First-principles theoretical modelling of one-handed helical ladder polymers circularly polarized luminescence

Abstract

The idea of helical chirality bridges the gap between the stereogenic asymmetry at local scale and the intrinsic nonsuperimposability in larger secondary structures (DNA, RNA, α-helix protein, etc.). Novel synthetic breakthroughs allowed the ascent of a brand-new chiral materials subclass grounded on defect-free single-handed helical ladder polymers reducing the conceptual barrier between the small artificial helical foldamers and the helical biomacromolecules. Beyond their extraordinary chemical-physical properties, the interference of circularly polarized radiation with optically-pure one-handed helical ladder polymers paved the way for pronounced circularly polarized luminescence events. This work, through a systematic theoretical investigation, tackled the CPL spectral profiles of a multitude of enantiomeric ladder-type polymers with diversified helical arrangements and topological cavities. The computational sequence integrated a preliminary ground state treatment of chiral monomeric units with excited molecular dynamics of oligo/polymeric systems to understand how key geometrical parameters of ladderization precursors vary during the photoexcitation along serially bigger chemical architectures. The consolidation of APFD and O3LYP functionals performances through the rigorous accumulation of chiroptical descriptors (emission energies, rotatational strengths, electric/magnetic transition dipole moments and their angle) granted us to democratize how the chiral dimensionality orients the CPL spectra of one-handed helical ladder polymers in terms of peak position, band shape, chiral sign and signal magnitude.