Unraveling multichannel charge transfer via piezochromic behavior in copper-phenylacetylide

The intrinsic competition among multiple charge-transfer (CT) pathways in copper-phenylacetylide (PhC₂Cu) has hindered the desirable development of its photoactive properties, whereas substantial spectral and temporal overlap among these pathways has obscured direct mechanistic understanding. Herein, hydrostatic pressure is employed as a clean and reversible external stimulus to continuously compress the one-dimensional Cu(I)-Cu(I) ladder in pristine PhC₂Cu without modifying its chemical composition. In situ high-pressure photoluminescence and transient absorption spectroscopy reveal a pressure-induced evolution of CT from copper to the acetylide carbon. High-pressure crystallographic analysis and X-ray absorption near-edge structure measurements demonstrate that anisotropic contraction of the Cu(I) ladder reconstructs the copper coordination environment and consequently modulates the relative contributions of metal-to-ligand CT pathways. These structure-dependent electronic dynamics provide direct insight into the CT mechanism of PhC₂Cu and establish hydrostatic pressure as a general and non-destructive strategy for investigating CT processes in one-dimensional (1D) coordination compounds.