Ligand-driven self-assembly of iodine-based Cd(ii) complexes via dissolution–recrystallization structural transformation

Abstract

Iodo–cadmium(II) complexes with a diversity of crystalline architectures have been prepared via a combination of a Cd(II) precursor and varied iodine solutions. The iodo–Cd(II) complexes with 1,10-phenantroline were assembled via a dissolution–recrystallization structural transformation (DRST) process at room temperature. The mixtures of the Cd(II) precursor, namely [Cd(AS)₂(phen)₂]EtOH (1) (where AS = 4-aminosalicylate, phen = 1,10-phenantroline, EtOH = ethanol), with a methanolic or ethanolic solution of I₂ result in the construction of a new Cd(II) complex, namely [Cd(I)(I₃)(phen)₂] (2), whereas different known Cd(II) complexes, namely [Cd(I)₂(phen)₂] (3) and [Cd(I)₂(phen)]_n (4), were obtained from DRST of 1 in I₂-containing tetrahydrofuran, and acetonitrile or acetone, respectively. Remarkably, the versatile 4-aminosalicylate ligand has been proven as a key ancillary to initiate the DRST process of 1 at room temperature through a coordinated substitution by iodide/polyiodide anions, which stabilizes a new supramolecular coordination framework via weak intermolecular hydrogen bonds. Moreover, taking advantage of the flexible nature of the supramolecular framework, complex 2 exhibits a thermally-induced structural transformation, and the reversible DRST process of 3 to the original 1 has been realized.