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

A stable
three-dimensional coordination polymer, [Eu3(bcbp)3(NO3)7(OH)2]n (1) (H2bcbp·2Cl = 1,1′-bis­(4-carboxyphenyl)-(4,4′-bipyridinium)
dichloride), was prepared by the solvothermal reaction of Eu­(NO3)3·6H2O and H2bcbp·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
(Eu3(CO2)6(NO3)7(OH), Eu3–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.