Two novel coordination polymers in the family of lanthanide complexes with o-phenylenedioxydiacetato as ligand

Abstract

Two novel coordination polymers [Ce(PDOA)(NO3)(H2O)2]n (1) and {[Ce(PDOA)(NO3)(H2O)3]·H2O}n (2) (PDOA=o-phenylenedioxydiacetato) have been prepared using hydrothermal conditions and have been structurally characterized. In both crystal structures 1 and 2 the Ce(III) atoms are decacoordinated by oxygen atoms from PDOA ligands with chelating and bridging functions, chelating nitrato ligands and aqua ligands. While in 1 the PDOA ligand presents a hexadentate coordination mode, in 2 it is coordinated in a pentadentate manner; this difference leads to different types of one-dimensional structural motifs: in 2 there are zig–zag chains of the –Ce–O–C–O–Ce– type with syn–anti carboxylate bridges and in 1 these chains are additionally interlinked by further syn–anti carboxylate bridges leading to a strip- or ribbon-like arrangement formed of {Ce3} fused triangles. The endothermic dehydration of 1 within the temperature range 69–199°C is at least a two-step process as suggested by TG and DTA methods. A variable temperature (2–300K) magnetic study reveals Curie–Weiss behavior for 1 with θ=−35.5K observed above 50K. The origin of the observed behavior is discussed.