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)center dot(CH3OH)]center dot(CH3OH) (1), Zn-2(C74H90N6O4)center dot(CH3OH) (2), [Zn(C30H28N4O2)center dot(CH3OH)]center dot(CH3OH) (3) and [Zn(C38H44N4O2)center dot(C2H5OH)]center dot(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.