A type of novel fluorescent phosphinimine derivative: Catalyst-free simple synthesis and optical properties

• A type of fluorescent phosphinimine derivative (M1) was successfully prepared.
• No requirement for any metal-catalyst in the synthesis process.
• Fluorescence of M1 was efficiently quenched by the introduction of H+.
• Fluorescence of M1-H+ complex recovered quickly with the presence of F−.
• Response to pH can also be clearly observed by naked eyes.

A type of fluorescent benzylidene cyclohexanone-containing phosphinimine derivative, 2,6-bis(4-triphenylphosphiniminebenzylidene)-4-methyl-cyclohexanone, has been synthesized by catalyst-free Staudinger reaction. Chemical structure of this compound was verified by Fourier Transform Infrared Spectroscopy, Nuclear Magnetic Resonance and Electrospray Ionization analyses. Optical properties of this compound in different solvents were investigated by Ultraviolet–visible spectroscopy and fluorescence analyses. Pale-yellow color of the dimethyl sulfoxide solution of this compound subsequently took off with the presence of incremental H+, accompanied by the quenching of its fluorescence. Furthermore, the color and fluorescence of this compound recovered gradually when H+ in the solution being neutralized, indicating that it could be applied as reversible optical pH indicator.

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