Blue luminescent organoaluminum compounds:: Al(CH3)2(dpa), Al2(CH3)5(dpa)2, Al4(O)2(CH3)6(dpa)2, and Al(pfap)3, dpa = deprotonated di-2-pyridylamine, pfap = deprotonated 2-pentafluoroanilinopyridine

The reactions of Al(CH3)(3) with di-2-pyridylamine (dpaH) yielded a mononuclear zwitterion complex, Al(CH3)(2)(dpa) (1), a dinuclear complex, Al-2(CH3)(5)(dpa) (2), and a tetranuclear complex, Al-4(O)(2)(CH3)(6)(dpa)(2) (3), depending on the stoichiometry and conditions of the reactions. The crystal structures of all three compounds were determined by single-crystal X-ray diffraction analyses, All three compounds emit an intense blue color in solution and the solid state at lambda(max) = 475, 445, and 450 nm, respectively, when irradiated by an UV light. Molecular orbital calculations using ab initio methods (Gaussian 94) on dpa, dpaH, and compound 1 were performed which revealed that the aluminum ion in compounds 1-3 plays a key role in stabilizing the complexes and promoting the blue luminescence. The reaction of Al(CH3)(3) with 2-pentafluoroanilinopyridine (pfapH) resulted in the formation of a mononuclear octahedral complex, Al(pfap)(3) (4). Variable-temperature and COSY H-1 NMR established that compound 4 is highly fluxional in solution due to a rapid interconversion of mer and fac isomers, with the mer isomer dominating at low temperature. The structure of the fac isomer of 4 was determined by X-ray diffraction. Compound 4 emits at lambda(max) = 409 am when irradiated by an UV light.