Anion-Induced Formation of Lanthanide-Organic Chains From 3D Framework Solids. Anion Exchange in a Crystal-to-Crystal Manner

A water-mediated transformation reversibly converts the neutral 3D microporous coordination polymers [Ln2(adipate)3(H2O)4]·6H2O (Ln3+ = Pr3+) and [Ln2(adipate)3(H2O)4]xH2O (Ln3+ = Gd3+, Sm3+), into the ionic 1D polymer [Ln(adipate)(H2O)5]XH2O (with X = NO3−, Cl− and Ln3+ = Pr3+, Gd3+, Sm3+). The 1D polymer consists of positively charged hydrogen-bonded lanthanide−adipate chains enclathrating NO3− or Cl− anions acting as templates. The hydrogen bonds linking the chains between them are so strong that it is possible to exchange NO3− for Cl− and vice versa in a crystal-to-crystal manner. The anion exchange reactions were directly observed on crystals by using Raman microprobe spectroscopy, single-crystal X-ray diffraction, and scanning electron microscopy.