Ultrafast transient lens spectroscopy of various C40 carotenoids: lycopene, β-carotene, (3R,3′R)-zeaxanthin, (3R,3′R,6′R)-lutein, echinenone, canthaxanthin, and astaxanthin

Abstract

The ultrafast internal conversion (IC) dynamics of seven C(40) carotenoids have been investigated at room temperature in a variety of solvents using two-color transient lens (TL) pump-probe spectroscopy. We provide comprehensive data sets for the carbonyl carotenoids canthaxanthin, astaxanthin, and-for the first time-echinenone, as well as new data for lycopene, beta-carotene, (3R,3'R)-zeaxanthin and (3R,3'R,6'R)-lutein in solvents which have not yet been investigated in the literature. Measurements were carried out to determine, how the IC processes are influenced by the conjugation length of the carotenoids, additional substituents and the polarity of the solvent. TL signals were recorded at 800 nm following excitation into the high energy edge of the carotenoid S2 band at 400 nm. For the S2 lifetime solvent-independent upper limits on the order of 100-200 fs are estimated for all carotenoids studied. The S1 lifetimes are in the picosecond range and increase systematically with decreasing conjugation length. For instance, in the sequence canthaxanthin/echinenone/beta-carotene (13/12/11 double bonds) one finds tau1 approximately 5, 7.7 and 9 ps for the S1-->S0 IC process, respectively. Hydroxyl groups not attached to the conjugated system have no apparent influence on tau1, as observed for canthaxanthin/astaxanthin (tau1 approximately 5 ps in both cases). For all carotenoids studied, tau1 is found to be insensitive to the solvent polarity. This is particularly interesting in the case of echinenone, canthaxanthin and astaxanthin, because earlier measurements for other carbonyl carotenoids like, e.g., peridinin partly showed dramatic differences. The likely presence of an intramolecular charge transfer state in the excited state manifold of C40 carbonyl carotenoids, which is stabilized in polar solvents, has obviously no influence on the measured tau1.

Ultrafast photoinduced relaxation dynamics of the indoline dye D149 in organic solvents

“…Details of this setup can be found in previous publications, 23,24 and here we focus only on the specifics relevant for the current experiments: the output of a mode-locked Ti:sapphire oscillator (Spectra-Physics Tsunami, 80 MHz; pump source: SpectraPhysics Millenia Xs Nd:YVO 4 laser) generated red pulses at 755 nm with an average power of 1.2 W. The laser beam was split into two parts. One beam traversed an acousto-optic modulator (AOM, 2 MHz modulation frequency) with subsequent frequency-doubling in an LBO crystal, resulting in an intensity-modulated UV pump beam (377.5 nm, pulse energy o 0.1 nJ).…”

Self-assembly and energy transfer in artificial light-harvesting complexes of bacteriochlorophyll c with astaxanthin

“…Ilagan et al (2005) determined the S 1 state lifetime of astaxanthin in methanol, acetonitrile and carbon disulfide to be ~5ps, and the lifetime of S 2 state to be between 105 fs (methanol) and 165 fs (acetonitrile). Kopczynski et al (2005) also reported a lifetime of ~5ps for the S 1 state of astaxanthin in various solutions ranging from toluene to methanol and a lifetime of ≤120fs for S 2 state of astaxanthin in acetone and dimethyl sulfoxide. The S 2 state relaxation was also measured by photon echo spectroscopy for astaxanthin in THF and a lifetime of 160 fs was determined using the excitation pulses of ~30 fs width (Christensson et al 2009).…”

Interne S2→S1‐Konversion in β‐Carotin: starke vibronische Kopplung aus der Amplitudenoszillation transienter Absorptionsbanden

“…(8 AE 1) ps. [2] Basierend auf Experimenten mit stimulierter Raman-und transienter Absorption schlugen die Gruppen von Hashimoto [4] und Cerullo [5] einen konsekutiven zweistufigen Mechanismus vor, der die ultraschnelle Bildung und Zerfall eines 1 1 [7a] ¾hnliche Schlussfolgerungen wurden aus Experimenten mit stimulierter Raman-Spektroskopie, [8] transienter Fluoreszenzspektroskopie [9,10] und Transient-Lens-Spektroskopie [11] gezogen, wobei die zeitliche Auflösung aber geringer war. Deutlich weniger ist über die intermediären Zustände S°, [12] S T* [13] und S solv* [7] bekannt, denen eine maßgeb-liche Rolle für bestimmte Eigenschaften der transienten Absorption um 520 nm zugeschrieben wurde.…”