Thiophene/selenophene-based windmill-shaped triple [6]helicenes

Abstract

The construction of multiple helicenes, one of important branches to curved polyaromatic hydrocarbons (PAHs) is a fundamental goal in both helicence chemistry and supramolecular chemistry. Here, we demonstrate the facile...

Polycyclic aromatic hydrocarbons containing antiaromatic chalcogenopyrano[3,2-b]-chalcogenopyrans

“…Therefore, the larger and more polarizable orbitals of Se may enhance intermolecular interactions and facilitate charge transport among molecules. [6][7][8][9] Despite the great advantages of the Se element, much fewer research studies have focused on Se-fused PAHs, 10,11 which can be attributed to the lack of commercially available starting materials, reagents, and key intermediates, as well as the limited synthetic methodologies. Consequently, functionalization of Se-fused PAHs is still synthetically challenging.…”

Construction and Phosphorescence Behavior of S/Se-Heteroaromatics/Phenanthrene-Fused Hetero[9]helicenes

“…The typical carbon−sulfur helicenes, bearing all sulfur atoms along the outer edge of the molecular skeletons, have been systematically studied by Rajca. 5−7 Wang and co-workers have developed this chemistry, and exhibited double thiahelicenes, 8,9 triple thiahelicenes, 10 and thiophene/selenophene-based helicenes. 10,11a As a special homologue of thiahelicenes, thia [9]helicene has received little attention.…”

“…They have been widely applied in multiple fields, such as asymmetric catalysis, molecular recognition, and circularly polarized luminescence (CPL) materials. − Thia-helicenes are a subclass of the helicene family, with at least one benzene unit replaced by thiophene, changing distinct electronic properties and chiroptical properties from their parent molecules. The typical carbon–sulfur helicenes, bearing all sulfur atoms along the outer edge of the molecular skeletons, have been systematically studied by Rajca. − Wang and co-workers have developed this chemistry, and exhibited double thiahelicenes, , triple thiahelicenes, and thiophene/selenophene-based helicenes. , …”

“…As a special homologue of thiahelicenes, thia[9]­helicene has received little attention. On the one hand, the molecular skeletons are composed of all thiophene units or fused thiophene/benzene units (Figure ), − and their synthesis was highly challenging. ,, On the other hand, the limited optoelectric properties of CPL , have been reported to the derivatives of thia[9]­helicenes. With the change of heteroatom from S to Se in the molecular skeletons, hetero[7]­helicenes and S-shaped double heterohelicenes exhibited the increase of molecular π-conjugation and the decrease of fluorescence emission in our previous work. , To the best of our knowledge, no study on the phosphorescence behaviors of thiahelicenes has been reported to date.…”

“…All three hetero[9]­helicenes exhibit weak fluorescence emission with a minor bathochromic shift from 434 to 442 and 444 nm, respectively. Meanwhile, their emission intensity decreases (Table ), implying the involvement of heavy atom effect, , which can promote the decay of intersystem crossing (ISC) and result in phosphorescence intensity more efficiently. The heavy atom effect is significantly observed for their emission behaviors in 2-methyl tetrahydrofuran (2-MTHF) at 77 K. With the heteroatom changing from S to Se, phosphorescence emissions increased and showed a bathochromic shift from 514/555 nm to 524/564 and 526/566 nm (Figure S38), respectively, consistent with the increase of both heavy atom effect and molecular π-conjugation.…”