Effects of Self-Assembled Aggregation on Excited States - Carotenoids: Physical, Chemical, and Biological Functions and Properties - page 146

Table 8.1
Absorption Maxima of Some Carotenoid Aggregates a

Carotenoid Solvent l max (M) l max (H) l max (J) Reference

ACOA b Ethanol 440 390 (1:4) T. Polívka (unpublished)

ACOA TiO 2 i lm 426 Gao et al. (2000)

ACOA TiO 2 i lm 400 Pan et al. (2004)

Astaxanthin Acetone 478 450 (1:9) 562 (3:7) Köpsel et al. (2005)

Astaxanthin Acetone 478 403 (1:9) 560 (1:9) c Mori et al. (1996)

Astaxanthin Ethanol 476 410 (1:9) d Buchwald et al. (1968)

Antheraxanthin Ethanol 447 375 (1:3) Ruban et al. (1993)

Acetone 455 420 (1:3) 515 (1:3) Zsila et al. (2001d)

β-Carotene

TX-100 micelles 505 Avital et al. (2006)

β-Carotene

Capsanthol Ethanol 447 385 (1:3) e 504 (1:3) f Zsila et al. (2001e)

Lutein Acetone 449 370 (4:15) Zsila et al. (2001b)

Lutein Ethanol 445 Ruban et al. (1993)

370 (∼1:1)

Lutein Thin i lm 380 Zsila et al. (2001b)

Lutein Lipid bilayer 370 Sujak et al. (2002)

Lycopene THF 480 354 (1:5) Wang et al. (2005)

Lycopene Ethanol 480 380 (1:4) 580 (1:4) Ray and Mishra (1997)

Lycopene LB i lm 348 563 Ray and Mishra (1997)

Spirilloxanthin Acetone/MetOH 496 374 (1:2) Agalidis et al. (1999)

Violaxanthin Ethanol 440 Ruban et al. (1993)

390 (∼1:1) 500 ( ∼ 1:1)

Violaxanthin TX-100 micelles 390 515 Avital et al. (2006)

Zeaxanthin Acetone 390 (3:7) 517 (1:1) Avital et al. (2006)

Zeaxanthin Methanol 450 387 (1:4) 530 (3:2) Billsten et al. (2005)

Zeaxanthin Ethanol 450 Ruban et al. (1993)

380 (∼1:1)

Zeaxanthin TX-100 micelles 380 g 520 Avital et al. (2006)

λ max refers to absorption maximum of monomers (M), H-aggregates (H), and J-aggregates (J); values in bold indicate
that a J-aggregate is present in the sample together with an H-aggregate; solvent:water ratio is shown in parentheses.

a

8′-apo-β-carotenoic acid.

b

At a higher temperature after several hours.

c

In presence of 3 M sodium perchlorate.

d

Position of the band varies with concentration (382-394 nm).

e

J-aggregate was formed for 6′S capsanthol while H-aggregate for 6′R capsanthol.

Formed from a J-aggregate after 2 h.

g

of H-aggregates caused by the increased water content. Since 3:2 ethanol/water ratio is close to
the limit of H-aggregate formation, a large distribution of aggregate sizes is likely present in the
sample. The narrowing of the H-band is caused by the delocalization of excitons in the aggregate.
For individual carotenoid molecules, the spectral width of the absorption band is determined by
disorder in the transition energy. However, upon aggregation, excitons are delocalized over sev-
eral molecules; this results in an averaging over the energetic disorder of the individual molecules,
thereby decreasing the width of the spectral band (exchange narrowing) (Ohta et al. 2001). Thus, a
narrower H-band rel ects an increase in the average number of molecules in the H-aggregate.
Increasing the initial concentration of zeaxanthin to 10 −4 M, Figure 8.6b, produces a differ-
ent dependence on the ethanol/water ratio. Under these initial conditions, adding water to a i nal
ethanol/water ratio of 3:2 leads to a distinctly different absorption spectrum than that observed at
lower initial concentration. The vibrational structure of the S 2 state is preserved and a new absorp-
tion band characteristic of J-aggregates appears at 530 nm. When the water content was increased