Studies on curcumin and curcuminoids. XXXIX. Photophysical properties of bisdemethoxycurcumin.
Bottom Line: The steady-state absorption and fluorescence, as well as the time-resolved fluorescence properties of bisdemethoxycurcumin dissolved in several solvents differing in polarity and H-bonding capability were measured.The bisdemethoxycurcumin decay mechanisms from the S(1) state were discussed and compared with those of curcumin.The differences in S(1) dynamics observed between bisdemethoxy-curcumin and curcumin could be ascribed to a difference in H-bond acceptor/donor properties of the phenolic OH and a difference in strength of the intramolecular H-bond in the keto-enol moiety within the two molecules.
Affiliation: Department of Physics and Mathematics, University of Insubria and C.N.I.S.M.-C.N.R., Via Valleggio, 11- 22100 Como, Italy. email@example.comShow MeSH
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Mentions: The absorption maxima, λAbs, of bisDMC in the different solvents are shown in Table 2. In all solvents except cyclohexane the absorption spectra were broad and essentially structureless and the absorption maximum was blue-shifted with respect to that of CURC . Some representative spectra are reported in Fig. 3a. In cyclohexane, bisDMC was rather insoluble, and only a noisy spectrum could be recorded even for a saturated solution. The main absorption band was observed in the UV, with peaks at 348 nm and 362 nm, respectively. The spectrum also displayed a shoulder around 380 nm. A second absorption band above 400 nm was barely detectable. The situation was opposite for CURC in cyclohexane  where the main absorption band was indentified above 400 nm and the near UV band was minor. For both compounds a systematic red shift was observed when changing from cyclohexane to solvents with higher dielectric constants and from weaker to stronger H-bonding solvents of comparable polarity. However, there was no linear correlation between either ε, α or β and λAbs. Conversely, λAbs remained constant within one solvent category (see Table 2 for bisDMC and  for CURC), but was markedly different from one category to another.Table 2
Affiliation: Department of Physics and Mathematics, University of Insubria and C.N.I.S.M.-C.N.R., Via Valleggio, 11- 22100 Como, Italy. firstname.lastname@example.org