Supramolecular Capsules: Strong versus Weak Chalcogen Bonding

Abstract

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 K_a =786 m^-1 .

Keywords: X-ray diffraction; chalcogen bonding; mass spectrometry; self-assembly; supramolecular capsules.