Supramolecular Capsules: Strong versus Weak Chalcogen Bonding

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 center dot center dot center dot N distances (<= 2.9 angstrom) 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 pi-pi stacking array. The association constant to form the dimeric capsule in [D-8]THF at 283 K, solely based on weak 2S-2N square interactions, was determined as K-a = 786 M-1.