Linear and nonlinear optical properties of a quadrupolar carbo-benzene and its benzenic parent: The carbo-merization effect

Herein, the optical properties of thiophene-functionalized quadrupolar carbo-benzenes and a benzenic parent, generic structure Th–CC–[core]–CC–Th, Th = R2C4HS, are comparatively investigated. Beyond previously unknown dioctylthienylethynylbenzene (core p-C6H4, R nOct), two bis-dialkylthienylethynyl-carbo-benzenes C18Ph4, nOct, nBu) envisaged for unique "carbo-aromatic" character C18 macrocycle. The three targets were synthesized from corresponding ethynylthiophenes in 47, 20 10% yield, respectively, then characterized by classical methods such as NMR spectroscopy, X-ray crystallography one carbo-benzenes. Regarding linear nonlinear properties, our results show that carbo-merization induces significant shift to lower energies one-photon electronic excitations accompanied an 8-fold increase molar extinction coefficient compared parent molecule. Intriguingly, these lead broad band photoluminescence comprising decay transitions type S1 → S0 but also S2 S0. This phenomenon emission higher excited states, which is contrary Kasha's rule, assigned - or revealed reduction internal conversion efficiency between S1. Two-photon induced enhanced, two-photon absorption cross-section (σ2PA) being average five times larger than their benzene wavelength range 650–950 nm, with maximum σ2PA 1430 GM (1 10−50 cm4 s/photon). moderate nonlinearity, this comparative study provides quantitative insights about way insertion π-conjugated macrocycle chromophoric functions (here thiophene rings) can tune organic molecules. discussed regard recent reports on chromophores based other types macrocyclic cores.