Theoretical Simulation on Regulating the Magnetic Coupling Properties of Diradical Artificial Bases

Abstract

In this work, we computationally designed a series of diradical molecules with obvious magnetic coupling properties based on newly synthesized artificial bases, 6-amino-3-(1′-β-d-2′-deoxyribofuranosyl)-5-nitro-1H-pyridin-2-one (Z), 2-amino-8-(1′-β-d-2′-deoxyribofuranosyl)-imidazo-[1,2a]-1,3,5-triazin-[8H]-4-one (P), 6-amino-9[(1′-β-d-2′-deoxyribofuranosyl)-4-hydroxy-5-(hydroxymethyl)-oxolan-2-yl]-1H-purin-2-one (B), and found two methods (base pairing and nitro group rotation) of regulating the magnetic magnitude, making them become magnetic switches with promising prospects. On one hand, the modified diradical artificial base P3 possesses an excellent magnetic exchange coupling constant due to its spin density concentration on a unique spin polarization path. Because of the serious mismatch between the singly occupied molecular orbital (SOMO) and the lowest unoccupied molecular orbital (LUMO) of Z-P3 base pairing, the magnetic coupling property of the Z-P3 base pair disappears, which indicates that the base pairing can be used as an effective means to regulate the molecular magnetic coupling properties. On the other hand, the investigation shows that the rotation of the nitro group on Z has an influence on the energy gaps between the closed-shell (CS) singlet and triplet (T) states of the base pairs formed by Z-analogues and thereby the expression of magnetic coupling properties. This work can help to develop the modification strategy of the diradical base and provide theoretical guidance for the design and synthesis of magnetic coupling materials with controllable magnetic coupling properties.

Antiaromatic Molecules as Magnetic Couplers: A Computational Quest

“…A significant number of recent research studies ,,,− ,− have been dedicated to finding new strategies for designing new organic diradicals with unique magnetic properties, especially in chemical processes that change or modify the magnetic properties of systems when transitions from ferromagnetic (FM) to antiferromagnetic (AFM) coupling (or vice versa) or when significant changes in the magnitude of the magnetic coupling constant J are observed. For example, Malik and Bu have shown that intramolecular proton transfer is able to modulate the magnetic spin-coupling interaction in photochromic azobenzene derivatives with ortho -site hydroxyl as a modulator, where some molecules can undergo magnetic conversion between antiferromagnetic and ferromagnetic coupling due to proton-transfer processes exhibiting large changes in J values.…”

“…The quest for designing and understanding novel organic compounds that can be characterized as open-shell singlet or triplet electronic spin states exhibiting unique properties that can be applied for various practical applications (spintronics, quantum information science, organic electronics) has long been of considerable interest to researchers. − Some of the most important characteristics describing organic compounds include their stability, optical and magnetic properties, and degree of reactivity. , Thus, many theoretical and computational models for predicting such properties have been developed over many years for the purpose of accurately describing the electronic structures of such systems. In this context, some of the most useful concepts for understanding organic systems are aromaticity, the degree of diradical character, and magnetic properties. − To this end, various descriptors for evaluating the degree of aromaticity have been developed, − as well as various measures of diradica...…”

Redox-Regulated Magnetic Conversions between Ferro- and Antiferromagnetism in Organic Nitroxide Diradicals

“…For a diradical, when two unpaired electrons occupy nearly degenerate spatial orbitals, a parallel-spin orientation gives rise to a triplet ground state (ferromagnetic coupling) while an antiparallel-spin orientation leads to a singlet ground state (antiferromagnetic coupling) [7]. A common type of organic diradical is composed of two single radical groups as the spin sources bridging through a coupler, which has been extensively investigated experimentally and theoretically [8][9][10][11][12][13][14][15][16][17][18]. The magnetic coupling constant J is largely dependent on the interaction between two spin sources.…”