Anion-Directed Structural Modulation and Tunable Luminescence in Copper(I)–Organic Hybrids

Abstract

Copper(I)–organic hybrid materials offer a versatile platform for integrating tunable photophysical and electronic functionalities. Herein, we report three distinct hybrid systems, [CuI(PMB)]n, [CuSCN(PMB)]n, and [CuCN(PMB)]n [PMB = 1-(pyridin-2-ylmethyl)-1H-benzimidazole], constructed via a sonochemical assembly approach. Single-crystal X-ray diffraction reveals a structural modulation from one-dimensional Cu2I2 and Cu2S2 chain motifs to a two-dimensional Cu–CN framework. The different anions generate distinct Cu(I) hybrid polymeric environments based on their bridging characteristics. All hybrids exhibit bright solid-state emission spanning cyan-green to yellow emission, with photoluminescence quantum yield of up to 51%. Temperature-dependent spectroscopy, TD-DFT calculations, and charge-density-difference analyses indicate the metal to ligand charge transfer (MLCT)/ ligand to ligand charge transfer (LLCT) character of the emissive states. Furthermore, these hybrids exhibit semiconducting behavior and are used in downconversion LEDs and luminescent anticounterfeiting inks. Overall, the distinct coordination modes and bridging characteristics of I–, SCN–, and CN– modulate the Cu(I) coordination geometry and framework connectivity, thereby tuning the local excited-state environment and solid-state luminescence without changing the organic ligand.