Redox-Modulated Magnetic Transformations between Ferro- and Antiferromagnetism in Organic Systems: Rational Design of Magnetic Organic Molecular Switches

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• 作者：Fengying Zhang ; Xinyu Song ; Yuxiang Bu
• 刊名：Journal of Physical Chemistry C
• 出版年：2015
• 出版时间：December 17, 2015
• 年：2015
• 卷：119
• 期：50
• 页码：27930-27937
• 全文大小：415K
• ISSN：1932-7455

文摘

Organic molecules with switchable magnetic properties have extensively technological applications due to the fact that magnetic conversion can be realized through diverse methods. In particular, the redox-induced magnetic reversal is easy to accomplish and exhibits promising application in the field of magnetic materials, and thus it is an imperative task to find magnetism-switchable systems. Herein, we computationally design two couples of nitroxy鈥損yrazinyl鈥搉itroxy diradicals in which two nitroxy radical groups are connected to a redox-active pyrazinyl coupler in the para or meta modes. We find that the magnetic conversion can occur from ferromagnetic to antiferromagnetic exchange coupling or vice versa by means of the redox method in these designed magnetic organic molecules, and their magnetic exchange coupling constants are considerably large no matter for ferromagnetic or antiferromagnetic couplings, as evidenced at both the B3LYP and M06-2X levels of theory. Analyses indicate that redox-induced structural change of the coupler leads to conversion of its aromaticity and considerable spin delocalization from the 蟺-conjugated structure and spin polarization from non-Kekule structure, which thus determine the spin coupling between two spin centers in the magnetic molecules. In addition, the spin alternation rule, singly occupied molecular orbital (SOMO) effect, and SOMO鈥揝OMO energy splitting of triplet state are utilized to analyze the diradical characters of the molecules, suggesting effective tools for predicting molecular ground states (ferromagnetic, antiferromagnetic, or nonmagnetic). This work provides helpful information for the rational design of promising organic magnetic switches.