Efficient Sensitization of Europium, Ytterbium, and Neodymium Functionalized Tris-Dipicolinate Lanthanide Complexes through Tunable Charge-Transfer Excited States

International audienceA series of push−pull donor-π-conjugated dipicolinic acid ligands and related tris-dipicolinate europium and lutetium complexes have been prepared. The ligands present broad absorption and emission transitions in the visible spectral range unambiguously assigned to charge-transfer transitions (CT) by means of time-dependent density functional theory calculations. The photophysical properties (absorption, emission, luminescence quantum yield, and lifetime) of the corresponding europium complexes were thoroughly investigated. Solvatochromism and temperature effects clearly confirm that Eu(III) sensitization directly occurs from the ligand CT state. In addition, modulation of the energy of the CT donating state by changing the nature of the donor fragment allows the optimal energy of the antennae for europium sensitization to be determined, and this optimal energy was found to be close to the 5D1 accepting state. Finally, this CT sensitization process has been successfully extended to near-infrared emitters (neodymium and ytterbium)

Organic Monolithic Natural Hyperbolic Material

© 2019 American Chemical Society.Materials with hyperbolic dispersion are the key to a variety of photonic applications involving nanoimaging, hyper-lensing, and spontaneous emission engineering, due to the availability of high k modes. Here we demonstrate that spin-coated polycrystalline organic semiconducting films with a layered molecular packing structure can exhibit a hyperbolic dispersion over a wide spectral range and support the presence of surface excitonic polaritons. This was evidenced from 670 to 920 nm and is related to the negative real part of the dielectric permittivity of the selected quinoidal organic semiconductor. In addition, the accessible high k modes lead to changes in the spontaneous emission decay rate and photoluminescence quantum yield of emitters placed nearby the organic monolithic (composed of only one molecule and not necessitating an alternating multilayer structure) natural hyperbolic material. This study opens a new route toward single-step solution manufacturing of large-area, low-cost, and flexible organic photonic metadevices with hyperbolic dispersion11sciescopu