A blue-emitting organic compound 9-hydroxyl-3-hydroxyethyl-2-methyl-4H-pyrido[1,2-a]pyrimidin-4-one: Synthesis, crystal structure and luminescent properties

A blue-emitting organic compound, 9-hydroxyl-3-hydroxyethyl-2-methyl-4H-pyrido[1,2-a]pyrimidin-4-one (I), was synthesized by the reaction of 2-amino-3-hydroxylpridine with 2-acetylbutyrolactone. The crystal of the title compound in larger size was reported for the first time through the slow evaporation method. The whole molecule in the crystal is non-planar, but the two conjugated rings are almost coplanar (with an average dihedral angle of only about 1.621 degrees). The hydroxyl group is in trans position to the pyrido[1,2-a]pyrimidin heterocyclic moiety. The molecules are linked by the N-H center dot center dot center dot O, O-H center dot center dot center dot O and C-H center dot center dot center dot O hydrogen bonds into two-dimensional sheets. Additionally, the pi-pi interactions (average distance 3.3680 angstrom) interconnect the sheets stabilizing the crystal structure. At room temperature, the compound exhibits an intense blue emission at 432 nm upon 323 nm excitation in the solid state. The simple EL device with the configuration of ITO/I + PMMA/Ag was fabricated, where the compound (I) was used as a main emitting material. The EL device fabricated had a maximum brightness of 289 cd m(-2). The thermal stability of the compound was also investigated by thermogravimetric analysis (TGA). (C) 2010 Elsevier B.V. All rights reserved.