Gadolinium Break in a Series of Three-Dimensional trans-1,4-Cyclohexane Dicarboxylates of Rare Earth Elements

Abstract

By a reaction of lanthanide nitrates with trans-1,4-cyclohexane dicarboxylic acid H₂chdc in an aqueous medium new coordination polymers with the composition [Ln₂(H₂O)₄(chdc)₃] (Ln = Ce (1), Sm (2), Eu (3), Gd (4)) are obtained. Crystallization conditions are optimized with the use of a hexamine-based pH buffer. Compound 1 is additionally characterized by powder X-ray diffraction, elemental and thermogravimetric analyses, and IR spectroscopy. The structure of the obtained compounds is determined by single crystal X-ray diffraction. In a series of isostructural three-dimensional frameworks [Ln₂(H₂O)₄(chdc)₃] (Ln = La—Eu, except Pm) a regular change in the structural features is analyzed. The [Gd₂(H₂O)₄(chdc)₃] compound has a similar composition but the topology of the three-dimensional network differs from that of the previous ones due to a decrease in the coordination number of metal centers. Heavier lanthanides, starting from Tb³⁺, and also yttrium(III) do not form compounds with the mentioned composition under similar reaction conditions.