Schiff base synthesis is usually acid catalyzed and it usually requires refluxing the mixture of aldehydes and amine in ethanolic solution. Synthesis and characterization of Schiff base ligands derived from substituted amine and salicylaldehyde and their complexes (Cu 2+, Co 2+) are reported. The ligands and ligand-complexes were characterized by melting point, FTIR, CHN-elemental analysis and UV-Visible analysis. The UV-Visible and elemental analysis of complexes established (1:2) mole ratio (M:L). The stability constant and thermodynamic parameters (K, ΔG, ΔH, ΔS) were determined at different temperature (30 - 40)°C which established that the metal-complexes were very stable. The review describes the promising biological activities of Schiff base and their metal complexes.
Schiff base derived from an amine and carbonyl compound is an important class of ligands that coordinate to metal ions via azomethine nitrogen and has been studied extensively [
1) They are insoluble in aqueous solution.
2) They decompose easily in acidic solution limiting their use to basic solution [
The chemistry of (C=N) double bond based complexes plays a vital role in the progress of chemistry and it has been found to possess the pharmacological activities such as malarial [
All chemicals and solvents were purchased from Fluka and BDH chemical companies. Cobalt and copper acetate were dried over P4O10 under vacuum for several days before use. Melting point was recorded on VeeGO Digital model VMP-D. Jenway. Elemental analyses (CHN) were performed by Perkin Elemer TGA. IR spectra used in the characterization of products were recorded Shimadzu, FTIR-8400S-JAPAN. UV/Vis absorption studies were measured in the region (200 - 800) nm using (10−4) M solution in ethanolic solution using U.V-9200 BIOTECH ENGINEERN MANAGEMENT CO. LTD (UK) Single beam.
The Schiff base was synthesized by refluxing ethanolic solution of (2.44 gm - 0.02 mol) salicylaldehyde with (2.74 gm - 0.02 mol) of substituted (o-benzoic, m-benzoic, p-benzoic) aniline in 20 ml warm ethanolic solution (40˚C - 50˚C, to speed up the reaction), the ratio is (1:1) for two hours [
An ethanolic solution of (2 × 10−2 M) Schiff base was added to (10−2 M) of metal ions (as dehydrated acetate salts). The mixture was stirred and refluxed for two hours. The solid coloured product obtained was filtered, washed and recrystallized from ethanol and then dried.
Physical measurements of the synthesized ligand and their metal complexes and their expected formula are shown in
Compound | Colour | Yield | M.p. |
---|---|---|---|
L1 | yellow | 78% | 120 |
Cu(L1)2 | sapphire | 56% | 187 |
Co(L1)2 | mustard | 71% | 274 |
L2 | Yellow-green | 82% | 141 |
Cu(L2)2 | Indigo | 69% | 263 |
Co(L2)2 | Rose | 62% | 226 |
L3 | Silver | 87% | 101 |
Cu(L3)2 | Azure | 63% | 190 |
Co(L3)2 | Gray | 52% | 185 |
L1 = o - position, L2 = m - position, L3 = p - position.
The data of element analysis (CHN) have shown that the results obtained are in good agreement with those calculated for suggested formula (
Spectrophotometrically from the wide studied range of molar concentration (10−5 - 10−3 M) of the mixed solution only concentration of (10−4 M) obey Beer-lambert law and showed intense colour, A calibration curve was plotted on absorbance against molar concentration in the range of (1 × 10−4 - 3 × 10−4 M), best fit straight line, were obtained. The composition of complexes formed in solution has been established by mole ratio and continuous variation methods, in both cases the result reveals (1:2) (M:L) ratio.
Compound | Founded ( calculated) | ||
---|---|---|---|
%C | %H | %N | |
L1 | 69.91 (70) | 4.11 (4.16) | 5.75 (5.83) |
Cu(L1)2 | 62.24 (62.27) | 2.82 (2.96) | 5.09 (5.18) |
Co(L1)2 | 62.90 (62.81) | 3.05 (2.99) | 5.14 (5.23) |
L2 | 70.09 (70) | 4.22 (4.16) | 5.94 (5.83) |
Cu(L2)2 | 62.26 (62.27) | 2.93 (2.96) | 5.25 (5.18) |
Co(L2)2 | 62.89 (62.81) | 2.89 (2.99) | 5.18 (5.23) |
L3 | 69.83 (70) | 4.25 (4.16) | 5.87 (5.83) |
Cu(L3)2 | 62.22 (62.27) | 2.85 (2.96) | 5.12 (5.18) |
Co(L3)2 | 62.20 (62.81) | 3.07 (2.99) | 5.22 (5.23) |
L1= o - position, L2 = m - position, L3 = p - position.
Compound | CH alphatic | CH aromatic | C=O | C=N | C-N | C=C | OH |
---|---|---|---|---|---|---|---|
L1 | 3400 | 3068 | - | 1616 | 1598 | 1425 | 1558 |
Cu(L1)2 | 3275 | 3115 | 2922 | 1598 | 1543 | 1357 | 1467 |
Co(L1)2 | 3307 | - | - | 1597 | 1541 | 1300 | 1448 |
L2 | 3500 | 3055 | 2995 | 1622 | 1678 | 1365 | 1463 |
Cu(L2)2 | 3392 | 3066 | 2879 | 1614 | 1560 | 1305 | 1469 |
Co(L2)2 | 3396 | 3070 | 2881 | 1614 | 1598 | 1390 | 1477 |
L3 | 3450 | 3074 | 2879 | 1680 | 1570 | 1431 | 1570 |
Cu(L3)2 | 3400 | 3018 | 2885 | 1614 | 1589 | 1398 | 1442 |
Co(L3)2 | 3433 | - | 2881 | 1602 | 1556 | 1409 | 1436 |
L1 = o - position, L2 = m - position, L3 = p - position.
where α = degree of analysis [
where C = concentration of the ligand which is equal the concentration of the metal.
The thermodynamic parameters (
where, K = Stability Constant, G = Free Energy, H = Enthalpy, S = Entropy.
The biological activity were studied, the effect of schiff base derivatives and its complexes on two type of
Compound | λmax nm | at 303 | at 313 | |||||||
---|---|---|---|---|---|---|---|---|---|---|
α | K × 108 | ∆H | ∆G | ∆S | α | K | ∆G | ∆S | ||
L1 | 396 | - | - | - | - | - | - | - | - | - |
Cu(L1)2 | 400 | 0.25 | 2.30 | 11.50 | 12.70 | -65 | 0.27 | 2.00 | 10.50 | -32 |
Co(L1)2 | 412 | 0.29 | 1.90 | 13.70 | 11.40 | 12 | 0.30 | 1.80 | 9.70 | 25 |
L2 | 380 | - | - | - | - | - | - | - | - | - |
Cu(L2)2 | 391 | 0.31 | 1.70 | 10.90 | 12.90 | 24 | 0.33 | 1.50 | 8.70 | 13 |
Co(L2)2 | 396 | 0.19 | 2.70 | 15.80 | 13.20 | 33 | 0.22 | 2.10 | 9.30 | -34 |
L3 | 400 | - | - | - | - | - | - | - | - | - |
Cu(L3)2 | 408 | 0.22 | 2.60 | 11.00 | 14.90 | 53 | 0.25 | 2.30 | 11.30 | 41 |
Co(L3)2 | 415 | 0.31 | 1.70 | 13.80 | 12.30 | -41 | 0.32 | 1.60 | 9.80 | 30 |
Compound | Aeromomas hydrophila (−) | Staphylococcus aureus (+) |
---|---|---|
L1 | - | - |
Cu(L1)2 | - | 12 |
Co(L1)2 | - | 10 |
L2 | - | 10 |
Cu(L2)2 | - | 12 |
Co(L2)2 | - | 10 |
L3 | - | 10 |
Cu(L3)2 | - | 12 |
Co(L3)2 | - | 10 |
L1 = o - position, L2 = m - position, L3 = p - position.
Bacteria Aeromomas hydrophila (−) and Staphylococcus aureus (+) have been described in
Schiff base of [o-benzyl, m-benzyl, p-benzyl] aniline with salisaladehyed was synthesized and characterized by analytical and spectral, FTIR, CHN technique. These compounds exhibited significant biological activities.
The author thanks the Iraqi Government, Ministry of Higher Education and Basrah University for the financial support provided for this work. The author is thankful of the support of the college of Education and Iraq Marine Science Center, Basrah University in undertaking the antibacterial studies.
Hanaa Hameed Haddad, (2016) A New Schiff Base Derivatives Designed to Bind Metal Ion (Cu, Co): Thermodynamics and Biological Activity Studies. American Journal of Analytical Chemistry,07,446-451. doi: 10.4236/ajac.2016.75041