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 [Ln 2 (adipate) 3 (H 2 O) 4 ]·6H 2 O (Ln 3+ = Pr 3+ ) and [Ln 2 (adipate) 3 (H 2 O) 4 ] x H 2 O (Ln 3+ = Gd 3+, Sm 3+ ), into the ionic 1D polymer [Ln(adipate)(H 2 O) 5 ]XH 2 O (with X = NO 3 −, Cl − and Ln 3+ = Pr 3+, Gd 3+, Sm 3+ ). The 1D polymer consists of positively charged hydrogen-bonded lanthanide−adipate chains enclathrating NO 3 − or Cl − anions acting as templates. The hydrogen bonds linking the chains between them are so strong that it is possible to exchange NO 3 − 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.