The structure of the aggregate form of bacteriochlorophyll c showing the Qy absorption above 740 nm: a 1H-NMR study

Bacteriochlorophyll c (3 1S, 8-isobutyl-12-ethyl, farnesyl) was dissolved in a mixture of methylene chloride and carbon tetrachloride (1 : 3), and changes in the 1H-NMR spectrum caused by the titration of methanol were traced. On the basis of the changes in chemical shift due to the ring-current effect of the neighboring macrocycles and in peak intensity (broadening) due to their stacking, the structure of the aggregate form showing the Qy absorption band above 740 nm is proposed: the macrocycles are stacked to form a one-dimensional inclined column, the y axis of each macrocycle being parallel to the long axis of the column.