RESUMO
Dibenzofuran (DBF) is converted to a vacuum-sublimable, electron-transporting host material via 2,8-substitution with diphenylphosphine oxide moieties. Close pi-pi stacking and the inductive influence of P=O moieties impart favorable electron-transport properties without lowering the triplet energy. A maximum external quantum efficiency of 10.1% and luminance power efficiency of 25.9 lm/W are realized using this material as the host for the blue-green electrophosphorescent molecule, iridium(III) bis(4,6-(di-fluorophenyl)pyridinato-N,C(2')picolinate (FIrpic).
RESUMO
The synthesis of the first completely characterized transition-metal complex containing a sulfur-bound 4,6-dimethyldibenzothiophene (4,6-Me(2)DBT) ligand, [CpRu(CO)(2)(eta(1)(S)-4,6-Me(2)DBT)]BF(4) (1) (Cp = eta(5)-C(5)Me(5)), is reported. X-ray studies of 1 and its 4-methyldibenzothiophene and dibenzothiophene analogues, [CpRu(CO)(2)(eta(1)(S)-4-MeDBT)]BF(4) (2) and [CpRu(CO)(2)(eta(1)(S)-DBT)]BF(4) (3), show that the Ru-S bond distances increase in the order, 3 < 2 < 1. Equilibrium studies on the series of [CpRu(CO)(2)(eta(1)(S)-DBTh)](+) compounds, where DBTh = DBT, 4-MeDBT, 4,6-Me(2)DBT, and 2,8-Me(2)DBT, show that the relative binding strengths of the dibenzothiophene ligands increase in the order 4,6-Me(2)DBT (1) < 4-MeDBT (20.2(1)) < DBT (62.7(6)) < 2,8-Me(2)DBT (223(3)). These results are the first to quantify the steric effect of 4- and 6-methyl groups on the sulfur-coordinating ability of dibenzothiophenes to transition-metal centers. They are also consistent with the proposal that 4- and 6-methyl groups reduce the coordination of dibenzothiophenes to active metal sites on hydrodesulfurization catalysts, which could account for the slow rate of 4-MeDBT and 4,6-Me(2)DBT hydrodesulfurization in petroleum feedstocks.
RESUMO
The complexes, CpRu(CO)2(BF4) and [CpFe(CO)2(eta2-2-methylpropene)][BF4], react with dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (4,6-Me2DBT) to give [CpRu(CO)2(DBT)][BF4] and [CpFe(CO)2(4,6-Me2DBT)][BF4], whose structures were established by X-ray diffraction studies. The same types of products are obtained when dibenzothiophenes react with CpRu(CO)2(BF4) and [CpFe(CO)2(THF)][BF4] that are adsorbed on the mesoporous silica SBA-15. DRIFT and XPS studies indicate that CpRu(CO)2(BF4) and [CpRu(CO)2(DBT)][BF4] are adsorbed on the SBA-15 by hydrogen-bonding of the BF4- anions to surface Si-O-H groups. CpRu(CO)2(BF4)/SBA-15 removes 99% of the DBT in a 45% toluene/55% hexanes simulated petroleum feedstock. This solid phase extractant is less successful for sterically-hindered 4,6-Me2DBT, as only 72% of it is removed. The results show that CpRu(CO)2(BF4) can be immobilized by adsorption on mesoporous silica and that it reacts with dibenzothiophenes in the adsorbed form, CpRu(CO)2(BF4)/SBA-15, in much the same way that it reacts in solution.
RESUMO
Anthraquinone-containing cyclic polyether hosts form 1:1 complexes with hydronium ion, producing large enhancements in luminescence via inversion of npi* and pipi* exited states. We have characterized the binding of hydronium ion within these host molecules and have synthesized a large variety of analogous hosts that contain different structural and electronic features that allow better understanding of what controls binding and luminescence capacity in this class of fluorescent sensor molecules. X-ray crystallography of an anthraquinone host that contains terminal amine functional groups rather than terminal ether groups is investigated, and complete proton transfer to carbonyl groups is observed in concentrated sulfuric acid media that also produces a previously unobserved luminescence.