Syntheses, structures and magnetic properties of two Co/Ni isostructural coordination polymers based on an asymmetric semirigid tricarboxylate ligand.

Two new isostructural complexes, namely, poly[aqua[μ-2-(4-carboxyphenoxy)terephthalato-κO:O:O](1,10-phenanthroline-κN,N')cobalt(II)], [Co(CHO)(CHN)(HO)] or [Co(μ-Hcpota)(phen)(HO)], I, and poly[aqua[μ-2-(4-carboxyphenoxy)terephthalato-κO:O:O](1,10-phenanthroline-κN,N')nickel(II)], [Ni(CHO)(CHN)(HO)] or [Ni(μ-Hcpota)(phen)(HO)], II, have been synthesized by solvothermal reactions. Complexes I and II were fully characterized by IR spectroscopy, elemental analyses, thermogravimetric analyses, and powder and single-crystal X-ray diffraction. They both present two-dimensional structures based on [M(μ-COO)] (M = Co or Ni) dinuclear metal units with a fes topology and a vertex symbol (4·8). Interestingly, the positions of the two dimeric metal motifs and the two partially deprotonated Hcpota ligands reproduce regular flying butterfly arrangements flipped upside down and sharing wings in the ab plane. Magnetic studies indicate antiferromagnetic interactions (J = -5.21 cm for I and -11.53 cm for II) in the dimeric units, with Co...Co and Ni...Ni distances of 4.397 (1) and 4.358 (1) Å, respectively, that are related to double syn-anti carboxylate bridges.