Indian Journal of Chemistry

Sect. A: Inorganic, Bio-inorganic, Physical, Theoretical & Analytical

Total visitors: 2,866  since 21-02-08

VOLUME 47A

NUMBER 1

January 2008

CONTENTS

 

9

 

Synthesis, characterization and properties of mono-, di- and polynuclear nickel(II) pseudohalide complexes containing bidentate Schiff bases. X-ray structure of [Ni(Ni,Np)2(NCS)2][Ni,Np = N-((pyridin-2-yl)benzylidene)benzylamine]

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Jaya Banerjee, Rajarshi Ghosh,
Sk
Hafijur Rahaman, Pradip Kumar Dan &
Barindra Kumar Ghosh*

 

 

 

Three different types of nickel(II) pseudohalide complexes, [Ni(Ni,Np)2(X)2] [Ni,Np = N-((pyridin-2-yl)benzylidene) benzylamine; X = N3-, 1; X = NCS-, 2; X = NCO-, 3], [Ni(Ni,Np)2(X)]2(Y)2 [X = N3-, Y = ClO4-, 4; X = N3-, Y = PF6-, 5; X = NCO-, X = ClO4-, 6; X = NCO-, Y = PF6-, 7] and [Ni(Ni,Np)(N3)2]n (8) have been prepared and characterized.

 

 

 

18

 

Self-assembly of hydrogen-bonded networks of [Cu(HL)Cl](PF6) (HL = N,N-bis(2-pyridylmethyl)-1,3-diaminopropan-2-ol) into 1D chains: Formation of new submicrometer [Cu(HL)Cl](PF6) rods

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

  

 

Koushik Dhara, Partha Roy, Mario Manassero &

Pradyot Banerjee*

 

 

 

A new mononuclear copper(II) complex [Cu(HL)Cl](PF6) having an N4O-donor ligand (HL = N,N-bis(2-pyridylmethyl)-1,3-diaminopropan-2-ol) has been synthesized and structurally characterized.

 

 

 

25

 

New nine coordinated hydrated heavier lanthanide ethylenediaminetetraacetates containing hydrazinium cation: Crystal structure of N2H5[Dy(EDTA)(H2O)3](H2O)5

 

 

L Vikram & B N Sivasankar*

 

 

 

Some new nine coordinated hydrazinium lanthanide ethylene diaminetetraacetate hydrates N2H5[Ln(EDTA)(H2O)3](H2O)5, where Ln: Eu, Gd, Tb or Dy, have been prepared in aqueous media and characterized.

 

 

32

 

Synthesis, structure and properties of [Pr(DMSO)5(H2O)2](μ-CN)[Co(CN)5]H2O

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Wen-Tong Chen*, Xi-Rui Zeng, Ya-Ping Xu, Qiu-Yan Luo & Hua-Long Chen

 

 

 

A new cyano-bridged praseodymiumIII-cobaltIII complex, [Pr(DMSO)5(H2O)2](μ-CN)[Co(CN)5]H2O, has been synthesized via solution reaction and characterized by X-ray diffraction.

 

 

37

 

Synthesis and crystal structure of square-planar and mixed ligand octahedral nickel(II) O,O-dicyclopentyl dithiophosphate complexes

 

 

 

Murat Taş*, Mehtap Yağan, Hmeyra Bati, Bekir Bati & Orhan Bykgngr

 

 

 

Ammonium O,O-dicyclopentylphosphorodithioate (dcpdtp) and its two complexes with nickel(II) have been synthesized from phosphorus pentasulphide and cyclopentanol in the presence of ammonia gas. The complexes crystallize in the triclinic system (space groups P ī) and exhibit a slightly distorted square planar [NiS4] and trans-octahedral [NiS4N2] geometry, respectively.

 

 

43

 

Novel method for the synthesis of zirconium(IV) chelate complexes from oxo-zirconium(IV) aryloxides

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

S C Chaudhry*, C Verma, S S Bhatt &
N Sharma

 

 

 

Reaction of oxo-zirconium(IV) aryloxides with the composition ZrO(OAr)2 and ZrOCl(OAr) [where OAr = OC6H4NO2-4, OC6H4Cl-2, and - OC6H4(NO2)2- 2,4] with chelating ligands such as acetylacetone (acacH), 2-hydroxyacetophenone (hapH) and salicylaldehyde (salH) in Et2O yield eight coordinate chelate complexes with the composition Zr(acac)4, Zr(hap)4 and Zr(sal)4.

 

 

49

 

Kinetics and mechanism of amine-catalysed solvolysis of azlactone in water-dioxan mixtures

 

 

 

Amel M Ismail

 

 

 

The effect of replacing solvent water by dioxan up to 50% v/v on the rate of catalytic-amine solvolysis of azlactone has been measured spectrophotometrically in the temperature range
40-60C.

 

Notes

 

55

 

Synthesis and characterisation of Sb2Zn2Cl4(OPri)6, MSb2Cl2(OPri)6 (M = Be, Mg, Zn), and M2Ti4Cl4(OPri)16 (M = Mg, Zn)

 

 

 

 

 

 

 

 

 

 

 

 

Jayshree Shahani & Anirudh Singh*

 

 

 

Reactions of MCl2 (M = Be, Mg, Zn) with Sb(OPri)3 and Ti(OPri)4 in desired molar ratios in benzene afford structurally interesting derivatives of the types MSb2Cl2 (OPri)6, Sb2Zn2Cl4(OPri)6 and M2Ti4Cl4(OPri)16.

 

 

 

58

 

Heterobimetallic penta- and hexa-coordinated organotin (IV) complexes at different temperatures

 

 

 

 

Rajesh Malhotra*, Jyoti Mehta, Kiran Bala & Ashok K Sharma*

 

 

 

The reactions of triorganotin (IV) chloride with ferrocenyl aroylhydrazone derived from condensation of acetylferrocene and aromatic acidhydrazide yield heterobimetallic penta- and hexa-coordinated organotin(IV) complexes of the type R3Sn(L) and R3Sn(HL)Cl (where R=Me, Et or Ph HL=ferrocenyl aroylhydrazone).

 

62

 

Thermochemistry of the compounds M(C4H7O5)xnH2O(s) (x = 1 and 2, n = 1 and 0) of several kinds of biologically active metal ions (M = Na, K, Mg and Ca) with L-threonic acid

 

 

 

 

 

You-Ying Di*, Sheng-Li Gao &
San-Ping Chen

 

 

 

The constant-volume energies of combustion (DcU) of the solid hydrated L-threonate, M(C4H7O5)xnH2O(s) (M = K, Na, Mg and Ca; x = 1 and 2; n = 1 and 0),have been determined by an RBC-II precision rotating-bomb combustion calorimeter at 298.15 K. The standard molar enthalpies of combustion of these compounds (DcHm0) have also been calculated. The standard molar enthalpies of formation of these compounds (DfHm0) have been derived from the combination of the standard molar enthalpies of combustion of these compounds with other auxiliary thermodynamic quantities.

 

66

 

Excess molar volumes and viscosity deviations of binary liquid mixtures of N-methylacetamide with ethyl acetate, ethyl chloroacetate and ethyl cyanoacetate

 

 

 

 

Sathyanarayana Boodida, Ranjith Kumar Bachu, Savitha Jyostna Tangeda & Satyanarayana Nallani*

 

 

 

The values of density and viscosity for the binary liquid mixtures of N-methylacetamide with aliphatic esters (ethyl acetate, ethyl chloroacetate and ethyl cyanoacetate) have been measured over the entire range of composition at T = 303.15318.15 K. Using these data, excess molar volumes and deviations in viscosity have been calculated. The results have been correlated with the Redlich-Kister type polynomial equation to derive the binary coefficients and standard errors.

 

 

71

 

Determination of the polyacid dissociation constants of glycyrrhizic acid

 

 

 

 

 

Chun-Xiang Zeng & Qin Hu*

 

 

 

Determination of the three stepwise dissociation constants of glycyrrhizic acid in water by potentiometric titration method is described. The experimental data have been processed with a stepwise linear regression and simultaneous equations algorithm. The three dissociation constants of glycyrrhizic acid assayed by the proposed method are 3.98 (pKa1), 4.62 (pKa2) and 5.17 (pKa3), respectively.

 

 

75

 

Enantioseparation condition of D,L-tryptophan using ligand exchange chromatography

 

 

 

 

 

 

 

 

 

 

Hongyuan Yan & Kyung Ho Row*

 

 

 

Chiral recognition mechanism and enantioseparation conditions of tryptophan enantiomers using ligand exchange chromatography are reported. Under the optimum conditions, baseline separation of the two enantiomers has been obtained on a C18 column with a resolution of 3.42 in less than 30 min using methanol-water solution (20:80 v/v) as mobile phase containing 3.0 mmolL-1 L-phenylalanine and 0.5 mmolL-1 copper sulphate. Thermodynamic data obtained by Vant Hoff plots reveal that the enantioseparation is an enthalpy-controlled process. The mechanism of chiral discrimination is based on the stabilities of the copper(II) binary complexes and their ternary diasteremeric complexes with amino acids formed in solution and stationary phase.

 

Authors for correspondence are indicated by (*)


Indian Journal of Chemistry

Vol. 47A, January 2008, pp. 9-17

 

Synthesis, characterization and properties of mono-, di- and polynuclear nickel(II) pseudohalide complexes containing bidentate Schiff bases. X-ray structure of [Ni(Ni,Np)2(NCS)2] [Ni,Np = N-((pyridin-2-yl)benzylidene)benzylamine]

Jaya Banerjee, Rajarshi Ghosh*, Sk Hafijur Rahaman, Pradip Kumar Dan & Barindra Kumar Ghosh*

Received 21 August 2007; revised 29 November 2007

Three different types of nickel(II) pseudohalide compounds, [Ni(Ni,Np)2(X)2] [Ni,Np = N-((pyridin-2-yl)benzylidene) benzylamine; X = N3-, 1; X = NCS-, 2; X = NCO-, 3], [Ni(Ni,Np)2(X)]2(Y)2 [X = N3-, Y = ClO4-, 4; X = N3-, Y = PF6-, 5; X = NCO-, X = ClO4-, 6; X = NCO-, Y = PF6-, 7] and [Ni(Ni,Np)(N3)2]n (8) have been prepared and characterized using microanalytical, spectroscopic and other physicochemical results. Single crystal X-ray study of one of the mononuclear compounds, [Ni(Ni,Np)2(NCS)2] (2) has been done. Structural analysis reveals that the metal center in 2 adopts a distorted octahedral geometry with an NiN6 chromophore coordinated through four N atoms of two bidentate L units and two N atoms of terminal thiocyanate in mutual cis orientation. The mononuclear units in 2 are engaged in intermolecular weak C-HS hydrogen bonding to give a 1D chain. Electrochemical electron transfer study reveals nearly-reversible responses to NiIII/NiII couple in acetontrile solutions. High-energy intraligand 1(p-p*) fluorescence at room temperature and intraligand 3(p-p*) phosphorescence in glassy solutions (MeOH at 77 K) are seen in all the complexes.

IPC Code: Int. Cl.8 C07F15/04; C07C251/02

 

Indian Journal of Chemistry

Vol. 47A, January 2008, pp. 18-24

 

Self-assembly of hydrogen-bonded networks of [Cu(HL)Cl](PF6) (HL = N,N-bis(2-pyridylmethyl)-1,3-diaminopropan-2-ol) into 1D chains: Formation of new submicrometer [Cu(HL)Cl](PF6) rods

Koushik Dhara, Partha Roy, Mario Manassero & Pradyot Banerjee*

Received 21 September 2007; revised 4 December 2007

A new mononuclear copper(II) complex [Cu(HL)Cl](PF6) (1) having an N4O-donor ligand (HL = N,N-bis(2-pyridylmethyl)-1,3-diaminopropan-2-ol) has been synthesized and structurally characterized by X-ray crystallography. 1 shows a 1D chain in the packing structure through intermolecular OH---Cl strong hydrogen bonding interaction (OH---Cl, 1.99(4) and the angle (OH---Cl) 163(4)). The packing structure of 1 also shows лл stacking [close contact 3.325a (a = 2-X,-Y,-Z)] of the large aromatic pyridine rings between adjacent chains. The 1D structure stabilized by this type of лл stacking interaction between adjacent chains leads to a 2D supramolecular network. A submicrometer rod structure of [Cu(HL)Cl](PF6) with a diameter of 580 nm and a length of several microns has been prepared by drop casting method from the methanolic solution of 1. The morphology of submicrometer rod of 1 has been studied by SEM. The driving force for the growth of [Cu(HL)Cl](PF6) rods is probably the strong intermolecular OH---Cl hydrogen bonding interaction along the 1D chain and лл stacking interaction between the adjacent chains.

IPC Code: Int. Cl.8 C07F1/08

 

Indian Journal of Chemistry

Vol. 47A, January 2008, pp. 25-31

 

New nine coordinated hydrated heavier lanthanide ethylenediaminetetraacetates containing hydrazinium cation: Crystal structure of N2H5[Dy(EDTA)(H2O)3](H2O)5

L Vikram & B N Sivasankar*

Received 21 March 2007; revised 21 October 2007

Some new nine coordinated hydrazinium lanthanide ethylenediaminetetraacetate hydrates N2H5[Ln(EDTA)(H2O)3](H2O)5 where Ln: Eu, Gd, Tb or Dy, have been prepared in aqueous media and characterized by chemical and elemental analyses, conductance, magnetic and spectral studies. The X-ray powder diffraction spectra of the complexes exhibit isomorphism in the series. The dysprosium complex has been prepared as a single crystal suitable for X-ray single crystal study and its analysis shows that the metal ion is nine coordinated with hexadentate tetravalent EDTA4- while three more coordination sites are occupied by water molecules. The simultaneous TG-DTA profiles of the complexes show multi step degradation involving dehydration, ligand pyrolysis and formation of respective metal oxides as end residues. The first stage of degradation provides clear evidence for the removal of five non-coordinated water molecules. The final residues have been identified and confirmed by TG-weight loss and X-ray powder diffraction technique.

IPC Code: Int. Cl.8 C07F5/00

 

Indian Journal of Chemistry

Vol. 47A, January 2008, pp. 32-36

 

Synthesis, structure and properties of [Pr(DMSO)5(H2O)2](μ-CN)[Co(CN)5]H2O

Wen-Tong Chen*, Xi-Rui Zeng, Ya-Ping Xu, Qiu-Yan Luo & Hua-Long Chen

Received 8 August 2007; revised 23 November 2007

A new cyano-bridged praseodymiumIII-cobaltIII complex [Pr(DMSO)5(H2O)2](μ-CN)[Co(CN)5]H2O, (1), has been synthesized via solution reaction and characterized by X-ray diffraction. The slightly distorted square-antiprism eightfold-coordinated Pr(III) and the approximately oriented octahedrally sixfold-coordinated Co(III) are linked by a cyano-bridge group to form a dinuclear complex. The [Pr(DMSO)5(H2O)2](μ-CN)[Co(CN)5] species are held together via hydrogen bonds to form a two-dimensional slab. The magnetic properties show that complex 1 exhibits antiferromagnetic interactions. IR and thermogravimetry-differential thermal analyses (TG-DTA) are also presented.

IPC Code: Int. Cl.8 C07F5/00; C07F15/06

 

Indian Journal of Chemistry

Vol. 47A, January 2008, pp. 37-42

 

Synthesis and crystal structure of square-planar and mixed ligand octahedral nickel(II) O,O-dicyclopentyl dithiophosphate complexes

Murat Taş*, Mehtap Yağan, Hmeyra Bati, Bekir Bati & Orhan Bykgng

Received 6 July 2007; revised 18 November 2007

Ammonium O,O-dicyclopentylphosphorodithioate (dcpdtp) has been synthesized from phosphorus pentasulphide and cyclopentanol in the presence of ammonia gas. Its complexes, I=[Ni(dcpdtp)2] and II= [Ni(bp)2(dcpdtp)2] (bp=4-benzylpiperidine), have been synthesized and their structures characterized by using UV-vis, IR spectroscopy, magnetic susceptibility measurements and X-ray single crystal structural analysis. The complexes crystallize in the triclinic system (space groups P ī) and exhibit a slightly distorted square planar [NiS4] and trans-octahedral [NiS4N2] geometry for the complexes I and II, respectively.

IPC Code: Int. Cl.8 C07F15/04

 

Indian Journal of Chemistry

Vol. 47A, January 2008, pp. 43-48

 

Novel method for the synthesis of zirconium(IV) chelate complexes from oxo-zirconium(IV) aryloxides

S C Chaudhry*, C Verma, S S Bhatt & N Sharma

Received 8 December 2006; revised 16 November 2007

Reaction of oxo-zirconium(IV) aryloxides with the composition ZrO(OAr)2 and ZrOCl(OAr) [where OAr = OC6H4NO2-4, OC6H4Cl-2, and - OC6H4(NO2)2- 2,4] with chelating ligands such as acetylacetone (acacH), 2-hydroxyacetophenone (hapH) and salicylaldehyde (salH) in Et2O yield eight coordinate chelate complexes with the composition Zr(acac)4, Zr(hap)4 and Zr(sal)4, as indicated by analytical, physico-chemical and infra-red spectral studies. The conclusive evidence for the formation of these zirconium(IV) chelates, contrary to the expected oxo-zirconium(IV) chelates of composition ZrO(chelate)2, has been obtained from the crystal structure determination of one of these zirconium(IV) chelates, Zr(acac)4 using X-ray technique. Present studies have thus provided a new method for the preparation of zirconium(IV) chelate complexes from oxo-zirconium(IV) aryloxides.

IPC Code: Int. Cl.8 C07F7/00

 

Indian Journal of Chemistry

Vol. 47A, January 2008, pp. 49-54

 

Kinetics and mechanism of amine-catalysed solvolysis of azlactone in water-dioxan mixtures

Amel M Ismail

Received 10 June 2007; revised 25 October 2007

The effect of replacing solvent water by dioxan up to 50% v/v on the rate of catalytic-amine solvolysis of azlactone has been measured spectrophotometrically in the temperature range 40-60C. Addition of an organic solvent to water largely decreases the rate of ring- opening process. Such an effect was found to diminish in the region of lower relative permittivity. The reaction rate constants are analyzed and discussed in terms of solvent effect and nucleophilicity of amines. G gradually decreases as a function of increasing [water], due to a complex and quasi-mirror image compensation of H and S. The variation of H versus S is linear. The catalytic coefficient, kAm, for amine has been estimated from the general linear equation, kobs= k o + kAm [Amine]. The binary solvent mixtures used give an unusual range of properties. The plot of log kAm versus log [H2O] show two linear segments with intersection at 33.3 mol dm-3 [H2O]. The correlation between log kAm and reciprocal of the relative permittivity is non-linear, while that between log kAm versus pKa is linear. All these observations are consistent with the suggested mechanism.

 

 

Indian Journal of Chemistry

Vol. 47A, January 2008, pp. 55-57

 

Synthesis and characterisation of Sb2Zn2Cl4(OPri)6, MSb2Cl2(OPri)6
(M = Be, Mg, Zn), and M2Ti4Cl4(OPri)16 (M = Mg, Zn)

Jayshree Shahani & Anirudh Singh*

Received 30 April 2007; revised 6 December 2007

Reactions of MCl2 (M = Be, Mg, Zn) with Sb(OPri)3 and Ti(OPri)4 in desired molar ratios in benzene afford structurally interesting derivatives of the types MSb2Cl2 (OPri)6 (M Be(1), Mg(2), Zn(3)), Sb2Zn2Cl4(OPri)6(4), M2Ti4Cl4(OPri)16 (M = Mg(5), Zn(6)). All these derivatives have been characterized by elemental (Be, Mg, Zn, Sb, Cl, Ti) analyses, isopropoxo groups determinations, molecular weight measurements, and spectroscopic studies.

IPC Code: Int. Cl.8 C07F3/00; C07F3/02; C07F3/06; C07F7/28; C07F9/90

 

Indian Journal of Chemistry

Vol. 47A, January 2008, pp. 58-61

 

Heterobimetallic penta- and hexa-coordinated organotin (IV) complexes at different temperatures

Rajesh Malhotra*, Jyoti Mehta, Kiran Bala & Ashok K Sharma

Received 4 June 2007; revised 26 November 2007

The reactions of triorganotin (IV) chloride with ferrocenyl aroylhydrazone derived from condensation of acetylferrocene and aromatic acidhydrazide yield heterobimetallic penta- and hexa-coordinated organotin(IV) complexes of the type R3Sn(L) and R3Sn(HL)Cl (where R=Me, Et or Ph HL=ferrocenyl aroylhydrazone). The ligands behave as bidentate, coordinating through carbonyl oxygen and azomethine nitrogen in keto and enolisation of keto form at low temperature and at room temperature respectively. The isolated complexes have been characterized by elemental analysis, molar conductance, infrared and NMR (1H, 13C and 119Sn) spectral data. The ligands and their organotin complexes have been evaluated for antifungal activity against Alternaria alternata, Fusarium oxysporum and Rhizoctonia solani, as well as antibacterial activity against gram negative, (Escherichia coli) and gram positive bacilli (Bacilli subtilis) at 28C. The activity of the ligands is enhanced on complexation with triorganotin (IV) chloride.

IPC Code: Int. Cl.8 C07F7/22

 

Indian Journal of Chemistry

Vol. 47A, January 2008, pp. 62-65

 

Thermochemistry of the compounds M(C4H7O5)xnH2O(s) (x = 1 and 2, n = 1 and 0) of several kinds of biologically active metal ions (M = Na, K, Mg and Ca) with L-threonic acid

You-Ying Di*, Sheng-Li Gao & San-Ping Chen

Received 19 July 2007; revised 2 October 2007

The constant-volume energies of combustion () of the solid hydrated L-threonate, M(C4H7O5)xnH2O(s) (M = K, Na, Mg and Ca; x = 1 and 2; n = 1 and 0), have been determined to be [Na(C4H7O5)H2O, s] = (10241.955.14) J g-1, [K(C4H7O5)H2O, s]=(9103.124.71) J g-1, [Mg(C4H7O5)2 H2O, s] = (10407.344.67) J g-1 and [Ca(C4H7O5)2H2O, s] = (10097.09 5.26) J g-1 by an RBC-II precision rotating-bomb combustion calorimeter at 298.15 K. The standard molar enthalpies of combustion of these compounds () have been calculated to be: (1802.380.91), (1748.470.91), (3383.07 1.21) and (3130.65 1.21) kJmol-1. The standard molar enthalpies of formation of these compounds () have been derived to be: (1265.841.06), (1292.591.06),(2571.681.63) and (2653.341.08) kJmol-1 from the combination of the standard molar enthalpies of combustion of these compounds with other auxiliary thermodynamic quantities.

 

Indian Journal of Chemistry

Vol. 47A, January 2008, pp. 66-70

 

Excess molar volumes and viscosity deviations of binary liquid mixtures of N-methylacetamide with ethyl acetate, ethyl chloroacetate and ethyl cyanoacetate

Sathyanarayana Boodida, Ranjith Kumar Bachu, Savitha Jyostna Tangeda & Satyanarayana Nallani*

Received 27 April 2007; revised 14 November 2007

The values of density and viscosity for the binary liquid mixtures of N-methylacetamide with aliphatic esters (ethyl acetate, ethyl chloroacetate and ethyl cyanoacetate) have been measured over the entire range of composition at T = 303.15 to 318.15 K. Using these data, excess molar volumes (VE) and deviations in viscosity (Dh) have been calculated. The results have been correlated with the Redlich-Kister type polynomial equation to derive the binary coefficients and standard errors.

 

Indian Journal of Chemistry

Vol. 47A, January 2008, pp. 71-74

 

Determination of the polyacid dissociation constants of glycyrrhizic acid

Chun-Xiang Zeng & Qin Hu*

Received 29 March 2007; revised 14 November 2007

Determination of the three stepwise dissociation constants of glycyrrhizic acid in water by potentiometric titration method is described here. The experimental data have been processed with a stepwise linear regression and simultaneous equations algorithm. The three dissociation constants of glycyrrhizic acid assayed by the proposed method are 3.98 (pKa1), 4.62 (pKa2) and 5.17 (pKa3), respectively. The distribution of the different charged ions of glycyrrhizic acid under different pH values has been simulated with Microsoft Excel software. The results are accurate and useful for further pharmacological and pharmacal studies of glycyrrhizic acid.

 

Indian Journal of Chemistry

Vol. 47A, January 2008, pp. 75-80

 

Enantioseparation condition of D, L-tryptophan using ligand exchange chromatography

Hongyuan Yan & Kyung Ho Row*

Received 7 March 2007; revised 15 November 2007

Chiral recognition mechanism and enantioseparation conditions of tryptophan enantiomers using ligand exchange chromatography are reported here. The effect of different kinds and concentration of ligands, bivalent copper ion, organic modifier, pH of mobile phase, and temperature on enantioseparation has been evaluated. The results show that the enantioselectivity is strongly affected by the pH and the ligand concentration. Under the optimum condition, baseline separation of the two enantiomers has been obtained on a C18 column with a resolution of 3.42 in less than 30 min using methanol-water solution (20:80 v/v) as mobile phase containing 3.0 mmolL-1 L-phenylalanine and 0.5 mmolL-1 copper sulphate. Thermodynamic data (ΔΔH and ΔΔS) obtained by Vant Hoff plots reveal that the enantioseparation is an enthalpy-controlled process. The mechanism of chiral discrimination is based on the stabilities of the copper(II) binary complexes and their ternary diasteremeric complexes with amino acids formed in solution and stationary phase. The proposed method has been successfully used for the quality evaluation of tryptophan enantiomers.

IPC Code: Int Cl.8 G01N 30/00