Synthesis, Structure and Photophysical Properties of Pyrene–based [5]Helicenes: an Experimental and Theoretical Study

Abstract

International audiencePyrene-cored [5]helicenes were prepared by a facile, efficient Wittig reaction and an intramolecular photocyclization reaction utilising 2,7-di-tert-butylpyrene-4-carbaldehyde and naphthalene/pyrene-based phosphorus ylides. Optical properties based on UV À vis absorption and fluorescence spectra were investigated. X-ray crystallography revealed that the pyrene-based [5]helicenes exhibited strong face-to-face p À p interactions and edge-to-face p À p interactions. HOMO and LUMO energies and molecular orbitals were also studied by density functional theory (DFT) calculations. This study has revealed that the torsion angle of the helical structure plays a role in determining the p À p interactions and the frontier molecular orbital energy levels. Thus, pyrene-based helicenes need to be considered when one designs new highly efficient organic light-emitting diodes and organic semiconductor materials

Exploiting a multicomponent domino reaction strategy for the tailoring of versatile environmentally sensitive fluorophore-based nicotinonitriles incorporating pyrene and fluorene moieties

“…These observations encouraged us to explore the catalytic prociency of AcOH in other solvents such as MeOH, 2-propanol, DMF, and dioxane, but no improvement in the yield of the target product 5a was observed ( Table 1, entries 12-15). Furthermore, we observe that the yields of 5a were distinctly affected by the amount of AcOH (Table 1, entries [16][17][18][19][20][21]. It was found that when the amount of acetic acid was increased, the desired product 5a was isolated in a signicantly higher yield.…”

“…The extremely uorescence properties of pyrene mean it is the rst choice uorophore in both fundamental and applied photochemical and photophysical research. [15][16][17][18][19][20][21] As its monomer emission typically appears at 370-420 nm and it is a distinguishing violet color, the pyrene moiety is considered to be one of the most benecial assembly moieties for the construction of uorogenic chemosensors that are frequently used for necessary chemical applications. 22 Pyrene derivatives have been extensively used in many applications as uorescent probes 23 and uorescent sensors.…”

Synthesis, Structure and Applications of Cationic Phosphonites

“…This was calculated to steadily decrease, on increasing n. [138] Incorporation of thiophene and furan sub-units has also been shown to decrease the HOMO-LUMO gap, so long as the thiophenes [139] alternate with benzene rings to maintain effective π-conjugation. Other methods include annulating additional rings or helices onto the structure, therefore increasing the area of electron delocalization, [140,141] or incorporating push-pull elements by introduction of electron donor/acceptor substituents. [142] Finally, incorporation of an anti-aromatic subunit to the helicene also has a dramatic effect on the position of the frontier orbitals.…”

“…[144,145] Some examples of helicenes with high fluorescence quantum yields are shown in Figure 19B. A) HOMO-LUMO gaps for the helicenes 108a, [142] 109, [146] 113, [139] 114, [141] 115, [140] 116, [142] 117. [143] B) examples of helicene derivatives with high fluorescence quantum yields 118 [145] and 119.…”

“…Figure19. A) HOMO-LUMO gaps for the helicenes 108a,[142] 109,[146] 113,[139] 114,[141] 115,[140] 116,[142] 117 [143]. …”