Sulfur‐Bridged Pure Organic Ester Clusters Exhibiting Near‐Infrared Fluorescence

Abstract The development of near‐infrared (NIR) luminophores offers significant potential in the life sciences, yet constructing pure organic clusteroluminescence (CL) from nonconjugated polymers via through‐space interaction (TSI) remains a substantial challenge. Herein, it is revealed that sulfur (S) functions as a bridge between isolated ester groups in small molecule models, facilitating ( n , π*) transitions. Building on this, RCP1 ‐ RCP5 and P1 ‐ P4 are synthesized to produce pure organic NIR‐CL luminophores. The introduction of S enhances chain clustering in polyesters and modulates inter‐/intra‐chain TSI, while micro‐folding within chains promotes clustering of adjacent ester groups and S atoms, resulting in a marked redshift. Notably, P4 displayed a fluorescence peak at 800 nm, extending to 883 nm, which sets a new record for CL. Additionally, full‐color fluorescent fibers are fabricated and explored the application of clusteroluminescent dyes. This work deepens the understanding of CL mechanisms and provides critical insights for developing high‐efficiency organic clusteroluminescent materials.