Synthesis, crystal structure, luminescent properties and photo degradation of mer-tris(8-Hydroxy-quinolinato-N, O)-indium(iii) hydrate 0.5 methanol solvate

Tris-(8-hydroxyquinioline) aluminium (Alq(3)) is widely used in organic light emitting diodes as an emission and electron transport layer. In this study the effect of solvent molecules, in the solid state crystal lattice, on the photoluminescence properties of synthesized mer-tris(8-Hydroxy-quinolinato-N, O)-indium(iii) hydrate 0.5 methanol solvate (mer-[ln(qn())3]center dot H2O center dot 0.5 CH3OH) was studied. Single crystals were obtained through a recrystallization process and single crystal X-ray diffraction was performed to obtain the unit cell structure. The main absorption peaks were assigned to ligand centered electronic transitions, while the solid state photoluminescence excitation peak at 440 nm was assigned to the 0-0 vibronic state of In(qn)(3). Broad emission at 510 nm was observed and was ascribed to the relaxation of an excited electron from the S-1-S-0 level. A powder sample was annealed at 130 degrees C for 2 h. A decrease in intensity was observed and could possibly be assigned to a loss of solvent species. To study the photon degradation, the sample was irradiated with an UV lamp for similar to 15 h. The emission data was collected and the change in photoluminescence intensity with time was monitored. High resolution X-ray photoelectron spectroscopy (XPS) scans of the 0-1s peak revealed that after annealing the binding energy shifted to lower energies indicating a possible loss of the H2O and CH3OH present in the crystal. The 0-1s peak of the degraded sample indicated the possible formation of C=O (similar to 532.5 eV),C-O-H and O=C-O-H (similar to 530.5 eV) on the phenoxide ring. (C) 2013 Elsevier B.V. All rights reserved.