Synthesis, structure and luminescence study of a binuclear aluminium complex: A novel structure containing six coordinated aluminium atoms in two distinct coordination geometries

Novel binuclear complexes of aluminium alkoxides were prepared by the reaction of 8-hydroxyquinoline with aluminium 2-methoxyethoxide and aluminium 2-ethoxyethoxide in refluxing benzene. Both compounds, [Al(C9H6NO)2(μ-OCH2CH2OR)]2 [where R = CH3 (1) and C2H5 (2)], have been characterized by elemental analysis and spectral studies. The molecular structure determination of compound 2 by single crystal X-ray analysis revealed a discrete unsymmetrical dimer (C2 symmetry) containing aluminium atoms in two distinct coordination geometries that are linked to each other by two bridging alkoxy groups. 27Al NMR spectra of compounds 1 and 2 shows that the solid state structure of the complexes is not retained in solution, and four-coordinate aluminium atoms form in solution. Both compounds display luminescence upon illumination by UV light. Specific rotation measurements show that for both complexes extra enantiomers (ee) exist in solution. The hydroxyquinoline derivatives of both aluminium alkoxides have good solubility in common organic solvents and have suitable thermal stability.

The reaction of 8-hydroxyquinoline with aluminium 2-methoxyethoxide and aluminium 2-ethoxyethoxide in refluxing benzene leads to the formation of luminescent complexes [Al(C9H6NO)2(μ-OCH2CH2O–CH3)]2 and [Al(C9H6NO)2(μ-OCH2CH2O–CH2CH3)]2. X-ray structure analysis reveals two distinct coordination geometries for the aluminium atoms in the binuclear complex.Figure optionsDownload as PowerPoint slide