The document discusses the concepts of complexation in physical pharmaceutics, focusing on types of ligands (unidentate, bidentate, tridentate, hexadentate) and their roles in forming complexes with metal ions. Various examples are provided, including the use of EDTA and specific drugs like procainamide and vitamin B12, as well as the significance of aromatic and inclusion complexes. Additionally, it highlights the importance of these complexes in drug stability and bioactivity.

1. Physical Pharmaceutics-I
Unit-IV

2. Complexation
Classical bonding theory – It includes:-
Covalent bonds
Vander wall forces
Dipole dipole
interaction
Hydrogen bond
Co-ordinate bond

4. Classification

5. Compound like ammonia which has a single pair of electrons for bonding
with metal ion is called unidentate ligand.
Ligand with two or three groups known as bidentate or tridentate ligand
respectively. EDTA has 6 points for attachment and called hexadentate ligand.

6. They have metal at Central and accept electron from ligand through coordination
bond. It is used to analyse chemical composition through colorimetric analysis.
Compound like ammonia which has a single pair of electrons for bonding with metal
ion is called
unidentate ligand.
Ligand with two or three groups known as bidentate or tridentate ligand respectively. EDTA has
6 points for attachment and called hexadentate ligand
1. Inorganic metal complex

8. • EDTA is used for removing di and trivalent forms
of
water.
• Procainamide is subjected to make complex with
cupric ions at pH4 for its assay.
• Vitamin B12 contains metal cobalt that is bound to a
porphyrin like chelating agent.
• EDTA, citrates, oxalates are used as anticoagulant.

9. • Aqueous solution of some metal ion absorb ethylene
moiety present in ligand and form water soluble
compound or complex.
• Used as catalyst for manufacturing of drugs, intermediate
and in analysis of drugs.
• Platinum, Mercury, iron, silver are pronounced examples
of olefins complex
• These complexes can be mono-olefin, di-olefin or non-
conjugated di-olefin.
3. Olefin complex

10. 4. Aromatic complexes
Eg: 1. Complex of toluene with hydrochloric acid is example
of pi bond complex
2. Complex of transition metal with aromatic compounds
such as ferrocene forms a complex which is an example of
sandwich complex

12. Drug such as benzocaine, tetracaine and procaine these are less stable
that's why they are complexed with caffeine which enhances their
stability.
Eg: Caffeine forms complex with gentisic acid ligand that masks the
bitter taste of drug in chewable tablets.

14. • Picric acid forms complex with strong bases (drugs). It makes
complex with butesin picrate that is very important ointment
applied on burnt and painful skin injuries.
• Picric acid is very important complexing agent because it makes
stable and more bioactive complexes with carcinogenic

16. 3. Inclusion Complexes

17. a) Channel lattice
The host component forms and channel like structure in which guest
molecules gets fit. Mostly channels are found by crystallization of
host molecule where long, unbranched chain molecule gets entrapped.
Eg: Dissolution of vitamin E and famotidine can be
improved by channel lattice complex

18. b) Layer type
They are also known as intercalation
compounds.
Ex- some compounds such as bentonite can
entrap hydrocarbon, alcohol, glycols
between their layer lattices.

19. c) Clathrates
• These are cage like structure in which guest molecules is entrapped.
• Chemical bonds are not involved in these kind of structure and
molecular size of guest molecule is very less.
Ex- Hydroquinone crystallizes as cage like structure and
allow and treatment of carbon dioxide and hydrochloric
acid.

20. d. Mono molecular compounds
Eg: Cyclodextrin show cyclic structure where drug can be complexed
to form monomolecular compound.