4-Bromo-α-phenylethylamine-templated synthesis of a layered uranyl carboxyphosphonate coordination polymer as a dual-responsive luminescent thermometer

To develop uranyl carboxyphosphonate coordination polymer with distinct temperature-responsive behaviors, we substituted 4-bromo-α-phenylethylamine for α-phenylethylamine, successfully synthesizing a new layered uranyl carboxyphosphonate coordination polymer, [4-Br(α-C8H11N)][(UO2)2(2-pmb)(2-pmbH)(H2O)] (‌1‌). In compound ‌1‌, both uranyl ions adopt a pentagonal bipyramidal geometry: The five equatorial oxygen atoms of U1O7 originate from three bridging phosphonate groups, one bridging carboxylate group, and one coordinated H2O molecule, whereas the five equatorial oxygen atoms of U2O7 arise from three bridging phosphonate groups and one chelating carboxylate group. The ligands connect to the uranyl ions in two forms (2-pmb3- and 2-pmbH2-) to form an anionic layer, while racemic and protonated 4-bromo-α-phenylethylamine molecules serve as counterions occupying the interlayer space. Photoluminescence studies reveal that compound ‌1‌ emits intense green light at room temperature (QY = 10.49%), with six distinct fingerlike emission peaks observable in the 450–650-nm range. Notably, both the luminescence intensity and lifetime of compound ‌1‌ exhibit excellent linear temperature dependence over the range of 80–300 K, enabling it to function not only as a dual-responsive luminescent thermometer but also to demonstrate markedly different temperature sensing characteristics compared to prior systems.