PART I: INVESTIGATIONS OF THE AZOALKANE TRIPLET STATE THROUGH INTRAMOLECULAR ENERGY TRANSFER. PART II: PHOTOCHEMICAL AND PHOTOPHYSICAL STUDIES OF AZO-1-BICYCLO(2.2.1)HEPTANE
HORSEY, DOUGLAS WAYNE
Doctor of Philosophy
Part I. Several azoalkane-triplet sensitizer bichromophoric systems are synthesized and the energy transfer properties are studied. Intramolecular energy transfer to azoalkanes is found to be much slower than literature cases with aromatic hydrocarbon acceptors. This is the first study of intramolecular energy transfer to a small chromophore. Energy transfer efficiencies are studied by measurement of phosphoresence intensities and lifetimes in low temperature glasses. Polymethylmethacrylate is used as a rigid matrix for some emission studies. Competitive intra and intermolecular quenching experiments and the corresponding Stern-Volmer plots are used to determine energy transfer rates in solution. Eventually a bichromophoric system (AP-DBO) is synthesized that has both the desired rapid intramolecular energy transfer and a quenchable azo triplet lifetime of (TURN)7 ns. Attempts to observe the azo triplet by transient techniques are unsuccessful. The triplet energies of several azos are estimated by kinetic spectroscopy using a graded series of sensitizers and the singlet-triplet energy gap is found to be constant at about 20 kcal/mol. Part II. The photochemical isomerization of azo-1-bicyclo 2.2.1 heptane is studied on long and short wavelength irradiation. Long wavelength irradiation yields (PHI)(,c(--->)t) = (PHI)(,t(--->)c) = 0.5. Isomerization quantum yields on 193 nm irradiation from an ArF laser are much lower than 0.5 and some deazatization occurs. An energy level diagram is presented to account for the observed results. Attempts are made to determine the triplet energy of cis-axo-1-bicyclo 2.2.1 heptane utilizing kinetic spectroscopy. The large triplet sensitized (PHI)(,c(--->)t) combined with the lability of the compound thwarted this investigation.