Fluorescent mesoionic 1-(2-aryl-4H-thieno[3,4-d][1,2,3]triazol-2-ium-4-ylidene)ethan-1-olates: One-pot synthesis, photophysics, and biological behavior

This paper reports the one-pot synthesis of a rare type of mesoionic compounds, which are condensed mesoionics. A series of new bicyclic arylthienotriazoliumolates was synthesized by an improved synthetic method. This approach has a large scope of starting materials and was used to obtain diverse structures with outstanding photophysical properties. The pattern of substituents decorating the mesoionic ring was the important factor determining the electronic distributions of the synthesized compounds. Pull–pull (А–π–A), push–push (D–π–D), pull–push (A–π–D), and push–pull (D–π–A) systems were designed, synthesized and their absorption, emission, stability, and biological behavior were studied. Quantum chemical calculations were performed to deepen the knowledge about the absorption and emission properties of these systems and explain their unusual geometries and electronic structures. Confocal microscopy experiments showed that thienotriazoliumolates easily penetrated into living cells and selectively accumulated near the cell membrane, Golgi apparatus, and endoplasmic reticulum.