Construction of sterically bent π-conjugated arylene by implanting into bulky NHC Cu(I) coordination polymers in crystalline media

Abstract

One-dimensional π-conjugated coordination polymers are a promising platform for tailoring solid-state physical properties through diverse coordination geometries and structural arrangements. Their tunability arises from the precise design of building blocks such as metal nodes, π-conjugated organic ligands, and counter anions, which collectively influence the coordination geometry and packing structure. While distorted π-conjugated systems such as helicenes, fullerenes, corannulenes, and cycloparaphenylenes (CPPs), exhibit unique electronic properties distinct from planar π-conjugated systems, their incorporation as ligand linkers within coordination polymers remains challenging. Herein, we report the synthesis and structural modulation of cationic N-heterocyclic carbene (NHC) Cu(I) coordination polymers bearing bis(4-pyridyl)acetylene as a π-conjugated linker and sterically bulky counter anions. By leveraging the steric effects of counter anions and modifying the π-backbone on NHC ligands, we succeeded to yield two coordination polymers possessing sterically distorted π-conjugated linkers, which are generally difficult to achieve in coordination polymers. Single-crystal X-ray diffraction (XRD) studies revealed that highly bulky counter anions inhibit close packing of NHC ligands between neighboring coordination polymer columns, leading to a tilt in the trigonal planar orientation relative to the column axis.