Near-Infrared-to-Visible Photon Upconversion Sensitized by a Metal Complex with Spin-Forbidden yet Strong S₀–T₁ Absorption

Near-infrared (NIR)-to-visible (vis) photon upconversion (UC) is useful for various applications; however, it remains challenging in triplet–triplet annihilation-based UC, mainly due to the energy loss during the S₁-to-T₁ intersystem crossing (ISC) of molecular sensitizers. In this work, we circumvent this energy loss by employing a sensitizer with direct S₀-to-T₁ absorption in the NIR region. A mixed solution of an osmium complex having a strong S₀–T₁ absorption and rubrene emitter upconverts NIR light (λ = 938 nm) to visible light (λ = 570 nm). Sensitizer-doped emitter nanoparticles are prepared by re-precipitation and dispersed into an oxygen-barrier polymer. The obtained composite film shows a stable NIR-to-vis UC emission based on triplet energy migration (TEM), even in air. A high UC quantum yield of 3.1% is observed for this TEM-UC system, expanding the scope of molecular sensitizers for NIR-to-vis UC

Directional Energy Transfer in Mixed-Metallic Copper(I)–Silver(I) Coordination Polymers with Strong Luminescence

Strongly luminescent mixed-metallic copper­(I)–silver­(I) coordination polymers with various Cu/Ag ratio were prepared by utilizing the isomorphous relationship of the luminescent parent homometallic coordination polymers (Φ_em = 0.65 and 0.72 for the solid Cu and Ag polymers, respectively, at room temperature). The mixed-metallic polymer with the mole fraction of copper even as low as 0.005 exhibits a strong emission (Φ_em = 0.75) from only the copper sites as the result of the efficient energy migration from the silver to the copper sites. The migration rates between the two sites were evaluated from the dependence of emission decays upon the mole fraction of copper

Proton-Coupled Electron Transfer and Lewis Acid Recognition at Self-Assembled Monolayers of an Oxo-Bridged Diruthenium(III) Complex Functionalized with Two Disulfide Anchors

A new μ-oxo-bis­(μ-acetato)­diruthenium­(III) complex bearing two pyridyl disulfide ligands {[Ru₂(μ-O)­(μ-OAc)₂(bpy)₂(L_py‑SS)₂]­(PF₆)₂ (OAc = CH₃CO₂^–, bpy = 2,2′-bipyridine, L_py‑SS = (C₅H₄N)­CH₂NHC­(O)­(CH₂)₄CH­(CH₂)₂SS) (<b>1</b>)} has been synthesized to prepare self-assembled monolayers (SAMs) on the Au(111) electrode surface. The SAMs have been characterized by contact-angle measurements, reflection–absorption surface infrared spectroscopy, cyclic voltammetry, and reductive desorption experiments. The SAMs exhibited proton-coupled electron transfer (PCET) reactions when the electrochemistry was studied in aqueous electrolyte solution (0.1 M NaClO₄ with Britton–Robinson buffer to adjust the solution pH). The potential–pH plot (Pourbaix diagram) in the pH range from 1 to 12 has established that the dinuclear ruthenium moiety was involved in the interfacial PCET processes with four distinct redox states: Ru^IIIRu^III(μ-O), Ru^IIRu^III(μ-OH), Ru^IIRu^II(μ-OH), and Ru^IIRu^II(μ-OH₂). We also demonstrated that the interfacial redox processes were modulated by the addition of Lewis acids such as BF₃ or Al³⁺ to the electrolyte media, in which the externally added Lewis acids interacted with μ-O of the dinuclear moiety within the SAMs

Synthesis and Properties of the Cyano Complex of Oxo-Centered Triruthenium Core [Ru₃(μ₃‑O)(μ-CH₃COO)₆(pyridine)₂(CN)]

The preparation and properties of a new cyano complex containing the Ru₃(μ₃-O) core, [Ru₃(μ₃-O)­(μ-CH₃COO)₆(py)₂(CN)] (<b>1</b>; py = pyridine), are reported. Complex <b>1</b> in CH₂Cl₂ showed intense absorption bands at 244, 334, and 662 nm, corresponding to a π–π* transition of the ligand, cluster-to-ligand charge transfer, and intracluster transitions, respectively. The cyclic voltammogram of <b>1</b> in 0.1 M (<i>n</i>-Bu)₄NPF₆–CH₂Cl₂ showed redox waves for the processes Ru₃^II,II,III/Ru₃^II,III,III, Ru₃^II,III,III/Ru₃^III,III,III, and Ru₃^III,III,III/Ru₃^III,III,IV at <i>E</i>_1/2 = −1.49, −0.26, and +1.03 V vs Ag/AgCl, respectively. The first two redox potentials are more negative by ca. 0.2 V in comparison with the corresponding potentials of [Ru₃(μ₃-O)­(μ-CH₃COO)₆(py)₃]⁺. This is in sharp contrast to the positive shifts of the corresponding waves of [Ru₃^II,III,III(μ₃-O)­(μ-CH₃COO)₆(py)₂(CO)]. Density functional theory (DFT) calculations of [Ru₃^II,III,III(μ₃-O)­(μ-CH₃COO)₆(py)₃], [Ru₃^II,III,III(μ₃-O)­(μ-CH₃COO)₆(py)₂(CN)]⁻, and [Ru₃^II,III,III(μ₃-O)­(μ-CH₃COO)₆(py)₂(CO)] showed that the positive charge of the ruthenium is delocalized over the triruthenium cores of the first two and is localized as Ru^II(CO)­{Ru^III(py)}₂ in the CO complex. The calculations explain the difference in the π interactions of the two ligands with the triruthenium cores