A New Family of 4f-3d Heterometallic Metal–Organic Frameworks with 2,2′-Bipyridine-3,3′-dicarboxylic Acid: Syntheses, Structures and Magnetic Properties

Eight isostructural lanthanide­(III)-cobalt­(II)
heterometallic metal–organic
frameworks (MOFs), {[Ln2Co­(BPDC)4(H2O)6]·xH2O}n (Ln = La (1-La, x =
9), Pr (2-Pr, x = 11), Nd (3-Nd, x = 8), Sm (4-Sm, x = 9), Eu (5-Eu, x = 6), Gd (6-Gd, x = 6.5), Tb (7-Tb, x = 7), Dy (8-Dy, x = 8);
H2BPDC = 2,2′-bipyridine-3,3′-dicarboxylic
acid), have been prepared and characterized. In these complexes, two
crystallographically independent Ln3+ ions are connected
via carboxyl groups into binuclear units, which are further linked
into a lanthanide chain through bridging BPDC2–.
Each Co2+ ion is chelated by the bipyridine groups of three
BPDC2– and further links the lanthanide chain to
form a three-dimensional framework. The framework with one-dimensional
channels occupied by water molecules possesses a new topology with
the short (Schläfli) vertex symbol {3·62}­{32·66·73·83·9}­{62·7}. The magnetic properties of the eight heterometallic
MOFs have been studied, in which only 8-Dy displays slow
relaxation of the magnetization at low temperature.