Exploring the Emissive Properties of New Azacrown Compounds Bearing Aryl, Furyl, or Thienyl Moieties: A Special Case of Chelation Enhancement of Fluorescence upon Interaction with Ca²⁺, Cu²⁺, or Ni²⁺

Three new compounds bearing furyl, aryl, or thienyl moieties linked to an imidazo-crown ether system (1, 2, and 3) were synthesized and fully characterized by elemental analysis, infrared, UV−vis absorption, and emission spectroscopy, X-ray crystal diffraction, and MALDI-TOF-MS spectrometry. The interaction toward metal ions (Ca²⁺, Cu²⁺, Ni²⁺, and Hg²⁺) and F⁻ has been explored in solution by absorption and fluorescence spectroscopy. Mononuclear and binuclear metal complexes using Cu²⁺ or Hg²⁺ as metal centers have been synthesized and characterized. Compounds 2 and 3 show a noticeable enhancement of the fluorescence intensity in the presence of Ca²⁺ and Cu²⁺ ions. Moreover compound 3 presents a dual sensory detection way by modification of the fluorimetric and colorimetric properties in the presence of Cu²⁺ or Hg²⁺. EPR studies in frozen solution and in microcrystalline state of the dinuclear Cu(II)3 complex revealed the presence of an unique Cu²⁺ type.