Base-Directed Formation of Isostructural Lanthanide–Sulfate–Glutarate Coordination Polymers with Photoluminescence

A series of five
isostructural 3D lanthanide-based coordination
polymers [LnIII2(H2O)6(glu)(SO4)2]n [Ln
= Pr(1), Nd(2), Sm(3), Eu(4), and Gd(5)] was effortlessly obtained within
a few minutes via the microwave-heating method. The employment of
auxiliary bases, that is, sodium hydroxide, 4,4′-bipyridine,
and 1,4-diazabicyclo[2.2.2]octane, led to the formation of the title
complex, whereas base-free synthesis yielded a three-dimensional inorganic
coordination polymer, [Ln2(H2O)4(SO4)3]n·nH2O, Ln = Nd (2a). The robustness of the
synthetic method was illustrated as both microwave-heating and conventional
hydrothermal techniques also enabled the formation of a high-crystalline
phase-pure complex 1–5. In the structure
of 1–5, glutarato (glu2–) and sulfato ligands link dinuclear Ln(III) building units into
three-dimensional frames. The glu2– ligands act
as tethering linkers, expanding the structure into a neutral 3D coordination
network. Hydrogen bonds were found to be the predominant intermolecular
interactions in the crystal structures. Photoluminescence of the complex 1–5 was studied.