Bulky ligands protect molecular ruby from oxygen quenching

Abstract

Steric protection strongly reduces phosphorescence quenching of excited molecular rubies by oxygen. The most bulky ligand enables photoluminescence quantum yields up to 5.1% and lifetimes up to 518 µs in air-saturated acetonitrile.

Quantum Yield of DNA Strand Breaks under Photoexcitation of a Molecular Ruby

“…Apparently, the electrostatic interactions between the positively charged Cr III complex and the negatively charged DNA origamis lead either to a partial rigidification of the complex, hampering non‐radiative relaxation pathways, and/or a slight shielding of the emissive Cr III center from oxygen quenching. A similar luminescence enhancement of a Cr III complex under aerated conditions was only recently observed by us in the presence of bulky counter anions [40] and by employing sterically demanding ligands [41] …”

“…A similar luminescence enhancement of a Cr III complex under aerated conditions was only recently observed by us in the presence of bulky counter anions [40] and by employing sterically demanding ligands. [41] Apparent DNA binding makes the water-soluble Cr III complex a suitable PS for DNA strand break studies with the DNA origami technique. Scheme 1b) highlights the DNA strand break determination and the experimental procedure to absolutely determine the DNA strand break cross sections (σ SB ) using DNA origami nanostructures as a platform for the investigation of arbitrary DNA target sequences.…”

Charge‐Transfer und Spin‐Flip‐Zustände als sich ergänzende Gegensätze

“…Bei CT‐Emittern mit räumlich ausgedehnten angeregten Zuständen ist eine solche sterische Abschirmung jedoch aufgrund der starken Delokalisierung der 3 MLCT‐Wellenfunktion auf die Liganden eine Herausforderung [214] . Die SF‐Zustände im molekularen Rubin hingegen können durch sterisch anspruchsvolle Gruppen rund um das Metallzentrum wirksam vor äußeren Einflüssen geschützt werden [215] …”

Visible‐Light Induced Fixation of SO2 into Organic Molecules with Polypyridine Chromium(III) Complexes

“…[38][39][40][41][42] Chromium(III) complexes with polypyridine ligands have been identified as excellent photoluminescent materials with very high excited state lifetimes, even in the presence of oxygen. [43][44][45][46][47] Yet, their application in organic synthesis has so far been limited to cycloaddition reactions, singlet oxygen generation, triplet-triplet annihilation followed by cycloaddition reactions and a few photoredox catalytic cycles which mostly rely on oxygen as terminal oxidant, which can impart problems due to the formation of reactive oxygen species. [48][49][50][51][52][53][54] Herein we report the, to the best of our knowledge, first application of chromium(III) photosensitizers in the visible-light mediated fixation of SO 2 into sulfones and sulfonamides complemented by mechanistic studies.…”

“…Copper complexes have already been successfully utilized in photocatalytic C−S bond forming reactions [38–42] . Chromium(III) complexes with polypyridine ligands have been identified as excellent photoluminescent materials with very high excited state lifetimes, even in the presence of oxygen [43–47] . Yet, their application in organic synthesis has so far been limited to cycloaddition reactions, singlet oxygen generation, triplet‐triplet annihilation followed by cycloaddition reactions and a few photoredox catalytic cycles which mostly rely on oxygen as terminal oxidant, which can impart problems due to the formation of reactive oxygen species [48–54] …”