N,N′-Dimethylene-2,2′-biimidazoleA Mimic of Carboxylate for the Formation of Complexes with Copper(I) And the Anion Directed Formation of a Solvent Pocket

The reaction of N,N′-dimethylene-2,2′-biimidazole
(L) with various copper salts gives eight complexes that
were characterized structurally in the solid state. This showed that
the ligand can effectively bridge two copper atoms in close proximity
similarly to the well-known bridging carboxylate motif. In reaction
with copper­(II), this gives a dimer (acetate, 1) or quadruple
helicate (perchlorate, 2). Extention to copper­(I) with
a coordinating counterion gives a one-dimensional polymer (iodide, 3), while reaction with noncoordinating counterion gives M2L3 triple helicate motifs. These helicates were
found to form chiral solvate-containing pockets surrounding benzene
when combined with a three-fold symmetric anion (BF4–, ClO4– and NO3–, 4, 5, and 6, respectively) or an achiral complex with only acetonitrile (ClO4–, 7). While the pocket could
accommodate fluorobenzene (BF4–, 8), more highly substituted benzenes do not allow its formation.