ABSTRACT
2-[(E)-[3-[(E)-(2-hydroxyphenyl)methyleneamino]phenyl] iminomethyl]pheno 1 was synthesized from the condensation reaction of 1,3-diaminobenzene and 2-hydroxyzaldehyde m dimethylformaldehyde (DMF). Its coordination characteristic with vanadium(III) and vanadium(V) complexes was studied via, UV/Visible, IR and NMR spectroscopy; stoichiometric, melting point and conductivity determinations. The analytical data of these complexes and the mode of bonding show that, the ligand acted as a tetradentate ligand via coordination through the two azomethine nitrogen and the two hydroxylic oxygen. Mole ratio method indicated a 1: 1 ligand to metal ratio for the complexes. Vanadium(III) and vanadium(V) were determined spectrophotometrically by measuring their absorbance at 400 and 405 nm respectively. From the calibration curve, Beer’s law was valid for vanadium(III) and vanadium(V) between 0.488 -3.904 ppm. The calibration and analytical sensitivity of vanadium(III) complex is 0.074 and 0.32 while that of vanadium(V) is 0.024 and 24 respectively. Optimum pH for the formation of the complex was determined to be 10 and 11 for vanadium(III) and vanadium(V) respectively. Very few elements were found to interfere with the method. The method was successfully applied in the determination of vanadium in steel.
ABSTRACT
2-[(E)-[3-[(E)-(2-hydroxyphenyl)methyleneamino]phenyl] iminomethyl]pheno 1 was synthesized from the condensation reaction of 1,3-diaminobenzene and 2-hydroxyzaldehyde m dimethylformaldehyde (DMF). Its coordination characteristic with vanadium(III) and vanadium(V) complexes was studied via, UV/Visible, IR and NMR spectroscopy; stoichiometric, melting point and conductivity determinations. The analytical data of these complexes and the mode of bonding show that, the ligand acted as a tetradentate ligand via coordination through the two azomethine nitrogen and the two hydroxylic oxygen. Mole ratio method indicated a 1: 1 ligand to metal ratio for the complexes. Vanadium(III) and vanadium(V) were determined spectrophotometrically by measuring their absorbance at 400 and 405 nm respectively. From the calibration curve, Beer’s law was valid for vanadium(III) and vanadium(V) between 0.488 -3.904 ppm. The calibration and analytical sensitivity of vanadium(III) complex is 0.074 and 0.32 while that of vanadium(V) is 0.024 and 24 respectively. Optimum pH for the formation of the complex was determined to be 10 and 11 for vanadium(III) and vanadium(V) respectively. Very few elements were found to interfere with the method. The method was successfully applied in the determination of vanadium in steel.
INTRODUCTION
1.1 Spectrophotometry
CHAPTER ONE
In Chemistry, Spectrophotometry is the quantitative measurement of the reflection or transmission properties of a material as a function of wavelength. Spectrophotometry deals with visible light, near-ultraviolet, and near-infrared, but does not cover time-resolved spectroscopic techniques’.
Spectrophotometry involves the use of a spectrophotometer. A spectrophotometer is a device for measuring light intensity which is a function of the light wavelength. Important features of spectrophotometers are spectral bandwidth and linear range of absorption or reflectance measurement’.
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 on any of the listed light ranges that usually cover around
200nm – 2500nm using different controls and calibrations ‘. Within these ranges of light, calibrations are needed on the machine using standards that vary in type depending on the wavelength of the photometric determination.
An example of an experiment in which spectrophotometry is used is in the determination of the equilibrium constant of a solution. For instance, a certain chemical reaction may occur in a forward and reverse direction where reactants form products and products break down into reactants. At some point, this chemical reaction will reach a point of balance called an equilibrium point. In order to determine the respective concentrations of reactants and products at this point, the light transmittance of the solution can be tested using spectrophotometry. The amount of light that passes through the solution is indicative of the concentration of certain chemicals that do not allow light to pass through ‘.
The use of spectrophotometers spans various scientific fields, such as physics, materials science, chemistry, biochemistry, and molecular biology.They are widely used in many industries including semiconductors, laser and optical manufacturing, printing and forensic examination, and as well in laboratories for the study of chemical substances. Ultimately, a spectrophotometer
is able to determine, depending on the control or calibration, what substances are present in a target and exactly how much through calculations of observed wavelengths.
There are two major classes of devices: single beam and double beam. A double beam spectrophotometer compares the light intensity between two light paths, one path containing a reference sample and the other the test sample. A single beam spectrophotometer measures the relative light intensity of the beam before and after a test sample is inserted. Although comparison measurements from double beam instruments are easier and more stable, single beam instruments can have a larger dynamic range and are optically simpler and more compact. Additionally, some specialized instruments, such as spectrophotometer built onto microscopes or telescopes, are single beam instruments due to practicality.
Historically, spectrophotometers use a monochromator containing a diffraction grating to produce the analytical spectrum. The grating can either be movable or fixed. If a single detector, such as a photomultiplier tube or photodiode is used, the grating can be scanned stepwise so that the detector can measure the light intensity at each wavelength (which will correspond to each “step”). Arrays of detectors, such as charge coupled devices (CCD) or photodiode arrays (PDA) can also be used. In such systems, the grating is fixed and the intensity of each wavelength of light is measured by a different detector in the array. Additionally, most modem mid-infrared spectrophotometers use a Fourier transform technique to acquire the spectral information. The technique is called Fourier Transform Infrared.
When making transmission measurements, the spectrophotometer quantitatively compares the fraction of light that passes through a reference solution and a test solution. For reflectance measurements, the spectrophotometer quantitatively compares the fraction of light that reflects from the reference and test samples. Light from the source lamp is passed through a monochromator, which diffracts the light into a “rainbow” of wavelengths and outputs narrow bandwidths of this diffracted spectrum. Discrete frequencies are transmitted through the test sample. Then the photon flux density (watts per meter squared usually) of the transmitted or reflected light is measured with a photodiode, charge coupled device or other light sensor. The transmittance or reflectance value for each wavelength of the test sample is then compared with
the transmission (or reflectance) values from the reference sample3.
In short, the sequence of events in a modem spectrophotometer is as follows: The light source is imaged upon the sample
A fraction of the light is transmitted or reflected from the sample
The light from the sample is imaged upon the entrance slit of the monochromator
The monochromator separates the wavelengths of light and focuses each of them onto the photo detector sequentially.
Many older spectrophotometers must be calibrated by a procedure known as “zeroing.” The absorbancy of a reference substance is set as a baseline value, so the absorbance of all other substances are recorded relative to the initial “zeroed” substance. The spectrophotometer then displays percent absorbance (the amount of light absorbed relative to the initial substance).The concentration of the solution can be determined by measuring the amount of light it absorbs
which requires a quantitative relationship. This is provided by Beer’s-Lambert’s Law 4
1.2 Beer-Lambert’s Law
Lambert concluded that the power P of the transmitted light varies exponentially with the path length, band directly with the power of Po of the incidence light. If P (or I) represents the power (or intensity) of transmitted light and P, (or I) represents the power incident light, then the change in P is proportional to the power of incident light multiplied by the change in thickness b of the material through which the light passes.
Mathematically, dP = KPdb
K is proportionality constant, and the negative sign indicates that P becomes smaller when b becomes larger. Rearranging and integrating the above equation 5 .
dP = –Kdb p
And
or
p
In =Kb
P,4
or
p K
Log =b
P, 2.303
Beer modified the law to apply to solution. He found that doubling the concentration of light absorbing molecules in a solution produced the same effect as doubling the thickness. The modified form of the above law is logP/P,= cbc
In this expression;
C is the concentration of the solution and is expressed in moles per liter .
& is molar absorptivity (molar extinction coefficient) and b is the cell width expressed in centimeters,
thus log(P/P,,) is directly proportional to concentration of solution.
If log (P/P,) is plotted against concentration for a solution which obeys the Beer’s -Lambert law, a straight line results whose slope is – cb.
P/P is called the transmittance of the solution.
Beer-Lambert law is a combination of two absorption laws and tells us quantitatively how the amount of transmitted power depends on the concentration of the absorbing molecules and the path length over which absorption occurs .
Beer-Lambert law is well obeyed with dilute solution, where there is a linear relationship. In the plot of absorption or transmittance (i.e A or log T) at the wavelength of maximum absorption, max, versus concentration for a series of standard solution. The concentration range in which the Beer-Lambert law is obeyed is known as linear dynamic range, and only quantitative determination done within it can be accurate and reliable.
Beer-Lambert law as expressed in the equation above can be used in several ways. Molar absorptivities of species can be calculated, if the concentration is known. The measured value of absorbance can be used to obtain concentration if absorption and path length are known. The law also applies to solution containing more than one kind of absorbing substance. Provided, that there is no interaction among the various species, the total absorbance substance. The total absorbance for multi-component system at a single wavelength is the sum of individual absorbancies.
1.3 Ultra Violet (UV) Spectrophotometry
The most common spectrophotometers are used in the UV and Visible regions of the spectrum. Light of wavelength between 400nm and 750 nm is visible and the instrument used to measure it is ultraviolet spectrometer and it absorbs light in the visible and near ultraviolet region, that is in the 200-750 nm range. This light is of higher frequency with respect to the nearby protons.
In Ultra Violet spectrophotometer, the samples are usually prepared in cuvettes; and fill up to mark, the chosen wavelength is set and the maximum absorbance is taken once the cuvette is placed inside the UV machine 6 .
1.4 Infrared (IR) Spectrophotometry
Spectrophotometers designed for the main infrared region are quite different because of the technical requirements of measurement in that region. One major factor is the type of photosensors that are available for different spectral regions, but infrared measurement is also challenging because virtually everything emits IR light as thermal radiation 7 .
A molecule is constantly vibrating, that is, its bonds stretch and bend with respect to each other,
changes in vibrations of a molecule are caused by absorption infra red light.
The infrared spectrum helps to reveal the structure of a new compound by telling us what groups are present in or absent from the molecule . IR is a highly characteristic property of an organic compound/ element because a particular group of atoms give rise to characteristic absorption bands.
1.5 Nuclear Magnetic Resonance (NMR)
NMR is a research technique that exploits the magnetic properties of certain atomic nuclei to determine physical and chemical properties of atoms or the molecules in which they are contained. It relies on the phenomenon ofNMR and can provide detailed information about the structure, dynamics reaction state and chemical environment of molecules ‘.
‘H, ‘N, ‘C and P are highly abundant isotopes whilst ‘N and ‘C are present at only low level <1 %. In simply terms, when the sample is placed in the magnet the nuclei of the atoms align with the magnetic field. Typically the magnets used in NMR spectroscopy are very strong
with pulses of energy in the radio frequency (RF) range, typically 40-800 MH, to the sample. The pluses cause Nuclei to rotate away from their equilibrium position and they start to precise
(rotate) around the axis of the magnetic field. The exact frequency at which the nuclei precise is related to both the chemical and physical environment of the atom in the molecule. This results in a spectrum showing many absorption peaks, whose relative position, reflect different environments of portions which can give unbelievable detailed information about molecular structure.
The various aspects of the NMR spectrum are 7
The number of signals which tell us how many different kinds ofprotons that are in a molecule. The position of the signals which tells us about the electronic environments of each kind of proton.
The intensities of the signals which tells us how many protons of each kind.
The splitting of a signal into several peaks, which tells us about the environment of the protons. NMR can also be used to look at dynamic processes. These include internal motions within regions oflarger molecules such as loops in a protein or the base pair in DNA or RNA.
1.6 Schiff Base
Schiff base is a term used to describe the product formed when an amme undergoes a condensation reaction with a carbonyl compound or it is said to be the nitrogen analog of an aldehyde or ketone in which the C = 0 group is replaced by a C = N-R group “. A German Chemist named Hugo Schiff discovered these bases. He discovered the Schiff bases and other imines, and was responsible for research into aldehydes, the field of amino acids and the Biuret reagent. He also had the Schiff test named after him’. Schiff bases are synonymous with imines, and even Azomethines ” An imine is a functional group or chemical compound containing a carbon- nitrogen double bond”. Imines can be classified further as Aldimines and Ketimines and this mainly depends on the type of carbonyl compound involved in the reaction. Imines derived from aldehydes are called aldimines [Scheme l] while those from ketones arc called ketimines
This material content is developed to serve as a GUIDE for students to conduct academic research
SPECTROPHOTOMETRIC DETERMINATION OF VANADIUM(III) AND VANADIUM(V) USING 2-[(E)-[3-[(E)-(2-HYDROXYPHENYL)METHYLENEAMINO] PHENYL]IMINOMETHYL]PHENOL>
PROJECTOPICS.com Support Team Are Always (24/7) Online To Help You With Your Project
Chat Us on WhatsApp » 07035244445
DO YOU NEED CLARIFICATION? CALL OUR HELP DESK:
07035244445 (Country Code: +234)YOU CAN REACH OUR SUPPORT TEAM VIA MAIL: [email protected]