Synthesis, characterisation and biological evaluation of lanthanide(III) complexes with 3-acetylcoumarin-o-aminobenzoylhydrazone (ACAB)

Article abstract of DOI:10.1248/cpb.53.1077

Lanthanide(III) complexes of the general formula [Ln(ACAB) ₂(NO₃)₂(H₂O)₂] ·NO₃·H₂O where Ln=La(III), Pr(III), Nd(III), Sm(III), Eu(III), Gd(III), Tb(III), Dy(III) and Y(III), ACAB=3-acetylcoumarin- o-aminobenzoylhydrazone have been isolated and characterised based on elemental analyses, molar conductance, IR, ¹H- and ¹³C-NMR, UV, TG/DTA and EPR spectral studies. The ligand behaves in bidentate fashion coordinating through hydrazide >C=O and nitrogen of >C=N. A coordination number of ten is assigned to the complexes. Antibacterial and Antifungal studies indicate an enhancement of activity of the ligand on complexation.

Full text of DOI:10.1248/cpb.53.1077

September 2005
Chem. Pharm. Bull. 53(9) 1077—1082 (2005)
1077
Synthesis, Characterisation and Biological Evaluation of Lanthanide(III)
Complexes with 3-Acetylcoumarin-o-aminobenzoylhydrazone (ACAB)
*
Kalagouda B. GUDASI, Rashmi V. SHENOY, Ramesh S. VADAVI, Manjula S. PATIL, and
Siddappa A. PATIL
Department of Chemistry, Karnatak University; Dharwad–580 003, India.
Received December 1, 2004; accepted June 9, 2005
Lanthanide(III) complexes of the general formula [Ln(ACAB)2(NO3)2(H2O)2]·NO3·H2O where LnꢀLa(III),
Pr(III), Nd(III), Sm(III), Eu(III), Gd(III), Tb(III), Dy(III) and Y(III), ACABꢀ3-acetylcoumarin-o-aminoben-
1
zoylhydrazone have been isolated and characterised based on elemental analyses, molar conductance, IR, H-
and 13C-NMR, UV, TG/DTA and EPR spectral studies. The ligand behaves in bidentate fashion coordinating
through hydrazide ꢁCꢀO and nitrogen of ꢁCꢀN. A coordination number of ten is assigned to the complexes.
Antibacterial and Antifungal studies indicate an enhancement of activity of the ligand on complexation.
Key words lanthanide metal complex; hydrazone complex; spectral study; antibacterial activity; antifungal activity
to the solution of o-aminobenzoylhydrazide (15.1 g, 100 mmol) in methanol
(130 ml) and stirred for 2—3 h, which yielded an orange crystalline product,
which was filtered, washed with alcohol and air-dried. It was further recrys-
tallised from methanol. (Yield 92%, mp 115—116 °C.)
Preparation of Complexes Ln(NO3)3 (1 mmol) dissolved in minimum
quantity of methanol was added to a hot solution of ligand (1 mmol) in 30 ml
methanol/CHCl3 (1 : 1, v/v) and refluxed for 1 h. The pH was then raised to
6.5 by adding methanolic solution of sodium acetate and was further re-
fluxed for 4—5 h. The clear orange solution formed was concentrated to a
small volume and the precipitate obtained was washed swiftly with cold dis-
tilled water and air-dried. (Yield 85%, mpꢁ250 °C.)
Coumarins generate strong interest stemming from their
great physiological and biological activities1) which is further
exemplified by their roles as anticoagulants (dicoumarols/
warfarins), aflatoxins and psoaralens,2) the important drugs in
use. Apart from the above, their role as caging agents in pho-
toactivable “caged” analogues of biomolecules, cytidine
diphosphate and glutamic acid,3) and as probes for reactive
oxygen species (ROS)4) spurred further interest in these com-
pounds. Earlier studies from our laboratory5,6) on biological
activity of coumarins and their complexes, showed signifi-
cant enhancement of antibacterial and antifungal activity of
the coumarin derivative on complexation. Keeping this in
mind, and in continuation of our previous studies,5—7) in the
present contribution we report the synthesis and characterisa-
tion of Ln(III) complexes with a potentially quadridentate
ligand, 3-acetylcoumarin-o-aminobenzoylhydrazone (ACAB)
and effect of complexation on biological activity of this lig-
and.
Results and Discussion
The reaction of ACAB with Ln(NO3)3 resulted in the for-
mation of complexes of the composition [Ln(ACAB)2(NO3)2
(H2O)2]·NO3·H2O, where LnꢂLa(III), Pr(III), Nd(III),
Sm(III), Eu(III), Gd(III), Tb(III), Dy(III) and Y(III) (Table
1). The complexes are non-hygroscopic, readily soluble in
common organic solvents such as ethanol, methanol, ace-
tone, dichloromethane, DMF and DMSO. All complexes are
extremely soluble in water. Molar conductivity measure-
ments of the complexes are commensurate with 1 : 1 elec-
trolytic behaviour.11)
Magnetic Properties and EPR Spectra The La(III) and
Y(III) complexes are diamagnetic as expected. The room
temperature magnetic moments of the complexes do not
show much deviation from Van Vleck values12) indicating
that there is no significant participation of the 4f electrons in
bonding since they are well shielded by the 5s2 5p6 octet.
However in case of Sm(III) and Eu(III) complexes a slight
variation from Van Vleck values was observed.13) Due to the
Experimental
Materials Reagent grade chemicals were used without further purifica-
tion. Methyl anthranilate was obtained from S.D. Fine Chemicals Ltd. and
Hydrazine hydrate was from Rankem. 3-Acetylcoumarin and o-aminoben-
zoylhydrazide were synthesized according to literature method.8,9)
Physical Measurements The metal contents of the complexes were de-
termined by complexometric titrations against EDTA.10) Carbon, Hydrogen
and Nitrogen contents were determined by using a Carlo-Erba Strumen-
tazione (Italy) CHN analyzer. Molar conductivities in DMSO (10ꢀ3 mol lꢀ1
)
at room temperature (26 °C) were measured using an Elico conductivity
bridge having platinum electrodes. Magnetic moments were determined by a
Faraday balance. The IR spectra of ligand and its metal complexes were
recorded on a Nicolet 170 SX FT-IR spectrometer in the range 400—
4000 cmꢀ1 using KBr discs. The EPR spectrum of the Gd(III) complex was
recorded on a Varian E-4X band spectrophotometer. The 1D and 2D NMR
spectra of the ligand were recorded in DMSO-d6 on Bruker AMX 500 spec-
trometer operating at 500.13 MHz for 1H and 127.77 MHz for 13C using
1
1
5 mm H/13C dual probe. The H- and 13C-NMR spectra of La(III) complex
were recorded in DMSO-d6 on Bruker Avance 300 spectrometer operating at
1
1
300.13 MHz for H and 75.47 MHz for 13C using 5 mm H/13C dual probe.
UV–Visible spectra were measured on a Hitachi 2001 spectrophotometer
using dimethylsulfoxide (DMSO) as solvent. Thermogravimetry (TG) and
Differential Thermal Analysis (DTA) measurements were made in N2 atmo-
sphere between 20 and 1000 °C using a Perkin-Elmer (Pyris Diamond) Ana-
lyzer. Lanthanide nitrates were prepared by dissolving the corresponding
oxide (99.99%, Indian Rare Earth) in 50% HNO3, followed by the evapora-
tion of the excess acid. The ligand (ACAB) was synthesized according to the
scheme (Chart 1).
Synthesis of Ligand 3-Acetyl coumarin (18.81 g, 100 mmol) was added
Chart 1
∗ To whom correspondence should be addressed. e-mail: kbgudasi@rediffmail.com
© 2005 Pharmaceutical Society of Japan

1078
Vol. 53, No. 9
Table 1. Analytical, Conductance and Magnetic Data of Ln(III) Complexes of ACAB
Magnetic
moment
(BM)
Elemental analysis (%)b)
Conductancea)
Code
Compound
M
C
H
N
13.17
C0
C1
C2
C3
C4
C5
C6
C7
C8
C9
ACAB
—
—
—
( —
67.31
67.28
21.45
21.15
21.39
21.28
21.23
21.04
21.04
20.92
21.00
20.89
20.93
20.77
21.21
20.75
20.55
20.67
21.92
22.24
4.77
4.98
1.42
1.76
1.63
1.75
1.44
1.75
1.65
1.74
1.88
1.74
1.81
1.73
1.69
1.72
1.73
1.72
1.89
1.85
13.08)
07.01
06.85)
06.54
06.84)
06.66
06.82)
06.73
06.78)
06.65
06.77)
06.81
06.73)
06.78
06.72)
06.59
06.70)
07.04
07.20)
[La(ACAB)2(NO3)2(H2O)2]·NO3·H2O
[Pr(ACAB)2(NO3)2(H2O)2]·NO3·H2O
[Nd(ACAB)2(NO3)2(H2O)2]·NO3·H2O
[Sm(ACAB)2(NO3)2(H2O)2]·NO3·H2O
[Eu(ACAB)2(NO3)2(H2O)2]·NO3·H2O
[Gd(ACAB)2(NO3)2(H2O)2]·NO3·H2O
[Tb(ACAB)2(NO3)2(H2O)2]·NO3·H2O
[Dy(ACAB)2(NO3)2(H2O)2]·NO3·H2O
[Y(ACAB)2(NO3)2(H2O)2]·NO3·H2O
dia
43.22
48.27
49.59
44.56
47.21
41.09
48.92
48.45
41.87
13.42
(13.60
13.56
(13.70
14.55
(14.05
13.93
(14.56
14.02
(14.69
14.89
(15.12
14.91
(15.26
15.08
(15.55
08.69
(09.15
03.78
03.72
02.05
03.78
07.98
09.82
10.77
dia
a) Wꢀ1 cm2 molꢀ1, b) calculated values are in parentheses. diaꢂdiamagnetic.
low J–J separation, the energy level between the ground state 1649 cmꢀ1 were assigned to the n(CꢂO) lactone20) and
and the next higher level being only of the order of KT, the n(CꢂO)21) of the hydrazide group, respectively. A band at
excited states are also populated leading to anomalous mag- 1617 cmꢀ1 was ascribed to the n(CꢂN) of the azomethine
netic moments. This is known as the first order Zeeman ef- group.20) Because of the involvement of lactone carbonyl in
fect.14,15)
hydrogen bonding with the CH3 group, it is observed at a
8
Gd (III) has an s7/2 single ion ground state and a spin lower frequency.17) The amide II band is observed at
value Iꢂ3/2.The ground state is orbitally non-degenerate and 1518 cmꢀ1 whereas a band at 1248 cmꢀ1 is assigned to the
well separated from the excited states. Compared to the other amide III band.17)
lanthanides, it does not show large anisotropic effects, thus
The presence of the n(CꢂO) or amide I band at a rela-
giving rise to single ion magnetic properties.16) The EPR tively low wave number (1649 cmꢀ1) suggests the involve-
spectra (both at RT and LNT) were broad having similar ꢀgꢁ ment of the carbonyl oxygen in strong intramolecular hydro-
value of 2.0, which is nearly equal to the free electron value gen bonding with the NH2 group22) as mentioned earlier.
(TCNE ꢀgꢁꢂ2.00277). Similar line widths at both the tem-
On complexation, the n(CꢂO) of hydrazide is shifted to
peratures indicate spin–lattice and spin–spin relaxation lower wave number (1644—1646 cmꢀ1) as is the amide II
processes contribute equally to line width.
band21) which is also shifted to lower frequency (1512—
IR Spectra The IR band assignments are given in Table 1516 cmꢀ1) whereas the amide III band (1248 cmꢀ1) under-
2. IR spectra of the complexes shows that ACAB behaves as goes a shift to higher frequency (1256—1262 cmꢀ1).23) These
a bidentate ligand, coordinating through hydrazide carbonyl changes in amide group vibrations indicate the coordination
and azomethine nitrogen, with the carbonyl of lactone and of the amide oxygen to the metal ion.24,21)
ring –NH2 remaining free. The coordinating behavior of the
ligand is shown in Fig. 1. (Lattice molecules have been omit- been observed, which is attributed to the deconjugation of the
Increase in lactone carbonyl frequency (13—21 cmꢀ1) has
ted for clarity.)
carbonyl group due to coordination via azomethine nitro-
In the free ligand, a sharp peak at 3646 cmꢀ1 is due to the gen25) and breakdown of hydrogen bonding between lactone
presence of a methanol molecule, which fulfils a space-filling oxygen and hydrogen of methyl group.
role in the lattice. Single crystal study of the ligand indicates
Further, coordination of the azomethine nitrogen to the
that it is involved in a series of intermolecular and intramole- metal leads to reduction in electron density of the azome-
cular hydrogen bondings17) and the relevant ones are shown thine linkage, which results in a downward shift (10—
in Fig. 2.
11 cmꢀ1) of n(CꢂN) band.26,27) The complexes exhibit bands
The hydrazide carbonyl is intramolecularly hydrogen at 1488 (n4), 1285 (n1), 1029—1035 (n2), 810—813 (n6),
bonded (Fig. 2) with hydrogen of –NH2 and lattice held 751—754 (n3) and 693—695 cmꢀ1 (n5) corresponding to the
methanol. Similarly, the lactone carbonyl oxygen is intermol- coordinated nitrate molecules. The magnitudes of n4–n1 and
ecularly hydrogen bonded with amide NH, H5C and CH3 n3–n5 lie in the range 207—208 cmꢀ1 and 50—58 cmꢀ1 re-
group. The nNH stretch is observed at 3260 cmꢀ1. The bands spectively, which is characteristic of bidentate coordination
at 3437 and 3367 cmꢀ1 were assigned to the n(asym) and of nitrate moiety.28)
n(sym) vibrations of the –NH2 group respectively.18) A band
A broad band between 3370—3380 cmꢀ1 due to coordi-
at 1584 cmꢀ1 is assigned to the –NH deformation mode of nated water molecules obscures the NH2 stretching frequen-
the primary amine.19) Intense bands observed at 1695 and cies. However the non-involvement of the latter in coordina-

September 2005
1079
n
n
n
Fig. 1
n
n
n
Fig. 2
1
tion is proved by H-NMR studies. The presence of coordi-
nated water molecules in all complexes was indicated by
their characteristic rocking frequency of non ligand band be-
tween 812—826 cmꢀ1.29) The band due to ionic nitrate was
observed at 1384 cmꢀ1. The presence of ionic nitrate is in
confirmation with the conductivity measurements.
n
1
1H-NMR Spectra The H-NMR spectra of ACAB and
its La(III) complex was recorded in DMSO-d6 and the spec-
tral assignments (Table 3) have been made based on compar-
isons with NMR assignments of 3-acetylcoumarin and
methyl anthranilate30,31) and 2D HETCOR (HMQC) (Fig. 3)
NMR of ACAB.
A sharp singlet appearing in the upfield region at 2.31 ppm
integrates for three protons of the methyl group (Fig. 2). The
signal due to –NH (D2O exchangeable) appears at 10.59 ppm
as a broad singlet and corresponds to one proton. A signal at
6.22 ppm is assignable to protons of the free –NH2 (ex-
changes with D2O) and accounts for two protons. The aro-
matic protons are observed in the range 6.59—8.23 ppm.
A multiplet at 7.42 ppm is formed by the merger of a dou-
blet and a triplet of H12 and H14. Three doublets at 7.88,
7.56 and 6.76 ppm are due to H5, H15 and H2. The triplets at
7.66, 7.21 and 6.59 ppm are ascribed to H13, H3 and H4. A
sharp peak at 8.23 ppm is due to the H10 of the coumarin
moiety.
n
n
n
A quartet and a singlet at 4.12 and 3.17 ppm are due to
–OH and –CH3 protons of the lattice held methanol mole-
cule. In this case, the coupling interaction between –CH3 and
–OH was observed leading to splitting of the –CH3 peak
(Jꢂ5.1 Hz).17)
n
n
1
In the H-NMR spectrum of La(III) complex, the –NH2
signals remain almost unperturbed at 6.21 ppm indicating the
non-involvement of this group in coordination. The signals
due to –NH and –CH3 remain almost unchanged at 10.60 and
2.31 ppm. The aromatic protons do not show any shift com-

1080
Vol. 53, No. 9
Table 3. 1H- and 13C-NMR Spectral Data (in d ppm) of ACAB and Its La(III) Complex
Carbon
ACAB
La(III) complex
Proton
ACAB
La(III) complex
—
6.76 (d, Jꢂ8.1 Hz)
7.21 (t, Jꢂ7.0 Hz)
C1a)
C2
C3
C4
C5
150.52
115.25
133.28
116.86
133.08
115.76
160.14
150.52
119.66
142.39
117.14
127.80
125.66
130.06
116.97
154.30
154.30
17.04
150.51
115.24
133.29
116.86
133.10
115.76
162.14
152.01
119.81, 119.65
142.40
117.16
127.78
125.67
130.06
116.96
154.28
154.37
17.04
—
H2
H3
H4
H5
—
—
—
—
—
6.76 (d, Jꢂ8.1 Hz)
7.21 (t, Jꢂ7.5 Hz)
6.59 (t, Jꢂ7.4 Hz)
7.88 (d, Jꢂ7.5 Hz)
6.59 (t, Jꢂ7.3 Hz)
7.87 (d, Jꢂ7.3 Hz)
C6
—
—
—
—
—
—
C7
C8a)
C9
—
8.23 (s)
—
C10
C11
C12
C13
C14
C15
C16b)
C17b)
C18
C19*
—
H10
—
8.23 (s)
—
—
H12
H13
H14
H15
—
—
–CH3
—
7.42 (m)
7.66 (t, Jꢂ7.7 Hz)
7.42 (m)
7.56 (d, Jꢂ7.7 Hz)
—
7.42 (m)
7.66 (m)
7.42 (m)
7.56 (d, Jꢂ7.6 Hz)
—
—
—
2.31 (s)
2.31 (s)
—
10.60 (s)
6.21 (s)
49.46
—
—
49.46
—
—
—
–NH
–NH2
10.59 (s, 2H)
6.22 (s)
—
a) These signals appear as a single line. b) These signals appear as a single line. ∗ CH3 of lattice methanol.
Fig. 3. 2D HETCOR NMR Spectrum of ACAB
pared to the ligand and are observed at 6.59—8.23 ppm, indi- observed at the same position as in ligand. However, the C7
cating that the lactone oxygen and the –NH2 moiety are not signal of hydrazide CꢂO group is shifted to 162.14 ppm
involved in coordination.
from 160.14 ppm confirming the coordination of carbonyl to
13C-NMR Spectra The 13C-NMR spectra of ACAB and metal ion. An intense peak at 150.51 ppm assigned to C1 and
its La(III) complex was carried out in DMSO-d6 and the as- C8 in ACAB undergoes a splitting into two signals appearing
signments are shown in Table 3. In spectra of ACAB, the car- at 150.51 and 152.01 ppm on complexation, indicating the
bon of lactone carbonyl is observed at 154.70 ppm. A peak at coordination of CꢂN to the metal ion. The C16 and C17 sig-
17.04 ppm is due to carbon of the –CH3 group. The methyl nal appears as a single line at 154.30 ppm in the ligand. In
carbon (Fig. 2) of the lattice held methanol appears at the complex, it splits into two lines with a new signal appear-
49 ppm. In the spectra of the La(III) complex, the signals are ing at 154.28 ppm which was earlier merged with the lactone

September 2005
1081
Table 4. UV–Visible Data of ACAB and Some Ln(III) Complexes
l
max of
lmax of
Complex
Assignments
Lnꢃ3
complex
b
Other parameters
ion (cmꢀ1
)
(cmꢀ1
)
[Nd(ACAB)2(NO3)2(H2O)2]·NO3·H2O
4I9/2—4F3/2
—2H9/2
11515
12475
13347
20292
21720
12376
22123
23324
11415
12450
13498
20145
21367
12300
22069
23314
0.9913
0.9979
1.0113
0.9927
0.9837
0.99385
0.99755
0.99957
dꢂ0.46414
b1/2ꢂ0.04806
hꢂ0.068128
—4F7/2
—2P1/2
—4G11/2
6H15/2—6F5/2
—4I15/2
[Dy(ACAB)2(NO3)2(H2O)2]·NO3·H2O
dꢂ0.301908
b1/2ꢂ0.03879
hꢂ0.05494
—4G11/2
Table 5. Inhibitory Activity of ACAB and Its Ln(III) Complexes
Fungi Bacteria
ꢁCꢂO, indicating complexation of n(CꢂN) to the metal.
Electronic Spectra The UV–Visible spectrum of the lig-
and exhibits bands at 299 and 332 nm assigned to the n–p*
transitions. The spectra of the complexes were similar with a
slight shift of spectral bands to lower energy compared to the
respective aquo ions.32) The nephelauxetic parameter (b),33)
bonding parameter (b1/2)34) and Sinha’s covalency parameter
(d)35) and angular covalency (h) for the Dy(III) and Nd(III)
complexes are presented in Table 4. The Sinha’s parameter
(d) suggests the degree of covalency and is obtained by the
equation, dꢂ(1ꢀbav)/bav ·100 where bav is the average value
of the ratio of ncomplex/naquo. The magnitude of the bonding
parameters (b1/2) suggests the degree of involvement of 4f or-
bitals in metal–ligand bonding and is related to nephelauxetic
ratio (b) by the equation, b1/2ꢂ[(1ꢀbav)/2]1/2. Angular cova-
lency (h)ꢂ(1ꢀbav)1/2/bav1/2. The intensity of the f–f transi-
tions presents an interesting observation. The intensity of the
normal f–f transitions does not show much change. However
the hypersensitive transitions (environment sensitive transi-
tions) are found to show large changes in intensity. Accord-
ing to Karraker,36) the shape and intensity of these transitions
indicate the geometry of the complex. In the present com-
plexes, nephelauxetic ratio (b) being less than one and posi-
tive values of b1/2 and d indicate slight covalent bonding be-
tween metal and ligand.
Thermal Analysis The TG/DTA curve of a representa-
tive La(III) complex suggests the following stages of decom-
position. The first step of decomposition in the temperature
range between 24—100 °C indicates the loss of a lattice held
water molecule. The observed value is in accordance with
calculated one (Obs: 1.32%, Calc: 1.77%). The next weight
loss occurs between 197—263 °C, which corresponds to the
loss of two coordinated water molecules is indicated by an
exothermic peak on the DTA curve. (Obs: 4.47%; Calc:
4.84%). The subsequent weight loss in the temperature range
263—290 °C corresponds to the loss of an ionic nitrate mole-
cule (Obs: 10.94%; Calc: 10.54%). Further weight losses in
the region 290—723 °C correspond to the loss of two coordi-
nated nitrates and two coordinated ligand molecules. Finally
it decomposes to the most stable oxide La2O3. The weight of
the residue is in good agreement with the metal contents ob-
tained by analytical measurements.
Compound
PA
BC
AN
PN
(gramꢀve) (gramꢃve)
ACAB
C1
C2
C3
C4
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃꢃ
ꢃ
ꢃ
ꢃ
ꢀ
ꢀ
ꢀ
ꢀ
ꢃ
ꢃꢃ
ꢃꢃ
ꢃꢃ
ꢃꢃ
ꢃ
C5
ꢃ
ꢀ
C6
C7
C8
C9
ꢃꢃ
ꢃꢃ
ꢃꢃ
ꢃꢃ
ꢃꢃꢃ
ꢀ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃꢃꢃ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢃꢃꢃ
ꢀ
ꢃꢃ
ꢃꢃ
ꢃꢃ
ꢃꢃ
ꢀ
Grisofulvin
Norfloxacin
Control
ꢃꢃꢃ
ꢀ
ꢀ
Key to interpretation: ꢀꢂno activity; ꢃꢂless active; ꢃꢃꢂmoderately active;
ꢃꢃꢃꢂhighly active.
gellosus (BC) by the cup-plate method.37) The concentration
used for testing was 1 mg/ml of DMSO. Grisofulvin and Nor-
floxacin were used as standards against fungi and bacteria re-
spectively. DMSO was used as the control. The cultures of
the fungi and the bacteria consisted of peptone (0.6%), yeast
extract (0.3%), beef extract (0.13%) and nutrient agar. The
nutrient agar further consisted of definite volumes of peptone
(0.5%), yeast extract (0.15%), beef extract (0.15%), NaCl
(0.35%), dipotassium phosphate (0.36%) and potassium di-
hydrogen phosphate (0.13%).
Wells were made by scooping out the nutrient agar with a
sterile cork borer. The solutions of the test compounds
(0.1 ml) were added to the wells using sterile pipettes. The
plates were further incubated for 37 °C for 48 h. The antimi-
crobial activity was estimated on the basis of size of inhibi-
tion zone formed around the wells in the plates.
The ligand ACAB was less active against both the fungi
and bacteria. In case of AN, the Gd(III), Tb(III), Dy(III) and
Y(III) complexes showed enhanced activity compared to the
ligand whereas the remaining complexes showed equal activ-
ity. In case of PN, Nd(III) complex showed enhanced activity
compared to ligand. The complexes were inactive against PA
compared to ligand. This inactivity stems from the higher
lipid content in the cell membrane of PA compared to BC
which prevents easy diffusion of complex into the cell. The
complexes exhibited moderate activities against BC com-
pared to the ligand and Eu(III) complex which were less ac-
Biological Evaluation The biological activity of the lig-
and and complexes (Table 5) was screened simultaneously
with metal salts, and the standards, against the fungi As-
pergillus niger (AN) and Penicillium notatum (PN) and the
bacteria Pseudomonas aeruginosa (PA) and Bacillus cirrofla-

1082
Vol. 53, No. 9
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