Unexpected halide anion binding modes in meso-bis-ethynyl picket-calix[4]pyrroles: effects of meso- (ethynyl) extension

meso-Ethynyl extended aryl-picket calix[4]pyrroles 2 and 3 are designed and synthesized by directly anchoring arylethynyl groups at diametrically opposed meso-positions. The critical roles of direct ethynyl linkers are manifested through the isolation of unexpected host-anion conformers of meso-arylethynyl calix[4]pyrroles and a significant enhancement in halide binding affinities.