Luminescent Coordination Polymer with Conjugated Lewis Acid Sites for the Detection of Organic Amines

A stable three-dimensional coordination polymer, [Eu-3(bcbp)(3)(NO3)(7)(OH)(2)](n) (1) (H(2)bcbp center dot 2Cl = 1,1'-bis(4-carboxyphenyl)-(4,4'-bipyridinium) dichloride), was prepared by the solvothermal reaction of Eu(NO3)(3)center dot 6H(2)O and H(2)bcbp center dot 2Cl in methanol, which was characterized by infrared spectroscopy, single-crystal X-ray diffraction, powder X-ray diffraction, and thermogravimetric analyses. In the solid state, 1 consists of an unusual trinuclear Eu(III) unit (Eu-3(CO2)(6)(NO3)(7)(OH), Eu-3-SBU), which further connects to six neighboring ones through six bcbp ligands to form a three-dimensional network. As expected, 1 exhibits a strong red-light emission at ambient temperature. Due to the presence of the electron-deficient bipyridinium moiety in the conjugation, this emission is selectively quenched by electron-rich organic amine compounds with high sensitivity and exhibits a prominent visual color change.