title: Near-Infrared-to-Visible Photon Upconversion Enabled by Conjugated Porphyrinic Sensitizers under Low-Power Noncoherent Illumination.
abstract: We report four supermolecular chromophores based on (porphinato)zinc(II) (PZn) and (polypyridyl)metal units bridged via ethyne connectivity (Pyr1RuPZn2, Pyr1RuPZnRuPyr1, Pyr1RuPZn2RuPyr1, and OsPZn2Os) that fulfill critical sensitizer requirements for NIR-to-vis triplet-triplet annihilation upconversion (TTA-UC) photochemistry. These NIR sensitizers feature: (i) broad, high oscillator strength NIR absorptivity (700 nm < λ(max(NIR)) < 770 nm; 6 × 10(4) M(-1) cm(-1) < extinction coefficient (λ(max(NIR))) < 1.6 × 10(5) M(-1) cm(-1); 820 cm(-1) < fwhm < 1700 cm(-1)); (ii) substantial intersystem crossing quantum yields; (iii) long, microsecond time scale T1 state lifetimes; and (iv) triplet states that are energetically poised for exergonic energy transfer to the molecular annihilator (rubrene). Using low-power noncoherent illumination at power densities (1-10 mW cm(-2)) similar to that of terrestrial solar photon illumination conditions, we demonstrate that Pyr1RuPZn2, Pyr1RuPZn2RuPyr1, and Pyr1RuPZnRuPyr1 sensitizers can be used in combination with the rubrene acceptor/annihilator to achieve TTA-UC: these studies represent the first examples whereby a low-power noncoherent NIR light source drives NIR-to-visible upconverted fluorescence centered in a spectral window within the bandgap of amorphous silicon.
authors.affiliation: †Department of Chemistry, French Family Science Center, 124 Science Drive, Duke University, Durham, North Carolina 27708-0346, United States.
authors.forename: Jean-Hubert
authors.initials: JH
authors.lastname: Olivier
authors.affiliation: †Department of Chemistry, French Family Science Center, 124 Science Drive, Duke University, Durham, North Carolina 27708-0346, United States.
authors.forename: Yusong
authors.initials: Y
authors.lastname: Bai
authors.affiliation: ‡Department of Chemistry, North Carolina State University, 2620 Yarbrough Drive, Raleigh, North Carolina 27695-8204, United States.
authors.forename: Hyounsoo
authors.initials: H
authors.lastname: Uh
authors.affiliation: †Department of Chemistry, French Family Science Center, 124 Science Drive, Duke University, Durham, North Carolina 27708-0346, United States.
authors.forename: Hyejin
authors.initials: H
authors.lastname: Yoo
authors.affiliation: †Department of Chemistry, French Family Science Center, 124 Science Drive, Duke University, Durham, North Carolina 27708-0346, United States.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Therien
authors.affiliation: ‡Department of Chemistry, North Carolina State University, 2620 Yarbrough Drive, Raleigh, North Carolina 27695-8204, United States.
authors.forename: Felix N
authors.initials: FN
authors.lastname: Castellano