Interplay of Anion‐π^<i>+</i> and π^<i>+</i>‐π^<i>+</i> Interactions in Novel Pyrido[2,1‐<i>a</i>]isoquinolinium‐Based AIEgens ‐ Substituent‐ and Counterion‐Dependent Fluorescence Modulation and Applications in Live Cell Mitochondrial Imaging**

Abstract

Recently, the concept of anion-π⁺ interactions has witnessed unique applications in the field of AIEgen development. In this contribution, we disclose a consolidated study of a library of N-doped ionic AIEgens accessed through silver-mediated cyclization of pyridino-alkynes. A thorough photophysical, computational and crystallographic study has been conducted to rationalize the observed substituent- and counterion-dependent fluorescence properties of these luminogens. We further elucidate the prominent role of anion-π⁺ interactions, π⁺ -π⁺ interactions and other non-covalent interactions, in inhibiting the undesired ACQ effect. Finally, we have also demonstrated the application of selected AIEgens for imaging of mitochondria in live cells.