A Piperidine-Substituted Chalcone as a Molecular Rotor for Luminescent Viscosity Sensing
Modern applications make use of the luminescent materials and dyes for optoelectronics, textiles and fluorescence microscopy. Recently, organic-based fluorophores have garnered interest in fluorescent microscopy as brighter and non-toxic alternatives to metal complexes used in cell biology. While some organic fluorophores have emerged as commonly-used imaging agents, such as fluorescein and rhodamine, these lack the ability sense the microenvironment properties with spatial and temporal resolution. As a solution, we proposed a simple chalcone-based molecular rotor to sense cellular viscosity. A bulky piperidine ring is incorporated to undergo twisted intramolecular charge transfer (TICT) producing a dark, non-emissive state in fluid solution (e.g. water), but a rigid, emissive structure in a viscous environment (e.g. cellular membranes). Dyes were prepared via aldol condensation of the appropriate aldehyde and ketone pairs in low to moderate yields. Synthesis was confirmed by TLC, 1H NMR, and IR. The optical properties of the piperidine-substituted dye and a less bulky dimethylamino derivative were compared for molecular rotor properties and TICT. Preliminary results in dichloromethane reveal green fluorescence and modest quantum yields (~22%). Viscochromic properties in solution, future directions and possible applications will be presented.
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