Distinct Fold-Mode Formation of Crystalline Cu(I) Helical Coordination Polymers with Alternation of the Solid-State Emission Using Shape of the Counter Anions.

One-dimensional cationic coordination polymers have been a promising platform for designing solid-state physical properties through diverse coordination geometries. In particular, the folding mode of the coordination polymers that form a helical structure directly determines the metal-centered coordination environment. Herein, we report N -heterocyclic carbene (NHC) Cu(I) cationic coordination polymers with pyrazine as the linker, which construct a 4-fold or 3-fold helical column in luminescent crystals using octahedral anions (SbF 6 - and PF 6 - ) or a tetrahedral anion (BF 4 - ), respectively. Single-crystal XRD studies revealed that the folding modes depend on the structural shape of the counteranions, which form H-F interactions between ligands and anions. Indeed, the folding mode change from 4-fold to 3-fold by including a different shape of the counteranions, resulting in red-shifted emission from approximately 580 to 687 nm, which is difficult to modulate in the solid state.