ABSTRACT
The Schiff base
ligand, 2-[(E)-[{3–[(2-hydroxybenzylidene)amino]phenyl}imino)methyl]phenol was
synthesized by condensing 1,3-diaminobenzene and 2-hydroxybenzaldehyde in
absolute ethanol. Its Cr(III) and Cr(VI) complexes were equally synthesized.
The ligand was characterized via UV, IR and NMR spectroscopy, whereas the
complexes were characterized based on UV and IR spectroscopy and conductivity
values. Stoichiometric studies indicated 1:1 metal to ligand ratio for both
complexes. Cr(III) complex absorbed at 1042.56 cm-1 υ(C-O), 532.37
cm-1 υ(Cr-N) and 607.60 cm-1 υ(Cr-O) while the Cr(VI)
complex absorbed at 1182 cm-1 υ(C-O), 749.37 cm-1 υ(Cr-O)
and 457 cm-1 for υ(Cr-N). Based
on UV, IR and NMR studies, the ligand coordinated to the metals using the
nitrogen and oxygen atoms. Spectrophotometric determination of the metals using
the ligand was done at 368 nm for Cr(III)
and 465 nm for Cr(VI).Optimum
conditions for complexation and stability were studied and it was shown that
optimum pH for Cr(III) and Cr(VI) were 13.0 and 2.0 respectively. Very few ions
such as Co2+, Cu2+, Mn2+, Mg2+, Fe3+
and Zn2+ interfered with the determination. Beer’s law was obeyed
between 0.02 to 0.14ppm for both metals. The method was successfully applied in
the analysis of steel.
TABLE OF CONTENTS
Title page – – – – – – – i
Approval – – – – – – – – ii
Declaration – – – – – – – iii
Dedication – – – – – – – – iv Acknowledgements – – – – – – – v
Abstract – – – – – – – – vi
Table of contents – – – – – – vii
List of Tables — – – – – – – – xi
List of Figures – – – – – – – – xii
List of Schemes – – – – – – – xiii
CHAPTER ONE
1.0 INTRODUCTION – – – – – – 1
1.1 Spectrophotometry – – – – – – 1
1.1.1 Beer- lambert’s law – – – – – 2
1.2 Schiff Base Ligands – – – – – – 4
1.2.1 Preparation of Schiff bases – – – – – 4
1.2.2 Uses of Schiff Bases – – – – – – 6
1.2.3 Biological Importance of Schiff Bases – – 7
1.2.4 Schiff Base Metal Complexes – – – – 8
1.3 Chromium – – – – – –
1.3.1 Determination of Chromium – – – – – 9
1.3.2 Uses – – – – – – – 10
1.4 Statement of the Problem – – – – 11
1.5 Aims and Objectives – – – – 12
CHAPTER TWO
2.0 LITERATURE REVIEW – – – – – – 14
2.1 Catalytic Spectrophotometric Determination of Chromium – – 14
2.2 Spectrophotometric Determination Of Trace
Level Chromium Using Bis
(Salicylaldehyde)
OrthophenyleneDiamine In Non-ionic Micellar Media – 14
2.3 Spectrophotometric Determination of Chromium(III)
and chromium(VI)
in sea water.- – – – – – – – 15
2.4 Determination of Hexavalent Chromium in drinking water by ion chromatography with
post-column derivatization and UV-visible spectroscopic detection. – 15
2.5 Determination of Cr(VI) in environmental sample evaluating Cr(VI) impact in a contaminated area. – – – – 16
2.6 Indirect Extraction – Spectrophotometric Determination of chromium. – – 17
2.7 Sensitivity Determination of Hexavalent
chromium in drinking water – – 18
2.8 Determination of Dissolved Hexavalent Chromium
in Drinking Water, Ground Water and Industrial Waste Water Effluents by
Ion Chromatography- – – – 18
CHAPTER THREE
3.0 Experimental – – – – – – 19
3.1 Apparatus – – – – – – – 19
3.2 Preparation of Stock Solution – – – – – – 19
3.3 Preparation of Buffer Solutions – – – – – 20
3.4 Synthesis of the Ligand (HBAPP) – – – – 20
3.5 Synthesis of Chromium (III) and Chromium (VI)
Complexes of HBAPP –
21
3.5.1
Determination of the Stoichiometry of the Complexes by Slope-Ratio Method. 22
3.6 General Procedure for the Complexation Studies – – 23
3.6.1 Effect of Time on the Formation of the Complexes – – 23
3.6.2 Effect of Temperature on the Formation of the Complexes – 23
3.6.3 Effect of
Concentration of Reagent on the Formation of the Complexes –
23
3.6.4 Effect of pH on the Formation of the Complexes – – 23
3.6.5 Effect of
Interfering Ions on the Formation of the Complexes – – –
23
3.6.6 Calibration Curve-Beer’s Law – – – – – 24
3.7 Determination of Chromium in Alloy – – – 24
3.7.1 Determination of Chromium in Alloy with Flame
Atomic Absorption
Spectrophotometry – – – – – – 24
3.7.2
Determination of Chromium in Alloys with UV Spectrophotometry – – 24
CHAPTER FOUR
4.0 Results And Discussion – – – – 26
4.1 Physical Characterization and Molar Conductivity Data of the Ligands and Its Cr(III) and Cr(VI) Complexes – – – 26
4.2 Spectroscopic Characterization Of The Ligand And Its Cr(III) And Cr(VI) Complexes. – – – – – – – 26
4.2.1 Electronic Spectral Data of the Ligand and Its Complexes – 26
4.2.2 Infrared Spectra – – – – – 27
4.2.3 1H and 13C NMR Spectra of the Ligand – – – 28
4.2.4 13C NMR – – – – – – 29
4.2.5 APT (Attached Proton Test) – – – – – 29
4.3 Stiochiomery of the Complexes – – – – 30
4.3.1 Metal-Ligand Mole Ratio of Cr(III) Complex – – 30
4.3.2 Metal-Ligand Mole Ratio of Cr(VI) Complex – – 31
4.3.3 Molecular
Formulae and Structures of the Ligand and Its Complexes – 33
4.4 Complexation Studies – – – – – – 35
4.4.1 Effect of Time on the formation of the Complexes – – 35
4.4.2 Effect of the concentration of the reagent on
the formation of the complexes – 36
4.4.3 Effect of temperature on the formation of the complexes 38
4.4.4 Effect of pH on the absorbance of the complexes – – 41
4.4.5 Effect of interfering ions on the formation
of Cr(III) and Cr(VI) complexes – 42
4.5 Calibration curve for determination of Cr(III)
and Cr(VI) complexes – 44
4.5.1 Cr(III) complex – – – – – – 44
4.5.2 Cr(VI) complex – – – – – – 45
4.6 Application using steel solution – – – – – 46
4.6.1 Determination of Cr(III) in the steel solution – – – 47
4.6.2 Determination of Cr(VI) in steel solution – – – 47
4.7 Conclusion – – – – – – 47
4.8 Recommendation – – – – – – 48
References – – – – – – – 49
Appendix A – – – – – – – – 55
Appendix B – – – – – – – – 58
LIST OF TABLES
3.1: Preparation of Buffer Solution – – – – – 21
4.1: Physical Data of the Ligands and Its Complexes – – 26
4.2: Electronic Spectra – – – – – – – 27
4.3: Infrared Spectral Data of the Ligand and Its Complexes – – 28
4.4: 1HNMR
Spectral of the Ligand in CDCl3 relative to TMS (ppm) – – 28
4.5: 13CNMR Spectral Data of the Ligand – – – – 29
4.6. Effect of some interfering ions on Cr(III) Complex – – 43
4.7 Effect of some interfering ions on Cr(VI) complex – – 44
4.8. Determination of Cr(III) in the steel solution- – 47
4.9. Determination of Cr(VI) in the steel solution- – – 47
4.10. Result of
slope-Ratio plot for Cr(III) complex-fixed ligand(1.0X 10-3 M) 55
4.11. Result of
Slope- Ratio plot for Cr(III) complex- fixed metal (1.0 X10-3 M) 55
4.12. Result of
Slope-Ratio plot for Cr(VI) complex; fixed ligand (1.0 X 10-3 M) 55
4.13. Result of
Slope- Ratio plot for Cr (VI) complex; fixed metal (1.0 X-3M) 56
4.14.Variation
of Absorbance With Time for the Formation of the Complexes 56
4.15.Variation of Absorbance with Reagent Concentration for the Formation of Complexes. – – – – – – – 56
4.16.Variation of Absorbance with Temperature for the Formation of the Complexes. – – – – – – 57
4.17. Variation
of Absorbance with pH for the Formation of the Complexes. – 57
4.18 Results
of Calibration Curve-Beer’s Law for Cr(III) and Cr (VI) Complexes 57
LIST OF FIGURES
4.5: Effect of Time on the formation of Cr(III)complex – – 35
4.6: Effect of Time on the formation of Cr(VI)complex – – 36
4.7: Effect of
concentration on the formation of Cr(III) complex – – 37
4.8: Effect of
concentration on the formation of Cr(VI) complex – – 38
4.9: Effect of Temperature on the formation of Cr(III)complex 39
4.10: Effect of Temperature on the formation of Cr(VI)complex – 40
4.11: Effect of pH on the formation of Cr(III)Complex – – 41
4.12: Effect of pH on the formation of Cr(VI) Complex – – 42
4.13 Calibration curve of Cr(III) complex – – – 45
4.14 Calibration Curve of Cr(VI) Complex – – – – 46
LIST OF SCHEMES
1 Formation of Schiff base – – – – – – 22
2 The ligand – – – – – – – – 33
3 Chromium(III) complex – – – – – – 34
4 Chromium(VI) complex — – – – – – 34
CHAPTER ONE
INTRODUCTION
1.1 SPECTROPHOTOMETRY
Spectrophotometry is the quantitative measurement of the reflection or transmission properties of a material as a function of wavelength1. It is more specific than the general term electromagnetic spectroscopy in that spectrophotometry deals with visible light, near-ultraviolet, and near-infrared, but does not cover time-resolved spectroscopic techniques. Spectrophotometry is a very fast and convenient method of qualitative analysis, due to the fact that absorption occurs in less than one second and can be measured very rapidly. Molecular absorption is valuable for identifying functional groups in a molecule and for the quantitative determination of compounds containing absorbing groups2,3. A spectrophotometer is commonly used for the measurement of transmittance or reflectance of solutions, transparent or opaque solids, such as polished glass or gases. However, they can also be designed to measure the diffusivity of any of the listed light ranges that usually cover around 200 – 250 nm using different controls and calibrations1 .
The most common spectrophotometers are used in the UV and visible regions of the spectrum and some of these instruments also operate into the near-infrared region as well. Visible region (400 – 700 nm) spectrophotometry is used extensively in colorimetry science. Ink manufacturers, printing companies, textile, vendors and many more, need the data provided through colorimetry. They take readings in the region of every 5 – 20 nanometers along the visible region and produce a spectral reflectance curve or a data stream for alternative presentations.
Spectrophotometeric method is
undoubtedly the most accurate method for determining, among other things, the
concentration of substances in solution, but the instruments are of necessity
more expensive. A spectrophotometer may be regarded as a refined filter
photoelectric photometer which permits the use of continuously variable and
more nearly monochromatic bands of light. The essential parts of a
spectrophotometer are (1) a source of radiant energy (2) a monochromator i.e. a
device for isolating monochromatic light or, more accurately, narrow bands of
radiant energy from the light source (3) glass or silica cells for the solvent
and for the solution under test and (4) a device to receive or measure the
beams of radiant energy passing through the solvent4.
SPECTROPHOTOMETRIC DETERMINATION OF CHROMIUM(III) AND CHROMIUM(VI) USING 2-[E)-[{3-[(2-HYDROXYBENZYLIDENE) AMINO]PHENYL}IMINO)METHYL]PHENOL
