Bajopas Volume 11 Number 1 June, 2018 http://dx.doi.org/10.4314/bajopas.v11i1.29 Bayero Journal of Pure and Applied Sciences, 11(1): 168 - 173 Received: January, 2018 Accepted: May, 2018 ISSN 2006 – 6996 SYNTHESIS AND CHARACTERISATION OF SOME MIXED LIGANDS ADDUCTS OF BENZOYLACETONE AND SALICYLALDEHYDE Abdullahi Mustapha,1 Muhammad Saleh Salga2 and Sani Sabo3 Department of Chemistry, Federal University Dutse.(1) Department of Pure and Industrial Chemistry Umaru Musa Yar’adua University Katsina (2)(3) Correspondence author: sani.sabo@umyu.edu.ng ABSTRACT A series of four mixed ligand complexes were synthesized by reacting benzoylacetone and salicylaldehyde with different metal chlorides in ethanolic medium. The complexes have been characterized by molar conductance measurements and spectral techniques such as IR and Uv-visible electronic spectra. Decomposition temperature was also determined. The results indicated that the compounds have bands at 400-500cm-1, with very sharp melting points. This proved the formation of metal-oxygen bond, purity and high thermal stability of the compounds that could lead to a high antimicrobial activity. Keywords: Adduct Synthesis, Ligands, and Complexes INTRODUCTION The chemistry of mixed ligand complexes has received interest in recent decades due to the wide applications of coordination compounds in various fields. Mixed ligand complexes appeared to be relevant in biological fluids, create specific structures and manifest themselves as enzyme-metal ion-substrate complexes (Reddy et al 2005). N-Anilinoacetohydrazobenzoylacetone (H2L) and their manganese(II), cobalt(II), nickel(II), copper(II) and zinc(II) complexes have been synthesized and characterized by IR, electronic spectra, molar conductivities, thermal analyses and magnetic susceptibilities. Binuclear complexes with molar ratios of (M:L) = 2:1 are formed. The IR spectra of these compounds showed that the ligand (H2L) coordinates to the metal ions in a tetradentate manner with O2N2 as donor sites in Mn(II), Co(II), Ni(II) and Zn(II) complexes while in the Cu(II) complexes the ligand coordinated as bidentate via N and O donor atoms. The copper(II) complexes, also, shows higher antibacterial activity towards gram positive (G+) bacteria Bacillus subtilis than the ligand and other complexes while Mn(II) complex shows higher antifungal activity than the free ligand (Kashar, 2014). Aliyu and Mustapha (2009) reported the synthesis of some oxovanadium (IV) complexes of acetylacetone, dibenzoylmethane, 2thionyltrifluoroacetone, Triflouroacetylacetone and benzoylacetone. The complexes were characterized by elemental analysis, molar conductance, decomposition temperature, solubility and infrared spectral studies with 1:2 M:L ratio. Dinuclear complexes from salicylaldehyde and 2aminophenol with Cu(II), Ni(II) and Co(II) and Fe(III) were synthesized and characterized by IR, UV-visible 168 and elemental analysis. The mass spectral data obtained was in good agreement with the result obtained from the thermogravimetric analysis (TGA) in accordance with its fragmentation pattern (Bhatt, 2008). The magnetic properties of these complexes were studied and the probable mechanism for the formation of the complexes was proposed. MATERIALS AND METHODS Materials: Benzoylacetone (Aldrich), Salicylaldehyde (Aldrich), Manganese (II) Chloride, Iron (III)Chloride (lobachem), Nickel (II) chloride, copper(II) chloride, ethanol (Glanson chemicals ltd), chloroform (cartvalues ltd), solvents were AnalaR and were used as supplied. Analytical methods and Physical measurements: The compounds were analyzed for IR using CARY 630 FT-IR, thermo Nicolet instrument in the range of 4004000. The UV spectral measurements was carried out using T60 spectrophotometer The solubility of each metal complex was tasted using various non-polar solvents like hexane and distilled water. While the polar solvents includes chloroform, acetic acid, acetone etc. Molar conductances were measured at room temperature in DMSO using digital conductivity meterT60. The melting points of the complexes were also carried out using Barnstead electronic thermal -IA9110. Synthesis of Copper (II) complex with mixed ligand To an ethanolic solution (10 ml) of CuCl2.2H2O (5.24 mmol, 0.893g), an ethanolic solutions (10 ml) of benzoylacetone (5.24 mmol, 0.85g) and salicyaldehyde (5.24 mmol, 0.64g) were added with constant stirring. The reaction mixture was stirred for about 40 minutes. The precipitate formed was filtered, washed with ethanol and dried under reduced pressure. (Agrawal, etal 2003) Bajopas Volume 11 Number 1 June, 2018 Synthesis of Manganese (II) complex with mixed ligand To an ethanolic solution (10 ml) of MnCl2.4H2O (5.24 mmol, 1.03g), an ethanolic solution (10 ml) of benzoylacetone (5.24 mmol, 0.85g) and salicyaldehyde (5.24 mmol, 0.64g) were added with constant stirring. The reaction mixture was stirred for about 40 minutes. No precipitate was obtained. Then, few drops of Triethylamine solution (4 ml) was added drop wise to the above reaction mixture to raise the pH to 6.0. The solution was stirred and refluxed for 3-4 hrs and the reaction mixture was kept at room temperature. The solution, was filtered, washed with ethanol and dried properly under reduced pressure. (Agrawal, et-al 2003) Synthesis of Nickel (II) complex with mixed ligand To an ethanolic solution (10 ml) of NiCl2 (5.24 mmol, 0.68g), an ethanolic solution (10 ml) of benzoylacetone (5.24 mmol, 0.85g) and salicyaldehyde (5.24 mmol, 0.64g) were added with constant stirring. The reaction mixture was stirred for about 40 minutes. No precipitate was obtained. Then, few drops of Triethylamine solution (4 ml) was added drop wise to the above reaction mixture to raise the pH to 6.0. The solution was stirred and refluxed for 3-4 hrs and the reaction mixture was kept on room temperature. The precipitate was settled down. The solution, was filtered, washed with ethanol and dried properly under reduced pressure. (Agrawal, et-al 2003) Synthesis of Iron (III) complex with mixed ligand To an ethanolic solution (10 ml) of FeCl3.6H2O (5.24 mmol, 0.85g), an ethanolic solution (10 ml) of benzoylacetone (5.24 mmol, 0.85g) and salicyaldehyde (5.24 mmol, 0.64g) were added with constant stirring. The reaction mixture was stirred for about 40 minutes. No precipitate was obtained. Then, few drops of Triethylamine solution (4 ml) was added drop wise to the above reaction mixture to raise the pH to 6.0. The solution was stirred and refluxed for 3-4 hrs and the reaction mixture was kept on room temperature. The resulting solution, was filtered, washed wit ethanol and dried properly under reduced pressure (Agrawal et al., 2003). RESULTS AND DISCUSSION Table 1 provides some of the physical parameters that serves as supporting evidence for the proposed complexes. Mixed ligand complexes of Cu (II), Fe (III), Mn (II), and Ni (II) have been prepared by the reaction of manganese (II) chloride tetrahydrate , ferric (III) chloride hexahydrate, nickel(II) chloride, zinc(II) chloride with the ligands Salicylaldehyde and Benzoylacetone in 1:1:1 ratio. The resulting synthesized complexes were coloured solids and have a relatively high decomposition point. The complexes of copper (II), Iron (III), Manganese (II) and Nickel (II) gave decomposition temperatures of 235oC, 220oC, 239oC and 239oC respectively. These high decomposition temperatures revealed that the complexes are thermally stable. However, the complexes appeared to have dark brown, reddish, light orange and pale green colours respectively. The complexes showed variable solubilities in different solvents with very few showing slight solubility in the same solvent used. However, all the complexes were soluble in DMSO (Table 2) being it a polar aprotic solvent, it has the ability to dissolve a wide range of solutes and also has a high di-electric constant. Being DMSO the only solvent that can dissolve the compounds, it was used to measure the molar conductivities of the compounds at 10-3 M solutions (Table 4). The results of conductivity measurements showed that the Mn(II), Fe(III), Ni(II) and Cu(II) complexes, have values in the range 49–90.6 Ω-1 mol-1 cm2. This indicates that they are non-electrolytes, the slight increase in the conductance values observed, may be due to some solvolysis or dissociation (El-Qisairi et al., 2007). Moreover, it is reported that, in a complex, the positive charge of the metal is partially shared with the donor atoms present in the ligand, and there may be π-electron delocalization over the whole complex (Sanap et al., 2013). The UV-visible spectra of the mixed ligand complexes were also recorded in DMSO in the region 300 to 600nm. All the complexes showed peaks in the UV region with wavelengths in the range 300-400nm this may be assigned to the π-π* transition of the chromophores, while bands above 400nm may be assigned to charge transfer transition (Table 4). The above Uv-visible results of the complexes conformed to the literature report by (Mustapha et al., 2014). In addition, the IR spectra of all the complexes have been studied and assignments were given to the manifested bands regions. The complexes of Fe(III), Mn(II) and Cu(II) showed absorption at the bands regions of 2080cm-1 , 2143cm-1 and 2119cm-1 respectively, this can presumably be attributed to the aromatic v(C-H) stretching (Malathy, 2004). The strong intensity bands that appeared at 1624cm-1 for Mn(II), 1617cm-1 for Fe(III), 1624cm-1 for Ni(II) and Cu(II) cm1 are assigned to v(C=O) stretching vibration (Halli et al., 2012). A band in the region 1419-1522cm-1 can be ascribed to v(C=C) bond. This can be presumed that the anionic ligand is coordinated to metal in the tautomeric form (Ahmadzadeh et al., 2014) as shown in Table 3 Bands for v(M-O) were observed in the spectra of Cu(II) complex at 419cm-1 , Fe(III) at 472cm-1 region, Ni(II) complex at 419cm-1 and Mn(II) at 419cm1 . This complied with the reported literature (Dnyaneshwar et al., 2014). Therefore, from the IR spectra it is concluded that the ligands behaved as monobasic or neutral ligands coordinated to the metal ion via carbonyl oxygen of benzoylacetone and enolic oxygen of the salicylaldehyde as shown in the diagram below. 169 Bajopas Volume 11 Number 1 June, 2018 Table 1: Physical measurements S/N Compound Empirical Formula Mwt. M.P (OC) 1 Mn(II) complex Fe(III) Complex Ni(II) complex Cu(II) complex [MnC17H15ClO4] 373.00 [FeC22H15Cl3O5] [NiC17H15ClO4] [CuC17H15ClO4] 2 3 4 %C found %H found %Cl found %O found % M. found Color 239 Cond. Λ, Ω-1 mol-1 cm2 52.9 54.64 4.05 9.49 17.13 14.74 408.97 220 90.6 49.79 3.69 17.29 15.61 13.62 377.44 382.30 239 235 51.2 49.6 54.10 53.42 4.01 3.95 9.39 9.27 16.96 16.74 15.55 16.62 Light Orange Reddish Brown Pale green Dark brown Key; Mwt: Molecular weight, Cond: Conductivity Table 2: Solubility of the complexes. Solvents Cu(II) complex Distilled water Ethanol Methanol Acetone Chloroform N-hexane Dimethylsulfoxide S= Soluble, SS= slightly Fe(III) complex S IS IS SS S SS S S S SS S SS S S soluble, IS=Insoluble Mn (II)complex S S S S S S S 170 Ni (II)complex SS S S SS SS S S Bajopas Volume 11 Number 1 June, 2018 Table 3: Infrared spectra data of the complexes Compounds v(C=O)cm-1 v(C=C)cm-1 v(C-H)cm-1 v (M-O)cm-1 [MnL1] (C17H15ClO4) 1624(s) 1419(s) 2143(m) 419(w) [FeL2] (C22H15Cl3O5) 1617(s) 1522(s) 2080(m) 472(w) [NiL3] (C17H15ClO4) 1624(s) 1457(W) - 419(w) [CuL4] (C17H15ClO4) 1624(s) 1510(m) 2119(b) 456(m) Key; S=strong, m=medium, b=broad Table 4: Uv-visible spectral data of the complexes Wave Cu(II) complex Fe(III) complex S/N length (nm) Absorbance Absorbance Mn(II) complex Absorbance Ni(II) complex Absorbance 1 300 0.255 0.235 0.442 0.222 2 320 0.232 0.212 0.345 0.232 3 340 0.212 0.215 0.331 0.205 4 360 0.225 0.477 0.206 0.324 5 380 0.354 0.244 0.285 0.424 6 400 0.476 0.213 0.124 0.357 7 420 0.205 0.173 0.164 0.259 8 440 0.234 0.127 0.163 0.171 9 460 0.324 0.124 0.122 0.288 10 480 0.166 0.164 0.145 0.211 11 500 0.134 0.163 0.155 0.123 12 520 0.114 0.146 0.255 0.135 13 540 0.222 0.155 0.145 0.112 14 560 0.184 0.224 0.112 0.132 15 580 0.127 0.174 0.178 0.112 16 600 0.139 0.167 0.224 0.121 Figure 1: proposed structure of the complexes where ‘M’ represents the divalent transition metals (Cu, Mn, and Ni) 171 Bajopas Volume 11 Number 1 June, 2018 Figure 2: proposed structure of the complex with Fe (III) as the central metal CONCLUSION This paper has reported a series of four mixed ligand complexes synthesized by the reaction of benzoylacetone and salicylaldehyde with suitable metal chlorides in ethanolic medium. 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