chemistry investigations

hi Ive been given the idea of doing a chemistry investigation on porphin ring systems, does anyone know anything about them or any suggestions on what I could do? Thanks,
Emma

Reply 1

oxymoron

Do you mean porphyrin ring systems?
(I haven't heard of porphin rings but it doesn't mean they don't exist)

Reply 2

horsecrazy

Yeah i meant porphyrin (oops)

Reply 3

oxymoron

Well - ideas for chemistry investigations don't immediately come to mind, but do you know what they are?

This site is good:
http://www.washburn.edu/cas/chemistry/sleung/porphyrin/porphyrin_page.html

The most important use of them I can think of though is in Haemoglobin and Myoglobin (oxygen carrying proteins in animals). The prosthetic group in these is a porphyrin ring system with an Fe2+ ion in the middle (it is this that carries the oxygen).

Did your teacher give you any ideas on what to do?

Reply 4

idiopathic

I've never heard of porphyrin, seems interesting though.
just looked it up now - haemoglobin works like an octahedral Fe ion complex, with the N and H2O/O2 acting as ligands:

http://www.chemguide.co.uk/inorganic/complexions/whatis.html

Reply 5

oxymoron

yes, but the 4 planar N atoms marked there are all linked by an aromatic ring system as well, and the top N is part of the protein (from a histidine amino acid side chain).

And I think the porphyrin system is just the ring system containing the 4 Nitrogens ... but it can have an Fe2+ ion put in the middle (and then the N's act as ligands) as it does in Haemoglobin

Reply 6

idiopathic

oops I see now. so in a complex like [Cu(H2O)6] , how are the 4 planar ligands linked together, if they are?

Reply 7

oxymoron

No, here the water molecules are not linked together, but this is NOT a porphyrin. This is just a simple octahedral complex with 6 waters acting as ligands around the central Cu2+ ion.

If you like, think of the porphyrin ring as a polydentate ligand (ie one molecule that can act as a ligand at many points). In fact the porphyrin can bind datively using any of its 4 nitrogen lone pairs (as it does), but H20 on the other hand is a monodentate ligand that can only make one bond in a complex.