Metal complexes of phosphorus compounds including indigoid structure: Synthesis, characterization, and biological study

Article abstract of DOI:10.1080/10426500802145049

Interaction of hexachlorocyclodiphosph(V)azanes, (I_a-h) with 5,5′ indigodisulfonic acid disodium salt (II) furnished the expected cyclodiphosph(V)azanes of the type (H₂L¹-H ₂L⁸). The coordinating beha

Full text of DOI:10.1080/10426500802145049

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Metal Complexes of Phosphorus
Compounds Including
Indigoid Structure: Synthesis,
Characterization, and
Biological Study
Zeinab H. Abd El-Wahab a & Abeer A. Faheim a
a Chemistry Department, Faculty of Science (Girl's) ,
Al-Azhar University , Nasr City, Cairo, Egypt
Published online: 03 Feb 2009.
To cite this article: Zeinab H. Abd El-Wahab & Abeer A. Faheim (2009) Metal
Complexes of Phosphorus Compounds Including Indigoid Structure: Synthesis,
Characterization, and Biological Study, Phosphorus, Sulfur, and Silicon and the Related
Elements, 184:2, 341-361, DOI: 10.1080/10426500802145049
To link to this article: http://dx.doi.org/10.1080/10426500802145049
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Phosphorus, Sulfur, and Silicon, 184:341–361, 2009
Copyright © Taylor & Francis Group, LLC
ISSN: 1042-6507 print / 1563-5325 online
DOI: 10.1080/10426500802145049
Metal Complexes of Phosphorus Compounds Including
Indigoid Structure: Synthesis, Characterization, and
Biological Study
Zeinab H. Abd El-Wahab and Abeer A. Faheim
Chemistry Department, Faculty of Science (Girl’s), Al-Azhar University,
Nasr City, Cairo, Egypt
Interaction of hexachlorocyclodiphosph(V)azanes, (Ia−h) with 5,5ꢀ indigodisul-
fonic acid disodium salt (II) furnished the expected cyclodiphosph(V)azanes of
1
8
1
1
the type (H2L –H2L ). The coordinating behavior of H2L , where H2L is
1,3diphenyl-2,2,4,4-tetrachloro-2,4-di{1,1ꢀ-di(5,5ꢀ indigodisulfonic acid disodium
salt)} cyclodiphosph(V)azane, towards the transition metal ions Mn(II), Co(II),
Ni(II), Cu(II) and Fe(III) was studied. The structures of the isolated products
are proposed based on elemental analyses, molar conductance, spectral analy-
1
sis (IR, H-NMR, and UV-Vis), as well as magnetic susceptibility measurements
and thermogravimetric analysis (TGA). From the elemental analyses, 1:2 (lig-
and:metal) ratio is suggested, and the complexes are found to have the general
1
formula [(M) (L )(Cl)x.n(H O)]·zH O where M = Mn(II) and Co(II) (x = 2, n = 6,
2
2
2
z = 1); M = Ni(II) (x = 2, n = 6, z = 1.5); M = Cu(II) (x = 2, n = 2, z = nil); M = Fe(III)
1
(x = 4, n = 4, z = 4) and (L ) = the deprotonated form of cyclodiphosphazane lig-
and. The molar conductance data show that all complexes are non-electrolytes. The
spectral data and magnetic susceptibility measurements revealed that the ligand
behaves as a dibasic tetradentate ligand coordinated to the metal ions through het-
erocyclic nitrogen and carbonyl oxygen atoms in an octahedral and square planar
manner. Some ligand field parameters (Dq, B, and β), in addition to ligand field sta-
bilization energy (LFSE), were calculated. The thermal behavior of these complexes
is studied using TG technique and the different dynamic parameters are calculated
applying Coats–Redfern equation. Antimicrobial activities have been studied using
the agar–disc diffusion technique, and the higher antimicrobial activity has been
observed for the iron (III) complex compared to the other metal complexes.
Keywords Biological study; cyclodiphosphazane; transition metal complexes
INTRODUCTION
Phosphorus-containing compounds proved to be important in their ap-
plications as antioxidants, corrosion resistant material, stabilizers in
Received 15 November 2007; accepted 22 April 2008.
Address correspondence to Zeinab A. Abd El-Wahab, Chemistry Department, Faculty
of Science (Girl’s), Al-Azhar University, P.O. Box, 11754, Nasr City, Cairo, Egypt. E-mail:
zhabdelwahab@yahoo.com
341

342
Z. H. A. El-Wahab and A. A. Faheim
plastic manufactures, binders, and coatings in refractory ceramics, oil
industry, flam-proofing, and they are used also in phosphate laser
glasses as well as agriculture insecticides and fertilizers.1,2 Interest
in the chemistry of phosphorus-containing heterocyclic compounds is
linked with their participation in many biochemical processes, with
their use as therapeutic preparations and agents for plant protection,
and with use in organic synthesis, metal complex catalysis, and other
areas.3 Over the last decade, the ligands based on the cyclodiphosph(III
or V)azane framework have been studied because of their ability to
coordinate with main group and transition metals.4,5 Although, the
interaction of hexachlorocyclodiphosph(V)azanes with several func-
tional groups containing compounds has been investigated in great
detail,1,2,4,6−16 the literature survey indicates the absence of analogous
reactions with 5,5ꢀindigodisulfonic acid disodium salt (indigo carmine).
Generally, indigo is one of the earliest known colorants. It was initially
extracted from plants and was later marketed as a synthetic product,
and it is used mainly for dyeing blue jeans.17 Indigo carmine is one
of the oldest dyes and still one of the most important used. Its major
industrial application is the dyeing of clothes (blue jeans) and other
blue denim, it has also been employed as redox indicator in analytical
chemistry and as a microscopic stain in biology, and additionally it has
been used as a food additive and as a diagnostic drug.18−20
The main aim of this work and in continuance of our work on
the coordination chemistry of cyclodiphosph(V)azanes, is to design
novel multidentate cyclic phosphorus–nitrogen ligands that are mul-
tifunctional systems particularly capable of holding two metal ions.
So we describe here the synthesis and structural characterization of
cyclodiphosph(V)azanes (H2L1–H2L8) including indigoid structure fol-
lowed by studying the complexation behavior toward Mn(II), Co(II),
Ni(II), Cu(II), and Fe(III) ions via different physicochemical tools such
as elemental analysis, molar conductance, magnetic moment, spectral
(IR,1H-NMR and UV-Vis), and thermal analyses. Furthermore, the syn-
thesized compounds were screened for their antimicrobial activity in
an attempt to understand the influence of metal ion and the ligand
nature on the biological properties.
EXPERIMENTAL
Analysis and Physical Measurements
All chemicals used were of highest available purity. They include
MnCl2·4H2O, CoCl2·6H2O, NiCl2·6H2O, CuCl2·2H2O, and FeCl3·6H2O
(BDH or Sigma); 5,5ꢀindigodisulfonic acid disodium salt (indigo

Metal Complexes of Phosphorus Compounds
343
carmine) and phosphorus pentachloride (Aldrich); and aryl amines:
aniline, p-toluidine, o- and p-anisidine, o- and p-nitroaniline, and o-
and p-chloroaniline (BDH, Sigma and Aldrich). Organic solvents used
included absolute ethyl alcohol, benzene, acetonitrile, diethylether,
dimethylformamide (DMF), and dimethylsulfoxide (DMSO), which
were purchased from Merck or Sigma. Concentrated nitric and per-
chloric acid were reagent grade and were used as supplied.
Carbon, hydrogen, nitrogen, and sulfur contents were determined
using a Perkin-Elmer 2408 CHN analyzer. Metal contents were deter-
mined by titration against standard EDTA solution after complete de-
composition of the complexes and the chloride and phosphorus contents
were determined gravimetrically.21 Melting or decomposition points
were carried out on a melting point apparatus, Gallenkamp, England.
IR spectra were recorded on a Perkin-Elmer FT-IR type 1650 spec-
trophotometer using KBr discs. 1H-NMR spectra were recorded using a
Brucker ARX-300 spectrometer using DMSO-d6 as a solvent. Electronic
spectra of the ligands and the metal complexes were recorded on a Jasco
model V-550 UV-vis spectrophotometer. Magnetic susceptibility of the
metal complexes were measured by the Gouy method at room temper-
ature using a Johnson Matthey, Alpha products, model MKI magnetic
susceptibility balance, and the effective magnetic moments were calcu-
lated using the relation µeff = 2.828 (χm.T)1/2 B.M, where χm is the mo-
lar susceptibility corrected using Pascal’s constants for diamagnetism
of all atoms in the compounds. The molar conductance measurements
were measured in solutions of the metal complexes in DMF (10−3M)
using a WTWD-812 Weilheium-Conductivity meter model LBR, fitted
with a cell model LTA100. A Shimadzu TGA-50H thermal analyzer was
used to record simultaneously the thermogravimetric (TG) and differ-
ential thermogravimetric (DTG) curves, the experiments were carried
out in dynamic nitrogen atmosphere (20 mL min−1) with a heating rate
10◦C min−1 within the temperature range from room temperature up
to 1000◦C using platinum crucibles. Highly sintered α-Al2O3 was used
as a reference. Additionally, the antimicrobial activity was done using
the agar–disc diffusion technique.22
Synthesis of Cyclodiphosph(V)azanes (H2L1–H2L8)
The cyclodiphosph(V)azanes, (H2L1–H2L8) were prepared through
two steps. The first step was preparation of hexachlorocy-
clodiphosph(V)azanes (Ia−h) using the methods of Chapmann and
Kirsanov. A solution of aryl amine (0.1 mol) in 80 mL cold, dry
benzene was added in small portions to a stirred cold solution of

344
Z. H. A. El-Wahab and A. A. Faheim
phosphorus pentachloride (0.1 mol) in 100 mL cold, dry benzene dur-
ing half hour at 15◦C. After the addition was completed, the reaction
mixture was heated under reflux for 3 h under anhydrous conditions
with continuous stirring. After the completion of the reaction (HCl gas
ceased to evolve), the reaction mixture was cooled to room tempera-
ture, and the solids obtained were filtered then washed several times
with dry benzene and dry diethylether to give 1,3diaryl-2,2,2,4,4,4-
hexachlorocyclodiphosph(V)azanes (Ia−h). The second step was the ad-
dition of 5,5ꢀindigodisulfonic acid disodium salt (II) (0.2 mol) in 80
mL cold, dry acetonitrile in small portions to a stirred cold solution
of the prepared cyclodiphosph(V)azanes (Ia−h) (0.1 mol) in 100 mL
cold, dry acetonitrile during a half-hour at 15◦C. After the addition
was completed, the reaction mixture was heated under reflux for 7 h
under anhydrous conditions with continuous stirring, then the solids
obtained were filtered and washed several times with dry acetonitrile
and dry diethylether to give 1,3diaryl-2,2,4,4-tetrachloro-2,4-di{1,1ꢀ‘-
{di(5,5ꢀindigodisulfonic acid disodium salt)} cyclodiphosph(V)azanes
(H2L1–H2L8). These products are of importance because of the presence
of several reactive sites that make them highly reactive and susceptible
to undergo a variety of functionalization processes. Figure 1 illustrates
the synthetic scheme of cyclodiphosph(V)azanes (H2L1–H2L8). Their
elemental analysis and some physicochemical characteristic data are
collected in Table I.
Synthesis of Metal Complexes
A
solution of respective metal chloride, namely, MnCl2·4H2O,
CoCl2·6H2O, NiCl2·6H2O, CuCl2·2H2O, or FeCl3·6H2O, dissolved in
ethanol (40 mL) was added dropwise to a stirred ethanolic solution of
1,3diphenyl-2,2,4,4-tetrachloro-2,4-di{1,1ꢀ-di (5,5ꢀindigodisulfonic acid
disodium salt)} cyclodiphosph(V)azane (H2L1) (60 mL) in a 2:1 metal-
to-ligand molar ratio at room temperature with continuous stirring. Af-
ter complete addition of the metal–salt solution, the reaction mixture
was heated under reflux with continuous stirring for 3 h to ensure the
complete precipitation of the formed complexes. The precipitated solid
complexes were filtered, washed several times with ethanol followed by
diethylether, and dried in a vacuum desiccator over anhydrous calcium
chloride. All metal complexes (1–5) are received as powder, stable in air,
insoluble in common organic solvents but soluble in DMF and DMSO,
and give elemental analysis consistent with the proposed structures.
Their elemental analysis and some physicochemical characteristic data
are collected in Table II.

Metal Complexes of Phosphorus Compounds
345
H
N
O
O
R
N
H
N
NaO3S
NaO3S
+
PCl3
Cl3P
N
H
SO3Na
+
N
H
SO3Na
N
R
O
O
5,5' Indigodisulphonic
acid disodium salt
II
5,5' Indigodisulphonic
acid disodium salt
Hexachlorocyclodiphos-
ph(v)azanes
II
Ia-h
Compd.No
Ia ; H2L1
R
acetonitrile
7hr
C6H5
Ib ; H2L2
Ic ; H2L3
Id ; H2L4
Ie ; H2L5
If ; H2L6
Ig ; H2L7
Ih ; H2L8
C6H4CH3–p
C6H4OCH3–o
C6H4OCH3-p
C6H4NO2-o
C6H4NO2-p
C6H4Cl-o
H
O
NaO3S
N
N
SO3Na
R
O
N
Cl
P
P
Cl
C6H4Cl-p
Cl
N
R
Cl
O
NaO3S
N
O
N
H
SO3Na
1
H2L-H2L8
FIGURE 1 Schematic diagram for preparation of cyclodiphosph(v)azanes,
(H2L1–H2L8). H2L1: 1,3diphenyl-2,2,4,4-tetrachloro-2,4-di{1,1ꢀ-di(5,5ꢀindigod-
isulfonic acid disodium salt)} cyclodiphosph (V)azane. H2L2: 1,3di(p-tolyl)-
2,2,4,4-tetrachloro-2,4-di{1,1ꢀ-di(5,5ꢀindigodisulfonic acid disodium salt)}
cyclodiphosph(V)azane. H2L3: 1,3di(o-anisidyl)-2,2,4,4-tetrachloro-2,4-di{1,1ꢀ-
di(5,5ꢀindigodisulfonic acid disodium salt)} cyclodiphosph(V)azane. H2L4: 1,3di
(p-anisidyl)-2,2,4,4-tetrachloro-2,4-di{1,1ꢀ-di(5,5ꢀindigodisulfonic acid disod-
ium salt)} cyclodiphosph(V)azane. H2L5: 1,3di(o-nitrophenyl)-2,2,4,4-tetra-
chloro-2,4-di{1,1ꢀ-di(5,5ꢀindigodisulfonic acid disodium salt)} cyclodiphosph
(V)azane. H2L6: 1,3di(p-nitrophenyl)-2,2,4,4-tetrachloro-2,4-di{1,1ꢀ-di(5,5ꢀ
indigodisulfonic acid disodium salt)} cyclodiphosph(V)azane. H2L7: 1,3di(o-
chlorophenyl)-2,2,4,4-tetrachloro-2,4-di{1,1ꢀ-di(5,5ꢀindigodisulfonic acid diso-
dium salt)} cyclodiphosph(V)azane. H2L8: 1,3di(p-chlorophenyl)-2,2,4,4-
tetrachloro-2,4-di{1,1ꢀ-di(5,5ꢀindigodisulfonic acid disodium salt)} cyclodipho-
sph(V)azane
Antimicrobial Assay
The cyclodiphosph(V)azane ligand (H2L1) and its metal complexes (1–
5) in addition to MnCl2·4H2O, CoCl2·6H2O, NiCl2·6H2O, CuCl2·2H2O,
and FeCl3·6H2O were screened for antibacterial and antifungal activity
against the sensitive organisms Staphylococcus aureus (ATCC 25923)
and Streptococcus pyogenes (ATCC 19615) as Gram-positive bacteria,

346

347

348
Z. H. A. El-Wahab and A. A. Faheim
Pseudomonas phaseolicola (GSPB 2828) and Pseudomonas fluorescens
(S 97) as Gram-negative bacteria, and the fungi Fusarium oxyspo-
rum, Aspergillus fumigatus, and Candida albicans. The antibiotics
Cephalothin, Chloramphencol, and Cycloheximide were used as stan-
dard references for Gram-positive bacteria, Gram-negative bacteria,
and fungi, respectively, using the agar–disc diffusion technique22 de-
scribed below:
The tested compounds were dissolved in DMF, which has no inhibi-
tion activity to get concentrations of 6.46 × 10−4 to 5.87 × 10−3 M/L.
The test was performed on medium potato dextrose agar (PDA), which
contains an infusion of 200 g potatoes, 6 g dextrose, and 15 g agar. Uni-
form size filter paper disks (3 disks per compound) were impregnated
by an equal volume (10 µl) from the specific concentration of dissolved
tested compounds and carefully placed on inoculated agar surface. Af-
ter incubation for 36 h at 27◦C in the case of bacteria and for 48 h at
24◦C in the case of fungi, inhibition of the organisms, which was evi-
denced by a clear zone surround each disk, was measured and used to
calculate the mean of inhibition zones.
RESULTS AND DISCUSSION
In the present investigation, phosphorus pentachloride reacted in cold,
dry benzene with aryl amines (1:1 molar ratio) to give 1,3diaryl-
2,2,2,4,4,4-hexa-chlorocyclodiphosph(V)azanes (Ia−h). The interaction
between these products and 5,5ꢀindigodisulfonic acid disodium salt
(II) in acetonitrile solution (1:2 molar ratio, respectively) led to cy-
closubstitution at the phosphorus atom by the elimination of one
chlorine atom from each side as HCl gas furnishing 1,3diaryl-2,2,4,4-
tetrachloro-2,4-di{1,1ꢀ-{di (5,5ꢀindigodisulfonic acid disodium salt)} cy-
clodiphosph(V)azanes (H2L1-H2L8).
Because the cyclodiphosph(V)azanes, (H2L1-H2L8) have simi-
lar structures, the ligand; 1,3diphenyl-2,2,4,4-tetrachloro-2,4-di{1,1ꢀ-
{di(5,5ꢀindigodisulfonic acid disodium salt)} cyclodiphosph(V)azane
(H2L1) was selected to study their behavior towards some metal ions
such as Mn (II), Co(II), Ni(II), Cu(II), and Fe(III), which is the our
goal in this article. The isolated metal complexes (1–5) gave elemental
analysis (Table II) compatible with the suggested formula in which the
ligand-metal stoichiometry for all complexes is 1:2, respectively. The
assignment of the proposed structures for the isolated compounds is
based on the different physicochemical tools.

Metal Complexes of Phosphorus Compounds
349
Characterization of Cyclodiphosph(V)azanes (H2L1–H2L8)
The assignment of the proposed structure for 1,3diaryl-2,2,4,4-
tetrachloro-2,4-di{1,1ꢀ-{di(5,5ꢀ-indigodisulfonic acid disodium salt)} cy-
clodiphosph(V)azanes (H2L1–H2L8) is based on the following:
1. The elemental analyses data (Table I) are compatible with the sug-
gested structure.
2. The UV spectra in DMF solvent showed absorption bands at 277–
288 nm (36,101–34,722 cm−1), which are characteristic for the elec-
tron delocalization within the phosphazo four-membered rings.8
1
3. The H-NMR spectra (Table III) showed the characteristic proton
signals at δ 10.65–10.64 ppm (s, NH), δ 7.76–6.41 ppm (m, phenyl
protons), δ 3.60 ppm (s, OCH3), and δ 2.56 ppm (s, CH3).8
4. The infrared spectra (Table III) showed the characteristic bands in
the spectral range of 3300–3290 cm−1; 1660–1658 cm−1and 1628–
1610 cm−1; 1490–1470 cm−1; 1025–1010 cm−1; and 600–579 cm−1
that can be reasonably assigned to ν(N H), ν(C O), ν(C C), ν(P N),
and ν(P-Cl), respectively.4,7,17,23
TABLE III Main IR and 1H-NMR Data with Their Assignment for
Cyclodiphosph(V)azanes (H2L1–H2L8)
IR bands (cm−1
)
Compd. No.
ν
N−H
ν
ν
ν
ν
1H-NMR (δ, ppm)
C=O
C=C
P−N
P−Cl
H2L1
3300 1660, 1628 1475 1025 600 10.64 (s, NH), 7.76–6.52 (m,
phenyl proton)
H2L2
H2L3
H2L4
H2L5
H2L6
H2L7
H2L8
3290 1662, 1614 1470 1010 600 10.65 (s, NH), 7.75–6.41 (m,
phenyl proton), 2.56 (s,CH3)
3290 1668, 1615 1475 1025 588 10.64 (s, NH), 7.65–6.71 (m,
phenyl proton), 3.60 (s,OCH3)
3296 1660, 1610 1480 1022 579 10.64 (s, NH), 7.76–6.48 (m,
phenyl proton), 3.60 (s,OCH3)
3300 1659, 1620 1490 1020 590 10.64 (s, NH), 7.65–6.71 (m,
phenyl proton)
3298 1664, 1622 1480 1010 580 10.64 (s, NH), 7.66–6.56 (m,
phenyl proton)
3294 1660, 1619 1475 1022 588 10.64 (s, NH), 7.75–6.75 (m,
phenyl proton)
3300 1658, 1621 1470 1025 580 10.64 (s, NH), 7.76–6.52 (m,
phenyl proton)
s, singlet; m, multiplet.

350
Z. H. A. El-Wahab and A. A. Faheim
Characterization of Metal Complexes (1–5)
The chemical behavior of cyclodiphosph(V)azane ligand (H2L1) towards
the transition metal cations was the our goal in this article. The metal
cations selected for this purpose were Mn(II), Co(II), Ni(II), Cu(II), and
Fe(III). When a mixture of one mole of cyclodiphosph(V)azane ligand
(H2L1) in dry ethanol was reacted with two moles of the metal salts
in dry ethanol, the metal complexes (1–5) were obtained and gave el-
emental analysis compatible with the suggested formula. Accordingly,
the metal complexes are prepared following the general equation:
H2L1 + 2MClx · nH2O → [(M)2L1(Cl)y · m(H2O)]Z + 2 HCl
M = Mn(II) : x = 2, n = 4, y = 2, m = 6, z = H2O
Co(II) : x = 2, n = 6, y = 2, m = 6, z = H2O
Ni(II) : x = 2, n = 6, y = 2, m = 6, z = 1.5 H2O
Cu(II) : x = 2, n = 2, y = 2, m = 2, z = nil
Fe(III) : x = 3, n = 6, y = 4, m = 4, z = 4H2O
The proposed composition of the metal complexes is confirmed using
the different physicochemical tools. For the structures, see the following
four sections. Additionally, the biological activity was done.
Conductivity Measurements
The molar conductance data of the metal complexes (1–5) at room
temperature in 10−3M DMF solutions were found to be in the range
11.35–7.44 ohm−1cm2 mol−1. Table II revealed the non-electrolytic na-
ture of these complexes. This can be accounted for by the satisfaction
of the bi- or trivalency of the metal by the chloride anion. This implies
the coordination of the anions to the metal ion centers.1,24
IR Spectra
A comparative study of the IR spectra of the metal complexes with
that of the free ligand and those of the complexes of related ligands
gives some positive information regarding the binding sites of the cy-
clodiphosph(V)azanes.
The IR spectra of metal complexes (Table IV) show that the stretch-
ing vibration band ν(NH) of heterocyclic ring (which in the free ligand,
H2L1 at 3300 cm−1) disappeared in the spectra of all metal complexes
(1–5) indicating the deprotonation of this group as a result of com-
plexation with metal ions. The strong absorption band appearing in
the IR spectrum of the free ligand H2L1 at 1628 cm−1 assigned to

Metal Complexes of Phosphorus Compounds
351
TABLE IV Characteristic IR Bands for Cyclodiphosph(V)azane,
(H2L1) and Its Metal Complexes 1–5
IR bands (cm−1
)
Compd. No.
ν
(H2O)
ν
N−H
ν
ν
ν
ν
ν
ν
O−H
C=O
C=C
P−N
P−Cl
M−O
M−N
H2L1
—
3300 1660, 1628 1475 1025
600
600
598
600
598
600
—
—
1
2
3
4
5
3410
3492
3400
3420
3428
—
—
—
—
—
1658, 1615 1474 1023
1659, 1600 1473 1025
1660, 1620 1471 1024
1658, 1620 1475 1025
1658, 1600 1473 1023
525
500
501
535
510
490
440
420
480
460
theν(C O) stretching vibrations appears at lower wave numbers (1620–
1600 cm−1) in all metal complexes in accordance with the coordination
of this group in complex formation, while there is little change for the
other carbonyl group (1660–1658 cm−1), thus ruling out its coordina-
tion. Conclusive evidence regarding the bonding of both heterocyclic
nitrogen and carbonyl oxygen atoms to the metal ions is provided by
the appearance of new medium and/or weak bands at lower frequen-
cies between 535–500 cm−1 and 490–420 cm−1 as a result of ν(M O)
and ν(M N) stretching modes, respectively.4,25 These stretches were
not present in the spectra of the free ligand. The broad bands observed
at 3492–3400 cm−1 in the spectra of all metal complexes can be as-
signed to the presence of water and/or coordinated water molecules25
supported by thermal analyses (see Kinetic Study section). It is obvious
from the IR data that cyclodiphosph(V)azane ligand, (H2L1) behaves
as a dibasic tetradentate ligand coordinated to the metal ions through
the deprotonated heterocyclic nitrogen and carbonyl oxygen atoms.
Magnetic Properties and Electronic Spectra
The magnetic moments of the metal complexes are measured at
room temperature and given in Table II. The complexes show magnetic
moment values of 5.50 and 5.91 BM corresponding to five unpaired
electrons expected for Mn(II) and Fe(III) complexes; 4.89, 3.02, and 1.98
BM corresponding to three, two, and one unpaired electrons expected
for Co(II), Ni (II), and Cu(II) complexes, respectively.26
The electronic spectra of the metal complexes showed absorption
bands at 270–283 nm (37,037–35,336 cm−1), which are characteristic of
the phosphazo four-membered ring.8 The reflectance spectra of Mn(II)
and Fe(III) complexes 1 and 5 display one weak band at 23,474 cm−1 for
Mn(II) complex (1) and 21,186 cm−1 for Fe(III) complex (5). These may

352
Z. H. A. El-Wahab and A. A. Faheim
be assigned to the charge transfer band L→M in addition to two bands
at 15,552 and 17,857 cm−1 for Mn(II) complex (1) and 16,807, 17,730
4
cm−1 for Fe(III) complex (5), which may be assigned to 6A1g → T1g tran-
sition. These results, together with the measured magnetic moments
values, are compatible with those reported for octahedral geometry
around Mn(II) and Fe(III) ions. The electronic spectrum of cobalt (II)
complex (2) displays two absorption bands at 17,036 and 19,231 cm−1
4
4
4
4
may be assignable to T1g (F) → A2g (F) and T1g (F) → T1g (P) tran-
sitions, respectively, suggesting octahedral configuration. The value of
magnetic moment (4.89 BM) is in good agreement with those reported
for the octahedral structure. The electronic spectrum of nickel (II) com-
plex (3) displays three absorption bands at 12,853, 19,802, and 20,325
cm−1, suggesting octahedral configuration about Ni (II) ion and may at-
3
3
3
tributed to 3A2g(F) → T2g(F), 3A2g(F) → T1g(F), and 3A2g(F) → T1g (P)
transitions, respectively. The magnetic moment value (3.02 BM) is in
good agreement with those reported for the octahedral structure. The
electronic spectrum of copper (II) complex (4) gave two bands at 14,577
and 16,287 cm−1 which may be assignable to the transition 2B1g → B2g
2
2
2
and B1g → Eg, suggesting square planar geometry. Its magnetic mo-
ment value (1.98 BM) supports the square planar structure. The data
that characterize these metal complexes are analogous to other metal
complexes containing a phosphazo four-membered ring.4,6,27,28
Various ligand field parameters, (Dq, B, and β) in addition to ligand
field stabilization energy (LFSE) were calculated for octahedral Co(II)
and Ni(II) complexes (Table V). In the octahedral cobalt complex, the
values of (υ2) and (υ3) are used to calculate the parameters (10 Dq) and
(B), while in the octahedral Ni (II) complex, the energy of the first spin
allowed transition directly and gives the value of (10Dq); also (B) values
have been calculated.29
Thermogravimetric Study
The thermogravimetric study for the metal complexes was carried
out within the temperature range from room temperature up to 1000◦C.
The determined temperature ranges and percent losses in mass of the
solid complexes on heating are given in Table VI. The results obtained
are in good agreement with the theoretical formulae suggested from
the elemental analyses. Different thermodynamic parameters are cal-
culated and listed in Table VII. Details are provided for the complex
[(Mn)2L1(Cl)2(H2O)6]·H2O. Figure 2 shows a representative example
for thermal analysis of the metal complexes under study, and reveals
the following findings:

353

354

Metal Complexes of Phosphorus Compounds
355
TABLE VII Thermodynamic Data of the Thermal Decomposition
Steps of Metal Complexes
E∗
ꢁS∗
ꢁH∗
ꢁG∗
Complex compound
Stage (kJ mol−1) (JK−1 mol−1) (kJ mol−1) (kJ mol−1
)
1 [(Mn)2L1(Cl)2(H2O)6].H2O
I
II
III
IV
V
38.24
55.18
76.99
99.27
143.02
36.55
65.59
102.27
44.35
66.98
88.79
113.65
155.39
60.94
104.38
179.04
214.83
59.21
89.67
112.58
139.91
−88.12
−65.99
−66.80
−70.41
−48.97
−94.05
−43.90
−29.32
−100.39
−46.33
−83.26
−46.90
−67.70
−47.39
−26.81
−30.62
−57.62
−39.79
−81.91
−46.40
−68.83
35.43
51.92
73.03
94.49
135.98
33.03
60.73
95.20
41.51
63.56
84.51
107.72
147.41
56.64
98.93
172.84
202.16
56.29
85.95
107.29
132.43
29.82
25.92
22.75
40.58
57.77
39.82
25.70
57.57
34.37
19.11
42.96
33.55
65.14
24.56
17.69
23.02
53.33
14.02
36.70
29.62
62.08
2 [(Co)2L1(Cl)2(H2O)6].H2O
I
II
III
I
II
III
IV
V
3 [(Ni) L1(Cl) (H O) ].11/ H O
2
2
2
2
6
2
4 [(Cu)2L1(Cl)2(H2O)2]
I
II
III
IV
I
II
III
IV
5 [(Fe)2L1(Cl)4(H2O)4].4H2O
.
FIGURE 2 TG thermograms for metal complex [(Mn)2L1(Cl)2(H2O)6] H2O.

356
Z. H. A. El-Wahab and A. A. Faheim
The first decomposition stage takes place at temperature range 43–
86◦C, corresponding to release of one molecule of H2O (hydrated). This
step brings weight loss of 1.31% against the calculated loss of 1.11%.
The second decomposition stage occurs at 86–152◦C, and the mass loss
observed is 2.48% against the calculated loss of 2.22%, which may arise
from the elimination of one molecule of H2O (coordinated). The third
stage of decomposition occurs at 152–253◦C, and the mass loss observed
is 5.04% against a calculated loss of 4.44% due to a loss of two molecules
of H2O (coordinated). The fourth stage of decomposition occurs in the
253–350◦C range, and the mass loss observed is 12.00% against a calcu-
lated loss of 12.15%, corresponding to loss of three molecules of H2O (co-
ordinated) and Cl2. The final stage of decomposition is two steps within
the temperature range 350–795◦C, which represents the decomposition
of the organic part with a found mass loss of 65.00% (calcd.64.98%). At
the end of the thermogram, 2MnCl2·2Na2S2O3was the residue [calcu-
lated (found) %: 35.02 (35.00)]. The thermal decomposition is suggested
to proceed as shown in Scheme 1:
o
43-86
C
1
(Mn) L1(Cl) (H O)
[
(Mn)2L (Cl)2(H2O)6
. H O
]
[
]
2
2
2
2
6
- H2O hydr.
o
86-152
C
- H2O coord.
o
152-253
C
(Mn) L1(Cl) (H O)
]
5
(Mn) L1(Cl) (H O)
[
[
]
2
2
2
2
2
2
3
- H O coord.
2
2
o
253-350
C
-(3H2O coord., Cl2)
o
350-795
C
[(Mn)2L1
]
2MnCl2.2Na2S2O3
SCHEME 1
The thermal decomposition for the other metal complexes is summa-
rized in Schemes 2–5:
o
43-257
C
1
1
(Co) L (Cl) (H O)
. H O
]
6
[
[
(Co) L (Cl) (H O)
]
2
2
2
2
2
2
2
3
-(H2O hydr.,3H2O coord.)
o
257-365
C
-(3H2O coord.,Cl2)
o
365-788
C
2CoCl2.2Na2S2O3
[ (Co)2L1 ]
SCHEME 2

Metal Complexes of Phosphorus Compounds
357
o
1
45-92
C
[(Ni)2 L1
.
[
(Ni)2 L(Cl2)(H 2 O )6
]
(Cl)2(H2 O)6
]
H2 O
1
1/2
-1 1/2
H 2 O hydr.
o
92-184 C
-2H 2O coord.
o
300-580
C
o
[(N i)2.3/4 L1 ]
]
(Ni)2 L1(Cl)2(H 2 O )4
[(N i)2L1
184-300 C
[
]
-1/4 L 1
-(4H 2O coord., C l2)
o
580-793 C
2 N iC l2 .2 N a2S 2O 3
SCHEME 3
o
150-338 C
338-427oC
Cl2
1
[ (Cu)2L(Cl)2 ]
1
(Cu) L1(Cl) (H O)
[
[
]
(Cu)2L
]
2
2
2
2
2
H O
coord.
2
o
427-519 C
1
-1/4 L
o
1
519-779 C
[ (Cu) . 3/4L ]
2 Cu. 4Na
2
SCHEME 4
o
38-118 C
1
[
(Fe)2L (Cl)4(H2O)4
[(Fe)2L1(Cl)4(H2O)4 ]
]
. 4 H2O
hydr.
-4
H2O
o
118-230 C
-4H O coord.
2
o
o
230-496 C
496-757 C
1
1
2Fe.4Na
[ (Fe)2. 3/4L ]
[ (Fe)2L (Cl)4]
1
)
-(2Cl , 1/4 L
2
SCHEME 5
Kinetic Study
The activation energy (ꢁE*) values of the various decomposition
stages for the metal complexes were determined from the TG and DTG
themograms using the Coats–Redfern equation in the following form:
ꢀ
ꢁ
ꢀ
ꢂ
ꢃꢁ
log{Wf /(Wf − W)}
AR
θE∗
2RT
E∗
E∗
2.303RT
log
= log
1 −
−
T2
where Wf is the mass loss at the completion of the reaction, W is the
mass loss up to temperature T, R is the gas constant, E is the activation
∼
energy, θ is the heating rate and (1–(2RT/E*))
1. A plot of the left-
=
hand side of this equation against 1/T gives a slope; from the intercept
and linear slope of such stages, the (A) and (E*) values were deter-
mined. The other kinetic parameters—the entropy of activation (ꢁS*),
enthalpy of activation (ꢁH*), and the free energy change of activation
(ꢁG*)—were calculated using the following relationships:
ꢂ
ꢃ
Ah
KT
ꢁH∗ = E − RT ; ꢁG∗ = H∗ − TS∗ and ꢁS∗ = 2.303 log
R

358
Z. H. A. El-Wahab and A. A. Faheim
where k and h are the Boltzmann and Planck constants, respectively.
The negative values of entropy indicate that the activated complexes
have more ordered systems than the reactants.
Antibacterial and Antifungal Assay
The screening data obtained for the compounds under study against
the sensitive organisms S. aureus, S. pyogenes, P. fluorescens, P.
phaseolicola, F. oxysporum, A. fumigatus, and C. albicans using the
disc–agar diffusion technique22 are summarized in Table VIII. A com-
parison of all tested compounds towards the different organisms brings
out the following facts to light:
r
The highest antimicrobial activity among the group of the tested
compounds was observed against the fungi strains.
The cyclodiphosph(V)azane ligand (H2L1) displayed intermediate ac-
r
tivity against all types of bacteria and fungi species.
Generally the activity of the free ligand was increased upon complex-
ation with metal ions; this enhancement in activity can be explained
r
TABLE VIII Antimicrobial Screening Results of the Compounds
Under Study
Gram-positive
bacteria
Gram-negative
bacteria
Compd. No.
Fungi
H2L1
(36) 14
(38) 15
15 (38)
15 (38)
15 (38)
(64) 25
(37) 14
(50) 19
(47) 18
(47) 18
(39) 15
(67) 26
(29) 11
(50) 19
18 (47)
16 (42)
18 (47)
(44) 15
18 (53)
17 (50)
19 (56)
18 (53)
30 (88)
(35) 12
(44) 15
18 (53)
17 (50)
20 (59)
(41) 15
16 (43)
16 (43)
19 (51)
17 (56)
29 (78)
(30) 11
(27) 10
13 (35)
14 (38)
21 (57)
17 (49)
21 (60)
21 (60)
22 (63)
22 (63)
33 (94)
(46) 16
(46) 16
(37) 13
(43) 15
(57) 20
19 (48)
22 (55)
24 (60)
21 (53)
23 (58)
36 (90)
(35) 14
(40) 16
(45) 18
(35) 14
(48) 19
18 (50)
23 (64)
24 (67)
23 (64)
24 (92)
34 (94)
(36) 13
(50) 18
(31) 11
(33) 12
(61) 22
1
2
3
4
5
MnCl2·4H2O (26) 10
CoCl2·6H2O
NiCl2·6H2O
CuCl2·2H2O
FeCl3·6H2O
R.S.
(49) 19
14 (36)
18 (46)
20 (51)
39 (100) 38 (100) 34 (100) 37 (100) 35 (100) 40 (100) 36 (100)
• The test was done using the agar–disc diffusion method.
• % Activity index in parentheses.
• R.S., Reference standard: Chloramphencol, Cephalothin, and Cycloheximide were
used as standard references for Gram-positive bacteria, Gram-negative bacteria, and
antifungal, respectively.
• Inhibition values: –No effect; 3–13 low activity; 14–24 intermediate activity;
25–32 high activity; and >32 very high activity.

Metal Complexes of Phosphorus Compounds
359
on the basis of chelation theory.30 Chelation reduces the polarity of
the metal ion considerably, mainly because of the partial sharing of
its positive charge with donor groups and the possible π-electrons de-
localization over the whole chelate ring. Chelation not only reduces
the polarity of metal ion, but also increases the lipophilic character of
the chelate. As a result of this, the interaction between the metal ion
and the cell walls is favored, resulting in interference with normal
cell processes.
The effect of all metal complexes towards the fungi species was
greater than the bacteria species.
The metal complexes (1–4) displayed intermediate activity against
all types of bacteria and fungi species with inhibition zone values
greater than the free ligand (H2L1).
Fe(III) complex (5) had a higher degree of activity than all the
other metal complexes or the free ligand (H2L1) against all types
of bacteria and fungi. It displayed high activity. Only the Fe(III)
complex (5) had an effect comparable with that of the standards
(Chloramphencol, Cephalothin, and Cycloheximide) towards the
tested organisms. This may have been due to the trivalent state of
the metal ion and/or the increase in the number of chloride around
the metal ion.
r
r
r
STRUCTURAL INFORMATION
From all of the above observations based on elemental analysis, molar
1
conductance, magnetic moment, and spectral (IR, H-NMR, and UV-
Vis) and thermal analyses, the proposed composition for the structure
of the metal complexes (Figures 3 and 4) discussed herein indicates
that the following:
r
The ligand acts a dibasic tetradentate, and both the heterocyclic
nitrogen and carbonyl oxygen atoms are involved in complexation
with metal ions. Microanalysis reveals 2:1 metals-to-ligand ratio.
All metal complexes are non-electrolyte. This implies the coordina-
tion of the chloride anions to the metal ion center.
Octahedral structure was suggested for Mn(II), Co(II), Ni(II), and
Fe(III) complexes. The Cu(II) complex is square planar.
r
r

360
Z. H. A. El-Wahab and A. A. Faheim
OH2
OH2
Cl
X
O
M
N
NaO3S
N
SO3Na
R
N
O
Cl
Cl P
.n H2O
P Cl
Cl
N
R
O
NaO3S
N
N
SO3Na
O
Cl
X
M
OH2
H2O
FIGURE 3 Suggested structure of the metal complexes 1–3 and 5. M = Mn(II)
or Co (II)−: x = H2O, n = 1; Ni(II): x = H2O, n = 1.5; Fe(III): x = Cl, n = 4.
OH2
Cu Cl
O
NaO3S
N
N
SO3Na
R
N
O
Cl
Cl P
P
Cl
N
R
Cl
O
NaO3S
N
O
N
SO3Na
Cl Cu
H2O
FIGURE 4 Suggested structure of the Cu(II) complex 4.

Metal Complexes of Phosphorus Compounds
361
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