From achiral ligands to chiral coordination polymers: Spontaneous resolution, weak ferromagnetism, and topological ferrimagnetism
From achiral ligands to chiral coordination polymers: Spontaneous resolution, weak ferromagnetism, and topological ferrimagnetism
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DOI：
10.1021/ja039104a
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发表时间：
2004-02-11
影响因子：
15
通讯作者：
Yan, CH
中科院分区：
文献类型：
--
作者：
Gao, EQ;Yue, YF;Yan, CH
使用非手性二嗪配体轴承两个双齿吡啶亚氨基作为来源的构象手性，五叠氮桥配位聚合物的制备和表征的晶体学和磁性。分子单元的手性是由二嗪配体以扭曲的手性构象配位引起的。使用L-1（1，4-双（2-吡啶基）-1-氨基-2，3-二氮杂-1，3-丁二烯）和L-2（1，4-双（2-吡啶基）-1，4-二氨基-2，3-二氮杂-1，3-丁二烯）诱导自发拆分，得到手性化合物[Mn-3（L-1）（2）（N-3）（6）]（n）（1）和[Mn-2（L-2）（2）（N-3）（3）]（n）（ClO 4）（n）（.）nH（2）O（2），其中三角形（1）或双螺旋（2）手性单元通过单个端对端（EE）叠氮桥连接成纯手性一维（1D）链。链通过氢键以同手性方式堆叠以产生手性晶体。当使用L-3（2，5-双（2-吡啶基）-3，4-二氮杂-2，4-己二烯）时，发生部分自发拆分，其中双核手性单元通过单个EE叠氮桥互连成鱼鳞状纯手性二维（2D）层。以异手性或同手性方式堆叠所述层以同时产生外消旋化合物[Mn-2（L-3）（N-3）（4）]（n）（3a）和聚集体[Mn-2（L-3）（N-3）（4）]（n）（.）nMeOH（3b）。另一方面，没有氨基和甲基取代基的配体（L-4，1，4-双（2-吡啶基）-2，3-二氮杂-1，3-丁二烯）不诱导自发拆分。得到的化合物[Mn-2（L）（N-3）（4）]（n）（4）由中心对称的二维层组成，具有交替的单二嗪、单EE叠氮基和双末端（EO）叠氮基桥，其中手性被中心对称的双EO桥破坏。这些化合物表现出非常不同的磁性行为。特别是，1表现为由具有独特的“融合三角形”拓扑结构的同质亚铁磁链构成的超磁体，2表现为具有交替反铁磁相互作用的一维反铁磁体，3a和3b表现为具有不同临界温度的自旋倾斜弱铁磁体，4也表现为自旋倾斜弱铁磁体，但表现出两步磁转变。
Using the achiral diazine ligands bearing two bidentate pyridylimino groups as sources of conformational chirality, five azido-bridged coordination polymers are prepared and characterized crystallographically and magnetically. The chirality of the molecular units is induced by the coordination of the diazine ligands in a twisted chiral conformation. The use of L-1 (1,4-bis(2-pyridyl)-1-amino-2,3-diaza-1,3-butadiene) and L-2 (1,4-bis(2-pyridyl)-1,4-diamino-2,3-diaza-1,3-butadiene) induces spontaneous resolution, yielding conglomerates of chiral compounds [Mn-3(L-1)(2)(N-3)(6)](n) (1) and [Mn-2(L-2)(2)(N-3)(3)](n)(ClO4)(n)(.)nH(2)O (2), respectively, where triangular (1) or double helical (2) chiral units are connected into homochiral one-dimensional (1D) chains via single end-to-end (EE) azido bridges. The chains are stacked via hydrogen bonds in a homochiral fashion to yield chiral crystals. When L-3 (2,5-bis(2-pyridyl)-3,4-diaza-2,4-hexadiene) is employed, a partial spontaneous resolution occurs, where binuclear chiral units are interlinked into fishscale-like homochiral two-dimensional (2D) layers via single EE azido bridges. The layers are stacked in a heterochiral or homochiral fashion to yield simultaneously a racemic compound, [Mn-2(L-3)(N-3)(4)](n) (3a), and a conglomerate, [Mn-2(L-3)(N-3)(4)](n)(.)nMeOH (3b). On the other hand, the ligand without amino and methyl substituents (L-4, 1, 4-bis(2-pyridyl)-2,3-diaza-1,3-butadiene) does not induce spontaneous resolution. The resulting compound, [Mn-2(L)(N-3)(4)](n) (4), consists of centrosymmetric 2D layers with alternating single diazine, single EE azido, and double end-on (EO) azido bridges, where the chirality is destroyed by the centrosymmetric double EO bridges. These compounds exhibit very different magnetic behaviors. In particular, 1 behaves as a metamagnet built of homometallic ferrimagnetic chains with a unique "fused-triangles" topology, 2 behaves as a 1 D antiferromagnet with alternating antiferromagnetic interactions, 3a and 3b behave as spin-canted weak ferromagnets with different critical temperatures, and 4 also behaves as a spin-canted weak ferromagnet but exhibits two-step magnetic transitions.