This work describes a new approach to construct highly conjugated molecules with asymmetric donor-acceptor-donor' architectures (DÀ AÀ D'). Five new emissive compounds featuring thiazole, a scarcely used acceptor, were synthesized using a three-component Rh(II) catalytic reaction. The asymmetric fluorescent compounds show significant emission in solution (QY = 73 %-100 %) and the solid-state (QY = 14 %-59 %), and therefore considered Dual-State Emitters (DSE). We also evaluate the impact of O-alkyl chains with varying lengths in the photophysical properties in solution, aggregates, and solid-state. Computational studies indicate that the involved electronic transitions have a significant charge transfer character produced almost exclusively from the triphenylamine donors. According to the single crystal X-ray data of compounds 8 and 9, the conjugated structures have a twisted molecular conformation that contributes to the observed emission in the solid-state. These findings show a systematic approach to design DSE materials, which may help to stimulate their use in biological or optoelectronic applications.
The Cover Feature shows 2,5‐disubstituted thiazole fluorescent dyes with an emergent phenomenon called dual‐state emission (DSE). The cover shows the sunset in the courtyard of the famous UNAM library building in harmony with the glowing compounds. The cover image was designed by Armando Navarro Huerta (Institute of Chemistry of UNAM). More information can be found in the Research Article by J. L. Belmonte‐Vázquez, B. Rodríguez‐Molina et al.
Herein, we describe a series of molecular rotors formed by cocrystallizing three indolo[3,2-b]carbazole (ICZ) derivatives with butyl and cyclohexyl substituents, along with 1,4-diaza[2.2.2]bicyclooctane (DABCO). The structures of rotors I and III were confirmed through single-crystal X-ray diffraction (SCXRD), revealing a concatenated 1D arrangement between the two components. Variable-temperature (VT) SCXRD experiments on rotors I and III suggested that the rotator shows rotational motion, with activation energies of 6.8 and 1.8 kcal mol −1 , respectively. The lower activation energy for rotor III was attributed to the flexible environment around DABCO due to the presence of cyclohexyl groups, while the surroundings of rotor I were found to be more rigid. Additionally, our predictions of radiative and nonradiative decay constants indicate that the vibrations of the molecular rotors impact nonradiative decay rates and, consequently, the fluorescence quantum yields.
The development of new structures with emerging functionalities has been one of the goals in nanoarchitectonics. It has been established that this concept includes the bottom-up organization of atoms and molecules and, with this in mind, the present chapter contains selected contributions focused on the importance of intramolecular dynamics in optical properties, dielectric response, macroscopic motion, and sorption behavior of crystals. It is considered that the understanding of molecular motion can be associated with the output of crystalline materials to envision new smart solid state materials for a wide variety of applications.
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