The utilization of high‐energy excited states for productive chemical transformations, known as Anti‐Kasha photochemistry, is acquiring momentum as a means to expand the thermodynamic and kinetic limits of solar‐to‐chemical energy conversion. This review discusses the strategies to drive this chemistry, the concepts behind the different approaches, the progress made so far, and the current challenges.
Multiresonance thermally activated delayed fluorescence (MR‐TADF) emitters are promising for narrowband organic light‐emitting diodes (OLEDs), yet simultaneous control of emission energy, vibronic coupling, and triplet harvesting within a common framework remains challenging. Here, local chalcogen‐bridging effects are systematically investigated within a double‐boron MR‐TADF framework using unbridged DBN‐H and its O‐ and S‐bridged analogs, DBN‐O and DBN‐S . This matched series clarifies how bridge identity governs molecular geometry, vibronic coupling, and spin‐conversion dynamics. Combined photophysical measurements and computational analyses reveal that oxygen bridging rigidifies the MR framework, suppressing excited‐state structural reorganization and vibronic coupling. Consequently, DBN‐O affords narrowband deep‐blue electroluminescence at 453 nm with a full width at half maximum of 19 nm, a maximum external quantum efficiency (EQE max ) of 25.7%, and Commission Internationale de l’Éclairage (CIE) chromaticity coordinates of (0.14, 0.06), close to the Rec.2020 blue primary. In contrast, DBN‐S forms a lower‐energy, more vibronically relaxed emissive state while exhibiting accelerated reverse intersystem crossing. Together with its near‐unity photoluminescence quantum yield and horizontal transition‐dipole orientation, these characteristics enable DBN‐S ‐based OLEDs to achieve an EQE max of 31.4% with suppressed efficiency roll‐off. These results demonstrate how local O‐ and S‐bridging motifs can differentially balance spectral purity and triplet harvesting within a common double‐boron MR‐TADF framework.
Among photoremovable protecting groups (PPGs), the 7‐hydroxyquinoline‐2‐ylmethyl‐based cage stands out for versatility, potential biological applications, and tunability of photophysical properties through modification of the substitution pattern at the quinoline nucleus. The introduction of electron‐withdrawing atoms/groups (EWGs) at quinoline C(8) profoundly affects its photochemical performance. Interested in caging tertiary amines because they are prevalent in a variety of biologically active compounds and photouncaging them with biocompatible visible light, we chose N ‐benzylpyrrolidine as an aliphatic tertiary amine model and synthesized a series of N ‐benzylpyrrolidines N ‐caged with 7‐hydroxyquinoline‐2‐ylmethyl 8‐substituted with different EWGs (halogen, cyano, methylsulfonyl, trifluoromethyl, and carboxyl). Photophysical characterization of the new constructs revealed that the 8‐halo‐substituted derivatives, unlike the others, display absorbance into the visible region up to 440 nm. Consistently with such an absorption profile, the 8‐bromo‐7‐hydroxyquinoline‐2‐ylmethyl (BHQ) caged N ‐benzylpyrrolidine and, to a lesser extent, the 8‐iodo analog showed moderate N ‐benzylpyrrolidine release upon exposure to visible light (440 nm), candidating BHQ to further structure‐properties optimization aimed at improving visible light‐induced photorelease of tertiary amines.
The widespread use and improper disposal of pharmaceutical compounds pose severe risks to both human health and aquatic ecosystems. Indeed, they can be found in freshwater bodies and are a cause of concern since they hardly undergo any degradation process. In this study, we propose the use of silica‐based materials to photodegrade one of these compounds, furosemide. The reactivity of three silica materials with different morphologies (compact nanoparticles and two mesoporous nanoparticles with different porosities) has been tested under irradiation at 330 nm at three pHs. To enhance catalytic performance, the optimal silica morphology was subsequently doped with iron via a straightforward calcination protocol, yielding two modified materials with distinct iron concentrations. To gain a deeper understanding of what are the defects on the surface of silica that allow it to improve its reactivity, the prepared materials are characterized by means of SEM, zeta potential measurement, and reflectance and emission spectroscopies.
Two‐photon excitation of fluorescence dyes and proteins is widely used for imaging living systems due to reduced scattering in biological media. Two‐photon absorption properties are well‐studied, but there is very little known on two‐photon reaction dynamics. Here, we present time‐resolved vibrational spectroscopy upon one‐ and two‐photon excitation at 515 and 1030 nm, respectively, on 4‐(dicyano‐methylen)‐2‐methyl‐6‐(4‐dimethylaminostyryl)‐4H‐pyran (DCM) in dimethyl‐sulfoxide (DMSO) and tetrahydrofuran (THF) solvent. We demonstrate overall similar dynamics for both excitation regimes at about 4 and 300 GW/cm 2 . Vibrational dynamics of nitrile stretching demonstrate small conformational changes within 0.4 ps in both solvents and an additional conformational change within 1 ps in DMSO. This new method provides detailed information on vibrational properties in the electronic excited state, fosters our understanding and use of two‐photon spectroscopy.
