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Piling up excited states to reach upconversion (UC) is severely restricted by vibrational quenching mechanisms, especially when one looks at discrete molecular entities in solution. By carefully controlling the supramolecular assembly processes resulting from the strong electrostatic interactions between negatively charged Yb complexes and Tb 3+ cations in aqueous solutions, we engineered the formation of heteropolynuclear complexes of [(YbL) 2 Tb x ] compositions (x = 1 and 2). These edifices display a phenomenon of cooperative photosensitization UC with green emission of the Tb cations upon NIR excitation at 980 nm in the Yb absorption band. The photophysical properties of the complexes were carefully investigated by steady-state and time-resolved luminescence experiments in D 2 O, allowing to quantify the impact of the composition and pD of the solution on the emission intensity, as well as clarifying the exact cooperative photosensitization upconversion mechanism. Using optimized conditions, the energy transfer UC process could be observed for the first time in non-deuterated water with discrete molecular compounds.

Two functional ethynyl-pyrene derivatives have been designed and synthesized by di- and tetra-substitutions of bromo pyrene derivatives with N-(4-ethynylphenyl)-3,4,5-tris(hexadecyloxy)benzamide fragments. The photoluminescence wavelength of the pyrene core can be tuned by the substitution pattern and the state of matter (solid, solution, gel, or liquid crystal). The disubstituted pyrene derivative 1 is not mesomorphic but produces robust and highly fluorescent gels in DMF, toluene, and cyclohexane. The well-defined fibers and ropes of the gel states were characterized by SEM and laser scanning confocal microscopy, and extended over several micrometers. The gels were integrated as active layers in field-effect transistors, which provided good bulk electron and hole charge mobilities as well as light emission generation. The tetra-substituted pyrene derivative is not a gelator but displays a stable liquid crystalline phase with 2D hexagonal symmetry between 20 and 200 degrees C. The pronounced luminescence properties of the mesophase allow one to observe original mesophase textures with flower-like patterns directly by fluorescence microscopy without crossed-polarizers.

Luminescent platinum-terpyridine or orthometalated bipyridine complexes have engendered widespread interest as functional materials, in particular stemming from their intense phosphorescence in the visible region of the electromagnetic spectrum. [1] These stable, neutral or ionic complexes have been widely used as electroluminescent thin films or as dopants in organic light-emitting devices (OLEDs), [2] as DNA intercalators, [3] and molecular probes for biological macromolecules. [4] In some cases, the ligand design, [5] the solvent, [6] or the use of soluble polymers induces metal···metal and p-p stacking interactions, which allow the tuning of the optical properties over a large spectral range. [7] Such intermolecular features are most useful for the engineering of liquid crystals and organogelators, for which intermolecular interactions are critical. [8] Rodlike metal alkynyl complexes of Pd II , Pt II , Rh I , and Hg I exhibit thermotropic liquid-crystalline properties, [9] and metal-poly(yne) polymers form lyotropic liquid crystals. [10] However, as a result of the shape and anisotropy introduced by the alkynyl tethers, most of these complexes exhibit only lamellar (SmA) and nematic mesophases. Also, the absence of p-accepting chromophores results in non-luminescent materials, which notably limits their practical utilization in energy-conversion devices (OLEDs, solar cells, etc.). While phosphorescent organogels of quinolinol platinum(II) complexes have recently been characterized, there was no indication of metal···metal interactions that might provide an additional mechanism for the control of their properties. [11] Thus, the construction of well-organized phosphorescent architectures remains an important objective, with the essential features being the need to incorporate 1) heavy metals to favor spin-orbit coupling for phosphorescence, 2) ligand tailoring to facilitate intermolecular interaction through hydrogen bonding (e.g. amide vectors) or p-p interactions through polyaromatic and/or polyimine fragments, and 3) d 8 -transition metals which are known to favor square-planar structures, thus facilitating metal-metal interactions. Here, we disclose our results on organogels and mesomorphic materials obtained through such a strategy.Syntheses of the pivotal ethynyl platforms 1 a-c were based on gallate-substituted derivatives with methyl, dodecyl (C 12 H 25 ), or phytol-like (C 20 H 41 ) substituents. [12] The final complexes were prepared by a cross-coupling reaction under anaerobic conditions between the terminal ethynyl derivatives and [(terpy)PtCl]BF 4 (terpy = 2,2':6',6''-terpyridine). [13] The reaction is catalyzed by CuI (ca. 6 mol %), and triethylamine is required to quench the nascent HCl. The deep-red complexes 2 a-c were obtained in good yields after column chromatography and crystallization from a mixture of dichloromethane/methanol and further fully characterized by NMR and FTIR spectroscopy, ESI mass spectrometry, and elemental analysis.

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Supramolecular gels and liquid-crystalline materials containing borondipyrromethene (F-Bodipy) are a new class of highly luminescent materials built by attachment of long-chain alkoxydiacylamido scaffoldings to boradiazaindacene templates. Robust gels were formed in nonane, and luminescence spectroscopy was used to probe the aggregation processes of the flat indacene cores. Coincidently, columnar mesophase was obtained from the pure material over a wide temperature range, allowing textural observations by fluorescence microscopy.

A strip of a liquid crystal elastomer doped with a near-infrared dye with one side crosslinked monodomain and the other crosslinked polydomain along the thickness behaves like a multifunctional photoactuator without the need for a support. A flat strip with two ends fixed on substrate surface forms a moving bump under laser scanning, which can be used as light-fueled conveyor to transport an object. Cutting off and laser scanning the bump with two free ends makes a soft and flexible millimeter-scale crawler that can not only move straight and climb an inclined surface, but also undergo light-guided turning to right or left as a result of combined out-of-plane and in-plane actuation. Based on the self-shadowing mechanism, with one end of the strip fixed on substrate surface, it can execute a variety of autonomous arm-like movements under constant laser illumination, such as bending-unbending and twisting, depending on the laser incident angles with respect to the strip actuator.

The present work describes the synthesis of difluoro‐boradiazaindacenes (Bodipy) functionalized at the central 8‐position by phenylamino moieties easily transformable into phenyl amide scaffoldings. Molecules carrying three linear or branched chains were prepared and characterized. An X‐ray crystal structure for the pivotal trimethoxyphenyl‐Bodipy derivative was determined, and the packing is discussed in terms of molecular interactions; a key feature for the formation of thin films. All of the dyes are thermally stable up to 170 °C but no liquid‐crystalline phases are observed. Reversible reduction and oxidation processes occur around +0.97 and −1.34 V, respectively, versus saturated calomel electrode in solution and the electroactivity and photoluminescence are maintained in thin films produced by vacuum evaporation. Interestingly, two distinct emissions are observed at 550 and 635 nm by electroluminescence of the trimethoxyphenyl‐Bodipy derivative, corresponding to the luminescence of isolated molecules and dimers, respectively. Doping Alq3 films with this Bodipy molecule by vacuum evaporation produces organic light‐emitting diodes (OLEDs) in which very efficient energy transfer from the Alq3 matrix to the Bodipy occurs by a resonance mechanism involving the first Bodipy excited state. Yellow light (550 nm, 344 cd m−2 at 15 V) is emitted at low doping concentration (7 mol %), whereas red light (635 nm, 125 cd m−2 at 15 V) is emitted at higher concentration (19 mol %). Dispersion of the Bodipy into a fluorescent poly(N‐vinylcarbazole) polymer (PVK) (≈3 mol % per repeating unit of PVK) by solution processing exclusively produces yellow emission owing to the isolated Bodipyfluorophore (550 nm, 213 cd m−2 at 15 V). The second excited state of the Bodipy dye is likely involved during energy transfer from the PVK matrix.