Chiral copper(I) iodide based porous coordination frameworks with asymmetrically substituted bridging N-donor ligands

The 2-dimensional coordination polymers 2∞[{(CuI)2(Mepyz)2} · Mepyz] (1a), 2∞[CuX(Mepyz)] (2a, X = Br; 2b, X = Cl) and 2∞[(CuX)2(Mepyz)] (3a, X = I;3b, X = Br) may be prepared by reaction of the appropriate copper(I) halide with 2-methylpyrazine (Mepyz) either in acetonitrile solution at 130 °C (2a/2b, 3a/3b) or without solvent at 20 °C (1a). Mepyz ligands bridge (CuI)2 rhomboid dimers in the chiral network of 1a, whose resulting 24-membered rings are large enough to accomodate an Mepyz guest molecule. 1a rapidly loses these guests to afford a crystalline powder (1b), that can reversibly imbibe benzonitrile molecules into its open channels. In contrast to 1a, the sheets of 2a/2b contain zigzag infinite CuX chains, those of 3a/3b staircase 1∞[CuX] double chains as their characteristic substructures. Helical 1∞[CuI] single chains in the 3-dimensional network of 3∞[CuI(Mepip)]4 are bridged by R-2-methylpiperazine (Mepip) ligands in a second example of a chiral coordination polymer.