Controlled Self-Assembly of a 2‑D Sheet Coordination Polymer and Monomer Containing an Eight-Membered Cu<sub>4</sub>I<sub>4</sub> Crown Motif

The reaction of Ni­(mnt)<sub>2</sub> (mnt = 1,2-dicyano-1,2-ethylenedithiolate) with CuI in THF results in the formation of a Ni­(mnt)<sub>2</sub>Cu<sub>4</sub>I<sub>4</sub> unit with an eight-membered Cu<sub>4</sub>I<sub>4</sub> crown motif. Coordination polymers with Ni­(mnt)<sub>2</sub>Cu<sub>4</sub>I<sub>4</sub> building units, having doubly bridged 1-D chains, were formed with bulky NBu<sub>4</sub> counterions. To pack the bulky NBu<sub>4</sub> cations into the crystal structure, no direct interactions between the 1-D chain structures are observed. When the bulky NBu<sub>4</sub> cations are exchanged for small sodium cations, direct interactions between the 1-D chain structures dominate. A doubly bridged 2-D sheet structure is formed through the bridging of the cyano groups of the Ni­(mnt)<sub>2</sub>Cu<sub>4</sub>I<sub>4</sub> units of neighboring 1-D chain structures by sodium atoms. The monomeric [Na<sub>2</sub>(18-crown-16)]<sub>2</sub>[Ni­(mnt)<sub>2</sub>Cu<sub>4</sub>I<sub>4</sub>] complex is formed when the sodium cations of the 2-D sheet structure are captured by 18-crown-6. The configuration of the coordination polymer or the monomer is controlled through the selection of the appropriate countercation to the Ni­(mnt)<sub>2</sub>Cu<sub>4</sub>I<sub>4</sub> building unit. Furthermore, the eight-membered Cu<sub>4</sub>I<sub>4</sub> crown motifs in the 2-D sheet structure captures sodium cations. In this regard, we propose that the flexible Cu<sub>4</sub>I<sub>4</sub> crown motif is capable of capturing atoms or molecules of various sizes; such a material may act as a useful molecular adsorbent through electrostatic interactions.