Photochemical upconversion and triplet annihilation limit from a boron dipyrromethene emitter. Issue 7 (11th June 2015)

• Record Type: Journal Article
• Authors: Deng, F.; Francis, A. J.; Weare, W. W.; Castellano, F. N.
• Is Part Of: Photochemical & photobiological sciences. Volume 14:Issue 7(2015:Jul.)
• Page Start: 1265
• Page End: 1270
• Publication Date: 2015-06-11
• Subjects: Photochemistry -- Periodicals; Photobiology -- Periodicals; 541.35
• DOI: 10.1039/c5pp00106d
• Languages: English
• ISSNs: 1474-905X

Abstract

Abstract : Non-coherent sensitized red-to-green upconversion has been achieved utilizing platinum(ii ) tetraphenyltetrabenzoporphyrin (PtTPTBP) as the triplet sensitizer and a nearly quantitatively fluorescent boron dipyrromethene chromophore as the energy acceptor/annihilator in deoxygenated toluene. Abstract : Non-coherent sensitized red-to-green upconversion has been achieved utilizing platinum(ii ) tetraphenyltetrabenzoporphyrin (PtTPTBP) as the triplet sensitizer and a nearly quantitatively fluorescent meso -(2, 6-dichloropyridyl)-substituted boron dipyrromethene (Cl2 PyBODIPY) chromophore ( Φ = 0.99 in toluene) as the energy acceptor/annihilator in deoxygenated toluene. Dynamic Stern–Volmer analysis revealed that PtTPTBP phosphorescence as quenched by Cl2 PyBODIPY occurs with a K SV of 108 000 M −1, yielding a triplet–triplet energy transfer rate constant of 2.3 × 10 9 M −1 s −1 . Using a non-coherent red light-emitting diode excitation source centered at 626 nm, the incident power dependence responsible for generating singlet BODIPY fluorescence in the green was shown to traverse quadratic to linear regimes, the latter being achieved near 60 mW cm −2 . These data were consistent with a photochemical upconversion mechanism being responsible for generating singlet fluorescence from the Cl2 PyBODIPY chromophores through sensitized triplet–triplet annihilation (TTA). Integrated delayed fluorescence transients were utilized to reveal the TTA efficiency for the Cl2 PyBODIPY chromophore and saturated near 46%, representing the lower limit for the TTA process. Kinetic modelling of the delayed fluorescence transient produced from 1.5 mJ laser pulses ( λ ex = 615 nm) revealed a maximum limiting TTA efficiency of 64% for this upconverting composition, implying that this is indeed an extremely relevant acceptor/annihilator composition for photochemical upconversion.