Synthesis and characterization of two 3-D polymeric lanthanide complexes constructed from 1,2,4,5-benzenetetracarboxylic acid

Two new 3-D lanthanide coordination polymers, [CeK(btec)(H₂O)₂] _n (1), [Ho(btec)_0.5(ad)_0.5(H₂O)] _n (2) (H₄btec?=?1,2,4,5-benzenetetracarboxylic acid, H₂ad?=?adipic acid), have been synthesized under hydrothermal conditions and characterized by elemental analysis, IR spectroscopy, and single-crystal X-ray diffraction. Structural analyses reveal that both complexes crystallized in monoclinic space group P2₁/c and possessed 3-D net-structures. In 1, btec adopts two types of coordination modes: µ₁₂–η²:η²:η²:η¹:η²:η²:η²:η¹ bridging mode linking six Ce(III) ions and six K⁺ ions and the other µ₈–η¹:η²:η²:η¹:η¹:η²:η²:η¹ bridging mode connecting four Ce(III) ions and four K⁺ ions. In 2, btec adopts a µ₆-bridging with each carboxylate group of btec ligand in a µ₂–η¹–η² mode, the adipate is µ₄-bridging with each carboxylate µ₂–η¹–η¹-monodentate. The topological analysis shows that 1 can be simplified to a 3-nodal net with the Schläfli symbol {3²,4⁸,5³,6²}₄{3⁴,4¹²,5¹²}{4³⁸,6²⁶,8²} and 2 can be simplified to a 3-nodal network with the Schläfli symbol {4²,8⁴}{4⁶,6⁶,8³}{4⁷,6³}₂. The thermogravimetric analyses and the X-ray powder diffraction of 1 and 2 are discussed.