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  • 1. ISSN (Print): 2328-3777, ISSN (Online): 2328-3785, ISSN (CD-ROM): 2328-3793 American International Journal of Research in Formal, Applied & Natural Sciences AIJRFANS 14-271; © 2014, AIJRFANS All Rights Reserved Page 136 Available online at http://www.iasir.net AIJRFANS is a refereed, indexed, peer-reviewed, multidisciplinary and open access journal published by International Association of Scientific Innovation and Research (IASIR), USA (An Association Unifying the Sciences, Engineering, and Applied Research) Synthesis, Characterisation and Thermal studies of polymeric Cu(II), Zn(II) and Cd(II) complexes with 4-{(E)-1-(pyrimidin-2-ylimino)ethyl}-6- ((z)-1-(pyrimidin-2-ylimino)ethyl)benzene-1,3-diol and 4-{(E)-1-(p- tolylimino)ethyl}-6-((z)-1-(p-tolylimino)ethyl)benzene-1,3-diol L. B. Roya , Pragya Kumarib , Madhu Bala* a Department of Civil Engineering, National Institute of Technology, Patna-800005,Bihar (INDIA) b Department of Life Science (Chemistry), United Institute of Technology, Industrial Area, Nainy, Allahabad, U.P (INDIA) * Department of Chemistry, National Institute of Technology, Patna-800005, Bihar (INDIA) I. INTRODUCTION The design of polymeric architecture in coordination compounds by ligand assisted reaction have aroused considerable interest due to multidimensional utility of polymers in industrial Technology and catalysis[1-3] . An additional interest arose when the polydentate bridging ligands possess relevant importance in biological processes, because their coordination to metal serves as model of reference in Bioinorganic chemistry[4] . The most important stereochemical models for biological function and polydentate Schiff bases are considered to be the important donor molecules for coordination chemistry[5-6] . The Schiff base ligand containing nitrogen, oxygen and sulphur donor sites are of prime importance due to their strong ability for formation of coordination complexes of biological potentiality, catalytic activity and photochromic properties[7-8] . In present investigation we have designed quadridentate Schiff bases 4-{(E)-1-(p-tolylimino)ethyl}-6-((z)-1-(p- tolylimino)ethyl)benzene-1,3-diol (H2bistdb) and 4-{(E)-1-(pyrimidin-2-ylimino)ethyl}-6-((z)-1-(pyrimidin-2- ylimino)ethyl)benzene-1,3-diol (H2bispdb), capable of forming polymeric complexes with metal ions and reported the synthesis and characterisation of their Cu(II), Zn(II) and Cd(II) complexes. II. EXPERIMENTAL These ligands were prepared by condensing 1,1’ -4,6-dihydroxy-1,3-phenylene)diethanone[8,9] (acdp) with appropriate amine, p-tolylamine and 2-aminopyrimidine in 1:2 molar proportion in ethanol containing a few drops of acetic acid. Abstract: Polymeric copper(II), zinc(II) and cadmium(II) complexes of polydentate ligand 1,5-bis(2- pyrimidineaminoethylidene)-2,4-dihydroxy benzene (H2bispdb) and 1,5-bis(p-tolylaminoethylidene)-2,4- dihydroxy benzene (H2bistdb) of compositions [CuL(H2O)2]n and [ML]n, (M= ZnII or CdII and H2L= H2bispdb or H2bistdb) were synthesised and characterised by analytical results, magnetic susceptibility, 1 HNMR, IR and electronic absorption studies. The thermal stability of zinc(II) and copper(II) complexes were studied and discussed. Keywords: Synthesis, Characterisation Polymeric Metal Complexes1,1’ -4,6-dihydroxy-1,3- phenylene)diethanone Schiff bases
  • 2. L. B. Royet al., American International Journal of Research in Formal, Applied & Natural Sciences, 6(2), March-May 2014, pp. 136-140 AIJRFANS 14-271; © 2014, AIJRFANS All Rights Reserved Page 137 1,1’ -4,6-dihydroxy-1,3-phenylene)diethanone (acdp) was prepared by Fries rearrangement in anhydrous ZnCl2 on reacting dry acetic anhydride and resorcinol by reported method[8,9] . Preparation of Schiff bases Preparation of H2bistdb and H2bispdb About 19.5 gm (.01 mole) 1,1’ -4,6-dihydroxy-1,3-phenylene)diethanone was taken in 100 ml ethanol and refluxed with (0.2 mole) of appropriate amines (p-toludine or 2-aminopyrimidine) for three to four hours on a steam bath by adding 2 ml acetic acid. The cream yellow Schiff bases began to separate slowly. The refluxate was concentrated and cooled to ice temperature. The product separated was collected on a filter, washed with cold ethanol and dried in a dessicator over CaCl2. The dried samples were recrystallised from THF ethanol mixture (1:1) and dried samples were analysed for carbon, hydrogen and nitrogen contents. The ligand H2bistdb was found to contain C; 77.22%, H; 6.65%, N; 7.43% and it (C24H24N2O2) requires C; 77.42%, H; 6.45%, N; 7.52%. Melting point recorded 2430 c (uncorrected). The compound H2bispdb was found to contain C; 61.88%, H; 4.68%, N; 23.96%. The compound H2bispdb (C18H16N6O2) requires C; 62.06%, H; 4.59% and N; 24.14%. Melting point of H2bispdb recorded 2610 c. Preparation of complexes [CuL(H2O)2] and [ML]n, (M= Zn2+ or Cd2+ and H2L= H2bistdb or H2bispdb) About 0.05 mole of metal acetate was dissolved in 30 ml aqueous ethanol and added slowly with stirring to appropriate ligand (0.05 mole) dissolved in hot THF and ethanol mixture, when tary product separated slowly. The products were titurated with ether when fine powdered products were obtained. The products were collected on filter, washed with methanol and ether and dried in a desiccators over CaCl2. The analytical results of complexes are recorded in Table-A. Materials and Physical measurements: All solvents and chemicals used were E.Merck or BDH products. Metal acetates were E.Merck extra pure chemicals. The magnetic susceptibility of the complexes were determined by Gouy method at room temperature. The i.r spectra of ligands and their complexes were recorded as KBr optics in the range of 400- 4000cm-1 on Shimadzu 8201 FTIR spectrophotometer at IIT Patna. The electronic absorption spectra of ligands and their complexes were recorded on Shimadzu U-V 2500 PC series spectrometers. 1 HNMR spectra of ligand were recorded in DMSO-d6 solution with Brucker AV 300 NMR spectrometer. Mass spectra were recorded on GEOL G.C Mate spectrometer at IIT Chennai. The results of C, H, N and TG, DTA analyses were obtained from BIT Mesra, Ranchi. Table-A: Elemental analysis and physical data of complexes (Molar electrical conductance value in DMF at 310 c) Compound Colour % Elemental analysis Found (Calc.) Ωαohm- 1 mol-1 cm-2 Metal Carbon Hydrogen Nitrogen [Cu(bistdb)(H2O)2]n Brick red 13.43(13.53) 61.19(61.33) 5.66(5.54) 6.01(5.96) 4 [Cu(bispdb)(H2O)2]n Brick red 14.17(14.26) 48.31(48.55) 3.82(4.04) 18.62(18.85) 6 [Zn(bistdb)]n Light cream 14.92(15.02) 66.01(66.14) 5.13(5.05) 6.51(6.43) 5 [Zn(bispdb)]n Light cream 15.73(15.89) 52.41(52.50) 3.48(3.40) 20.18(20.41) 3 [Cd2(bistdb)]n Creamyellow 23.18(23.30) 59.53(59.78) 4.69(4.56) 5.94(5.80) 3 [Cd2(bistdb)]n Creamyellow 24.38(24.52) 48.49(48.55) 3.27(3.14) 18.13(18.32) 4 III. RESULTS AND DISCUSSION The proton NMR spectrum of 4-{(E)-1-(p-tolylimino) ethyl}-6-((z)-1-(p-tolylimino)ethyl)benzene-1,3-diol (H2bistdb) shows two sharp singlet (1 HNMR-Fig I) located at δ= 2.527 ppm and δ= 4.282 ppm assigned as tolyl CH3proton and ethylidene proton signals. The multiplets observed in 1 HNMR spectrum of H2bistdb between (δ= 7.346-7.874 ppm) are assigned as phenyl ring proton signals. The proton signals at δ= 8.001 and 8.027 ppm are attributed to phenolic proton signals. The 1 HNMR spectrum of 4-{(E)-1-(pyrimidin-2- ylimino)ethyl}-6-((z)-1-(pyrimidin-2-ylimino)ethyl)benzene-1,3-diol (H2bispdb) shows one strong singlet at δ= 4.268 ppm can be assigned to ethylidene CH3 proton signal. The multiplets between δ= 7.105 and 7.935 ppm are assigned to phenyl and pyrimidine ring (CH) proton signals. The phenolic proton signals of H2bispdb were observed at δ= 8.145 and 8.195 ppm. The mass determination of ligand H2bistdb shows molecular mass peak (Fig-M-T-1) at 373 for M+ +1 peak supporting molecular mass 372 for ligand. The base peak at 105 indicated the formation of toluidine fragment. The mass spectrum of ligand 4-{(E)-1-(pyrimidin-2-ylimino)ethyl}-6-((z)-1- (pyrimidin-2-ylimino)ethyl)benzene-1,3-diol(H2bispdb) show M+ +1 peak at 349 supporting molecular mass to be 348. The base peak at 79 indicated the formation of pyrimidine fragment. The mass and 1 HNMR spectra of ligand H2bistdb and (H2bispdb) are consistent with their assigned structure.
  • 3. L. B. Royet al., American International Journal of Research in Formal, Applied & Natural Sciences, 6(2), March-May 2014, pp. 136-140 AIJRFANS 14-271; © 2014, AIJRFANS All Rights Reserved Page 138 The ligands are potent quadridentate (N-O) donor coordinating molecules capable of forming bridging group in polymeric complexes. The elemental analysis of the complexes correspond to composition [CuL(H2O)2]n, (H2L= H2bistdb or H2bispdb) and [ML]n, (M= ZnII or CdII and H2L= H2bistdb or H2bispdb). The complexes are quite stable in air at elevated temperature. The complexes are insoluble in water, methanol and ethanol but dissolve appreciably in DMF and DMSO. The complexes partially dissolve in dioxan and THF. The DMF solutions of complexes are almost non conducting (Ωα = 4-5 ohm-1 mol-1 cm2 ) supporting their non ionic characters[10] . As expected zinc(II) and cadmium(II) complexes are diamagnetic and copper(II) complexes are paramagnetic. The effective magnetic moment value of [Cu(bistdb)(H2O)2] and [Cu(bispdb)(H2O)2] at room temperature are 1.87 and 1.89 B.M respectively occur in the range of magnetically dilute distorted octahedral copper(II) complexes[11- 12] . The electronic absorption spectrum of H2bistdb in ethanol shows electronic bands at 234, 262 and 330 nm assigned as σ π *, ππ* and nπ* transitions. The ligand H2bispdb shows electronic transitions at 228, 256 and 305 nm assignable as σ π *, ππ* and nπ* transitions. These transitions are obscured in complexes due to strong charge transfer transitions of complexes. The electronic absorption spectrum of DMF solutions of zinc(II) and cadmium(II) complexes show strong absorption below 390 nm due to charge transfer absorption. The Cu(II) complexes [Cu(bistdb)(H2O)2] shows a medium band at 520 nm and weak broad band at 680-690 nm attributed to 2 B1g2 B2g and 2 B1g2 A1g , 2 Eg transitions. The brick red copper(II) complex [Cu(bispdb)(H2O)2] shows strong absorption below 400 nm due to charge transfer transition. The medium band at 530-540 nm observed has been attributed to 2 B1g2 B2g and a broad band at 670-700 nm to 2 B1g2 A1g , 2 Eg transitions.
  • 4. L. B. Royet al., American International Journal of Research in Formal, Applied & Natural Sciences, 6(2), March-May 2014, pp. 136-140 AIJRFANS 14-271; © 2014, AIJRFANS All Rights Reserved Page 139 The i.r. spectra of ligands and their complexes display characteristic IR vibrations of phenolic OH and ethylideneimino (C=N) groups. The i.r spectrum H2bistdb shows ν(OH) vibration at 3501 and broad band at 3190-2973 cm-1 due to hydrogen bonded phenolic OH group. The methyl (CH3) group stretching band can be assigned to i.r. band at 2973 cm-1 . The phenolic group stretching band of ligand disappears in its complexes supporting deprotonation of (OH) proton on coordination. The ligand (IR-Fig-A3) show ν(C=N) vibration at 1642 cm-1 which is shifted to lower vibrations and observed near 1600±5 cm-1 supporting coordination of ligand through (C=N) nitrogen. A large number of i.r. bands in finger print region are assigned to phenyl group and ethylidene part skeletal vibrations. Diaquo copper(II) complex [Cu(bistdb)(H2O)2] shows a broad strong band at 3409 cm-1 for ν(H2O) vibration and a medium band at 663 cm-1 for rocking band of coordinated H2O group. The ν(C=N) of ligand was shifted to lower wave number and located at 1604 cm-1 supporting coordination of (C=N) nitrogen to copper (II).The ligand H2bispdb shows phenolic group ν(OH) at 3388 cm-1 and broad band near 3195 cm-1 due to hydrogen bonded phenolic group. The ν(C=N) of ligand (IR-Fig-M2) was observed 1634 cm-1 which is shifted to lower frequency in almost all complexes and observed at 1600±5 cm-1 . The phenolic group ν(C-O) of H2bispdb was assigned to a band at 1156 cm-1 which is shifted to higher wave number and observed near 1350±10 cm-1 supporting coordination of deprotonated phenolic oxygen atom.
  • 5. L. B. Royet al., American International Journal of Research in Formal, Applied & Natural Sciences, 6(2), March-May 2014, pp. 136-140 AIJRFANS 14-271; © 2014, AIJRFANS All Rights Reserved Page 140 The TGA and DTA studies of complexes were performed in the range of 400 -7200 c in static air. The TG curve of copper(II) complex [Cu(bistdb)(H2O)2] starts loss in weight at 1600 c giving DTA maxima at 1800 c and DTG peak at the same temperature and give stable product at 2100 c. The weight loss corresponds to 2H2O per copper atom supporting coordination of both H2O molecule for each copper(II) in complex. The product formed at 2100 c is very stable and remains stable upto 5400 c without loss in weight showing an exothermic DTA maxima 4800 c indicating phase change in complex. The complex started slow decomposition with weight loss and showing DTG maxima at 5700 c and an exothermic DTA peak at 5750 c. The loss in weight continues upto 6100 c giving stable product probably CuO. The weight of residue required is 16.94 and observed for formation of CuO is 17.02%. The TG curve shows that the product [Cu(bispdb)(H2O)2] is also stable upto 1250 c and starts loss in weight giving DTG maxima at 1700 c and an exothermic DTA peak at 1700 c. The loss in weight continues upto 1900 c giving stable product [Cu(bispdb)]n. The loss incurred is 8.24% and calculated for loss of two coordinated water is 8.08%. The TG curve shows that product is stable upto 4900 c but shows an exothermic DTA maxima at 3800 c attributable to change in phase structure of complexes. The TG curve shows that on heating after 4900 c the complex starts decomposes showing an exothermic peak at 5300 c and DTG maxima at 5250 c. The loss continues giving stable metal oxide at 6000 c. The loss in weight corresponds to expected loss 82.15% for formation of CuO. The Zn(II) complex, [Zn(bistdb)]n is stable upto 3300 c with an exothermic DTA maxima at 3500 c indicating a phase change forming octahedral environment around metal from tetrahedral one. TG curve shows that complex starts decomposing slowly after 4400 c giving metal oxide at 520-5300 c. A broad DTA maxima at 4900 c indicated burning and decomposition of complex between 440-5200 c. The cadmium(II) complex [Cd(bistdb)]n is also stable to heat below 4200 c with phase change at 3800 c as indicated by an exothermic DTA maxima. The complex starts decomposing at 4500 c as indicated by weight loss in TG curve. The complex decomposes completely between 450-520 in static air giving stable metal oxide (CdO). The observed weight of residue 26.82% corresponds to expected weight of CdO, 26.61%. The decomposition process is exothermic, showing DTA maxima at 4800 c. The exceptionally high thermal stability of complexes supported polymeric structure of complexes. The copper(II) complexes have higher stability than Zn(II) and Cd(II) complexes indicating strong coordination of Cu(II) than that of Zn(II) and Cd(II) complexes. Thus from the studies of molecular composition and physical data, the following polymeric structure is suggested for H2bistdb or H2bispdb complexes of Cu(II), Zn(II) and Cd(II). Conclusion The ligand H2bistdb and H2bispdb forms thermally stable polymeric complexes with Cu(II), Zn(II) and Cd(II). These ligand coordinates as N, O, donor chelating molecule forming bridge between metal atoms. Acknowledgement: Thanks are due to authority of IIT Patna for IR and UV spectral measurement and B.I.T Mesra for C, H, N analysis, TG and DTA measurements. References: [1] A. I. Balch, Prog. Inorg. Chem. vol.41, 1994, pp. 239. [2] G. R. Newkome, Chem. Rev., vol.93, 1993, pp. 2067. [3] N. H. Tarte, Hyun Yong. Cho, and IhI. Woo. Seong, Macromolecules vol. 40, 2007, pp. 8162-8167. [4] P. A. Vigato and S. T. Tamburine, Coord. Chem. Rev., vol. 248, 2004, pp. 1717. [5] S. R. Collinson and D. E. Fenton, Coord. Chem. Rev., vol. 19, 1996, pp. 148. [6] M. Calligaris and L. Randaccio, “Schiff bases as acyclic polydentate ligands” In comprehensive coordination chemistry, Eds. G. Wilkinson, R. D. Gillard, and J. A. Mc Cleverty, Pergaman Press, Oxford, vol. 2 1987, pp.715. [7] Dikonda, S. Rani, V. A. Parupalli, Lakshami and V. Jagadyaraju, Trans. Met. Chem. vol.19, 1994, pp.75. [8] Anjaneyalu and A. S. R. Prasad, Current science, vol. 48 1979, pp. 300. [9] A. Balasubramanian and P. Sankaran, Indian. J. Chem., Sec B vol. 20B(11), 1981, pp. 989. [10] W. J. Geary, Coord. Chem. Rev. vol. 7 1971, pp.81. [11] E. Foster and D. M. L. goodgame, Inorg. Chem., vol. 4, 1965,pp. 823, [12] A. B. P. Lever “Inorganic Electronic Spectroscopy” Elsevier, Amsterdam, 1968. [13] M. Joseph, A. Sreekanth, V. Suni, and M. R. P. Kurup Spectro Chim. Acta. vol. 74, 2009, pp. 907. [14] K. B. Deepa and K. K. Aravindakshan, Synth. React. Inorg. Metal. or Chem., vol. 30, 2000, pp. 1601. [15] K. Nakamotto “Infrared and Raman Spectra of Inorganic and coordination compounds” 3rd Ed, John Wiley & sons, New York, U.S.A, 1978.