(161aw) Designing Donor-Acceptor Conjugated Macrocycles with Polyradical Character and Global (anti)Aromaticity

Organic semiconductors (OSCs) have great potential applications in the new advanced (opto)electronic technologies. The development of novel molecules with unique architectures are of great importance in designing next generation (opto)electronic devices. π-conjugated macromolecules have rigid porous structures with unique, unusual geometric, and electronic properties. Although conjugated macromolecules have numerous applications in electronic devices, novel molecular architectures with intriguing electronic properties are scarce in the literature. Here, we have designed new donor-acceptor (D-A) macromolecules along with their π-spacer derivatives and analyzed electronic properties with density functional theory (DFT). The curved molecules with n = 8 and 16 repeat units shows similar singlet-triplet energy gap, have closed-shell configuration with no diradical character (y = 0), and shows global non-aromatic character, which is supported by NICS(0), AICD, and 2D-ICSS analysis. However, the derivatives with π-spacer (n = 8-π) develops near pure open-shell character (y ≈ 1), increased singlet-triplet gaps (ΔE_ST), globally antiaromatic in the singlet ground-state according to Huckel's rule, and globally aromatic in the lowest triplet state following Baird's rule, and have a very high polyradical character in the ground-state, which is not reported for D-A type macromolecules. The calculated absorption spectra with time-dependent DFT (TDDFT) indicates light absorption in the near-infrared (NIR) region broadening to 2500 nm. Also, the macrocycles display size-dependent absorption maxima when the number of repeat units increased from n = 8 to 16. Furthermore, due to the development of open-shell character in the π-spacer derivatives, a significant red-shift in the absorbance wavelength is observed.