A novel supramolecular synthon for H-bonded coordination networks: syntheses and structures of extended 2-dimensional cadmium(II) arenedisulfonates

Abstract

Four cadmium(II) arenedisulfonate polymers, namely [Cd(N,N′-meen)₂](2,6nds) (1), [Cd(N,N′-meen)₂](1,5nds) (2), [Cd(N,N′-meen)₂](bpds) (3), and [Cd(N-meen)₂](2,6nds)·2H₂O (4), where nds = naphthalenedisulfonate, bpds = 4,4′-biphenyldisulfonate, N,N′-meen = N,N′-dimethylethylenediamine and N-meen = N-methylethylenediamine, have been synthesized in aqueous solution and structurally characterized by X-ray single crystal diffraction and IR spectroscopy. In all four crystalline materials, the arenedisulfonate anions act as bifunctional spacers to coordinate the CdN₄ complex cations, generating stepwise 1-dimensional strings. Due to the inherent multiple H-bonding donors/acceptors on their neutral polymeric backbones the same pattern of inter-chain H-bonding interactions described as C(6)R₂²(12) are formed by the amino H-atoms and sulfonate O-atoms. Hence, the driving forces for the assembly of these 1-dimensional polymers into 2-dimensional networks have been rationalized and a unique supramolecular synthon identified. It represents a novel strategy that leads to predictable 2-dimensional coordination networks sustained by direct H-bonding interactions between the 1-dimensional polymeric backbones.