Solvent-Induced Crystal Engineering for Enhanced Room-Temperature Phosphorescence in Copper(I) Iodide Clusters

Abstract

Based on crystalline polymorphism, we utilized a solvent-mediated crystal engineering strategy to synthesize three polymorphic copper-iodide clusters, 1 [Cu4I4(4-dpda)4], 1-Tol [Cu4I4(4-dpda)4·C7H8], and 1-PX [Cu4I4(4-dpda)4·C8H10] (4-dpda = 4-(diphenylphosphino)-N,N-dimethylaniline), respectively. The polymorphic clusters not only exhibit significant differences in their crystal structures but also manifest remarkable changes in their room-temperature phosphorescence (RTP), high energy (HE)/ low energy (LE) energy transfer barriers, and thermal quenching properties. Through comprehensive analysis of single crystal structure, spectroscopic measurements and theoretical calculation, we elucidated the distinct mechanisms by which solvent-mediated crystal engineering enhances RTP performance. Furthermore, based on the significantly enhanced thermochromic effect, potential of 1-Tol as a luminescent thermometer with dual-temperature-zone response characteristics was explored, achieving a notable improvement in sensitivity in the low-temperature region. In contrast, 1-PX broadened the response range of thermochromic sensing.