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Intriguing diaza effects on magnetic coupling characteristics in diaza‐benzo[ k ]tetraphene‐bridged nitroxide diradicals
Author(s) -
Zhang Fengying,
Luo Qi,
Song Xiufang,
Song Xinyu,
Bu Yuxiang
Publication year - 2018
Publication title -
international journal of quantum chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.484
H-Index - 105
eISSN - 1097-461X
pISSN - 0020-7608
DOI - 10.1002/qua.25693
Subject(s) - homo/lumo , antiferromagnetism , diradical , chemistry , ferromagnetism , molecular orbital , inductive coupling , crystallography , coupling (piping) , aromaticity , spin (aerodynamics) , condensed matter physics , molecule , physics , materials science , atomic physics , excited state , singlet state , quantum mechanics , metallurgy , organic chemistry , thermodynamics
We theoretically design four diaza‐benzo[ k ]tetraphene‐based diradical isomers ( 1, 2, 3 , and 4 ) with two nitroxide (NO) radical groups as spin sources. The calculations at the B3LYP/6‐311++G(d,p) level suggest that the diaza doping can induce the aromaticity changes and the CC bond rearrangements and, thus, remarkably affect their magnetic coupling magnitudes and even characteristics (ferromagnetic vs. antiferromagnetic). More interestingly, different diaza‐doping positions can lead to distinctly different effects, and further dielectron‐oxidation can also noticeably change the magnetic coupling magnitudes from −919.9 cm −1 ( 1 ) to −158.3 cm −1 ( 1 2+ ) or from −105.1 cm −1 ( 3 ) to −918.9 cm −1 ( 3 2+ ) or induce the magnetic conversions from nonmagnetism ( 2 ) to antiferromagnetism ( 2 2+ , −140.1 cm −1 ) or from ferromagnetism ( 4 , 108.9 cm −1 ) to antiferromagnetism ( 4 2+ , −462.5 cm −1 ). Good matching of two singly occupied molecular orbitals (SOMOs) of the NO groups with the highest occupied molecular orbital (HOMO) of the coupler (for 1 ), or with the lowest unoccupied molecular orbital (LUMO) of the coupler (for 3 2+ and 4 2+ ), available Kekulé structure (for 2 ), aromaticity variations are responsible to strong magnetic couplings. Besides, the HOMO‐LUMO energy gaps of the couplers also considerably affect the magnetic couplings. This work may open a new route for the rational design of the diaza‐benzo[ k ]tetraphene‐based magnetic molecular modulators or switches.