The document provides information about Schiff bases: - Schiff bases are organic compounds formed by the condensation of carbonyl compounds with primary amines, first reported in 1864. - There are several methods for synthesizing Schiff bases, including microwave, reflux, stirring, and grinding methods. Spectroscopic techniques like FT-IR, UV-Vis, and X-ray spectroscopy are used to characterize Schiff bases and their complexes. - Schiff bases have applications in coordination chemistry and as intermediates in organic synthesis. They also show biological activities like antimicrobial and anticancer properties.

1. Wael AL-HARBI
Schiff base
complexes and application

2. Contents
Introduction
SYNTHESIS
MECHANISMS
Spectroscopic properties
Applications
References

3. INTRODUCTION
Schiff bases constitute one of the most widely used families of organic
compounds not only as synthetic intermediates but also in
coordination chemistry and their chemistry is essential material in
organic textbooks[1].
Schiff bases (also known as imine or azomethine), named after Hugo
Schiff, was reported in the 19th century by Schiff(1864). Since then a
variety of methods for the synthesis of imines have been described.
The classical synthesis is when any primary amine condenses with a
carbonyl compound[2].

4. INTRODUCTION
Who was Schiff ?
1834 1848 1849 1857 1863 1915
Born in the vibrant Jewish
community in Frankfurt/
Main, Germany
Revolutions these
were tumultuous
times in Europe
Moved to London from Germany.
Jailed. Because of his “rather
advanced political views”.
He emigrated to
Switzerland
He moved to Italy
where his brother
Moritz Schiff
Spent his long career in Italy
and continued teaching until
1915, the year of his death
[3]

5. INTRODUCTION
In Italy Schiff first obtained a position in
Pisa, where in 1864 he studied the reaction
of aniline with aldehydes, including
acetaldehyde, valeraldehyde,
benzaldehyde, and cinnamaldehyde.
The first brief paper was entitled
“A New Series of Organic Bases” [3].

6. INTRODUCTION
Schiff base compounds have an azomethine group (-CH=N-) which are
made by the condensation of carbonyl compounds with a primary
amine [2].
But the Schiff base compounds that are prepared from aromatic
aldehydes and aromatic amines are more stable and more effective [2].

7. INTRODUCTION
The azomethane group (CH = N-) appears to be one of the reasons for
making many types of base-base compounds of great importance in
large areas of industrial applications and biological activities such as
antimicrobial, antifungal, anticancer, antiviral, antioxidants, anti-
inflammatory, antiparasitic, antioxidants and more in industrial and
auricular chemistry [4].
These biological activities can be altered depending upon the types of
substituents attached to the aromatic rings [5].
One of the most important alternatives is the hydroxyl group (OH).

8. INTRODUCTION
Schiff bases containing hydroxyl group on different positions got a great
interest because they have pharmacological activities for example anti-
bacterial, anti-cancer and anti-oxidants.
The Schiff base compounds, which contain a hydroxyl group in ortho,
have two forms: Keto (N–H…O) and Enol (O–H…N) [6].

9. INTRODUCTION
Of compounds known to the Schiff base containing a hydroxyl group
salen and salophen.
Although the Schiff bases are
known to be good chelating
agents, and easily prepared and
characterized, little interest has
been given to their uses for
analytical purposes because of
two serious drawbacks
They are insoluble in aqueous solutions but soluble in most organic solvents
They decompose easily in acidic solutions [7]

10. INTRODUCTION
Schiff bases usually contain N, O and S donor atoms and may act as
ligands. They are able to coordinate with many metals to stabilize their
various oxidation states in such a way that a five or six membered
chelate ring can be formed [8].
Schiff base ligands are easily synthesized and form complexes with
almost all metal ions.
Schiff bases and their metal complexes have been found to be
biological active in the view of antibiotic, antimicrobial, antifungal and
antitumor properties [8].

11. SYNTHESIS
Four common methods that vary in reaction time, product, and
percentage yield have been reported for the synthesis of Schiff bases.
These methods include:
Microwave
method
Stirring
method
Grindstone
method
Reflux
method

12. SYNTHESIS
Four common methods that vary in reaction time, product, and
percentage yield have been reported for the synthesis of Schiff bases.
These methods include:
Microwave method
Stirring method
Grindstone method
Reflux method
This method is temperature controlled method. Used to reduce reaction
time and give high yield.

13. SYNTHESIS
Four common methods that vary in reaction time, product, and
percentage yield have been reported for the synthesis of Schiff bases.
These methods include:
Microwave method
Stirring method
Grindstone method
Reflux method
This is Green method of synthesis of Schiff bases. This is newly Developed
process

14. SYNTHESIS
Four common methods that vary in reaction time, product, and
percentage yield have been reported for the synthesis of Schiff bases.
These methods include:
Microwave method
Stirring method
Grindstone method
Reflux method
This is conventional method for the preparation of Schiff bases. This Process
gives the best yield and easy to form the product.

15. SYNTHESIS
Four common methods that vary in reaction time, product, and
percentage yield have been reported for the synthesis of Schiff bases.
These methods include:
Microwave method
Stirring method
Grindstone method
Reflux method This is conventional method for the formation of Schiff base ligand

16. SYNTHESIS
O H
C l
N H 2
N H 2
N
C l
H 2 N
E t h a n o l
Time
Yield
Reaction condition
Way
8 min
80.04%
Microwave Irradiation
1
8 h
68.34%
Reflux
2
5 h
75.12%
Stirring
3
20 min
67.05%
Grinding
4
[9]

17. SYNTHESIS
R
Scheme
Synthesis
Title
10
A solution of FeCl3·5H2O (1 mmol) in 20 mL
of ethanol was added dropwise to a
solution of the ligand L2 (0.386 g, 1 mmol)
in 20 mL of ethanol with stirring.
Non-enolisable
Knoevenagel condensate
appended Schiff bases-
metal (II) complexes:
Spectral characteristics,
DNA-binding and
nuclease activities
11
The following general procedure was
applied in the synthesis of complexes [NiL]
and [CuL]. 1 mmol of tetradentate Schiff
base ligand dissolved in methanol (10 mL)
was added to 1 mmol of acetate salt
dissolved in 10 mL of a methanol. The
resulting mixture was stirred at reflux for 2
h.
Synthesis and electronic
structure of novel Schiff
bases Ni/Cu (II)
complexes: Evaluation of
DNA/serum protein
binding by spectroscopic
studies

18. SYNTHESIS
R
Scheme
Synthesis
Title
12
The La(III)/Th(IV) nitrate and
vanadyl sulphate (4.3/5.7/1.81 g,
0.01 mol) in super-dry alcohol (10
mL) were treated with Shciff
bases (4.8/4.3 g, 0.01 mol) in super-
dry alcohol (40 mL). The reaction
mixture was refluxed for 4–5 h.
Synthesis, characterization, DNA
cleavage and in vitro antimicrobial
studies of
La(III), Th(IV) and VO(IV)
complexes with Schiff bases of
coumarin derivatives

19. MECHANISMS
R
C
R
O
NH2
R C R
O
R
N
H
R
H
C R
OH
R
N
R
H
Base catalyzed
OH
C
N
R
R
R
Acid catalyzed H
C R
OH2
R
N
R
H
C
N
R
R
R
H
H2O
C
N
R
R
R
H2O

20. Spectroscopic properties
FT-IR Spectra
There are some functional groups that can be distinguished by absorption using the
IR spectrum.
One of the most important functional groups that can be distinguished in Schiff
base compounds
v(C=C) 1600-1580 cm-1
v(OH) 3400-3200 cm-1
v(C-O) 1100-1300 cm-1
v(C=N) 1610-1625 cm-1
[6]

21. Spectroscopic properties
FT-IR Spectra
It is observed that when Schiff base compounds are associated with
metals, displacement of the absorption values occurs.
New tetradentate Schiff bases of 2-amino-3,5-dibromobenzaldehyde
with aliphatic diamines and their metal complexes: Synthesis,
characterization and thermal stability
Complexe
Schiff base
Compound
C=N
C=C
C=N
C=C
1458
1610
1627
1400-1500
L1
1604
1462
1633
1400-1500
L2
1605
1457
1632
1420-1500
L3
[13]

22. Spectroscopic properties
FT-IR Spectra
Synthesis, Characterization and Biological Studies of Metal(II)
Complexes of (3E)-3-[(2-{(E)-[1-(2,4-Dihydroxyphenyl)
ethylidene]amino}ethyl)imino]-1-phenylbutan-1-one Schiff Base
Schiff base
Compound
C-O
C=N
C=C
1241-1288
1605
1470-1543
DEPH2
1240-1287
1601
1469-1542
[Zn(DEP)].2H2O
1180-1240
1592
1483-1515
[Cu(DEP)].2H2O
1180-1240
1597
1485-11516
[Ni(DEP)].3H2O
[14]

23. Spectroscopic properties
UV-Vis Spectra
In the UV-visible spectra of schiff base, Mostly the wavelength 200–
400 nm is due to the π→π* and n→π* transition.
In the UV-visible spectra of salicylaldimine and naphthaldimine
derivatives, four main bands are to be expected in the 200–400 nm ;
namely the first (210–234 nm) and second (240–282 nm) bands are
attributed to the π → π* transitions of aromatic rings. The third band at
300–340 nm is assigned to the π → π* transitions of C=N group. The
forth band at >400 nm involves n → π* transitions of C=O group [13]

24. Spectroscopic properties
UV-Vis Spectra
In the Schiff base complex, Beck's appearance is observed in the
wavelength area> 400 depending on the type of metal bonded.
Substitution of PPh3+ as a lipophilic cation on new water-
soluble Co(II)and Zn(II) Schiff base complexes: Effect of
central metal and substitutional group of ligand on DNA-
complex interaction
Wavelength {nm)
Compound
333, 387
L
268, 382
1
268, 460
2
265, 380
3
265, 464
4
[15]

25. Spectroscopic properties
UV-Vis Spectra
In the Schiff base complex, Beck's appearance is observed in the
wavelength area> 400 depending on the type of metal bonded
New tetradentate Schiff bases of 2-amino-3,5-dibromobenzaldehyde
with aliphatic diamines and their metal complexes: Synthesis,
characterization and thermal stability
Complexes
Compound
Schiff base
Compound
484. 535 nm
[NiL1](OAc)2
364 nm
L1
473 nm
[NiL2](OAc)2
362 nm
L2
497 nm
[NiL3](OAc)2
363 nm
L3
[13]

26. Spectroscopic properties
X-ray Spectra
Is a method to find out : Order of atoms with in crystals
Determine the size of the atoms
Types and length of chemical bonds
The differences between many
materials at the atomic level
(especially metals and ligands)

27. Spectroscopic properties
X-ray Spectra
1
2
3
4
[16]

28. Spectroscopic properties
X-ray Spectra
1
2
3
4
Compounds 1, 2, 3 and 4 crystallize in the
monoclinic.
Each of the molecules were found in the
enolimine form.
The crystal structures of 1, 2, 3 and 4 are
stabilized by two intramolecular hydrogen
bonds of the O–H…N .
The crystal structures of 1, 2, 3 and 4 form
weak 𝜋 … 𝜋 stacking interactions between the
aryl rings [16]

29. Spectroscopic properties
X-ray Spectra
3
In a compound 3 H–bonds are formed between
the oxygen atom of the SO2 group and the
hydrogen atom of one of the spacer phenylene
rings of a further molecule .
As a result of these intermolecular interactions,
polymeric chains are formed .
[16]

30. Spectroscopic properties
X-ray Spectra
1 2
3
4
[16]
Indicates
4
3
2
1
Compounds
single bonds
1.342(3)-1.342(3)
C-O
1.413(3)-1.456(5)
(N=)C-C (aryl)
double bond
1.259(5)-1.302(3)
(aryl)C=N
sp2-hybridization
of the nitrogen
atoms
120.0(2)-122.22(19)
C-N=C

31. Spectroscopic properties
X-ray Spectra
The molecules of 2, 3 and 4 contain two N-
salicylidene aniline derivatives linked by an
oxygen atom, sulfur atom or sulfone group with the
dihedral angles for:
Compound 2 : C6H4–O–C6H4 53.72(8)
Compound 3 : C6H4–(O=)S(=O)–C6H4 80.66(10)
Compound 4 : C6H4–S–C6H4 73.63(10)
[16]

32. Spectroscopic properties
X-ray Spectra
Molecules of 2, 3and 4 are
stacked in the crystal
However, in 3 each of the N-salicylidene
aniline residues of a molecule are packed
almost perpendicularly to two
N-salicylidene aniline derivatives of a
further molecule
[16]
3

33. Spectroscopic properties
X-ray Spectra
whereas in 2 and 4 N-salicylidene aniline
residues of a molecule are parallel
[16]
4
2

34. Spectroscopic properties
X-ray Spectra

35. Spectroscopic properties
X-ray Spectra
1 2

36. Spectroscopic properties
X-ray Spectra
1
The asymmetric unit of compound 1
contains one half of the molecule
The phosphazene ring
(P1/N1/P2/N2/P3/N3)
The six-membered rings
(P1/N7/O1/C1/C6/C7)

37. Spectroscopic properties
X-ray Spectra
1
The phosphazene ring
(P1/N1/P2/N2/P3/N3)
θ2 = 123.3(1.8)°
twisted-boat conformation

38. Spectroscopic properties
X-ray Spectra
1
The six-membered rings
(P1/N7/O1/C1/C6/C7)
θ2 = 89.39(13)°
boat conformations

39. Spectroscopic properties
X-ray Spectra
2
The phosphazene ring
(P1/N1/P2/N2/P3/N3)
and
(P4/N4/P5/N5/P6/N6)
The six-membered rings
(P1/N7/O1/C1/C6/C7)
and
(P4/N8/O2/C21/C22/C23)

40. Spectroscopic properties
X-ray Spectra
2
The phosphazene ring
(P1/N1/P2/N2/P3/N3)
θ2 =93.4(1.1)°
twisted-boat conformations
(P4/N4/P5/N5/P6/N6)
θ2 = 89.4(1)°
boat conformations

41. Spectroscopic properties
X-ray Spectra
2
The six-membered rings
(P1/N7/O1/C1/C6/C7)
θ2 = 89.39(13)°
flattened-boat conformations
(P4/N8/O2/C21/C22/C23)
θ2 =144.23(49)°
boat conformations

42. Spectroscopic properties
X-ray Spectra

43. APPLICATIONS
Biologically active
A series of Schiff base derivatives were synthesized and analyzed as
novel antioxidants and anti-inflammatory agents [17].
[17]

44. APPLICATIONS
The in vitro antioxidant activities of these compounds were
evaluated and compared with those of commercial antioxidants:
ascorbic acid, gallic acid, butylated hydroxytoluene and butylated
hydroxy anisole (BHA) employing 1,1-diphyenyl-2-picrylhydrazyl
(DPPH) assay.
The results
1-revealed that IC50 values of compounds were lower than those of
standards in all three performed antioxidant assays indicating good
activities of these compounds.
2-That the compounds with electron-donating moiety (OH, OCH3)
were found to be excellent antioxidants.
3-That the compounds with electron-withdrawing moiety (Cl, NO2)
were found to be excellent anti-inflammatory agents.
[17]

45. APPLICATIONS
Catalysis
Schiff bases are artificial and are used to form many important
catalysts, such as Jacobsen's catalyst.
One of the uses of this catalyst
is preparation of epoxidation

46. APPLICATIONS
[18]

47. REFERENCES
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Dihydroxyphenyl)ethylidene]amino}ethyl)imino]-1-phenylbutan-1-one Schiff Base. 2015:9788-9802.
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