Benzo-15-crown-5 functionalized polydiacetylene-based colorimetric self-assembled vesicular receptors for lead ion recognition

A novel crown functionalized diacetylene monomer, N-(2,3,5,6,8,9,11,12- octahydrobenzo[b][1,4,7,10,13] pentaoxacyclopentadecin-15-yl) pentacosa-10,12-diynamide (BCDA), was synthesized successfully. The copolymerized composite vesicles of BCDA and 10,12-pentacosadiynoic acid (DA) with embedded receptor sites for metal ions have been prepared and characterized. Their response to the presence of metal cations in aqueous solution has been investigated by monitoring changes of color and UV-vis absorption. Upon addition of a series of alkali, alkaline earth and transition metal cations such as Na⁺, K⁺, Mg²⁺, Ca ²⁺, Fe²⁺, Co²⁺, Cu²⁺, Mn ²⁺, Ba²⁺, Cd²⁺, Ag⁺, Pb²⁺ and Zn²⁺, only Pb²⁺ ion could induce a color change from blue to red observable by the naked eye, which clearly showed that PBCDA-PDA composite vesicles could act as a highly selective and sensitive probe to detect Pb²⁺ ions in aqueous solution with minor interference from other metal ions. The excellent Pb²⁺ ion selectivity of PBCDA-PDA composite vesicles was mainly attributed to the stronger complexation behavior of Pb ²⁺ with crown ethers and the carboxylic acid at the lipid-solution interface which could perturb the polydiacetylene backbone.