BODIPY heterochromophores, asymmetrically substituted with perylene and/or iodine at the 2 and 6 positions were prepared and investigated as sensitizers for triplet‐triplet annihilation up conversion (TTA‐UC). Single‐crystal X‐ray crystallographic analyses show that the torsion angle between BODIPY and perylene units lie between 73.54 and 74.51, though they are not orthogonal. Both compounds show intense, charge transfer absorption and emission profiles, confirmed by resonance Raman spectroscopy and consistent with DFT calculations. The emission quantum yield was solvent dependent but the emission profile remained characteristic of CT transition across all solvents explored. Both BODIPY derivatives were found to be effective sensitizers of TTA‐UC with perylene annihilator in dioxane and DMSO. Intense anti‐Stokes emission was observed, and visible by eye from these solvents. Conversely, no TTA‐UC was observed from the other solvents explored, including from non‐polar solvents such as toluene and hexane that yielded brightest fluorescence from the BODIPY derivatives. In dioxane, the power density plots obtained were strongly consistent with TTA‐UC and the power density threshold, the Ith value (the photon flux at which 50 % of ΦTTAUC is achieved), for B2PI was observed to be 2.5x lower than of B2P under optimal conditions, an effect ascribed to the combined influence of spin‐orbit charge transfer intersystem crossing (SOCT‐ISC) and heavy metal on the triplet state formation for B2PI.

BODIPY‐based donor‐acceptor dyads are widely used as sensors and probes in life science. Thus, their biophysical properties are well established in solution, while their photophysical properties in cellulo, i. e., in the environment, in which the dyes are designed to function, are generally understood less. To address this issue, we present a sub‐ns time‐resolved transient absorption study of the excited‐state dynamics of a BODIPY‐perylene dyad designed as a twisted intramolecular charge transfer (TICT) probe of the local viscosity in live cells.

Vibronic and solvent effects significantly impact the radiative lifetime of a BODIPY dye.

BODIPY‐perylene dyads have emerged as useful metal free sensitizers for triplet‐triplet annihilation upconversion (TTAUC), these dyads are capable of efficient triplet generation via spin‐orbit charge transfer intersystem crossing (SOCT‐ISC). This important route to triplet formation requires dyads in which two moieties are oriented perpendicular to each other. In this contribution, we give a deeper insight on the behavior of established BODIPY‐perylene dyads, where BODIPY‐perylene dihedral exhibits non‐orthogonal dyad geometry. The intersystem crossing of BODIPY‐perylene dyads with and without iodine are investigated using femtosecond transient absorption (fs‐TA) and nanosecond transient absorption (ns‐TA) spectroscopy. The concurrent decay of the singlet charge transfer state (1CT) and rise of triplet states in both the iodinated and non‐iodinated dyads confirms the SOCT‐ISC as the main intersystem crossing pathway despite the altered geometry of the dyads. The presence of an iodine atom on the BODIPY‐moiety enables intersystem crossing 2.6‐times faster and provides a higher triplet yield with respect to dyad without iodine. The upconversion quantum yield ( ) is 8.4‐times higher in the sample containing iodinated dyad as sensitizer and perylene as annihilator. The triplet‐triplet energy transfer rate (kTTET) is ∼8×108 M−1 cm−1 for both iodinated and non‐iodinated sensitizer containing TTAUC systems in 1,4‐dioxane.

A linear sequence to access to a novel series of C-nucleosides bearing a quaternary carbon at the anomeric position tethered to a 4-substituted 1,2,3-triazole ring is described. Most of the...