Synthesis and complexing properties of molecular probes linked with fluorescent phosphane oxide derivatives

• Fluorescent sensors based on conjugated phosphane oxide linked with amino group.
• Efficient charge transfer upon visible excitation and high fluorescence quantum yield.
• Coordination of Cd2+and Pb2+ showed different changes of photophysical properties.

Synthesis and host-guest interactions with various metal ions of two molecular fluorescent probes containing either an aza-crown or a dialkylamino group and a phosphane oxide are reported. These probes were designed and synthesized with rod-shaped push-pull fluorophores containing phosphane oxide as electron-withdrawing group conjugated to an amino electron-donating group by an arylene–ethynylene–arylene–ethylene–arylene linker. A five-steps straightforward convergent synthesis of the phosphane oxide derivatives in moderate overall yields has been proposed. Their high fluorescence quantum yields and DFT calculations indicated that an efficient intramolecular charge transfer occurred upon light excitation. In order to understand the interactions and affinities of these compounds with different cations, changes in their absorption and emission properties upon addition of heavy metal ions and alkali ions were evaluated. By calculating the binding constants and studying the photochemical properties changes, we demonstrated the importance of structure, charge density and cooperative effect of the complexing units

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