Construction of Nanosize Magnetic Bar by Assembling of Organic Molecules and Control of Their Arrangement

近年来，人们对分子磁性的研究产生了浓厚的兴趣。虽然这些铁磁有序已被偶然发现，分子间交换耦合途径的设计方法尚未建立。迄今为止报道的有机铁磁体具有合适的排列以满足McConnell提出的模型和/或轨道正交性;然而，晶体中分子排列的控制不一定对应于可预测的策略。虽然分子化学处理的是单个自由基单元的设计和合成，但它们组装成固体是由超分子化学的概念决定的。我们的最终目标是设计一种自由基分子，其组装结构可以由其化学结构来预测。我们已经发现了在硝酰基硝酰基中磁性自组装的形成（4，4，5，5-四甲基-4，5-二氢-1H-咪唑啉-1-氧基-3-氧化物）衍生物，其携带具有NH位点的杂环，例如咪唑-2-基、苯并咪唑-2-基、萘[2，3-d]咪唑-2-基和氮杂吲哚-2-基环。在这些化合物中，苯并咪唑衍生物形成了一个堆叠的柱状组装诱导的分子内和分子间的氢键之间的NH网站和两个硝酰基O原子。该组装体表现出一维铁磁链行为（J=约13 &lt;$16 cm^<-1>），通过单占据分子轨道（SOMO）之间的空间紧密接触可以合理化该行为.为了增强分子系统中的磁相互作用，SOMO之间的多点紧密接触是有利的，因为分子间的磁相互作用是由属于相邻分子的邻近原子的自旋密度乘积之和描述的.我们还对2，2-二苯基-1，2-二氢喹啉-1-氧自由基进行了研究，发现了一些有趣的磁性特征。

Recently, there has been substantial interest in the study of molecular-based magnetism. Whereas these ferromagnetic orderings have been discovered fortuitously, methodology for designing intermolecular exchange coupling pathways has not been established yet. Organic ferromagnets so far reported have suitable arrangements to fulfill the model proposed by McConnell and/or orbital orthogonality ; however, the control of molecular arrangement in the crystal does not necessarily correspond to predictable strategy. Whereas molecular chemistry deals with the design and the synthesis of individual radical units, their assembly into a solid is governed by concepts of supramolecular chemistry. Our ultimate objective is to design radical molecules whose assembled structure can be predicted from their chemical structure.We have already found the formation of magnetic self-assemblies in nitronyl nitroxyl (4,4,5,5-tetramethyl-4,5-dihydro-1 H-imidazoline-1 oxyl-3-oxide) derivatives carrying heterocycles with the NH site, such as the imidazol-2-yl, benzimidazol-2-yl, naphth[2,3-d]imidazol-2-yl and azaindol-2-yl rings. Among these compounds, the benzimidazole derivatives formed a piled columnar assembly induced by intra- and intermolecular hydrogen bondings between an NH site and two nitroxyl O atoms. The assembly exhibited a 1D ferromagnetic chain behavior (J=ca.13〜16 cm^<-1>) that could be rationalized by through space close contact between the singly occupied molecular orbitals (SOMOs).To enhance the magnetic interaction in molecular systems, it is favorable to design multipoint close contacts between the SOMOs, because intermolecular magnetic interaction is described by the sum of the spin-density product of nearby atoms belonging to neighboring molecules. We also focused on 2,2-diphenyl-1,2-dihydroquinoline-1-oxyl and found several interesting magnetic characteristics in chemically modified derivatives.