Excitation energy relaxation in model aggregates of photosynthetic pigments upon picosecond laser excitation

Deactivation of Excited States in Nanostructures Containing Cu-Porphyrin Subunit

“…We have shown that a small amount of bifunctional linker molecule (like dioxane) plays the directed role in the formation of stable polymeric ordered aggregates of photosynthetic pigments (chlorophylls a and b, protochlorophyll or bacteriochlorophyll) being previously dissolved in solvents with poor solubility (such as water or 3-methylpentane). [85][86][87][88] The size and the morphology of these aggregates and their spectroscopic properties (polarized fluorescence and high optical activity) depend strongly on the linker molecule, concentration, ratio of the solvent mixture and temperature. [87][88][89] In binary mixture of solvents we realized conditions where the formation of mixed aggregates of different molecules but having the general structural elements, was thermodynamically more preferable.…”

“…[85][86][87][88] The two oxygen atoms of the dioxane molecule are able to link two Chl a (or PChl a) molecules by coordinating to the central magnesium atoms of the tetrapyrrolic macrocycles with center-to-center distance R≈7 Å (Figures 7A and 7D). Due to the molecular structure of dioxane, other types of bonding are not possible.…”

“…dioxane solutions at 293 K (4 in Figure 7C) reflects the high ordering of interacting p-conjugated macrocycles in these arrays. The circular dichroism (CD) signal (3 in Figure 7C) is strong (by two order of magnitude with respect to that for monomers [85][86][87][88] ) and the sign sequence follows that of the polarization spectrum. y-Type effect in CD spectra (splitting into two components of the opposite sign) of these aggregates reflects the long-range interactions within the sizable aggregate frame.…”