Synthesis of new [6]helicene derivatives for OLED applications. Experimental photophysical and chiroptical properties and theoretical investigation

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Six-membered helicenes with specific functionalities were synthesized in good overall yields (40 %-73 %) through a concise photochemical method, allowing for their comprehensive characterization. The racemic mixtures were effectively resolved into their P- and M-enantiomers with high optical purity (97.56 %-100 % ee) by using chiral HPLC. This separation showcased remarkable optical activity, revealing substantial optical rotations (e.g., +2500–3000 for the (P)-enantiomer at λ = 589 nm) and notable electronic circular dichroism (ECD) signals. The organic helical species showed a strong absorption in the UV region and exhibited a red shifted emission, resulting in a quantum yield of 0.12–0.21. Moreover, they demonstrated irreversible one-electron oxidation and reduction processes, and their HOMO and LUMO energy levels were estimated via electrochemical methods. Utilizing DFT and TD–DFT computational approaches, we accurately predicted the electronic absorption and ECD spectra, as well as the frontier molecular orbitals (FMOs), aligning closely with experimental observations. Furthermore, in-depth analyses of absorption and ECD spectra, molecular electrostatic potential (MEP), and reduced density gradient (RDG) through quantum chemical calculations offered insights into the fundamental characteristics of these materials. The collective properties strongly indicate the potential application of these helicenes in electroluminescent and OLED devices, underscoring their promise as candidates in optoelectronic applications.