Preparation, structural characterization and biological evaluation of l-tyrosinate metal ion complexes

Article abstract of DOI:10.1016/j.molstruc.2007.08.027

The complexes formed between different metal ions and biological molecules like amino acids play an important role in human life. Sn(II), Sn(IV), Zn(II), Cd(II), Hg(II), Cr(III), Fe(III), La(III), ZrO(II) and UO₂(II) complexes are synthesized w

Full text of DOI:10.1016/j.molstruc.2007.08.027

Available online at www.sciencedirect.com
Journal of Molecular Structure 881 (2008) 28–45
www.elsevier.com/locate/molstruc
Preparation, structural characterization and biological evaluation
of L-tyrosinate metal ion complexes
a,
b
a
Moamen S. Refat *, Sabry A. El-Korashy , Ahmed S. Ahmed
a
Department of Chemistry, Faculty of Education, Port Said, Suez Canal University, Mohamed Ali Street, Port Said, Egypt
b
Department of Chemistry, Faculty of Science, Ismalia, Suez Canal University, Ismalia, Egypt
Received 18 April 2007; received in revised form 17 August 2007; accepted 20 August 2007
Available online 4 September 2007
Abstract
The complexes formed between different metal ions and biological molecules like amino acids play an important role in human life.
Sn(II), Sn(IV), Zn(II), Cd(II), Hg(II), Cr(III), Fe(III), La(III), ZrO(II) and UO2(II) complexes are synthesized with L-tyrosine (tyr).
These complexes are characterized by elemental analysis, molar conductance, magnetic measurements, mass, IR, UV–vis and 1H
NMR spectra as well as thermogravimetric analysis (TGA/DTG). It has been found from the elemental analysis and the thermal studies
that the ligand behaves as bidentate ligand forming chelates with 1:3 (metal:ligand) stoichiometry for trivalent metals and 1:2 for divalent
and tetravalent metals. The molar conductance measurements of the complexes in DMSO indicate that the complexes are non-electro-
lyte. The activation energies and other kinetic parameters were calculated from the Coats–Redfern and Horowitz–Metzger equations.
The biological activities of the metal complexes have also been studied against different bacteria and fungi.
ꢀ 2007 Elsevier B.V. All rights reserved.
Keywords: L-Tyrosine; Microbiological investigation; Infrared spectra; Thermogravimetric analyses
1. Introduction
are close to those of phenyl alanine itself. However, this
oxygen does appear to coordinate to Cu(II) in some dipep-
tide complexes [4] and X-ray analysis of [Cu(L-tyr)2]
[L-tyr = L-tyrosinate (1ꢀ)] shows an abnormally short
Cu-phenyl ring distance [5].
Amino acids and their compounds with different metal
ions play an important role in biology, pharmacy and
industry [1]. Tyrosine (Tyr), 2-amino-3-(4-hydroxyphe-
nyl)-propanoic, H2L, is non-essential amino acid for
human development and precursor for the synthesis of thy-
roid hormones and select neurotransmitters, such as dopa-
mine and norepinephrine, may be considered essential by
the brain [2]. In plants, solar energy is used to extract elec-
trons from water, producing atmospheric oxygen. This is
conducted by Photosystem, where a redox ’’triad’’ consist-
ing of chlorophyll, a tyrosine, and a manganese cluster,
governs an essential part of the process [3].
For a number of metalloproteins of biological impor-
tance it assumed [6] that the phenolate oxygen in tyrosine
acts as a metal ion binding site. Extensive investigations
have therefore been made to establish the complex-forming
properties of transition metal ions with tyrosine, with
special regard to the participation of phenolate group in
complex formation [7]. The phenolic hydroxyl group in
o-tyrosine is in a sterically more favorable position for
coordination to the metal ion in its complexes. Letter and
Bauman [8] made a comparative study of the copper(II)
complexes of tyrosine, m-tyrosine, and o-tyrosine (4-, 3-,
and 2-hydroxyphenylalanine, respectively; H2A). From
the absorption band at 390 nm, indicative of the cop-
per(II)-phenolate interaction for o-tyrosine, they assumed
direct coordination of the phenolate oxygen at pH 10.
A review of the literature on tyrosine suggests that the
phenolic oxygen does not participate in coordination reac-
tion to metal ions with the result that formation constants
*
Corresponding author.
E-mail address: msrefat@yahoo.com (M.S. Refat).
0022-2860/$ - see front matter ꢀ 2007 Elsevier B.V. All rights reserved.
doi:10.1016/j.molstruc.2007.08.027

M.S. Refat et al. / Journal of Molecular Structure 881 (2008) 28–45
29
The coordinate of L-tyrosine with rare earth element
Eu3+ was investigated in solution by ultraviolet and was
proved the molar ratio was 1:2, and then the solid complex
was prepared by coprecipitation method [9].
metal:ligand ratio), the metal salt was added to the tyrH-
LiOHÆH2O solution. Precipitation was almost instanta-
neous, but stirring with heating were continued for
15 min. The Sn(II) complex was filtered, washed with hot
water (25 ml), and dried in vacuo over anhydrous CaCl2.
Schiff bases derived from L-tyrosine and their metal
complexes have wide application in biological science, like,
ML2 [H2O]2 where (M = Mn, Co, Ni and Cu) were synthe-
sized and were screened for their antifungal behavior
against Phytophthora capsici, the casual organism of foot
rot of black pepper [10]. A convenient method for the prep-
aration of transition metal complexes of L-tyrosine was
reported and this had enabled eight complexes of tyrosi-
nate anion (tyr) to be prepared: [M(tyr)2(H2O)n]
(M = Co, Ni, Cu, Zn; n = 1, 2, 3), [Cu(tyr)(NO3)], and
Li[Cu(tyr)3] [11,12]. In view of the literature, the coordina-
tion chemistry of tyrosine with heavy metals is obscure. In
the paper herein, we report the formation of 10 new amino
acid complexes obtained from the reaction of L-tyrosine
with the 10 metal ions in aqueous media.
2.2.2. [Sn(tyr)2(Cl)2] (II, C18H20N2O6SnCl2)
A similar procedure as that described for complex I
was carried out, but the weights of L-tyrosine (0.724 g,
4.0 mmol), LiOHÆH2O (0.168 g, 4.0 mmol) and SnCl4Æ
5H2O was 0.350 g and 1.0 mmol.
2.2.3. [Zn(tyr)2]Æ2H2O (III, C18H24N2O8Zn)
L-Tyrosine (0.543 g, 3.0 mmol) and LiOHÆH2O (0.126 g,
3.0 mmol) were dissolved in water (25 ml) and the solution
heated to 70 ꢁC for 20 min. The ZnBr2 salt (0.337 g,
1.5 mmol) was dissolved in a minimum quantity of water
and the solutions mixed with vigorous stirring (for a 1:2
metal:ligand ratio), the metal salt was added to the tyrH-
LiOHÆH2O solution. Precipitation was almost instanta-
neous, but stirring with heating were continued for
15 min. The Zn(II) complex was filtered, washed with
hot water (25 ml), and dried in vacuo over anhydrous
CaCl2.
The aim of this study is to make an assessment of the
coordination behavior of the resulting new complexes
formed.
2. Experimental
2.1. Materials
2.2.4. [Cd(tyr)2]Æ2H2O (IV, C18H24N2O8Cd)
A similar procedure as that described for complex III
was carried out the weight of CdCl2 was 0.302 g and
1.5 mmol.
L-Tyrosine (BDH), SnCl2, SnCl4, ZnBr2, CdCl2, HgCl2,
CrCl3Æ6H2O, FeCl3, La(NO3)3Æ6H2O, ZrOCl2Æ6H2O,
UO2(NO3)2Æ6H2O and LiOHÆH2O (Merck) were purchased
and used without further purification.
2.2.5. [Hg(tyr)2] (V, C18H20N2O6Hg)
A pale brown compound was prepared by the same
method as under compound III. The weight of HgCl2
was 0.407 g and 1.5 mmol.
2.2. Synthesis of metal complexes
First experiments were performed in order to find, if
possible, a general method for the preparation of L-tyrosine
complexes. Many amino acids will react with metal ions in
aqueous solutions, but reaction appeared to occur between
solutions of L-tyrosine and metal salts in water, at room
temperature or at 70 ꢁC.
It was found that lithium hydroxide powder was prefer-
able to sodium hydroxide or potassium hydroxide pellets,
as more accurate weight is possible with the powder.
A second approach was via the reaction of L-tyrosine
with lithium hydroxide in water at room temperature; sub-
sequent addition of aqueous metal salt solutions did not
appear to lead to complex formation. However, it was
found that by heating the tyrH-LiOHÆH2O solution to
70 ꢁC for 20 min, followed by addition of the metal salts,
complexes formed readily.
2.2.6. [Cr(tyr)3]Æ6H2O (VI, C27H42N3O15Cr)
L-Tyrosine (0.543 g, 3.0 mmol) and LiOHÆH2O (0.126 g,
3.0 mmol) were dissolved in water (25 ml) and the solution
heated to 70 ꢁC for 20 min. The CrCl3Æ6H2O salt (0.286 g,
1.0 mmol) was dissolved in a minimum quantity of water
and the solutions mixed with vigorous stirring (for a 1:3
metal:ligand ratio), the metal salt was added to the tyrH-
LiOHÆH2O solution. Precipitation was almost instanta-
neous, but stirring with heating were continued for
15 min. The Cr(III) complex was filtered, washed with
hot water (25 ml), and dried in vacuo over anhydrous
CaCl2.
2.2.7. [Fe(tyr)3] (VII, C27H30N3O9Fe)
Exactly like the above procedure of the Cr(III) complex
preparation but the weight of FeCl3 was 0.162 g and
1.0 mmol.
2.2.1. [Sn(tyr)2]ÆH2O (I, C18H22N2O7Sn)
L-Tyrosine (0.543 g, 3.0 mmol) and LiOHÆH2O (0.126 g,
3.0 mmol) were dissolved in water (25 ml) and the solution
heated to 70 ꢁC for 20 min. The SnCl2Æ2H2O salt (0.433 g,
1.5 mmol) was dissolved in a minimum quantity of water
and the solutions mixed with vigorous stirring (for a 1:2
2.2.8. [La(tyr)3]Æ7H2O (VIII, C27H44N3O16La)
Preparation of this compound followed essentially the
same procedure as preparation of VI, but the weight of
La(NO3)3Æ6H2O was 0.433 g and 1.0 mmol.

30
M.S. Refat et al. / Journal of Molecular Structure 881 (2008) 28–45
1
2.2.9. [ZrO(tyr)2]Æ2H2O (IX, C18H24N2O9Zr)
2.3.6. H NMR spectra
The structures of L-tyrosine, Sn(IV), Hg(II), Cr(III) and
ZrO(II) complexes were elucidated using a Varian Gemini
L-Tyrosine (0.543 g, 3.0 mmol) and LiOHÆH2O (0.126 g,
3.0 mmol) were dissolved in water (25 ml) and the solution
heated to 70 ꢁC for 20 min. The ZrOCl2Æ6H2O salt (0.429 g,
1.5 mmol) was dissolved in a minimum quantity of water
and the solutions mixed with vigorous stirring (for a 1:2
metal:ligand ratio), the metal salt was added to the tyrH-
LiOHÆH2O solution. Precipitation was almost instanta-
neous, but stirring with heating were continued for
15 min. The ZrO(II) complex was filtered, washed with
hot water (25 ml), and dried in vacuo over anhydrous
CaCl2.
1
200 MHz H NMR spectrometer. The L-tyrosine and the
above complexes were added into sample tubes and dis-
solved in DMSO-d6 and TMS as an internal reference.
1
The H NMR was done at 25 ꢁC.
2.3.7. Mass spectra
The purity of the Sn(II), Zn(II), Fe(III) and UO2(II)
complex were checked from mass spectra at 70 eV by using
AEI MS 30 Mass spectrometer.
2.2.10. [UO2(tyr)2] (X, C18H20N2O8U)
Exactly like the above procedure of the ZrO(II) complex
preparation but the weight of UO2(NO3)2Æ6H2O was
0.753 g and 1.5 mmol.
2.3.8. Thermal analysis (TG) and (DTG) techniques
Thermogravimetric analyses (TG) were carried out in
the temperature range from 25 to 800 ꢁC in a steam of
nitrogen atmosphere by Shimadzu TGA 50H thermal anal-
ysis. The experimental conditions were: platinum crucible,
nitrogen atmosphere with a 30 ml/min flow rate and a heat-
ing rate 10 ꢁC/min.
2.3. Apparatus and experimental conditions
2.3.1. Elemental analysis and metal percentage
Elemental analyses (C, H, and N) were performed using
a Perkin-Elmer CHN 2400 elemental analyzer. The per-
centages of the metal ions of the complexes were deter-
mined gravimetrically by converting the compounds into
their corresponding oxides.
2.3.9. Microbiological investigation
For these investigations the filter paper disc method was
applied. The investigated isolates of bacteria were seeded
in tubes with nutrient broth (NB). The seeded NB (1 cm3)
was homogenized in the tubes with 9 cm3 of melted (45 ꢁC)
nutrient agar (NA). The homogeneous suspensions were
poured into Petri dishes. The discs of filter paper (diameter
4 mm) were ranged on the cool medium. After cooling on
the formed solid medium, 2 · 10ꢀ5 dm3 of the investigated
compounds were applied using a micropipette. After incuba-
tion for 24 h in a thermostat at 25–27 ꢁC, the inhibition (ster-
ile) zone diameters (including disc) were measured and
expressed mm. An inhibition zone diameter over 7 mm indi-
cates that the tested compound is active against the bacteria
under investigation.
2.3.2. Molar conductance
Molar conductance measurements of the L-tyr ligand
and their complexes with 1.0 · 10ꢀ3 mol/l in DMSO were
carried out using Jenway 4010 conductivity meter.
2.3.3. Magnetic measurements
Magnetic measurements were carried out on a Sher-
wood Scientific magnetic balance in the micro analytical
laboratory using Gouy method.
Calibration: Two very good solid calibrants are
Hg[Co(CNS)4] and [Ni(en)3](S2O3). They are easily prepared
pure, do not decompose or absorb moisture and pack well.
Their susceptibilities at 20 ꢁC are 16.44 · 10ꢀ6 and
11.03 · 10ꢀ6 c.g.s. Units, decreasing by 0.05 · 10ꢀ6 and
0.04 · 10ꢀ6 per degree temperature raise, respectively, near
room temperature. The cobalt compound, besides having
the higher susceptibility, also packs rather densely and is
suitable for calibrating low fields, while the nickel compound
with lower susceptibility and density is suitable for higher
field [13]. Here we are used Hg[Co(CNS)4] only as calibrant.
The antibacterial activities of the investigated com-
pounds were tested against Escherichia coli, Bacillus subtil-
is, Serratia and Pseudomonas aeruginosa as well as some
kinds of fungi; Aspergillus flavus, Fusarium solani and Pen-
icillium verrucosum. The concentration of each solution was
1.0 · 10ꢀ3 mol dm3. Commercial DMSO was employed to
dissolve the tested samples.
3. Results and discussion
Ten, L-tyrosine complexes (Sn(II) and Sn(IV)), (Zn(II),
Cd(II) and Hg(II)), (Cr(III), Fe(III) and La(III)) and
(ZrO(II) and UO2(II)) rather L-tyrosine ligand have been
synthesized according to the following synthetic method:
For,
2.3.4. Infrared spectra
IR spectra (4000–400 cmꢀ1) were recorded as KBr pel-
lets on Bruker FT-IR Spectrophotometer.
2.3.5. Electronic spectra
(i) Sn(II) complex, (I)
The UV–vis, Spectra were obtained for the DMSO solu-
tion (1.0 · 10ꢀ3 M) of the L-tyr and their 10 complexes with
a Jenway 6405 Spectrophotometer using 1 cm quartz cell,
in the range 200–550 nm.
aqueous media
SnCl þ 2½tyrH-LiOH ꢁ H Oꢂ
½SnðtyrÞ ꢂ ꢁ H O
ꢀꢀꢀꢀꢀꢀ!
2
2
2
2
(ii) Sn(IV) complex, (II)

M.S. Refat et al. / Journal of Molecular Structure 881 (2008) 28–45
31
aqueous media
3.2. Molar conductivities of metal chelates
SnCl þ 4½tyrH-LiOH ꢁ H Oꢂ
(iii) Zn(II) complex, (III)
½SnðtyrÞ Cl ꢂ
ꢀꢀꢀꢀꢀꢀ!
4
2
2
2
Conductivity measurements in non-aqueous solutions
have frequently been used in structural studies of metal
chelates within the limits of their solubility. They provide
a method of testing the degree of ionization of the com-
plexes, the molar ions that a complex liberates in solution,
the higher will be its molar conductivity and vice versa. The
non-ionized complexes have negligible value of molar con-
ductance. The molar conductivities of the solid chelates are
measured for 1.0 · 10ꢀ3 mol solution of 1:2 and 1:3 com-
plexes in DMSO. The conductivity data reported for these
complexes are given in Table 1. It is clear from the conduc-
tivity data that the complexes present behave as non-elec-
trolytes [14] behavior. The molar conductivity values for
all the complexes in organic solvent (DMSO) with
10ꢀ3 mol were in rang of (11.7–19.2) Xꢀ1 cmꢀ1 molꢀ1
(Table 1).
aqueous media
ZnBr þ 2½tyrH-LiOH ꢁ H Oꢂ
½ZnðtyrÞ ꢂ ꢁ 2H O
ꢀꢀꢀꢀꢀꢀ!
2
2
2
2
(iv) Cd(II) complex, (IV)
aqueous media
CdCl þ 2½tyrH-LiOH ꢁ H Oꢂ
½CdðtyrÞ ꢂ ꢁ 2H O
ꢀꢀꢀꢀꢀꢀ!
2
2
2
2
(v) Hg(II) complex, (V)
HgCl þ 2½tyrH-LiOH ꢁ H O aqueous media½HgðtyrÞ ꢂ
ꢀꢀꢀꢀꢀꢀ!
2
2
2
(vi) Cr(III) complex, (VI)
aqueous media
CrCl þ 3½tyrH-LiOH ꢁ H Oꢂ
½CrðtyrÞ ꢂ ꢁ 6H O
ꢀꢀꢀꢀꢀꢀ!
3
2
2
3
(vii) Fe(III) complex, (VII)
aqueous media
FeCl þ 3½tyrH-LiOH ꢁ H Oꢂ
½FeðtyrÞ ꢂ
ꢀꢀꢀꢀꢀꢀ!
3
2
2
(viii) La(III) complex, (VIII)
3.3. Magnetic measurements
aqueous media
LaðNO Þ þ 3½tyrH-LiOH ꢁ H Oꢂ
ꢁ 7H2O
½LaðtyrÞ ꢂ
ꢀꢀꢀꢀꢀꢀ!
3
2
2
3
Magnetic measurements were carried out on a Sher-
wood Scientific magnetic balance according to the Gauy
method.
(ix) ZrO(II) complex, (IX)
The magnetic moments of the Cr(III) and Fe(III) com-
plexes at T = 300 K and their corresponding hybrid orbi-
tals are given in Table 2. From the data given in Table 2,
the observed values of the effective magnetic moments leff
measured for the [Cr(tyr)3]Æ6H2O and [Fe(tyr)3] complexes
equal to 3.13 and 2.18 B.M., respectively, this is in conve-
nient with experimental values of 3.77 and 2.25 B.M. [13]
obtained for high spin octahedral Cr(III) complex and
low spin octahedral Fe(III) complex, with hyperdization
of d2sp3 for both complexes.
aqueous media
ZrOCl þ 2½tyrH-LiOH ꢁ H Oꢂ
½ZrOðtyrÞ ꢁ 2H O
ꢀꢀꢀꢀꢀꢀ!
2
2
2
2
(x) UO2(II) complex, (X)
aqueous media
UO Cl þ 2½tyrH-LiOH ꢁ H Oꢂ
½UO ðtyrÞ ꢂ
ꢀꢀꢀꢀꢀꢀ!
2
2
2
2
2
The L-tyrosine complexes were investigated in this study,
are very stable at room temperature in the solid state.
These complexes; Sn(II), Sn(IV), Zn(II), Cd(II), Hg(II),
Cr(III), Fe(III), La(III), ZrO(II) and UO2(II) are insoluble
in common organic solvents in cold or hot conditions
except DMSO (dimethylsulphoxide).
3.4. Infrared spectra
The IR spectra in the (4000–400 cmꢀ1) region have pro-
vided information regarding the coordination mode in the
L-tyrosine complexes and were analyzed by comparison
with data for the free L-tyrosine ligand. The most relevant
bands and proposed assignments for all the complexes are
mentioned in Table 3. In the FT-IR spectra, extensive cou-
pling occurs for several vibrations, making qualitative
deductions about the environment around metal ions diffi-
cult. However, the IR spectral data (Table 3) shown
changes in the position and profiles of some bands, as com-
pared to those of free L-tyrosine (amino acid), suggesting
participation of the groups that produce these bounds in
the coordination with metal ions Sn(II), Sn(IV), Zn(II),
Cd(II), Hg(II), Cr(III), Fe(III), La(III), ZrO(II) and
UO2(II). Major changes are related to the carboxylate
and amine bands.
No suitable crystals of the complexes were obtained in
order to perform an X-ray structure determination. The
physical properties: colors, melting and/or decomposition
points, elemental analyses and molar conductance of the
free ligand and its complexes are given in Table 1. The ana-
lytical data are in a good agreement with the proposed stoi-
chiometry of the complexes.
The metal-to-ligand ratio in Sn(II), Sn(IV), Zn(II),
Cd(II), Hg(II), ZrO(II) and UO2(II) complexes were the
same molar ratio, that found to be 1:2 (metal:ligand) but
these are different in the coordination behaviors. On the
other hand, the Cr(III), Fe(III) and La(III) tyrosine com-
plexes have been coordinated to (1:3) molar ratio.
3.1. Elemental analysis data
The elemental analysis measurements of the carbon,
nitrogen, hydrogen, and the percentage of metal ions for
the synthesized complexes are illustrated in Table 1.
(i) Ligand (L-tyr); amino acid physical properties indi-
cate a ‘‘salt-like’’ behavior. Amino acids are crystal-
line solids with relatively high melting points, and

32
M.S. Refat et al. / Journal of Molecular Structure 881 (2008) 28–45
Table 1
Elemental analyses and physical data of the tyrosine complexes
Compounds
Mwt.
Mp (ꢁC) or decomp.
Color
Content ((calculated) found)
Km (Xꢀ1 cmꢀ1 molꢀ1
)
% C
% H
% N
%M
–
L-Tyrosine
(C9H11NO3)
181.19
496.69
549.69
461.38
508.4
344 dec.
275 dec.
280
White
White
White
59.66
6.12
7.73
11.7
(59.60)
(6.07)
(7.59)
[Sn(tyr)2]ÆH2O
(I, C18H22N2O7Sn)
43.38
(43.49)
4.41
(4.43)
5.33
(5.64)
23.73
(23.92)
14.02
19.2
[Sn(tyr)2(Cl)2]
(II, C18H20N2O6SnCl2)
38.98
(39.29)
3.57
(3.64)
5.07
(5.09)
21.40
(21.59)
[Zn(tyr)2]Æ2H2O
(III, C18H24N2O8Zn)
290 dec.
235
Pale
Yellow
46.77
(46.82)
5.13
(5.20)
5.68
(6.07)
13.93
(14.17)
11.98
13.07
11.78
13.84
12.41
18.70
16.14
13.62
[Cd(tyr)2]Æ2H2O
(IV, C18H24N2O8Cd)
Pall
Brown
42.31
(42.49)
4.67
(4.72)
4.85
(5.51)
22.07
(22.11)
[Hg(tyr)2]
(V, C18H20N2O6Hg)
560.59
699.99
595.84
804.91
503.22
630.03
320 dec.
275 dec.
270
Pall
Brown
38.53
(38.20)
3.56
(3.57)
4.99
(5.12)
(35.78)
(35.18)
[Cr(tyr)3].6H2O
(VI, C27H42N3O15Cr)
Green
45.89
(46.28)
5.91
(6.00)
5.71
(6.00)
7.39
(7.43)
[Fe(tyr)3]
(VII, C27H30N3O9Fe)
Brown
54.31
(54.38)
4.99
(5.03)
6.81
(7.05)
9.28
(9.37)
[La(tyr)3]Æ7H2O
(VIII, C27H44N3O16La)
270 dec.
240 dec.
270
Pall
Brown
39.87
(40.25)
(5.93)
(5.47)
4.72
(5.22)
17.18
(17.26)
[ZrO(tyr)2]Æ2H2O
(IX, C18H24N2O9Zr)
White
(42.98)
(42.52)
4.29
(4.74)
5.43
(5.33)
18.13
(18.23)
[UO2(tyr)2]
Yellow
34.19
3.09
4.37
37.70
(X, C18H20N2O9U)
(34.28)
(3.17)
(4.44)
(37.78)
almost are quite soluble in water and insoluble in
non-polar solvents. In solution, the amino acid mole-
cule appears to have a change which changes with
pH. As intermolecular neutralization reaction leads
to a salt-like ion called a Zwitterion. The accepted
practice is to show the amino acids in the Zwitterion
from (Scheme 1); (i) the amino group can lose a
Table 2
The magnetic moment of the Cr(III) and Fe(III) complexes
Complex
leff B.M.
(found)
leff B.M.
(calcd.)
Hybrid
orbitals
Stereo-
chemistry
[Cr(tyr)3]Æ6H2O 3.13
[Fe(tyr)3]
3.77
2.25
d2sp3
d2sp3
Octahedral
Octahedral
2.18
Table 3
Important FT-IR bands of the L-tyrosine and its metal complexes
Assignments (cmꢀ1
)
Compound
L-Tyr
–
I
II
III
IV
V
VI
VII
VIII
IX
X
NH2 asym. str.
NH2 sym. str.
3375
3390
3364
3307
3270
3178
3382
3262
3322
3273
3420
3422
3378
3399
3423
NH3 str.
3124
3205
1612
1588
1416
1364
1243
–
3206
3206
3204
3120
1578
3206
3206
3205
3206
3207
OH str.
COOꢀ asym.
dNH2
1610
1588
1416
1364
1245
1042
1610
1587
1416
1364
1245
1042
1615
1544
1399
1610
1588
1407
1369
1243
1044
1610
1589
1416
1365
1246
1041
1610
1589
1416
1364
1246
1042
1611
1588
1415
1364
1244
1042
1611
1588
1416
1364
1244
1042
1609
1589
1416
1364
1247
1042
COOꢀ sym.
dCH; CH2
OH in plane def.
NH2 wagging
1424
1367
1252
1069
1043
679
1234
–
OH out of plane def.
NH2 rocking
648
–
649
575
649
575
658
543
649
574
648
574
649
575
649
575
650
576
650
575
595
569
M-N str.
–
432
432
420
432
420
418
432
432
433
434

M.S. Refat et al. / Journal of Molecular Structure 881 (2008) 28–45
33
hydrogen ion to become negative charged, (ii) the
amino group can accept a hydrogen ion to become
positive charged.
tions of the benzene ring and the d(NH2) vibrations to
some extent. The m(COOꢀ) antisymmetric stretching are
observed at the same frequencies and symmetric stretching
vibrations are at the same region frequencies (with varying
in the intensity of bands) than those of the ligand in the
Zwitterion feature.
The OH in plane and out of plane deformation vibra-
tions has no detected frequencies. The vibrations of the
phenolic group, the skeletal deformation vibrations occur
at the same regions as in the ligand.
(ii) Assignment of observed frequencies; in all spectra,
the characteristic band of NH2 group vibration
appears at ꢃ3300 and ꢃ3400 cmꢀ1 corresponding to
ms(NH2) and mas(NH2), respectively. In the spectra
of complex compounds, this band overlap with the
well defined very intense due to the hydrogen bond
þ
of crystalline water.The band due to the NH3 group
mðNH3þÞ at ꢃ3124, 2950 and 2500 cmꢀ1 [15], which
are very intense in the free ligand, appears as a weak
shoulder or disappear in the spectra of the complex
compounds.The sharp band at around 3200 cmꢀ1 is
assigned to the OH stretching vibration; the broad
From 500 to 400 cmꢀ1, absorption bands which cannot be
observed in the ligand or appear with shifted in frequencies
or the intensities were defected dependently on the complex-
ation. The absorption bands appear at 432 cmꢀ1 for Sn(II),
432 cmꢀ1 for Sn(IV), 420 cmꢀ1 for Zn(II), 432 cmꢀ1 for
Cd(II), 420 cmꢀ1 for Hg(II), 418 cmꢀ1 for Cr(III),
432 cmꢀ1 for Fe(III), 432 cmꢀ1 for La(III), 433 cmꢀ1 for
ZrO(II) and 434 cmꢀ1 for UO2(II) complexes, respectively.
They are assigned to the metal-nitrogen stretching vibration
by comparison of the chelate spectra with the ligand spec-
trum and referring to the metal chelate amino acids [18–21].
For the L-tyrosine adducts, the observed mas(COOꢀ)
band was exhibits at ꢃ1610 cmꢀ1 as well as the ms(COOꢀ)
band which appears at ꢃ1400 cmꢀ1, are in agreement with
coordination involving the amine nitrogen, as well as an
oxygen atom of the carboxylate group [22,23]. The Dm dif-
ference (asymmetric–symmetric) is ranged from 193 to
216 cmꢀ1,, this value proved that, metal ions coordinated
to carboxylate group of L-tyrosine ligand as a monodentate
chelates [15].
bands from 3100 to 2800 cmꢀ1 are due to NH3
þ
and CH stretching vibrations of the benzene ring.
The CH stretching vibrations of an aliphatic group
are observed in a lower frequency region than those
of a benzene ring.
(iii) Metal-chelates; in all of the complexes it is appar-
ent that the tyrosine moiety complexes as the tyro-
sinate anion [9,11,16,17]. Tyrosine can lose
a
proton in two ways: from the carboxylic acid group
or from the phenolic group. It is to be expected
that carboxylic acid group will deprotonated prefer-
entially, especially the a-amino acid moiety acts as
a chelate. In the present study no specific attempt
was made to deprotonate the phenolic (hydrogen)
and there is no evidence to suggest that it occurred
in advertently.
The m(U@O) vibration in the uranyl complex is observed
as expected as a medium strong at 930 cmꢀ1 is a good
agreement with those known for many dioxouranium
(VI) complexes [24,25]. On the other hand, concerning,
the infrared spectra of [ZrO]2+ complex show a medium
strong absorption band at 1040 account that m(Zr@O) as
expected [26].
As the bands above 3500 cmꢀ1 of the Sn(II), Zn(II),
Cd(II), Cr(III), La(III) and ZrO(II) chelates disappear in
the IR spectra, are obtained often TGA analysis, these
bands are assigned to the OH stretching vibrations in the
water of crystallization.
Although the bands from 3400 to 3100 cmꢀ1 are due to
NH2 symmetric and asymmetric and OH stretching vibra-
tions are observed at the same region as in the ligand.
In the region 1700–500 cmꢀ1 the assignments of the
observed bands is accomplished by a comparison of the
spectrum of each chelate with that of the L-tyrosine free
ligand. For the metal chelates,þthe NH2 deformation vibra-
tions appear in stead of NH3 deformation vibrations of
the ligand. The m(COOꢀ) antisymmetric stretching vibra-
Account that tyrosine acts as a bidentate ligand, data
about the complex compounds formation were obtained
mainly by compaþring the absorption bands due to the
vibrations of NH3 and COOꢀ groups.
3.5. Electronic spectra
The bands in the range 200–450 nm can be assigned to
n–p* and/or p–p* intraligand transition associated to
H
C
R
O
C
O
H
-
+
H
C
(acid)
(amine) H2N
OH
H
N
C
O
H
R
H2
Zwitterion
C
OH
R=
Scheme 1. Zwitterion structure of L-tyrosine.

34
M.S. Refat et al. / Journal of Molecular Structure 881 (2008) 28–45
amino acid (L-tyrosine). Free ligand and complexes exhibit
similar spectra in UV region in relation to the number of
the absorption peaks.
The electronic spectra of L-tyrosine and its complexes
were recorded in DMSO and listed in Table 4.
The electronic absorption spectrum of the free ligand
shows three absorption peaks appearing at kmax = 230,
240 and 280 nm. The first two bands are attributed to the
intraligand p–p* transition [27], and the third can be attrib-
uted to the intraligand n–p* charge transfers [28–30]. The
electronic absorption spectra of the complexes are different
from the spectrum of the free ligand, where there are forth
bands appearing in the spectrum of Sn(II) complex. The
first two band appeared at 220, 235 nm, which represent
the intraligand p–p* transition. The second two bands
appeared at 245, 280 nm, which can be assigned to the
intraligand n–p* charge transfers. But in the spectra of
Sn(IV) complex there are three bands only, the first two,
which are appeared at 235, 250 nm represented the intrali-
gand p–p* transition, and the third, which at 275 nm, can
be interpretated to the intraligand n–p* charge transfers.
The electronic absorption spectra of Zn(II) complex
show four bands. The first two band appeared at 220,
235 nm, which represent the intraligand p–p* transition.
The third band appeared at 280 nm, which can be attrib-
uted to the intraligand n–p* charge transfers. The forth
band, which is abroad band, appeared at range 325 nm,
can be assigned to L fi Zn(II) charge transfers. But in
the spectra of Cd(II) and Hg(II) complex there are three
bands only the first two represent the intraligand p–p*
transition, and the third can be attributed to the intraligand
n–p* charge transfers.
There are three bands appearing in the spectrum of
Cr(III) complex. The first band appeared at 220 nm, which
represents the intraligand p–p* transition. The second band
appeared at 275 nm, which can be attributed to the intral-
igand n–p* charge transfers. The third band, which is
abroad band, appeared at range 435 nm, can be assigned
to L fi Cr(III) charge transfers. In the spectra of Fe(III)
complex there are three bands, the first two represent the
intraligand p–p* transition, and the third can be attributed
to the intraligand n–p* charge transfers. The spectra of
La(III) complex show four bands, the first two represent
the intraligand p–p* transition, and the second two can
be attributed to the intraligand n–p* charge transfers.
The electronic spectrum of ZrO(II) complex is resample
to the spectrum of Cr(III) complex but the two bands
appeared at 245 and 285 nm.
There are five bands appearing in the spectrum of
UO2(II) complex. The first two band appeared at 225,
235 nm, which represented the intraligand p–p* transition.
The second two bands appeared at 245 and 280 nm, can be
attributed to the intraligand n–p* charge transfers. The fifth
band, which is abroad band, appeared at range 400 nm,
can be assigned to L fi UO2(II) charge transfers.
Table 4
The electronic spectral date of the free ligand and its complexes
Compound
L-Tyr
kmax (nm)
e (molꢀ1 cmꢀ1
)
Assignment
230
240
280
471
199
1189
p–p* trans.
p–p* trans.
n–p* trans.
[Sn(tyr)2]ÆH2O
220
235
245
280
265
155
370
p–p* trans.
p–p* trans.
n–p* trans.
n–p* trans.
1947
[Sn(tyr)2(Cl)2]
235
250
275
211
3000
3000
p–p* trans.
p–p* trans.
n–p* trans.
[Zn(tyr)2]Æ2H2O
220
235
280
325
270
1224
2943
500
p–p* trans.
p–p* trans.
n–p* trans.
L fi Zn C.T.
[Cd(tyr)2]Æ2H2O
[Hg(tyr)2]
225
245
285
3000
3000
2919
p–p* trans.
p–p* trans.
n–p* trans.
220
240
280
1134
284
3000
p–p* trans.
p–p* trans.
n–p* trans.
1
3.6. H NMR spectra
[Cr(tyr)3]Æ6H2O
[Fe(tyr)3]
220
275
435
330
1510
190
p–p* trans.
n–p* trans.
L fi Cr C.T.
The proton magnetic resonance spectra of the Sn(IV),
Hg(II), Cr(III) and UO2(II) complexes were analyzed in
comparison of the spectra of the free ligand (Fig. 1). The
ligand structure is shown in Scheme 2. The chemical shift
(d, ppm) of the different protons have been recorded in
Table 5.
It is clear that all H protons (b–H, c–H, d–H and e–H)
experience downfield shift in the L-tyrosine complex, except
a–H has an up field shift, these data compared with free L-
tyrosine ligand. Theoretically, the possible complex site
were –NH2, –OH and –COOH, but the chance of complex
site of –OH with Sn(IV), Hg(II), Cr(III) and ZrO(II) ele-
ments is slim, only if the PH was very high in the system.
In experimental section, the pH value was adjust at pH 7
(neutral).
245
270
285
673
2499
2552
p–p* trans.
n–p* trans.
n–p* trans.
[La(tyr)3]Æ7H2O
225
245
270
285
192
246
2874
3000
p–p* trans.
p–p* trans.
n–p* trans.
n–p* trans.
[ZrO(tyr)2]Æ2H2O
245
285
282
2628
p–p* trans.
n–p* trans.
[UO2(tyr)2]
225
235
245
280
400
382
946
205
2427
300
p–p* trans.
p–p* trans.
n–p* trans.
n–p* trans.
L fi UO2 C.T.

M.S. Refat et al. / Journal of Molecular Structure 881 (2008) 28–45
35
a
H
c
H
e
d
f
HO
C
C
COOH
H
NH2
d
e
b
Scheme 2. Structure formula of L-tyrosine.
Table 5
The 1H NMR spectral dataa (d, ppm)b of the ligand and its corresponding
Sn(IV), Hg(II), Cr(III) and ZrO(II) complexes
Compound
a–H
b–H
c–H
d–H
e–H
f–Hc
L-Tyrosine
[Sn(tyr)2(Cl)2]
[Hg(tyr)2]
[Cr(tyr)3]Æ6H2O
[UO2(tyr)2]
a
2.61
2.50
2.52
2.58
2.49
2.72
–
3.06
–
3.33
3.39
3.41
3.50
6.50
6.68
6.71
6.77
6.71
6.85
7.04
7.09
7.07
7.11
9.83
10.80
9.32
9.50
9.35
2.93
3.26 4.20
Solvent DMSO-d6.
b
c
Relative to TMS.
The phenolic proton resonances not shifted indicating that (OH) group
does not participate in bonding.
tyrosine where proton of phenolic group is not released.
A comparison of metal–ligand stability constants values
of tyrosine with those of serine permits the conclusion that
the unionized hydroxyl group is not participating in the
complex formation [31,32]. The coordination appears to
be only through amino nitrogen and carboxylate oxygen.
The brood signal exhibited by the ligand due to the OH
(carboxylate group) proton at 12.34 ppm disappears in the
tyrosine complexes indicating the coordination of oxygen
atom (carboxylate ion) with the metal ion [33,34]. The
appearance of signals due to (phenolic) protons of the same
positions in the free ligand and in its complexes shows the
non-involvement of this group in coordination.
Another fact is that the vibration of chemical shift of c–
H is larger than a–H and b–H, indicating one of the com-
plex sites was near to c–H, that is –NH2.
3.7. Mass spectra
The electron impact mass spectrum of the free ligand (L-
tyrosine) Fig. 2, confirm the proposed formula by showing
a peak at m/z = 181 amu corresponding to L-tyrosine moi-
ety [(C9H11NO3) atomic mass 181.19]. It also shows a series
of peaks i.e. m/z (%)=136 (3.6), 107 (100), 76 (7.6) and 38
(2.4), corresponding to various fragments. This intensity
gives an idea of stability of fragment. The fragmentation
patterns of L-tyrosine are shown in Scheme 3.
The mass spectra of Sn(II), Zn(II), Fe(III) and UO2(II)
tyrosine are presented in Fig. 2. All of these complexes
have two main molecular ion peaks, one of them concern-
ing the molecular ion peak of tyrosine ion m/z = 180 amu
(ligand) and the other important peak at m/z = 118, 65,
56 and 238 amu corresponding to the release of metal ions
Sn(II), Zn(II), Fe(III) and UO2(II), respectively.
Fig. 1. The 1H NMR spectra of L-tyrosine and its complexes.
Most amino acids are present as a single protonated
from HL in the pH range 2.7–8.5. A few amino acids occur
as H2L, H2L+ from over the whole range. This is true for

36
M.S. Refat et al. / Journal of Molecular Structure 881 (2008) 28–45
Fig. 2. The mass spectra L-tyrosine and its complexes.
O
H
C
H2N
CH
H2N
C
OH
CH2
CH2
CH2
- COOH
- 45
- CH3N
- 29
OH
OH
OH
C8H10NO
m/z (%)= 136 (3.60)
C9H11NO3
m/z (%)= 181 (3.00)
C7H7O
m/z (%)= 107 (100.00)
base peak
- CH3O
- 31
- C3H2
- 38
C3H2
m/z (%)= 38 (2.40)
C6H4
m/z (%)= 76 (7.60)
Scheme 3. Fragmentation scheme of L-tyrosine.

M.S. Refat et al. / Journal of Molecular Structure 881 (2008) 28–45
37
Both the L-tyrosinate complexes resulted herein and the
L-tyrosine ligand show the base peaks at m/z 107, which
due to the fragment, C7H7O. The data confirm the coordi-
nation mode of the metal tyrosinate complexes, this fact is
greatly supported that, L-tyrosine act as bidentate ligand
with coordination involving the carboxylic oxygen and
the nitrogen atom of the amino group.
From the mass spectra (Fig. 2); the Sn(II)-tyrosinate
complex possesses a series of peaks, i.e. m/z = 180, 135,
118, 106 and 77 amu corresponding to the release of
C9H10NO3, C8H9NO, Sn(II), C7H6O and C6H5; the
Zn(II)-tyrosinate complex show the main fragment peaks
at m/z = 180, 135, 106, 76 and 65 amu, which due to the
fragments of C9H10NO3, C8H9NO, C7H6O, C6H5 and
Zn(II), respectively; the important fragments peaks of
Fe(III)-tyrosinate complex at m/z = 180, 135, 106, 76 and
56 amu corresponding to the release of C9H10NO3,
C8H9NO, C7H6O, C6H5 and Fe(III), respectively; concern-
ing, UO2(II)-tyrosinate complex, the fragment patterns are
observed at 238, 180, 135, 106 and 76 amu, which are due
to the fragments: UO2(II), C9H10NO3, C8H9NO, C7H6O
and C6H5, respectively.
From the two previously Schemes 4 and 5, can be con-
cluded that:
(i) The present of the important fragment peak at m/
z = 135 amu in all of our studied tyrosine complexes,
proved that, the L-tyrosine ligand involved in the
complexation as a tyrosinate feature.
(ii) The molecular ion peak, C7H6O m/z = 106 amu,
which is exist in the tyrosinate complexes gives an
interpretation about the non-participation of the phe-
nolic group in the chelation between metal ions and
L-tyrosine.
(iii) From the mass spectra (TLC) in the four fragment
diagrams of Sn(II), Zn(II), Fe(III) and UO2(II), it is
clearly obvious that all of our studied tyrosinate com-
plexes are pure and all of them have one peak.
O
H2
N
H2
C
H
C
C
O
OH
M
H2
C
HO
C
H
N
O
C
O
H2
M= Sn(II), Zn(II) and UO2(II)
m/z 118
m/z 65
- M
M
m/z 238
H2
C
H
C
H2
C
- CO2
H
C
H2N
OH
H2N
O
OH
- 44
C
O
C8H10NO
m/z= 135
C9H10NO3
m/z= 180
- CH3N
- 29
- CH3O
H2C
OH
- 31
C7H7O
m/z = 106
C6H4
m/z = 76
Scheme 4. Fragmentation scheme of Sn(II), Zn(II) and UO2(II) tyrosinate complexes.

38
M.S. Refat et al. / Journal of Molecular Structure 881 (2008) 28–45
HO
OH
O
H2C
C
HC
CH2
HC
O
H2N
C
O
O
O
H2C
Fe
Fe
N
O
C
NH2
H2
CH
- Fe
HO
m/z 65
H2
C
H
C
H2
C
H
C
- CO2
- 44
H2N
OH
H2N
O
OH
C
O
C8H10NO
m/z= 135
C9H10NO3
m/z= 180
- CH3N
- 29
- CH3O
- 31
H2C
OH
C7H7O
C6H4
m/z = 106
m/z = 76
Scheme 5. Fragmentation scheme of Fe(III) tyrosinate complex.
3.8. Thermal analysis
[Cr(tyr)3]Æ6H2O, [Fe(tyr)3], [La(tyr)3]Æ7H2O, [ZrO(tyr)2]-
Æ2H2O and [UO2(tyr)2] compounds at the heating rate of
10 ꢁC/min in the static nitrogen atmosphere were done.
The overall loss of mass from the TG curves is 67.08%
for L-tyr, 63.37 for [Sn(tyr)2]ÆH2O, 79.20% for [Sn(tyr)2Cl2],
72.66% for [Zn(tyr)2]Æ2H2O, 74.70% for [Cd(tyr)2]Æ2H2O,
53.27% for [Hg(tyr)2], 53.41% for [Cr(tyr)3].6H2O, 78.58%
for [Fe(tyr)3], 61.53% for [La(tyr)3]Æ7H2O, 74.04% for
[ZrO(tyr)2]Æ2H2O and 63.57% for [UO2(tyr)2] compounds,
respectively. All the complexes have two, three or four
maxima peaks mass loss. The analysis of thermal curves
of the complexes clearly indicates that the weight loss (first
maximum peak) between 20 and 200 ꢁC (except to
[La(tyr)3]Æ7H2O from 20 to 300 ꢁC) corresponds to water
Thermal techniques, such as thermogravimetric analysis
(TGA and DTG), has been successfully employed for the
study of the energetic of interactions of metal cations with
biological species, such as amino acids [34,35]. The weight
loss profiles are analyzed the amount or percent of weight
loss at any given temperature, and the temperature ranges
of the degradation process were determined [36].
Thermal stability domains, melting points, decomposi-
tion phenomena and their assignments for the L-tyrosinate
complexes are summarized in Table 6. The simultaneous
TG-DTG measurements of: L-tyr, [Sn(tyr)2]ÆH2O,
[Sn(tyr)2Cl2], [Zn(tyr)2]Æ2H2O, [Cd(tyr)2]Æ2H2O, [Hg(tyr)2],

M.S. Refat et al. / Journal of Molecular Structure 881 (2008) 28–45
39
Table 6
Thermal data of L-tyrosine and its complexes
Compound
Steps
Temperature range (ꢁC)
DTG peak (ꢁC)
TG Weight loss (%)
Assignments
Endo
323
Exo
Calc.
Found
L-Tyr
1st
25–800
–
66.89
33.11
67.08
32.92
–C4H11NO3 (organic moiety)
5C (residue)
[Sn(tyr)2]ÆH2O
1st
2nd
25–200
200–800
83
280
–
–
3.62
59.59
36.78
3.31
60.06
36.63
One mole of crystal water
C14H20N2O5 (organic moiety)
SnO + 4C (residue)
[Sn(tyr)2Cl2]
1st
2nd
25–300
300–800
276
600
–
–
38.93
39.48
21.59
38.45
40.75
20.80
C14H14O2 (two, p-hydroxy phenyl)
C4H6N2O4Cl2(organic moiety)
Sn (residue)
[Zn(tyr)2]Æ2H2O
1st
2nd
3rd
25–200
200–500
500–800
63
292
558
–
–
–
7.80
23.19
40.96
28.05
7.69
23.82
41.15
27.34
2 H2O crystal water
C7H7O (one, p-hydroxy phenyl)
C7H13N2O4 (organic moiety)
ZnO + 4C (residue)
[Cd(tyr)2]Æ2H2O
1st
25–220
220–250
250–350
350–800
217
238
301
521
–
–
–
–
7.08
21.05
21.05
25.57
25.25
6.88
20.64
20.64
26.54
25.30
2 H2O crystal water
2nd
3rd
4th
C7H7O (one, p-hydroxy phenyl)
C7H7O (one, p-hydroxy phenyl)
C4H6N2O3 (organic moiety)
CdO (residue)
[Hg(tyr)2]
1st
2nd
3rd
25–390
390–640
640–800
327
577
670
–
–
–
19.08
19.08
14.63
47.21
18.88
18.88
15.51
46.73
C7H7O (one, p-hydroxy phenyl)
C7H7O (one, p-hydroxy phenyl)
H6N2O3
HgO + 4C (residue)
[Cr(tyr)3]Æ6H2O
1st
2nd
3rd
25–200
200–340
340–800
101
276
506
–
–
–
15.44
15.29
24.14
45.13
16.32
14.84
22.25
46.59
6 H2O crystal water
C7H7O (one, p-hydroxy phenyl)
H23N3O6.5 (organic moiety)
1/2Cr2O3 + 20C (residue)
[Fe(tyr)3]
1st
2nd
25–500
500–800
264
664
–
–
53.85
24.68
21.47
53.71
24.87
21.42
C21H21O3 (three, p-hydroxy phenyl)
C2H9N3O4.5 (organic moiety)
1/2Fe2O3 + 4C (residue)
[La(tyr)3]Æ7H2O
[ZrO(tyr)2]Æ2H2O
[UO2(tyr)2]
1st
2nd
25–300
300–800
275
475
–
15.64
46.25
38.11
15.58
45.95
38.47
7 H2O
C15H30N3O7.5 (organic moiety)
1/2La2O3 + 12C (residue)
1st
2nd
25–200
200–800
117
306
–
–
7.15
68.37
24.48
6.53
67.51
25.96
2 H2O
C18H20N2O5 (organic moiety)
ZrO2 (residue)
1st
2nd
3rd
25–120
120–300
300–800
95
259
–
–
–
660
–
–
Melting point
33.95
28.29
37.76
33.70
29.87
36.43
C14H14O2 (two, p-hydroxy phenyl)
C4H6N2O6 (organic moiety)
Uranium metal (residue)
molecules for the hydrated complexes like, (Sn(II), Zn(II),
Cd(II), Cr(III), La(III) and ZrO(II)). Because of the low
temperatures, these water molecules may be considered as
crystal water [37]. While the first (in case of non-hydrated
complexes), second and third mass loss is due to the loss
of one, two or three molecule of organic radicals
(C7H7O-p-hydroxyphenyl) from contents of L-tyr ligand.
The other decomposition peak was interpreted to the
decomposition of the L-tyrosine rest. The end-products
were confirmed with infrared spectra.
dation peak was observed at 323 ꢁC in the TG profile.
From the TG profile of the L-tyr, it appears that the sample
decomposes in one sharp stage over the wide temperature
range 25–800 ꢁC. The decomposition occurs with a mass
loss of 67.08% and its calculated value is 66.89%.
3.8.2. [Sn(tyr)2]ÆH2 O and [Sn(tyr)2Cl2]
Thermal analysis curves of the tin(II) and tin(IV) com-
plexes show that decomposition takes places in two stages
in temperature range 25–800 ꢁC (DTGmax: 83 and 280 ꢁC)
for [Sn(tyr)2]ÆH2O complex and in between 25 and 800 ꢁC
(DTGmax: 276 and 600 ꢁC) for [Sn(tyr)2Cl2] complex. The
two endothermic decomposition stages correspond to
decomposition of the ligand. The TG curves of the two
3.8.1. L-Tyrosine (ligand)
The 4-hydroxyphenylalanine (L-tyr) ligand melts at
343 ꢁC with simultaneous decomposition. The main degra-

40
M.S. Refat et al. / Journal of Molecular Structure 881 (2008) 28–45
complexes show a weight losses (found 63.37, calcd.
63.16% for Sn(II) complex and found 79.20, calcd.
78.41% for Sn(IV) complex) corresponding to the loss of
(one crystal water molecule and organic moiety,
C14H20N2O5) and (two p-hydroxyphenyl molecules,
C14H14O2 and organic moiety, C4H6N2O4Cl2) for
[Sn(tyr)2]ÆH2O and [Sn(tyr)2Cl2] complexes, respectively.
The final products, formed at 800 ꢁC, consist of
(SnO + 4C) and (Sn metal) for Sn(II) and Sn(IV) com-
plexes, respectively. Reported data on thermal analysis
studies were collected in nitrogen atmosphere media which,
indicate that the two tin complexes decompose to give
tin(II) oxide or tin metal (according to metal cations) and
few carbon atoms as final products, interpretive for no suf-
ficiently of oxygen atoms encouraged the liberated carbon
as carbon monoxide or dioxide.
product is Cr2O3 (Fig. 3). The overall weight loss (found
53.41%, calcd. 54.87%) agrees well with the proposed struc-
ture. The Fe(III) and La(III)-tyrosinate complexes show a
weight losses (found 78.58, calcd. 78.53% for Fe(III) com-
plex and found 61.53, calcd. 61.89% for La(III) complex)
corresponding to the loss of (three p-hydroxyphenyl mole-
cules, C21H21O3 and organic moiety, C2H9N3O4.5) and
(seven water molecules and C15H30N3O7.5 as organic rest
moiety) for [Fe(tyr)3] and [La(tyr)3]Æ7H2O complexes,
respectively. The final products, formed at 800 ꢁC, consist
of metal trioxide (Fig. 3).
3.8.5. [ZrO(tyr)2]Æ2H2O and [UO2(tyr)2]
The TG of [ZrO(tyr)2]Æ2H2O complex, two steps are
shown in the pyrolysis curve at 117 and 306 ꢁC. The first
step corresponding to the dehydration of two water mole-
cules (calcd.: 7.13%, found: 6.53%). The rest of the two
tyrosinate molecules were decomposes in the last step with
the formation of ZrO2 as the final residue.
For UO2(II)-tyrosinate complex consist of three decom-
position steps at 95, 259 and 660 ꢁC. The first step in the
temperature range 25–120 ꢁC corresponds to the melting
point of the ligand, because no loss of weight was detected
in the TG curve and the second step (DTGmax; 259 ꢁC)
seems to be consistent with evolution of two, p-hydroxy
phenyl molecules (calcd.: 33.95%, found: 33.70%). It was
hardly to detect the exact degradation of the organic moi-
eties because of, this step is widely extending from 300 to
3.8.3. [Zn(tyr)2]Æ2H2O, [Cd(tyr)2]Æ2H2O and [Hg(tyr)2]
Thermal decomposition of d10 transition metals com-
plexes; [Zn(tyr)2]Æ2H2O, [Cd(tyr)2]Æ2H2O and [Hg(tyr)2]
proceeds in three and/or four ranged main stages. These
three-to-four stages are related to the decomposition of
two hydrated water molecules and the organic part of the
chelate like two molecule of organic radicals (C7H7O-p-
hydroxyphenyl) from two molecules of the ligand and the
following pyrolysis of the L-tyr rest; (found 72.66%; calcd.
71.95% for Zn(II) complex, found 74.70%; calcd. 74.75%
for Cd(II) complex and found 53.27%; calcd. 52.79% for
Hg(II) complex, respectively), in the temperature ranges
25–800 ꢁC by giving an endothermic effect (DTGmax: 63,
292 and 558 ꢁC; DTGmax: 217, 238, 301 and 521 ꢁC and
DTGmax: 327, 577 and 670 ꢁC) for [Zn(tyr)2]Æ2H2O,
[Cd(tyr)2]Æ2H2O and [Hg(tyr)2] complexes, respectively. In
the sequence stages, the Zn(II), Cd(II) and Hg(II) com-
plexes decomposes in the final steps to oxide (MO;
M = Zn, Cd and Hg).
3.8.4. [Cr(tyr)3]Æ6H2O, [Fe(tyr)3] and [La(tyr)3]Æ7H2O
The TG diagrams of [Cr(tyr)3]Æ6H2O, [Fe(tyr)3] and
[La(tyr)3]Æ7H2O complexes reveal mass loss in the tempera-
ture range 25–800 ꢁC corresponding to the formation of 1/
2M2O3 (M = Cr, Fe and La). The two and/or three endo-
thermic peaks were observed in DTG analysis. The maxims
of these peaks are found to be (DTGmax; 101, 276 and
506 ꢁC) for Cr(III) complex, (DTGmax; 264 and 664 ꢁC)
for Fe(III)-tyrosinate complex, (DTGmax
;
275 and
475 ꢁC), respectively. The first peak in case of chro-
mium(III)-tyrosinate complex was discussed concerning
to the loss of six uncoordinated water molecules of the
Cr(III) complex. The Cr(III), Fe(III) and La(III) com-
plexes are thermally stable up to 506, 664 and 475 ꢁC,
respectively. Respecting of Cr(III) complex, the second
and third peaks correspond to decomposition of the ligand.
The mass losses at 276 and 506 ꢁC DTGmax, respectively,
are endothermic decomposition and corresponding to the
loss of one molecule of p-hydroxyphenyl moiety and
H23N3O6.5 organic rest, and then the final decomposition
Fig. 3. The IR spectra of the metal trioxides; (a) Cr2O3 and (b) Fe2O3.

M.S. Refat et al. / Journal of Molecular Structure 881 (2008) 28–45
41
Table 7
Kinetic parameters determined using the Coats–Redfern (CR) and Horowitz–Metzger (HM) of the L-tyrosine and its complexes
Complex
Stage
Method
Parameter
r
E (kJ molꢀ1
)
A (sꢀ1
)
DS (J molꢀ1 Kꢀ1
)
DH (kJ molꢀ1
)
DG (kJ molꢀ1)
L-Tyr
1st
CR
HM
Average
4.30 · 105
4.39 · 105
4.34 · 105
9.48 · 1035
1.19 · 1037
6.42 · 1036
4.38 · 102
4.59 · 102
4.48 · 102
4.25 · 105
4.35 · 105
4.30 · 105
1.64 · 105
1.61 · 105
1.62 · 105
0.9997
0.9994
I
1st
CR
HM
3.13 · 104
3.84 · 104
3.48 · 104
2.35 · 105
2.39 · 105
1.67 · 105
1.74 · 105
1.70 · 105
2.17 · 105
2.30 · 105
2.23 · 105
1.49 · 105
1.54 · 105
1.51 · 105
1.97 · 105
2.06 · 105
2.02 · 105
1.31 · 105
1.42 · 105
1.36 · 105
6.89 · 103
1.98 · 103
4.43 · 103
2.60 · 1020
8.12 · 1020
9.72 · 1013
6.52 · 1014
3.74 · 103
4.66 · 1010
4.94 · 1010
4.60 · 1010
2.63 · 1021
3.91 · 1021
3.27 · 1021
5.08 · 1015
2.73 · 1017
1.39 · 1017
4.32 · 105
5.57 · 105
1.94 · 105
ꢀ1.73 · 102
ꢀ1.84 · 102
ꢀ1.78 · 102
1.41 · 102
2.82 · 104
3.53 · 104
3.17 · 104
2.30 · 105
2.34 · 105
1.63 · 105
1.69 · 105
1.66 · 105
2.09 · 105
2.22 · 105
2.15 · 105
1.46 · 105
1.52 · 105
1.48 · 105
1.92 · 105
2.02 · 105
1.97 · 105
1.24 · 105
1.36 · 105
1.30 · 105
9.29 · 104
1.04 · 105
9.84 · 104
1.52 · 105
1.51 · 105
1.53 · 105
1.51 · 105
1.52 · 105
2.53 · 105
2.49 · 105
2.51 · 105
9.06 · 104
8.88 · 104
8.97 · 104
1.64 · 105
1.55 · 105
1.59 · 105
2.45 · 105
2.39 · 105
2.69 · 105
0.9954
0.9952
2nd
1st
CR
HM
0.9921
0.9898
1.50 · 102
II
CR
HM
Average
CR
HM
17.80
33.60
25.70
ꢀ49.60
ꢀ30.00
ꢀ39.80
0.9973
0.9980
2nd
0.9968
0.9955
Average
III
1st
CR
HM
Average
CR
HM
Average
CR
HM
1.64 · 102
1.87 · 102
1.75 · 102
50.50
83.60
67.05
ꢀ1.46 · 102
ꢀ1.24 · 102
ꢀ1.81 · 102
0.9939
0.9916
2nd
3rd
0.9635
0.9659
0.9811
0.9785
Average
IV
1st
CR
HM
Average
CR
HM
Average
CR
HM
Average
CR
HM
3.36 · 104
4.20 · 104
3.78 · 104
2.76 · 105
2.80 · 105
2.78 · 105
2.52 · 105
2.48 · 105
2.50 · 105
2.08 · 105
2.29 · 105
2.18 · 105
2.30 · 103
2.07 · 103
2.05 · 103
3.03 · 1027
2.19 · 1028
1.24 · 105
4.99 · 1023
6.83 · 1023
5.91 · 1023
2.35 · 1017
1.48 · 1019
7.51 · 1018
ꢀ1.82 · 102
ꢀ1.64 · 102
ꢀ1.73 · 102
2.77 · 102
2.94 · 102
2.85 · 102
2.04 · 102
2.07 · 102
2.05 · 105
82.20
3.07 · 104
3.91 · 104
3.49 · 104
2.72 · 105
2.76 · 105
2.74 · 105
2.47 · 105
2.44 · 105
2.45 · 105
2.03 · 105
2.24 · 105
2.13 · 105
9.40 · 104
9.60 · 104
9.50 · 104
1.36 · 105
1.32 · 105
1.34 · 105
1.43 · 105
1.38 · 105
1.40 · 105
1.56 · 105
1.57 · 105
1.56 · 105
0.9904
0.9942
2nd
3rd
4th
0.9972
0.9991
0.9892
0.9843
0.9978
0.9964
117.0
99.0
Average
V
1st
CR
HM
Average
CR
HM
Average
CR
HM
2.21 · 105
2.40 · 105
2.61 · 105
1.28 · 105
1.33 · 105
1.30 · 105
4.94 · 105
5.08 · 105
5.01 · 105
1.84 · 1017
1.57 · 1019
4.94 · 1018
2.49 · 107
1.56 · 108
9.04 · 107
2.63 · 1028
3.88 · 1029
2.07 · 1029
79.8
117.0
98.4
2.16 · 105
2.35 · 105
2.25 · 105
1.22 · 105
1.27 · 105
1.25 · 105
4.86 · 105
5.01 · 105
5.43 · 105
1.68 · 105
1.65 · 105
1.65 · 105
1.97 · 105
1.92 · 105
1.95 · 105
2.40 · 105
2.36 · 105
2.38 · 105
0.9955
0.9960
2nd
3rd
ꢀ110.0
0.9840
0.9816
ꢀ94.9
ꢀ102.4
2.90 · 102
3.13 · 102
3.01 · 102
0.9879
0.9874
Average
VI
1st
CR
HM
Average
CR
HM
Average
CR
HM
4.11 · 104
9.28 · 104
6.69 · 104
1.74 · 105
1.85 · 105
1.79 · 105
9.33 · 104
1.04 · 105
9.86 · 104
3.00 · 103
1.97 · 1011
9.85 · 1010
6.12 · 1014
7.53 · 1015
4.07 · 1015
3.40 · 105
4.00 · 105
3.70 · 105
ꢀ180.0
3.80 · 104
8.97 · 104
6.38 · 104
1.70 · 105
1.80 · 105
1.75 · 105
8.81 · 104
9.91 · 104
9.36 · 104
1.05 · 105
1.01 · 105
1.03 · 105
1.52 · 105
1.51 · 105
1.51 · 105
1.79 · 105
1.77 · 105
1.78 · 105
0.9921
0.9960
ꢀ30.6
ꢀ105.3
2nd
3rd
33.10
0.9980
0.9995
54.00
43.55
ꢀ1.45 · 102
ꢀ1.25 · 102
ꢀ1.35 · 102
0.9882
0.9995
Average
VII
1st
CR
HM
Average
CR
HM
2.08 · 105
2.22 · 105
2.15 · 105
9.52 · 104
1.02 · 105
9.86 · 104
3.01 · 1018
7.70 · 1019
4.00 · 1019
3.22 · 104
2.46 · 104
2.84 · 104
1.04 · 102
1.31 · 102
1.17 · 102
ꢀ1.86 · 102
ꢀ1.69 · 102
ꢀ1.77 · 102
2.04 · 105
2.17 · 105
2.10 · 105
8.86 · 104
9.58 · 104
9.22 · 104
1.48 · 105
1.47 · 105
1.47 · 105
2.37 · 105
2.31 · 105
2.34 · 105
0.9978
0.9985
2nd
0.9798
0.9802
Average
(continued on next page)

42
M.S. Refat et al. / Journal of Molecular Structure 881 (2008) 28–45
Table 7 (continued)
Complex
Stage
Method
Parameter
r
E (kJ molꢀ1
)
A (sꢀ1
)
DS (J molꢀ1 Kꢀ1
)
DH (kJ molꢀ1
)
DG (kJ molꢀ1)
VIII
1st
CR
HM
Average
CR
HM
3.31 · 104
3.95 · 104
3.63 · 104
2.22 · 105
2.28 · 105
2.25 · 105
2.08 · 103
8.28 · 103
5.18 · 103
1.85 · 1019
1.28 · 1019
1.56 · 1019
ꢀ1.83 · 102
ꢀ1.71 · 102
ꢀ1.77 · 102
1.19 · 102
1.35 · 102
1.27 · 102
3.02 · 104
3.66 · 104
3.34 · 104
2.17 · 105
2.24 · 105
2.20 · 105
9.38 · 104
9.62 · 104
9.50 · 104
1.52 · 105
1.50 · 105
1.51 · 105
0.9860
0.9950
2nd
0.9943
0.9931
Average
IX
1st
CR
HM
Average
CR
HM
3.10 · 104
3.54 · 104
3.32 · 104
2.97 · 105
3.09 · 105
3.03 · 105
9.33 · 103
3.94 · 102
4.86 · 103
1.00 · 1025
1.96 · 1025
1.98 · 1025
ꢀ1.71 · 102
ꢀ1.97 · 102
ꢀ1.84 · 102
2.28 · 102
2.53 · 102
2.40 · 102
2.78 · 104
3.21 · 104
2.99 · 104
2.92 · 105
3.04 · 105
2.98 · 105
9.44 · 104
1.09 · 105
1.01 · 105
1.60 · 105
1.58 · 105
1.59 · 105
0.9708
0.9782
2nd
0.9994
0.9995
Average
X
1st
CR
HM
Average
CR
HM
Average
CR
HM
1.46 · 105
1.53 · 105
1.49 · 105
2.75 · 105
2.87 · 105
2.81 · 105
1.14 · 105
1.23 · 105
1.18 · 105
1.57 · 1019
1.56 · 1019
1.56 · 1019
2.24 · 1025
4.64 · 1025
6.88 · 1025
4.82 · 107
2.78 · 107
3.80 · 106
1.21 · 102
1.40 · 102
1.30 · 102
2.36 · 102
2.61 · 102
2.48 · 102
ꢀ1.24 · 102
ꢀ1.09 · 102
ꢀ1.16 · 102
1.43 · 105
1.50 · 105
1.46 · 105
2.71 · 105
2.83 · 105
2.76 · 105
1.08 · 105
1.17 · 105
1.12 · 105
9.83 · 104
9.81 · 104
9.82 · 104
1.46 · 105
1.44 · 105
1.45 · 105
1.91 · 105
1.91 · 105
1.91 · 105
0.9954
0.9929
2nd
3rd
0.9880
0.9896
0.9770
0.9739
Average
800 ꢁC. The weight loss of this complex is 29.87% and its
where g(a) is a function of a dependent on the mechanism
of the reaction. The integral on the right-hand side is
known as temperature integral and has no closed for solu-
tion. So, several techniques have been used for the evalua-
tion of temperature integral. Most commonly used
methods for this purpose are the differential method of
Freeman and Carroll [38] integral method of Coat and
Redfern [40], the approximation method of Horowitz and
Metzger [43].
In the present investigation, the general thermal behav-
iors of the L-tyrosine ligand and the 10 complexes in terms
of stability ranges, peak temperatures and values of kinetic
parameters are tabulated Table 7. The kinetic parameters
have been evaluated using the following methods and the
results obtained by these methods are compared with one
another. The following two methods are discussed in brief.
calculated value is 28.29%.
3.9. Kinetic studies
In recent years there has been increasing interest in
determining the rate-dependent parameters of solid-state
non-isothermal decomposition reactions by analysis of
TG curves. Several equations [38–45] have been proposed
as means of analyzing a TG curve and obtaining values
for kinetic parameters. Many authors [38–42] have dis-
cussed the advantages of this method over the conventional
isothermal method. The rate of a decomposition process
can be described as the product of two separate functions
of temperature and conversion [39], using
da=dt ¼ kðTÞf ðaÞ
ð1Þ
where a is the fraction decomposed at time t, k(T) is the
temperature dependent function and f(a) is the conversion
function dependent on the mechanism of decomposition. It
has been established that the temperature dependent func-
tion k(T) is of the Arrhenius type and can be considered as
the rate constant k.
3.9.1. Coats–Redfern equation
The Coats–Redfern equation, which is a typical integral
method, can be represented as:
ꢁ
ꢂ
Z
Z
a
T2
da
A
u
Eꢄ
RT
¼
exp
ꢀ
dt
n
ð1 ꢀ aÞ
0
T1
ꢄ
k ¼ AeꢀE =RT
ð2Þ
For convenience of integration the lower limit T1 is usually
taken as zero. This equation on integration gives;
where R is the gas constant in (J molꢀ1 Kꢀ1). Substituting
ꢃ
ꢄ
ꢃ
ꢄ
lnð1 ꢀ aÞ
Eꢄ
RT
AR
uEꢄ
Eq. (2) into Eq. (1), we get,
ln ꢀ
¼ ꢀ
þ ln
T2
ꢄ
da=dT ¼ ðA=/eꢀE =RT Þf ðaÞ
A plot of left-hand side (LHS) against 1/T was drawn. E* is
the energy of activation in kJ molꢀ1 and calculated from
the slop and A in (sꢀ1) from the intercept value. The entro-
py of activation DS* in (J Kꢀ1 molꢀ1) was calculated by
using the equation:
where / is the linear heating rate dT/dt. On integration and
approximation, this equation can be obtained in the fol-
lowing form
ln gðaÞ ¼ ꢀEꢄ=RT þ ln½AR=/Eꢄꢂ

M.S. Refat et al. / Journal of Molecular Structure 881 (2008) 28–45
43
Table 8
Antibacterial activity data of the L-tyrosine and its complexes
Compound
Bacillus subtilis
Serratia
Pseudomonas aeruginosa
E. coli
L-Tyrosine
+++
+++
++++
+++
+++
+++
++++
++++
++++
–
–
–
–
+++
++
+++
++++
+
++++
+
++
[Sn(tyr)2]ÆH2O
[Sn(tyr)2(Cl)2]
[Zn(tyr)2]Æ2H2O
[Cd(tyr)2]Æ2H2O
[Hg(tyr)2]
[Cr(tyr)3]Æ6H2O
[Fe(tyr)3]
[La(tyr)3]Æ7H2O
[ZrO(tyr)2]Æ2H2O
[UO2(tyr)2]
++++
–
++++
–
–
–
–
–
++
+++
++++
–
++
–
++
+++
+++
++
–
–
++
+++
+
(–) NO antibacterial activity, (+) mild activity, (++) moderate activity, (+++) marked activity, (++++) strong marked activity.
DSꢄ ¼ R lnðAh=kBT sÞ
where kB is the Boltzmann constant, h is the Plank’s con-
ð3Þ
3.9.2. Horowitz–Metzger equation
The Horowitz–Metzger equation is an illustrative of the
approximation methods. These authors derived the
relation:
stant and Ts is the DTG peak temperature [46].
1ꢀn
log½f1 ꢀ ð1 ꢀ aÞ g=ð1 ꢀ nÞꢂ
¼ Eꢄh=2:303RT 2s for n ¼ 1
ð4Þ
The effect of L-tyrosine complexes on Serratia
When n = 1, the LHS of Eq. (4) would be log[ꢀlog (1 ꢀ a)].
For a first-order kinetic process the Horowitz–Metzger
equation may be written in the form:
(Htyr)
Sn(II)
Sn(IV)
Zn(II)
log½logðwa=wcÞꢂ ¼ Eꢄh=2:303RT s2 ꢀ log 2:303
where h = T ꢀ Ts, wc = wa ꢀ w, wa = mass loss at the com-
pletion of the reaction; w = mass loss up to time t. The plot
of log[log(wa/wc)] vs h was drawn and found to be linear
from the slope of which E* was calculated. The pre-expo-
nential factor, A, was calculated from the equation:
Cd(II)
Hg(II)
Cr(III)
Fe(III)
La(III)
ZrO(II)
UO2(II)
Eꢄ=RT 2s ¼ A=½/ expðꢀEꢄ=RT sÞꢂ
The entropy of activation, DS*, was calculated from Eq.
(3). The enthalpy activation, DH*, and Gibbs free energy,
DG*, were calculated from; DH* = E* ꢀ RT and
DG* = DH* ꢀ TDS*, respectively.
UO2(II) ZrO(II) La(III) Fe(III) Cr(III) Hg(II) Cd(II) Zn(II) Sn(IV) Sn(II) (Htyr)
The effect of L-tyrosine complexes on Aspegillus flavus Ps.
(Htyr)
Sn(II)
Sn(IV)
Zn(II)
Table 9
Antifungal activity data for L-tyrosine and its complexes
Compound
Aspergillus
flavus
Fusarium
solani
Penicillium
verrucosum
Cd(II)
Hg(II)
Cr(III)
Fe(III)
La(III)
ZrO(II)
UO2(II)
L-Tyrosine
–
–
+
–
–
–
+++
++
++
–
–
–
+
–
+
+
–
+
+
+
+
++
+
[Sn(tyr)2]ÆH2O
[Sn(tyr)2(Cl)2]
[Zn(tyr)2]Æ2H2O
[Cd(tyr)2]Æ2H2O
[Hg(tyr)2]
[Cr(tyr)3]Æ6H2O
[Fe(tyr)3]
[La(tyr)3]Æ2H2O
+++
+
+
++++
++++
+++
++
++
[ZrO(tyr)2]Æ2H2O ++++
[UO2(tyr)2]
UO2(II) ZrO(II) La(III) Fe(III) Cr(III) Hg(II) Cd(II) Zn(II) Sn(IV) Sn(II) (Htyr)
–
(–) NO antibacterial activity, (+) mild activity, (++) moderate activity,
(+++) marked activity, (++++) strong marked activity.
Fig. 4. The inhabitation zone of the L-tyrosine and their metal complexes
on some kinds of bacterial and fungi.

44
M.S. Refat et al. / Journal of Molecular Structure 881 (2008) 28–45
Scheme 6. The structures of di-, tri-, and tetra-valent metal ion complexes.
[5] D. Van der Helm, C.E. Tatsch, Acta Crystallogr. Sect. B 28 (1972)
2307.
3.10. Microbiological investigation
[6] B.L. Vallee, W.E.C. Wacker, in: H. Neurath (Ed.), Metalloproteins,
vol. 5, Academic Press, New York and London, 1970.
[7] T. Kiss, A. Gergely, J. Chem. Soc. Dalton Trans. (1984) 1951.
[8] J.E. Letter Jr, J.E. Bauman Jr, J. Am. Chem. Soc. 92 (1970) 443.
[9] Hao Xu, Liang Chen, Spectrochim. Acta A 59 (2003) 657.
[10] G. Devi Indira, Parameswaran Geetha, S.S. Veena, Asian J. Chem. 16
(2) (2004) 884.
[11] C.A. McAuliffe, S.G. Murray, Inorgan. Chim. Acta 7 (1973) 171.
[12] (a) S.H. Lauri, Chem. Comm. 155 (1967);
(b) Aust. J. Chem. 20 (1967) 2609.
[13] A. Earnshow, Introduction to Magneto Chemistry, Academic press,
New York, 1968.
L-Tyrosine is sometimes recommended by practitioners
as helpful for weight loss, clinical depression, Parkinson’s
disease, and phenyl ketonuria; however, one study found
that it had no impact on endurance exercise perfor-
mance. It is useful in phenyl ketonuria because whereas
phenyl ketonurias cannot met a bolize phenylalanine into
tyrosine, they just stay off the phenylalanine and set trea-
ted with tyrosine and other amino acids extracted from
proteins [47].
The results of antibacterial actives in vitro of the
ligand and the complexes are shown in Table 8 and
Fig. 4. From the results we can see that all the test com-
pounds have lower antibacterial on Serratia (except for
Zn(II) and Hg(II) tyrosinate complexes) and the (Sn(IV),
Cr(III), Fe(III) and La(III) tyrosinate complexes)
enhanced the activity on Bacillus subtilis. The zinc(II)
tyrosinate complex has high activity against Pseudomonas
aeruginosa. The L-tyrosine and their complexes have been
evaluated for their antifungal activity. The minimal
inhibitory concentration values listed in Table 9 show
that all the test compounds have the order of antifungal
activity as Fusarium solani > Aspergillus flavus > Penicil-
lium verrucosum.
[14] W.J. Geary, Coord. Chem. Rev. 7 (1971) 81.
[15] K. Nakamoto, Infrared and Raman Spectra of Inorganic and
Coordination compounds, fourth ed., Wiley, New York, 1986.
[16] Y. Inomata, T. Inomata, T. Moriwaki, Bull. Chem., Soc. Jap. 47 (4)
(1974) 818.
[17] J.F. Vilia, W.E. Hatfield, Chem. Phys. Lett. 9 (6) (1971) 568.
[18] T.J. Lane, J.A. Durkin, R.J. Hooper, Spectrochim. Acta 20 (1964)
1017.
[19] I. Nakagaw, R.J. Hooper, J.L. Walter, T.J. Lane, Spectrochim. Acta
21 (1965) 1.
[20] J.F. Jackovitz, J.L. Walter, Spectrochim. Acta 22 (1966) 1393.
[21] J.F. Jackovitz, J.A. Durkin, J.L. Walter, Spectrochim. Acta 23A
(1967) 67.
[22] R.F. de farieas, J. Scatena Jr., C. Airoldi, J. Inorg. Biochem. 73 (1999)
253.
[23] R.F. de farieas, C. Airoldi, J. Inorg. Biochem. 76 (1999) 273.
[24] S.P. Mc Glynm, J.K. Smish, W.C. Neely, J. Chem. Phys. 35 (1961)
105.
3.11. Structure of the tyrosinate complexes
[25] L.H. Jones, Spectrochim. Acta 15 (1959) 409.
[26] J. Selbin, Chem. Rev. 65 (1965) 153.
The structures of the L-tyrosinate complexes (I–X)
accordingly the above interpretation using elemental anal-
ysis, magnetic studies, molar conductance, (infrared, 1H
NMR, Mass) spectra as well as thermogravimetric analysis
can be suggested as shown in Scheme 6.
[27] W. Barnum, J. Inorg. Nucl. Chem. 21 (1961) 221.
[28] R.H. Holm, F.A. Cotton, J. Am. Chem. Soc. 80 (1958) 5658.
[29] F.A. Cotton, C.W. Wilkinson, in: Advanced Inorganic Chemistry,
third ed., Interscience Publisher, New York, 1972.
[30] J.E. Letter Jr., J.E. Bauman Jr., J. Am. Chem. Soc. 92 (1970) 447.
[31] V.D. Panasynk, V.A. Golab, Russ. J. Inorg. Chem. 14 (1965) 1485.
[32] R. Roy, M.C. Saha, P.S. Roy, Trans. Met. Chem. 5110 (1990) 51.
[33] P.P. Carbi, F. Cagnim, L.P.B. Sabeh, A.C. Massabni, C.M. Costa-
Neto, Spectrochim. Acta part A 66 (4–5) (2007) 1171.
[34] R.F. de Farias, H.C. Airoldi, H. Scatena Jr., J. Inorg. Biochem. 73
(1999) 253.
References
[1] Norbert sewald and Hans-Dieter jakube ‘‘peptides: chemistry and
biology, wiley-VCH verlag Gmb H& Co. KGaA, 2002.
[35] R.F. de Farias, H.C. Airoldi, J. Inorg. Biochem. 76 (1999) 273.
[36] K. Burger, Coordination Chemistry: Experimental Methods, Akade-
miai Kiado, Budapest, 1973, p. 23.
[37] Qu Lunyu, Sun Yingji, Chen Yaguang, Yu Ming, Pen Jun, Synth.
React. Inorg. Met.-Org. Chem. 24 (1994) 1339.
[2] passim J.P. Greenstein, M. Winitz, Chemistry of the Amino Acids,
vol. 1–3, John Wiley and Sons, Inc., New York, 1961.
[3] A. Magnuson, Y. Frapart, M. Abrahamsson, O. Horner, B.
Kermark, L. Sun, G. Jean-Jacques, L. Hammarstroem, S. Styring,
J. Am. Chem. Soc. 121 (1) (1999) 89.
[38] E.S. Freeman, B. Carroll, J. Phys. Chem. 62 (1958) 394.
[4] R.J.W. Hefford, L.D. Pettit, J. Chem. Soc. Dalton Trans. (1981) 1331.

M.S. Refat et al. / Journal of Molecular Structure 881 (2008) 28–45
45
[39] J. Sestak, V. Satava, W.W. Wendlandt, Thermochim. Acta 7 (1973) 333.
[43] H.W. Horowitz, G. Metzger, Anal. Chem. 35 (1963) 1464.
[44] J.H. Flynn, L.A. Wall, Polym. Lett. 4 (1966) 323.
[45] P. Kofstad, Nature 179 (1957) 1362.
[46] J.H.F. Flynn, L.A. Wall, J. Res. Natl. Bur. Stand. 70A (1996) 487.
[47] A.C. par cell et al., J. Appl. Physiol. 93 (5) (2002) 1590.
[40] A.W. Coats, J.P. Redfern, Nature 201 (1964) 68.
[41] T. Ozawa, Bull. Chem. Sot. Jpn. 38 (1965) 1881.
[42] W.W. Wendlandt, Thermal Methods of Analysis, Wiley, New York,
1974.