Four isostructural lanthanide coordination polymers based on rare coordinated citric acid: Syntheses, structures, magnetisms and luminescence

• Four lanthanide coordination polymers have been synthesized by hydrothermal methods.
• All of them adopt rare coordinated modes based on citric acid.
• 1 displayed color-pure red luminescent behavior.
• 1 and 3 exhibited antiferromagnetic behaviors and 2 exhibited ferromagnetic behavior.

Four new isostructural lanthanide coordination polymers [Ln(Hcit)(H2O)2·2H2O]n (H4cit = citric acid) (Ln = Sm (1), Gd (2), Er (3), Nd (4)) have been synthesized under hydrothermal method by using citric acid, melamine as well as Sm(NO3)3·6H2O (1), Gd(NO3)3·6H2O (2), Er(NO3)3·6H2O (3), Nd(NO3)3·6H2O (4), and structurally characterized by FT-IR, thermogravimetric analyses (TGA), powder X-ray diffraction (PXRD), elemental analyses and X-ray single-crystal diffraction. The X-ray single-crystal diffraction analyses demonstrated that Hcit3- ligand adopt the rare coordination mode to connect the metal atoms of complexes 1–4 by chelating carboxyl group, single coordinated carboxyl group and hydroxyl group, forming left-handed and right-handed helical chains, which are further connected to 2D layer structures by Ln–O bonds. Furthermore, complex 1 displayed good fluorescence at solid state; complexes 1 and 3 exhibited antiferromagnetic behaviors, while complex 2 displayed ferromagnetic behavior.

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