Conductometric Study of Complex Formation Between Cu (II) Ion and 2-hydroxyimino-3-(2'-hydazonopyridyl)-butane (HL)

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1 Frontiers in Science 2012, 2(4): 76- DOI: /j.fs Conductoetric Study of Coplex Foration Between Cu (II) Ion and 2-hydroxyiino-3-(2'-hydazonopyridyl)-butane (HL) E A. Goaa *, K. M. Ibrahi, N. M. Hassan Cheistry Departent, Faculty of Science, Mansoura University, 35516, Mansoura, Egypt Abstract The association constant,foration constants and Gibbs free energies are calculated fro the conductoetric titration curves of CuCl 2 with 2-hydroxyiino-3-(2 -hydazonopyridyl)-butane (HL) in absolute ethanol at different teperatures( K, K, K and k). On drawing the relation between olar conductance and the ratio of etal to ligand concentrations, different lines are obtained indicating the foration of 1:2, 1:1 and 2:1 (M:L) stoichioetric coplexes. The foration constants of different coplexes in absolute ethanol follow the order: K f (2:1) K f (1:1) > K f (1:2) for (M: L). As the teperature increases, the foration constants and association constants of different coplexes increase. The enthalpy and entropy of foration and association of CuCl 2 with HL were also estiated and their values were also discussed. The solvation free energies ( G s ),Enthalpy changes of solvation ( H s )and the entropy of salvation ( S s ) were also calculated fro solubility easureents for 2-hydroxyiino-3-(2- hydrazonopyridyl)-butane (HL) at different teperatures ( K, K, K and K). Keywords Solvation Association Constants, Foration, Gibbs Free Energies, Solvation Free Energies, Enthalpy Changes of 1. Introduction Schiff bases hydrazone derivatives and their etal copl exes have been studied for their interesting and iportant properties, e.g., antibacterial[1,2], antifungal[3], antioxidant [4], anticancer[5] and catalytic activity in oxidation of cyclohexene[6]. Moreover, Schiff bases hydrazone derivati ves are versatile ligands and they offer the possibility of different odes of coordination towards transition etal ions. Also, soe of these derivatives have been applied as iron chelate or drugs in therapy of anaeia[7] and treatent of neuropathic pain[8]. Therefore it propted us to study Schiff base transition etal coplexes. Transition etal ions have a strong role in bio-inorganic cheistry and redox enzye systes and ay provide the basis of odels for active sites of biological systes[9]. Copper (II) ion is a biologically active, essentialon, cleating ability and positive redox potential allow participation in biological transport reactions. Cu(II) coplexes possess a wide range of biological activity and are aong the ost potent antiviral, antituor and anti * Corresponding author: esa_1947@hotail.co (E. A. Goaa ) Published online at Copyright 2012 Scientific & Acadeic Publishing. All Rights Reserved inflaatory agents[10]. Schiff base transition etal coplexes have been extensively studied because of their potential use as catalysts in a wide range of oxidation reactions[11 14]. In recent years any copper, nickel and anganese coplexes of Schiff bases were prepared and characterized by several techniques[15, 16]. 2. Objectives This work deals with the deterination of solvation free energies ( Gs),enthalpy changes of solvation( Hs) and the entropy of solvation ( Ss) fro solubility easureent and identification of coordination behaviour of Schiff base ligand HLtowards CuCl 2.and the deterination of the therodyna ic stability constants and therodynaic functions using the conductoetric technique. Thus, therodynaic studies of coplexation reactions of this Schiff base with transition etal ions not only result in iportant inforation on the therodynaics of coplexation reaction, but also lead to a better understanding of the high selectivity of this ligand towards different etal cations. The ai of this work the evaluation the non-covalent behavior of CuCl 2 with 2-hydroxyiino-3-(2'-hydazonopyr idyl)-butane (HL) in absolute ethanol solutions at K. These non-covalent interactions can help us for analysis of salts in bodies and environneent[17].

2 Frontiers in Science 2012, 2(4): Methods 3.1. Materials Schee 1. The outline of the synthesis of 2-hydroxyiino-3-(2'-hydrazonopyridyl)-butane (HL) All anipulations were perfored under aerobic conditions. The cupper chloride and the used reagents were Merck pure Preparation of HL 2-hydroxyiino-3-(2'-hydrazonopyridyl)-butane (HL) (schee 1) was prepared by boiling an EtOH solution of 2-hydrazino pyridine (Aldrich) with 2, 3-butanedione onoxie (1:1) under reflux. The product was recrystallised fro hot absolute EtOH[ 18]. (M.p: 220 ; yield %). The purity of the copound was checked by TLC Conductoetric Measureent The conductoetric titration of the CuCl 2 (1x10-4 ) ole/l against the ligand (1x10-3 ) ole/l in absolute ethanol was perfored with 0.2 l interval additions fro HL solution. The specific conductance values were recorded using conductivity bridge ADWA, AD 3000 with a cell constant equal to 1 c -1. The teperature was adjusted at K, K, K and K 3.5. Solubility Measurent Saturated solutions of HL were prepared by dissolving an excess aount of the solid substances in 10 l. of the corresponding solvent ixtures, using closed test tubes. The solutions were vigorously shaken in a therostatic water-ba th at the desired teperature. The olal solubilities of the HL were analysed by drying 1l. of the saturated solutions in sall aluiniu dishes. Evaporation of the solvent was perfored carefully and slowly under a tungsten lap to prevent any loss in salt weight. Solubility value was taken as an average of three consecutive independent easureents. 4. Results and Discussion 4.1. Association Constants The specific conductance values (K s ) of different concentrations of CuCl 2 in absolute ethanol were easured experientally in absence and in the presence of ligand at different teperatures ( K, K, K and K). The olar conductance (/\ ) values were calculated[19] using equation (1): ( Ks Ksolv ) Kcell 1000 Λ = C (1), where K s and K solv are the specific conductance of the solution and the solvent, respectively; K cell is the cell constant and C is the olar concentration of the CuCl 2 solutions. The liiting olar conductances (/\ M ) at infinite dilutions

3 78 E A. Goaa et al.: Conductoetric Study of Coplex Foration Between Cu (II) Ion and 2-hydroxyiino-3-(2'-hydazonopyridyl)-butane (HL) were estiated for CuCl 2 in absolute ethanol alone at different teperatures by extrapolating the relation between /\ and C ½ to zero concentration as shown in Fig.(1). The liiting olar conductances (/\ o ) at infinite dilutions were estiated for CuCl 2 in the presence of the ligand (HL) by extrapolating the relation between /\ and C ½ to zero concentration Fig. (2) By drawing the relation between olar conductance (/\ ) and the olar ratio of etal to ligand (M/L) concentrations (Fig. (3), (4), (5), (6)), different lines are obtained with sharp breaks indicating the foration of 1:2, 1:1 and 2:1 (M:L) stoichioetric coplexes. 90 /\ 75 CuCl 2 +HL /\ K K K K Figure 3. The relation between /\ and M/L (CuCl 2-HL) at K /\ M/L CuCl 2 +HL C ½ Figure 1. The relation between olar conductance (and\ ) and (C ½ ) of CuCl 2 alone in absolute ethanol at different teperatures (293.15K, K, K and K) M/L /\ C ½ K K K K Figure 4. The relation between/\ and M/L (CuCl 2-HL) at K /\ 90 CuCl 2 +HL Figure 2. The relation between olar conductance (/\ ) and (C ½ ) of CuCl 2 in presence of HL in absolute ethanol at different teperatures (293.15K, K, K and K) M/L Figure 5. The relation between /\ and M/L(CuCl 2-HL) at K

4 Frontiers in Science 2012, 2(4): /\ CuCl 2 +HL M/L Figure 6. The relation between /\ and M/L (CuCl 2-HL) at K The experiental data of (/\ M ) and (/\ o ) were analyzed for the deterination of association and foration constants for each type of the stoichioetric coplexes. The association constants of CuCl 2 in the presence of ligand (HL) in absolute ethanol at different teperatures ( K, K, K and K) for 2:1,1:1 and 1:2 (M:L) were calculated by using equation[20,21]: K A Λ ( Λ Λ) = 4 C S( z) Λ (2), where (/\, /\ 0 ) are the olar and liiting olar conductance of CuCl 2 in presence of Hl respectively; C is olar concentration of CuCl 2, S(Z) is Fuoss-Shedlovsky factor, equal with unity for strong electrolytes[22]. The calculated association constants are shown in Table (1) Gibbs Free Energies of Association The Gibbs free energies of association (ΔG A ) were calculated fro the association constant[23, 24] by applying equation: Δ G A = - R T ln K A (3), where R is the gas constant (8.341 J) and T is the absolute teperature.the calculated Gibbs free energies were presented in Table (2) The Foration Constants for Coplexes The foration constants (K f ) for CuCl 2 coplexes were calculated for each type of coplexes (1:2), (1:1) and (2:1) (M: L)[25, 26] by using equation: where /\ M is the liiting olar conductance of the CuCl 2 alone, /\ obs is the olar conductance of solution during titration and /\ ML is the olar conductance of the coplex. The obtained values (K f ) for CuCl 2 -ligand stoichioetric coplexes are presented in Table (3) (4) Table 1. Association constants of CuCl 2 with HL at different teperatures ( K, K, K and K) KA 9.52E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E+01 Table 2. Gibbs free energies of association of CuCl 2 with HL at different teperatures ( K, K, K and K) Δ G A(k J/ol) 9.52E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E+00

5 E A. Goaa et al.: Conductoetric Study of Coplex Foration Between Cu (II) Ion and 2-hydroxyiino-3-(2'-hydazonopyridyl)-butane (HL) Table 3. Foration constants for 1:2, 1:1 and 2:1 (M/L) coplexes in absolute ethanol at different teperatures ( K, K, K and K) K f 1 : 2 (M/L) 8.33E E E E E E E E E E E E E E E E E E E E E E E E E+04 1 : 1 (M/L) 9.09E E E E E E E E E E E E E E E E E E E E E E E E E+05 2 : 1 (M/L) 9.52E E E E E E E E E E E E E E E E E E E E E E E E E Gibbs Free Energies of Coplex Foration The Gibbs free energies of foration for each stoichioe tric coplexes were calculated by using the equation: ΔG f = - R T ln K f (5). The calculated ΔG f values are presented in Table (4) Enthalpies and Entropies The enthalpy (ΔH A ) for CuCl 2 coplexes were calculated for each type of coplexes (1:2), (1:1) and (2:1) (M:L) by using Van't Hoff equation[26,27] : Where R is the gas constant and T is the absolute teperature. By drawing the relation between log K A and 1/T, different lines are obtained indicating the foration of 1:2,1:1 and 2:1 (M:L) stoichioetric coplexes Fig.(7) Enthalpies and Entropies of Association Fro the relation between log K and 1/T, ΔH A can be calculated for each type of coplexes fro the slope of each line (-ΔH/2.303 R).The entropy (ΔS A ) for CuCl 2 coplexes were calculated for each type of coplexes (1:2), (1:1) and (2:1) (M:L) by using equation : ΔG = ΔH TΔS (7) Where (S) is the entropy of the syste. The calculated values of (ΔH A ) and (ΔS A ) for CuCl 2 -lig and stoichioetric coplexes are presented in Table (5): By drawing the relation between log K f and 1/T, different (6) lines are obtained indicating the foration of 1:2,1:1 and 2:1 (M:L) stoichioetric coplexes Fig.(8) Enthapies and Entropies of Coplex Foration The enthalpy (ΔH f ) for CuCl 2 coplexes were calculated for each type of coplexes (1:2), (1:1) and (2:1) (M:L) by using van 't Hoff equation. The calculated values of (ΔH f ) and (ΔS f ) for CuCl 2 -ligand stoichioetric coplexes are presented in Table (6): 4.8. Acivation Energies Since the conductance of an ion depends ainly on its obility, it is quite reasonable to treat the rate process taking place with the change of teperature on the basis of equation (8) : /\ 0 =A e -Ea/RT (8), where A is the frequency factor, R is the gas constant and Ea is the Arrhenius activation energy of the transfer process. Consequently, fro the plot of log /\ 0 vs. 1/T, the E a values can be evaluated[ 27] as shown in Fig (9). E a value is KJ/ol Soubility Measureent The solubility (S) of 2-hydroxyiino-3-(2'-hydazonopyrr idyl)-butane (HL) in (EtOH-H2O) ixtures at different teperatures (293.15, , and K) was deterined by gravietric technique. The results are illustrated in Table 1. Solubility was calculated as an average of the two experiental data. The olal solubility is

6 Frontiers in Science 2012, 2(4): calculated by using equation (9): Molal solubility (S) = W.1000/do.M g.ole /1000 g. solvent (9), where (W) is the weight of one l. of saturated solution, after its coplete evaporation in the aluinu dish under the effect of tungsten lap,(m) is the olecular weight of HL and (d o ) is the density of pure solvent used as it shown in Table (7) ; Fig.(10) the olal solubility was increased with the increase of the content of the organic solvent used (EtOH).This can be explained on the basis of the fact that like dissolve like as well as the lower and higher ion-solvent interactions. The olal solubility of HL was increased with the increase of teperatures Table 4. Gibbs free energies of foration of CuCl 2 with HL at different teperatures ( K, K, K and K) ΔG f (k J/ol) 1 : 2 (M/L) 8.33E E E E E : 1 (M/L) 9.09E E E E E : 1 (M/L) 9.52E E E E E :2 1:1 2: logk A /T Figure 7. The relation between (log K A) and (1/T)

7 82 E A. Goaa et al.: Conductoetric Study of Coplex Foration Between Cu (II) Ion and 2-hydroxyiino-3-(2'-hydazonopyridyl)-butane (HL) Table 5. The enthalpies and entropies of association of coplexes at different teperatures ( K, K, K and K) ΔH A(KJ/ol) and ΔS A(KJ/ol.K) 1 : 2 (M/L) Tep K K K K ΔHA ΔSA : 1 (M/L) Tep K K K K ΔHA ΔSA : 1 (M/L) Tep K K K K ΔHA ΔSA : Log K f /T Figure 8. The relation between (log K f) and (1/T) Table 6. The enthalpies and entropies of foration of coplexes at different teperatures ( K, K, K and K) ΔH f (KJ/ol) and ΔS f(kj/ol.k) 1 : 2 (M/L) Tep K K K K ΔHf ΔSf : 1 (M/L) Tep K K K K ΔHf ΔSf : 1 (M/L) Tep K K K K ΔHf ΔSf

8 Frontiers in Science 2012, 2(4): CuCl 2 +HL 2.54 log/\o Figure 9. The relation of (log /\ 0) and 1/T Table 7. The Molal solubility (S) of HL at different teperatures ( K, K, K and K) Vol. % of EtOH /T (S) of HL K K K K S(g.ole/1000 g.solvent) K K K K X S Figure 10. Variation of the olal solubility (S) of HL with the ole fraction (Xs) of EtOH at different teperatures

9 84 E A. Goaa et al.: Conductoetric Study of Coplex Foration Between Cu (II) Ion and 2-hydroxyiino-3-(2'-hydazonopyridyl)-butane (HL) Table 8. The solvation free energies ( G) S of HL in EtOH-H2O ixture at different teperatures ( K, K, Kand K) Vol. % of EtOH (ΔG) S (KJ/ol) K K K K (ΔH)s (KJ/ol) Therodynaics of Solvation The solvation free energies G S of HL in EtOH-H 2 O ixture at different teperatures( K, K, K and K) were calculated fro the solubility easureents by using the following equation (10): ( G) s = RT log K sp (10). The value of (log K sp ) depends ainly on the solvation of the solute in the solvent under investigation.in case of neutral copound (the activity coefficient is close to one), the values of (log K sp ) can be equal to log (S). The enthalpy changes of solvation( H s ) of HL in EtOH-H 2 O ixtures were calculated fro the plots of (log K sp ) versus (1/T),where the slope equals (- H s /2.303 R) using the following equation(11): log K sp = - ( H s ) / RT + constant (11) 5. Conclusions The stability constants for the coplexation of copper (II) ion with 2-hydroxyiino-3-(2'-hydazonopyridyl)-butane (HL) were deterined conductoetrically at different teperatures. Therodynaic paraeters of coplexation were deterined fro the teperature dependence of the foration constant. The negative values of G show the ability of the studied ligand to for stable coplexes and the process trend to proceed spontaneously. However, the obtained positive values of H eans that enthalpy is not the driving force for the foration of the coplexes. Furtherore, the positive values of S indicate that entropy is responsible for the coplexing process. The foration constants and Gibbs free energies of different coplexes follow that order: K f (2:1) K f (1:1) K f (1:2) for (M:L), and G f (2:1) G f (1:1) G f (1:2) for (M:L) REFERENCES [1] S.M Ea, F.A. El-Saied, S.A. Abou El-Enein, H.A. El-Shater, Spectrochi. Acta Part A 72 (2009) [2] A.R. Yaul, V.V. Dhande, A.S. Aswar, Rev. Rou. Chi. 55 (2010) [3] A.S. El-Tabl, F.A. El-Saied,W. Plass, A.N. Al-Haki, Spectrochi. Acta Part A 71 (2008) [4] Y. Li, Z.-Y. Yang, M.-F.Wang, J. Fluoresc. 20 (2010) [5] S.B. Desai, P.B. Desai, K.R. Desai, Heterocycl. Coun. 7 (2001) [6] M.S. Niasari, A. Airi, Appl. Catal. A 290 (2005) [7] M.C.R. Arguelles,M.B. Ferrari, F. Bisceglie, C. Plizzi, G. Pelosi, S. Pinelli,M. Sassi, J. Inorg. Bioche. 98 (2004) [8] P. Yogeeswari, N.Menon, A. Sewal,M. Arjun, D. Srira, Eur. J.Med. Che. 46 (2011) [9] M.V. Angelusiu, S.F. Barbuceanu, C. Draghici, G.L. Alajan, Eur. J. Med. Che. 45 (2010) ,F. W C Vosburg and G R Cooper, J.A. Che. Soc., 1941, 63, 437. [10] L. Canali, D.C. Sherrington, Che. Soc. Rev. 28 (1999) 93. [11] G.J. Ki, J.H. Shin, Catal. Lett. 63 (1999) [12] T. Katsuki, Coord. Che. Rev. 140 (1995) [13] K.J. O Connor, S.J.Wey, C.J. Burrows, Tetrahedron Lett. 33 (1992) [14] M.J. Saide, D.G. Peters, J. Electroanal. Che. 443 (1998) [15] Losada, I. Del Peso, L. Beyer, Inorg. Chi. Acta 321 (2001) [16] Zhibo Yang,, Ph.D. thesis, Wayne State University, Detroit, Michigan, USA., [17] Kaal M.Ibrahi, Magdy M.Bekhit and Gaber M.Abu EL-Reash (1991) Transition Met.Che, 16,

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