Near-Infrared Emissive Molecular Carbons based on Quadruple [n]Helicenes.

Abstract

We present a molecular design strategy that combines structural multiplicity and π-extension on a quaterrylene diimide scaffold to construct efficient near-infrared (NIR) circularly polarized luminescence (CPL) emitters. Through a carefully controlled synthesis involving sequential regioselective Suzuki coupling followed by Sholl-type oxidative cyclization, we successfully obtained two novel quadruple [n]helicenes (QnH). Comprehensive experimental characterization and theoretical calculations demonstrated their distinct configurational preferences: Q5H exclusively adopted the meso (P,P,M,M) configuration, while Q6H produced only the (P,P,P,P)/(M,M,M,M) enantiomeric pair. Single-crystal X-ray diffraction unambiguously confirmed the unique "four-bladed propeller" structure of (P,P,M,M)-Q5H. Both compounds demonstrated intense NIR fluorescence emission with photoluminescence quantum yields (ΦPL) of 47% for Q5H and 37% for Q6H. The chiral (P,P,P,P)/(M,M,M,M)-Q6H enantiomers showed exceptional chiroptical properties, including intense Cotton effects reached 719 M-1 cm-1 at 410 nm, a high absorption dissymmetry factor |gabs| of 0.035, and prominent CPL activity across 600 to 800 nm with a CPL brightness (BCPL) of 96 M-1 cm-1.