Heavy atom induced phosphorescence of organic materials using mono- and trifunctional organomercury derivatives
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This dissertation focuses on the phosphorescence of organic chromophores using perfluoro-ortho-phenylene mercury (1) and bis(pentafluorophenyl)mercury (2) as external heavy atom effect inducers. To ascertain the suitability of these luminescent adducts for OLED applications, several research objectives have been investigated. To further shorten the triplet lifetimes of adducts involving 1, a strategy was developed which combines both internal and external heavy atom effects. Specifically, complexes involving 1 and N-methylcarbazole, N-methylindole and the 1- halonaphthalenes were investigated. The existence and stability of the complexes could be confirmed in solution by fluorescence spectroscopy. In the solid state, these adducts form supramolecular binary stacks where the molecules of 1 alternate with the aromatic substrate. As a result of the mercury external heavy atom effect, all of these adducts display intense room temperature phosphorescence of the free arene. With the Nheterocycles, the triplet lifetimes were drastically reduced to below 100 mu-s. To appreciate the origin of the unusual heavy atom effects observed in arene adducts with 1, 2 was studied as a monofunctional analog to 1. By utilizing fluorescence spectroscopy, naphthalene, biphenyl, and fluorene complexes of 1 and 2 have been detected in solution. The solid state structure of the adducts with 2 reveal supramolecular binary stacks. Comparison of the photophysical results supports the occurrence of cooperative effects between the Lewis acidic mercury centers of 1, which make it a more efficient external heavy-atom effect inducer. Polymeric materials which are amenable to deposition in thin layers were investigated as substrates for 1 and 2. Both poly(vinyl-2-naphthalene) and poly(vinylcarbazole) interact with 1 and 2 in solution as evidenced by fluorescence spectroscopy. With the solid blend 1•PVK, a small doping percentage of 1 results in white emission, while larger percentages of 1 yield bright orange emission. This dissertation presents the first structurally characterized ternary complex with 1, carbazole, and coordinating solvents THF and triethylamine. IR spectroscopy and short N···O and N···N distances in the solid state indicates that the acidic N-H moiety of carbazole interacts with the solvent by hydrogen bonding. In the extended structure, molecules of 1 and the hydrogen bonded complex alternate to form supramolecules.
Burress, Charlotte Nicole (2006). Heavy atom induced phosphorescence of organic materials using mono- and trifunctional organomercury derivatives. Doctoral dissertation, Texas A&M University. Available electronically from