Donor-Acceptor Conjugated Macrocycles with Polyradical Character and Global Aromaticity

• Main Authors: Md Abdus Sabuj, Md Masrul Huda, Neeraj Rai
• Format: Article
• Language: English
• Published: Elsevier 2020-11-01
• Series: iScience
• Subjects: Chemistry; Supramolecular Chemistry; Computational Chemistry; Macromolecules
• Online Access: http://www.sciencedirect.com/science/article/pii/S2589004220308671

Summary: Polyradical character and global aromaticity are fundamental concepts that govern the rational design of cyclic conjugated macromolecules for optoelectronic applications. Here, we report donor-acceptor (D−A) conjugated macromolecules with and without π-spacer derivatives to tune the antiferromagnetic couplings between the unpaired electrons. The macromolecules without π-spacer have a closed-shell electronic configuration and show global nonaromatic character in the singlet and lowest triplet states. However, the derivatives with π-spacer develop a nearly pure open-shell diradical and a very high polyradical character, not reported for D−A type macromolecules. Furthermore, the π-spacer derivatives display global nonaromaticity in the singlet ground state, but global aromaticity in the lowest triplet state, according to Baird's rule. The absorption spectra of the open-shell macromolecules calculated with time-dependent density functional theory indicate intensive light absorption in the near-infrared region and broadening to 2,500 nm, making these materials suitable for numerous optoelectronic applications.