3D lanthanide–transition-metal–organic frameworks constructed from tetranuclear {Ln4} SBUs and Cu centres with fsc net

Abstract

Four novel lanthanide(III)–copper(II) heterometallic coordination polymers based on six-coordinated Cu centres and square-planar tetranuclear {Ln₄} SBUs with sulfate as an auxiliary bridging ligand, namely, [Ln₂Cu_0.5(2,6-pydc)₂(2-pyc)(SO₄)(H₂O)₂]·(H₂O) (Ln = Nd 1, Sm 2, Eu 3, Gd 4; 2,6-pydc = pyridine-2,6-dicarboxylate, 2-pyc = pyridine-2-carboxylate), have been hydrothermally synthesized and structurally characterized by single-crystal X-ray diffraction. Compounds 1–4 are isostructural and present a rarely reported binodal (4,6)-connected fsc net with the Cu centre as a four-connected node and the tetranuclear {Ln₄} SBUs as six-connected nodes. As far as we know, a fsc net in hetero-Ln–TM coordination polymers has never been reported. This work provides a good example of incorporating {Ln₄} SBUs and Cu centres to construct a heterometallic binodal net. Notably, the 2-pyc ligand was in situ generated by decarboxylation of the 2,6-pydc ligand under hydrothermal conditions. Furthermore, the IR, TGA, PXRD, luminescent and magnetic properties were also investigated.