The document summarizes a research presentation on the synthesis and characterization of new zinc, copper, and nickel complexes based on an imine ligand containing a 2-aminothiophenol moiety. Specifically, it describes the synthesis of a tridentate Schiff base ligand and its dimeric complexes with zinc, copper, and nickel ions. It then discusses the various techniques used to characterize the ligand and complexes, including IR spectroscopy, UV-Vis spectroscopy, NMR spectroscopy, conductivity measurements, computational modeling, and X-ray crystallography. The key findings are that the complexes were stable in solid and solution states, with the ligand acting as a tridentate chelating agent, and DFT calculations provided insights into their frontier

1. Welcome
to my Presentation

2. Research Paper Presented By
Ariful Islam
Roll No: 2053506
Presented to
Dr. Md Mizanur Rahman Badal
Professor
Department of Chemistry
Khulna University of Engineering & Technology
Khulna-9203,Bangladesh

3. Synthesis, characterization, spectroscopic
and theoretical studies of new
zinc(II), copper(II) and nickel(II)
complexes based on imine ligand
containing 2-
aminothiophenol moiety.
Presentation On

5. Schiff base ligands have significant importance in the development of
Schiff base complexes, because Schiff base ligands are potentially
capable of forming stable complexes with metal ions.
Schiff base ligands with sulfur and nitrogen donor atoms in
their structures act as good chelating agents for metal ions.
Coordination of such compounds with metal ions, like copper,
nickel and zinc, can enhance their biological activities.
Introduction

6. Dinuclear transition metal complexes of Schiff base ligands have many
applications such as antibacterial, antiviral and antifungal agents.
Schiff bases are potential anticancer drugs and the anticancer activity of
their metal complexes can enhance in comparison to the free ligand.

7. Schiff base complexes of zinc have application as a fluorescent emitters and
active layers in organic light-emitting diodes (OLEDs)

8. In this paper, we will see the synthesis of a new tridentate Schiff base ligand containing
2-aminothiophenol and its new dimeric complexes.
This tridentate Schiff base ligand was coordinated to the metal ions through the NSO
donor atoms.

9. The Schiff base and its complexes were characterized by :
IR spectra were measured as KBr pellets on a Perkin-Elmer spectrum.
Electronic spectra of DMSO solutions of compounds were measured on an Analytik Jena Specord
205 spectrophotometer.
Fluorescence spectra were recorded on FP-6200 spectrofluorometer.
Elemental analysis was performed using an elementar vario EL III.
H NMR spectra were obtained on a on a Bruker Avance DPX 500 MHz spectrophotometer in
CDCl3 as a solvent with tetramethylsilane as an internal reference.
Melting points were determined on a Barnstead Electrothermal 9100.
Conductivity was measured in DMSO solution (3×10-4 M) using a 712 conductometer (Metrohm).
Experimental

10. The oxidized form of Schiff base was also
characterized by X-ray crystallography.
The X-ray diffraction measurements were made
on a Single Crystal X-Ray Diffractometer
STOE IPDS-2T with graphite monochromated
Mo-Kα radiation.
The atomic factors were taken from the
International Tables for X-ray Crystallography.
Crystal structure determination and refinement

11. A solution of 2-hydroxy-
5-methyl benzaldehyde
(0.649 g, 5.18 millimol)
in 7 mL of absolute
ethanol.
2-aminothiophenol (0.706
g, 5.18 mmol) in 7 mL of
absolute ethanol.
Solution A were
slowly added to
the Solution B
A
B
Under 60 °C
temp.
Synthesis of tridentate Schiff base ligand, H2L

12. The mixture stirred for 8 hours in 80 °C under an inert atmosphere of argon.
After removal of the solvent, the yellow precipitate was obtained and washed with n-hexane.Then,
the product was dried in vacuo at room temperature.
N.B: Inert atmosphere use in order to prevent the oxidation of the thiole group
Melting point: 175 ºC
[C14H13NOS] (H2L)
Moleculer weight: 243.23

13. A solution of Zn(OAc)2
(0.045 g, 0.205 mmol) in
ethanol (solution A)
A solution (5 mL) of Schiff
base H2L (0.050 g, 0.205
mmol). (Solution B)
Solution A were
added dropwise to
the Solution B
Under 60 °C
temp.
Synthesis of zinc dimer complex
A
B

14. The mixture was heated with stirring on a
water bath at 80 °C for 8 hours.
The yellow solution of complex was left to stand for a night.
A pale yellow precipitate was obtained and washed with cold ethanol and then dried in vacuo at
room temperature.
m.p: 343 ºC, [C28H22N2Zn2O2S2] (Zn2L2):(M.W: 613.376)

15. Synthesis of copper dimer complex, Cu2L2
Copper acetate monohydrate (0.073 g, 0.360 mmol) in ethanol was added dropwise to a solution (5
mL) of Schiff base H2L (0.090 g, 0.360 mmol).
The mixture was heated with stirring on a water bath at 68 °C for 8 hours.
The resulting brown solution was evaporated and the brown precipitate product was collected and
washed with cold ethanol.
A brown solid was obtained.
m.p:> 200 ºC (decomp.)
[C28H22N2Cu2O2S2].H2O(Cu2L2)
M.W: 627.723

16. Synthesis of nickel dimer complex, Ni2L2
This complex was synthesized in the same manner as zinc or copper complex, except that
an ethanolic solution of Ni(OAc)2.4H2O (0.076 g, 0.307 mmol) was used and heated on a water
bath at 57 °C for 6 hours.
m.p: 234 ºC
[C28H22N2Ni2O2S2].4H2O(Ni2L2)
(M.W: 672.062)

17. Computational method
In addition to experimental studies,they
described density functional theory (DFT)
calculations for the three new zinc, copper and
nickel complexes.
This is a very useful tool for structural
identification of the complexes.
All calculations were performed using DFT
at the B3LYP/6-31G(d,p) level of theory as
implemented in the GAMESS program suite.
The highest occupied molecular orbital
(HOMO) and lowest unoccupied molecular
orbital (LUMO) have been calculated by the
same level of theory.

18. All of the complexes were stable both in solid state and in solution.In these complexes Schiff base ligand acted
as a chelating agent towards the metal ions as a tridentate ligand via azomethine nitrogen atom, one negatively
charged oxygen atom and NiNi, CuCu and ZnZn metal centers were bridged by the sulfur atoms and thus
facilitated the linkage of two units.
Results and discussion

19. IR spectra

20. UV-Vis spectra
UV–Vis absorption spectra of the ligand H2L and its Zn(II), Cu(II) and Ni(II) dimer complexes.
The absorption maxima was slightly shifted to the longer wavelength in the complexes compared with the free
Schiff base ligand, as a result of the enlargement of the conjugate.

21. Molar conductivity measurements
The molar conductivity values of all complexes were in the range of 1.46-5.64 ohm-1 cm2 mol-1, indicating the
non-electrolytic nature of these complexes

22. The 1H NMR spectra of the Schiff base ligand and Zn(II) complex were recorded.
The azomethine proton (–CH=N) of the ligand resonated as a sharp singlet signal at 8.62 ppm.
In Zn(II) complex this signal was shifted to 8.59 ppm, indicating the involvement of azomethine group
in chelation.
In the Schiff base ligand the protons peak of Me group was observed at 2.36 ppm. The 1H NMR
spectra of zinc complex showed that these protons was shifted to the downfield approximately 0.21
ppm relative to the free ligand and observed at 2.15 ppm. Moreover, a singlet signal at 12.66
ppmconfirmed the presence of phenolic OH in the Schiff base ligand but not observed in the zinc
complex.

23. Investigation of frontier molecular orbitals
The energy gap of HOMO and LUMO were calculated for the metal Schiff base complexes in order to
investigation the stability of these complexes. The frontier orbitals details for these complexes shown in Table 5.

24. Research Highlights
• The crystal structure of a new double Schiff base was investigated.
• New zinc, copper and nickel complexes with NSO donor atoms were
synthesized.
• Fluorescence of the Schiff base ligand and its complexes were
investigated.
• The DFT calculations were performed for the optimized structures of
complexes.
• The energy gap of HOMO and LUMO were calculated for metal Schiff
base complexes.

25. A lot of Schiff bases with different structures have been synthesized but little attention has
been given to Schiff bases which include disulfide bonds
Further extensive investigation

27. References

28. ...I’m thankful for your
support and understanding….