Hertzog Jerald E, Maddi Vincent J, Hart Laura F, Rawe Benjamin W, Rauscher Phillip M, Herbert Katie M, Bruckner Eric P, de Pablo Juan J, Rowan Stuart J
Department of Chemistry, University of Chicago Chicago IL 60637 USA
Pritzker School of Molecular Engineering, University of Chicago Chicago IL 60637 USA.
Chem Sci. 2022 Apr 20;13(18):5333-5344. doi: 10.1039/d2sc01486f. eCollection 2022 May 11.
Ring size is a critically important parameter in many interlocked molecules as it directly impacts many of the unique molecular motions that they exhibit. Reported herein are studies using one of the largest macrocycles reported to date to synthesize doubly threaded [3]rotaxanes. A large ditopic 46 atom macrocycle containing two 2,6-bis(-alkyl-benzimidazolyl)pyridine ligands has been used to synthesize several metastable doubly threaded [3]rotaxanes in high yield (65-75% isolated) metal templating. Macrocycle and linear thread components were synthesized and self-assembled upon addition of iron(ii) ions to form the doubly threaded pseudo[3]rotaxanes that could be subsequently stoppered using azide-alkyne cycloaddition chemistry. Following demetallation with base, these doubly threaded [3]rotaxanes were fully characterized utilizing a variety of NMR spectroscopy, mass spectrometry, size-exclusion chromatography, and all-atom simulation techniques. Critical to the success of accessing a metastable [3]rotaxane with such a large macrocycle was the nature of the stopper group employed. By varying the size of the stopper group it was possible to access metastable [3]rotaxanes with stabilities in deuterated chloroform ranging from a half-life of <1 minute to 6 months at room temperature potentially opening the door to interlocked materials with controllable degradation rates.
环的大小是许多互锁分子中至关重要的参数，因为它直接影响到它们所展现出的许多独特分子运动。本文报道了使用迄今为止所报道的最大的大环之一来合成双股[3]轮烷的研究。一种含有两个2,6-双（-烷基-苯并咪唑基）吡啶配体的46原子大二价大环已被用于通过金属模板法高产率（分离产率为65 - 75%）地合成几种亚稳态双股[3]轮烷。大环和线性链组分被合成出来，并在加入铁（II）离子后自组装形成双股准[3]轮烷，随后可以使用叠氮化物 - 炔烃环加成化学方法加上封端基团。在用碱脱金属后，这些双股[3]轮烷通过多种核磁共振光谱、质谱、尺寸排阻色谱和全原子模拟技术进行了全面表征。对于用如此大的大环获得亚稳态[3]轮烷成功至关重要的是所采用的封端基团的性质。通过改变封端基团的大小，可以获得在氘代氯仿中稳定性范围从室温下半衰期小于1分钟到6个月的亚稳态[3]轮烷，这可能为具有可控降解速率的互锁材料打开大门。
