Design, Synthesis and Physico-Chemical Investigation of the Iron (II) Complexes Containing Heterocyclic Nitrogen Donor Ligands
S.K. Khatua1, S.C. Nayak1*, P.K.Das2, R.R. Guin1
1Department of Chemistry B.N.M.A College, Paliabindha, Bhadrak, Orissa
2P.G.Department of Chemistry GM. College Sambalpur Orissa
*Corresponding Author E-mail: saratnayak31@rediffmail.com
ABSTRACT:
A number of iron metal complexes of type [FeL4(H2O)2]SO4 where L=hetero cyclic nitrogen donor ligands (imidazole, pyridine, piperadine piperazine, indole, benzimidazole, benzotriazole, triazole, quinoline, iso-quinoline, carbazole) have been synthesized and characterized. These complexes are soluble in ordinary organic solvent. The conductivity data shows that these complexes are 1:1 electrolytic in nature. The IR spectra reveal the coordination of nitrogen of the ligand to central iron metal atom. The mass spectra for benzimidazole complex shows the molecular ion peak at 660 and base peak at 119. The thermal decomposition studies indicate the presence of water molecule which is associated to central metal ion. The loss of water molecule and decomposition of sulphate ion occurs at 2500c. Then after 1000c imidazole molecule is removed one by one, giving the Fe3O4 as the final product.
KEYWORDS: Metal, complexes, ligands, indole, benzimidazole, triazole, IRspectra, mass spectra.
The iron metal is in fact known to mankind since long. Its coordination compound started forming in this earth since 4109 years, in that contest one of the nature’s famous system hemoglobin1-4 complexes and its function plays a vital role in animal’s biological system. Although iron is relatively more abundant on the earth’s crust, it’s properties to carry oxygen in the biological 5-10 system and change of oxidation number in particular PH is say to say most important nature’s occurring in the living system
Iron forms number of complexes with nitrogen donor ligands which are most important as they resembles to many biologically active iron complexes. The heterocyclic nitrogen donor ligands are fundamental; compounds of nucleic acid, enzymes, proteins, and many other important biological active organic compounds. These ligands provides a potential binding site for metal ions.
For biological importance, we syntheses many iron(II) complexes with various nitrogen containing donor ligands and studied it’s physico-chemical properties.
MATERIAL AND METHODS:
FeSO4. 7H2O indole, pyridine are BDH reagents The iso-quinoline and carbazole are merk (germany) reagents The benzotriazole, triazole are from Sd- fine chemicals. The quinoline and piperazine are from Loba chemicals
Analytical Measurements
Micro analytical data (C. H. N) were collected using a Perkin –Elmer 2400 CHN analyzer. The Iron analysis was carried out by standard literature procedure. Molar conductance of the complexes were recorded on a direct reading systronic 304 model conductivity meter using 10-3 M solution. The IR spectra were recorded by perkin783 spectrophotometer (υ = 500-4000 cm-1) and UV-VIS spectra (λ= 200 to 800 mn) were recorded by, Chimadzu uv 1601 spectrophotometer using methanol as solvent. The mass spectral data were recorded by Q-Tof microTM spectroscope. The thermal decomposition of the complexes were obtained by using NETZSCH-geratebau GmbH thermal analyzer. The thermal decomposition measurement were carried out between 25. c to 1000. c in an atmosphere of nitrogen by using sample wt 100 mg. The rate of temperature increase of 10. c min-1 was chosen for all the measurements. The equipment records TG, DST, DT simultaneously
Synthesis of Metal Complexes---[FeL4(H2O)2]SO4
An aqueous methanolic solution containing FeSO4. 7H2O (0. 25 m mol) and ligand (1 m. mol) in methanol were taken separately. The two solutions (metal solution and ligand solution) were warmed separately. The ligand solution is added to the metal solution while on warming. The solution was stirred vigorously under nitrogen atmosphere for three 3hrs, then cooled green crystals are deposited. These are collected by filtration, washed with cold water and then with MeOH and finally by Et2O It was dried in vacuo over CaCl2 All these complexes were prepared following identical procedure and the yield was varied from 65% to 75%
RESULT AND DISCUSSION:
These series of sulphate compound presented in this work are reported in the table – 1 along with other analytical data11, melting point, and conductance values. The conductance measurement are taken in EtOH solution. The molar conductance values shows that all the metal complexes are in 1:1 ionic in nature The magnetic moments of iron complexes are around 4. 5 B, M The UV, Vis spectral studies12 of these complexes (Fig. -1) exhibit transition at lower than 400 mn This is corresponds to n→π* transition. Intense absorption bands appears in the region of 430-460 nm for these complexes. this corresponds to π →π* Finally abroad weak band is observed at 620-680 nm. This is probably due to d(Fe) →π*
IR Spectra.
The most possible assignment of IR bands13-15 useful for establishing the coordination mode of the titled complexes have been compared with the free ligands values. The most significance difference has been observed in the azoimine function The υ(C=N) and υ(N=N) appear at 1580-1600 and 1380-1390 cm-1 in Fe (II)- complexes, these are shifted to lower frequency by 20-50 cm-1 compared to free ligand values. This is common with complexes of azoimdazoles in higher congeners group (VIII). The metal sulpher band generally appears at 320-330 cm-1 but this peak does not appear due to limitation of our IR instruments
Mass spectra.
The mass spectra of the compound [Fe (bm)4(H2O)2]SO4 is in good agreement with its calculated value. The molecular ion peak appears at 660 in this spectra, . Initially one benzimidazole molecule is removed, giving the peak at 512. Then the second benzimiddazole molecules is lost from the remaining part of the compound, the peak appears at 424. Then C2H3 fragment is removed giving the peak at 279, finally the base peak at 119 is due to benzimidazole molecule
Thermal measurement of the com pound,
The compounds are thermally relatively stable. The thermal decomposition16 of these compound are multi stage process. The subsequent detachment of the ligand are observed and the Fe3O4 was the final product of the complexes. The thermal decomposition data of these compounds are summarized
The TG and DTA curves for the compound [Fe(im)4(H2O)2]SO4 is shown in the Figure-1. The TG curve for these complexes indicate that it is considerably stable up to 230c. The slow decomposition proceeds. The TG curve shows four bending at 250, 350, 450, 800, 0C These correspondence to the presence of four intermediate decomposition products.
[Fe(im)4(H2O)2]SO4 --250c--→[Fe(im)4] +2H2O + SO2+ O2
Fe(im)4] --350c--→ [Fe(im)3] + im
[Fe(im)3] --450c--→[Fe(im)2] + im
[Fe(im)2] --800c--→Fe3O4 + im
TABLE – 1 Analytical Data and Other Physical Properties of [FeL4(H2O)2]SO4 complexes % Found / (calculated)
|
Compound |
Mol Wt |
Iron |
Carbon |
Hydrogen |
Nitrogen |
Ώ |
M.P/OC |
|
[Fe(im)4(H2O)2]SO4 FeC12H18N8SO6 |
428 |
13.21 (13.08) |
33..58 (33.64) |
4.22 (4.20) |
26.14 (26.16) |
19.32 |
226 |
|
[Fe(py)4(H2O)2]SO4 FeC20H24N4SO6 |
504 |
11.23 (11.11) |
47.53 (47.61) |
4.62 (4.76) |
11.12 (11.11) |
24.36 |
>235 |
|
[Fe(pi)4(H2O)2]SO4 FeC20H48N4SO6 |
528 |
10.55 (10.60) |
45.33 (45.45) |
9.08 (9.12) |
10.62 (10.61) |
21.22 |
231 |
|
[Fe(pip)4(H2O)2]SO4 FeC16H44N8SO6 |
532 |
10.55 (10.52) |
36.01 (36.1) |
8.24 (8.27) |
21.15 (21.05 ) |
23.36 |
222 |
|
[Fe(ind)4(H2O)2]SO4 FeC32H32N4SO6 |
656 |
8.44 (8.53) |
58.48 (58.53) |
4.85 (4.87) |
8.52 (8.53) |
25.45 |
>240 |
|
[Fe(bm)4(H2O)2]SO4 FeC28H28N12SO6 |
660 |
8.42 (8.48) |
50.94 (50.9) |
4.22 (4.24) |
25.44 (25.45) |
20.98 |
232 |
|
[Fe(btz)4(H2O)2]SO4 FeC25H24N12SO6 |
664 |
8.63 (8.43) |
50.61 (50.6) |
3.64 (3.61) |
25.32 (25.30) |
23.45 |
228 |
|
[Fe(tri)4(H2O)2]SO4 FeC8H16N12SO8 |
464 |
12.16 (12.06) |
20.70 (20.68) |
3.47 (3.44) |
36.23 (36.20) |
24.65 |
226 |
|
[Fe(qui)4(H2O)2]SO4 FeC36H32N4SO6 |
704 |
7.98 (7.95) |
31.37 (31.36) |
4.52 (4.54) |
7.92 (7.95) |
21.45 |
227 |
|
[Fe(i-qui)4(H2O)2]SO4 FeC36H32N4SO6 |
704 |
7.88 (7.95) |
31.33 (31.36) |
4.48 (4.54) |
7.88 (7.95) |
21.42 |
227 |
|
[Fe(car)4(H2O)2]SO4 FeC48H40N4SO6 |
856 |
6.42 (6.54) |
67.22 (67.28) |
4.65 (4.67) |
19.63 (19.62) |
19.29 |
238 |
Im=imidazole Py=pyridine,pi=piperidine,pip=piperazine,ind=indole,bm=benzimidazole,btz=benzotriazole,tri=trizole,qui=quinoline,
i-qui=iso-quinoline,car=carbazole Calculated values in parenthesis, conductance values in ohm-1 cm2mol-1 at room temperature
The DTA curve of these complexes proceeds with three exothermic peaks at 250c, 350c, 450c, is corresponding the loss of water molecules imidazole and third molecules of imidazole. . There are one endothermic maxima appears at 800c corresponds to the formation of Fe2O3.
Fig-1 Spectrum of [Fe(Im)4(H2O)2]SO4 complex taken at Department of Chemistry IIT Kharagpur using Shimadzu UV-1601 spectrophotometer. Solvent was ethanol.
ACKNOWLEDGEMENTS:
The authors thank the authorities of the central research facility (CRF) IIT, Kharagpur for UV, IR. Spectra and thermo-gravimetric analysis. Thanks are due to the IICB kolkatta for providing mass spectra. One of us (S. C. Nayak) is thankful to the university grants commission (UGC). Kolkatta unit for financial support under a minor research project
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Received on 05.03.2012 Modified on 19.03.2012
Accepted on 25.03.2012 © AJRC All right reserved
Asian J. Research Chem. 5(4): April 2012; Page 529-531