Thermodynamically versus Kinetically Controlled Self-Assembly of a Naphthalenediimide–Thiophene Derivative: From Crystalline, Fluorescent, n-Type Semiconducting 1D Needles to Nanofibers

Abstract

The control over aggregation pathways is a key requirement for present and future technologies, as it can provide access to a variety of sophisticated structures with unique functional properties. In this work, we demonstrate an unprecedented control over the supramolecular self-assembly of a semiconductive material, based on a naphthalenediimide core functionalized with phenyl–thiophene moieties at the imide termini, by trapping the molecules into different arrangements depending on the crystallization conditions. The control of the solvent evaporation rate enables the growth of highly elaborated hierarchical self-assembled structures: either in an energy-minimum thermodynamic state when the solvent is slowly evaporated forming needle-shaped crystals (polymorph α) or in a local energy-minimum state when the solvent is rapidly evaporated leading to the formation of nanofibers (polymorph β). The exceptional persistence of the kinetically trapped β form allowed the study and comparison of its characteristics with that of the stable α form, revealing the importance of molecular aggregation geometry in functional properties. Intriguingly, we found that compared to the thermodynamically stable α phase, characterized by a J-type aggregation, the β phase exhibits (i) an unusual strong blue shift of the emission from the charge-transfer state responsible for the solid-state luminescent enhancement, (ii) a higher work function with a “rigid shift” of the electronic levels, as shown by Kelvin probe force microscopy and cyclic voltammetry measurements, and (iii) a superior field-effect transistor mobility in agreement with an H-type aggregation as indicated by X-ray analysis and theoretical calculations.

Nanostructuring Iridium Complexes into Crystalline Phosphorescent Nanoparticles: Structural Characterization, Photophysics, and Biological Applications

“…In the other two complexes, PPY and MDQ, the nanoparticles show a profile completely different from that of the pristine crystalline powders, thus evidencing the formation of novel polymorphic forms. It is noteworthy that these complexes show a propensity to aggregate in different crystal assemblies; these aspects will be addressed in detail in a further study because the search of new functionalities by polymorph exploitation of known compounds is an emerging topic with high technological relevance. − The average size of the crystallites in the nanoparticle calculated by using the Scherrer formula ( Dv = K λ/β cos θ) at the most intense peak was 51 nm for FI-Nps, 40 nm for PPY-Nps, and 35 nm for MDQ-Nps. To get more direct clues about the size and location of the crystalline zone in the nanoparticle, TEM measurements were performed (Figures S7–S9).…”

Supramolecular Assembly of Thiophene‐Based Oligomers into Nanostructured Fluorescent Conductive and Chiral Microfibers

“…Conformational polymorphism between amorphous and crystalline phase is at the origin of the fabrication of a bicolored pixel structure LED based on a single luminescent oligothiophene . Polymorphic needle‐shaped crystals and crystalline nanofibers with very different functional properties and reproducibly grown on different substrates have also recently been reported . We have described the first example of polymorphic microfibers generated from a ‘sulphur overrich’ octamer, namely 3,3′,3′′′,3′′′′′,3′′′′′′′′′,4′′,4′′′′,4′′′′′′‐octakis(hexylsulphanyl), 1 .…”

Push–pull thiophene-based small molecules with donor and acceptor units of varying strength for photovoltaic application: beyond P3HT and PCBM

“…from hours to minutes, and (iii) work in environment-friendly conditions using water as co-solvent. [44][45][46] In the final step, all heptamers, which differ for the peripheral A units or for the presence of an extra sulfur atom in the side chains of the D group, were obtained in yield ranging from 60 to 70% after 20 min of MW irradiation. The presence of hexyl side chains on the four thiophene rings guarantees good solubility of all molecules in DCM, toluene, and THF, particularly for T7Bz-Dp 2 , which has additional hexyl side chains installed on the Dp units.…”