The triple layered tetraazacyclophane 3a was prepared in high yield by a fourfold bond connection in a one-pot reaction sequence. The helical chirality of 3a results from the unique crossed meta/meta-cyclophane linkage. A racemisation process can only take place by breaking a covalent bond. The X-ray structure analysis of 3a proved the constitution of the isomer, difficult to determine by spectroscopy
The hitherto longest molecular ribbons (4–6), composed of several [3.3]metacyclophane units, are synthesized using a new iterative synthetic strategy, up to a length of seven fourfold-bridged benzene rings, and it is proved by X-ray crystal structural analyses and 1H NMR spectroscopy that these molecules form meander-type folded syn conformations leading to multiple π-staples.
通过 X 射线晶体结构分析和 1H NMR 光谱分析证明,这些分子形成了蜿蜒型折叠合成构象,导致多个 π-带。