Donor-Acceptor Conjugated Macrocycles with Polyradical Character and Global Aromaticity

Abstract

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.

Non-Aufbau orbital ordering and spin density modulation in high-spin donor–acceptor conjugated polymers

“…However, there is no polyradical character observed in the studied polymers (Table S3, ESI †), which has also been reported for other BBT-based materials. 8,78 This is probably due to the fact that the unpaired electrons which are deeper in energy do not contribute to the open-shell character, limiting the open-shell character to diradicals (see Table S3, ESI †). A similar phenomenon in orbital orientation is observed for the Si substituted polymer as well (Fig.…”

“…OSCs with two (diradicals) or more number of unpaired electrons (polyradicals) have unique optical, electronic, spin-transport, and magnetic properties, making them suitable for potential application in organic photovoltaics, solar cells, charge-storage devices, organic spintronics, and magnetic materials. [1][2][3][4][5][6][7][8][9] Research endeavors are mostly directed towards finding novel organic high-spin state molecules [10][11][12][13][14][15][16][17] to understand the core mechanism of magnetism which may facilitate the development of new materials with improved optoelectronic and magnetic properties. 5,18 However, the mechanism to control the spin distribution and alignment of unpaired electrons in molecular orbitals (MOs) is not well studied.…”

Acene-Linked Zethrenes and Bisphenalenyls: A DFT Search for Organic Tetraradicals

“…To check the possibility of stabilization of the tetraradicaloid states in the such way constructed hydrocarbon systems and expecting to reveal compounds with four unpaired electrons, we have performed a computational modeling of zethrene 1 and bisphenalenyl 2 derivatives comprising from five to nine benzene rings ( n = 1–5) in the linker group (Chart ). A peculiar feature of the considered systems as compared with the previously studied tetraradicaloids − is the presence of two types of paramagnetic centers providing for the possibility of a wide variation of magnetic properties.…”

Theoretical exploration of molecular packing and the charge transfer mechanism of organic solar cells based on PM6:Y6

“…Ab initio molecular dynamics (AIMD) can be used to accurately calculate electronic structures, and atomic and molecular interactions, and then simulate the trajectory of molecules over time to obtain the evolution of molecular morphology in the active layer. 34,35 It is important to analyze molecular conformation, stacking and charge transfer processes. Among them, the tight-binding quantum mechanical approach Geometry Frequency Noncovalent-eXtended TB (GFN-xTB) focuses on molecular structural properties and performs robustly, and is widely applicable.…”