Halogen-Bonded Bithiophene-Based Nanofibers for Luminescent Sensing

Discovery of new smart luminescent nanomaterials from small organic molecules possessing multiple useful properties is advantageous yet challenging. Self-assembling peptide-based molecules, which contained halogen-substituted (Cl, Br, and I) bithiophene chromophores, were developed to achieve organic luminescent nanomaterials. The dipeptide-based bithiophenes were fabricated to unidirectional nanofibers, and their novel applications were explored. The peptide analogues formed efficient luminescent organogelation, which displayed aggregation-induced emission. Further, the building blocks, 3,5′-dihalo-2,2′-bithiophene-5-carboxaldehydes, formed luminescent nanomaterials with aggregation-induced emission properties. Notably, the luminescence properties of the building blocks were exploited to sense the lethal cyanide ion, organic solvent, and moisture. The insight about the noncovalent interactions through NMR, solid-state X-ray crystallography, and Hirshfeld surface analyses revealed the existence of the halogen bonding of type C–I···O for 3,5′-diiodo-2,2′-bithiophene-5-carboxaldehyde for the self-aggregation process.