Derivatives of phosphate Schiff base transition metal complexes: synthesis, studies and biological activity.

Article abstract of DOI:10.1016/S1386-1425(03)00216-6

We report the synthesis and structural characterization of series of tetra- and hexacoordinate metal chelate complexes of phosphate Schiff base ligands having the general composition LMX(n).H(2)O and L(2)MX(n) (L=phosphate Schiff base ligand; M=Ag(+), Mn(

Full text of DOI:10.1016/S1386-1425(03)00216-6

Spectrochimica Acta Part A 60 (2004) 271–277
Derivatives of phosphate Schiff base transition metal complexes:
synthesis, studies and biological activity
Z.H. Abd El-Wahab∗, M.R. El-Sarrag
Chemistry Department, Faculty of Science (Girl’s), Al-Azhar University Nasr-City, P.O. Box 11754 Cairo, Egypt
Received 9 December 2002; received in revised form 8 May 2003; accepted 9 May 2003
Abstract
We report the synthesis and structural characterization of series of tetra- and hexacoordinate metal chelate complexes of phosphate Schiff
base ligands having the general composition LMXn·H2O and L2MXn (L = phosphate Schiff base ligand; M = Ag+, Mn2+, Cu2+, Zn2+, Cd2+
,
P
Hg2+, or Fe3+ and X = NO3−, Br− or Cl−). The structure of the prepared compounds was investigated using elemental analysis, IR, 1H and 31
NMR, UV–vis, mass spectra, solid reflectance, magnetic susceptibility and conductance measurements as well as conductometric titration. In
all the complexes studied, the ligands act as a chelate ligand with coordination involving the phosphate–O-atom and the azomethine–N-atom.
IR, solid reflectance spectra and magnetic moment measurement are used to infer the structure and to illustrate the coordination capacity
of ligand. IR spectra show the presence of coordinated nitrate and water molecule, the magnetic moments of all complexes show normal
magnetic behavior and the electronic spectra of the metal complexes indicate a tetra- and octahedral structure for Mn2+, octahedral structure of
Fe3+ and both square-planar and distorted octahedral structure for Cu2+ complexes. Antimicrobial activity of the ligands and their complexes
were tested using the disc diffusion method and the chosen strains include Staphylococcus aureus, Pseudomonas aereuguinosa, Klebsiella
penumoniae, Escherichia coli, Microsporum canis, Trichophyton mentagrophyte and Trichophyton rubrum. Some known antibiotics are
included for the sake of comparison and the chosen antibiotic are Amikacin, Doxycllin, Augmantin, Sulperazon, Unasyn, Septrin, Cefobid,
Ampicillin, Nitrofurantion, Traivid and Erythromycin.
© 2003 Elsevier B.V. All rights reserved.
Keywords: Phosphate Schiff base ligands; Transition metal complexes; Spectroscopic techniques; Magnetic measurements; Biological activity
1. -Introduction
spectroscopic features is perhaps the most important step
to understand the structure and behavior of these biological
systems. Schiff base metal complexes attract considerable
interest and occupy an important role in the development of
the chemistry of chelate systems [6,7] due to the fact that es-
pecially these with N2O2 tetradentate ligands, such systems
closely resemble metallo-proteins. Survey of the literature
reveals an excellent work devoted to synthesis and charac-
terization of many metal complexes of Schiff base [8–13],
furthermore the coordination compounds of phosphonic
acid and their esters with transition metal ions have been
the subject of several studies due to the fact that complexes
of such compounds exhibit biological activity [14–17]. The
present paper deals with the preparation and characteriza-
tion of phosphate Schiff base derivatives followed by study-
ing their complexation with di-and trivalent transition metal
ions which have been the subject of several studies due to
the fact that these ligands and their metal complexes exhibit
different biological activity and very industrial applications.
The transition metal complexes having oxygen and ni-
trogen donor Schiff bases possess unusual configuration,
structural lability and are sensitive to molecular environ-
ment [1]. The environment around the metal center ‘as
coordination geometry, number of coordinated ligands and
their donor group’ is the key factor for metalloprotein to
carry out a specific physiological function [2]. About 20
Zinc enzymes are known in which Zinc is generally tetrahe-
drally four coordinate and bonded to hard donor atoms such
as nitrogen or oxygen [3]. Manganese plays an important
role in several biological redox-active system [4], a number
of copper proteins including enzymes have been reported
and proteins containing iron participate in oxygen transport
[5]. The preparation of model complexes having similar
∗
Corresponding author.
E-mail address: zhabdelwahab@hotmail.com (Z.H.A. El-Wahab).
1386-1425/$ – see front matter © 2003 Elsevier B.V. All rights reserved.
doi:10.1016/S1386-1425(03)00216-6

272
Z.H.A. El-Wahab, M.R. El-Sarrag / Spectrochimica Acta Part A 60 (2004) 271–277
Table 1
Analytical and physical data of bidentate phosphate Schiff base ligands (Ia,b
)
Compd. No.
Molecular formula (M.wt)
Colour
m.p.(◦C)
Analysis% found (calcd.)
N
P
Ia
Ib
C25H20NPO3 (413)
Yellowish green
Pale yellow
146
148
2.90 (3.39)
2.70 (3.16)
7.62 (7.51)
7.86 (7.00)
C
26H22NPO4 (443)
2. Experimental
(IIa–l) and (IIIa–j). The microanalytical data for complex
derivatives are listed in Tables 2 and 3.
2.1. Preparation of phosphate Schiff base ‘ligand’
2.3. Antimicrobial activity
At first, two Schiff base derivatives were prepared by
literature method [18] via condensation of aniline with
benzaldehyde and p-methoxybenzaldehyde, respectively.
Secondly, the phosphate Schiff base derivatives ‘ligands’
(Ia,b) were prepared by direct reaction of Schiff base with
diphenyl chlorophosphate in 1:1 molar ratio in presence of
tertiary amine to absorb the liberated hydrogen chloride us-
ing acetonitrile as solvent. In a typical experiment, a solution
of diphenyl chlorophosphate (5.2 ml, 0.025 mmol) in 25 ml
acetonitrile was added dropwise to a well stirred solution of
Schiff base (4.53 g of benzalaniline; or 5.28 g of p-methoxy
benzalaniline; 0.025 mmol) in 25 ml acetonitrile containing
triethylamine (3.5 ml, 0.025 mmol). After complete addi-
tion, the reaction mixture was heated under reflux for 2 h, the
formed solid ‘triethylaminhydrochloride’ was filtered and
the filtrate was evaporated in vacuum. The obtained solid
(Ia,b) gave analytical data which are summarized in Table 1.
The phosphate Schiff base ‘ligands’ (Ia,b) and their metal
complex derivatives (IIa–l) and (IIIa–j) were evaluated for
their antibacterial activity against Klebsiella penumoniae,
Escherichia coli, Pseudomonas aereuguinosa and Staphylo-
coccus aureus and also for their antifungal activity against
Trichophyton mentogrophrtes, Microsporum canis and Tri-
chophyton rubrum using the disc diffusion method [19,20].
Moreover some of known antibiotic were evaluated for their
antibacterial activity as well as phosphate derivatives and
some comparison were discussed. The chosen antibiotic are
Amikacin, Doxycllin, Augmantin, Sulperazon, Unasyn, Sep-
trin, Cefobid, Ampicillin, Nitrofurantion, Traivid and Ery-
thromycin. The obtained data are collected in Tables 4–6.
2.4. Physical measurements
The elemental C, H and N analysis were carried at micro-
analytical laboratory of Cairo university, phosphorus anal-
ysis were determined gravimetrically by Voy method [21],
metal contents were determined volumetrically by titration
against standard EDTA after complete decomposition of
the complexes with nitric and perchloric acids in a kjeldahl
flask [22]. IR spectra were recorded on a Perkin–Elmer
FT-IR type 1650 spectrophotometer with KBr disc. Mass
spectra were performed by Hewlett-Packard mass spec-
2.2. Preparation of metal complexes
For the preparation of metal complexes, a hot ethanolic
solution of metal halide or nitrate was added dropwise to
ethanolic solution of phosphate Schiff base derivatives (Ia,b
in 1:1 and 1:2 molar ratio (M:L), respectively and the result-
ing solution was refluxed for 2 h. After evaporation of the
solvent, the colored solid obtained was recrystallised to give
)
Table 2
Analytical and physical data of phosphate Schiff base complexes in 1:1 molar ratio
Compd. No.
Molecular formula (M.wt)
Colour
m.p. (◦C)
Analysis% found (calcd.)
µeff B.M.
P
N
M
IIa
IIb
IIc
IId
IIe
IIf
IIg
IIh
IIi
C25H20NPO3 Cl2Hg (684.59)
C25H20NPO3 Cl2 Cd (596.41)
Grey
Greenish blue
Green
Greenish black
Greenish grey
White
Reddish brown
Reddish brown
Pale green
Green
151
299
124
125
121
>330
147
297
120
110
4.33 (4.53)
4.27 (5.20)
6.95 (5.16)
4.80 (5.75)
4.33 (4.86)
6.03 (5.22)
4.20 (4.34)
4.46 (4.95)
5.32 (5.37)
5.70 (5.45)
4.47 (4.64)
5.58 (4.97)
2.10 (2.05)
1.80 (2.35)
5.20 (466)
2.50 (2.60)
2.10 (2.19)
2.15 (2.36)
2.10 (1.96)
2.30 (2.23)
2.80 (2.42)
3.00 (2.46)
2.80 (2.10)
2.42 (2.25)
28.70 (29.30)
18.81 (18.85)
Diamag.
Diamag.
Diamag.
5.46
Diamag.
5.82
Diamag.
Diamag.
2.03
C25
H22N2PO7 Ag (600.87)
C
25H20NPO3 Cl2 Mn (538.94)
10.37 (10.19)
10.00 (10.25)
8.76 (9.41)
27.42 (28.07)
18.91 (17.95)
10.14 (11.00)
8.73 (9.66)
C25
C25
C26
C26
H20NPO3 Br2 Zn (638.19)
H21NPO3 Cl3 Fe (593.35)
H22NPO4 Cl2 Hg (714.59)
H22NPO4 Cl2 Cd (626.41)
C26H22NPO4 Cl2 Cu (577.55)
C26H22NPO4 Cl2 Mn (568.94)
IIj
IIk
IIl
5.54
Diamag.
5.85
C
26H22NPO4 Br2 Zn (668.19)
Black
Yellow
154
>330
8.64 (9.79)
9.20 (8.96)
C26H24NPO5 Cl3 Fe (623.35)

Z.H.A. El-Wahab, M.R. El-Sarrag / Spectrochimica Acta Part A 60 (2004) 271–277
273
Table 3
Analytical and physical data of phosphate Schiff base complexes in 1:2 molar ratio
Compd. No.
Molecular formula (M.wt)
Colour
m.p. (◦C)
Analysis% found (calcd.)
µeff B.M.
P
N
M
IIIa
IIIb
IIIc
IIId
IIIe
IIIf
IIIg
IIIh
IIIi
IIIj
C
C50
C50
50H40N2P2O6 Cl2 Cd (1009.41)
Blue
167
158
151
122
147
164
120
164
156
>330
6.11 (6.14)
6.08 (6.45)
7.44 (6.51)
6.95 (5.90)
5.37 (5.36)
5.95 (5.80)
6.09 (6.08)
6.85 (6.13)
5.89 (5.58)
6.57 (5.91)
3.00 (2.77)
2.40 (2.91)
3.00 (2.94)
2.58 (2.66)
2.50 (2.42)
3.70 (2.62)
2.20 (2.74)
2.90 (2.77)
3.30 (2.52)
3.11 (2.67)
10.95 (11.14)
5.65 (6.62)
5.82 (5.77)
5.48 (6.22)
17.27 (17.33)
11.47 (10.51)
5.80 (6.23)
5.12 (5.43)
6.76 (5.88)
4.77 (5.33)
Diamag.
1.80
5.16
Diamag.
Diamag.
Diamag.
1.87
6.03
Diamag.
5.95
H
H
40N2P2O6 Cl2 Cu (960.55)
40N2P2O6 Cl2Mn (951.94)
Greenish black
Reddish brown
Pale brown
Reddish brown
Reddish brown
Green
Green
Dark green
White
C
50H40N2P2O6 Br2 Zn (1051.19)
C52
C52
C52
H44N2P2O8 Cl2 Hg (1157.59)
H44N2P2O8 Cl2 Cd (1069.41)
H44N2P2O8 Cl2 Cu (1020.55)
C52H44N2P2O8 Cl2Mn (1011.94)
C52 44N2P2O8 Br2 Zn (1111.19)
C52H44N2P2O8 Cl3 Fe (1048.35)
H
trometer model MS 5988, H and 31P NMR spectra were
performed at the microanalytical center at Cairo University.
UV–vis spectra were performed by Perkin–Elmer Lambda
20 spectrophotometer at Al-Azhar University. Magnetic
susceptibilities measurements were measured by the Gouy
method at room temperature using an oxford faraday mag-
netometer at Qanal University. The solid reflectance spectra
were measured on a shimadzu 3101 pc spectrophotome-
ter at Cairo University. The conductmetric titrations was
carried out using engineered system of designs USA and
the biological screening was carried out at microbiology
laboratory, Bab Al-sheria University hospital, Al-Azhar
University.
1
Table 5
Antifungal activity of some phosphate Schiff base metal complexes
Compd.
No.
Fungi
Microsporum
canis
Trichophyton
mentagrophyte
Trichophyton
rubrum
IIa
IIb
IIg
IIh
IIi
R
++
+
+
++
++
++++
R
+++
++
+++
R
++
++
R
IIj
R
R
R
IIIa
IIIj
++
++
+++
R
R
R
Table 4
3. Results and discussion
Antibacterial activity of phosphate Schiff base derivatives and their metal
complexes
The treatment of diphenyl chlorophosphate with benza-
laniline and p-methoxybenzaniline, respectively led to the
replacement of azomethine proton giving the correspond-
ing phosphate Schiff base derivatives (Ia,b) which have two
donor sites, nitrogen and oxygen atoms, and so, they may
function as bidentate ligand (Fig. 1).
Compd. Gram positive
No.
Gram negative
Staphylococcus Pseudomonas Klebsiella
Escherichia
coli
aureus
aereuguinosa penumoniae
Ia
R
R
R
++
+++
R
R
R
R
R
++
++
R
R
R
+
++
R
Ib
R
IIa
IIb
IId
IIe
IIf
IIg
IIh
IIi
++++
++
R
+
+++
3.1. Characterization of phosphate Schiff base ligands
R
R
+
R
R
R
R
++
+++
R
Structure elucidation of the prepared compounds (Ia,b
)
+++
++
+
+
was accomplished on the bases of elemental analysis
++
++
R
1
(Table 1), IR, H and 31P NMR, Mass and UV–vis. Spec-
troscopic data.
IIj
R
R
R
(1) The analytical data of the isolated compounds (Ia,b
have been given in Table 1 which are in good agreement
with the proposed structure.
)
IIk
IIl
R
R
R
R
R
R
R
R
R
R
R
R
R
R
+
+
R
R
R
IIIa
IIIb
IIIc
IIIf
IIIg
IIIh
IIIi
IIIj
+
+
+++
++
+
++
+
R
++
+
R
R
R
R
R
R
R
R
R
++
+
R, Resistance; +++, Highly active; +, Less active; ++++, Very active;
Fig. 1. Phosphate Schiff base ligands (Ia,b).
++, Moderate active.

274
Z.H.A. El-Wahab, M.R. El-Sarrag / Spectrochimica Acta Part A 60 (2004) 271–277
Table 6
Antibacterial activity of some known antibiotics
Antibiotic name
Cocci (gram positive)
Bacilli (gram negative)
Staphylococcus aureus
Pseudomonas aereuguinosa
Klebsiella penumoniae
Escherichia coli
A mikacin
Doxycllin
Augmantin
Sulperazon
Unasyn
R
+++
R
R
+++
+++
+++
+++
R
++
R
+++
+++
+++
+++
R
+++
+++
R
R
++
R
R
Septrin
Cefobid
R
R
++
R
R
Ampicillin
Nitrofurantion
Traivid
R
++
R
++
+++
R
+++
+++
R
R
R
R
R
+++
R
Erythromycin
+++
(2) IR spectra showed the characteristic stretching vibra-
In the IR spectra of the free ligands (Ia,b), the band cen-
tered around (1673–1614 cm−1) and (1279–1220 cm−1
which characteristic for νC and νP O, respectively are
tions νC and νP O at (1673–1614 cm−1) and (1279–1220
)
=
=
N
cm−1), respectively [8,23].
=
=
N
1
(3) The H NMR spectra were used to substantiate the
shifted to a lower frequencies at (1640–1574 cm−1) and
(1249–1074 cm−1) upon coordination to transition metals
[8,23] with the appearance of other modes of vibrations
at (565–493 cm−1) and (477–414 cm−1) corresponding to
νM–N and νM–O [23,27] which are absent in the free lig-
and spectra. This confirms the involvement of azomethine
nitrogen and phosphate oxygen in complex formation. For
the nitrato complex compound (IIc) the band observed at
proposed structures (Ia,b), thus 1H NMR spectra showed that
the characteristic azomethine proton signal for shift bases at
δ = 8.6 ppm [8,9] had disappeared. Also the spectra for the
compounds (Ia,b) in DMSO-d6 solution showed the aromatic
protons signal at 7.2–7.1 ppm regions and a signal at 3.9
ppm region for Ib only due to the presence of the methoxy
group [9]. 31P NMR spectra for compound Ib show a signal
at δ = −11.6 due to the non bonding electrons on oxygen
phosphate group [24].
1491, 1384 and 1072 cm−1 is due to νN O, νasy NO and νsy
=
2
, the frequency difference (107 cm−1) is an agreement
NO2
(4) The mass spectra for the compounds (Ia,b) were
characterized by a peak corresponding to Schiff base frag-
mentation (M -233), the mass spectrum of the ligand Ia
show intense peak at m/e 180 (0.54%) corresponding to
Ph-c+=N-Ph ion and the mole peak at m/e 412.4 (0.26%)
(calculated 413). For the ligand Ib its mass spectrum is
characterized by i+ntense peak at m/e 233 (4.3%) corre-
PhNC+C6H4OCH3 ion and an intense peak at m/e 250
(47.1%) corresponding to (PhO)2 P (O) (OH). Intense peak
of this type is very common in phenyl–phosphorus com-
pounds containing more than one phenyl group attached to
the phosphorus atom [25].
with the unidentate coordination mode of the nitrate anion
[28,29]. A very broad band at about 3300–3446 cm−1 is
present in the spectra of the complexes IIc,f,l. The presence
of this broad band is associated with coordinated and/or sol-
vated water molecule [30,31]. The presence of coordinated
water in this complexes has been inferred on the basis of a
medium intensity band at 728–777 cm−1 (OH-rocking) [31].
The other stretching vibration in the ligand are much less
affected by complex formation indicating that the ligand be-
have as bidentate chelating ligand and both the azomethine
nitrogen and phosphate oxygen are the two sites of coordi-
nation. The data collected in Table 7.
=
sponding to O P (OPh)2 ion, m/e 210 (0.6%) due to
1H-NMR spectra for the complex derivatives (IIb,e,h,k
)
(5) The UV–vis spectra of phosphate Schiff-base ligands
(Ia,b) in DMF solution show two intense bands in the region
200–400 at 265 and 294 nm can be assigned to ␲–␲* and
n–␲* transition over the whole conjugated system [26].
and (IIIa,f,i) show signal at 7–7.4 ppm due to aromatic pro-
tons and a signal at 3.3–3.9 ppm due to the methoxy pro-
tons for compounds (IIk,h) and (IIIf,i) [8,23], see Table 8.
Also, the signal given by 31P nucleus in the NMR spectra
appears at δ = −11.6 and −11.7 for compounds IIh and IIIf.
The significance of this negative chemical shift than in the
reference compound is due to that the phosphorus nucleus
is more effectively shielded by the electron in the complex
compounds than in the reference (85% phosphoric acid).
3.2. Characterization of phosphate Schiff base metal
complexes
The reaction of phosphate derivatives (Ia,b) with metal
halide or nitrate led to the formation of (IIa–l) and (IIIa–j
)
derivatives. The elemental analysis were satisfactory and
show that the complexes have a ligand-to-metal ratio of 1:1
and 2:1. A comparison of the spectra of the free ligands
(Ia,b) with those of the metal complexes has been carried
out to investigate the mode of bonding of the ligands.
3.3. Determination the composition of the metal complexes
The stoichiometry of the metal complexes is confirmed
by conductometric titration of each of the metal ions and
Schiff base ligands in ethanol medium. The experimental

Z.H.A. El-Wahab, M.R. El-Sarrag / Spectrochimica Acta Part A 60 (2004) 271–277
275
Table 7
nature [33], accordingly the halide ions or nitrate group con-
tribute to the coordination sphere in the complexes under in-
vestigation except the Fe3+ complex compound IIIj which
its value corresponding to 1:1 electrolyte [28]. Moreover,
the composition of metal complexes was determined using
spectroscopic studies as the molar ratio method [34]. Cu2+
complexes were chosen as example of metal complexes un-
der investigation. A series of 2 ml solution was prepared
in which the Cu2+ ion concentration was kept constant at
1×10−3 M while that of the ligand was regularly varied
from 0.2×10−3 to 2.2×10−3 M in ethanol using the same
concentration of the ligand present in the examined solution
as a blank. A plot of the absorbance as a function of molar
ratio of [lig.]/[Cu2+], one obtains straight lines, each two
interesting at a certain ratio indicating the formation of 1:1
and 1:2 metal ligand species. This is an agreement with all
above results.
Characteristic infrared stretching vibrations (cm−1) of phosphate Schiff
base metal complexes
Compd. νC
No.
νP
νM–N νM–O
=
=
O
N
Free Coord. Shift Free Coord. Shift
IIa
IIb
IIc
IId
IIe
IIf
1614 1575
1575
39
39
23
23
25
23
1279 1136
1117
143
62
59
57
30
85
493
493
517
519
519
503
433
430
414
414
438
430
1591
1591
1589
1591
1220
1222
1249
1194
IIg
IIh
IIi
IIj
IIk
IIl
1673 1592
1615
81
58
84
78
35
82
1220 1204
1206
16
14
2
15
16
20
518
505
505
505
518
502
480
477
448
446
414
430
1589
1595
1638
1591
1218
1205
1204
1200
IIIa
IIIb
IIIc
IIId
1614 1574
1589
40
25
39
49
1279 1134
1219
145
60
140
60
565
544
564
544
436
438
438
414
3.4. Magnetic susceptibility and electronic spectra
measurements
1575
1565
1139
1219
A comparison of the electronic spectra of the free ligands
with those of the corresponding metal complexes show some
shift were detected, this can be considered as evidence for
the complex formation, the data were collected in Table 9.
Additionally the solid reflectance spectra of metal com-
plexes show different bands at different wavelengths each
one is corresponding to certain transition which suggests the
geometry of the complex compounds. Table 10 show the
different assignment of the complex compounds.
IIIe
IIIf
IIIg
IIIh
IIIi
IIIj
1673 1591
1590
82
83
84
35
37
82
1220 1204
1203
16
17
16
15
16
18
545
547
521
505
505
527
415
416
417
417
416
419
1589
1638
1636
1591
1204
1205
1204
1202
procedure involved the titration of 25 ml of 1×10−3 M of
The magnetic moment values of Mn2+ complexes un-
der study are found to be 5.16–6.03 B.M. The reflectance
data of Mn2+ complexes IId and IIj show the observed
metal ion solution with increasing volume of 1×10−3
M
of ligand solution with continuous magnetic stirring. The
conductivity values were corrected for the effect of dilution
during the titration then were plotted versus the milliliters
of reagent added and the least square equation is applied
[32]. The resulting curves are smooth straight lines for all
the points and the well defined breaks are coincident with
the stoichometric ratio of complexes formed in solution and
the results are in a good agreement with 1:1 and 2:1 molar
ratio suggested for these complexes. The low molar con-
ductance value of the isolated complexes measured in DMF
solution at room temperature suggest their nonelectrolytic
4
bands at 12 150–19 305 cm−1 attributable to 6A1→ T1,
6A1→ T2 (G) and 6A1→ E transition, respectively sug-
gest a tetrahedral stereochemistry for these complexes [35].
While, for compounds IIIc and IIIh, the observed bands
4
4
at 12 165–19 569 cm−1 due to the transition A1g→ T1g,
6
4
6A1g→ T2g (G) and A1g→ Eg suggest high spin octahe-
dral geometry around the metal ion [36–38].The magnetic
moment values of Fe3+ complexes IIf, IIl and IIIj are
found to be 5.82–5.95 B.M. indicating it to be high-spin
type paramagnetic, it lies within the octahedral range which
4
6
4
Table 8
1H-NMR spectra data of diamagnetism phosphate Schiff base metal com-
plexes
Table 9
The UV–vis, spectra data of the phosphate Schiff base metal complexes
Compd. No.
Chemical shifts δ in ppm
Compd. No.
␲→␲*
n→␲*
Compd. No.
␲→␲*
n→␲*
Ar
–OCH3
IIa
IIb
IIc
IId
IIe
IIf
IIg
IIh
266
267
263
267
261
261
269
263
294
294
–
294
294
–
IIi
IIj
266
266
267
262
269
–
293
293
–
297
247
293
IIb
IIe
7.1–7.3
7–7.4
–
–
IIk
IIl
IIIa
IIIb
IIIf
IIh
IIk
IIIa
IIIf
IIIj
7.1–7.4
7–7.3
7.1–7.3
7–7.4
3.9
3.8
–
3.8
3.3
293
293
269
7–7.3

276
Z.H.A. El-Wahab, M.R. El-Sarrag / Spectrochimica Acta Part A 60 (2004) 271–277
for Cu2+ complex IIi exhibits three absorption bands from
Table 10
Significant solid reflectance data of Schiff base phosphate metal complexes
12 128–19 361 cm−1 due to the transition.
2B1→ B2, 2B1→ E and charge transfer, respectively cor-
responding to square-planar configuration [33,39]. Addition-
ally, the electronic spectrum for Cu2+ complexes IIIb and
IIIg show the absorption bands in the region 12 453–19 569
2
2
Complex compound
Peak position
(cm−1
Assignment
)
6A1→ T1
4
IId
IIf
C25H20NPO3 Cl2 Mn
12 150
17 528
19 305
4
6A1→ T2 (G)
4
6A1→ E
2
2
2
2
cm−1 due to B1g→ B2g, B1g→ Eg and charge transfer
transition suggesting a distorted octahedral geometry for
these compounds [40]. Zn2+, Hg2+ and Cd2+ complexes are
diamagnetic as expected for d10 system, their complexes are
four- as well as six-coordinated as inferred from elemental
analysis and spectral data.
6A1g→ T1g
4
C25H22NPO4 Cl3 Fe
12 845
16 051
17 559
19 685
4
6A1g→ T2g (G)
4
6A1g→ Eg
6A1g→ T2g (D)
4
2B1g→ B2g
2
IIi
IIj
IIl
C26
H
22NPO4 Cl2 Cu
12 128
15 987
19 361
2
2B1g→ Eg
Charge transfer
4. Conclusion
6A1→ T1
4
C
26H22NPO4 Cl2 Mn
12 845
17 730
19 305
On the bases of the presented results we suggest that
the phosphate Schiff-base ligand coordinate to metal
4
6A1→ T2 (G)
4
6A1→ E
ions through the N,O system to give octahedral Fe3+
,
square-planar and distorted octahedral Cu2+, tetrahedral and
octahedral Mn2+ and octahedral Cd2+, Zn2+ and Hg2+ envi-
ronment around the metal ion anchor depending on the molar
ratio of metal to ligand in the reaction and hence the struc-
ture of phosphate Schiff base metal ions is given in Fig. 2.
4
C26H24NPO5 Cl3 Fe
12 903
15 974
17 550
19 627
6A1g→ T1g
4
6A1g→ T2g (G)
4
6A1g→ Eg
6A1g→ T2g (D)
4
2
IIIb
IIIc
IIIg
IIIh
IIIj
C50H40N2P2O6 Cl2 Cu
12 812
15 974
19 550
2B1g→ B2g
2
2B1g→ Eg
4.1. Evaluation of biological activity
Charge transfer
4
C50H40N2P2O6 Cl2 Mn
12 224
14 577
18 814
6A1g→ T1g
The question about the involvement of metal ligand com-
plexes in medical treatment are of special interest. To as-
sess the biological potential of the synthesized compounds,
the phosphate Schiff base ligands and their metal complexes
were tested against the selected bacteria and fungi. The an-
timicrobial data were collected in Tables 4 and 5. The syn-
thesized compounds were found to be possess remarkable
bactericidal and fungicidal properties, it is however interest-
ing that the biological activity gets enhanced on undergoing
complexation with the metal ions.
From structure point of view of the prepared compounds
with their effects on microbial tested, it is clear that forma-
tion of the chelate derivatives in 1:2 molar ratio (M:L) some-
times increase the biological activity as appeared from the
Mn2+ complexes IId and IIIc and Fe3+ complexes IIl and
IIIj. So the enhanced activities of the metal complex deriva-
tives compared to the free ligands may be due to the increase
in the number of phosphate group around the central metal
atom arising from chelation in 1:2 molar ratio (M:L) and
hence, the central metal atom was not only the responsible
for biological activity because some metal complexes are
enhanced the activity and other reduced this activity with
respect to the parent ligands.
4
6A1g→ T2g (G)
4
6A1g→ Eg
2
C
52H44N2P2O8 Cl2 Cu
12 453
15 060
19 569
2B1g→ B2g
2
2B1g→ Eg
Charge transfer
4
C52
H
44N2P2O8 Cl2 Mn
12 165
12 437
19 569
6A1g→ T1g
4
6A1g→ T2g (G)
6A1g→ Eg
4
4
C52H44N2P2O8 Cl3 Fe
12 642
16 012
17 543
19 474
6A1g→ T1g
6A1g→ T2g (G)
4
4
6A1g→ Eg
4
6A1g→ T2g (D)
very close to spin only value of 5.90 B.M. as the ground
term is A1g and thus supports octahedral stereochemistry
6
its reflectance spectra shows weak bands and are of low in-
tensity in the region 12 642–19 685 cm−1 may be assigned
to transition 6A1g→ T1g, 6A1g→ T2g (G), 6A1g→ Eg and
4
4
4
6A1g→ T2g (D) transition [27,33,38]. The magnetic mo-
Finally, to complete the evaluation of biological activity
of the synthesized compounds, some comparison with the
known antibiotic were performed and the data are collected
in Table 6. This table shows that the effect of Hg2+ com-
plex IIa against gram positive bacteria is greater than the
4
ments of Cu2+ complexes general range from 1.80–2.03
B.M. No absorption band is observed below 10 000 cm−1
in any complex under study which rules out the possibility
of tetrahedral geometry [33,39]. The electronic spectrum

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