Single-component-based multicolor emissions enabled by symmetry breaking.

Abstract

Excitation-dependent multicolor emission from a single-component system, independent of aggregation, remains a fundamental challenge due to inherent difficulties in innovative principles. Herein, we propose a molecular symmetry-breaking strategy to enrich electronic processes, enabling the molecule to exhibit excitation-dependent multicolor emissions from one chemical entity. A star-shaped molecule, 1,3,5-(4-tert-butylphenyl-o-carboranyl-4-phenyl)benzene (Ph-3CP) is designed, where spatial restriction induces inequivalence among three bulky, non-planar branches. This asymmetry gives rise to a broad excitation-dependent emission range of nearly 175 nm across solution, amorphous, and crystalline states. Crystallization from different solvents successfully traps distinct asymmetric conformers of Ph-3CP, providing direct experimental evidence for the predicted symmetry-breaking structures from theoretical calculations. Structure-property relationship studies further reveal two distinct relaxation pathways that dominate the emission behavior of this molecular system. Leveraging these properties, we develop a single-component fluorescence sensor array that enables rapid and selective identification of chlorinated hydrocarbon vapors. This work provides a general strategy for designing multifunctional luminescent materials through symmetry-controlled excited-state engineering.