Interaction of naphthalene acetic acid with dipositive metal ions and the characterization of the complexes

On literature review, the studies on carboxylic acids reveal that their coordination chemistry has been studied extensively. However, in view of the absence of reports on the coordination chemistry of substituted acetic acid moieties the present investigation has been undertaken. In the present work, naphthalene acetic acid (NAA) a base moiety was characterized by elemental analysis, Ultra Violet – Visible, FT-IR, and H-NMR spectroscopy and magnetic susceptibility. Studies and the interaction of the base NAA with bivalent metal ions like cobalt (II), copper (II), nickel (II) and mercury(II) in nonaqueous media like ethanol was studied. The metal complexes of cobalt (II), copper (II), nickel (II) and mercury(II) ions with NAA are synthezied in solid state and their characterization was done by chemical analysis, electrical conductivity, elemental analysis and spectral measurement (UV-visible, FT-IR, and H-NMR).Magnetic susceptibility values have also been measured for the complexes synthezised. Key-Words: Naphthalene acetic acid, Bivalent metal ions. Introduction Co-ordination chemistry is a rapidly developing field in chemistry. It has versatile applications in a number of ways. Many naturally occurring substances like chlorophyll (green pigment of plants) and haemoglobin (coloring matter in blood) are co-ordination compounds. The transition metals have a maximum number of vacant d-orbital and can gain considerable stability by accepting electrons from the ligands in the form of dative bonds with the resultant formation of a metal-ligand complex . The tendency of the transition metals to form complex compounds is particularly marked with iron, cobalt and nickel.Indole-3 acetic acid, naphthalene acetic acid, and 2,4dichlorophenoxyacetic acid are the well known plant growth regulating hormones, widely used in agricultural field [13, . The derivatives of these hormones were also found to have plant growth regulating and other biological activities [13, 15, . * Corresponding Author E.mail:[email protected], [email protected] Material and Methods A short account of the analytical methods employed in this work is presented in this chapter. Molar conductance, magnetic susceptibility, infrared spectral measurement, ultra-violet spectral measurement, H NMR spectral measurement, elemental analysis and chemical analysis were carried to characterize the synthezised compounds. Electrical Conductivity Measurement was measured the concentration around 10M . The infra-red spectra of the ligand NAA and the complexes were taken as KBr pellets in the conventional range of 4000-400 cm. The H-NMR spectrum was recorded employing TMS as internal reference and DMSO-D6 and CHCl3-D as solvent at 300 K. The H-NMR spectral study has been carried out to elucidate the structure of the organic ligand NAA and its mercury (II) complex. The electronic spectra of the present ligand and the coloured metal complexes were measured in DMF or DMSO solutions using a double beam UV – visible spectrophotometer Lambda 35.The working range of the instrument was 350 – 1100nm. Magnetic measurements were carried out using a Gouy magnetic balance. The Gouy tube was calibrated using Hg[Co(SCN)4]and diamagnetic corrections were made with Pascal’s constants. The effective magnetic moments were calculated using Curie’s relation, μeff = 2.84[ ΧM corr .T]B.M, where, T is the absolute temperature at which measurements were done. The metal complexes of naphthalene acetic Research Article [Ananthalakshmiet al., 4(5): May, 2013] CODEN (USA): IJPLCP ISSN: 0976-7126 Int. J. of Pharm. & Life Sci. (IJPLS), Vol. 4, Issue 5: May: 2013, 2672-2679 2673 acid were analyzed for the metal content after decomposing them in conc.HNO3. Cobalt (II), nickel (II) and mercury (II) were determined gravimetrically. Copper (II) was determined by the iodometric titration method. The chemical composition of the ligand naphthalene acetic acid was determined by analyzing carbon and hydrogen content. Carbon and hydrogen were determined using Vario EL III analyzer. Characterization of Naphthalene acetic acid Commercially available and chemically pure naphthalene acetic acid purchased was used as ligand in the present study. Experimental Techniques Synthesis of metal complexes of Naphthalene acetic acid Preparation of Cobalt (II) Complex A weight of 2.38g of hydrated Cobalt (II) chloride (0.01 M) was taken in a 100 ml beaker and dissolved in 25ml of hot distilled water. An amount of 5.58 g of NAA (0.03 M) was taken in another 100ml beaker and dissolved in 25ml of hot ethanol. The clear solution of the ligand was added to the solution of the metal salt in small quantities with constant stirring for 10 minutes. A pink coloured solid complex separated from the solution. It was filtered, washed repeatedly with ethanol and finally with solvent ether. The complex was dried and stored in a vacuum desiccator. The same procedure was adopted for the preparation of Cu(II) , Ni(II) and Hg(II) complexes. Estimation of Cobalt Cobalt was estimated gravimetrically. Appropriate amounts of mercuric chloride and ammonium thiocyanate were added to the cobalt solution. A blue coloured solid complex Hg[Co(SCN)4] separated out. From the weight of the complex the weight of cobalt was calculated. Estimation of copper Copper was estimated iodometrically.To the copper solution ammonium hydroxide was added to form pale blue precipitate. It was dissolved in acetic acid and nearly 2g of solid potassium iodide was added and mixed well and then the liberated iodine was titrated against standardised sodium thiosulphate. 2ml of starch solution was added to get the end point. The end point was the disappearance of blue colour. From the titre value the amount of copper was calculated. Estimation of Nickel Nickel was estimated gravimetrically as follows. To the clear solution 5ml of 1:1 HCl was added and the solution was diluted to 100ml with distilled water. The solution was then heated to about 80° C. To the hot solution about 20 ml of 1% alcoholic solution of dimethyl glyoxime reagent was added in drops with constant stirring. Immediately dilute ammonia solution was added drop wise directly to the solution to make it alkaline. A rosy red precipitate of nickel dimethyl glyoximate complex was obtained. The precipitate was digested on water bath for about an hour and the precipitate was allowed to settle. The precipitate was filtered, washed with hot water and dried in an air oven, cooled in desiccator and weighed. From the weight of the dimethyl glyoximate complex, the weight of nickel was calculated. Results and Discussion Naphalene acetic acid (NAA), a new base derived from naphthalene contains two oxygen atoms as potential donor atoms. It is pertinent to study how the NAA binds with the metal atom, when it is interacted with a transition metal salt. Hence, the new base NAA was purchased and used as a ligand. Analytical results The results of elemental analysis on NAA and its complexes are furnished in Table 4.1.The percentage compositions of NAA and its complexes indicate their empirical formulae. Characterization of NAA The commercial product of NAA was purified and then characterized by melting point, elemental analysis, infrared, UV and H-NMR spectra. The results of elemental analysis of NAA are provided in (Table 4.1). The important vibrational frequencies are listed in (Table 4.2). The H-NMR resonance signals are listed in( Table 4.3). A perusal of the IR spectrum shows a medium strong absorption band at 3434 cm which attributed to the carboxylic OH group. The absorption band found at 3060 cm is ascribed to the aromatic CH vibration and that at 2916 cm is due to aliphatic CH absorption. The absorptions found in the range 16961510 cm may be due aromatic C=C stretch as well as the carboxylic carbonyl group. The free ligand NAA multiplet signals found at δ7.9667.246 ppm are ascribed to the aromatic protons and the signal seen at δ 4.073 ppm is due to the protons of the CH2 group. The chemical shift due to the carboxylic proton (COOH) is expected to be observed at δ1014ppm. Since the spectrum was scanned in the δ range -0.5 to 9.5ppm this particular signal was not located. Characterization of Co (C12H9O2)2.2H2O This pink coloured complex having 1:2 metals: ligand stoichiometry may have cobalt in +2oxidation state. During the interaction Co chloride with NAA the carboxylic acid might have ionized to give the carboxylate anion which combine with Co to give the pink complex Co (C12H9O2)2. The elemental analysis (Table 4.1) and conductivity measured in ~ 10M DMF solution confirm the same. Research Article [Ananthalakshmiet al., 4(5): May, 2013] CODEN (USA): IJPLCP ISSN: 0976-7126 Int. J. of Pharm. & Life Sci. (IJPLS), Vol. 4, Issue 5: May: 2013, 2672-2679 2674 The free acetate ion (CH3COO ) shows absorption at 1560 and 1416cm which are attributed to υa (COO ) and υs (COO ) respectively. Considering the NAA ion, the band at 1410 cm-1 may be due to symmetric υs (COO) vibrations. In the case of the cobalt (II) complex these respective absorption bands are observed at 1511 and 1410 cm-1. The difference (∆) between the asymmetric and symmetric bands of free NAA is at a much higher value of 189cm where as in the complex spectrum, ∆ is much lower at 100cm indicating bidentate chelation of the corboxylate ligand to Co ion. A perusal of the electronic spectrum of the Co complex shows several bands due to d-d transition, charge transfer and ligand origin. A very weak absorption at 524.7nm (ie19058 cm) may be attributed to T2g (F) → T1g (P) transition. Another weak absorption band found at 651.2nm (15356cm) is attributed to T2g (F) → A2g (F) transition. A strong band found at 297nm (33670cm-1) may be due to charge transfer transition. The effective magnetic moment measured at room temperature for the CO ion is 4.8 B.M. Hence on the basis of chemical analysis, infrared and electronic spectra and magnetic moment the cobalt (II) complex is proposed to have an octahedral stereochemistry. Characterization of Ni (C12H9O2)2.2H2O The green coloured nicked (II) complex on elemental analysis is found to have 1:2 stoichiometry. Very low electrical conductivity value indicate the complex to be a nonelectrolyte. An examination of IR spectrum of this shows the appearance of υa (COO ) at 1510 cm and that υs (COO ) at 1410 cm. The difference between the symmetric and anti symmetric absorption is at 100 cm which much less than the free ion (NAA) value (189cm) this spectral feature indicates the bidentate chelation of the carboxylate ligand. Also the far IR absorption band seen at 540 cm may be due to υ(Co-O). The IR spectrum also shows bands at 3391(lr), 1631, 801, and 625 cm which are attributed to the presence of coordinated water molecules. The band found at 540 cm is ascribed to the (NiO) stretching vibration. The electronic spectrum of the Ni II complex shows an absorption at 24814 cm (403 nm) which is attributed to A2g (F) → T1g (P) transition, another band at 13405 CM (746 nm) due to A2g (F) → T1g (F) and a third band at 9814 CM (1019 nm) due to A2g (F) → T1g (F) transition. These absorption bands are indicative of an octahedral symmetry of Ni II in the complex. The μeff value measured at 2.84 B.M is also supportive of octahedral geometry. Hence based on analytical conductivity and magnetic data and IR and UV-visible spectroscopy a bidentate chelation of the organic ligand and octahedral stereochemistry is proposed to this complex. Characterization of Cu (C12H9O2)2.2H2O On the basis of chemical and elemental analysis this complex is given 1:2 stoichiometry. The very electrical conductance measured for this complex reveals that the complex in non-ionic. The IR spectrum indicates the presence υa (COO ) and υs (COO ) vibrational frequencies at 1511 and 1329 cm respectively. The difference between these two is much higher than expected for bidentate chelation mode of coordination of NAA ligand. Presence of water in the coordination sphere is indicated by IR bands at 3466 (br), 1599,79 (split) and 625 cm. The band at 511 cm also points to the binding of Cu and O atoms. The green coloured Cu complex measures an electronic absorption band at 11509 CM (868.86 nm) which is attributed to Eg→ T2g (F). It also exhibits another band at 32159 cm (310.95 nm) which may be due to charge transfer transition. The complex has a μeff value of 1.45 B.M per Cu atom at room temperature. The very low value of μeff may be due a coupling of the unpaired electrons one on each Cu II ion. Hence based upon the chemical and elemental analysis, conductivity, magnetic moment, IR and electronic absorption spectra, this complex is given a carboxylato bridged binuclear structure where there is antiferromagnetic interaction between two copper ions. Characterization of Hg (C12H9O2)2.2H2O Analysis shows that the mercury complex has 1:2 stoichiometry. The electrical conductivity measurement shows that it is a non-electrolyte. Investigation of its IR spectrum points to the fact that the carboxylato anion as a chelating bidentate ligand. The υa(COO ) appears at 1511 cm and the υs(COO ) appears at 1410 cm. The difference between the two is 101 cm which is very low indicating bidentate chelation to the metal ion. Also the appearances of bands at 3448, 1599, 801 and 625 cm are attributed to the presence of coordinated water molecules. Further, the far IR absorption at 400 cm which is due to Hg-O stretching vibration may also indicate the coordination of the carboxylate anion and H2O molecules .There is no magnetic and electronic spectral criterion for the bonding in d system. Hence, on the basis of other physicochemical data a 6 – coordinated structure is proposed for this complex also. Conclusion This work embodies the results on the investigation of coordinating nature of 1naphthalane acetic acid with Research Article [Ananthalakshmiet al., 4(5): May, 2013] CODEN (USA): IJPLCP ISSN: 0976-7126 Int. J. of Pharm. & Life Sci. (IJPLS), Vol. 4, Issue 5: May: 2013, 2672-26792675transition metals[Co(II), Ni(II), Cu(II), Hg(II)] .Itdetails on transition metal ion complexes withreference to cobalt (II), nickel (II), copper (II) andmercury (II) ions, the biological importance ofnaphthalene acetic acid and a review on metalcomplexes of carboxylates and related compounds.Itgives the details of the experimental techniquesemployed for the structural characterization of thecomplexes isolated. The experimental techniquesinclude electrical conductivity and magneticmeasurements, IR, UV-visible and H NMRspectroscopy, elemental and chemical analysis.Thiswork outlines the discussion of the results obtained. Onthe sphysico–chemical data obtained the bondingatoms are fixed and the stereochemistry assigned for allthe complexes. All the complexes have 1:2stoichiometry. All of them have two coordinated watermolecules each. In the Co, Niand Hgcomplexes, thecarboxylate ligland acts as a chelating bidentate and inCucomplex, it is bridging bidentate. The very lowmagnetic moment determined in the case of Cucomplex suggests a binuclear bridged structure. Themetal ions in all the complexes studied are in anoctahedral environment. References1. Gurudeepraj, “Advanced Inorganic chemistry”,vol.II sixth Edn, Goel Publishing house p-675(1997).2. F.A.Cotten and G.Wilkinson, “AdvancedInorganic chemistry”, 3 Edn, Willey EasternLtd., p-802(1989).3. N.Akhmetov, “Inorganic chemistry” First Edn.MIR Publications Mascow, p-94(19734. B.R.Puri, L.R.Sharma and K.C.Kalia,“Principles of Inorganic chemistry”, S.Chand&Co, P-817(1996).5. L.Birkenback and K.Kellerman, chem.Ber.58(1786) 2377(1925).6. D.L.Kerpert in “Comprehensive coordinationchemistry”, ed.G.Wilkinson, R.D.Gillard andJ.A.Mccleverty, Pergamm press, Oxford, vol.2,p-79(1987).7. S.D. Robinson and M.F. Uttley, J. Chem. Soc.,1912 (1973).8. T.A. Stephenson and G. Wilkinson, J.Inorg.Nucl.Chem. 29, 2122 (1967).9. G. Csontos, B.Heil and C. Marko. J.Organometal. Chem., 37, 183 (1972).10. A.V.R. Warrier and P.S. Narayanan,Spectrochim. Acta, 23A, 1061 (1967).11. A.V.R. Warrier and R.S. Krishnan,Spectrochim. Acta, 27A, 1243 (1971).12. K. Nakamato, Y.Morimoto, and A. E. Martell.J. Am. Chem. Soc., 83, 4528 (1961).13. T. Gaspar, C. Keveks, C. Penel, H. Greppin, D.M. Reid, and T. A. Thorpe, “Plant hormonesand plant growth regulators in plant tissueculture,” In Vitro Cellular and DevelopmentalBiology—Plant, vol. 32, no. 4, pp. 272–289,1996. View at Scopus.14. P. H, Moura-Costa, and L. Lundoh, “Theeffects of auxins (IBA, NAA and 2,4-D) onrooting of Dryobalanops lanceolata (kapur,Dipterocarpaceae) cuttings,” Journal ofTropical Forest Science, vol. 7, no. 2, pp. 338–340, 1994.15. M. Katayama, “Synthesis and biologicalactivities of 4-chloroindole-3-acetic acid andits esters,” Bioscience, Biotechnology, andBiochemistry, vol. 64, no. 4, pp. 808–815,2000. View at Publisher · View at GoogleScholar.16. T. Ulven, J. M. Receveur, M. Grimstrup et al.,“Novel selective orally active CRTH2antagonists for allergic inflammationdeveloped from in silico derived hits,” Journalof Medicinal Chemistry, vol. 49, no. 23, pp.6638–6641, 2006. View at Publisher · View atGoogle Scholar · View at Scopus Research Article[Ananthalakshmiet al., 4(5): May, 2013] CODEN (USA): IJPLCPISSN: 0976-7126 Int. J. of Pharm. & Life Sci. (IJPLS), Vol. 4, Issue 5: May: 2013, 2672-26792676Table 1: Analytical Results on IAA and its Metal Complexes FIG. 4.2 H-NMR spectrum of NAAS/ No. Compound%Cfound (expected)% Hfound (expected)% Mfound (expected) 1IAA(C10H9NO2)76.49(77.41)5.32(5.37)2 Co(C10H8NO2)2.2H2O62.20(61.94)4.62(4.73)12.74(12.68) 3 Ni(C10H8NO2)2.2H2O62.42(61.81)4.82(4.72)13.06(12.86) 4 Cu(C10H8NO2)2.2H2O61.46(61.33)4.96(4.69)13.88(13.53) 5 Hg(C12H9O2) .2H2O47.98(47.48)3.68(3.63)33.70(33.07) Research Article[Ananthalakshmiet al., 4(5): May, 2013] CODEN (USA): IJPLCPISSN: 0976-7126 Int. J. of Pharm. & Life Sci. (IJPLS), Vol. 4, Issue 5: May: 2013, 2672-26792677Table 2: Infrared Spectral Bands of NAA Complexes (cm) Table 3: Proton NMR chemical shifts of NAA and its mercury complex (in ppm) Table 4: Magnetic and Electronic Spectral Data on NAA metal Complexes Complexμeff (BM)(Colour)Absorption bands(cm)Electronic transition Co(NAA)2. 2H2O4.80(Pink)190581535633670T2g(F)→T1g(P)T2g(F)→A2g(F)Charge transfer. Ni(NAA)2 . 2H2O2.84(Green)24814134059814A2g(F)→T1g(P)A2g(F)→T1g(F)A2g(F)→T2g(F) Cu(NAA)2. 2H2O1.45(Green)1150932159Eg→ T2g(F)Charge transfer. Fig. 4.4: UV Spectrum of Co (C12H9O2)2.2H2OCompoundυa(co2 )υs(co2 ) ∆υ