  A molecular modeling study was conducted on a series of six natural occurring
chlorophylls. Quantum chemistry calculated orbital energies were used to
estimate frequency of transitions between occupied molecular orbital and
unoccupied molecular orbital energy levels of chlorophyll molecules in vivo
conditions in standard (ASTMG173) environmental conditions. Obtained results
are in good agreement with energies necessary to fix the Magnesium atom by
chlorophyll molecules and with occurrence of chlorophylls in living vegetal
organisms.
