Benzylidenecyclohexanone-triazole-based conjugated polymer: Click synthesis, Staudinger end-capping and application as optical probe scaffold

• Benzylidenecyclohexanone-triazole based conjugated polymer (P5) was synthesized.
• Fluorescence of P5 was specifically quenched by the introduction of I−.
• Fluorescence turn-on probing of Hg2+was achieved by P5/I−assembly.
• Phosphinimine-endcapped polymer (P5-TPP) was obtained by Staudinger reaction.
• P5-TPP displayed fluorescence ratiometric alteration toward hypochlorite ion.

A type of benzylidenecyclohexanone-triazole based conjugated polymer (P5) was successfully synthesized by Cu+-catalyzed Click reaction. The THF solution of P5 exhibited specific optical response (increase in absorption and decrease in fluorescence) toward I−. With the further addition of Hg2+ into the assembly of P5-I−, distinctive recovery of optical properties was detected, suggests that P5-I− adduct can act as fluorescence turn-on probing platform for Hg2+. Post-polymerization of P5 was implemented by catalyst-free Staudinger reaction between P5 and triphenylphosphine to afford phosphinimine-endcapped polymer (P5-TPP). Different from the blue-greenish emission (∼490 nm) of P5, P5-TPP emitted yellow light (∼550 nm) in THF–water mixture (VTHF/Vwater = 2/8). P5-TPP displayed specific fluorescence ratiometric alteration toward hypochlorite ion in THF–water mixture (VTHF/Vwater = 2/8, pH = 7.4), which might be due to the hypochlorite-induced hydrolysis of phosphinimine energy-transfer acceptors in P5-TPP. The results suggest that P5 can act as structure scaffold for the construction of optical probe for triple analytes (I−, Hg2+ and ClO−).

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