Solvent-mediated supramolecular templated assembly of a metal organophosphonate viaa crystal-amorphous-crystal transformation

Three low-dimensional Cu(ii)-based organophosphonates were synthesized: two molecular cationic complexes, [Cu sub(2)( mu sub(2)-L) sub(2)( super(2,2')BPy) sub(2)(H sub(2)O) sub(2)](NO sub(3)) sub(2)S (1) and [Cu(L)( super(2,2')BPy) sub(2)].NO sub(3).(H sub(2)O) sub(2) (3), and one neutral complex, [Cu sub(2)( mu sub(2)-L) sub(2)( super(2,2')BPy) sub(2)(NO sub(3)) sub(2)].MeOH (2), assembled by the phosphonomonoester i.e., ethylhydrogen(anthracen-9-ylmethyl)phosphonate and an auxillary bidendate ligand (2,2'-bipyridine). Single-crystal X-ray diffraction analysis showed that complex 1 consisted of a dimer unit arranged supramolecularly with a nitrate anion and that these layers were further assembled via pi ... pi interactions, which resulted in the formation of a porous supramolecular architecture. The cationic complexes 1 and 3 showed supramolecular templated assembly by simply altering the solvent, which resulted in a change in architecture. The remarkable change from a cationic complex to a neutral complex viathe formation of an amorphous solid (1a) (a crystal-amorphous-crystal transformation) was observed when crystals of 1 were heated at 90 degree C under vacuum. It is hypothesized that the uncoordinated nitrate ion moved from the lattice to the metal, resulting in the transformation of the cationic metal complex into a neutral metal complex. These complexes also showed luminescent behaviour.