A “crossbreeding” dyad strategy for bright and small-molecular weight near-infrared fluorogens: From the structural design to boost aggregation-induced emission

The development of high-performance near-infrared fluorophores has gained tremendous attention for spatiotemporally in vivo dynamical bioimaging. The proposed π-conjugated “crossbreeding” dyad strategy has led to the emergence of a new class of dyes with simple structure but stable, bright, and biocompatible. These dyads consist of two individual chromophores bridging via a short π-conjugated bridge and tending to be identical in the delocalized system, thereby affording valuable new features not retaining their parent fluorophores in the photophysical properties. This review summarizes the crossbreeding dyad backbones and advances to bring forth small-molecular weight, high molar extinction coefficients, and outstanding chemical stability. Impressively, the crossbreeding AIEgens greatly expand NIR-II emission, high stability, and good brightness for in vivo imaging intact tissues and living animals. This crossbreeding strategy could pave a new way to construct high-performance NIR dyes, showing great potentials with the extensive endorsement of NIR-II bioimaging for clinic diagnosis.