Solvent-Induced Carboxylate Shift and Movement of an Anthryl Side-Group in Single-Crystal to Single-Crystal Structural Dynamics in a Gadolinium Coordination Polymer

Abstract

Single crystal to single crystal (SC–SC) transformation involving cooperative movement of atoms represents one of the most fascinating phenomena in coordination polymers. Here, we describe a novel two-dimensional coordination polymer {[Gd2(L)3(DMF)2(H2O)2]·(DMF)2·(H2O)5.5}n (1) synthesized from carboxylate-based flexible ligand 5-[(anthracen-9-ylmethyl)-amino]-isophthalic acid and Gd(III) ion by the solvothermal technique. The complex undergoes solvent-induced rearrangement reactions with the cleavage and formation of coordination bonds and substantial movement of the anthracene side groups without losing crystallinity to form the daughter products as {[Gd2(L)3(H2O)4]·(DMF)4·(H2O)1.5}n (1a), {[Gd2(L)3(DMF)2(H2O)]·(DMF)2·(DCM)2·(H2O)5}n (1b), and [Gd(L)2(DEF)]n (1c). These transformations exhibit a crystallographic snapshot of “carboxylate-shift” process which is further supported by IR spectroscopy, elemental analysis, and powder X-ray diffraction patterns. To the best of our knowledge, it is the first example of carboxylate shift in a Gd(III) coordination polymer. The mother crystal 1 and the daughters 1a and 1c exhibit 4-connected sql topology, while 1b shows a 3-connected hcb topology. Magnetic susceptibility measurements at variable temperature indicate the existence of antiferromagnetic interactions in all the complexes. The photoluminescent properties of the complexes in the solid state are also investigated at room temperature.