Three green luminescent cadmium complexes containing 8-aminoquinoline ligands: Syntheses, crystal structures, emission spectra and DFT calculations

Three complexes, Cd(8-aminoql)₂×₂ (8-aminoql=8-aminoquinoline; X^-=ClO₄^-, SCN^-, 1 and 2, respectively) and Cd(8-aminoql)(N₃)₂ (3), were synthesized and structurally characterized. For each complex, the Cd²⁺ ion exhibits distorted octahedral coordination geometry. Two 8-aminoquinoline molecules and two counter-anions are coordinated to the Cd²⁺ center to form a mononuclear species with two trans-ClO₄^- anions for 1, while two SCN^- anions adopt a cis-configuration for 2. The intermolecular H-bonding interactions between the -NH₂ groups and the O atom (1) and the S atom (2) result in the formation of a 2-D layered structure. In the crystal of 3, the N₃^- anions bridging the neighboring Cd(8-aminoql)²⁺ units form a 1-D coordination polymer. The three complexes emit green luminescence. The emission bands possess a broad asymmetric feature, which can be assigned to L′LCT transitions based on DFT and TDDFT calculations.