Optical absorption spectra of rare earth elements with amino acid in different solvents

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1 Available online at Advances in Applied Science Research, 2013, 4(3):33-38 ISSN: CODEN (USA): AASRFC Optical absorption spectra of rare earth elements with amino acid in different solvents Anup Kumar Gupta and Shri Kishan Ujjwal Department of Physics, Jai Narain Vyas University, Jodhpur, Rajasthan, India ABSTRACT The optical absorption spectra of complex of Neodymium and Praseodymium with amino acid Histidine as primary ligand and propane 1,3- diol as secondary ligand have been recorded in visible region ( nm) in ratio (1:2:1) in water. Methanol, Ethanol and Acetic Acid. The energies and intensities of various transitions were calculated using Judd-Ofelt relation and are in good agreement with what we have obtained experimentally. Key worlds: Rare earth metals, Amino acid, Optical absorption Spectroscopy, Judd Ofelt parameters. INTRODUCTION The optical absorption spectra of various complexes with rare earth ions in the f f transition have been studied continuously in last many years [1-7]. Some more spectroscopic studies too have yielded information regarding the structure and composition of complexes [8-13]. In present paper we report the optical absorption spectra of neodymium(iii) and Praseodymium(III) with Histidine as primary ligand and Propane 1,3- diol as secondary ligand. Various intensity parameters, bonding parameters, Slater -Condon parameters, Racah parameters, Lande parameters and Oscillator strength have been calculated. MATERIALS AND METHODS The ternary complex of praseodymium and Neodymium were prepared by method [14]. The chemical used were of AR grade and the metals were 99.9 % pure (Indian Rare Earth Ltd.). The complexes were synthesized with Histidine and propane 1,3- diol in molar ratio 1:2:1. The complexes so prepared were crystallized under vacuum. The absorption spectra of complexes were recorded on model uv-2601 Spectrophotometer in visible region nm in different solvents and the energies which were recorded in terms of wavelength have been converted into wave number. RESULTS AND DISCUSSION Energy Parameters. The energy levels for various transition ware evaluated theoretically by using relation. E j ( F, ζ k 4f 0 0 ) = Eoj (Fk, ζ4f ) + k = 2,4,6 E F k j F k + E ξ j 4f ζ 4f (1) where E 0j is the zero order energy of j th level. The values of zero order energy ( E 0j ) and partial derivatives E j / F k and E j / ξ 4f for the observed levels of Pr 3+, Nd 3+ calculated by Wong [15]. 33

2 Intensity levels Parameters:- The experimental values of the Oscillator strength for the various transitions have been computed by using the relation. 1/2 ע x P exp = 4.6 x 10-9 x ε m (2) Where ε m and ע are the molecular extinction coefficient and band width for transition respectively. 1/2 The experimentally observed value of oscillator strength for Neodymium complex along with their calculated values have been recorded in table 1, where as for Praseodymium have been recorded in table 2. The value of F 2, F 4 & F 6 i.e Slater-Condon parameters were recorded using Judd-Ofelt relation [16] by partial multiple regression method and have been collected in table 3 for Neodymium and in table 4 for Praseodymium. The value of parameters E 1, E 2, E 3 were calculated using relation. E 1 = 1/9(70 F F F 6 ) E 2 = 1/9(F 2-3 F 4 +7 F 6 ) (3) E 3 = 1/3(5 F 2 +6 F 4-91 F 6 ) and Nephelauxetic ratio β for neodymium complex has been recorded in table 3 and for Praseodymium complex has been reported in table 4. All these parameters have been calculated in different solvents i. e water(18.01), Methanol(32.04),Ethanol(46.07) & Acetic Acid(60.05) and the values of reduced matrix elements were collected from carnall et al [17]. The value in parenthesis indicates the molecular weight of different solvent. Using Judd-Ofelt relation in terms of T λ (λ=2,4,6) Parameters we have (2) (4) (6) ( ) ( ) ( ) P U v T U v T U v T = + + (4) calc x 2 x 4 x 6 Bonding Parameters From table 3 & 4 we find that in case of Neodymium as well as for Praseodymium complex the value of b 1/2 is positive indicating that the complexes are ionic in nature. In fig. 1 and fig. 2 we have shown the optical density with wavelength in all solvents for Nd 3+ complex and Pr 3+ complex in all four solvent. b 1/2 1 β = 2 1/2 (5) We have also calculated the values of oscillator strength for Neodymium and Praseodymium complex which have been reported in table 5 & table 6 respectively. Computed values of T λ parameters for Nd 3+ complex has been recorded in table 7 & for Pr 3+ complex in table 8. The values of refractive index parameters have been reported in table 9 & 10 for Neodymium & Praseodymium respectively. Table 1 : Observed & calculation values of energy levels for Nd 3+ complex in different solvent. 2 P 1/ G 11/ G 9/ G 9/ G 7/ G 5/ F 9/ F 7/ F 5/ F 3/ rms deviation

3 Table 2 : Observed & calculation values of energy levels for Pr 3+ complex in different solvents. 3 P P P D rms deviation Table 3: Computed value of Slater- Condon parameters & Landes parameters β & b 1/2 for Nd 3+ complexes in different solvent. F 2 ( ) F 4 ( ) F 6( ) ζ 4f ( ) E 1 ( ) E 2 ( ) E 3 ( ) F 4/F F 6/F E E E E-02 E 1 /E E 2 /E E E E E-02 β b1/ E E E E-02 Zero order parameters :- F 2 = F 4 = F 6 = ξ 4f = Table 4: Computed value of Slater- Condon parameters & Lande s parameters β & b 1/2 for Pr 3+ complex in different solvents. F 2 ( ) F 4 ( ) F 6( ) ζ 4f ( ) E 1 ( ) E 2 ( ) E 3 ( ) F 4/F F 6/F E 1 /E E 2 /E E E E E-02 β b 1/ Free ion Pr 3+ F 2 = Table 5 : Observed & calculated value of Oscillator strength for Nd 3+ complexes in different solvent. 2 P 1/ G 11/ G 9/ G 9/ G 7/ G 5/ F 9/ F 7/ F 5/ F 3/

4 Table 6 : Observed & calculated value of Oscillator strength for Pr 3+ complex in different solvents. Obs 3 P P P D Table 7: Compute value of T λ parameters & T 4 / T 6 for Nd 3+ complex in different solvent. T 2 x T 4 x T 6 x T 4 / T rms deviation E E E E-07 Table 8: Compute value of T λ parameters & T 4 / T 6 for Pr 3+ complex in different solvents. T 2 x T 4 x T 6 x T 4 / T rms deviation E E E E-07 Table 9 : Refractive index value observed for Complex Nd 3+ in different solvents.. Complex Solvent Refractive index water Nd(H) 2P Methanol Ethanol Acetic Acid Table 10: Refractive index value observed for Complex Pr 3+ in different solvents. Complex Solvent Refractive index water Pr(H) 2P Methanol Ethanol Acetic Acid

5 In fig. We have show the variation of optical density with wavelength in all solvents for Nd 3+ and Pr 3+ complex in visible region ( nm) Nd(H) 2 P 4 G 5/2 Water Methanol Ethanol Acetic Acid 4 F 5/2 Optical density G 11/2 4 G 9/2 4 G 7/2 4 F 7/2 4 F 3/ P 1/2 2 G 9/2 4 F 9/ Wavelength (nm) Fig. 1 Variation of optical density with wavelength for Nd 3+ complex in different solvent Optical density P 2 Pr(H) 2 P 3 P 1 3 P Wavelength(nm) Water Methanol Ethanol Acetic Acid 1 D 2 Fig. 2. Variation of optical density with wavelength for Pr 3+ complex in different solvent CONCLUSION In table 1 we have shown the observed energy (in wave number) as well as calculated values of energy levels for Neodymium in different solvents, which matches with the observed value. In case of Praseodymium too in table 2 we have reported the energy level parameters in different solvents. In has been obtained that calculated value of energy level parameters almost matches with observed value. Low rms deviation between these values supports the validity of relation used in case of Neodymium & Praseodymium complex in all solvents. It also indicates that formation of complex is perfect. 37

6 From table 3 & 4 we have observed that parameters values are roughly same in different solvents. The decrease of in value F 2 from that of free ion supports the complexation. The decrease in value show that on complextion the contraction of 4f- orbital is reduced with increase of atomic number of metal ion. Ten peaks have been observed in case of Nd 3+ & four in case of Pr 3+ complex. The difference of energy values between observed & calculation in small that too supports the formation of complex as well. The variation of wavelength with optical density for Nd 3+ complex & Pr 3+ complex have been shown in fig. 1 & fig. 2 resp. in different solvents in visible region( nm). In table 5 & table 6 we have reported the calculated values of oscillator strength for Nd 3+ & Pr 3+ complex in different solvent, which is in good agreement with observed value. The values of all parameter for 4 G 5/2 levels are maximum because of hypersensitive transition in case of Nd 3+ complex and 3 P 2 levels are maximum in case of Pr 3+ complex due to pseudo- hypersensitive transition. In table 7 &8 we have reported the value of T λ parameters along with ratio of T 4 /T 6 for Nd 3+ complex & Pr 3+ complex in all solvents. The ratio T 4 /T 6 is almost constant in all solvents & low value of rms deviation as well. We have also observed that the ratio T 4 /T 6 is low in each metal & the complex under study have ratio of range in case of Pr 3+ complex & of range in case of Nd 3+ complex, which supports that they have oxygen/ nitrogen donor liquids. From table 9-10 we have reported the value of refractive index for Nd 3+ & Pr 3+ complex, which is in the increasing order as is the increasing order of molecular weight of the solvent. Acknowledgement One of the author Shri Kishan Ujjwal thanks UGC, New Delhi for awarding Rajiv Gandhi National Fellowship. REFERENCES [1] Karakker D G, J. Inorg. and Nucl. chem. (GB), 1971, 33, 3713 [2] Henrie D F, and Choppin G R, J. Chem. Phys(USA), 1968, 49, 477 [3] Sharma Y K, et al., Indian J. of Pure and A. Phys, 2008, 46, 239 [4] Gupta Anup Kumar and Ujjwal Shri Kishan, Res. J. of Physical Sci, 2013, 1(2), 9 [5] Chaudhari K G, Savale P A, Advances in Applied Science Research, 2012, 3 (2),1895. [6] Chaudhari K G, Savale P A, Scholars Research Library, Archives of Applied Science Research, 2012, 4 (3), [7] Lis Stefan, et al., J. Spectrochimica Acta Part A, 2005, 62,478 [8] Tandon S P, and Govil R C, J. Chem. Phys, 1972, 57, 4097 [9] Bhutra M P, and Tandon S P,and Gupta Anup K, Rev.Tec. Ing.,Univ. Zulia, 1984, 7, 19 [10] Chaudhari K G, Savale P A, Archives of Applied Science Research, 2011, 3(6), 327. [11] Chaudhari K G, et al, Der Chemica Sinica, 2012, 3(5):1169 [12] Judd B R, Physical Review, 1967, 162, 28 [13] Binnemans K,et al., J. of Alloys and compounds, 2000, 303, 387 [14] Srinivasa Rao L, et al., Physica B: condensed Matter, 2008, 403, 2542 [15] Kenyon A J, Prog. Quantum Electron, 2002, 26, 225 [16] Judd B R, Physical Review, 1962, 127, 750 [17] Carnall W T, J. Chem. Phys, 1965, 42,