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.