Abstract
J-aggregation is an efficient strategy for the development of fluorescent imaging agents in the second near-infrared window. However, the design of the second near-infrared fluorescent J-aggregates is challenging due to the lack of suitable J-aggregation dyes. Herein, we report meso-[2.2]paracyclophanyl-3,5-bis-N,N-dimethylaminostyrl BODIPY (PCP-BDP2) as an example of BODIPY dye with J-aggregation induced the second near-infrared fluorescence. PCP-BDP2 shows an emission maximum at 1010 nm in the J-aggregation state. Mechanism studies reveal that the steric and conjugation effect of the PCP group on the BODIPY play key roles in the J-aggregation behavior and photophysical properties tuning. Notably, PCP-BDP2 J-aggregates can be utilized for lymph node imaging and fluorescence-guided surgery in the nude mouse, which demonstrates their potential clinical application. This study demonstrates BODIPY dye as an alternate J-aggregation platform for developing the second near-infrared imaging agents.
Highlights
J-aggregation is an efficient strategy for the development of fluorescent imaging agents in the second near-infrared window
To dismiss the strongly π–π interactions between the indacene plane and subsequently achieve the goal of J-aggregation, we introduced a PCP group with a three-dimension structure, to the meso-position of the BODIPY core
Different from the aggregation-caused J-aggregates emission enhancement of PCP-BDP1 and PCP-BDP2, the emission of both two compounds was gradually decreased, and no J-aggregates emission was observed (Supplementary Fig. 14). These results suggest that H-aggregationinduced emission quenching dominated the photophysical properties of Ph-BDP1 and Ph-BDP2 in the aggregation state, which further demonstrated the key role that PCP group plays in the Jaggregation behavior of PCP-BDP1 and PCP-BDP2
Summary
J-aggregation is an efficient strategy for the development of fluorescent imaging agents in the second near-infrared window. This study demonstrates BODIPY dye as an alternate J-aggregation platform for developing the second near-infrared imaging agents. NIR-II dyes are mainly derived from the polymethine skeleton[6,7,8,9,10,11] and benzobisthiadiazole core[2,12,13,14,15,16,17,18], and rare examples are developed based on BODIPY19–22, squaraine[23], as well as rhodamine[24]. J-aggregates, in which the transition dipole moments of individual molecules are in slip-stacked alignment, usually display different photophysical properties from those of monomers including red-shifted absorption and fluorescence spectra and enhanced quantum yields[25,26,27]. Rare fluorescent dyes show J-aggregation behavior except for cyanine, perylenediimide, chlorophylls, and squaranines[23,27,28,29,31,32,33,34,35]
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