Picosecond absorption spectroscopy permitted direct detection of several new reactive intermediates in bond dissociation reactions. / Our study of 9-fluorenol and related substituted fluorenes led to a spectral assignment for the 9-fluorenyl cation, HFl$\sp+$, which exhibits a $\lambda\sb{\rm max}$ at 515 nm and has a lifetime of $<$20 ps in 9:1 H$\sb2$O/CH$\sb3$OH. In the non-nucleophilic solvent, trifluoroethanol, this lifetime increases to 1.25 ns. The 9-methyl-9-fluorenyl cation, which absorbs at 485 nm and has a lifetime of 275 ps in 9:1 H$\sb2$O/CH$\sb3$OH, was also characterized. The absorption spectrum of the 9-fluorenol cation radical was assigned to a 640-nm band which previously was assigned incorrectly to HFl$\sp+$. / Picosecond-pulsed irradiation of 9-diazofluorene in hexanes, cyclohexane, CH$\sb2$Cl$\sb2$, and CH$\sb3$CN permitted the observation of a precursor of the ground-state triplet carbene, 9-fluorenylidene ($\sp3$Fl:). The precursor absorbs at 415 nm in CH$\sb3$CN and is quenched by added CH$\sb3$OH with an apparent second-order rate constant of (2.3 $\pm$ 0.4) $\times$ 10$\sp9$ M$\sp{-1}$ s$\sp{-1}$. The 415-nm absorption band is assigned to singlet fluorenylidene, $\sp1$Fl:. This is the first observation of a singlet carbene which is not the ground state in room-temperature solution. / The photochemistry of diaryliodonium salts was found to be highly dependent on the identity of the counterion: diphenyliodonium salts with complex counterions such as BF$\sb4\sp-$ or PF$\sb6\sp-$ decompose in CH$\sb3$CN or CH$\sb2$Cl$\sb2$ via the iodobenzene cation radical to produce iodobenzene and protic acid. Salts with halide counterions, on the other hand, behave quite differently: excitation of diphenyliodonium chloride (Ph$\sb2$I$\sp+$ Cl$\sp-$), causes electron transfer to occur from Cl$\sp-$ to the diaryliodonium cation, which is followed by loss of a phenyl radical to form an iodobenzene/chlorine-atom complex ($\lambda\sb{\rm max}$ = 460 nm). The same complex is formed upon irradiation of iodobenzene dichloride. / The unsymmetrical p-anisylphenyliodonium salts exhibit similar behavior; however, the iodoanisole/chlorine-atom complex is unstable, and undergoes back-electron transfer to give the iodoanisole cation radical and chloride with a rate k = 6.7 $\times$ 10$\sp{10}$ s$\sp{-1}$. / Source: Dissertation Abstracts International, Volume: 51-09, Section: B, page: 4348. / Major Professor: Edwin F. Hilinski. / Thesis (Ph.D.)--The Florida State University, 1990.
| Identifer | oai:union.ndltd.org:fsu.edu/oai:fsu.digital.flvc.org:fsu_78321 |
| Contributors | Mecklenburg, Sandra L., Florida State University |
| Source Sets | Florida State University |
| Language | English |
| Detected Language | English |
| Type | Text |
| Format | 269 p. |
| Rights | On campus use only. |
| Relation | Dissertation Abstracts International |
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