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首页> 外文期刊>IUCrJ >Towards understanding π-stacking interactions between non-aromatic rings
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Towards understanding π-stacking interactions between non-aromatic rings

机译：理解非芳香环之间的π堆积相互作用

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摘要

The first systematic study of π interactions between non-aromatic rings, based on the authors' own results from an experimental X-ray charge-density analysis assisted by quantum chemical calculations, is presented. The landmark (non-aromatic) examples include quinoid rings, planar radicals and metal-chelate rings. The results can be summarized as: (i) non-aromatic planar polyenic rings can be stacked, (ii) interactions are more pronounced between systems or rings with little or no π-electron delocalization (e.g. quinones) than those involving delocalized systems (e.g. aromatics), and (iii) the main component of the interaction is electrostatic/multipolar between closed-shell rings, whereas (iv) interactions between radicals involve a significant covalent contribution (multicentric bonding). Thus, stacking covers a wide range of interactions and energies, ranging from weak dispersion to unlocalized two-electron multicentric covalent bonding (`pancake bonding'), allowing a face-to-face stacking arrangement in some chemical species (quinone anions). The predominant interaction in a particular stacked system modulates the physical properties and defines a strategy for crystal engineering of functional materials.
机译：基于作者自己的，由量子化学计算辅助的实验X射线电荷密度分析的结果，提出了对非芳香环之间π相互作用的第一个系统研究。具有里程碑意义的（非芳香族）实例包括喹啉环，平面自由基和金属螯合物环。结果可总结为：（i）可以堆叠非芳族平面多烯环，（ii）具有很少或没有π电子离域的环或环之间的相互作用比涉及离域系统的环或环（例如醌）更为明显。 （iii）相互作用的主要成分是闭壳环之间的静电/多极性，而（iv）自由基之间的相互作用涉及显着的共价贡献（多中心键合）。因此，堆叠涵盖了广泛的相互作用和能量，范围从微弱的分散性到非局域的两电子多中心共价键合（“薄饼键合”），允许某些化学物种（醌阴离子）面对面堆叠。在特定的堆叠系统中，主要的相互作用调节了物理性质，并定义了功能材料晶体工程的策略。

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