Spiro Compounds for Organic Electroluminescence and Related Applications

Synthesis, characterization, crystal structure and DFT studies on 1',3'-dihydrospiro[fluorene-9,2'-perimidine]

The title compound, 1',3'-dihydrospiro[fluorene-9,2'-perimidine] has been synthesized and characterized by NMR, ESI-MS, IR, elemental analysis, UV-vis and fluorescence spectroscopy. The crystal structures of the title compound and its co-crystal with 9-fluorenone have also been determined by X-ray single crystal diffraction. Density functional theory (DFT) calculations and vibrational frequencies have been performed at B3LYP/6-31G* level. The comparisons between the experimental vibrational frequencies and the predicted data show that B3LYP/6-31G* method can simulate the IR of the title compound on the whole. The theoretical electronic absorption spectra have been calculated by using TD-DFT method and compared with the experimental result. The solid-fluorescence determination of the title compound reveals two emission bans at 430 and 590 nm while its co-crystal reveals only one emission band at 590 nm.

Synthesis of a highly luminescent three-dimensional pyrene dye based on the spirobifluorene skeleton

We have synthesized a highly luminescent (log e > 5.0, F > 0.9) pyrene dye based on a spirobifluorene skeleton [2,2',7,7'-tetrakis(7-tert-butyl-1-pyrenyl)-9,9'-spirobi[9H-fluorene; 4-PySBF]. The use of spirobifluorene prevents fluorescence quenching by intramolecular energy transfer and/or electron transfer among the chromophores in the excited state. The emission spectra of 4-PySBF exhibited a red shift of 20 nm in comparison to a model compound [9,9'-dioctyl-2,7-bis(7-tert-butyl-1-pyrenyl)-9H-fluorene; 2-PyF], but its UV-Vis spectrum remained unchanged.

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 co-planar (with an average dihedral angle of only about 1.621degrees). The hydroxyl group is in trans position to the pyrido[1,2-a]pyrimidin heterocyclic moiety. The molecules are linked by the N-HO, O-HO and C-HO hydrogen bonds into two-dimensional sheets. Additionally, the pi-pi interactions (average distance 3.3680 A) 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).

2,2',7,7'-Tetra-bromo-9,9'-spiro-bifluorene toluene hemisolvate

There are two independent mol­ecules and one toluene solvent mol­ecule in the asymmetric unit of the title compound, C₂₅H₁₂Br₄·0.5C₇H₈. The dihedral angles between the fluorene ring systems are 85.30 (6) and 84.95 (6)° in the two mol­ecules. The disortions in angles from the ideal sp³-hybridization geometry around the tetra­hedral C atoms are due to the strain imposed by the central five-membered ring and steric effects.

Spiro-bridged ladder-type poly(p-phenylene)s: towards structurally perfect light-emitting materials

Structurally perfect spiro-bridged ladder-type poly(p-phenylene)s, which show blue fluorescence in the photoluminescence (PL) and electroluminescence (EL) emission spectra, are prepared by Suzuki-Miyaura polycondensation and Friedel-Crafts cyclization. The polymers are free of ketonic defects, exhibiting excellent thermal and color stability upon annealing in air at 110 degrees C for 24 h.

Synthesis of Monodisperse Spiro-Bridged Ladder-Type Oligo-p-phenylenes

Monodisperse spiro-bridged ladder-type oligo-p-phenylenes, which have very rigid backbones, exhibited intensive emissions with very small Stocks shifts, displayed very good color stability upon thermo-oxidation, and were synthesized by Suzuki cross-coupling, oxidation, and BF3.ether-catalyzed cyclization reactions.