Perylene-Embedded Helical Nanographenes with Emission up to 1010 nm: Synthesis, Structures, and Chiroptical Properties.

Abstract

Near-infrared (NIR) circularly polarized absorbing or emitting materials offer distinct advantages over their visible-light counterparts and have attracted considerable interest across various fields. Materials exhibiting NIR chiroptical properties with high fluorescence quantum yields (Φ_F) are particularly rare. In this study, we report the synthesis of a series of helical nanographenes (1, 2, 3, and 4), where perylene is fused with one to four hexa-peri-hexabenzocoronene (sub) units by a strategy involving Diels-Alder cycloaddition followed by a Scholl reaction. X-ray crystallographic analysis confirmed their structures, revealing helicene moieties integrated into a highly contorted framework. Benefiting from a similar distribution pattern of frontier molecular orbitals to perylene and extended π-conjugation, compounds 1-4 demonstrate respectable Φ_F values of 31.9 %, 15.0 %, 13.7 %, and 6.5 %, respectively, with emission maxima reaching up to 1010 nm. Their enantiopure forms, isolated by preparative chiral HPLC, exhibit distinct circular dichroism signals and circularly polarized luminescence across a broad spectral range, extending from the ultraviolet to the NIR.