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THE PHOTOPHYSICAL PROPERTIES OF SOME C 15 LUPINE ALKALOIDS:
Author(s) -
Halpern ARTHUR M.,
FALCK CHRISTIAN,
LEGENZA MICHAEL W.
Publication year - 1989
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/j.1751-1097.1989.tb04073.x
Subject(s) - quinolizidine , fluorescence , chemistry , sparteine , quenching (fluorescence) , intersystem crossing , delocalized electron , photochemistry , excited state , stereochemistry , alkaloid , analytical chemistry (journal) , organic chemistry , physics , quantum mechanics , nuclear physics , singlet state
Sparteine, the tetracyclic saturated amine alkaloid, is highly fluorescent in n‐hexane solution (Φ f = 0.64; ζ= 63 ns) and has a large Stokes shift [λ max (abs) = 203 nm; λ max (fluor) = 325 nm]. Its isomer, α‐isosparteine, has similar properties: Φ f = 0.55; ζ f = 50 ns; λ max (fluor) = 338 nm. Oxidized derivatives, such as lupanine, thermopsine, and α‐diplospartyrine, are weakly fluorescent. Based on a comparison with spectroscopic and photophysical properties of the monoamine, quinolizidine, it is concluded that the excitation energy is delocalized over the two N‐atoms in starteine and a‐isosparteine. The self quenching rate constant for sparteine, ca. 1 times 10 7 M ‐1 s ‐1 , is about 100 times smaller than that for quinolizidine, consistent with excited state derealization. The significant fluorescence quenching in lupanine is rationalized by the fact that N‐methyl‐2‐piperidone mfe/molecularly quenches the fluorescence of quinolizidine at nearly the diffusion controlled rate in ‐hexane. Comparisons are made with the fluorescence properties of other diamines such as N, N'‐dimethylbispidine and N, N'‐disubstituted piperazines.