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N
N
N
N
O
O
O
O
O
O
Mg
Chlorophyll d
N
N
N
N
O
O
R
O
O
O
Mg
Chlorophyll a/b
N
N
N
N
O
OH
R
O
O
O
Mg
Chlorophyllide
N
H
N
N
N
H
O
OH
R
O
O
O
Pheophorbide
N
H
N
N
N
H
O
OH
R
O
Pyropheophorbide
N
N
N
N
O
O
R
O
O
O
Mg
O
H
13
2
-OH-chlorophyll
N
H
N
N
N
H
O
O
R
O
O
O
Pheophytin
N
H
N
N
N
H
O
O
R
O
Pyropheophytin
N
N
N
N
O
O
O
O
O
Mg
O
Chlorophyll f
Fig. 6.3 Chlorophylls structures containing the chlorin macrocycle present in phytoplankton
The second type of macrocycle are the chlorins, chemically defined as 17,18-transdihydrophytoporphyrin (Fig. 6.1), which means an unsaturated bond exists between
the C-17,18. Consequently, chlorophylls carrying a chlorin macrocycle typically
presents two maxima, around 440 and 660 nm, with similar absorbance (Table 6.6).
Chlorophylls a, b, d, and f (including their derivatives, Fig. 6.3) of oxygenic organisms as well as bacteriochlorophylls c, d, and e (Fig. 6.4) are formed with a chlorin