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首页> 外文期刊>Chemistry: A European journal >The Central Atom Size Effect on the Structure of Group 14 Tetratolyls
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The Central Atom Size Effect on the Structure of Group 14 Tetratolyls

机译：中心原子尺寸对第14族四甲苯基结构的影响

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The tetraphenyl derivatives of the Group 14 elements are of great potential interest as supramolecular constructs in extended porous networks.[1] The tetratolyl derivatives are particularly important precursors to usable constructs, courtesy of the ease of functionalisation at the site of the paramethyl group. The methyl groups constitute the outer contact sphere of individual tetratolyl molecules, making them particularly sensitive to the nature of the intermolecular interactions.Upon variation of the central atom, the methyl group dynamics allow a direct probe of these contact potentials across the complete series of materials. Due to the similar electronic properties of the different central atoms, the tolyl groups are chemically similar throughout the series meaning that the dominant effect is simply that of molecular size, which is dictated by the central atom. Methyl tunnelling spectroscopy is an extremely sensitive probe of intermolecular potentials and molecular interactions about torsional rotor units such a methyl groups, with high-resolution inelastic neutron scattering (hr-INS) spectroscopy being the most direct method to measure these small energy splittings.[2] This is most clearly manifested at low temperatures, with the internal molecular vibrations restricted primarily to the ground state. So-called methyl tunnelling transitions due to quantum interactions, or quantum tunnelling, of the wavefunctions of ground state rotors thermally trapped in the torsional potential energy minima and the equivalent positions about the torsional axis, result in observable transitions in hr-INS spectra.[2] Distinct peaks are obtained in the meV spectral region for each distinct methyl environment. In this respect, the tunnelling spectra can be related directly to the crystal structure. The heavier analogues, having tin and lead as the central atoms, are known to be isomorphic, in the space group I4ˉ,[3] with the silicon and germanium tetratolyl derivatives being reported under the Pc space group.[4] This is in stark contrast to the tetraphenyl species that are isomorphic throughout the Group 14 elements,[5] indicating that the methyl groups at the molecular periphery have profound effects on the extent of molecular packing interactions upon variation of the size of the central atom. The implication of existing structural data is that a symmetry break occurs at a central atom radius of about 1.3 (lying between the reported radii for germanium and tin atoms),[5b] presumably due to steric hindrance in the methyl group environments. However, the structure of the carbon analogue,obtained herein for the first time, indicates that it is of the same structure as the heavier tin and lead centred materials.
机译：作为扩展多孔网络中的超分子构建体，第14组元素的四苯基衍生物具有巨大的潜在兴趣。[1]由于对甲基的位点易于官能化，因此四甲苯基衍生物是可用构建体的特别重要的前体。甲基构成单个四甲苯基分子的外部接触球，使其对分子间相互作用的性质特别敏感。通过中心原子的变化，甲基动力学可以直接探测整个系列材料中的这些接触电势。 。由于不同中心原子的相似电子特性，在整个系列中，甲苯基在化学上是相似的，这意味着主要作用只是分子大小的作用，这是由中心原子决定的。甲基隧道光谱法是关于诸如甲基的扭转转子单元的分子间电势和分子相互作用的极其灵敏的探针，高分辨率非弹性中子散射（hr-INS）光谱法是测量这些小能量分裂的最直接方法。[2 ]这在低温下最为明显，内部分子振动主要限于基态。由于热陷在扭转势能极小值和扭转轴等效位置的基态转子的波函数的量子相互作用或量子隧穿引起的所谓甲基隧穿跃迁导致hr-INS光谱中可观察到的跃迁。[ 2]对于每种不同的甲基环境，在meV光谱区域均获得了不同的峰。在这方面，隧道光谱可以直接与晶体结构有关。在空间群I4ˉ，[3]中，以锡和铅为中心原子的较重类似物是同构的，据报道在Pc空间群下有硅和锗四甲苯基衍生物。[4]这与在第14组元素中同构的四苯基物质形成了鲜明的对比，[5]表明分子外围的甲基对中心原子大小变化对分子堆积相互作用的程度具有深远的影响。现有结构数据的含义是，对称断裂发生在中心原子半径约为1.3（位于所报告的锗和锡原子半径之间）处[5b]，这可能是由于甲基环境中的空间位阻所致。然而，本文首次获得的碳类似物的结构表明它与较重的锡和铅中心材料具有相同的结构。

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