SYNTHESIS AND CHARACTERIZATION OF AN AZO DYE AND ITS IRON COMPLEX

An azo dye and its iron complex have been synthesized and characterized using IR and UV-Vis spectrophotometer. The azo dye is prepared by coupling 3-aminophenol and 2-naphtol after which the iron complex is synthesized by coupling the unmetallised dye with FeCl 3 . The unmetallized dye has its maximum absorption wavelength at 436.00nm while the metal complex dye has 341.50nm. The IR spectra showed the value of –N=N-stretching frequency at 1458.23cm -1 for both the unmetallised dye and its metal complex, and which is within the range of 1400-1500cm -1 . This indicates that the synthesized complexes contain azo an azo group. The IR spectra showed the value of C-N frequency at 1267.27cm -1 for both the unmetallised dye and its metal complex. Also, The IR spectra showed the value of O-H frequency at 3408.33cm -1 for dye while 3402.54cm -1 for metal complex dye. C=C has the IR spectra frequency of the dye at 1514.17 cm -1 which is within the range of 1450-1600 cm -1 . The metal complex dye shows the IR value of Fe-N at 263 cm -1 and Fe-O at 576 cm -1 .

The solvent in which the reactions are carried out in water, which offers obvious economic and environmental advantages over all other solvents. It is likely that in the future, azo dyes are likely to assume even greater importance as some of the other chemical types, notable anthraquinones, become progressively less economic. In terms of their colour properties, azo dyes are capable of providing virtually a complete range of hues. There is no doubt though that they are significantly more important commercially in yellow-brown, orange and reddishbrown colours (i.e. absorbing at shorter wavelengths), than in blues and greens. Azo dyes are capable of providing the high intensity of colour, about twice that of the anthraquinones, and reasonably bright colours (Prival, 1998). They are capable of providing reasonable to very good technical properties, for example, fastness to light, heat, water and other solvents, although in this respect they are often inferior to other chemical classes, for example, arbonyl and phthalocyanine dyes, especially in terms of light fastness. The prime reason for the commercial importance of azo dyes is that they are the most cost-effective of all the chemical classes of organic dyes and pigments (Abd-Alredha, 2012).

Production of a dye by coupling 3-aminophenol with 2naphthol
The dye was prepared with slight modification of the method of David (2008) as follows: 2.00g of 3-aminophenol was weighed and dissolved in a conical flask (A) containing 30 ml of distilled water. 5 ml of Conc. HCl was slowly added and stirred until complete dissolution. The solution was cooled in an ice-water bath until its temperature is below 5 0 C. 2.00g of 2-naphthol was dissolved in 10ml of 1M NaOH in an Erlenmeyer flask (B). 0.35g of NaNO2was added into a 5ml of distilled water in a test tube (C). The solution prepared in (C) was transferred into the solution prepared in (B). 10 g of crushed ice was placed in a 500 ml beaker (D) and 3ml of conc. HCl was added. The solution prepared in (B) was transferred into (D) and stirred for 7 minute to form the diazonium salt. The solution was then cooled below 5 0 C. The solution in (A) was transferred into (D) and stirred. The solution was kept for 24 hours before it was filtered, wash and dried. Preparation of metal complex dye 0.6 g of unmetallised dye was dissolved in 10 ml of methanol in a beaker. The solution was heated to 80 0 C while stirring. A 0.6 g of FeCl3 was added in a 10 ml beaker to the mixture. 3 ml of 0.1M NaOH was added to adjust the pH to 8. The mixture was stirred at 80 0 C for 25 minutes. The product was filtered, wash with methanol and airdried.

DISCUSSION
The metal complex dye was synthesized by reacting 3aminophenol and sodium nitrite to form a diazonium salt which was then coupled with 2-naphthol to give an unmetallized dye. The unmetallized dye was reacted with FeCl3 to give a metal complex.
The absorption maximum of the unmetallized dye was 436.00 nm and that of the metal complex dye was 341.50 nm. The change in the absorption maximum of the metal complex from its ligand indicates the coordination of the ligand to the metal. This is agree with the findings of Abd-Alredha et al, 2012.
The IR spectra showed the value of -N=Nstretching frequency at 1458.23 cm -1 for both the unmetallised dye and its metal complex, and which is within the range of 1400-1500 cm -1 . This indicates that the synthesized complexes contain azo group. The IR spectra showed the value of C-N frequency at 1267.27 cm -1 for both the unmetallised dye and its metal complex. Also, the IR spectra showed the value of O-H frequency at 3408.33cm -1 for dye while 3402.54 cm -1 for metal complex dye. C=C has the IR spectra frequency of the dye at 1514.17cm -1 which is within the range of 1450-1600cm -1 . The metal complex dye shows the IR value of Fe-N at 263cm -1 and Fe-O at 576cm -1 . The percentage yield obtained for the dye is 85% while the metal complex dye has 50%. The metal complex has a low yield due to interference caused by instrumental error which contains some impurities and tends to react with the work. dihydronaphthalen-2-ol and 309.02 g/mol for 1:2 iron metal complex respectively.

CONCLUSION
An azo dye (3-aminophenol and 2-naphthol) and its metal complex (1:2 iron metal complex) were synthesized and characterized by FTIR and UV-Vis spectrophotometer. The proposed structure of the metal complex has been illustrated in Fig 4.1. The unmetallisd dye has a maximum absorption wavelength of 36.00 nm while the metal complex has 341.50nm. The vibrating frequencies of the unmetallised dye and its complex fall within the range of IR spectra as provided by reviewed pieces of literature The physical properties of the dye and complex synthesized were also determined o be deep brown for the azo dye and reddish-brown for its metal complex.