Synthesis, investigation and spectroscopic characterization of piroxicam ternary complexes of Fe(II), Fe(III), Co(II), Ni(II), Cu(II) and Zn(II) with glycine and DL-phenylalanine

Article abstract of DOI:10.1016/j.saa.2004.01.035

The ternary piroxicam (Pir; 4-hydroxy-2-methyl-N-(2-pyridyl)-2H-1,2- benzothiazine-3-carboxamide 1,1-dioxide) complexes of Fe(II), Fe(III), Co(II), Ni(II), Cu(II) and Zn(II) with various amino acids (AA) such as glycine (Gly) or DL-phenylalanine (PhA) were prepared and characterized by elemental analyses, molar conductance, IR, UV-Vis, magnetic moment, diffuse reflectance and X-ray powder diffraction. The UV-Vis spectra of Pir and the effect of metal chelation on the different interligand transitions are discussed in detailed manner. IR and UV-Vis spectra confirm that Pir behaves as a neutral bidentate ligand coordinated to the metal ions via the pyridine-N and carbonyl group of the amide moiety. Gly molecule acted as a uninegatively monodentate ligand and coordinate to the metal ions through its carboxylic group, in addition PhA acted as a uninegatively bidentate ligand and coordinate to the metal ions through its carboxylic and amino groups. All the chelates have octahedral geometrical structures while Cu(II)- and Zn(II)-ternary chelates with PhA have square planar geometrical structures. The molar conductance data reveal that most of these chelates are non electrolytes, while Fe(III)-Pir-Gly, Co(II)-, Ni(II)-, Cu(II)- and Zn(II)-Pir-PhA cheletes were 1:1 electrolytes. X-ray powder diffraction is used as a new tool to estimate the crystallinity of chelates as well as to elucidate their geometrical structures.

Full text of DOI:10.1016/j.saa.2004.01.035

Spectrochimica Acta Part A 60 (2004) 3141–3154
Synthesis, investigation and spectroscopic characterization of piroxicam
ternary complexes of Fe(II), Fe(III), Co(II), Ni(II), Cu(II)
and Zn(II) with glycine and dl-phenylalanine
Gehad G. Mohamed∗, Nadia E.A. El-Gamel
Chemistry Department, Faculty of Science, Cairo University, Giza, Egypt
Received 22 December 2003; accepted 27 January 2004
Abstract
The ternary piroxicam (Pir; 4-hydroxy-2-methyl-N-(2-pyridyl)-2H-1,2-benzothiazine-3-carboxamide 1,1-dioxide) complexes of Fe(II),
Fe(III), Co(II), Ni(II), Cu(II) and Zn(II) with various amino acids (AA) such as glycine (Gly) or dl-phenylalanine (PhA) were prepared and
characterized by elemental analyses, molar conductance, IR, UV-Vis, magnetic moment, diffuse reflectance and X-ray powder diffraction. The
UV-Vis spectra of Pir and the effect of metal chelation on the different interligand transitions are discussed in detailed manner. IR and UV-Vis
spectra confirm that Pir behaves as a neutral bidentate ligand coordinated to the metal ions via the pyridine-N and carbonyl group of the amide
moiety. Gly molecule acted as a uninegatively monodentate ligand and coordinate to the metal ions through its carboxylic group, in addition
PhA acted as a uninegatively bidentate ligand and coordinate to the metal ions through its carboxylic and amino groups. All the chelates have
octahedral geometrical structures while Cu(II)- and Zn(II)-ternary chelates with PhA have square planar geometrical structures. The molar
conductance data reveal that most of these chelates are non electrolytes, while Fe(III)-Pir-Gly, Co(II)-, Ni(II)-, Cu(II)- and Zn(II)-Pir-PhA
cheletes were 1:1 electrolytes. X-ray powder diffraction is used as a new tool to estimate the crystallinity of chelates as well as to elucidate
their geometrical structures.
© 2004 Elsevier B.V. All rights reserved.
Keywords: Piroxicam; Ternary chelates; IR; Magnetic and diffuse reflectance spectra; UV-Vis; XRD
1. Introduction
ease characterized by painful disorders in the muscle and
joints. At present, therapeutical treatment, for this illness
are mainly based on non-steroidal anti-inflammatory drugs
(NSAIDs), characterized by rapid and complete uptake in
the blood stream and thus possessing a fast analgesic action
[6]. Piroxicam (Pir; 4-hydroxy-2-methyl-N-(2-pyridyl)-2H-
1,2-benzothiazine-3-carboxamide 1,1-dioxide) is the most
important member of oxicams class (Fig. 1) [6–10] to be
strong chelators for several divalent metal ions from the
‘d-block’ of the periodic table, via the amide oxygen atom
and nitrogen atoms from the pyridyl or thiazolyl rings
[8,9]. In this type of compounds the enol oxygen atom is
always deprotonated, is not linked to the metal but instead
is linked to the N–H function via a strong intramolecular
hydrogen bond mode possible by ZZZ conformation at the
C(3)–C(4), C(14)–N(16) and N(16)–C(2ꢀ) vectors. The in-
volvement of the enolate oxygen atom of ‘oxicam’ ligands
in the coordination to the metals has been clearly shown
only in the case of Sn(IV) complex [11] and this is related
to a highly affinity of this metal ion towards the oxygen
An intensive number of studies on the formation of
mixed ligand complexes reveals a realization of their
growing importance, particularly in their role in biolog-
ical process [1]. The formation of mixed ligand chelates
is a general feature of systems where a metal is present
with two or more ligands. The study of these complexes
shows that their formations are a favoured process over
that of simple complexes [2]. The study of ternary com-
plexes involving an aromatic amine as the primary ligand,
various amino acids (AA) and biomolecules as secondary
ligands can serve as useful models for gaining a better
understanding of enzyme–metal ion–substrate complexes,
which play an important role in metalloenzyme-catalysed
biochemical reactions [3–5]. Rheumatoid arthritis is a dis-
∗
Corresponding author.
E-mail address: ggenidy@hotmail.com (G.G. Mohamed).
1386-1425/$ – see front matter © 2004 Elsevier B.V. All rights reserved.
doi:10.1016/j.saa.2004.01.035

3142
G.G. Mohamed, N.E.A. El-Gamel / Spectrochimica Acta Part A 60 (2004) 3141–3154
2.2. Instrumentation
The spectrophotometric measurements in solution were
carried out using automated spectrophotometer UV/Vis
Perkin-Elmer Model Lambda 20 ranged from 200 to 900 nm.
Elemental microanalysis of the separated solid chelates for
C, H, N, and S were performed in the Microanalytical Cen-
ter, Cairo University. The analyses were repeated twice to
check the accuracy of the analyses data. Infrared spectra
were recorded on a Perkin-Elmer FT-IR type 1650 spec-
trophotometer in wavenumber region 4000–200 cm−1. The
spectra were recorded as KBr pellets. The solid reflectance
spectra were measured on a Shimadzu 3101pc spectropho-
tometer. The molar magnetic susceptibility was measured
on powdered samples using the Faraday method. The dia-
magnetic corrections were made by Pascal’s constant and
Hg[Co(SCN)4] was used as calibrant.
The X-ray powder diffraction analyses were carried out
by using Rigku Model ROTAFLEX Ru-200. Radiation was
provided by copper target (Cu anode 2000 W) high intensity
X-ray tube operated at 40 KV and 35 MA. Divergence slit
and the receiving slit were 1 and 0.1, respectively. Metal con-
tents were determined by titration against standard EDTA
after complete decomposition of the complexes with aqua
regia in kjeldahl flask. The water was always de-ionized
obtained from Altra clear SG-Wasser aufbereitung und re-
generierstation GmbH instrument.
Fig. 1. Structural formula for piroxicam (H2Pir).
donor, and to the deprotonated form of the ligand used
in the preparative procedure (Pir2−, H2Pir, piroxicam) as
shown in Fig. 1.
With the aim to continue the exploration of the coor-
dination mode adopted by piroxicam we have performed
a preparative and structural work by using piroxicam (as
primary ligand) with various amino acids such as glycine
(Gly) as an example of non-essential amino acid and dl-
phenylalanine (PhA) as an example of essential amino
acid (as secondary ligand) with some ‘d-block’ metal ions
by employing the amide oxygen and pyridyl nitrogen of
the drug molecule with deprotonated carboxylate group
in unidentate manner of glycine and uninegatively biden-
tate through deprotonated carboxylate and amino groups
of dl-phenylalanine. The solid chelates are characterized
using different physico-chemical methods like IR, UV-
Vis, molar conductance, magnetic moment and diffuse
reflectance spectra. XRD technique is also utilized as a
confirmatory tool for elucidation the crystallinity of the
chelates.
2.3. Synthesis
A hot ethanol solution (60 ◦C) of the respective metal
chlorides (Fe(II), Fe(III), Co(II) and Ni(II)) or acetate (Cu(II)
and Zn(II)) solutions (1 mmol) in de-ionized water (25 ml)
were added to 25 ml hot ethanol solution (60 ◦C) of Pir
(0.331 g, 1 mmol) followed by addition of 25 ml 1 mmol Gly
(0.075 g in de-ionized water) or 25 ml 1 mmol PhA (0.165 g
in ethanol) in the molar ratio 1:1:1 (metal salt: Pir: Gly
or PhA) in total volume 75 ml mixture. The resulting mix-
ture was stirred under reflux for 30 min. The complexes
were precipitated as microcrystalline powders. They were
removed by filtration, washed with hot ethanol followed by
diethylether and dried in a vacuum desiccator over anhy-
drous calcium chloride. All the complexes are coloured and
received as powder. Their stoichiometries were confirmed
by chemical analysis. The m.p. and analytical data are col-
lected in Table 1.
2. Experimental
2.1. Materials
All chemicals used were of the analytical reagent grade
(AR), and of highest purity available. They included
piroxicam, an authentic sample was kindly supplied by
Pfizer Company, Cairo (Egypt) and its melting point was
checked (198 ◦C) to confirm its purity. Amino acids; dl-
phenylalanine was supplied from Acros (USA), while
glycine was supplied from Sigma.
Copper(II) acetate dihydrate (Prolabo); cobalt(II) and
nickel(II) chlorides hexahydrate (BDH); zinc acetate dihy-
drate (Ubichem), anhydrous ferrous sulphate (Sigma) and
ferric chloride hexahydrated (Prolabo), boric acid (BDH),
phosphoric and glacial acetic acids (AR) were used. Zinc
oxide, disodium salt of ethylenediaminetetraacetic acid
(EDTA; Analar), ammonia solution (33% v/v) and ammo-
nium chloride (El Nasr pharm. Chem. Co., Egypt). Ab-
solute ethyl alcohol, diethylether, nitric acid (Analar) and
dimethylformamide (DMF) were supplied from ADWIC.
Hydrogen peroxide and sodium hydroxide were supplied
from Prolabo. De-ionized water collected from all glass
equipments was usually used in all preparations.
3. Results and discussion
The purity of Pir is checked from 1H NMR study (Fig. 2)
where the spectrum shows a sharp singlet signals at δ =
8.9 and 13.3 ppm with integrations correspond to one NH
and one OH protons, respectively. Also, the spectrum shows
a multiple peaks at δ = 7.13–8.31 ppm and singlet sharp
peak at δ = 2.91 ppm with integrals correspond to eight

Table 1
Analytical and physical data of Pir chelates with Gly and PhA
Compound
Chemical formula
Colour
m.p. (◦C)
Found, calcd. (%)
µeff
(B.M.)
Λm
(ꢀ−1 cm2 mol−1
)
C
H
N
S
M
[Pir]
[PhA]
[Gly]
C15H13N3O4S
C9H11NO2
C2H5NO2
White
White
White
198
54.50 (54.38)
65.60 (65.45)
32.00 (31.80)
42.90 (43.08)
43.15 (43.52)
43.65 (43.35)
43.25 (43.35)
46.60 (46.23)
44.40 (44.31)
45.50 (45.35)
44.95 (45.00)
46.12 (46.06)
46.25 (46.04)
46.20 (49.09)
46.40 (46.36)
3.70 (3.90)
6.43 (6.6)
12.34 (12.68)
8.60 (8.48)
9.55 (9.66)
–
–
–
–
–
–
–
–
–
–
–
267 ◦C dec
245 ◦C dec
193
6.80 (6.60)
4.35 (4.54)
4.20 (4.05)
3.45 (3.61)
3.45 (3.60)
4.55 (4.19)
4.10 (4.17)
4.21 (4.25)
3.90 (4.06)
4.45 (4.30)
4.48 (4.30)
4.45 (4.40)
4.80 (4.90)
18.42 (18.66)
11.70 (11.83)
11.86 (11.95)
11.85 (11.90)
11.95 (11.90)
12.75 (12.69)
12.30 (12.29)
8.60 (8.82)
8.70 (8.75)
8.85 (8.95)
8.87 (8.95)
8.75 (8.81)
Fe(II)-Pir-Gly
Fe(III)-Pir-Gly
Co(II)-Pir-Gly
Ni(II)-Pir-Gly
Cu(II)-Pir-Gly
Zn(II)-Pir-Gly
Fe(II)-Pir-PhA
Fe(III)-Pir-PhA
Co(II)-Pir-PhA
Ni(II)-Pir-PhA
Cu(II)-Pir-PhA
Zn(II)-Pir-PhA
[Fe(Pir)2(Gly)2]·4.5H2O
[Fe(Pir)2(Gly)2]Cl·2H2O
[Co(Pir)2(Gly)2]·4H2O
[Ni(Pir)2(Gly)2]·4H2O
[Cu(Pir)2(Gly)2]·1.5H2O
[Zn(Pir)2(Gly)2]·2H2O
[Fe(Pir)(PhA)(H2O)2]0.5SO4
[Fe(Pir)(PhA)Cl2]·H2O
[Co(Pir)(PhA)(H2O)2]Cl
[Ni(Pir)(PhA)(H2O)2]Cl
[Cu(Pir)(PhA)](Ac)·H2O
[Zn(Pir)(PhA)(H2O)2](Ac)·H2O
Reddish brown
Reddish brown
Orange
Light green
Olive green
Lemon
Reddish brown
Reddish brown
Orange
Light green
Olive green
Lemon
6.32 (6.76)
6.90 (6.82)
6.75 (6.80)
6.70 (6.80)
7.35 (7.25)
6.98 (7.02)
7.72 (7.56)
4.90 (5.00)
5.40 (5.12)
5.25 (5.11)
5.25 (5.03)
4.60 (4.75)
5.67 (5.91)
5.70 (5.97)
5.66 (6.27)
6.27 (6.27)
7.62 (7.19)
7.14 (7.28)
8.29 (8.82)
4.52 (4.38)
9.60 (9.43)
9.27 (9.43)
9.36 (9.99)
9.32 (9.66)
5.12
5.92
5.10
2.86
2.0
Diam.
4.91
5.70
5.40
3.40
1.70
Diam.
17.70
130
29.0
22.0
10.1
25.0
156
15.70
115
105
120
135
169
204
218
159
223
200
218
140
175
170
220
8.44 (8.32)

3144
G.G. Mohamed, N.E.A. El-Gamel / Spectrochimica Acta Part A 60 (2004) 3141–3154
The mixed ligand complexes of Pir and PhA with the same
transition metals are formed with 1:1:1 ratio [metal salts: Pir:
PhA]. The Fe(II), Co(II), Ni(II), Cu(II) and Zn(II)-ternary
chelates have the formula [M(H2L)(PhA)(H2O)x](A)·H2O
where A = acetate in case of Cu(II) (x = 0) and Zn(II) (x =
2); sulphate in case of Fe(II) (x = 2) or Cl− in case of Co(II)
(x = 2) and Ni(II) (x = 2); whereas in case of Fe(III)-ternary
chelate, it has the formula [Fe(H2L)(PhA)(Cl)2]·H2O.
3.1. UV-Vis spectra of ternary chelates
Figs. 3 and 4 show the absorption spectra of piroxicam
ternary chelates with glycine and phenylalanine, respec-
tively, in absolute ethanol at wavelength ranging from 200 to
600 nm against the same solvent as a blank. It was shown that
Pir gives three maximum bands at 205, 256 and 360 nm and
shoulder band at 291 nm. While Gly and PhA exhibit three
maximum bands at 204–207, 258–259 and 362–370 nm and
one shoulder band at 291 nm. The higher energy band at
204–207 nm may be attributed to ␴−␴* transition (ꢁ =
2.1–4.4 × 105 l mol−1 cm−1) while the lower energy bands
(λ = 256–259 nm) can be assigned to n–␲* and ␲–␲* tran-
sitions (ε = 7–15 × 104 l mol−1 cm−1) within Gly and PhA
molecules.
It is obvious from the absorption spectra obtained that
all the ternary chelates of Pir with Gly or PhA give the
same behaviour. The first and second bands in Pir, Gly and
PhA at 204–507 and 256–259 nm remain in the same po-
sition in all the chelates indicating that they are not af-
fected by metal chelation. Moreover, they may be attributed
Fig. 2. 1H NMR spectrum of piroxicam.
ArHs and three CH3 protons, respectively. Due to the lack
of solubility of Zn(II)-ternary chelates in different solvents,
1
render it difficult to carry out their H NMR spectra. The
results of the elemental analyses of ternary chelates are listed
in Table 1. The results are close to each other and they are
in the acceptable range of 0.5% error. It was seen from
Table 1 that ternary chelates of di- and trivalent transition
metals with Pir and Gly are formed with 1:2:2 ratio (metal
salts: Pir: Gly). The divalent metal chelates have the general
formula [M(H2L)2(Gly)2]·yH2O where M = Fe(II), Co(II),
Ni(II), Cu(II) and Zn(II) and y = 2 − 4; while Fe(III)-
ternary chelate has the formula [Fe(H2L)2(Gly)2]Cl·2H2O.
1.6
1.4
(g)
1.2
(a )= Piroxicam
(b)= Glycine
1
(c)= Fe(II)-Pir-Gly
(d)= Fe(III)-Pir-Gly
(e)= Co(II)-Pir-Gly
(f)= Ni(II)-Pir-Gly
(g)= Cu(II)-Pir-Gly
(h)= Zn(II)-Pir-Gly
0.8
(d)
(f)
0.6
0.4
0.2
0
(c)
(e)
(h)
(a)
(b)
200
250
300
350
400
Wavelength (nm)
Fig. 3. Absorption spectra of piroxicam and its ternary complexes with glycine in absolute ethanol.
450
500
550
600

G.G. Mohamed, N.E.A. El-Gamel / Spectrochimica Acta Part A 60 (2004) 3141–3154
3145
1.6
1.4
1.2
1
(a)= Piroxicam
(b)= Phenylalanine
(c)= Fe(II)-Pir-PhA
(d) = Fe(III)-Pir-PhA
(e)= Co(II)-Pir-PhA
(f)= Ni(II)-Pir-PhA
(g)= Cu(II)-Pir-PhA
(h)= Zn(II)-Pir-PhA
(g)
(e)
0.8
0.6
0.4
0.2
0
(c)
(d)
(f)
(h)
*
(a)
(b)
200
250
300
350
400
450
500
550
600
Wavelength (nm)
Fig. 4. Absorption spectra of piroxicam and its ternary complexes with dl-phenylalanine in absolute ethanol.
to ␲–␲* and n–␲* transition within the Pir, Gly or PhA
molecules.
The shoulder band observed at 291 nm in ethanol solvent
Figs. 3a and 4a may be assigned to n–␲* transition within
brations, respectively. The other series of weak bands be-
tween 3100 and 2800 cm−1 are related to (C–H) modes of
vibrations. After complexation, the full region is dominated
by two strong broad bands related to the stretching modes of
the water molecules. Some weak bands are located between
2000 and 1700 cm−1 and can be assigned to overtones of
the aromatic rings.
=
the C O group of the amide moiety in the free Pir or car-
boxylate of amino acids. This band is red shifted to 292, 293,
295 nm in case of Fe(II), Fe(III) and Ni(II) chelates, while
it disappeared in all the remaining chelates revealing the in-
In the wavenumber range 1700–1000 cm−1 some of the
most characteristic bands of these systems are found. The
=
volvement of the C O of amide group or carboxylate–O in
=
chelate formation [12].
so-called amide I band, which represents mainly the ν(C O)
The n–␲* transitions within the Pir molecule are over-
lapped with those of Gly and PhA molecules at λ =
360–370 nm so renders it difficult to attribute the blue or
red shift of these bands as a result of the involvement of
the pyridyl-N of Pir or amino group of Gly or PhA during
chelate formation (N → M) [12].
stretching mode, is seen as a very strong band at 1630 cm−1
,
with a weak shoulder at 1612 cm−1 in free Pir. In Pir com-
plexes, this band is shifted to higher or lower frequencies
or disappear (see Table 2), supporting the participation of
the carbonyl group of the Pir in the metal coordination [14].
This band appears broadened in most of the chelates by
the simultaneous appearance of the δ(H2O) vibration in the
same range, a fact which obstructs the clear visualization of
3.2. IR spectra and mode of bonding
=
the effective displacement of the ν(C O) band [9]. Another
band vibration ν(CN) + δ(NH) combination usually known
as amide III, can be assigned to the strong band seen at
1301 cm−1 in Pir, which is absent in the spectra of the com-
plexes, or it may be shifted and superimposed on any other
near-lying band. As it known, this band is very sensitive to
The careful inspection of the IR spectra of free Pir and its
ternary complexes, is based on some general references [13]
and made in comparison with other related molecules and
complexes. Table 2 shows the measured IR band positions
of the ternary chelates in order to facilitate the assignment
of these bands in the free ligands and their metal chelates.
Figs. 5 and 6 show the IR spectra of Pir and its ternary
chelates with Gly and PhA, respectively, at the wavenumber
=
the geometrical changes in the O C–N(H)–C moiety [15].
Since after complexation, the carbonyl group is involved in
coordination, such changes are, obviously, important in this
part of the Pir molecule.
range 4000–200 cm−1
.
The band located at 1572 cm−1 is assigned to the ν(C N)
The well-defined peaks at 3385 s and 3336 s cm−1 in the
=
stretching vibration of pyridyl nitrogen. This band disap-
spectrum of Pir are assigned to the ν(N–H) and ν(O–H) vi-

Table 2
IR assignment (4000–200 cm−1) of Pir ternary metal chelates with Gly and PhA
=
νasym(COO)
νsym(COO)
δNH2
ν(CONH)
ν(C N)
ρ(py)
νasym(SO2)
νsym(SO2)
ν(M–N)
ν(M–O)
ν(M–O) (Gly)
ν(M–O) (PhA)
ν(M–N) (PhA)
(PhA)
(Gly)
(Pir)
1586 s
1594 s
–
1412 s
1408 s
–
1502 s
1524 s
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
1630 s
dis
1602 m
dis
dis
dis
dis
dis
dis
dis
1572 m
dis
dis
dis
dis
dis
dis
dis
dis
dis
dis
dis
dis
623 s
673 m
670 w
659 w
672 w
658 w
673 m
670 w
650 w
650 w
670 m
666 w
656 w
1351 s
1325 m
1349 m
1326 w
1325 w
1331 w
1327 m
1328 w
1326 w
1326 w
1327 m
1333 m
1330 w
1040 m
1063 w
1045 w
1037 w
1061 w
1055 m
1065 m
1040 w
1038 w
1065 w
1063 m
1055 w
1048 w
Fe(II)-Pir-Gly
Fe(III)-Pir-Gly
Co(II)-Pir-Gly
Ni(II)-Pir-Gly
Cu(II)-Pir-Gly
Zn(II)-Pir-Gly
Fe(II)-Pir-PhA
Fe(III)-Pir-PhA
Co(II)-Pir-PhA
Ni(II)-Pir-PhA
Cu(II)-Pir-PhA
Zn(II)-Pir-PhA
1597 w
1562 s
1548 w
1584 br
1575 br
1587 br
1580 br
1605 m
1580 w
1588 br
1574 w
1575 w
1401 m
1429 m
1391 m
1401 s
1396 m
1402 w
1397 w
1400 w
1399 m
1400 m
1391 m
1397 w
1516 w
1524 w
1528 w
1518 m
1518 m
1517 m
1520 w
1525 m
1516 m
1516 m
1518 m
1514 w
570 w
578 w
570 s
568 w
566 m
569 w
573 w
576 w
573 w
570 w
568 w
566 w
375 w
381 w
386 w
376 m
374 w
379 m
358 w
363 w
357 w
372 m
375 w
357 w
410 w
336 w
454 w
338 w
333 w
355 w
–
–
–
–
–
–
–
–
433 w
410 w
430 w
433 w
437 w
425 w
331 w
334 w
332 w
337 w
324 w
313 w
dis
dis
1621 w
s: strong; w: weak; m: medium; br: broad; dis: disappear.

G.G. Mohamed, N.E.A. El-Gamel / Spectrochimica Acta Part A 60 (2004) 3141–3154
3147
Fig. 6. IR spectra (4000–200 cm−1) of Pir and PhA mixed ligand chelates:
(a) PhA, (b) Fe(II), (c) Fe(III), (d) Co(II), (e) Ni(II), (f) Cu(II) and (g)
Zn(II).
Fig. 5. IR spectra (4000–200 cm−1) of Pir and Gly mixed ligand chelates:
(a) Gly, (b) Fe(II), (c) Fe(III), (d) Co(II), (e) Ni(II), (f) Cu(II) and (g) Zn
(II).

3148
G.G. Mohamed, N.E.A. El-Gamel / Spectrochimica Acta Part A 60 (2004) 3141–3154
At the wavenumber 3500–3000 cm−1 region of the ternary
chelates of Pir, the overlap of the various ν(NH) vibra-
tions coupled in many cases with molecules of water of
hydration gives rise to very strong absorption. This pre-
vents the individual recognition of the various bands. The
band due to the in-plane deformation of the amino group
of Gly (δNH2) at 1524 cm−1 is slightly shifted to higher or
lower frequencies (1528–1516 cm−1) upon chelation indi-
cating non-participation of the nitrogen atom in bonding to
the metal ions. The shift to higher or lower wavenumbers
may be attributed to the participation of the NH2 group in
intramolecular hydrogen bond. The band due to δNH2 of
peared but it is still difficult to confirm the participation of
the pyridyl nitrogen as its band overlapped with those of
the carboxylate group of the amino acids or the amide II
stretching vibration band. Its participation is confirmed from
the band due to in-plane deformation ρ(py) located at 600
and 400 cm−1
.
The in-plane ring deformation (604 cm−1 in free pyri-
dine) is probably overlapped by the 623 cm−1. After com-
plexation, the band at 623 cm−1 disappears and a new band
at 673–650 cm−1 is found in the ternary chelates, as previ-
ously reported for pyridine complexes of divalent ions of the
first row transition metal series [16]. Detecting the shift of
the out-of-plane ρ(py) at 405 cm−1 is difficult because the
spectra are rich for the complexes.
dl-phenylalanine appeared as a maximum near 1502 cm−1
.
This band has been shifted to the extent 12–23 cm−1 in all
the complexes confirming coordination of the NH2 group to
the metal ions [19,20].
Two bands, located at 1351 and 1040 cm−1, are assigned
to the antisymmetric and symmetric stretching vibrations of
the SO2 group, respectively. Interestingly, these bands are
found in particularly the same position as in saccharin [17],
a molecule with a structure very similar to that of the ben-
zothiazine part of Pir. These two SO2 bands are shifted to
lower or higher frequencies in ternary complexes, in accor-
dance to the assignment of Cini et al. [8]. As the SO2 group
is not involved in metal binding, this shift to higher frequen-
cies must be related to important hydrogen bonding effects.
Another possible explanation for this shift may be due to
the electronic density changes on the sulfur atom and in the
ring after complex formation.
Most of the band shifts observed at the wavenumber
region 1150–994 cm−1 are in agreement with the struc-
tural changes observed in the molecular carbon skeleton
after complexation, which cause some important changes
in (C–C) bond lengths and also affect some of the C–O and
C–N bonds indirectly [6].
The ν(M–N) bands for the pyridyl nitrogen appeared in
the wavenumber range 566–573 cm−1 for the divalent and
at 576–578 cm−1 for the trivalent metal ion [16]. New peaks
of weak or medium intensity are observed in the wavenum-
ber range 357–386 cm−1 which are attributed to ν(M–O) vi-
brations of ternary chelates [21]. The band at 334 cm−1 is
assigned to the M–Cl vibration of Fe(III) ternary complex
with Pir and PhA [22]. The stretching vibration bands due to
ν(M–O) of amino acids (Gly and PhA) appeared in the region
of 454–313 cm−1, as reported for [Cu(Gly)2] and [Cu(ala)2]
complexes [23]. While the ν(M–N) bands [23] of the PhA
ternary chelates are observed in the region 410–437 cm−1
.
The vibrations of the sulphate ion in Fe(II)-ternary
chelates with PhA appears at 1160 and 629 cm−1. This in
association with conductance data indicate the uncoordi-
nated nature of sulphate group [24].
Therefore, it is concluded that from UV-Vis and IR spec-
tra that Pir behaves as neutral bidentate ligand coordinated
to the metal ions through amide–CO and pyridine-N. In ad-
dition, Gly is bonded to the metal ions through its depro-
tonated carboxylate group in unidentate manner, while the
amino group is remained unchanged in the ternary chelates.
In the case of dl-phenylalanine, it behaves as a uninega-
tively bidentate ligand where it binds to the central metal ions
through its deprotonated carboxylate group and its amino
group. Hence, these studies, IR and UV-Vis, give us use-
ful information’s about how Pir appear its effect with Gly
or PhA on metal ions present in the biological fluids in the
human body.
The bands between 840 and 732 cm−1 can be assigned
to δ(CH) and to ring modes, respectively. One group of in-
teresting bands of the free ligand in this region are those
located at 691 and 623 cm−1. The first of them may be the
so-called amide V band [(mainly out-of-plane δ(NH)]. The
second may be attributed to the δ(OCN) (amide IV) and the
δ(CO) out-of-plane (amide VI) modes as well as internal
pyridine modes. Both groups of bands change appreciably
after complexation. The Pir bands found at 938, 831 and
732 cm−1 also disappear or shifted to higher wavenumbers
after complexation. Some of them are surely related to com-
plicated skeletal modes involving vibrations of the –C(O)-
NH- portion of the molecule [9].
The bands at the wavenumber 1594–1586 and 1412–
1408 cm−1 regions, in the free amino acids; Gly or PhA,
are assigned to the antisymmetric and symmetric stretch-
ing vibrations of the carboxylate group, respectively. The
shift of these two bands to higher or lower frequencies
suggest the participation of –COOH group in complex for-
mation after deprotonation [18]. The values of band shift
3.3. Molar conductivity measurements
As seen from Table 1, the molar conductivity value of
Fe(III)-Pir-Gly is 130 ꢀ−1 cm2 mol−1. Furthermore the mo-
lar conductivity of the most of Pir-PhA chelates are found
to be 156, 115, 105, 120 and 135 ꢀ−1 cm2 mol−1 for Fe(II),
Co(II), Ni(II), Cu(II) and Zn(II)-chelates, respectively. It
is obvious from the data that these complexes are ionic in
nature and they are of the type 1:1 electrolytes [25]. On the
other hand; the remaining chelates have molar conductiv-
ꢂν (νas(COO)–νsym(COO)) are all about 143–205 cm−1
,
indicating that the carboxylate group in both Gly and PhA
are chelated in a unidentate manner to the metal ions [18].

G.G. Mohamed, N.E.A. El-Gamel / Spectrochimica Acta Part A 60 (2004) 3141–3154
3149
ity values ranged from 10.1 to 29.0 ꢀ−1 cm2 mol−1. These
values indicate the non-ionic nature of these chelates and
they are considered as non electrolytes [25]. Hence, the mo-
lar conductance measurements of the chelates confirm the
proposed general formulae of those chelates as suggested
depending upon the results of elemental analyses and IR
spectra.
strong interaction between the reactive sites of the or-
ganic compounds with nickel. The B values are less than
unity (0.52–0.76), suggesting a largely covalent bond be-
tween the organic ligand and nickel. The electronic spec-
tra of the ternary Co(II)-complexes give three bands at
(12.27–11.31) × 103 cm−1, (15.04–13.89) × 103 cm−1 and
at (17.59–16.34) × 103 cm−1 wavenumber regions, respec-
tively. The third region (18.18–26.06) × 103 cm−1 refers to
the charge transfer band. The bands observed are assigned
3.4. Magnetic susceptibility and electronic spectra
4
4
4
to the transitions T1g(F) → T2g(F)(ν1), T1g(F) →
4A2g(F)(ν2) and 4T1g(F) → T2g(P)(ν3), respectively, sug-
4
As further structural tools, magnetic and solid reflectance
spectral studies have been used to confirm the geometry
of the complexes. From the diffuse reflectance spectra it
is observed that, the ternary Fe(III)-chelates exhibit a band
at (21.93–21.14) × 103 cm−1, which may be assigned to
gesting that there is an octahedral geometry around Co(II)
ion [30,31]. The ratio ν3/ν1 = 1.14–1.58 is lower than the
expected for octahedral Co(II)-complexes (1.95–2.48) [32].
For calculating the Racah parameters, the following two
equations are used [39]:
6
the A1g → T2g (G) transition in octahedral geometry of
6
the complexes. The A1g
→
5T1g transition appears to
10Dq = 2ν1 − ν3 + 15B
be split into two bands at (12.42–11.90) × 103 cm−1 and
(8.98–17.61)×103 cm−1. The observed magnetic moments
of Fe(III) complexes are 5.7–5.92 B.M. Thus, the complexes
formed have the octahedral geometry involving d2sp3 hy-
bridization in Fe(III) ion [26].
1
B =
[−(ν1 − ν3) (−ν12 + −ν32 + ν1ν3)1/2
]
30
1
10Dq = (2ν2 − ν3) + 5B
3
The diffused reflectance spectra of mixed ligand com-
plexes of Fe(II) ion display two absorption bands at
1
B =
[7(ν3 − 2ν2) 3[81ν32 − 16ν2(ν2 − ν3)1/2
]
510
(12.20–11.63) × 103 cm−1 and (22.22–17.73) × 103 cm−1
The B parameter is a measure of the electron–electron repul-
sion term, which is lower in the complexes (600–850 cm−1
5
which are assigned to T2g
→
5Eg transition and charge
)
transfer, respectively [27]. The Fe(II) chelates exhibit mag-
netic moment values of 4.91–5.12 B.M., which are consis-
tent with a high spin octahedral geometry [28]. The Ni(II)-
mixed ligand complexes of Pir and Gly or PhA reported
herein are high spin with a room temperature magnetic
moment values of 2.86–3.40 B.M.; which are in the normal
range observed for octahedral Ni(II)-complexes [27]. This
indicates that, the mixed ligand complexes of Ni(II) are six
coordinate and probably octahedral [29].
than in free ion (985 cm−1), with B values in the 0.61–0.86
range. From the position of the bands and the calculated
Racah parameters, the chelates are octahedral with largely
covalent bonds between the organic ligands and the metal
ion [30]. The magnetic susceptibility measurements lie in
the 5.4–5.1 B.M. range (normal range for octahedral Co(II)-
complexes is 4.3–5.2 B.M.), is an indicative of octahedral
geometry [32].
The reflectance spectra of Cu(II)-ternary chelates with Pir
in the presence of Gly consist of a broad, low intensity shoul-
der band centered at 17.86×103 cm−1 that forms part of the
charge transfer band. The 2Eg and 2T2g states of the octahe-
dral copper(II) ion (d9) split under the influence of the tetrag-
onal distortion and the distortion can be such as to cause the
Their electronic spectra, in addition to show the ␲–␲*
and n–␲* bands of free ligands, display three bands, in the
solid reflectance spectra at:
ν1 : (12.63–11.61) × 103 cm−1 : 3A2g → T2g
3
3
ν2 : (15.77–14.64) × 103 cm−1 : 3A2g → T1g(F)
2
2
2
2
2
three transitions B1g → B2g; B1g → Eg and B1g
→
ν3 : (20.28–19.08) × 103 cm−1 : 3A2g → T1g(P)
3
2A1g to remain unresolved in the spectra [33]. It is concluded
that, all three transitions lie within the single broad envelope
centered at the same range previously mentioned. The mag-
netic moment of 2.0 B.M. falls within the range normally
observed for octahedral Cu(II)-complexes [34]. While the
Cu(II)-complexes of Pir ternary chelates in the presence of
PhA exhibit a broad band in the region 16.67 × 103 cm−1
The Racah parameters are calculated according to the fol-
lowing equations:
ν2 + ν3 − 3ν1
B =
15
1
{3ν2[25(ν3 − ν2)2 − 16ν1]2}1/2
assigned to 2Eg → T2g transition and broad band in the re-
2
B =
75
gion 14.71 × 103 cm−1 which is assigned to B1g → A1g
as well as a shoulder band in the range 17.61 × 103 cm−1
characteristic of a square planner geometry for Cu(II) com-
plexes with dx2−y2 ground state [35]. The magnetic moments
2
2
10Dq = ν1
The 10Dq values lie in the 11.61–12.63 × 103 cm−1 range,
again confirming the octahedral configuration of the Ni(II)
chelates [29]. The smaller B values (560–820 cm−1) com-
pared to the free metal ion (1080 cm−1) are due to the
of the Cu(II)-complexes are found to be 1.7 B.M., a dsp2 hy-
brid orbital being involved [35]. A moderately intense peak

3150
G.G. Mohamed, N.E.A. El-Gamel / Spectrochimica Acta Part A 60 (2004) 3141–3154
Fig. 8. X-ray diffraction pattern of Pir and PhA mixed ligand chelates:
(a) PhA, (b) Fe(II), (c) Fe(III), (d) Co(II), (e) Ni(II), (f) Cu(II) and (g)
Zn (II).
Fig. 7. X-ray diffraction pattern of Pir and Gly mixed ligand chelates: (a)
Gly, (b) Fe(II), (c) Fe(III), (d) Co(II), (e) Ni(II), (f) Cu(II) and (g) Zn (II).

G.G. Mohamed, N.E.A. El-Gamel / Spectrochimica Acta Part A 60 (2004) 3141–3154
3151
Table 3
Characteristic lines of X-ray powder diffraction of Gly and its ternary chelates with Pir
Compound
d (Å)
2θ
I/I0
Compound
d (Å)
2θ
5.67
I/I0
Glycine (Gly)
5.99
4.68
4.41
4.09
3.72
3.52
3.14
3.05
2.99
2.53
2.45
2.31
1.86
1.69
14.78
18.94
20.10
21.73
32.92
25.29
28.43
29.29
29.81
35.38
36.62
39.04
48.98
53.94
11.36
32.25
6.19
[Ni(II)(Pir)2(Gly)2]·4H2O
15.56
7.40
6.83
6.26
6.07
5.70
5.13
4.79
4.37
4.26
3.81
3.77
3.56
3.49
3.41
3.23
2.12
100
36
13
57
65
90
36
39
34
52
26
30
30
68
28
19
18
11.95
12.96
14.10
14.58
15.52
17.27
18.50
20.32
20.83
23.34
23.57
25.01
25.52
26.14
27.55
42.71
12.43
100.0
32.24
18.35
53.95
19.58
14.78
9.41
8.52
6.60
2.66
[Fe(II)(Pir)2(Gly)2]·4.5H2O
15.33
6.41
6.02
5.80
5.18
4.79
4.25
3.81
3.52
5.76
13.80
14.70
15.26
17.10
18.50
20.88
23.34
25.28
100
27
30
48
15
20
27
15
36
[Cu(II)(Pir)2(Gly)2]·1.5H2O
13.94
7.36
6.96
6.08
5.68
5.13
5.01
4.63
4.49
3.95
3.58
3.43
2.95
2.84
6.34
12.02
12.70
14.75
15.75
17.24
17.69
19.13
19.74
22.43
24.87
25.92
30.28
31.47
86
11
7
30
100
15
11
23
23
16
10
21
10
7
[Fe(II)(Pir)2(Gly)2]Cl·2H2O
8.08
7.60
6.08
5.51
5.27
5.06
4.68
4.38
4.23
4.12
4.06
3.83
3.80
3.44
3.34
3.13
3.02
2.97
10.93
11.63
14.54
16.06
16.79
17.49
18.92
20.20
20.95
21.54
21.86
23.18
23.38
25.84
26.60
28.43
29.50
30.04
27
38
63
76
71
76
38
37
37
31
92
50
83
50
38
100
35
21
[Zn(II)(Pir)2(Gly)2]·2H2O
15.43
7.44
6.41
6.10
5.81
4.80
4.36
4.25
3.80
3.54
3.42
5.72
11.89
13.80
14.50
15.24
18.50
20.33
20.87
23.40
25.10
26.00
100
29
38
51
91
29
22
38
27
56
20
[Co(II)(Pir)2(Gly)2]·4H2O
15.52
13.12
7.41
6.22
6.03
5.27
5.10
4.79
4.26
3.78
3.46
3.24
5.68
6.73
100
11
35
47
55
17
28
43
47
27
53
21
11.93
14.23
14.67
16.70
17.36
18.47
20.82
23.49
25.71
27.49

3152
G.G. Mohamed, N.E.A. El-Gamel / Spectrochimica Acta Part A 60 (2004) 3141–3154
Table 3 (Continued )
Compound
d (Å)
2θ
I/I0
Compound
d (Å)
2θ
I/I0
2.93
2.28
2.11
1.96
30.39
39.40
42.72
46.32
15
17
21
15
Table 4
Characteristic lines of X-ray powder diffraction of PhA and its ternary chelates with Pir
Compound
d (Å)
2θ
I/I0
Compound
d (Å)
2θ
5.74
I/I0
dl-Phenylalanine (PhA)
15.72
5.21
3.90
3.12
2.60
5.62
100
23
33
12
10
[Ni(II)(Pir)(PhA) (H2O)2]Cl
15.38
7.37
6.29
6.04
5.73
5.13
4.78
4.24
3.50
3.40
3.28
2.95
2.50
2.10
100
28
49
59
91
30
32
41
61
19
10
8
17.00
22.76
28.56
34.48
12.00
14.06
14.66
15.46
17.28
18.56
20.92
25.44
26.18
27.16
30.30
35.96
42.94
8
10
[Fe(II)(Pir)(PhA)(H2O)2]0.5SO4
15.40
6.13
6.04
5.78
5.14
4.91
4.80
4.26
3.51
3.38
3.25
5.72
14.44
14.66
15.32
17.22
18.06
18.46
20.84
25.38
26.28
27.40
100
27
50
50
20
16
39
36
29
18
11
[Cu(II)(Pir)(PhA)(H2O)2](Ac)·H2O
16.47
15.82
13.97
6.09
5.69
4.63
4.49
3.95
3.43
3.26
3.07
5.36
5.58
6.32
53
27
100
24
75
15
14
13
14
8
14.54
15.56
19.14
19.76
22.46
25.92
27.32
28.98
4
[Fe(III)(Pir)(PhA)(Cl)2]·H2O
–
–
–
[Zn(II)(Pir)(PhA)(H2O)2](Ac)·H2O
16.85
15.54
7.45
6.41
6.10
5.81
4.26
3.80
3.55
3.43
5.24
5.68
61
100
28
38
52
87
33
24
44
11.86
13.80
14.50
15.24
20.84
23.38
25.10
25.98
16
[Co(II)(Pir)(PhA)(H2O)2]Cl
15.49
6.37
6.04
5.77
5.13
4.25
3.80
3.51
3.48
2.55
2.1
5.70
13.88
14.66
15.34
17.26
20.86
23.38
25.34
25.54
35.14
43.02
100
14
16
27
15
18
15
17
12
11
7

G.G. Mohamed, N.E.A. El-Gamel / Spectrochimica Acta Part A 60 (2004) 3141–3154
3153
observed in the range (33.56–27.17) × 103 cm−1 is due to
ligand–metal charge transfer transition [36].
The interdistance spacing (d, Å) and relative intensity
((I/I0 × 100)) for the strongest lines characteristic for the
free ligands together with their ternary chelates are indicated
by bold and underline letters as shown in Tables 3 and 4;
and it can be considered as a finger print for these ternary
chelates.
In analogy with those described for Zn(II) complexes con-
taining N–O donor Schiff bases [37–39] and according to
the empirical formulae of these complexes, we proposed an
octahedral geometry for the mixed ligand Zn(II)-complexes
of Pir (as primary ligand) and Gly or PhA (as secondary lig-
ands) with two axial position occupied by the two glycine
molecules or water molecules in case of Pir mixed ligand
complexes with PhA.
3.6. Structural interpretation
The structure of the complexes was confirmed by the IR,
UV-Vis, magnetic, solid reflectance, molar conductance and
XRD analysis. The chelation is brought about by the pyri-
3.5. X-ray powder diffraction
=
dine nitrogen and C O of amide groups of Pir or by the
Figs. 7a and 8a show the X-ray powder diffraction pattern
of Gly and PhA, respectively. The values of 2θ, interplanar
distance (d, Å and (I/I0) × 100 are listed in Tables 3 and 4.
Form the obtained X-ray chart and interplanar distance (d,
Å) values, it is obvious that Gly exists as ␣-Gly form while
PhA exists as dl-phenylalanine form, in accordance with
the previously reported data [40,41]. The space group of Gly
(monoclinic P21/n (14)) and PhA (orthorhombic P212121
(19), are determined.
Figs. 7 and 8 show the X-ray powder diffraction spec-
tra of ternary chelates under study. Tables 3 and 4 illus-
trate the X-ray diffraction pattern for ternary chelates with
their characteristic d-spacing (Å), 2θ and relative intensity
(I/I0 × 100). The d-spacing (Å) and (I/I0 × 100) of these
ternary chelates are listed for identification of the phases.
XRD analysis for ternary chelates shows that the coordina-
tion of Pir alone or in the presence of Gly or PhA, to the
metal ions (Fe(II), Fe(III), Co(II), Ni(II), Cu(II) and Zn(II))
change the XRD pattern of the ligands. This means that the
metal ions are not fitted in the same phase of Pir, Gly or
PhA. Therefore, the non-similarity of XRD pattern between
the metal ions ternary chelates suggests that these chelates
have a different phase structures than the Pir, Gly and PhA
ligands.
carboxylate and/or the amino groups of amino acids (Gly
or PhA). The valence of the metal ions in the chelates is
neutralized by displacement of carboxylate proton of amino
acids. From the reflectance spectra and magnetic moment
measurements, the geometrical structure of the chelates were
proposed and found to be octahedral, or square planar.
As a general conclusion, Pir behaves as neutral bidentate
ligands in all the chelates. While, Gly behaves as a monoba-
sic ligand through the carboxylate group. Whereas, PhA be-
haves as a dibasic ligand through the carboxylate and amino
groups. The structure of the chelates can be given as follows:
• Suggested structural formulae of Pir ternary chelates with
Gly
In addition, on comparing the XRD spectra of the ternary
chelates with the XRD spectra of the free ligands, indicate
the crystallinity of the ternary chelates under study, except
Fe(III)-Pir-PhA chelates, it can considered as amorphous
structure.
• Suggested structural formulae of Pir ternary chelates with
PhA

3154
G.G. Mohamed, N.E.A. El-Gamel / Spectrochimica Acta Part A 60 (2004) 3141–3154
[22] F.H. Urena, A.L.P. Chamorro, M.N.M. Carreterro, J.M. Amigo, V.
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