Shown here is the structure of monovinyl chlorophyll a (C56H72O5N4Mg), the most common of the several chlorophyll species. Closely-related compounds are chlorophyll b (chl a:chl b = 3:1 in green algae and higher plants), chlorophyll c (diatoms and brown algae), and chlorophyll d (marine red algae), as well as bacteriochlorophyll a and b and chlorobium chlorophyll.
Govindjee and G. Papageorgiou. 1992. “Chlorophyll” 3:581-584. McGraw-Hill Encyc. of Sci. and Technol. (7th ed).