The photochemical reaction of anthracene (A) with trans,trans-2,4-hexadiene (D) produces anthracene dimer (A(,2)), a major 4(pi)+4(pi) cross-adduct (Ad), and three minor cross-adducts: Ad' (4(pi)+4(pi)), Ad'' (4(pi)+2(pi)), and Ad''' (yet unknown). Quantum yields were studied as a function of anthracene and diene concentration and in the presence of a triplet sensitizer, a triplet quencher, and a heavy atom solvent in order to establish the role of excited anthracene singlets and triplets in product formation. Fluorescence quenching studies were conducted, when necessary, to obtain the appropriate rate constants for our mechanism. Using anthracene - ('14)C and isotopic dilution analysis, it was established that diene does not enhance, but instead diminishes dimer yields. The high A losses previously attributed to A(,2) formation were shown to be accounted for entirely by the thermal addition of Ad to A to give A(,2)d, a 2:1 anthracene to diene adduct. The structure of A(,2)d was established by X-ray crystallography, and thus the structure of Ad was confirmed by inference. These observations confirmed Kaupp's qualitative results concerning the role of diene in quenching A(,2) yields and thermal A(,2)d formation. The results presented demonstrate that Ad and Ad' are derived from the interaction of diene with anthracene singlets. Formation of Ad'' and Ad''', on the other hand, was shown to result from the interaction of diene with anthracene triplets. An excited triple complex, involving the interaction of A/D singlet exciplex with ground state A, is not a precursor leading to A(,2) or A(,2)d. Though the quantum yield expressions derived from the proposed mechanism are complex and contain many kinetic parameters, a large number of these parameters are known from previous spectroscopic and photochemical kinetic measurements. Thus the interpretation of the data / required a minimum number of derived parameters. These parameters describe the fate of singlet and triplet (A/D) exciplexes in cross-adduct formation ('1)(AD)*(--->) (beta) Ad + (beta)' Ad' + (1-(beta)-(beta)') (A+D); ('3)(AD)*(--->) (gamma) Ad'' = (gamma)' Ad''' + (1-(gamma)-(gamma)') (A+D) where (beta) = 0.46, (beta)' + 0.11, (gamma) = 0.16(,2), and (gamma)' = 0.052. / Source: Dissertation Abstracts International, Volume: 46-04, Section: B, page: 1168. / Thesis (Ph.D.)--The Florida State University, 1985.
| Identifer | oai:union.ndltd.org:fsu.edu/oai:fsu.digital.flvc.org:fsu_75570 |
| Contributors | DABESTANI, REZA., Florida State University |
| Source Sets | Florida State University |
| Detected Language | English |
| Type | Text |
| Format | 278 p. |
| Rights | On campus use only. |
| Relation | Dissertation Abstracts International |
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