Printer Friendly

Synthesis and Characterization of 1,2-bis[4-(pent-3-en-4yl-2-one)ethane], a Novel QuardidentateLigand and its TransitionMetal Complexes.

Byline: Muhammad Shabbir, Zareen Akhter, Asghari Gul and Michael Bolte

Abstract. A novel crystalline enaminoketone ligand was synthesized by reacting 1, 2-di (4- aminophenyloxy) ethylene with acetyl acetone. After that it was complexed with different metal acetates to prepare chromium Cr (II), cobalt Co (II), copper Cu (II) and zinc Zn (II) complexes. Elemental analysis, magnetic susceptibility measurements, thermogravimetric analysis, x-rays crystallographic studies, UV-visible spectroscopy were carried out for structural elucidation and property exploration. The ligand exhibited quardidentate structure with two N-donor and two O- donor atoms with central methylene bridge in the gauche conformation which was stabilized by two intramolecular N-H--O hydrogen bonds The dihedral angle between the two aromatic rings was 45.1 o . All complexes were thermally stable and exhibit square planar or tetrahedral geometries.

Keywords: Crystal structure; Metal complexes; Quardidentate ligand (enaminoketone)

Introduction

Multidentate Schiff base ligands have been widely studied in coordination chemistry due to their facile synthesis and interesting properties like good solubility in common solvents, their ability to reversibly bind oxygen and complexing ability towards some toxic transition metals. Moreover, the electronic and steric properties of these can be partly altered by varying the substituent on N atom [1-7].

These can accommodate a wide variety of metals having different coordination numbers resulting in metal complexes having unusual configuration and sensitivity towards environment [4-15]. These complexes are expected to show catalytical activities like they can be used (1) for the copolymerization of cyclohexane and carbondioxide and (2) in the polymerization of lactides.[18-20]

We report here in the preparation of a quardidentate, crystalline, nitrogen and oxygen donor ligand derived from acetyl acetone and 1, 2-di (4- aminophenyloxy) ethylene (DAPE) which is further used for complexation with acetates of chromium, cobalt, copper and zinc to prepare thermally stable Cr (II), Co (II), Cu (II) and Zn (II) complexes.

Results and Discussion

The ligand (L)was prepared in good yield following the reported method, scheme 1 [23].The structure and properties of the L was studied by melting point, spectroscopic studies elemental and single crystal X-ray analysis. It was found thattautomeric forms were possible for the'L'. Single crystal analysis showed that the ''ketoimines'' existed almost exclusively in enaminone tautomeric form (Fig. 1). It was further confirmed by 1 H NMR spectroscopic studies which had a broad signal around 12.47 ppm suggesting the presence of aproton bound to heteroatoms.The synthesized ligand was complexed with different transition metal acetates(scheme 2).

The resulting complexes were characterized by various analytical techniques like elemental analysis, magnetic susceptibility measurements, IR, UV-Vis spectroscopy and thermogravimetric analysis.

O N O HN

Fig. 1: Tautomeric forms of ligand L.

X-ray Structure Analysis of Ligand (L) The L crystal, suitable for single crystal X- ray studies was grown from a saturated solution (in ethanol) at room temperature for three days. A crystal of size 0.33 x 0.27 x 0.14 was mounted on a glass fiber and intensity data was collected at 173K on a STOE IPDS-II diffractometer, using M o K Alpha -radiation. The direct methods were used to solve the structure and refinement was done with full-matrix least- squares techniques on F 2 [24]. The ORTEP diagram of the ligand is shown in Fig. 2.

Crystal data, refinement details are tabulated in Table-1 and the selected bond lengths and angles for ligand summarized in Table-2. It can be seen that the central methylene bridge is gauche in conformation and the molecular conformation is stabilized by two intramolecularN-H--O hydrogen bonds (Fig. 3). The dihedral angle between two aromatic rings is 45.1 o .

Single crystal analysis showed that the presence of enaminonetautomeric form predominant in solid state Analyticaland Physical Measurements of Ligand and Complexes The elemental analyses data for L and metal complexes, summarized in the Table-4, showed good agreement with the calculated values. It revealed that metal to ligand ratio in complexes was 2:1.

The magnetic susceptibility measurements were performed at room temperature and the data related to the complexes are presented in Table-4. It showed that except zinc, all other complexes were paramagnetic in nature. Low magnetic moment of copper complex indicated presence of an unpaired electron whereas greater values for chromium and cobalt complexes showedmore number of unpaired electrons. Zinc complex showed no magnetic moment and was found diamagnetic in nature. The study showed that the geometry of copper, chromium and cobalt complexes was square planar while zinc complex was tetrahedral [25-28]. The magnetic moment data was in good agreement with the expected high spin configurations of the complexes.

IR Spectroscopy ] The IR spectrum of the quardidentate ligand showed peak around 1720 cm -1 indicating presence of C=O group. An absorption band at 3284 cm -1 was assigned to the -NH group. The IR data of the complexes indicated the coordination of the ligand was through nitrogen and oxygen atoms. The IR spectra of all complexes showed shift of C=O band to the lower frequency coincident with the appearance of new peaks around 480-540 cm -1 and 450-400 cm - 1 , assigned to the M-N and M-O bond vibrations respectively, confirming the successful preparation of the complexes[29-30]

UV Visible Spectroscopy

UV visible spectral studies of the ligand and the complexes were performed in ethanol in 200-800 nm range. The bands in regions 261 and 303nm in the ligand corresponds to Pi-Pi transitions (-C=C-and benzene) [31-32].Copper (II),chromium (II) and cobalt (II) complexes display three bands each at 280, 355, 583, 288, 405, 53 and 321, 403, 529nm respectively indicating Pi-Pi , d-d and charge transfer transitions, suggesting square planar geometry [33]. The Zn (II) complex displays two bands at 305 and 560nm owing to Pi-Pi , and charge transfer transitions, however it does not exhibit d-d transition due to completely filled d-orbital. Generally zinc forms tetrahedral complexes.

The UV-visible spectra supplement the magnetic measurements suggesting the square planar and tetrahedral geometries for the metal complexes

Thermal Analysis

Thermal analysis of the complexes was carried out under inert atmosphereat a heating rate of 10 o C/min in a temperature range of 40-800 o C. The weight loss for each complex was calculated within corresponding temperature range. The thermograms revealed the presence of four molecules of coordinated water per molecule of the complex in Cu (II), Cr (II), Co (II), and Zn (II). The proposed structure of all divalent complexes showed loss of coordinated water in a one step process at 141 0 C for Cu(II) complex, 134 0 C for Cr(II), 104 o C for Co(II) complex and 152 0 C for Zn(II) complex. Thermogravimetric data of Cu 2 L4H 2 O showed decomposition in three steps. The first step involved weight loss of 4.016% at 157 o C owing to the removal of moisture. The second weight loss step of 63.15 % (between 241 o C and 457 o C) corresponded to the loss of four coordinated water molecules (calculated 63.5) [34].

Third stage is removal of NO, CO 2 and organic moieties (between 550-663.5 o C) accompanied by further loss of 14.94% weight (calculated 14.17 %). The thermal decomposition plot reached at a constant mass of 22.53 % zone near 675 o C where almost all the volatile groups have been lost and a solid phase of metal oxide is left. The thermal decomposition of the other complexes showed similar behavior and final product in all the complexes is metal oxide [35-34]. A representative thermo gram is shown in Fig. 4. The data suggest the general formula [M 2 L.4H 2 O] where M=Cu (II), Co (II), Cr (II), Zn (II) for metal complexes. On the basis of these analytical and physical measurements the proposed structure of the complexes is shown in Fig. 5.

Table-1: Crystal data and structure refinement for Ligand L

###Formula weight###408.48

###Empirical formula###C24 H28 N2 O4

###Temperature###173(2) K

###Wavelength###0.71073 A

###Crystal system###Monoclinic

###Space group###P21/n

###Unit cell dimensions###a = 10.6102(7) Ab = 14.8207(7) Ac = 13.8242(8) A

###= 90deg = 93.822(5)deg = 90deg.

###3

###Volume###2169.0(2) A Z4

###Density (calculated)###3

###1.251 Mg/m

###1

###Absorption coefficient###0.085 mm-

###F (000)###872

###3

###Crystal size###0.33 x 0.27 x 0.14 mm

###Theta range for data collection###3.61 to 27.57deg.

###Index ranges###-13less than=h less than =13, -19 less than =k less than =19, -17 less than =l less than =17

###Reflections collected###33043

###Independent reflections###4980 [R (int) = 0.0510]

###Completeness to theta = 25.00deg###99.7 %

###Absorption correction###None

###Max. and min. transmission###0.9882 and 0.9724

###Refinement method###2

###Data / restraints / parameters###Full-matrix least-squares on F

###4980 / 0 / 284

###Goodness-of-fit on F2###1.020

###Final R indices [I Greater than 2sigma(I)]###R1 = 0.0418, wR2 = 0.1026

###R indices (all data)###R1 = 0.0566, wR2 = 0.1088

###Extinction coefficient###0.0081(14)

###Largest diff. peak and hole###0.257 and -0.171

Table-2: Selected Bond lengths [A] and angles [deg] for Ligand L.

###N(1)-C(3)###1.3456(17)

###N(1)-C(3)-C(4)###122.50(12)

###N(1)-C(14)###1.4368(16)

###N(1)-C(3)-C(31)###117.13(12)

###N(1)-H(1)###0.883(18)

###O(3)-C(5)-C(4)###123.11(12)

###N(2)-C(6)###1.3458(18)

###O(3)-C(5)-C(51)###118.81(13)

###N(2)-C(24)###1.4365(16)

###C(4)-C(5)-C(51)###118.08(12)

###N(2)-H(2)###0.881(19)

###N(2)-C(6)-C(7)###121.52(13)

###O(1)-C(11)###1.3796(15)

###N(2)-C(6)-C(61)###118.47(13)

###O(1)-C(1)###1.4363(16)

###O(4)-C(8)-C(7)###122.76(12)

###O(2)-C(21)###1.3772(14)

###O(4)-C(8)-C(81)###118.50(13)

###O(2)-C(2)###1.4353(15)

###C(7)-C(8)-C(81)###118.73(13)

###O(3)-C(5)###1.2482(17)

###O(1)-C(11)-C(12)###124.47(12)

###O(4)-C(8)###1.2517(17)

###O(1)-C(11)-C(16)###115.97(11)

###C(3)-N(1)-C(14)###124.49(11)

###O(2)-C(21)-C(22)###125.02(11)

###C(3)-N(1)-H(1)###115.4(11)

###O(2)-C(21)-C(26)###115.41(11)

###C(14)-N(1)-H(1)###120.1(11)

###C(24)-N(2)-H(2)###119.4(12)

###C(6)-N(2)-C(24)###126.26(12)

###O(1)-C(1)-C(2)###109.63(11)

###C(6)-N(2)-H(2)###114.3(12)

Fig. 2: ORTEP drawing of Ligand L.

Fig..3: Intramolecular N-H---O hydrogen bonds in ligand L.

Table-3: N-H---O hydrogen bonds in ligand L.

###H...A###d(D-H)###d(H...A)###d(D...A)###less than (DHA)

###N (1)-H (1)...O (3)###0.883(18)###2.009(18)###2.7055(15)###134.8(15)

###N (1)-H (1)...O (4)###0.883(18)###2.327(18)###3.0412(16)###138.0(15)

###N (2)-H (2)...O (3)###0.881(19)###2.462(19)###3.1712(15)###137.9(16)

###N (2)-H (2)...O (4)###0.881(19)###1.956(19)###2.6712(15)###137.4(16)

Table 4: Analytical and magnetic moment data of Ligand and its transition metal complexes

###compound###Color###% found (calc.)###Magnetic behavior

###(ueff)BM

###Metal###C###H###N

L (C24 H28 N2 O4)###brown###158###-###70.72(70.72)###6.72(6.72)###7.17(7.18)###-###-

Cu2L.4H2O###chocolate###265###20.48(20.92)###47.51(47.44)###4.13(4.61)###5.13(5.93)###1.8###Para-magnetic

###Cr2L.4H2O###dark brown###240###17.89(17.81)###49.28(49.31)###4.73(4.79)###6.20(6.16)###4.8###Para-magnetic

###Co2L.4H2O###brown###270###19.48(19.46)###48.16(48.32)###4.65(4.71)###6.13(6.04)###2.9###Para-magnetic

###Zn2L.4H2O###white###280###-###70.72(70.72)###6.72(6.72)###7.17(7.18)###-###Dia-magnetic

Fig. 5: Proposed structure of the complexes.

Experimental

Materials

Metal acetates were obtained commercially and used as received. All the chemicals and reagents used were of analytical grade. Solvents were purchased from Merck (A. R. grade) and were purified according to the standard procedures [21].

Measurements

Melting points were measured, using a MPD Mitamura Riken Kogyo (Japan) electro thermal melting point apparatus. Elemental analysis was carried out on a CHNS 932 (Leco-USA) elemental analyzer. FT-IR, model FTS 4800 MX spectrophotometer (USA) was used for FTIR analysis in the frequency range of 4000-400 cm -1 using KBr pellets. 1 H NMR spectral studies were performed on a Bruker 300MHz NMR Spectrophotometer in deuterated acetone using teteramethylsilane as internal reference. UV-Visible spectra of the ligand and the complexes were recorded in ethanol with a systronic double beam UV-Visible Spectrophotometer 2202 in the range 200-800 nm. Thermogravimetric analysis of the complexes was carried out on TGA/SDTA 851e Mettler Toledo Swiss at a heating rate of 10 o C /min over a temperature range of 40-800 o C under nitrogen flow.

The metal contents of the complexes were determined by a Shimadzu model AA-670 in solutions using nitric acid as blank reference. Magnetic properties were evaluated by a Gouy method at room temperature using Hg [Co (NCS) 4 ] as calibrant.

2-di (4-aminophenyloxy) ethylene 1, 2-di (4-aminophenyloxy) ethylenewas prepared as reported earlier [22].

Synthesis of Ligand (L) 1, 2-di (4-aminophenyloxy)ethylene (DAPE) (0.122g, 0.5 mmol) was dissolved in 20ml dried ethanol, at heating and continuous stirring in a 250ml round bottom flask fitted with a condenser, gas inlet, magnetic stirrer and hot plate. After that (0.1ml, 1.0 mmol) acetyl acetone was added dropwise to the flask under inert atmosphere. The mixture was refluxed for 24 hs till the color of the solution turned to light brown. Progress of the reactions and purity of the products were checked by thin layer chromatography on pre-coated Kiesel gel 60HF TLC plates. The solution was concentrated and kept at room temperature for 24 hs.

The crystalline product was filtered, washed with ethanol and dried in air. Good quality crystal was obtained by slow evaporation of ethanol solution for three days which was used for single crystal analysis, scheme 1.

(Equation) Scheme-1: Synthesis of ligand L. C 24 H 28 O 4 N 2 (408); C, 70.72(calc 70.59); H, 7.17 (6.86); N, 6.72(6.86)%. IR (KBr) (Upsilon cm -1 )1720 (ketonic, C=O), 1628 (C = C), 3284 (N-H). UV- Vis(ethanol) Lambda max =261.33nm. 1 H NMR (300MHz, [D 6 ]Acetone, 25oC): Delta =7.00-7.18 (m, 8H, aromatic), 5.19 (s, 2H, olefinic), 1.95 (s, 6 H, 2CH 3 ). 1.98 (s, 6H, 2CH 3 ), 12.47 (s, 2H, NH), 4.40 ( s,4H, 2CH 2 ).

Synthesis of Cr (II), Co (II), Cu (II) and Zn (II) Complexes The ligand (L) was dissolved in 20ml dried ethanol in a 250 ml round bottom flask fitted with magnetic stirrer, gas inlet and condenser. 20 ml solution of metal acetate (chromium, cobalt, copper and zinc) in ethanol was added slowly to the flask under inert atmosphere. The molar ratio of the reactant was 2:1. The mixture was refluxed for 3 hs. The progress of the reaction was checked by TLC. Different colored products obtained were filtered in hot, washed with ethanol, dried and stored under vacuum, scheme 2.

Cr 2 L.4H 2 O: Yield = 64 %, m. p. 240 o C. Color dark brown, Elemental analysis %Found (calc.) Cr17.89 (17.81) C49.28 (49.31), H6.20 (6.16), and N4.73 (4.79), Magnetic moment (u eff ):4.8BMIR (KBr) (Upsilon cm -1 ) = 1702 (ketonic, C=O), 1630 (C = C), 510 (M-N), 421 (M-O).

Co 2 L.4H 2 O: Yield (62%)., m.p 270 o C. .Color brown, Elemental analysis %Found (calc.)Co19.48(19.46),C48.16(48.32), H6.13 (6.04), N4.65 (4.71), Magnetic moment (u eff ):2.9BMIR (KBr) (Upsiloncm -1 ) = 1705 (ketonic, C=O), 1625 (C = C), 480 (M-N), 410 (M-O).

Cu 2 L.4H 2 O: Yield (72 %), m.p. 265 o C, Colour chocolate. Elemental analysis %Found(calc.) Cu.20.48(20.92),C 47.51 (47.44),H47.51 (47.44), N4.13(4.61), Magnetic moment(u eff ):1.8BM IR (KBr), (Upsilon cm -1 ) = 1699 (ketonic, C=O), 1620 (C = C), 488 (M-N), 440 (M-O).

Zn 2 L.4H 2 O: Yield (54%), m.p.280 o C, Colour offwhite. Elemental analysis %Found(calc.)Zn 21.28(21.31), C47.30 (47.21), H5.11 (5.90), and N4.91 (4.59), Magnetic moment (u eff ): zero IR (KBr), (Upsilon cm -1 ) = 1708 (ketonic, C=O), 1622 (C = C),534(M-N),432(M-O).

Conclusions

A new crystalline, quardidentate ligand having two N-donor and two O-donor atoms was synthesized and characterized successfully. The complexation of ligand with metal acetates resulted in the square planar and tetrahedral Cr (II), Co (II), Cu (II) and Zn (II)-complexes which were stable at room. ] References

1. A. Martinez, C. Hemmert and B. Meunier, Journal of Catalysis, 234, 250 (2005).

2. C. Michon, A. Ellern and R. J. Angelici, InorganicaChimicaActa, 359, 4549 (2006).

3. D. M. Boghaei and S. Mohebi, Tetrahedron, 58, 5357 (2002).

4. M. McCann, S. Townsend, M. Devereux, V. McKee and B. Walker, Polyhedron, 29, 2799 (2002).

5. T. Sato and H. Takeda, InorganicaChimicaActa, 246, 413 (1996).

6. Y. Cai, C. Y. Su, A Xu, B. Dang, Y. X. Tong, H. Q, Liu and S. Jie, Polyhedron, 20, 657 (2001). ] 7. S. Ozkar, D. Ulku, L. T. Yildirim, N. Biricik and B. Gumgum, Journal of Molecular Structure, 688, 207 (2004).

8. M. Salavati-Niasari and S. H. Banitaba, Journal of Molecular Catalysis A: Chemical, 201, 43 (2003).

9. N. Raman, V. Muthuraj, S. Ravichandran and A. Kulandaisamy, Proceedings of the Indian Academy of Science, Section A (Chemical Science), 115, 161 (2003).

10. R. Ferreira, M. Silva, C. Freire, B. de Castro and J. L. Figueiredo, Microporous and Mesoporous Materials, 38, 391 (2000).

11. A. Sachse, N. C. Mosch-Zenetti, G. Lyashenko, J. Wielandt, K. Most, J. Magull, F. D. Antonia, Pal and R. Herbst-Irmer, Inorganic Chemistry, 46, 7129 (2007).

12. X. Guangyong, L. Yuxue, S. Jieand and Q. Changtao, Inorganic Chemical Communication, 12, 796 (2009).

13. C. R. Courtney and M. F. Joseph, Polyhedron, 29, 1271 (2010). 14. B. Najoua, E. Mbarek, B. A. Mongi, A. H. M'hamed and B. Faouzi, Polyhedron, 29, 1692 (2010).

15. S. M. Islam, A. S. Roy, P. Mondal and N. Islam, Journal of Inorganic Organometallic Polymer, 22, 717 (2010).

16. A. Bastianini, G. A. Battiston, F. Benetollo, R. Gerbasi and M. Porchia, Polyhedron, 16, 1105 (1997).

17. H. Hatem, D. B. Isabelle, M. Perrin and R. Lamartine, Journal of Organic Chemistry, 69, 6521 (2004).

18. Y. Z. Zhu, J. Y. Liu, Y. S. Li and Y. J. Tong, Journal of Organometallic Chemistry, 689, 1295 (2004).

19. I. M. Lee, Focus on Organometallic Chemistry Research, 133 (2005).

20. S. Pasko, G. H. Liliane, P. Richard and A. Adulfas, Inorganic Chemical Communication, 8, 483 (2005).

21. G. G. Mohammad, M. M. Omar and A. M. Hindy, Turk. Journal of Chemical Education, 30, 361 (2006).

22. G. M. Sheldrick, SHELX 97. Program for Crystal Structure Solution and Refinement, University of Gottingen (1997).

23. R. L. Duta and A. Syamal, Elements of Magnetochemistry, 2 nd edn.(New Delhi Elsevier) (1992)

24. D. Todor and L. Carmay, Journal of American Chemical Society, 122, 11146 (2000).

25. S Chandra, D Jain, A Sharma and P Sharma. Molecules, 14, 174 (2009).

26. B. Cristovao, Journal of Serbian Chemical Society, 76, 1639 (2011).

27. K. R. Surati, B. T. Thaer and C. K. Modi, Russian Journal of Coordination Chemistry, 34, 25 (2008).

28. K. R. Surati, B. T. Thaer, S. L. Oswal, R. N. Jadeja and V. K.Gupta, Journal of Structural Chemistry, 34, 295 (2007).

29. E. Tas, A. Kilic, N. Konak and I. Yilmaz, Polyhedron, 27, 1024 (2008).

30. R. Herzfeld and P. Nagy, Current Organic Chemistry, 5, 373 (2001).

31. A. P. Lever, Inorganic Electronic Spectroscopy, second ed., Elsevier, New York (1984).

32. E. Canpolat and M. Kaya, Transition Metal Chemistry, 29, 550 (2004). ] 33. M. I. Dhar and O. Singh. Thermochimica Acta, 191, 285 (1991). ] 34. E. Dubler and G. Hanggi. Thermochimica Acta, 234, 201 (1994).

35. B. S. Furniss, A. J. Hnnaford, P. W. G. Smith and A. R. Fatchell, "Vogel's Textbook of Practical Organic Chemistry", 5th Ed., 395 (1989). ] 1 Muhammad Shabbir, 1 Zareen Akhter , 1 Asghari Gul and 2 Michael Bolte 1 Department of Chemistry, Quaid-I-Azam University, Islamabad 45320, Pakistan.

2 InstitutfurAnorganischeChemie, J. W. Goethe-Universita t Frankfurt, Max-von-Laue-Strasse 7, 60438 Frankfurt / Main, Germany.

zareenakhter@yahoo.com
COPYRIGHT 2014 Asianet-Pakistan
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 2014 Gale, Cengage Learning. All rights reserved.

Article Details
Printer friendly Cite/link Email Feedback
Author:Shabbir, Muhammad; Akhter, Zareen; Gul, Asghari; Bolte, Michael
Publication:Journal of the Chemical Society of Pakistan
Article Type:Report
Date:Feb 28, 2014
Words:3491
Previous Article:Novel HPC-Ibuprofen Conjugates: Synthesis, Characterization, Thermal Analysis and Degradation Kinetics.
Next Article:Synthesis of Potent Antibacterial Agents Derived from 5-[1-(Phenylsulfonyl)piperidin-4-yl]-1,3,4-Oxadiazol-2-thiol.
Topics:

Terms of use | Privacy policy | Copyright © 2022 Farlex, Inc. | Feedback | For webmasters |