Crystal structures, red-shifted luminescence and iodide-anion recognition properties of four novel D-A type Zn(ii) complexes

Four D-A type Zn(ii) coordination complexes, [Zn(C₂₉H₂₉N₃O₂)·(CH₃OH)]·(CH₃OH) (1), Zn₂(C₇₄H₉₀N₆O₄)·(CH₃OH) (2), [Zn(C₃₀H₂₈N₄O₂)·(CH₃OH)]·(CH₃OH) (3) and [Zn(C₃₈H₄₄N₄O₂)·(C₂H₅OH)]·(C₂H₅OH) (4), were designed, synthesized, and studied. Their fluorescence properties in the solid state and in THF solution were comprehensively analysed based on their single-crystal structures. The results showed that the red-shift of fluorescence emission from complexes 1 to 4 was successfully achieved via the strategy of enhancing intramolecular charge transfer (ICT) effects by increasing the number of electron-pulling and pushing groups gradually. Meanwhile, because of the fluorescence recognition abilities of these four complexes towards iodide anions in THF, they could be regarded as potential fluorescent sensors for I^- in this organic solution in the future.