Structure investigations on assembled astaxanthin molecules

Excited-state dynamics of astaxanthin aggregates

“…H-aggregate of astaxanthin prepared in hydrated methanol peaks at 388 nm [22], thus essentially at the same wavelength as we observed in hydrated DMSO even though absorption spectrum of astaxanthin monomer in DMSO is red-shifted by nearly 30 nm. The same is observed for J-aggregates; the 0-0 band was reported at 560 [20] and 562 nm [21] in hydrated acetone, and around 570 nm in hydrated methanol [22] and DMSO ( Figure 1). The absence of solvent polarizability-related red shift in aggregates is caused by the size of the aggregates; the aggregates are large, thus majority of molecules is buried inside the aggregate and not exposed to solvent, resulting in observed absence of the solventdependent shift of absorption spectrum.…”

“…The absorption spectrum of the monomer has a maximum at 504 nm and does not exhibit any vibrational structure. Due to dispersion interactions, the maximum of the S 0 -S 2 transition of astaxanthin in DMSO is significantly redshifted compared to the absorption spectra measured in methanol or acetone that peak around 476 nm [19,21,22]. A comparable S 0 -S 2 maximum, 506 nm, was reported for astaxanthin in the nonpolar but highly polarizable CS 2 [25].…”

“…Upon binding to crustacyanin, absorption spectrum of astaxanthin undergoes a large red shift whose origin is still a matter of debate and excitonic interaction due to aggregation has been also suggested to contribute to the red shift [18]. Aggregates of astaxanthin were so far studied only by steady-state spectroscopies that described formation of both H-and J-type aggregates in various hydrated solvents [19][20][21][22][23]. Here we employ transient absorption spectroscopy to reveal aggregation-induced changes of excited-state dynamics of astaxanthin.…”

Mobile phase additives for enhancing the chromatographic performance of astaxanthin on nonendcapped polymeric C30‐bonded stationary phases

“…Because the peak area response with no additive without a column exceeded that one with a C 30 column, on-column degradation of AST is likely. Results of spectrometry indicate that the variation of peak area response cannot be explained by the formation of supramolecular assemblies with different spectral properties [47,48]. Hence variation of peak area response is supposed to be based on degradation, potentially increased by heavy metal impurities.…”

Molecular Properties of Astaxanthin in Water/Ethanol Solutions from Computer Simulations

“…In particular, spectroscopic analysis have shown that their absorption spectra can be blue shifted as well as red shifted compared to that of the isolated monomers depending on the aggregation conditions. 7,8,[12][13][14] The blue shift is attributed to the formation of H-aggregates and the red shift is attributed to the formation of J-aggregates. The H-aggregates formed by these molecules when deposited on surfaces or arranged at interfaces, hold promise as photoactive species in dye-sensitized solar cells.…”