Metallation of the Free-Base Porphyrin
The iron porphyrin is conveniently prepared from the free-base porphyrin by a
scaled-down, modified version of the procedure reported by Adler et al.10.
The progress of the reaction is conveniently
monitored by checking the reaction
medium for fluorescence. Dilute solutions
(these must be sufficiently diluted or the
residual fluorescence can be missed!!) of
the free-base (i.e., metal free) porphyrins
fluoresce brightly red when irradiated with
long-wave UV light in a darkened room,
whereas the metallated porphyrins do not.
Procedure for the synthesis of an iron-porphyrin complex Fe(porph)Cl
In a 250-mL three-neck, round-bottom flask equipped with a reflux condenser, a
stirred mixture of 1 g of free-base porphyrin in 100-mL dimethylflormamide, DMF, is
brought to a reflux. About 0.5 g of FeCl2 is added over a 5-min period, and the solution
is allowed to reflux for 10 min. Caution! The addition of FeCl2 to the reaction medium
is accompanied with the evolution of heat. The FeCl2 must be added in small increments.
If an examination of the reaction medium reveals fluorescence, additional FeCl2 is added
and the reaction mixture refluxed for an additional 10 min. The DMF solution is cooled
to room temperature and an equal volume of water added along with 1 mL of 6 M HCl.
The mixture is chilled in an ice bath and suction filtered. The dark brown-purple solid is
washed with water until the filtrate is colorless and aspirated to dryness. Typically,
isolated yields are greater than 90%. WASTE DISPOSAL: The initial filtrate should
go in the metal containing waste container in the hood. The subsequent water
washings may go down the sink with plenty of water.