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Complexes are formed because of the donar acceptor mechanism. Donor is the neutral molecule or ion of non metallic substance that can donate the lone pair of electrons. Acceptor is the metallic ion or sometimes it might a neutral atom.

Complexes are of following types.

1) Metal ion complexes

2) Organic complexes

3) Inclusion compounds

Inorganic complexes, chelates, olefin complexes
and aromatic complexes are included in the metal ion complexes.

Quinhydrone complexes, picric acid complexes,
drug complexes and polymer complexes are included in the organic complexes.

Channel lattice complexes, layer type complexes, clatharates, mono and macro molecular complexes are included in the inclusion compounds.

Metal complexes

Inorganic complexes:

Here there will be a metal atom to which the ligands donate the lone pair of electrons. The general ligands are water, ammonia and cyanide molecules.

One point that we have to note is that during
the complex formation the lower energy levels like 3d and 4s will be filled earlier to the 4p.

Organic complexes:

The two components are attached by the weak donor acceptor forces. Sometimes the hydrogen bonds may be involved.

The distance in case of organic compounds will
be more and so the attraction energy will be less. So the separation of these compounds from the solution is not easy.

Quinhydrone complexes are formed when the alcohol solution of benzoquinone and alcoholic solution of the hydroquinone is mixed in equimolar concentration.

Picric acid complexes are formed when picric acid is treated with weak bases.

Polymeric complexes formed when the polymers have nucleophilic oxygen.

Inclusion complexes.

Channel type: The choleric acids form these type of complexes. The deoxycholeic acid molecules can form channels in which the molecules will get inside.

Layer type:The guest molecule get entrapped with in the layers.

Clatharates: It's a cage like
complex. And here there will be no formation of the chemical bonds.

Monomolecular complexes and macromolecular complexes are the inclusion compounds that are classified based on the number of the guest molecules that will get entrapped.


Martin's Physical Pharmacy and Pharmaceutical
sciences by Patrick J. Sinko, 5th edition, Lippincott Williams and wilkins publishers, page no 267 to 277.

"This blog does not contain any plagiarized material"


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Sho's picture

its good that you have given such an info over here, but when you are writing the article make sure that you give examples also.......pls do write examples of each complexes.....this will help students in future as they do not always carry book with them.....

ok sho thanks for the comment and in some cases i quoted the examples and i will take your suggestion
Satyajit Panda Asst. professor Maharajah's College Of Pharmacy