Highly Polarizable Triiodide Anions (I₃^–) as Cross-Linkers for Coordination Polymers: Closing the Semiconductive Band Gap

From a hydrothermal reaction using CuI, KI, and 3,3′5,5′-tetramethyl-4,4′-bipyrazole (TMBP), the triiodide anion I3– has been integrated into the water-stable 2D coordination polymer Cu­(TMBP)­I3 (1). In contrast with other metal triiodide complexes, 1 features remarkably small distortions in the bond distances associated with the I3– units (i.e., the Cu–I and I–I bonds), which effectively link up the copper­(I) centers into infinite CuI3 chains. The electronic band gaps and electrical conductivity data are also found to be consistent with the I3– ion acting as an effective linker across the copper­(I) centers.