Achieving Strong Positive Cooperativity through Activating Weak Non‐Covalent Interactions

• Published in: Angewandte Chemie 2018-01, Vol.130 (3), p.717-721
• Main Authors: Ma, Yan‐Long, Ke, Hua, Valkonen, Arto, Rissanen, Kari, Jiang, Wei
• Format: Article
• Language: English
• Subjects: Bonding strength; Cations; Chemical bonds; Chemical synthesis; Chemistry; Cooperativity; Crystal structure; Hydrogen bonding; Hydrogen bonds; Kooperativität; Makrocyclen; Selbstorganisation; Self-assembly; Single crystals; Supramolekulare Chemie; Tubes; Wirt-Gast-Chemie
• ISSN: 0044-8249; 1521-3757
• DOI: 10.1002/ange.201711077

Positive cooperativity achieved through activating weak non‐covalent interactions is common in biological assemblies but is rarely observed in synthetic complexes. Two new molecular tubes have been synthesized and the syn isomer binds DABCO‐based organic cations with high orientational selectivity. Surprisingly, the ternary complex with two hosts and one guest shows a high cooperativity factor (α=580), which is the highest reported for synthetic systems without involving ion‐pairing interactions. The X‐ray single‐crystal structure revealed that the strong positive cooperativity likely originates from eight C−H⋅⋅⋅O hydrogen bonds between the two head‐to‐head‐arranged syn tube molecules. These relatively weak hydrogen bonds were not observed in the free hosts and only emerged in the complex. Furthermore, this complex was used as a basic motif to construct a robust [2+2] cyclic assembly, thus demonstrating its potential in molecular self‐assembly. Äußerst komplex: Starke positive allosterische Kooperativität in einem ternären Komplex aus zwei molekularen Röhren beruht auf der Bildung von relativ schwachen C‐H⋅⋅⋅O‐Wasserstoffbrücken. Das stabile Bindungsmotiv wurde für die Konstruktion eines großen cyclischen [2+2]‐Komplexes verwendet.