Dual state emissive tridentate imidazopyridines with applications in acidochromism, metal ions detection, data encryption, and bioimaging

Four novel tridentate scaffolds IP-nTPA (n = 1, 4, 8, and 12), in which 2,6-bis(imidazo [1,2-a]pyridin-2-yl)pyridine and alkoxyl-substituted triphenylamine (TPA) are utilized as electron-donor and electron-acceptor, respectively, have been synthesized. Due to the inclusion of flexible alkoxyl chain to suppress π–π stacking in solids, IP-nTPA (n = 1, 4, 8) displayed efficient fluorescence in both solution and solid state. Meanwhile, IP-nTPA demonstrated an obvious solvatochromism with red-shifted emission when increasing solvent polarity, which is associated with the formed intramolecular charge transfer (ICT) states in the donor-acceptor (D-A) architecture. Theoretical calculations and single crystal structure analysis were utilized to interpret the emission behaviors in both solution and solid state. Importantly, IP-4TPA was chosen as the candidate to exhibit reversible acidichromism, metal ions detection, and information security application. Finally, the bioimaging application of IP-nTPA in PC-3 cells was investigated, which showed excellent biocompatibility and cell permeability.