Fig. 2: Photophysical properties and molecular structures of NHNI esters.
From: Biocompatible decarboxylative coupling enabled by N-hydroxynaphthalimide esters
a Chemical structures of NHNI esters 1, 2, and 3. b Prompt PL spectra of NHNI esters 1, 2, 3 at 77 K. c Delayed PL spectra (10 ms) at 77 K. d Average phosphorescence lifetimes (τP) of NHNI esters 1, 2, 3. e Highest occupied and lowest unoccupied NTOs of NHNI esters based on time-dependent DFT calculations for the S1 state, with calculated dipole moments (Δμ) shown in the inset. The structural and photophysical properties of NHNI esters 1, 2, and 3 illustrate the relationship between singlet-triplet conversion efficiency and reaction yields. The D-A framework in esters 2 and 3 enhances phosphorescence and singlet-triplet conversion efficiency, contributing to improved reactivity under biocompatible conditions. All spectral intensities are plotted in arbitrary units (a.u., arb. units). Colors in panels b–d correspond to NHNI esters 1 (blue), 2 (green), and 3 (purple). NHNI ester N-hydroxynaphthalimide ester, NBoc tert-butoxycarbonyl, PL photoluminescence, τP phosphorescence lifetime, Φp phosphorescence quantum yield, Φf fluorescence quantum yield, NTO natural transition orbital, Δμ(S0–S1) change in dipole moment between S0 and S1 states, D–A donor–acceptor.
