Preparations, Structures, and Magnetic Properties of a Series of Novel Copper(II)−Lanthanide(III) Coordination Polymers via Hydrothermal Reaction

The hydrothermal reaction of Ln2O3 (Ln = Er, Gd, and Sm), pyridine-2,5-dicarboxylic acid (H2pydc), and Cu(II)
reagents (CuO, Cu(OAc)2·2H2O, or CuCl2·2H2O) with a mole ratio of 1:2:4 resulted in the formation of six polymeric
Cu(II)−Ln(III) complexes, [{Ln2Cu3(pydc)6(H2O)12}·4H2O]n (Ln = Er (1); Ln = Gd (2)), [{Ln4Cu2(pydc)8(H2O)12}·4H2O]n (Ln = Sm (3); Ln = Gd (4); Ln = Er (5)), and [{Gd2Cu2(pydc)4(H2O)8}·Cu(pydc)2·12H2O]n (6). 1 and
2 are isomorphous and crystallize in triclinic space group P1̄. Compounds 3−5 are isomorphous and crystallize
in monoclinic space group P21/c. Compound 6 crystallizes in triclinic space group P1̄. Complexes 1 and 2 have
one-dimensional zigzag chain structures and compounds 3−5 display three-dimensional wavelike polymeric
structures, while 6 has an infinite sandwich-type structure. The different structures of the complexes are induced
by the different forms of Cu(II) reagents; the reactions of Cu(OAc)2·2H2O yield high Cu/Ln ratio products 1, 2,
and 6, while the reactions of CuO or CuCl2·2H2O/2,2‘-bipyridine results in low Cu/Ln ratio compounds 3−5.
Temperature-dependent magnetic susceptibilities for 2, 4, and 5 were studied, and the thermal stabilities of
complexes 2 and 4 were examined.