Photochemical Upconversion: Anthracene Dimerization Sensitized to Visible Light by a Ru^II Chromophore

Abstract

Verdoppelt: Photochemische Upconversion durch MLCT‐sensibilisierte Triplett‐Triplett‐Aufhebung wird gezeigt (MLCT=Metall‐Ligand‐Charge‐Transfer). Die selektive Anregung von [Ru(dmb)3]2+ (dmb=4,4′‐Dimethyl‐2,2′‐bipyridin) in Gegenwart von Anthracen mit sichtbarem Licht führt effizient zum [4+4]‐Cycloaddukt. Bisher wurde für diese Umwandlung ultraviolette Strahlung benötigt.

Ruthenium(II) Polyimine Complexes with a Long‐Lived 3IL Excited State or a 3MLCT/3IL Equilibrium: Efficient Triplet Sensitizers for Low‐Power Upconversion

“…The upconversion of the complexes was studied by using 9,10-diphenylanthracene (DPA; Figure 2 b) as the acceptor/annihilator because of its appropriate T 1 energy level (1.77 eV) and high fluorescence quantum yield (F F = 0.95). [5] The blue fluorescence of DPA was observed upon excitation of the mixture of DPA and the complexes with a 473 nm laser (Figure 2 b). The anti-Stokes shift is 0.48 eV (473 nm!400 nm).…”

“…(1) recently emerged and is believed to be promising for practical applications such as dye-sensitized solar cells. [5,6] In this approach, a sensitizer is used, which is normally a transitionmetal complex with accessible triplet excited states, such as Ru II polypyridine complexes for which the metal-to-ligand charge-transfer ( 3 MLCT) excited state can be populated by photoexcitation (e.g., [Ru(dmb) 3 ] 2+ , Scheme 1; dmb = 4,4-dimethyl-2,2-bipyridine). The sensitizer harvests the exciting light and transfers the energy to the acceptor (the annihilator, usually polycyclic aromatic hydrocarbons, such as anthracene) by triplet-triplet energy transfer (TTET).…”

Blue‐Green Up‐Conversion: Noncoherent Excitation by NIR Light

“…[2][3][4] In comparison to the above-described methods, the fundamental advantage of the triplet-triplet annihilationsupported bimolecular photon up-conversion process is its inherent independence [5] on the coherence of the excitation light. Another principal advantage [5] of this up-conversion process is the very low intensity (as low as 1 W cm À2 ) and extremely low spectral power density (as low as 600 mW nm À1 ) needed from the excitation source; thus, the source can be the sun.The process of photon up-conversion, based on triplettriplet annihilation in multimolecular systems, [5][6][7][8] is to be considered as an inherently connected chain of three processes already studied in the past. The first process in this chain is intersystem crossing (ISC), which is strongly enhanced by the spin-orbit coupling to the metal center of metalated macrocyclic sensitizer molecules.…”

Photodimerization of thioxanthone–anthracene: formation of monochromophoric Type II initiator

“…In the literature, based on the different substituents attached to anthracene, dimer proton is observed between 3.7 and 6.5. [28][29][30] While dimerization procedure was carried out under nitrogen atmosphere, δ 6.15-6.5 ppm protons belonging to endoperoxide formation were not observed. However, δ 4.00 ppm protons belong to bridgehead protons of photodimer product was seen as shown in Figure 4.…”