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.