Using noncovalent intra-strand and inter-strand interactions to prescribe helix formation within a metallo-supramolecular system
Using noncovalent intra-strand and inter-strand interactions to prescribe helix formation within a metallo-supramolecular system
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DOI：
10.1002/chem.200400169
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发表时间：
2004-09-06
影响因子：
4.3
通讯作者：
Hannon, ML
中科院分区：
文献类型：
--
作者：
Childs, LJ;Pascu, M;Hannon, ML
在金属-超分子体系中探讨了链间和链内相互作用的影响，其中金属-配体的配位要求可以通过多种不同的超分子结构来满足。这是通过在容易制备的双(吡啶亚胺)配体的间隔基上引入烷基取代基来实现的。烷基取代基在配体链中诱导扭曲，这种链内效应有利于螺旋结构的形成。烷基取代基还将链间相互作用引入体系中。对于较小的甲基，它们被最有效地容纳在三核圆形螺旋结构中。双核双螺旋和三核圆螺旋的溶液混合物，对铜(I)来说，三核圆螺旋结晶。CH…pi相互作用使圆形螺旋体具有碗状构象，三角形单元聚集成四面体球状阵列。低温核磁共振研究表明，在溶液中，CH…pi相互作用也使三角形形成碗状构象。在低核度双螺旋体系中，较大的乙基可以维持链内CH...pi相互作用，这是该配体体系在溶液和固体中的独特结构。描述了铜(I)和银(I)络合物的晶体结构。因此，我们表明，链内相互作用可以用来在这个系统内诱导螺旋性，而阵列的成核性可以由链间相互作用来规定。
The effect of inter-strand and intra-strand interactions is explored in a metallo-supramolecular system in which the metal-ligand coordination requirements may be satisfied by more than one different supramolecular architecture. This is achieved by introducing alkyl substituents onto the spacers of readily prepared bis(pyridylimine) ligands. The alkyl substituents induce twisting within the ligand strand and this intra-strand effect favours formation of helical architectures. The alkyl substituents also introduce interstrand CH...pi interactions into the system. For the smaller methyl group these are most effectively accommodated in a trinuclear circular helicate architecture. A solution mixture of dinuclear double-helicate and trinuclear circular helicate results from which, for copper(i), the trinuclear circular helicate crystallises. The CH...pi interactions endow the circular helicate with a bowl-shaped conformation and the triangular unit aggregates into a tetrahedral ball-shaped array. Low-temperature NMR studies indicate that the CH...pi interactions also confer a bowl-shaped conformation on the triangle in solution. The larger ethyl groups can sustain intra-strand CH...pi interactions in the lower nuclearity double-helical system and this is the unique architecture for that ligand system in both solution and the solid state. Crystal structures are described for both the copper(I) and silver(I) complexes. Thus we show that intra-strand interactions may be used to induce helicity within this system, while the nuclearity of the array can be prescribed by the interstrand interactions.