Light-Harvesting Fullerene Dyads as Organic Triplet Photosensitizers for Triplet–Triplet Annihilation Upconversions

Visible light-harvesting C₆₀–bodipy dyads were devised as universal organic triplet photosensitizers for triplet–triplet annihilation (TTA) upconversion. The antennas in the dyad were used to harvest the excitation energy, and then the singlet excited state of C₆₀ will be populated via the intramolecular energy transfer from the antenna to C₆₀ unit. In turn with the intrinsic intersystem crossing (ISC) of the C₆₀, the triplet excited state of the C₆₀ will be produced. Thus, without any heavy atoms, the triplet excited states of organic dyads are populated upon photoexcitation. Different from C₆₀, the dyads show strong absorption of visible light at 515 nm (<b>C-1</b>, ε = 70400 M^–1 cm^–1) or 590 nm (<b>C-2</b>, ε = 82500 M^–1 cm^–1). Efficient intramolecular energy transfer from the bodipy moieties to C₆₀ unit and localization of the triplet excited state on C₆₀ were confirmed by steady-state and time-resolved spectroscopy as well as DFT calculations. The dyads were used as triplet photosensitizers for TTA upconversion, and an upconversion quantum yield up to 7.0% was observed. We propose that C₆₀–organic chromophore dyads can be used as a general molecular structural motif for organic triplet photosensitizers, which can be used for photocatalysis, photodynamic therapy, and TTA upconversions

Efficient Enhancement of the Visible-Light Absorption of Cyclometalated Ir(III) Complexes Triplet Photosensitizers with Bodipy and Applications in Photooxidation and Triplet–Triplet Annihilation Upconversion

We report molecular designing strategies to enhance the effective visible-light absorption of cyclometalated Ir­(III) complexes. Cationic cyclometalated Ir­(III) complexes were prepared in which boron–dipyrromethene (Bodipy) units were attached to the 2,2′-bipyridine (bpy) ligand via −CC– bonds at either the <i>meso</i>-phenyl (<b>Ir-2</b>) or 2 position of the π core of Bodipy (<b>Ir-3</b>). For the first time the effect of π conjugating (<b>Ir-3</b>) or tethering (<b>Ir-2</b>) of a light-harvesting chromophore to the coordination center on the photophysical properties was compared in detail. Ir­(ppy)₂(bpy) (<b>Ir-1</b>; ppy = 2-phenylpyridine) was used as model complex, which gives the typical weak absorption in visible range (ε < 4790 M^–1 cm^–1 in region > 400 nm). <b>Ir-2</b> and <b>Ir-3</b> showed much stronger absorption in the visible range (ε = 71 400 M^–1 cm^–1 at 499 nm and 83 000 M^–1 cm^–1 at 527 nm, respectively). Room-temperature phosphorescence was only observed for <b>Ir-1</b> (λ_em = 590 nm) and <b>Ir-3</b> (λ_em = 742 nm). <b>Ir-3</b> gives RT phosphorescence of the Bodipy unit. On the basis of the 77 K emission spectra, nanosecond transient absorption spectra, and spin density analysis, we proposed that Bodipy-localized long-lived triplet excited states were populated for <b>Ir-2</b> (τ_T = 23.7 μs) and <b>Ir-3</b> (87.2 μs). <b>Ir-1</b> gives a much shorter triplet-state lifetime (0.35 μs). Complexes were used as singlet oxygen (¹O₂) photosensitizers in photooxidation. The ¹O₂ quantum yield of <b>Ir-3</b> (Φ_Δ = 0.97) is ca. 2-fold of <b>Ir-2</b> (Φ_Δ = 0.52). Complexes were also used as triplet photosensitizer for TTA upconversion; upconversion quantum yields of 1.2% and 2.8% were observed for <b>Ir-2</b> and <b>Ir-3</b>, respectively. Our results proved that the strong absorption of visible light of <b>Ir-2</b> failed to enhance production of a triplet excited state. These results are useful for designing transition metal complexes that show <i>effective</i> strong visible-light absorption and long-lived triplet excited states, which can be used as ideal triplet photosensitizers in photocatalysis and TTA upconversion

Acid/Base-Controllable FRET and Self-Assembling Systems Fabricated by Rhodamine B Functionalized Pillar[5]arene-Based Host–Guest Recognition Motifs

A novel supramolecular Föster resonance energy transfer (FRET) system was fabricated by utilizing rhodamine B (<b>RB</b>) functionalized pillar[5]­arene (<b>EtP5-RB</b>) and cyano-modified boron dipyrromethene (<b>BDP-CN</b>) based on their host–guest recognition at 5.0 × 10^–5 M, which could be turned “on” and “off” by adding trifluoroacetic acid (TFA) and triethylamine (TEA), respectively. At a higher concentration (1.0 × 10^–4 M) in acetone, <b>EtP5-RB</b> self-assembled into vesicles while <b>EtP5-RBH</b> self-assembled into nanoribbons. After the addition of <b>BDP-CN</b>, both <b>EtP5-RB</b>⊃<b>BDP-CN</b> and <b>EtP5-RBH</b>⊃<b>BDP-CN</b> self-assembled into nanoparticles, which caused the fluorescence of the host–guest complexes to be quenched

Deracemization of Racemic Amine Using ω‑Transaminase and a Nickel-Based Nanocatalyst

Chiral amines are key building blocks for the development of numerous bioactive compounds. In this study, we developed a concurrent chemoenzymatic cascade approach using ω-transaminase for the isomeric configuration inversion of a racemic amine mixture. One isomer was transaminated using ω-transaminase, generating coproduct ketones and an additional chiral substance. Then, the mixture underwent selective reductive amination of a ketone using a specially designed compatible nickel-based nanocatalyst, which transformed coproduct ketone to racemic amines while leaving the opposite enantiomer unchanged. The combination of the two steps in one reaction system functions as an overall isomeric configuration inversion system. Moreover, the desired chiral amines with an additional chiral substance were formed. The procedure consumed NH3 and generated H2O as the sole byproduct

Highly Emissive Self-Assembled BODIPY-Platinum Supramolecular Triangles

Light-emitting supramolecular coordination complexes (SCCs) have been widely studied for applications in the chemical and biological sciences. Herein, we report the coordination-driven self-assembly of two highly emissive platinum­(II) supramolecular triangles (<b>1</b> and <b>2</b>) containing BODIPY-based bridging ligands. The metallacycles exhibit favorable anticancer activities against HeLa cells (IC₅₀ of 6.41 and 2.11 μM). The characteristic ∼570 nm fluorescence of the boron dipyrromethene (BODIPY) moieties in the metallacycles permits their intracellular visualization using confocal microscopy. Additionally, the BODIPY fluorophore is an excellent photodynamic agent, making the metallacycles as ideal therapeutics for photodynamic therapy (PDT) and chemotherapy. In vitro studies demonstrate that the combination indexes against HeLa cells are 0.56 and 0.48 for <b>1</b> and <b>2</b>, respectively, confirming their synergistic anticancer effect. More importantly, these SCCs also exhibit superior anticancer efficacy toward cisplatin-resistant A2780cis cell line by combining PDT and chemotherapy, showing promise in overcoming drug resistance. This study exploits a multicomponent approach to self-assembled metallacages that enables design of effective theranostic agents wherein the platinum acceptors are toxic chemotherapeutics and the BODIPY donors are imaging probes and photosensitizers. Since each piece may be independently tuned, i.e., Pt­(II) polypyridyl fragment swapped for Pt­(II) phosphine, the activity may be optimized without a total redesign of the system

Highly Emissive Self-Assembled BODIPY-Platinum Supramolecular Triangles

Light-emitting supramolecular coordination complexes (SCCs) have been widely studied for applications in the chemical and biological sciences. Herein, we report the coordination-driven self-assembly of two highly emissive platinum­(II) supramolecular triangles (<b>1</b> and <b>2</b>) containing BODIPY-based bridging ligands. The metallacycles exhibit favorable anticancer activities against HeLa cells (IC₅₀ of 6.41 and 2.11 μM). The characteristic ∼570 nm fluorescence of the boron dipyrromethene (BODIPY) moieties in the metallacycles permits their intracellular visualization using confocal microscopy. Additionally, the BODIPY fluorophore is an excellent photodynamic agent, making the metallacycles as ideal therapeutics for photodynamic therapy (PDT) and chemotherapy. In vitro studies demonstrate that the combination indexes against HeLa cells are 0.56 and 0.48 for <b>1</b> and <b>2</b>, respectively, confirming their synergistic anticancer effect. More importantly, these SCCs also exhibit superior anticancer efficacy toward cisplatin-resistant A2780cis cell line by combining PDT and chemotherapy, showing promise in overcoming drug resistance. This study exploits a multicomponent approach to self-assembled metallacages that enables design of effective theranostic agents wherein the platinum acceptors are toxic chemotherapeutics and the BODIPY donors are imaging probes and photosensitizers. Since each piece may be independently tuned, i.e., Pt­(II) polypyridyl fragment swapped for Pt­(II) phosphine, the activity may be optimized without a total redesign of the system

Highly Emissive Self-Assembled BODIPY-Platinum Supramolecular Triangles

Light-emitting supramolecular coordination complexes (SCCs) have been widely studied for applications in the chemical and biological sciences. Herein, we report the coordination-driven self-assembly of two highly emissive platinum­(II) supramolecular triangles (<b>1</b> and <b>2</b>) containing BODIPY-based bridging ligands. The metallacycles exhibit favorable anticancer activities against HeLa cells (IC₅₀ of 6.41 and 2.11 μM). The characteristic ∼570 nm fluorescence of the boron dipyrromethene (BODIPY) moieties in the metallacycles permits their intracellular visualization using confocal microscopy. Additionally, the BODIPY fluorophore is an excellent photodynamic agent, making the metallacycles as ideal therapeutics for photodynamic therapy (PDT) and chemotherapy. In vitro studies demonstrate that the combination indexes against HeLa cells are 0.56 and 0.48 for <b>1</b> and <b>2</b>, respectively, confirming their synergistic anticancer effect. More importantly, these SCCs also exhibit superior anticancer efficacy toward cisplatin-resistant A2780cis cell line by combining PDT and chemotherapy, showing promise in overcoming drug resistance. This study exploits a multicomponent approach to self-assembled metallacages that enables design of effective theranostic agents wherein the platinum acceptors are toxic chemotherapeutics and the BODIPY donors are imaging probes and photosensitizers. Since each piece may be independently tuned, i.e., Pt­(II) polypyridyl fragment swapped for Pt­(II) phosphine, the activity may be optimized without a total redesign of the system