In this study we report on the characterization of a series of pentacoordinate aluminum 8-hydroxyquinolines, AlQ 2X (X = F, Cl, Br), composed of two 8-hydroxyquinoline (8-HQ) groups and one halogen ligand. These were prepared by reacting 8-hydroxyquinoline and dialkylaluminum halide stoichiometrically. The λ maxs of absorption and emission were in the range of 385–388 and 515–516 nm, respectively, which were similar to AlQ 3. The molar absorptivity of AlQ 2X is similar regardless of the X group but emission efficiency of AlQ 2X is 2–3 fold higher than that of AlQ 3 when X = F or Br, but not when X = Cl. This result can be attributed to decreased quenching of energy due to a less steric environment by reducing quinolinate content. The overall molecular orbital structures and the absorption spectra of AlQ 2X and AlQ 3 are very similar due to a single quinolinate unit. The value of the potential difference of AlQ 2Xs between anodic and cathodic waves (Δ E = 3.12 V) is close to the estimated HOMO–LUMO energy gap (the optical band gap, Δ E optical ∼ 1240/ λ max), 3.19 eV. Detailed optical and electrochemical properties of AlQ 2X are discussed.