Les calmars géants

8 páginas, 6 figurasPeer reviewe

Novel Fullerene Platinum Alkynyl Complexes with High Second-Order Nonlinear Optical Properties as a Springboard for NLO-Active Polymer Films

The synthesis and second-order nonlinear optical (NLO) properties of seven novel fullerene-C₆₀ derivatives are reported. In these donor–bridge–acceptor systems, the fullerene unit (acceptor) is connected through a cyclopropane ring to an ethynyl thienyl fragment (bridge) which binds a trimethylsilyl or platinum alkynyl fragment (donor). All derivatives are NLO-active, as determined by the electric field induced second harmonic generation technique, but the fullerene platinum alkynyl complexes are characterized by a particularly large second-order NLO response. Substitution of the thienyl fragment by a terthiophene leads to an increase of the NLO performance by using trimethylsilyl as a donor group, whereas no effect is observed in the case of platinum derivatives. Remarkably, fullerene platinum alkynyl complexes can be dispersed in poly­(methyl methacrylate) or polystyrene, affording NLO-active polymer films

H‑Aggregates Granting Crystallization-Induced Emissive Behavior and Ultralong Phosphorescence from a Pure Organic Molecule

Solid-state luminescent materials with long lifetimes are the subject of ever-growing interest from both a scientific and a technological point of view. However, when dealing with organic compounds, the achievement of highly efficient materials is limited by aggregation-caused quenching (ACQ) phenomena on one side and by ultrafast deactivation of the excited states on the other. Here, we report on a simple organic molecule, namely, cyclic triimidazole (C₉H₆N₆), <b>1</b>, showing crystallization-induced emissive (CIE) behavior and, in particular, ultralong phosphorescence due to strong coupling in H-aggregated molecules. Our experimental data reveal that luminescence lifetimes up to 1 s, which are several orders of magnitude longer than those of conventional organic fluorophores, can be realized under ambient conditions, thus expanding the class of organic materials for phosphorescence applications

H‑Aggregates Granting Crystallization-Induced Emissive Behavior and Ultralong Phosphorescence from a Pure Organic Molecule

Solid-state luminescent materials with long lifetimes are the subject of ever-growing interest from both a scientific and a technological point of view. However, when dealing with organic compounds, the achievement of highly efficient materials is limited by aggregation-caused quenching (ACQ) phenomena on one side and by ultrafast deactivation of the excited states on the other. Here, we report on a simple organic molecule, namely, cyclic triimidazole (C₉H₆N₆), <b>1</b>, showing crystallization-induced emissive (CIE) behavior and, in particular, ultralong phosphorescence due to strong coupling in H-aggregated molecules. Our experimental data reveal that luminescence lifetimes up to 1 s, which are several orders of magnitude longer than those of conventional organic fluorophores, can be realized under ambient conditions, thus expanding the class of organic materials for phosphorescence applications

Cyclometalated 4‑Styryl-2-phenylpyridine Platinum(II) Acetylacetonate Complexes as Second-Order NLO Building Blocks for SHG Active Polymeric Films

The second-order nonlinear optical (NLO) properties of various Pt­(II) acetylcetonate complexes bearing a substituted cyclometalated 4-styryl-2-phenylpyridine (ppy-4-styryl-R, with R = NEt₂, OMe, H, NO₂) were investigated in DMF solution on working with an incident wavelength of 1907 nm by the EFISH technique, whereas the dipole moments were determined by density functional theory (DFT) calculations. In addition, a Pt­(II) complex with the ppy-4-styryl-NEt₂ ligand, which was the most NLO efficient chromophore due to a particularly high dipole moment, was dispersed in a polymethylmethacrylate matrix and then oriented by poling to give a composite film characterized by a good and quite stable second harmonic generation (SHG) signal

Functionalized Ruthenium Dialkynyl Complexes with High Second-Order Nonlinear Optical Properties and Good Potential as Dye Sensitizers for Solar Cells

Various dipolar π-delocalized Ru­(II) dialkynyl complexes were prepared and characterized. Their second-order nonlinear optical (NLO) properties were investigated by the electric-field-induced second harmonic generation (EFISH) technique working in CH₂Cl₂ solution with an incident wavelength of 1907 nm, whereas the dipole moments were determined by density functional theory (DFT) calculations. All the investigated complexes are characterized by a negative value of μβ_1.907 EFISH, in agreement with a negative value of Δμ_eg (difference of the dipole moment in the excited and ground state) upon excitation. Their second-order NLO response can be easily modulated by the nature of the alkynyl substituents. Besides, the most promising “push–pull” ruthenium diacetylide complex, adequately functionalized for anchoring to TiO₂, was tested as photosensitizer in dye-sensitized solar cells (DSSCs)

Second-Order NLO Switches from Molecules to Polymer Films Based on Photochromic Cyclometalated Platinum(II) Complexes

Novel photochromic dithienylethene-based platinum­(II) complexes (C^∧N^∧N)­Pt­(CCDTEC₆H₄D) ((C^∧N^∧N) = 4,4′-di­(<i>n</i>-hexyl)-6-phenyl-2,2′-bipyridine; D = H, NMe₂) were prepared and characterized. Their excellent photochromic properties allow the photoinduced switching of their second-order nonlinear optical properties in solution, as measured by the EFISH technique, due to formation of an extended π-conjugated ligand upon suitable electromagnetic radiation. Insights into the electronic structures of the complexes and the nature of their excited states have been obtained by DFT and TD-DFT calculations. These novel Pt­(II) complexes were nanoorganized in polymer films which were poled, affording new materials characterized by a good second-order NLO response that can be easily switched, with an excellent NLO contrast. To the best of our knowledge, our compounds allowed designing the very first examples of switchable NLO polymer films based on metal complexes