The symmetric multistate photo-switchable molecule 72, which contains two DHP units with a dibenzocyclophane as a spacer, was successfully synthesized by different routes using aryne-furan type Diels-Alder reactions. In the course of making 72, the intermediate furan 79 was synthesized, which upon deoxygenation gave photo-switchable furan 82. In a study of substitution effects on benzo[e]pyrene 21, the substituents phenyl, acetyl, nitro and phenylethynyl were attached to the 4,5-positions. The acetyl and nitro groups were introduced by direct substitution of 21, while coupling methodology were used for the phenyl and phenylethynyl groups. In the later case, a Suzuki coupling was used on bromide 69, followed by bromination, or a Sonogashira coupling was used on the bromoiodide 100, and then an aryne-furan Diels-Alder reaction and deoxygenation were used to give the final substituted benzo[e]pyrenes 105 and 103. The successful synthesis of the phenylbenzo[e]pyrene 105 enabled us to access the monosubstituted tris-pyrene system 120 through the reaction of bromophenylpyrene 107 and furan 79. The thermal return reactions (cyclophanediene to dihydropyrene) were studied on the benzo[e]pyrene derivatives and multistate photoswitch systems. Although the activation energies and enthalpies do not change much with substitution, the thermal return rates do appear to decrease with an electron withdrawing substituent. Photochromic studies were performed on 72 and 120. They both opened in a stepwise manner with one DHP ring opening and then the other, though the intermediate could not be isolated. A simple comparison of the photo opening and closing rates relative to benzo[e] pyrene 21 was performed under excess light conditions. All the derivatives of 21 synthesized in this thesis had faster visible opening rates than the parent 21; the UV closing rates did not change much however. / Graduate

This dissertation focuses on the photodissociation dynamics of stratospheric bromine and chlorine radical intermediates (BrO, ClO) along with reservoir species (ClONO2), which are known to play an important role at stratospheric ozone depletion. The experiments were carried out using a newly built velocity-map ion imaging apparatus which is an improvement over traditional translational spectroscopy studying photodissociation dynamics. The apparatus combines a collision-free molecular beam source with a laser-based pump-probe technique; i.e., single state pumping followed by a state-selective resonantly enhanced multiphoton ionization. Intense molecular beams were prepared using a custom-built flash pyrolytic source. The current research involves the development of fundamental properties of target species such as bond enthalpies and heats of formation, the chemical identification of photofragments, and their relative branching ratios, the excited states dynamics that lead to final products, partitioning of the available energy and finally the wavelength dependence of all these properties.

No description available.

No description available.

No description available.

The formal intramolecular photoredox reaction initially discovered for the parent 2- (hydroxymethyl)-9,10-anthraquinone (HMAQ) in aqueous solution was extended to a variety of anthraquinone derivatives 2.1-2.9, biphenyl anthraquinones 3.1-3.4 and acenequinones 4.1-4.4. The purpose of the study was to explore the generality of the unique photochemical reaction involving HMAQ, understand the mechanism of the reaction and develop potential applications. All the anthraquinones studied (except for 2.4) undergo the formal intramolecular photoredox reaction with a range of quantum yields (PHI =0.02-0.7). Mechanistic studies based on the parent compound HMAQ were carried out by product studies, isotope effects, solvent deuterium isotope effects, pH effect, triplet quenching studies, and laser flash photolysis. It was found that the formal intramolecular photoredox reaction involves a highly polarized triplet excited state in which the electron density of the benzylic CH20H moiety is transferred to the central anthraquinone ring. This highly polarized triplet excited state is subsequently trapped adiabatically by protonation at the anthraquinone carbonyl oxygen. / Graduate

Thesis (M.S.)--Rochester Institute of Technology, 1982. / Typescript. Includes bibliographical references (leaves 82-85).

Thesis (Ph. D.)--New York, University, 1934. / Vita. eContent provider-neutral record in process. Description based on print version record. Bibliography: p. 54-55.

Thesis (Ph. D.)--New York, University, 1934. / Vita. eContent provider-neutral record in process. Description based on print version record. Bibliography: p. 54-55.

Thesis (M.S.)--University of Wisconsin--Madison. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographies.