Lanthanide contraction in linear lanthanide–oxygen clusters
Five coordination polymers containing linear lanthanide–oxygen clusters 1–5 have been synthesized by a hydrothermal reaction of 3-(quinolin-8-yloxy) phthalic acid (H2L) with the respective lanthanide salt. The X-ray single crystal structural analyses revealed that these five crystalline materials belong to two isostructures with formulas [LnHL2(H2O)2]n (Ln1, where Ln = La 1, Ce 2, Pr 3) and [Ln(HL)(L)(H2O)]n (Ln2, where Ln = Nd 4, Sm 5), respectively, which are attributed to the effect of lanthanide contraction. In both structures, the lanthanide cations were bridged by two carboxyl groups of L2− through Ln–O bonds to form 1-D linear lanthanide–oxygen clusters, which were further connected by intermolecular π–π stacking interactions between quinolinyl units to generate 3-D supramolecular polymers with moderate luminescence and high thermal stability.
