Through-space conjugation-dominated luminescence mechanism

The influence of through-space conjugation (TSC) on the optical properties of molecules was consistently neglected in past research. Recently, TSC-related luminescence phenomena were reported sporadically, but a general lack of in-depth understanding of the TSC luminescence mechanism exists. The TSC factors, TSC intensity, and the impact of TSC on material properties remained theoretical blind spots. This work selected cyclooctatetrathiophene (COTh) as a research model and comprehensively analyzed the nature of TSC at the experimental and theoretical levels. The COTh molecule exhibited an anomalous luminescence that did not match the degree of through-bond conjugation. Instead, it was determined to be a luminescence phenomenon dominated by TSC. A unique overpass-shaped TSC channel was the key to achieving TSC-dominated luminescence. Orbital phase, angle, and spatial distance were essential factors in forming an effective TSC channel. Moreover, both COTh isomers and aryl-substituted COTh derivatives were shown to possess TSC-dominated luminescence properties, which provided sufficient evidence for the TSC-dominated luminescence mechanism. In addition, a practical TSC analysis tool was developed that could quickly analyze the TSC path, action location, and action intensity for any molecular system. This work will provide helpful guidance and inspiration for TSC research and promote the development of TSC-related research.