Highly photostable ketopyrrolyl-BODIPYs with red aggregation-induced emission characteristics for ultrafast wash-free mitochondria-targeted bioimaging

Mitochondrial Targeting and Imaging with Small Organic Conjugated Fluorophores: A Review

“…Nonetheless, to exert a significant effect on the photophysical properties of the system, such peripheral alterations must be conjugated to the core motif. Importantly, substitutions on this position have been reported to often lead to alternative radiationless deactivation pathways with the associated detrimental effect of diminishing the fluorescence quantum efficiency (e. g., φ f =0.63, 0.33 and 0.04 for 4 , 5 and 6 in phosphate buffered saline (PBS), respectively) [65,67,75] . This can be alleviated via ortho‐substitution, resulting in out of plane re‐arrangement of the meso substituents with respect to the planar BODIPY core motif (φ f =0.88 for 7 in acetonitrile) [78] …”

“…Importantly, substitutions on this position have been reported to often lead to alternative radiationless deactivation pathways with the associated detrimental effect of diminishing the fluorescence quantum efficiency (e. g., φ f = 0.63, 0.33 and 0.04 for 4, 5 and 6 in phosphate buffered saline (PBS), respectively). [65,67,75] This can be alleviated via ortho-substitution, resulting in out of plane rearrangement of the meso substituents with respect to the planar BODIPY core motif (φ f = 0.88 for 7 in acetonitrile). [78] Whilst such approaches would limit the bathochromic effect normally associated to meso substitutions, impaired rotation ensures large quantum efficiencies.…”

“…Subtle peripheral alterations, such as simultaneous H for Me on the ketopyrrolyl meso and position 2 in 8 and 9, respectively, can lead to bathochromic changes (λ em max = 548 and 573 nm for 8 and 9 in dichloromethane (DCM), respectively) whilst maintaining intentionally sought negligible quantum yields. [75] In some cases, such low quantum efficiencies are judiciously designed to access probes able to ratiometrically report on the concentration of a particular mitochondrial analyte by changes in their fluorescence intensity. [55] Although this can be achieved through heavy atom substitutions on positions 2 and/or 6 (e. g., φ f = 1.00, 0.17, 0.08 for 10, 11 and 12 in ethanol, respectively), [59,60,65] it is primarily accessed through intramolecular photoinduced electron transfer processes such as in a neutral phenothiazine-containing BODIPY (13).…”

“…Whilst such approaches would limit the bathochromic effect normally associated to meso substitutions, impaired rotation ensures large quantum efficiencies. Subtle peripheral alterations, such as simultaneous H for Me on the ketopyrrolyl meso and position 2 in 8 and 9 , respectively, can lead to bathochromic changes (λ em max =548 and 573 nm for 8 and 9 in dichloromethane (DCM), respectively) whilst maintaining intentionally sought negligible quantum yields [75] . In some cases, such low quantum efficiencies are judiciously designed to access probes able to ratiometrically report on the concentration of a particular mitochondrial analyte by changes in their fluorescence intensity [55] .…”

Ultra-small NIR J-aggregates of BODIPY for potent phototheranostics

“…15–23 More intriguingly, the optical performance of BODIPY chromophores can be modulated by diverse functionalization and aggregation of molecules. 24–47 Moreover, the J-aggregates of BODIPY endow them with distinct advantages over those of monomers, which bring about considerably bathochromic-shifted absorption, low radiation transition, and high photostability. Several BODIPY-based PTAs have been reported to have J-aggregation behaviors.…”