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

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.