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Stability Constants of Cu(Il) – Chelates with 3-(2-Hydroxy-3-Iodo-5-Methyl Phenyl) 1-Phenyl-5-(4-Methoxy Phenyl) Pyrazoline and 3-(2-Hydroxy-3-Iodo-5-Methylphenyl)-5(4-Methoxy-Phenyl) Isoxazoline at Various Ionic Strengths Potentiometrically
| Content Provider | Semantic Scholar |
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| Author | Meshram, Yogita K. Mandakmare, A. U. Narwade, Maruti Laxman |
| Copyright Year | 2017 |
| Abstract | The interaction of Co(ll), Ni(ll) and Cu{ll) metal ions with 3(2-hydroxy-5-methyl phenyl) 5phenyl pyrazoline (ligand 1) and 3(2-hydroxy-3-nitro-5-methyl)phenyl)-5-phenyl pyrazollne (ligand 2) and 3(2-hydroxy-3-bromo-5-methyl phenyl) 1,5 Diphenyl pyrazoline (ligand 3) have been investigated by pH metric technique at 0.1 M ionic strength and 27±0.1°C in 70% diozame water mixture. The data obtained were used to estimate the values of proton-llgand stability constant (pk) and metal ligand stability constants (log k). It is observed that Co(ll), Ni(ll), and Cu(ll) metal ions formed 1:1 and 1:2 complexes with all the three ligands. Pyrazolines are weak bases and are good complexing agent due to presence of donor nitrogen. They form coloured complexes with metal ion in solid state. Nanwade ef.a/.' studied formation and stability constant of thorium (iv) complexes with some substituted pyrazolines. Recently complexes of 3(2hydroxy phenyl) 5-(4-x phenyl) pyrazoline with Cu(ll) and Co(ll) has been synthesised and characterised by Nalarajan et.al. From IR spectral study it is observed that coordination taken plaee through phenolic oxygen and azomethine nitrogen of pyrazoline ring. In view of the analytical applications of pyrazoline, it was of interest to know the physico chemical properties such as stabilities of its complex with Co(ll), Ni(ll), and Cu(ll) metal ions. The detailed study of complexes under identical set of experimental condition is still lacking. It is, therefore, thought of interest to study the chelating properties of some substituted pyrazolines under suitable condition pH metrically Metal nitrates (B-D-H) were dissolved in perchloric acid and their concentration were estimated by standard method'. Pyrazoline and substituted pyrazolines are insoluble in water and hence 70% diozane water (v/v) was used as a solvent. 1,4-diozame was purified by standard method^ and its purity was checked by potassium iodide. The other solutions were prepared in double distilled water. pH measurements were carried out with ELICO-LI-10 pH meter (accuracy ± 0.05 unit) using glass and colonel electrodes at 27 ± O.rC. The B values (pH water reading in 70% dioxane-water mixture) were converted to (H*) values by applying the corrections proposed by van-Uiterty and Ha as 4. The overall 0.1 M ionic strength of solution was calculated by the expression p = 14 + Z cizi^. The contribution of the other ions in addition to Na+ and CIO_,̂ were also taken into consideration. Proton ligand stability constants : Substituted pyrazoline may be considered as monobasic acids having only one replaceable H+ ions from -OH group and that -OH group generally dissociates completely above pH §.00; and can therefore be represented as : HL i.e HL = H* + L". The titration data were used to construct the curves between volume NaOH vs pH. They are called Acid, Ligand and metal titration curves. It is observed from titration curves for all the systems that ligand curves start deviating from the Table 1 : Determination of proton ligand stability constants (pK) of some substituted pyrazolines at 0.1 M ionic strength System Constant Pk Half Pointwise InteCalculagral tion 1) 3{2-hydroxy-5-methyl phenyl) 1,5diphenyl pyrazolines 12.20 12.25 ± 0.05 (Ligand 1) 2) 3(2-hydroxy-3-nitro-5-methyl phenyl 1,5 diphenyl 11.80 11.83 ± 0.06 pyrazoline (Ligand 2) 3. 3(2-hydroxy-3-bromo-5-methyl phenyl) 1,5 diphenyl and 11.85 11.88 ± 0.07 pyrazoline (Ligand 3) 196 Orient. J. Chem., Vol. 15(1) (1999) free acid (HCIOJ curves at about pH 7.0 and deviated continuously upto pH 12.5. The deviation shows that d i ssoc ia t ion and -OH group in subs t i t u ted py razo l ines . The average number of p ro ton associated with the ligand (na) was determined from acid and l igand titration curves employing the equation of Irving and Rosotti^ The proton ligand formation curves were then obtained by plotting the values of fTA Vs pH. From these graphs the values of pK were determined (half integral method) by nothing the pH at which "nA = 0.5. The accurate values of pK were estimated by pointwise calculations method which are presented in Table 1. pk values of ligand No.1 is greater than ligand No.2 & ligand No.3. this may be due to the effect of stronger electron withdrawing group (-NOj-) and (-Br-)group, that reduces the pK values but increases the dissociatipn. In case of simple pyrazoline pK values is greater this is due to the effect of methyl e lectron re leasing group than decreased the dissociation and increases the dissociation constant pK values are found to increase in the following order of Iigands1> Ligand 2 > Ligand 3. IVletal l igand stabi l i ty constants Metal ligand stability constants of Co(ll) Ni(ll) Cu(ll) complexes with some substituted pyrazolines were determined by employing Bjerrum calvin pH titration technique as adopted by Irving and Rossotti. The formation of Chelates between Co(ll) Ni(ll) and Cu(ll) can be substituted pyrazoline was indicated by i) The significant departure starting from pH 3.00 forCo(l l ) , Ni(ll). ii) and deviation of Cu(ll) metal titration curve from ligand curves was observed from pH 3.50 ill) Tho change in colour from light yellow to light brown and then dark brown as pH was raised from 2.,5 to 9,0. Table 3 : Motal ligand stability constants at 0.1IV1 ionic strength Table 2 : De te rm l i g a n d s tab i l i (Log K) of Co(ll), Ni(ll), substituted pyrazolines i n a t l o n of meta l ty c o n s t a n t s Cu(ll) complexes with at O.ltyl ionic strength System i) Co{ll) Ligand No. 1 Ni (1!) Ligand No. 1 Cu(ll) Ligand No. 1 II) Co(ll) Ligand No. 2 NI (II) Ligand No. 2 Cu (II) Ligana No. 2 III) Co (II) Ligand No. 3 Ni (II) Ligand No, 3 Cu (II) Ligand No. 3 Constant LogKI i.e.PLI 10.59 9.79 10.35 10.29 9.94 10.34 8.84 769 8.99 LogK2 i.e PL2 6.25 5.40 6.04 4.60 5.05 4.60 5.90 5.65 4.90 System Co(ll) Ligand No. 1 Co (II) Ligand No. 2 Co(ll) Ligand No. 3 Ni (II) Ligand No. 1 Ni (II) Ligand No. 2 Ni (II) Ligand No. 3 Cu (II) Ligand No. 1 Cu (II) Ligand No. 2 Cu (II) Ligand No. 3 LogKI LogK2 4.34 5.69 2.94 4.39 4.89 2.04 4.31 5.74 4.09 Log K1 LogK2 1.69 2.23 1.49 1.81 1.96 1.36 1.71 2.24 1.83 Deviation between (acid + ligand + metal) titration curves from (acid + ligand) titration curves started from pH 3 which shows the commencement of complex formation. It could be seen from (Table 2) that log K values follows decreasing trend. This is due to the effect of electron releasing group (CH3) and electron withdrawing group -NO^ and Br. The values of log K (log K, log K )̂ and .og K/ log K̂ are presented in Table 3. It is observed that the smaller difference may be due to trans-structure. The results shows that the ratio log K/Log K̂ is positive in all cases. This implies that there is little or no steric hindrance to the addi t ion of secondary l igand molecules. Validity of log K=a pK -f b relat ion The linear relation of log K = apK + b has been found out by some workers^ to hold for transition metal complexes of a series of closely related ligands. Similar plots of log K, and log K^ against pK showed satisfactory linear relation giving slope values 1.105, 0.99 0,95 respectively when the change in partial molal free energies of thermal ligand and proton ligand complex exactly compensate each other. The log K Vs pK plot is linear with the slope of unity. ACKNOWLEDGEMENT The authors are thankful to Principal and Head of Department, G.S. College, Khamgaon for providing all the facilities. REFERENCES 1. Narwade M.L., Jamode V.S. and Gudadhe S.K., Acta. Ciencia Indica, XIC, 234 (1885) 2. Vogel A. I . , "A Text Book of Quantitative Inorganic Analysis", Longmans Green (London) 589(1975) 3. Vogel A.I., "A Text Book of Practical Organic 4n.i/ys/s", Longmans Green (London) 177(1956) 4. Van Vitert L.G. and Hass C.G., J. Am. Ctiem. Soc, 75,451 (1953) 5. Irving H.M. and Rossotti H.S., J. Ctiem. Soc, 3397(1953) 6. Narwade M.L., Chinchoikar M.M. and Sathe S.W., Indian J. Chem. Sac, 194, 197 (1985) Oriental Journal of Chemistry Vol, 15(3)531-534(1999) STABILITY CONSTANTS OF Cu(ll) CHELATES WITH 3-(2-HYDROXY-3-IODO-5METHYL PHENYL) 1-PHENYL-5-(4-METHOXY PHENYL) PYRAZOLINE AND 3-(2-HYDROXY-3-IODO-5-METHYLPHENYL)-5(4-METHOXY-PHENYL) ISOXAZOLINE AT VARIOUS IONIC STRENGTHS POTENTIOMETRICALLY Y. K. Meshram*, A. U. Mandakmare and M. L. Narwade" Department of Chemistry, G.S. College Khamgaon (M.S.) 444 312, B.MV. College, AMT (India) •'Department of Chemistry, Government Vidarbfia Matiavidyalaya, Amravati (M.S.) (India) (Received, September 12, 1999) |
| Starting Page | 531 |
| Ending Page | 534 |
| Page Count | 4 |
| File Format | PDF HTM / HTML |
| Volume Number | 13 |
| Alternate Webpage(s) | https://shodhganga.inflibnet.ac.in/bitstream/10603/67283/11/11_published%20research%20papers.pdf |
| Language | English |
| Access Restriction | Open |
| Content Type | Text |
| Resource Type | Article |
