Red-Light-Driven Bifunctionalization of Styrene Derivatives.

A red-light-activated phthalocyanine ruthenium complex has been designed as a catalyst for the bifunctionalization of styrene derivatives. The combination of a trifluoromethylation agent resistant to nucleophiles and various nucleophiles facilitates the concurrent incorporation of a trifluoromethyl group and various functional groups onto the double bond of the substrate. This reaction demonstrates the utility of mild, low-energy, and highly transmissive long-wavelength light for intricate molecular transformations in a one-pot procedure.

Photosensitizing Metasurface Empowered by Enhanced Magnetic Field of Toroidal Dipole Resonance.

Photochemical reaction exploiting an excited triplet state (T1 ) of a molecule requires two steps for the excitation, i.e., electronic transition from the ground (S0 ) to singlet excited (S1 ) states and intersystem crossing to the T1  state. A dielectric metasurface coupled with photosensitizer that enables energy efficient photochemical reaction via the enhanced S0 →T1 magnetic dipole transition is developed. In the direct S0 →T1 transition, the photon energy of several hundreds of meV is saved compared to the conventional S0 → S1 →T1 transition. To maximize the magnetic field intensity on the surface, a silicon (Si) nanodisk array metasurface with toroidal dipole resonances is designed. The surface of the metasurface is functionalized with ruthenium (Ru(II)) complexes that work as a photosensitizer for singlet oxygen generation. In the coupled system, the rate of the direct S0 →T1 transition of Ru(II) complexes is 41-fold enhanced at the toroidal dipole resonance of a Si nanodisk array. The enhancement of a singlet oxygen generation rate is observed when the toroidal dipole resonance of a Si nanodisk array is matched with the direct S0 →T1 transition wavelength of Ru(II) complexes.

Direct Near Infrared Light-Activatable Phthalocyanine Catalysts.

The high penetration of near-infrared (NIR) light makes it effective for use in selective reactions under light-shielded conditions, such as in sealed reactors and deep tissues. Herein, we report the development of phthalocyanine catalysts directly activated by NIR light to transform small organic molecules. The desired photocatalytic properties were achieved in the phthalocyanines by introducing the appropriate peripheral substituents and central metal. These phthalocyanine photocatalysts promote cross-dehydrogenative-coupling (CDC) under irradiation with 810 nm NIR light. The choice of solvent is important, and a mixture of a reaction-accelerating (pyridine) and -decelerating (methanol) solvents was particularly effective. Moreover, we demonstrate photoreactions under visible-light-shielded conditions through the transmission of NIR light. A combined experimental and computational mechanistic analysis revealed that this NIR reaction does not involve a photoredox-type mechanism with electron transfer, but instead a singlet-oxygen-mediated mechanism with energy transfer.