyOH molecule, forming a square-pyramidal CuO 3 NO chromophore. All the methanoates arebidentate and serve as bridges between the adjacent copper ions via syn-anti and anti–anti coordination. The basal square coordinationaxes are formed by O(syn), N(3-pyOH) (1.974(2), 2.016(2) A˚) and O(anti), O(anti) (1.945(2), 1.960(2) A˚), while the third O(anti)(2.247(2) A˚) is on the top of the pyramid. A ferromagnetic transition with an exchange constant 2J/k B = 9.2 cm 1 is found for 1 below20 K. This interaction probably takes place through two syn-anti methanoates extended in a chain through the 2D structure. On theother hand, two monoatomic Cu–O–Cu intra-dinuclear asymmetric (1.986(2), 2.415(2) A˚) bridges of two methanoates in[Cu