Research Journal of Chemical Sciences ______________________________________________ ISSN 2231-606X Vol. 1(7), 1-14, Oct. (2011) Res.J.Chem.Sci. International Science Congress Association 1 Metal Chelates of Hydrazone Ligand Chelating Tendencies of 2-Carboxyphenylhydrazoacetoacetanilide (2-Cphaaa) Ligand Mostafa M. Chemistry Department, Faculty of Education Ain Shams University Roxy, Cairo, EGYPTAvailable online at: www.isca.in (Received 22th June 2011, revised 15th July 2011, accepted 15th September 2011)Abstract The chelating properties, of hydrazone ligand 2-carboxyphenylhydrarzoacetoacetanilide (2-CPHAAA) (HL) have been studied. A series of binary complexes, of HL with the metal ions Cd(II), Cu(II), Co(II), UO (VI) and Th(IV) were prepared. The binary Cu (II) complexes of 2-CPHAAA was reacted with the ligands 1,10 –phenanthroline (1,10- phen) and 2-amino-4-methyl-pyridine (2 AMP) to form mixed ligand complexes. The structures of all complexes, were elucidated by elemental analyses, conductance, IR ,electronic absorption spectra , magnetic moment, 1HNMR and TG-DSC measurements. The metal –ligand stability constants of the Cu(II), Ni(II) , Co(II) , Zn (II) , Mn(II) , Cd(II) UO(VI), Th(IV) , Sm (III) and Er(III) chelates of 2-CPHAAA were determined in 75%(v/v) dioxane water medium at 10,20,30 and 40 C and µ = 0.10 M KNO. The thermodynamic parameters for the proton – ligand and metal ligand stability constants were obtained by the temperature coefficient method. The thermodynamic functions G and H of the complexes were analyzed in terms of electrostatic (el) and non electrostatic (non) components. The values of H non show a linear variation with the hardness andsoftness (En) of the metal ion. The ternary complexes of 2–CPHAAA complexes of the Th (IV) and UO(VI) with 2AMP or 1,10-phen ligands were studied in 75% (v/v) dioxane water solvents. Key words:Binary complexes, mixed ligands, stability of complexes and thermodynamic parameters. IntroductionIn the preceding papers [1-3] we have reported on the complex equilibria of 2-car boxyphenylhydrazoacetoacetanilide (2-CPHAAA) (structure I) and 2-carboxy phenylhydrazo para methoxyacetoacetanilide (2-CPH-P-OCH-AAA) with proton , some of transition and lanthanide ions in 75% (v/v) dioxane-water and 0.1 M KNO.The study revealed that the ligands behave as dianionic tridentate (NOO)-donor. The coordination sites as obtained from infrared were carboxylate oxygen, ketonic oxygen and hydrazo nitrogen. In the present report, the chelating ability of 2-CPHAAA has been measured through the isolation of solid complexes and investigation through elemental analysis, IR , UV-visible, 1HNMR spectra and TG, - DSC measurements. The thermodynamic parameters were determined and discussed through the separation into their electrostatic (el) and non-electrostatic or cratic components. The mixed –ligand complexes of copper (II),Ni(II),Co(II),Fe(III),UO(IV) and Th(VI) were prepared by mixing equimolar amount 2CPHAAA with 2- amino-4-methylpyridine (2-AMP) or 1,10 phenanthroline(1,10 – phen) In addition the mixed complexes were investigated in 75% (v/v) dioxane water solvents. N N = C NH N CH NH2 N N AMP C O CH C O O H C O - carboxyphenylhydrazo aceto Acetanilide( - CPHAAA) ( ) 2 1 2 2 - phen 1 , 10Material and MethodsThe organic ligand 2-CPHAAA was prepared as described previously [1-2]. For starting materials, purification of solvents and procedure see reference. Conductance and magnetic moment as well as recording parameters for infrared, UV-visible and 1HNMR spectra and TG-DSC measurements are described in. Preparation of Metal Complexes: The binary and ternary complexes were prepared in the presence of LiOH. HO as deprotonating agent. Preparation of binary complexes: A mixture as 1:1: 1 Mn+: L: LiOH.HO in 75% (v/v) methanol – water was refluxed Research Journal of Chemical Sciences __________________________________________________________ ISSN 2231-606X Vol. 1(7), 1-14, Oct. (2011) Res.J.Chem.SciInternational Science Congress Association 2 K n for 3hr with constant stirring to ensure the complete formation of the metal complexes. The precipitated solid complexes were filtered, washed several times with 1:1 aqueous methanol to remove any traces of unreacted materials. Finally the complexes washed with diethylether and dried in a vacuum desicator over anhydrous calcium chloride. The complexes obtained by this method are: [Cu(HL)(OH)]. (3); [Co(HL)(OH)]1/2 HO (6); [Ni(HL)(OH]. (7), [Cd(HL)].3 HO (2); [Th(HL)(OH].5HO(8) and [UO`(HL)]. 4HO (9). Preparation of ternary complexes: Molar ratio of Cu(II); 2CPHAAA : 2AMP or 1,10-phen : LiOH = 1:1:1 was refluxed in 50% methanol water for 5h with constant stirring to ensure the complete formation of the metal complexes. The precipitated solid complexes were filtered, washed several times with 50% (v/v) methanol -water to remove any traces of unreacted starting materials. Finally, the mixed ligand complexes were washed with diethyl ether and dried under vacuum over anhydrous CaCl. The complexes obtained are: [Cu (HL) (1,10-phen) (OH)].2HO(4) and [(Cu) (HL) (2AMP) (OH)]. HO (5). The full analyses of these complexes are presented in table (1). Results and DiscussionThe potentiometric titration curves of 2-CHAAA ligand in absence and presence of different metal cations using 75% (v/v) dioxine-water as solvent and 0.10 M KNO is shown in figure 1. The curves shows long buffer region between a= 0 and a=1 (a = number of moles of base added per mol.of ligand followed by strong inflection at a= 1 due to the complete neutralization of carboxylic group of the ligand The second buffer region occurs at higher pH without any inflection point which indicates that dissociation of hydrazo proton is not clear. The diprotic nature of this ligand is substantiated from the titration curves of the ligand in presence of various metal ions, where two protons librated. For the general protonation equilibrium + Hn-1 L HL (n= 1 or 2) The constant, were determined from hydrogen concentration of ligand solution for each increment of base added. The values of these constants were calculated using the general relationship:  pHOHOHLogLogK]))][)(]))][)(1( Research Journal of Chemical Sciences __________________________________________________________ ISSN 2231-606X Vol. 1(7), 1-14, Oct. (2011) Res.J.Chem.SciInternational Science Congress Association 3 Table-1 Analytical and physical data of organic ligand: HL and its metal complexes Compound F.W color M.P C) Yield Elemental analysis , found (calc.) % C H N Metal (1)1715325.32 Yellow 220 80 62.30 (62.76) 4.90 (4.65) 12.90 (12.92) - - (2) [Cd(HL)].3HO C343411Cd 815.08 Yellow �250 73 49.90 (50.10) 4.60 (4.20) 10.10 (10.31) 13.83 (13.79) (3)[Cu(HL)(OH) 1715Cu 404.87 Green �250 59 50.60 (50.43) 3.70 (3.73) 10.10 (10.38) 15.87 (15.69) (4)[Cu(HL)(1,10-phen)(OH)].2HO 2927Cu 621.11 Pale green �250 67 55.80 (56.08) 4.50 (4.38) 11.50 (11.28) 10.16 (10.23) (5)[Cu(HL)(OH)(2-AMP)(OH].H 2225Cu 535.01 Green �250 63 49.40 (49.39) 4.80 (4.71) 12.90 (13.09) 11.92 (11.88) (6)[Co(HL)(OH)].1/2 HO 17161/2Co 409.26 Brown �250 74 49.80 (49.89) 3.90 (3.94) 9.90 (10.27) 14.21 (14.40) (7)[Ni(HL)(OH] 1719Ni 436.04 Pale green �250 84 46.80 (46.83) 4.60 (4.39) 9.70 (9.64) 13.21 (13.46) (8)[Th(HL)(OH].5HO 344215Th 1006.77 Yellow �250 69 40.80 (40.56) 4.50 (4.20) 8.50 (8.35) 23.12 (23.05) (9)[UO(HL)2].4HO 243614U 990.72 Yellow �250 64 41.20 (41.22) 3.80 (3.66) 8.30 (8.48) - - Table-2 Protonation constant and thermodynamic parameters of: 2CPHAAA ligand In 75% (v/v) dioxane – water at different temperatures and ionic strength = 0.1 M KNOLigand Symbol of Proton constant Temperature G H S Cal/mol.k 10 0 C 20 0 C 30 0 C 40 0 C Kcal/mol pK 6.77 6.43 6.30 5.88 8.74 9.24 1.70 2-CPHAAA pK 12.42 12.22 11.94 11.14 16.63 16.49 -0.50 Table-3 Stability constants of 2 CPHAAA ligand – metal chelates at different temperatures, [ = 0.1 M KNO; 75 (v/v) dioxane– water] Cation Log K 1 Log K 2 10 o C 20 o C 30 o C 40 o C 10 o C 20 o C 30 o C 40 o C Cu 2+ 14.72 14.53 14.44 13.79 9.18 9.08 8.92 8.2 Ni 2+ 10.84 10.53 10.28 9.46 8.60 8.14 8.22 7.79 Co 2+ 10.71 10.37 10.19 9.31 7.99 7.82 7.63 7.29 Zn 2+ 10.84 10.51 10.30 9.37 8.46 8.11 8.05 7.13 Mn 2+ 10.36 10.11 9.90 9.01 6.84 6.43 6.34 5.62 Cd 2+ 10.69 10.34 10.17 9.30 6.71 6.50 6.32 5.71 UO 2 2+ 14.79 14.72 14.40 13. 97 8.22 7.95 7.75 6.99 Th 4+ 15.10 14.73 14.63 14.14 11.16 10.94 10.76 10.36 Sm 3+ 12.87 12.58 12.33 11.73 9.33 9.29 9.21 9.11 Er 3+ 12.49 12.19 11.94 11.32 9.43 9.32 9.05 8.42 Research Journal of Chemical Sciences __________________________________________________________ ISSN 2231-606X Vol. 1(7), 1-14, Oct. (2011) Res.J.Chem.SciInternational Science Congress Association 4 Where m is the ligand basicity. The correction of pH values in 75% (v/v) dioxin- water was taken as 0.28. Since the ionic product of the water , pK in 75% (v/v) dioxine- water medium is approximately 18.7, both of the hydrogen and hydroxyl concentration term in equation 1 are negligible in the region of proton dissociations . The values of pK and pK for 2-CPHAAA ligand at different temperatures are presented in table 2. The variation of pKandpK with 1/T was checked using linear regression method and always gave straight lines of correlation coefficient (r) equals to 0-990-0.0999. This indicates that raising of the temperature increase the acidity of the ligand. The linear change ofpK or pKwith 1/T permits the calculation of the enthalpies of protonation by use of Vant Hoff equation: 2 303 . 2 RT dTdLogKThe values of H are calculated in each case by least –squares fit of the data to the relation: consRTLogKtan303.2 D - )2( The free energy G and entropy S are calculated from known relationships:G=2.303 RT Log K (3) and )( T G H S D - D (4) The summary of protonation constants at different temperatures as well as the thermodynamic parameters for the ligand is coupled in table 2. The effect of –HN-N- -diketone grouping on the dissociation of the carboxylate proton is apparent when this groups is absent e.g benzoic acid in which its pK equall 6.50. The thermodynamic parameters of the dissociation process of the ligand are given in table 2. Inspection of these values reveals that the values H ( and ) are positive, indicating that the dissociation is accompanied by absorption of heat and the processes is endothermic. Such positive value due to the breakage of the covalent bond present on the ligand. The thermodynamic parameters described the dissociation of the protons from carboxalate ( , , ) and hydrazo groups ( , , ) show the order This order indicates that after the elimination of the carboxylate proton, the charge density on the species increases and this retards the dissociation of hydrazo proton. This is supported by the order obtained for the enthalpies and entropies 2,2 The negative values of S make the dissociation process non.- spontaneous and G positive. This negative value of entropy arise from the fact that the degree of the orientation and partial immobilization of dioxane and water molecules by H, the neutral and anionic species is larger in dioxane -water mixture than in pure water. Interaction Of 2-Cphaaa And Metal Ions: The titration curves of 3:1 2CPHAAA: metal ions indicate the diprotic nature of the ligand. Always two protons liberate by the metal cation. The curve show inflection point at m = 4 (m=number of moles of base added per mol of metal) due to the formation of bis chelates n+ + 2H ML+ 4HThe values of the stability constants at different temperateness were calculated as described in [3] and included in table 3. The conventional thermodynamic functions accompanying complex formation were calculated and have been divided into electrostatic (el) and non-electrostatic (non) parts using the methods suggested by Gurney, Anderegg, Degisher and Nancalles10 and modified by Murakami and Yoshing11ln q RCnRT (5) DH1(RC (6) lnnRT (7) Where is a temperature characteristic of the solvent12. According to the definition, the separated thermodynamic parts are summarized in table 4. Table 4 Non electrostatic (non) and electrostatic (el) thermodynamic function accompanying the complex formation: M + nL MLn Table-4non el G nRTlnM+RCa q /T RCe H RCa q q / 1( T RC S -nRlnM q q / )/( T RC The values of the free parameters C and a to calculate each component in table 4 can be determined from equation 5 and 6 or 7 when the values of S, G and H are known, the calculated values are given in table 5 Mixed Ligand Chelates of Uranyl and Thorium Metal Ions: The nature of mixed complexes of UO(VI) and Th( IV) cations using 2AMP as primary ligand and 2CPHAAA as secondary one are carried out by PH –metery. The protonation constants pK and pK of the dihydro 2AMP were determined by titration of 30 ml of 0.003 M 2AMP in 75% (v/v) dioxane-water and 0.1 M KNO against 0.06M HNO. The values of constants obtained at 30 C are 2.27 and 5.84 for pK and pK respectively. Research Journal of Chemical Sciences __________________________________________________________ ISSN 2231-606X Vol. 1(7), 1-14, Oct. (2011) Res.J.Chem.SciInternational Science Congress Association 5 Figure-2 Potentiometric titration of 2-CPHAAA and 2-amino-4-methyl pyridine at ionic strength mm = 0.10M-KNO, T = 30°C and 75% (v/v) dioacase-water in presence of UO (II) ions 1-1:3 motar ratio of UO(II) (0.001M) to 2-CPHAAA(0.003M) 2-1:3 molar ratio of UO (II) (0.001M) to 2-amino-4-methylpryidine (0.003M). 3-1:1:1 motar ratio of UO(II) (0.003M) to 2-CPHAAA (0.003M) and 2-amino-4-methyl pyridine (0.003M) Figure-3 Potentiometric titration of 2-CPHAAA and 2-amino-4-methyl pyridine at ionic strength mm = 0.10M KNO, T = 30°C and 75% (v/v) dioxane-water in presence of Th(IV) ions 1-1:3 motar ratio of Th(IV) (0.001M) to 2-CPHAAA(0.003M) 2-1:3 molar ratio of Th(IV) (0.001M) to 2-amino-4-methylpryidine (0.003M). 3-1:1:1 motar ratio of Th(IV) (0.003M) to 2-CPHAAA (0.003M) and 2-amino-4-methyl pyridine (0.003M) Titration procedures involved potentiometric titration of the following carbonate free solutions: 1:1:1 M: L : A ( L = 2CPAAA; A = 2 AMP and M = Th4+ or UO2+ ) = [HA] = 0.003 M + [HL] = 0.003 M + [Th4+] or [UO2+] = 0.003M + [HNO] = 0.006 M The titration curves are plotted in figure 2 and 3. The absence of any kind of precipitation during the course of the titration indicates that complex more resistant to hydrolysis is produced when the two ligands are mixed. The lowering of the original pH for 1 : 1 : 1 titration curve compared to MA and ML curves followed by inflection point at m=4 supported the formation of mixed complexes. Anotherevidence comes from each system UOLA or ThLA curves does not coincide with either ML or MA curve. The mixed complex formation should be, therefore takes place by simultaneous and not by stepwise equilibrium and both the ligands attached simultaneously to UO(VI) or Th(IV). The long buffer region between m=o and m=4 followed by inflection point at m=4 in MLA curve indicate the following equilibrium: A + HL + UO2+ MLA2- + 4HA + HL + Th4+ MLA + 4H and for UO2+ ][][[2][+-=UOMLAMLA (8) and for Th4+ ][][[][+=ThMLAMLA (9) L represents the primary ligand 2AMP and HA the secondary ligand 2CPHAAA. The stability constant is calculated according to the method described by Candike and Martell13. The calculated values are presented in table (6). )]])MMAMLMLALogKLogKLogKLogKvaluesThey are positive and equals 2.40 and 6.76 for UO2+ and Th4+ complexes respectively. The values of Log K depend on the geometry of the complex and the denticity of the ligands. In the present study the Log K values are relatively higher which indicates a greater stabilization of the mixed ligand complexes. The higher denticity on the ligand could account for such stabilization. The ligand 2CPHAAA Research Journal of Chemical Sciences __________________________________________________________ ISSN 2231-606X Vol. 1(7), 1-14, Oct. (2011) Res.J.Chem.SciInternational Science Congress Association 6 contains several coordination sites (behave as tridentate NOO-donar through oxygen of carboxylate and ketonic groups and azomethine nitrogen). This beside 2AMP ligand which acts as bidentate NN-donor The parameter "percentage relative stabilization (% R.S.)" has been introduced and defined as 100MLLogKMLLogKMAMLALogKThis value is 43.10 and 73.90 for UO2+ and Th4+ complexes respectively. These higher values indicate greater stabilization of the ternary complexes which could be tentatively be explained on the basis of cooperative effect14 between the primary and secondary ligands. The possibilities of the steroselectivity, indirect cooperative effect and intra – molecular covalent bond formation being ruled out and hydrophobic interaction takes place and consequently greater stabilization of the mixed complexes results. Complexes in solution state: Table 5 report the data on thermodynamic parameters , and n (n=1,2). The data of all complex systems show negative values of enthalpy, while entropy values are positive or negative. These indicate that in systems of negative enthalpy and positive entropy values are enthalpy or entropy controlled, while for complex of negative enthalpy and entropy, the enthalpy contribution has the major deriving force.The values of the stability constants of the complexes under investigation decrease with a rise of temperature, indicating that the formation eqiulibria are exothermic in nature. This is also borne out by the fact that G and H are both negative. The G values in any solution eamined varied as usual, in the sequence - G1 � -G2. The values of generally varied in the sequence - �- while the entropy order is as follows � . Therefore, the decrease in with n increase is responsible for the decrease in with the increase in n. Table-5 Thermodynamic parameters, non-electrostatic (non) and electrostatic (el), Thermodynamic quantities and T*associated with the reaction of metal ions with 2-CPHAAA. In 75% dioxane – water [ = 0.1 M KNO, V=30 ml, [L] =0.003 M, [M] = 0.001 M] Cation 1 cal / mol.K c a 1non -elnonelCal/mol.k K cal / mol K cal / mol K cal / mol Cu 2+ 20.04 10.56 101 -2798.1 -0.103 2.992 23.229 0.574 9.985 108.98 Ni 2+ 14.27 15.68 98.9 -2743.10 -1.080 8.309 22.772 5.891 9.789 106.83 Co 2+ 14.15 11.75 85.5 -2399.80 -0.668 5.603 19.923 3.185 8.564 93.465 Zn 2+ 14.30 17.06 103.50 -2862.50 -1.203 9.262 23.764 6.844 10.215 111.49 Mn 2+ 13.74 10.53 80.10 -2261.70 -0.547 4.876 18.776 2.458 8.071 88.085 Cd 2+ 14.11 15.60 98.10 -2722.70 -1.087 8.301 22.603 5.883 9.716 106.04 UO 2+ 19.98 9.94 98.8 -2740.50 -0.029 2.578 22.751 0.160 9.779 106.73 Th 4+ 20.30 10.90 103 -2849 -0.129 3.150 23.651 0.733 10.167 110.96 Sm 3+ 17.11 12.97 99.30 -2754.10 -0.574 5.559 22.863 3.141 9.828 107.26 Er 3+ 16.37 13.32 98.70 -2721 -0.667 6.027 22.589 3.609 9.710 105.97 G 2 H 2 cal/mol.K c a 2 non - 2 el Kcal/mol Kcal/mol Kcal/mol Cal/mol.k Cu 2+ 12.37 13.17 84.30 -2369.30 -1.001 7.132 19.669 4.714 8.455 92.277 Ni 2+ 11.45 9.32 68.60 -1965.10 -0.590 4.725 16.314 2.307 7.012 76.533 Co 2+ 10.59 8.04 61.70 -1783.70 -0.472 4.092 14.808 1.674 6.365 69.47 Zn 2+ 11.17 15.17 86.90 -2437.10 -1.336 8.890 20.232 6.472 8.697 94.617 Mn 2+ 8.80 13.89 74.90 -2127.80 -1.489 8.714 17.664 6.296 7.593 82.87 Cd 2+ 8.77 11.43 66.60 -1916.80 -1.205 7.007 15.913 4.589 6.8403 74.652 UO +2 14.14 10.75 82.20 -2314.20 -0.541 4.909 19.212 2.491 8.258 90.131 Th 4+ 14.93 9.10 79.30 -2241.40 -0.247 3.519 18.607 1.101 7.998 87.293 Sm 3+ 12.79 2.02 48.90 -1460 -1.099 -0.772 12.120 -3.190 5.210 56.862 Er 3+ 12.56 11.57 79.60 -2249.80 -0.792 5.959 18.677 3.541 8.028 87.623 Research Journal of Chemical Sciences __________________________________________________________ ISSN 2231-606X Vol. 1(7), 1-14, Oct. (2011) Res.J.Chem.SciInternational Science Congress Association 7 Table-6 Stability constants of single and mixed chelates and other related parametersMetal ion Primary Ligand (H 2 A) LogKMASecondary Ligand(H 2 L) LogkMLLogKMLA logk %.R.S UO2+ 2AMP 3.34 2-CPHAAA 14.72 21.06 2.40 43.10 Th4+ 2AMP 4.02 2-CPHAAA 14.73 25.61 6.76 73.90 The decreased values of and with increase of n might be expected if stronger metal-ligand bonds within an aquametal ion-weaken when a part of the water molecules within the aquametal ion is replaced with a ligand which has an atom or atoms, with stronger donor property than water15. Thus we can accept that the Ln-OH bonds within the mono complex are weaker than those within the aquametal ion. Therefore when the second ligand molecule bonded to the mono complex, the energy(enthalpy)to expel water molecules (the ligand is tridentate OON-donor) from the coordination sphere of the mono complex may be less than that of aquametal ion consequently the stepwise enthalpy of formation of these complexes became less negative than the mono complex. In contrast, when water molecules within the mono complex in which water molecules combine relatively weakly with the metal ions are removed from the coordination sphere, a lower entropy gain may result compared with that for releasing water molecules from aquametal ion. The tridentate (OON-donor abilities of 2-CPHAAA is confirmed from its higher negative enthalpy values of different complexes table 5. Digisher and Nancollas10 have permitted out that for systems involving nitrogen and carboxylate oxygen, the H values reflected the change in the number and strength of the bonds made and broken during the reactions and have correlated the values of H to the type of bonding between metal ion and the ligand molecule, and to structural feature of the complex-considering this and the fact that the crystal field produced by an oxygen containing ligand, i. e COOH or C=O are similar to those of water molecule16, H will not be significantly affected by the displacement of water molecules. Thus, the higher negative values of the enthalpies of the complex system obtained her could be related to the coordination sites of nitrogen atom of hydrazo group. The entropy changes associated with metal – chelate formation on the studied systems are relatively high and positive for 1:1complexes table 5. In the case of bis – chelate positive values are obtained which could be attributed to a combination of (a) an increase in S values owing to release of water of hydration (b) a decrease in entropy of transilation on the formation of one chelate from two species (c) a decrease in configuration entropy of the ligand on the complex formation. For reactions with charged donor group (the ligand behaves as dianion species i.e L2-) the entropy changes associated with (a) predominate because neutralization of charge on the metal ion cause great disorder. In order to provide information on the nature of bonding in the complexes, the values of , n and have been separated into their electrostatic (el) and non electrostatic (non) or crtatic components. The separated el, non, el,non and el (non is constant and equals to 8 cal/mol.k) are calculated and given in table 5 for all complexes: For the equilibrium involving mono complex formation which has been represented by the equation +n + HL ML+n-2 + 2Hnon values are more negative than el value indicating that the electrostatic forces are weaker than non-electrostatic forces: The order is- non � -el and remains almost constant in all complexes table 5, indicating thereby that metal chelation reactions occurs by similar mechanism. The enthalpy that also support the above consideration i.e -non� -el. The non value reflects the covalency of bonding and structural change on complexes10. Regarding the covalency, the softer metal ion has a greater affinity for softer donor17. The quaintly E was introduced by Klopman18 as a measure of hardness and softness of metal ion in aqueous solution, A soft metal is characterized by a large negative value of E and vice versa. In general the Evalue above 2.0 ev (hard), 2 to – 2 ev intermediate and below – 2ev (soft) respectively. According to this soft metal such as Cd2+ (E = -2.04ev), Cu2+ (E= -0.55ev) border line, metals such as Ni2+, (E = 0.29ev) , Fe2+( E = 0.69ev), hard metals such as La3+ (E= 4.5 ev) , Co2+ (E = 2.03ev). Values of non( non + 2non) are plotted against the quantility EFigure 4. A linear correlation appears to exist, -nonincreases with the softness or hardness of metal ion. A deviation of Co2+ from the line, in addition to Ln3+ (E= 4.5 ev) does not fit the line in the figure. This could be related to the different nature of lanthanum complexes (mainly ionic) than d- block elements. Research Journal of Chemical Sciences __________________________________________________________ ISSN 2231-606X Vol. 1(7), 1-14, Oct. (2011) Res.J.Chem.SciInternational Science Congress Association 8 Table-7 Characteristic IR bands (cm-1 of organic ligands and HL and its metal complexesCompound (OH) (NH) Hydrazone (CH) aromatic (CH) aliphatic (C=O) (C=N) asCOOCOO(M-O) (M-N) Additional bands (1) HL (ligand) 3308 br 3255 br 3055 s 2967 m 1695 s 1664 s 1598 s - - - - 3182 br (NH) of acetanilide moiety. (2) - 3234 br 3075 m 2959 m 1661 s 1597 s 1484 s 1319 s691 m 624 m 532 m 3380 br (lattice water), 3185 br (NH) of acetanilide moiety. (3) - - 3083 m 2963 m 1675 s 1591 s 1448 s 1314 s 690 m 665 m 636 m 530 m 3523 br (coordinated water), 3186 br (NH) of acetanilide moiety. (4) - - 3070 m 2966 m 1669 s 1593 s 1447 s 1311 s 690 m 663 m 636 m 561 m 530 m 3522 br (coordinated water), 3411 br ( lattice water), 1574 s (coordinated C=N of 1,10-phen) 3184 br (NH) of acetanilide moiety. (5) - - 3063 m 2962 m 1676 s 1591 s 1448 s 1314 s 690 m 666 m 637 m 560 m 530 m 3528 br (coordinated water), 3411 br ( lattice water), 3176 br (coordinated NHgroup and (NH) of acetanilide moiety), 961 s (pyridine ring breathing mode). (6) - - 3075 s 2967 m 1659 s 1590 s 1448 m 1310 s 690 m 660 m 624 m 538 m 3508 br (coordinated water), 3394 br ( lattice water), 3183 br (NH) of acetanilide moiety. (7) - - 3059 s 2961 m 1654 s 1593 s 1448 s 1313 s 693 m 663 m 624 m 560 m 3486 br (coordinated water), 3185m br (NH) acetanilide moiety). (8) - - 3074 s 2964 m 1659 s 1584 s 1485 s 1356 s 693 m 665 m 621 m 533 m 3504 br (coordinated water), 3428 br ( lattice water), 3187 br (NH) of acetanilide moiety. (9) - 3222 br 3067 s 2962 m 1659 s 1584 s 1485 s 1313 s693 m 666 m 530 m 3391 br (coordinated water), 3180 br (NH) of acetanilide moiety,931 s (antisymmetric (O=U=O) The values of el presented in table 5 are nearly constant. This is ascribed to the nearly constant ionic radius of these metals. As result of this the value of H for a given complex system is mainly determined by the value of non Complexes in solid state: The ligand 2 CPHAAA (HL) has different tautomers as shown in scheme 1. The band at 3204 cm-1 due to hydrazo group19-21 indicates that tautomer (b) in scheme 1 is the predominant one. The broad band observed at 3308 cm-1 in the spectra of the free ligand table 7 is assigned to (OH) of the carboxylic group. The broadness of such band is due to hydrogen bond formation. The carbonyl group of carboxylic was observed at 1695 cm-1. In all complexes the band due to (OH) of the carboxylic group disappeared, indicating its deprotonation in the ligand during complexation. The participation of the carboxylate groups in complex formation is also confirmed by the disappearance of the band due to (C=O) of -COOH group and appearance of two new bands at1447-1487 and 1310- Research Journal of Chemical Sciences __________________________________________________________ ISSN 2231-606X Vol. 1(7), 1-14, Oct. (2011) Res.J.Chem.SciInternational Science Congress Association 9 1356cm-1. Table 7, assigned to as (COO-) and (COO-) respectively. This indicates that the carboxylate group behaves as a monoanionic mono dentate group22-24 N CH O H N CO CO NH N CCO O H CO CO NH HN N CCO O H N CO C NH OH N CCO O H N CC NH O OH CH CH CH CH (a) (b) (c) (d)Scheme-1 The stretching vibrations of carbonyl groups of the ligand is complicated due to the overlap between the carbonyl groups of both carboxylic and acetyl group which leads to a single band at 1695cm-1, the band due to carbonyl group of acetanilide moiety was observed at 1664cm-1.In all complexes a band was observed at 1664-1675 cm-1 assigned to the overlap of the coordinated group of the acetyl group and the uncoordinated carbonyl group of the acetanilide moiety. The azomethine group was observed at 1598 cm-1 in ligand spectra and was slightly affected in all complexes of 2CPHAAA ligand. Figure-4 The relation between hardness and softness E (ev) of metal ion with DD1ion+ DD2nonfor 2-CPHAAAThe ligand (HL) showed IR bands at 3255 and 3182 cm-1, due to (NH) of hydrazone moiety and (NH) of acetanilide moiety respectively. The band due to (NH) of acetanilide moiety, was slightly shifted in all complexes except cadmium and uranyl complexes appears at 3234 and 3222cm respectively. The IR spectra of the free ligand and its metal complexes indicated that the ligand behaves either as a monoanionic tridentate, through oxygen atoms of carboxylic or carbonyl groups and the nitrogen atom of NH group of hydrazo moiety or as a dianionic tridentate ligand, as the previous mode of coordination except the deprotonation of NH group of hydrazo moiety. The mixed -1,10-phen complexes (4) showed new band at 1574 cm-1 would be due to the coordinated C=N groups of 1-10-phen25-28. The mixed 2-amino-4-methylpyridine (2AMP) complexes (5) showed two new bands at 3176 and 961 cm-1. The second band is assigned to the skeletal vibration of pyridine ring [29], breathing mode, while the first band is due to the coordinated NH groups. The two new bands at 690cm-1 and 561cm-1 are assigned to (M-O) and (M-N) respectively. The (OH) of the lattice water were observed at 3411 cm-1, while the IR spectra of complexes display the absorption peaks of coordinated water at 3528 cm-1. The IR spectra of the uranyl complexes (19) show strong band at 931cm-1 assigned to anti symmetric as (O = U = O) vibration The assignment of the main signal in the H NMR spectra of the free ligand and their diamagnetic complexes of cadmium ion are listed in table 8. The free ligand showed a signal at 14.92 ppm due to the carboxylic group proton. This signal disappeared in the complex [Cd(HL)]3HO (2). This indicates the deprotonation of the carboxylic group – COOH during the formation of the metal complexes. The signal due to the NH group of hydrazone moiety was observed at 13.73 ppm this signal was shifted down field in the spectrum of complex indicating the participation of this group in coordination to central metal ion. The signal of the NH group of acetanilide moiety in the free ligand was observed at 11.08 ppm (H) and slightly affected in complex (2) indicating the non involvement of this group in coordination to the central metal ion. The free ligand also showed the signals due to the aromatic protons at 7.15-8.00 ppm which were slightly shifted upfield in the complexes. The signals due to aliphatic protons were observed at 1.92 ppm (3H) due to the CH group. These protons were slightly shifted to 2.01 ppm in the complex. The lattice water molecules were observed at 3.40 ppm (6H) for cadmium complexes. Research Journal of Chemical Sciences __________________________________________________________ ISSN 2231-606X Vol. 1(7), 1-14, Oct. (2011) Res.J.Chem.SciInternational Science Congress Association 10 Table-8 H NMR data for organic ligand HL and its Diamagnetic Cadmium complexesCompound (COOH)(NH) hydrazone (CH) aromatic (CH) aliphatic Additional signals L Free ligand 14.92 (H) 12.73 (H) 7.15 – 8.0 (9H) 1.92 (3 H) 11.08 (H) proton of NH group of acetanilide moiety (2) - 15.26 (2H) 7.13-8.11(18 H) 2.01 (6 H) 11.07 (2H) protons of NH group of acetanilide moiety 3.4 (6H)lattice water Table-9 Molar conductance, Magnetic Moment and Electronic Spectral Data, cm-1 for organic ligand HL and its metal complexes Compound Molar Conductance(Ohm-1 cm2 mol-1) eff (B.M.) *, n * Charge transfer transitions d d Transitions L Free ligand - - 333670 , 28612 , 25126 - 2 6.16 Diam 34483 , 28571 , 24630 - 3 4.85 1.97 34602 , 28531 , 23781 20325 , 17480 4 3.30 1.91 34188 , 28490 , 23952 19084 , 15106 5 7.95 1.78 34662 , 28612 , 23781 20555 , 14738 6 9.30 2.64 34423 , 28571 , 23502 20704 , 16892 7 9.60 2.89 33784 , 28612 , 23809 15314 8 19.30 Diam 34130 , 28531 , 24450 - 9 8.24 Diam 34130 , 28531 , 24125 - a DMF solutions , 10 -3 , at 28 C b Measurements were taken at 27 From the results of both HNMR and IR spectra, it is suggested that the modes of coordination of the free ligand are as follows: The ligand behave as mono basic tridentate one , through the oxygen atom of the carboxylic group, the nitrogen atom of NH group of the hydrone moiety and oxygen atom of the carbonyl groups of the acetyl moiety or dianionic ligand, as previous mode of coordination except the deprotanation of NH groups of the hydrazone moiety. The conductance measurements (10-3M in DMF) indicate the complexes are non electrolyte. The UV-Visible spectra of the ligand and its complexes were carried out in 10-3 solutions. The values of band position (cm-1) and the magnetic moment values are listed in table 9. The UV-Visible spectra of the ligand showed bands at 33670, 28612 and 25126 cm-1 assigned to – , n – and charge transfer (CT) transitions within the molecules, respectively. The band of the free ligand were slightly blue shifted in all complexes, while new bands were observed in the visible region for Cu(), Co() and Ni() complexes due to d-d transitions. The magnetic moment eff value, of the binary Cu() complexes (3) was 1.97 B.M. This value reveals the presence of one unpaired electron and shows no copper – copper interaction. The a absorption band observed in its visible region at 20325 and 17480cm-1 are due to d –d transition in square planar Cu() complexes and are assigned to combination of B1g–E and B1g transitions30. The proposed structure for this complex in the square planar geometry is shown in figure 5. The mixed ligand complexes of Cu (II) with 1,10– phen. (4) and 2AMP (5) showed magnetic moment values, eff in the range, 1.78-1.91 B.M These values correspond to one unpaired electron and this offer an evidence for mononuclear structure of the complexes. The mixed ligand complexes of Cu () exhibited two transitions bands in the region 19084 – 20555 and 14738–15196 cm-1.The transitions including the mixed ligand complexes are similar in energies to those of binary complexes, and this indicated that the geometry of copper ion in the mixed complexes is distorted octahedral. The proposed structures of the mixed 1, 10 phen and 2AMP complexes are shown in figure.5. Research Journal of Chemical Sciences __________________________________________________________ ISSN 2231-606X Vol. 1(7), 1-14, Oct. (2011) Res.J.Chem.SciInternational Science Congress Association 11 N N CC N HC CH OOHC OO N C OC N N HC OOH N CC OOH O NN CH N CC N C CH OOOH N N N N CC N C CH OOOHN N NH2 N CC N C CH OOOHN N CC N C CH OOOHN Cd H3C ( ) 2 H2O 3 Cu ( ) 3 ( ) H2O Cu OH 2 4 ( ) H2O Cu OH OH 5 ( ) OH Co 1 / 2 H2O 6 ( ) OH Ni OH OH 7 OH Research Journal of Chemical Sciences __________________________________________________________ ISSN 2231-606X Vol. 1(7), 1-14, Oct. (2011) Res.J.Chem.SciInternational Science Congress Association 12 N N C N HC CH OOHC OO N C OC N N HC O O OC OH N N C N C CH OOHC OO N C OC N N HC OC OH H3C ( ) H2O 4 U 6 H3C H2O Th OH H2O 5 Figure-5 Suggested Structures of binary and ternary complexes The binary Co() chelats have the room temperate magnetic moment value 1.78 B.M, as expected for a square – planar Co() complexes31,32. The visible spectra exhibit peaks at 20704 and 16892 cm-1, assigned to A1g – Eg and A1g2gtransitions respectively, and are compatible with a square – planar geometry figure 5. The magnetic moment of the binary Ni() complex was found to be 2.89 B.M. suggest its octahedral structure [33]. The transition bands in the region 23809 and 15314cm-1assignable to 2g – T1g (F) and 2g –1g(P)) transitions respectively. The first transition band of the complex was overlapped by CT transition across the ligand molecules figure 5. The binary complexes of Cd(), Th(IV) and UO(VI) are diamagnetic and the electronic spectra of the complexes are dominated only by the ligand bands. The elemental analysis and H N M R spectra showed that Cd(II) complex have octahedral configuration figure 5. The complexes of Th(IV) and UO (VI) have octa- coordination number and in a distorted dodecahedral geometry figure 5. The results of TG – DSC analysis of the binary and mixed complexes are shown in table 10. The results shown good agreement with theoretical formula as suggested from analyses data. The complexes became anhydrous at 76137c. The loss of crystal water molecules was accompanied by endothermic peak in DSC with H 33.67 – 571.23 J/g. The coordinated water molecules were eliminated from complexes at relatively higher temperatures than the lattice water or outersphere water molecules. There are different routes in the removal of coordinated water molecules from the complexes, as follows: 1-Elimination of coordinated water molecules only in a separate steps as complexes (5) , (6) , (7) , (8) and (9) – The elimination of coordinated water molecules in this step (112– Research Journal of Chemical Sciences __________________________________________________________ ISSN 2231-606X Vol. 1(7), 1-14, Oct. (2011) Res.J.Chem.SciInternational Science Congress Association 13 240C) was accompanied by endothermic peak 2-elimination of the coordinated water molecules was accompanied by the decomposition of the complex at 272 c (H 64.82 j/g) and lead to non – isoble complex. The complexes start to decompose at relatively higher temperatures � 260 oc, and the organic ligand lose the gases CO2 , CO , (CN) , HC CH, and CH – CH. Table-10 Thermal analyses data for organic ligand HL and its metal complexes Compound Temperature Range (C) % Loss in weight found (calc.) DSC peak (0C) H (J/g) Composition of the Residue Probable composition of the Expelled Groups Endo Exo (1) HL Free ligand 50-293 293-517 38.92(38.73) 75.49(75.31) 256 483 - - 93.17 107.33 1313One molecule of CO, two molecules of CO and one molecule of CN Half molecule of CH-CH and four molecules of HCCH (2) 40-119 119-353 6.54(6.63) 44.69(44.42) 99 - - 271 53.66 -13.36 [Cd(HL)] [Cd(C1110)] Three molecules of lattice water Two molecules of CO,four molecules of CO, two Molecules of CN, half molecule of CH CH 3 and one molecule of HC CH (3) 50-167 167-374 4.50(4.45) 52.37(52.12) 118 - - 331 11.00 -53.85 [Cu(HL)] [Cu(C)] One molecule of coordinated water One molecule of CO, two molecules of CO, one molecule of CN, half molecule of CH-CH and two molecule of HCCH (4) 40-119 119-310 310-352 5.83(5.80) 29.20(28.98) 48.27(48.14) 103 - 239 - 272 - 122.00 -64.82 26.19 [Cu(HL)(1,10-phen)(OH)] [Cu(C1313(1,10-phen)] [Cu(C(1,10-phen)] Two molecules of lattice water One molecule of coordinated water, one molecule of CO, two molecules of CO and one molecule of CN Half molecule of CH-CH and four molecules of CN (5) 40-109 109-240 240-474 3.74(3.67) 10.22(10.10) 63.93(63.76) 101 - 402 - 240 - 38.94 -79.24 16.84 [Cu(HL(2-Amp)(OH] [Cu(HL(2-Ampy)] [Cu(C)] One molecule of lattice water Two molecules of coordinated water One molecule of CO, two molecules of CO, one molecule of CN, half molecule of CH 3 -CH 3 , two molecules of HCCH (6) 35-87 87-185 185-414 2.26(2.20) 6.77(6.60) 53.94(53.75) 68 161 342 - - - 34.75 70.52 14.56 [Co(HL)(OH)] [Co(HL)] [Co(C)] Half molecules of lattice water One molecule of coordinated water One molecule of CO, two molecules of CO, one molecule of CN, half molecule of CH 3 - CH 3 , two molecules of HC CH (7) 50-160 160-235 235-401 8.40(8.26) 12.44(12.39) 56.79(37.55) 160 224 349 - - - 78.38 3.52 15.34 [Ni(HL)(OH)] [Ni(HL)] [Ni(C)] Two molecule of coordinated water One molecule of coordinated water One molecule of CO, two molecules of CO, one molecule of CN, half molecule of CH 3 -CH 3 , two molecules of HCCH (8) 35-127 127-262 262-405 8.76(8.94) 12.48(12.52) 37.79(37.55) 103 - - - 236 385 61.56 30.17 184.45 [Th(HL)(OH] [Th(HL)] [Th(C1313] Five molecules of lattice water Two molecule of coordinated water Two molecule of CO, four molecules of CO, and two molecule of CN (9) 40-123 123-343 343-568 7.14(7.27) 27.69(27.46) 56.98(56.73) 104 - 441 - 311 - 69.08 -68.92 3.90 [UO(HL)] [UO(C1414] [UO(C] Four molecules of lattice water Two molecules of CO, and four molecules of CO Two molecules of CN, one molecule of CH-CH and eight molecules of HCCH Research Journal of Chemical Sciences __________________________________________________________ ISSN 2231-606X Vol. 1(7), 1-14, Oct. (2011) Res.J.Chem.SciInternational Science Congress Association 14 Conclusions This study reports the effects of temperature, metal ions, ligands on the stability of the chelates as well as their thermodynamic parameters. Generally the values of the stability constants of the complexes under investigation decrease with a rise of temperature, indicating that the formation eqiulibria are exothermic in nature. This is also borne out by the fact that G and H are both negative. The values in any solution examined varied as usual, in the sequence - � -. The values of generally varied in the sequence - �- while the entropy order is as follows � . Therefore, the decrease in with n increase is responsible for the decrease in with the increase of n. Value of H non show linear variation with the hardness and the softness (E) of the metal ions. The tridentate OON-donor abilities of 2-CPHAAA is confirmed from its higher negative enthalpy values of different complexes. 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