Supramolecular Capsules: Strong versus Weak Chalcogen Bonding

• Published in: Angewandte Chemie International Edition 2018-12, Vol.57 (52), p.17259-17264
• Main Authors: Riwar, Leslie‐Joana, Trapp, Nils, Root, Katharina, Zenobi, Renato, Diederich, François
• Format: Article
• Language: English
• Subjects: Bonding strength; chalcogen bonding; Chalcogen bonds; Crystal structure; Crystallization; Dimers; Ionization; Ions; Mass spectrometry; Mass spectroscopy; self-assembly; Solvents; supramolecular capsules; X-ray diffraction
• ISSN: 1433-7851; 1521-3773
• DOI: 10.1002/anie.201812095

Resorcin[4]arene cavitands containing either 2,1,3‐benzotelluradiazole or 2,1,3‐benzothiadiazole motifs were dimerized to supramolecular capsules by chalcogen bonding. Their respective behavior varied depending on the interaction strength of the chalcogen bonds with Te forming strong interactions and S weak interactions. The tremendous strength of multiple 2Te–2N square interactions led to formation of a chalcogen‐bonded dimeric capsule in all solvents, as shown by X‐ray crystal structures with 16 short Te⋅⋅⋅N distances (≤2.9 Å) and confirmed by native electrospray ionization mass spectrometry (ESI‐MS). With the S cavitand, solvent‐dependent crystallization resulted in different arrangements: either a shifted 2S–2N square‐bonded capsule or an interlocked 1D polymer with an infinite π–π stacking array. The association constant to form the dimeric capsule in [D8]THF at 283 K, solely based on weak 2S–2N square interactions, was determined as Ka=786 m−1. Strengths and weaknesses: Dimeric chalcogen‐bonding capsules display a distinct behavior depending on the association strength, as shown by X‐ray structures and confirmed by NMR spectroscopy solution studies. While capsules based on weak S⋅⋅⋅N interactions rely on solvation and the associated hemisphere preorganization, capsular assemblies formed by strong Te⋅⋅⋅N interactions are beyond external influences.