Positive Allosteric Control of Guests Encapsulation by Metal Binding to Covalent Porphyrin Cages

• Published in: Chemistry : a European journal 2019-01, Vol.25 (6), p.1481-1487
• Main Authors: Djemili, Ryan, Kocher, Lucas, Durot, Stéphanie, Peuronen, Anssi, Rissanen, Kari, Heitz, Valérie
• Format: Article
• Language: English
• Subjects: allosteric control; Allosteric properties; Binding; cage compounds; Cages; Chemical Sciences; Chemistry; Connectors; Crystal structure; Crystallography; Diimide; Encapsulation; host–guest systems; Naphthalene; Other; Porphyrins; Pyrazine; Pyrazines; Receptor mechanisms; Receptors; Silver; supramolecular chemistry; Triazoles; Zinc
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.201805498

The allosteric control of the receptor properties of two flexible covalent cages is reported. These receptors consist of two zinc(II) porphyrins connected by four linkers of two different sizes, each incorporating two 1,2,3‐triazolyl ligands. Silver(I) ions act as effectors, responsible for an on/off encapsulation mechanism of neutral guest molecules. Binding silver(I) ions to the triazoles opens the cages and triggers the coordination of pyrazine or the encapsulation of N,N′‐dibutyl‐1,4,5,8‐naphthalene diimide. The X‐ray structure of the silver(I)‐complexed receptor with short connectors is reported, revealing the hollow structure with a cavity well‐defined by two eclipsed porphyrins. Rather unexpectedly, the crystallographic structure of this receptor with pyrazine as a guest molecule showed that the cavity is occupied by two pyrazines, each binding to the zinc(II) porphyrin in a monotopic fashion. Allosteric receptor: Two flexible covalent cages showed an on/off encapsulation mechanism triggered by significant conformational changes upon silver(I) coordination to the peripheral binding sites. In addition, the X‐ray structures of the silver(I)‐bound receptor and of the one with pyrazine as the guest molecule confirmed the large cavity size of the receptor.