邻、间、对-二甲氧基亚甲基苯及衍生物双自由基体系的自旋耦 合规律

采用量子化学abinitio法对具有甲氧基的碳、氧双自由基邻、间、对二甲氧基亚甲基苯及衍生物体系基态自旋耦合规律进行研究,得到非平面共轭体系中自由基之间磁性耦合的拓朴规则:共轭体系中,两个自由基之间以偶数个碳原子耦合,则有效交换积分J~i~j<0,体系具有低自旋基态;两个自由基之间以奇数个碳原子耦合,则J~i~j>0,体系具有高自旋基态。自由基性质对自旋耦合的影响较大,正离子自由基间磁性耦合能力较强,这些结论为有机磁性材料的分子设计与实验合成提供了理论依据。

Spin coupling rules for the biradicals of o-, m-, p- bimethoxymethanobenzene and its derivatives

Spin coupling rules for the ground state of the carbon or nitrogen biradicals of o-, m-, p-bimethoxymethanobenzene and its derivatives containing the carbon, nitrogen biradicals have been studied quantum chemical ab initio methods. It is proved that there are topological rules for the magnetic couplings between the radicals of nonplane conjugated systems: In conjugated system, the effective exchange integrals of radical sites through the even number of carbons with a π-electron network are negative in sign, which means the low spin state corresponds to a stable ground state, while those through odd carbon atoms are positive in sign, (i.e., the high spin state corresponds to a stable ground state). The properties of radical have obvious influence on the spin coupling. Stronger ferromagnetic coupling occurs between positive ion radicals, which provides theoretical guide for molecular design and experimental synthesis of organic magnetic materials.