H-aggregate triggered mechanochromic luminescence property of 7-(diethylamino)-coumarin-3-carbaldehyde oxime derivative

Abstract

For the organic luminogens, the packing structure and fluorescent emission of H-aggregate could be affected by mechanical stimuli. According to the finding, here a new coumarin oxime derivative 4-chloro-7-(diethylamino)-coumarin-3-carbaldehyde oxime A1 showing reversible mechanochromic luminescence (MCL) property was developed. Optical properties study in the solution and DFT calculation revealed that A1 had ICT nature. The emission wavelength in solid state of A1 changed reversibly from 515 nm to 540 nm upon mechanical stimuli and solvent treatment. To demonstrate the relationship between MCL property and molecular structure, another three relative coumarin oxime compounds were synthesized. The results showed that the formation of H-aggregate in solid state observed by X-ray diffraction analysis was considered to be responsible for MCL property of A1, and the intermolecular H-bonding caused by oxime hydroxyl group played a key role in the formation of H-aggregate. Furthermore, the potential application in rewritable data storage based on the MCL behavior of A1 was studied.