Indian Journal of Chemistry

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

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VOLUME 44A

NUMBER 11

NOVEMBER  2005

 

CONTENTS

Papers

 

2195

 

Electronic structure of seven component model protein chains: Effect of electron correlation

 

 

 

 

 

 

 

Shyam Kishor & A K Bakhshi*

 

 

 

 

Quasi-particle band structure results of seven homopolypeptides with aliphatic side chains obtained using double zeta basis set have been used as input to calculate the electronic density of states of periodic and aperiodic model protein chains on the basis of negative factor counting method in tight binding approximation. The results are compared to the electronic structure obtained from ab initio Hartree Fock band structure results for the same systems, obtained using minimal basis set and double zeta basis set respectively.

 

 

2202

 

Aquo complexes of simple Cu+, Ag+ and Au+ ions and the acidities of metal aquo ions. A heat of hydration analysis and PM3 calculations

 

 

 

 

 

 

 

 

Jnan Prakash Naskar & Dipankar Datta*

 

 

 

 

The heats of hydration  of some metal ions (except Cu+, Ag+ and Au+) with charge Z varying from +1 to +4 can be reproduced with an average error of 3.8 (± 2.7) % by the equation: . Application of this equation to the DH0 values of Cu+, Ag+ and Au+ reveals that while no aquo complex is possible for simple Au+ ion in water, simple Cu+ ion can be 2 or 4 coordinated and Ag+ ion 2 coordinated in water. The acid dissociation behaviour of the aquo ion of some metal ions has also been studied by PM3 calculations.

 

 

2208

 

Liquid phase benzylation over iron incorporated sulphated zirconia systems

 

 

 

 

 

 

 

H Suja & S Sugunan*

 

 

 

 

Iron incorporated sulphated zirconia systems have been investigated for benzylation reaction. Incorporation of iron improves the surface properties of sulphated zirconia. Surface area and acidity is enhanced and tetragonal phase is stabilized with no trace of monoclinic phase. All the systems show high catalytic activity and selectivity for monoalkylation.

 

 

2214

 

Synthesis and structural characterization of cerium incorporated manganese oxide OMS-2 type catalysts

 

 

 

 

 

 

 

 

R Jothiramalingam, B Viswanathan* &
T K Varadarajan

 

 

 

 

Cerium incorporated ordered phase of manganese oxide OMS (octahedral molecular sieve) materials have been synthesized by ion exchange and hydrothermal methods. The cerium incorporated OMS-2 type catalysts have been prepared from potassium birnessite as well as from potassium containing cryptomelane. XRD, TGA, BET and SEM analyses have been used to characterize the cerium incorporated manganese oxide OMS-2 materials.

 

 

2218

 

Stopped-flow kinetic investigations of
one-electron transfer reactions of
4,4
¢-diaminodiphenylmethane and its radical cation in aqueous solution

 

 

 

 

 

C Sankar, P Aravindan* S Anandan &
P Maruthamuthu*

 

 

 

 

The oxidation of 4,4¢-diaminodiphenylmethane (DADPM) by metal ion (Ce4+); oxoanions (MnO4- and Cr2O72-), peroxides (peroxomonosulfate, peroxodisulfate and H2O2), and halogens (Cl2, Br2 and I2), to the radical cation DADPM·+, and further oxidation to the product monocation DADPM+ has been investigated by stopped-flow technique. The reactions follow a total second-order kinetics; first-order each with respect to the [DADPM] or [DADPM·+] and [oxidant].

 

2228

 

Aqua pyridine complex of protoporphyrinato IX iron(III): Effect of ligand binding, surfactant concentration and proton coupling on redox potential

 

 

 

 

 

Diganta Kumar Das & Okhil K Medhi*

 

 

 

 

Binding of one molecule of pyridine to hemin with water as the other ligand gives a very large positive shift in mid-point potential of the Fe(II)/Fe(III) couple. The high value of mid-point potential is due to the formation of the highly stable bis pyridine complex of hemin in reduced state. The aqua pyridine complex also shows pH dependence of redox potential. There are two proton coupled electron transfer sites detected involving one carboxylate of the heme and the coordinated water molecule.

 

 

2233

 

Electrochemical characterization of polypyrrole/cobalt ferrite composite films for oxygen reduction

 

 

 

 

 

 

 

 

 

M Malviya, J P Singh & R N Singh*

 

 

 

 

Electrodeposited films of polypyrrole  and its composite with CoFe2O4 nanoparticles, incorporated with a charge compensating electrolyte anion, ClO4-, on polished and pretreated graphite electrodes have been prepared and characterized. The porosity of the polymer matrix increases slightly on incorporation of oxide nano-particles. The sum of the film and solution resistances, though higher for the composite electrode, remains practically constant under cathodic polarization conditions. In contrast to a non-composite electrode of the same oxide, the composite electrode exhibits much better electrocatalytic activity towards O2 reduction reaction.

 

 

2240

 

Synthesis, characterization and catalytic activity of μ-phenoxodicopper complexes with bi-Schiff bases derived from α-amino acids

 

 

 

 

 

 

Jun-Fa Wei* & Xian-Ying Shi

 

 

 

 

Several dicopper complexes and relevant dimetal complexes have been synthesized with the bi-Schiff base ligands formed by 2,6-diformyl-4-methylphenol with glycine, L-phenylalanine, L-histidine or histamine. Using the Cu2 complexes as models of dopamine β-hydroxylase and peptidylglycine α-hydroxylation monooxygenase the epoxidation of styrene with PhIO as the monooxygen donor has been investigated. The results show that styrene oxide is the main product of epoxidation of styrene and no benzaldehyde is formed as the by-product.

 

 

2247

 

New lanthanide(III) complexes of biologically active 2,3–disubstituted quinazoline–4-(3H)-one: Synthesis, characterization and biological studies

 

 

 

 

 

 

K B Gudasi*, R V Shenoy, R S Vadavi, M S Patil & S A Patil

 

 

 

 

 

 

2255

 

Transition metal complexes of cis-3,7-dimethyl-2,6-octadienthiosemicarbazone: Synthesis, characterization and biocidal studies#

 

 

 

 

 

 

 

Renu Sharma, Anil K Bansal & Meena Nagar*

 

 

 

 

 

Notes

 

2259

 

A simple reduction route to carbon hollow spheres

 

 

 

 

 

Yucai Hu

 

 

 

 

 

 

 

 

2262

 

Photocatalytic degradation of phenol as a model pollutant by immobilized TiO2

 

 

 

 

 

 

 

 

 

 

 

Sanjay R Thakare* & N S Bhave

 

 

 

 

 

 

2266

 

Photoreduction of congo red by ascorbic acid and EDTA over cadmium sulphide as photocatalyst

 

 

 

 

 

 

Shilpa Kothari, Ritu Vyas, Rakshit Ameta & Pinki B Punjabi*

 

 

 

 

CdS                                    h+   +  

h+   +   e-                   heat

D¯   +   H+             DH ¯

R   +   h+                  R+

 

 

2270

 

Corrosion and inhibition kinetics of PVA polymer on carbon steel in sulfuric acid solution

 

 

 

 

 

 

 

Jyotsna Shukla & K S Pitre*

 

 

 

 

The inhibitive action of polyvinyl acetate towards the corrosion of carbon steel in 2N H2SO4 solution has been investigated and a new voltammetric method to determine the corrosion rates at short time intervals has been developed. The corrosion inhibition efficiency of polyvinyl acetate is 91% after 24 hours.

 

 

2274

 

Enthalpy of dissolution of the complex Zn(Leu)SO4×1/2H2O(s)

 

 

 

 

 

 

 

 

 

You-Ying Di*, Zhi-Cheng Tan &
Sheng-Li Gao

 

 

 

 

Molar enthalpies of dissolution of [ZnSO4×7H2O (s) and Leu (s)] mixture [n (ZnSO4×7H2O) : n (Leu) = 1 : 1 ] and the complex Zn(Leu)SO4×1/2H2O (s) in 100 cm3 of 2 mol×dm-3 HCl at (298.15 ± 0.001) K have been determined to be = -(84.943 ± 0.090) kJ×mol-1 and = (55.967 ± 0.060) kJ×mol-1, respectively, using an isoperibol solution-reaction calorimeter. The standard molar enthalpy of formation of the complex Zn(Leu)SO4×1/2H2O(s) has been found to be  [Zn(Leu)SO4×1/2H2O, s, 298.15 K] = - (1998.155 ± 0.965) J×mol-1.

 

 

Authors for correspondence are indicated by (*)

 

 

 

 

 

Indian Journal of Chemistry

Vol. 44A, November 2005, pp. 2195-2201

 

Electronic structure of seven component model protein chains:
Effect of electron correlation

        Shyam Kishor & A K Bakhshi*

        Received 26 April 2005; revised 14 September 2005

Quasi-particle band structure results of seven homopolypeptides with aliphatic side chains obtained using double zeta basis set have been used as input to calculate the electronic density of states of periodic and aperiodic model protein chains on the basis of negative factor counting method in tight binding approximation. The results obtained are compared to the electronic structure obtained from ab initio Hartree Fock band structure results for the same system, obtained using minimal basis set and double zeta basis set respectively.

Indian Journal of Chemistry

Vol. 44A, November 2005, pp. 2202-2207

 

Aquo complexes of simple Cu+, Ag+ and Au+ ions and the acidities of
metal aquo ions. A heat of hydration analysis and PM3 calculations

Jnan Prakash Naskar and & Dipankar Datta*

Received 5 January 2005; revised 14 September 2005

It is shown that the heats of hydration (DH0) of some 37 metal ions (excluding Cu+, Ag+ and Au+) with charge Z on them varying from +1 to +4 can be reproduced with an average error of 3.8 (± 2.7) % by the following equation:

In the above equation N is Avogadro's number, e charge of an electron, e0 the permittivity of vacuum, e the relative permittivity of water and r Shannon's crystal ionic radii; the factor of 1012 is introduced so that r is expressed in pm. Application of this equation to the DH0 values of Cu+, Ag+ and Au+ reveals that while no aquo complex is possible for simple Au+ ion in water, simple Cu+ ion can be 2 or 4 coordinated and Ag+ ion 2 coordinated in water. It is realised This indicates that the appearance of the factor of 53 pm in the above equation is a consequence of the hydration structure around a metal ion. Further, the experimental pKa values for some 21 metal aquo ions are found to correlate linearly (correlation coefficient = 0.975) with the gas phase enthalpy changes DH0 DHo for the reaction (i)

 

[M(H2O)n]Z+ + m H2O ¾® [M(H2O)n+m-p-1(OH)](Z-1)+ +p H2O + H+(i)

 

 calculated at the PM3 level. It is concluded that in In exceptional cases, some metal ions (e.g. Hg2+) undergo expansion of the coordination spheres upon deprotonation and some metal ions (e.g. Tl3+) lose water molecule(s) with deprotonation.

 

 

 

  

 

Indian Journal of Chemistry

Vol. 44A, November 2005, pp. 2208-2213

 

Liquid phase benzylation over iron incorporated sulphated zirconia systems

H Suja & S Sugunan*

Received 31 December 2002; revised 14 September 2005

The utility of iron incorporated sulphated zirconia for benzylation reaction has been studied. Physico-chemical characterization of the prepared systems have been achieved using data on XRD, laser Raman spectra, IR spectra, surface area, pore volume, EDX and acidity. Incorporation of iron improves the surface properties of sulphated zirconia. Surface area and acidity is enhanced and tetragonal phase is stabilized with no trace of monoclinic phase. All the systems show high catalytic activity and selectivity for monoalkylation.

IPC Code: Int. Cl.7 B01J21/06; C07B37/00

 

Indian Journal of Chemistry

Vol. 44A, November 2005, pp. 2214-2217

 

Synthesis and structural characterization of cerium incorporated
manganese oxide OMS-2 type catalysts

R Jothiramalingam, B Viswanathan* & T K Varadarajan

Received 29 November 2004; revised 14 September 2005

Cerium incorporated ordered phase of manganese oxide OMS (octahedral molecular sieve) materials have been synthesized by ion exchange and hydrothermal methods. The cerium incorporated OMS-2 type catalysts have been prepared from potassium birnessite as well as from potassium containing cryptomelane. XRD, TGA, BET and SEM analyses have been used to characterize the cerium incorporated manganese oxide OMS-2 materials.

IPC Code: Int. Cl.7 B01J29/00

 

Indian Journal of Chemistry

Vol. 44A, November 2005, pp. 2218-2227

 

Stopped-flow kinetic investigations of one-electron transfer reactions of
4,4¢-diaminodiphenylmethane and its radical cation in aqueous solution

 

C Sankar, P Aravindan*, S Anandan & P Maruthamuthu,*

Received 8 February 2005; revised 23 August 2005

The oxidation of 4,4¢-diaminodiphenylmethane (DADPM) by metal ion (Ce4+); oxoanions [MnO4- and Cr2O72-], peroxides [peroxomonosulfate (PMS), peroxodisulfate (PDS) and H2O2], and halogens [Cl2, Br2 and I2], to the radical cation DADPM·+, and further oxidation to the product monocation DADPM+ by the above mentioned oxidants has been investigated by stopped-flow technique. A probable mechanism has been proposed. The reactions follow a total second-order kinetics, first-order each with respect to the [DADPM] or [DADPM·+] and [oxidant]. In addition, the radical cation DADPM·+ oxidizes sulfite (SO32-), thiosulfate (S2O32-), dithionite (S2O42-) and metabisulfite (S2O52-) to regenerate the parent compound DADPM. The rate constants for these reactions have also been estimated. Reactivity for the formation of DADPM follows the decreasing order in the case of oxoanions (MnO4- > Cr2O72- > Ce(IV)) and peroxides (S2O82- > HSO5- > H2O2) which is in agreement with the redox potentials, while the reactivity trend for halogens is found to be I2 > Br2 > Cl2 which is not in agreement with the redox potentials. The observed rate constants for electron transfer have been correlated theoretically using Marcus theory.

IPC Code: Int.Cl.7 C07B33/00

Indian Journal of Chemistry

Vol. 44A, November 2005, pp. 2228-2232

 

Aqua pyridine complex of protoporphyrinato IX iron(III): Effect of
ligand binding, surfactant concentration and proton coupling on redox potential

Diganta Kumar Das & Okhil K Medhi*

Received 7 April 2005; revised 2 September 2005

Binding of one molecule of pyridine to hemin with water as the other ligand gives a very large positive shift in mid-point potential of the Fe(II)/Fe(III) couple. The mid-point potential of the aqua pyridine complex are -0.076 V, -0.046 V,-0.012 V and +0.008 V (versus Ag-AgCl electrode) in water, SDS, TX-100 and CTAB micelles, respectively. The anodic shift in potential on binding one molecule of pyridine to hemin is 0.290 V in SDS and TX-100 and 0.250 V in CTAB. The high value of mid-point potential is due to the formation of the highly stable bis pyridine complex of hemin in reduced state. The average anodic shift in mid-point potential of the complex in aqueous micelles with respect to water is +80 mV in CTAB, +64 mV in TX-100 and +30 mV in SDS. The aqua pyridine complex also shows pH dependence of redox potential. There are two proton coupled electron transfer sites detected involving one carboxylate of the heme and the coordinated water molecule.

IPC Code: Int. Cl.7 C25B

 

Indian Journal of Chemistry

Vol. 44A, November 2005, pp. 2233-2239

 

Electrochemical characterization of polypyrrole/cobalt ferrite composite films for oxygen reduction

M Malviya, J P Singh & R N Singh*

Received 3 March 2005; revised 1 September 2005

Electrodeposited films of polypyrrole (PPy) and composite of PPy and CoFe2O4 nanoparticles, incorporated with a charge compensating electrolyte anion (ClO4-) have been obtained on polished and pretreated graphite electrodes and characterized by cyclic voltammetry, impedance and cathodic polarization techniques. The study of films in a 0.8 mol dm-3 LiClO4 + 5 mmol dm-3 KOH solution indicates that the porosity of the polymer matrix somewhat increases with incorporation of oxide nano-particles. The average apparent diffusion coefficient (Da) of the dopant (ClO4-) has been observed to be ~2 times higher in the composite film compared to pure PPy film. The sum of the film and solution resistances, though higher for the composite electrode, remains practically constant under cathodic polarization conditions. In contrast to a non-composite electrode of the same oxide, the composite electrode exhibits much better electrocatalytic activity towards the O2 reduction reaction.

IPC Code: Int. Cl.7 B01J23/74; C25D; G01R

Indian Journal of Chemistry

Vol. 44A, November 2005, pp. 2240-2246

 

Synthesis, characterization and catalytic activity of μ-phenoxodicopper complexes with bi-Schiff bases derived from α-amino acids

Jun-Fa Wei* & Xian-Ying Shi

Received 8 July 2005; revised 3 September 2005
Several dicopper complexes and relevant dimetal complexes have been synthesized with the bi-Schiff base ligands formed by 2,6-diformyl-4-methylphenol (HDFA) with glycine, L-phenylalanine, L-histidine or histamine, and characterized by elemental analysis, IR, UV-vis, CD, EPR, and XPS. Using the Cu2 complexes as models of dopamine β-hydroxylase (DβH) and peptidylglycine α-hydroxylation monooxygenase (PHM), we have investigated the epoxidation of styrene with PhIO as the monooxygen donor. The results show that styrene oxide is the main product of epoxidation of styrene, and that no benzaldehyde is formed as the by-product. Turnover numbers (TNs) of each model complex in epoxidation of styrene are 4.7, 3.1, 2.8, and 2.5 mol−1 Cu2, for the complex derived from glycine, phenylalanine, L-histidine, and histamine, respectively. EPR study reveals that a hypervalent iodine oxo intermediate CuCu←O─IPh might be formed as the active species, ruling out the possibility of formation of the hypervalent metal-oxo species Cu(III)═O in the oxidation course.

IPC Code: Int. Cl.7 C07C251/02; C07F1/08

Indian Journal of Chemistry

Vol. 44A, November 2005, pp. 2247-2254

 

New lanthanide(III) complexes of biologically active 2,3-disubstituted quinazoline-4-(3H)-one: Synthesis, characterization and biological studies

K B Gudasi*, R V Shenoy, R S Vadavi, M S Patil & S A Patil

Received 3 May 2005; revised 28 August 2005

A number of lanthanide(III) complexes with 2-pyridine-2-yl-3-[pyridine-2-carboxylideneamino]-1,2-dihydroquinazolin-4-(3H)-one (PPCADQ) have been synthesized. On the basis of magnetic studies, thermal studies, IR, NMR, UV-vis and EPR spectra, the complexes have been formulated as [Ln(PPCADQ)2(H2O)2(NO3)](NO3)2 where Ln = La(III), Pr(III), Nd(III), Sm(III), Eu(III), Gd(III), Tb(III), Dy(III) and Y(III). The ligand behaves in tridentate fashion. The ligand and complexes have been evaluated for their antibacterial and antifungal activities.

IPC Code: Int. Cl.7 C07F5/00

 

Indian Journal of Chemistry

Vol. 44A, November 2005, pp. 2255-2258

 

Transition metal complexes of cis-3,7-dimethyl-2,6-octadienthiosemicarbazone: Synthesis, characterization and biocidal studies

Renu Sharma, Anil K Bansal & Meena Nagar*

Received 1 June 2005; revised 2 September 2005

Transition metal complexes containing a bidentate N,S donor ligand, i.e., cis-3,7-dimethyl-2,6-octadienthiosemicarba-
zone (CDOTSC) have been synthesized and characterized by elemental analysis, molar conductance, magnetic susceptibility measurements and various spectral (ir, eletronic, and 1H nmr) studies. All the metal complexes are [ML2Cl2] type, where M = CoII, NiII, CuII, ZnII, CdII and HgII; L = CDOTSC. The ligand CDOTSC acts as a bidentate ligand in all the complexes. Distorted octahedral geometry for CuII complex and octahedral geometries for all other complexes are proposed. The newly synthesized ligand (CDOTSC) and its metal complexes have been screened at 37ºC in vitro for their antimicrobial activity against the bacterial species, Escherichia coli and Staphylococcus aureus, and the fungal strains, Aspergillus niger and Candida albicans. All the complexes and ligand CDOTSC possess strong inhibitory action against bacteria and fungi. The antimicrobial activities of the complexes are stronger than those of ligand CDOTSC itself.

IPC Code: Int. Cl.7 C07F1/08; C07F3/06; C07F3/08; C07F3/10; C07F15/06; C07F15/104

 

 

  

Indian Journal of Chemistry

Vol. 44A, November 2005, pp. 2259-2261

A simple reduction route to carbon hollow spheres

Yucai Hu

Received 14 June 2005; revised 2 September 2005

Carbon hollow spheres with average diameter of 450-500 nm and thickness of 25 nm have been synthesized by a simple reaction of hexachlorobenzene with metal sodium at a low temperature of 400°C. Formation mechanism of the carbon hollow spheres is also discussed.

IPC Code: Int. Cl.7 B82B1/00;C01B31/00

Indian Journal of Chemistry
Vol. 44A, November 2005, pp. 2262-2265

Photocatalytic degradation of phenol as a model pollutant by immobilized TiO2

Sanjay R Thakare, * & N S Bhave

Received 4 November 2004; revised 29 August 2005

TiO2 has been immobilized in polyvinyl alcohol polymer network and successfully used for the degradation of phenol. The prepared PVA-TiO2 composite is completely insoluble in water. The diffuse reflectance study shows that the prepared polymer composite shows absorption in visible region as compared to the bare titanium dioxide. The immobilized TiO2 shows remarkable degradation activity in the presence of UV as well as visible light. In the presence of visible light, after 5 hours irradiation, 72% degradation of phenol takes place while in the presence of UV light and 5 hours irradiation, 89% degradation of phenol takes place. The support material (polyvinyl alcohol) is not degraded during the photocatalysis reaction and the net photocatalytic efficiency does not decrease after five runs. Diffuse reflectance study shows that the polymer composite is stable during the photocatalysis reaction for a short time.

IPC Code: Int. Cl.7 B01J21/06; C02F1/58

Indian Journal of Chemistry

Vol. 44A, November 2005, pp. 2266-2269

Photoreduction of congo red by ascorbic acid and EDTA over cadmium sulphide as photocatalyst

Shilpa Kothari, Ritu Vyas, Rakshit Ameta &
Pinki B Punjabi*

The photoreduction of congo red in presence of CdS and ascorbic acid or EDTA has been carried out. The effect of different parameters like pH, light intensity, concentrations of congo red and reductants and amount of semiconductor on the rate of photocatalytic reaction has been studied. On the basis of observed data, a tentative mechanism for the photoreduction of congo red has been proposed.

IPC Code: Int. Cl.7 C7B31/00; C09B

 

  

Indian Journal of Chemistry

Vol. 44A, November 2005, pp. 2270-2273

 

Corrosion and inhibition kinetics of PVA polymer on carbon steel in
sulfuric acid solution

Jyotsna Shukla  & K S Pitre*

Received 23 April 2004, revised 23 August 2005

A new voltammetric method to determine the corrosion rates at short time intervals has been developed. Variation of metal corrodibility, solution corrosiveness and corrosion rates have been reported as a function of time. The corrosion inhibition efficiency of PVA (polyvinyl acetate) is 91% after 24 hours. Using the proposed method it is also possible to determine simultaneously, the corrosion rates with respect to Fe(II) and Fe(III).

IPC Code: Int. Cl.7 G01N17/00

 

Indian Journal of Chemistry

Vol. 44A, November 2005, pp. 2274-2278

 

Enthalpy of dissolution of the complex Zn(Leu)SO4×1/2H2O(s)

 

You-Ying Di*, Zhi-Cheng Tan & Sheng-Li Gao

Received 21 February 2005; revised 12 September 2005

Molar enthalpies of dissolution of [ZnSO4×7H2O (s) and Leu (s)] mixture [n (ZnSO4×7H2O) : n (Leu) = 1 : 1 ] and the complex Zn(Leu)SO4×1/2H2O (s) in 100 cm3 of 2 mol×dm-3 HCl at (298.15 ± 0.001) K have been determined to be = -(84.943 ± 0.090) kJ×mol-1 and = (55.967 ± 0.060) kJ×mol-1, respectively, using an isoperibol solution-reaction calorimeter. The standard molar enthalpy of formation of the complex Zn(Leu)SO4×1/2H2O(s) has been found to be  [Zn(Leu)SO4×1/2H2O, s, 298.15 K] =-(1998.155 ± 0.965) J×mol-1, on the basis of experimental values of enthalpies of dissolution with some auxiliary thermodynamic data through a designed Hess thermochemical cycle. The constant-volume combustion energy of the complex Zn(Leu)SO4×1/2H2O (s) has been measured to be DcE /J×g-1 =-(9971.85 ± 11.27) by a precision rotating bomb combustion calorimeter at 298.15 K. The standard molar enthalpy of combustion and formation of the compound have been calculated to be  =-(3007.889 ± 3.399) kJ×mol-1 and  [Zn(Leu)SO4×H2O, s] =-(2001.251 ± 3.503) J×mol-1. The relative deviation of results obtained from the two calorimetric methods agree with each other and is within ± 0.2%.