Microwave-assisted synthesis of novel 4-N,N-dimethylamino- and 4-cycloamino-substituted 1,2,4-triazole-3-thiones

Article abstract of DOI:10.1002/hc.20593

4-N,N-Dimethylamino- and 4-cyclo- amino-5-phenyl-1,2,4-triazole-3-thiones 1-13 have been synthesized from benzhydrazides and substituted methyl dithiocarbazates under various conditions including short microwave irradiations. The last method seemed faster than the classical refluxing one. The influence of base and solvent types on the reaction direction has been also examined.

Full text of DOI:10.1002/hc.20593

Heteroatom Chemistry
Volume 21, Number 3, 2010
Synthesis, Characterization, Antifungal,
Antibacterial, and Antitumor Activities of Some
Tris(pentafluorophenyl)arsenic(V) Derivatives
Rahul Mishra,1 Kiran Singhal,1 Ashok Ranjan,2 A. K. Saxena,2
and Prem Raj1
1Department of Chemistry, University of Lucknow, Lucknow 226 007, India
2Defence Material and Stores Research; Development Establishment,
G. T. Road, Kanpur 208 013, India
Received 13 September 2009; revised 24 February 2010
cept for a few scattered references, they have not
ABSTRACT: A series of tris(pentafluorophenyl)
drawn attention probably because of the difficulty
encountered in their preparation coupled with high
toxicity of arsenic itself [1–7]. Inorganic and organic
derivatives of arsenic are well-known antimicrobial
arsenic(V) derivatives of the type (C6F5)3AsL2,
(C6F5)3As(Cl)(L) [L = OCOC6H4(o-OH), OCOC-
(OH)(C6H5)2, and 2-(6-OCH3C10H6)CH(CH3) COO ],
O
agents and even can cure solid tumor [8]. The activ-
ity is significantly affected by the nature of organic
group bound to arsenic and oxidation state of metal
[8]. The partially or fully fluorine-substituted organic
group(s) bound to metal, together with chloro sub-
stituents, is known to enhance the solubility of water
and lipids, which could enhance their in vitro and in
vivo activities [9]. Moreover, it may be noticed that
organometallic carboxylates with fluoro substituents
exhibit significant biological activity [8,9].
(C6F5)3As O C(O) CHR
and cycloarsenates,
(R =
C6H5, p-CF3C6H4, and p-OCH3C6H4) have been iso-
lated and characterized by elemental analysis and
spectroscopic data (infrared; H, 19F, and 13C NMR).
1
These compounds were screened for their in vitro an-
tifungal, antibacterial, and antitumor activities and
were found to show moderate to significant activ-
ꢀ
C
ity.
2010 Wiley Periodicals, Inc. Heteroatom Chem
21:181–187, 2010; Published online in Wiley InterScience
(www.interscience.wiley.com). DOI 10.1002/hc.20593
In this paper, we report the synthesis of hitherto
unreported tris(pentafluorophenyl)arsenic(V) dicar-
boxylates, (halo)carboxylates, and cycloarsenates
with a view to establish the mode and nature of
bonding of carboxylate group(s) and their capabil-
ity to form ring compounds coupled with the twin
objectives to ascertain their biological efficacy. The
latter objective prompted us to employ biologically
active moieties. The newly synthesized compounds
INTRODUCTION
In sharp contrast to hydrocarbon ligand–based
organoarsenic derivatives, those bearing pentafluo-
rophenyl group(s) have not been much studied. Ex-
1
Correspondence to: Kiran Singhal; e-mail: singhal.kiran@
gmail.com.
Contract grant sponsor: Council of Scientific and Industrial
Research, New Delhi, India.
were characterized by solid-state infrared (IR), H,
19F, and 13C NMR spectra. Solution-phase studies
complementary these have been carried out to es-
tablish their behavior in solution. The compounds
were assayed in vitro for their antibacterial, antifun-
gal, and antitumor activities.
Contract grant number: 01/(1923)04/EMR-II.
Contract grant number: 09/107(0242)/2002-EMR-I [SRF (NET)
to Rahul Mishra].
c
ꢀ
2010 Wiley Periodicals, Inc.
181

182 Mishra et al.
RESULTS AND DISCUSSION
of formation of [Et3N·HCl], amount of silver chlo-
ride formed, melting points, elemental analysis, and
superimposable IR spectra. In the 1:2 molar ratio re-
action, the unreacted silver salts of carboxylic acid
in stoichiometric amount was also obtained.
Compounds 1–9 are off-white/brownish solid
and are freely soluble in most of the organic sol-
vents but are insoluble in petroleum ether and
n-hexane. They are monomeric in freezing ben-
zene and show nonelectrolyte behavior in acetoni-
trile. Their analytical data are given in Table 1.
In an atmosphere of nitrogen under anhydrous
conditions, interaction of tris(pentafluorophenyl)-
arsenic(V) dichloride, (C6F5)3AsCl2, with silver salt
of corresponding carboxylic acid in 1:2 molar ra-
tio yielded tris(pentafluorophenyl)arsenic(V) dicar-
boxylate [Eq. (1)].
(C6F5)3AsCl2 + 2AgL −→ (C6F5)3As(L)2 + 2AgCl
(1)
where
β
H3C
O
O
α
1′
8′
5′
1′
CH C
8′′
4′′
OH
i′
7′
O
O
C
i′
O
2′
3′
2′
3′
O
3′
C
C
α
L =
H3CO 6′
Ph
4′
β
1′
O H
2′
2-(6-OCH3C10H6)CH(CH3)COO– 3
–OCOC(OH)(C6H5)2 2, and
–OCOC6H4(o-OH) 1,
A 1:1 molar ratio interaction of (C6F5)3AsCl2
with the silver salt of carboxylic acid afforded
(chloro)carboxylate derivative of pentafluoropheny-
larsenic(V) [Eq. (2)].
Infrared Spectra
Infrared spectra of pentafluorophenylarsenic(V) car-
boxylates 1–9 were recorded in solid state with KBr
pellets and are listed in Table 2. The characteristic
absorptions associated with the pentafluorophenyl
groups bound to arsenic correspond well with those
reported earlier [10–12]. As C stretching frequency
corresponding to y-mode appears in the range
497–449 cm−1 as a medium to strong peak. The
β-OH group in compounds 1 and 4 and α-OH group
in compounds 2 and 5 do not participate in the
reaction, as has been observed by the appearance of
ν(O H) band in the IR spectra, whereas the disap-
pearance of ν(O H) peak from the spectra of com-
pounds 7–9 shows its participation in bonding. On
(C6F5)3AsCl2 + AgL −→ (C6F5)3As(Cl)(L) + AgCl
(2)
where
L = OCOC6H4(o-OH) 4; OCO(OH)(C6H5)2 5;
and 2-(6-OCH3C10H6)CH(CH3)COO
6
In sharp contrast this, both 1:1 and 1:2 molar re-
actions of (C6F5)3AsCl2 with corresponding silver salt
of mandelic acid, p-(trifluoromethyl) mandelic acid,
and p-methoxy mandelic acid afforded cycloarsen-
ates [Eq. (3)].
O
R
O
THF
.
+ AgCl + Et3N HCl
(C6F5)3As
(3)
(C6F5)3AsCl2 + AgL / 2AgL
Et3N
O
where
the other hand, the νasym(OCO) frequency appears in
the range 1727–1659 cm−1 and the corresponding
νsym(OCO) appears in the range 1460–1323 cm−1. The
magnitude of difference [ꢀν(OCO) = νasym(OCO) −
νsym(OCO)] clearly indicates that the carboxylate
moiety behave as a unidentate ligand [6,13–17].
The appearance of νasym(OCO) absorption band rela-
tively at higher frequency may be attributed to the
changed electronic behavior because of pentafluoro-
phenyl ring.
OH
O
O
3′
i′
i.e. –OCOCH(OH)(C6H4R)
L =
R
C C
α
H
1′
2′
(R = –H 7; –CF3 8; and –OCH3 9)
The change in molar ratio or solvent did not af-
fect the nature of compounds 7–9. The formation
of cycloarsenates was also established on the basis
Heteroatom Chemistry DOI 10.1002/hc

Synthesis, Characterization, and Biological Activity of Tris(pentafluorophenyl)arsenic(V) Derivatives 183
TABLE 1 Some Physical and Analytical Data of Pentafluorophenylarsenic(V) Carboxylates
Elemental Analysis
(%):Found (Calculated)
Compound
Molecular Formula
Molecular Weight
M.P. (◦C)
Yield (%)
C
H
1
2
3
4
5
6
7
8
9
C32H10AsF15O6
C46H22AsF15O6
850.32
1030.04
1034.59
748.66
838.78
840.79
800.26
868.26
830.28
146
124
126
118
116
114
102
72
68
74
59
66
74
60
65
66
63
45.29 (45.20)
53.62 (53.61)
53.38 (53.40)
40.13 (40.11)
45.90 (45.82)
45.67 (45.71)
42.11 (42.02)
40.09 (40.13)
42.06 (41.95)
1.08 (1.19)
2.09 (2.15)
2.57 (2.53)
0.64 (0.67)
1.25 (1.32)
1.60 (1.56)
0.98 (1.01)
0.89 (0.81)
1.15 (1.21)
C46H26AsF15O6
C25H5AsClF15O3
C32H11AsClF15O3
C32H13AsClF15O3
C28H8AsF15O6
C29H7AsF18O6
C29H10AsF15O7
88
1H NMR Spectra
19F NMR Spectra
The 1H NMR spectra of compounds 1–9 were
recorded in CDCl3 on a 300-MHz instrument, us-
ing TMS as the reference. The chemical shift values
are summarized in Table 3. In compounds 1 and
4, the phenyl protons appeared as multiplet in the
range δ = 6.86–7.84 ppm. The phenyl protons in the
case of compounds 2 and 5 were centered around
δ = 7.43 ppm as multiplet. The α-hydrogen for com-
pounds 7–9 appeared as singlet in the range δ = 5.38–
5.51 ppm, whereas in the case of compounds 3 and
6, it was detected at higher field in the range δ =
3.84–3.86 ppm as multiplet because of the presence
of CH3 group on the α-carbon atom. The OCH3
proton signals appeared at δ = 1.57 and 1.58 ppm,
respectively. The α-naphthyl ring protons for com-
pounds 3 and 6 were observed in the range δ = 7.14–
7.71 ppm. The OH proton signals of COOH group
disappeared in all the compounds, indicating the for-
mation of arsenic(V) carboxylates [18–20].
The 19F NMR spectra of compounds 1, 2, and 6–
9 were recorded in CDCl3 on a 300-MHz instru-
ment, using CF3COOH as reference (Table 3). The
p-F signals may easily be identified because of its
half intensity as compared with the signals of m-
F and o-F. The p-F signals also split into a triplet
because of the m-F coupling, although expected fur-
ther splitting as triplet of triplet because of o-F cou-
pling was not observed in these compounds. The
m-F and o-F signals appeared as triplet and doublet,
respectively. m-F chemical shift appeared at higher
field than of o-F and p-F chemical shifts, indicat-
ing the donation of electron from ortho- and para
positions toward carbon attached to arsenic atom
[21]. This observation is in accordance with previous
studies that the ipso-carbon of perfluorinated ben-
zene ring experience high electron density because
of diminished inductive effect of fluorine atom and
donation of electron density from the unshared p-
electron of fluorine to the π-system of the ring (p-π
interaction) [5,6,12,17,21]. The CF3 group in com-
pound 8 gave one signal at δ = −65 ppm, which
further confirms the coordination of ligand to the
metal.
TABLE 2 Characteristic IR Absorption Bands (cm−1) of
Pentafluorophenylarsenic(V) Derivatives
ν(OCO)
Compound
ν
ν
ꢀν ν(O H) ν(As C)
asym
sym
13C NMR Spectra
1
2
3
4
5
6
7
8
9
1659 (s) 1323 (m) 336 3248 (m) 464 (s)
1719 (vs) 1368 (w) 351 3399 (s) 478 (m)
1710 (s) 1450 (w) 300
1664 (s) 1330 (m) 334 3250 (m) 464 (m)
1719 (s) (o) 3400 (s) 459 (m)
1727 (s) 1420 (w) 307
1719 (s) (o)
The 13C NMR spectra of compounds 1–9 were
recorded in CDCl3 on a 300-MHz instrument
(Table 4). In every case, i-C, δ = 100.0–101.7 ppm
at pentafluorophenyl ring (i.e., As C), was more
shielded than o-C, δ = 152.0–152.7 ppm, m-C, δ =
126.1–126.8 ppm, and p-C, δ = 145.0–146.1 ppm.
The order of chemical shift was as follows: o-C >
p-C > m-C > i-C. It is evident from the 13C NMR
data that there is an invariable lower field shift of
–
483 (s)
–
–
–
–
–
448 (s)
495 (m)
485 (m)
453 (s)
–
1723 (s) 1440 (w) 283
1675 (s) 1460 (m) 215
Abbreviations: vs, very strong; s, strong; m, medium; w, weak;
o, obscured.
Heteroatom Chemistry DOI 10.1002/hc

184 Mishra et al.
TABLE 3 1H and 19F NMR Data of Pentafluorophenylarsenic(V) Derivatives
1H NMR δ (ppm)
19F NMR δ (ppm)
Compound
α-H
β-H
OCH3
Phenyl
Naphthyl
o-F
m-F
p-F
1
2
3
4
5
6
7
8
9
–
–
–
–
–
–
6.86–7.80 (m)
6.57–7.52 (m)
–
6.86–7.84 (m)
6.58–7.54 (m)
–
7.22–7.48 (m)
7.33–7.54 (m)
7.40–7.58 (m)
–
–
−132(d)
−127(d)
–
−161(t)
−162(t)
–
−143(t)
−142(t)
–
3.84 (m)
–
1.57 (d)
3.91 (s)
7.14–7.70 (m)
–
–
–
–
–
–
–
–
–
–
–
–
–
3.91 (s)
–
3.86 (m)
5.51 (s)
5.41 (s)
5.38 (s)
1.58 (d)
7.14–7.71 (m)
−131(d)
−133(d)
−131(d)
−133(d)
−157(t)
−155(t)
−156(t)
−155(t)
−142(t)
−141(t)
−141(t)
−141(t)
–
–
–
–
–
–
–
3.79 (s)
Abbreviations: s, singlet; d, doublet; t, triplet; m, multiplet.
all the pentafluorophenyl ring carbon centers be-
cause of the decrease in the electronegativity of the
ligands [18]. Because of this, the pentafluorophenyl
ring carbon centers of compounds 1–3 experience
higher field shift than their respective chloro deriva-
tives 4–6. The i-C center felt significant change where
the electron density seems decreased while replacing
strong electronegative chlorine atom with carboxy-
late group. These data are in conformity to 19F NMR
data. The chemical shift values of the carbon cen-
ters of ligands show marginal difference from the
carbon of free carboxylic acids. The position of car-
boxylate carbon in all compounds 1–9 shifts to lower
field than that of the free acid, indicating the partic-
ipation of carboxylate group in coordination with
arsenic.
Antifungal Activity
The antifungal activity of (C6F5)3As, (C6F5)3AsCl2,
and compounds 1–9 was evaluated against As-
pergillus flavus and Aspergillus niger at 10 μg mL−1
of the test compound and the percent inhibition was
calculated by the colony diameter of control and test
samples (Table 5). (C6F5)3As does not show any activ-
ity against A. flavus but show 30% inhibition against
A. niger. On the other hand, (C6F5)3AsCl2 is signifi-
cantly active against former strain (65% inhibition)
but less active against the latter strain. It appears
that the presence of two chlorine atoms bound to
arsenic enhances activity. The salicylic acid deriva-
tives 1 and 4 were moderately active against both the
strains. It is surprising that benzylic acid derivatives
TABLE 4 13C NMR Data of Pentafluorophenylarsenic(V) Derivatives in δ (ppm)
Compound
13C NMR
1
2
3
4
5
6
7
8
9
C
m-C
152.4
126.7
145.8
152.0 152.1
126.6 126.1
145.0 145.0
152.7
127.1
146.1
152.9 152.2 152.4 152.7 152.7
126.9 126.1 126.8 126.8 126.3
145.8 145.1 145.1 145.2 145.2
p-C
1ꢁ-C
130.4 and 161.1 (OH) 127.9 127.2 130.6 and 161.2 (OH) 128.0 127.2 128.0 126.2 129.7
2ꢁ-C
118.2 and 117.0
127.2 119.0
127.2 129.3
118.4 and 117.1
127.4 119.1 126.2 126.2 128.1
127.4 129.3 127.2 128.1 129.0
3ꢁ- and 8ꢁ-C
4ꢁ-C
134.6
–
–
–
134.9
–
–
–
–
–
–
–
–
105.7
126.2
157.7
136.0
135.2
–
–
–
–
–
105.7
126.2
157.8
136.1
135.2
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
5ꢁ- and 7ꢁ-C
6ꢁ-C
4ꢁꢁ-C
8ꢁꢁ-C
>C O
i-C
–
–
–
173.6
100.1
114.8
–
–
–
–
173.9
100.3
114.8
–
–
–
174.7 182.0
100.4 100.0
175.3 182.1 174.1 173.0 175.0
101.6 100.1 101.5 101.7 101.7
iꢁ-C
α-C
β-C
CF3
134.0
81.5
–
–
–
–
134.3
81.7
–
–
–
–
139.3 140.1 140.2
45.1
18.2
–
45.1
18.2
–
73.4
73.2
–
77.0
–
–
–
–
125.0
–
–
53.1
OCH3
–
55.3
–
55.3
Heteroatom Chemistry DOI 10.1002/hc

Synthesis, Characterization, and Biological Activity of Tris(pentafluorophenyl)arsenic(V) Derivatives 185
TABLE 5 Biological Activity of Pentafluorophenylarsenic(III) and Pentafluorophenylarsenic(V) Derivatives
Antimicrobial Activity
Antitumor Activity
Antifungal
Aspergillus flavus
Antibacterial
Aspergillus niger
Colony
Diameter (cm)
Inhibition
Colony
Diameter (cm)
Inhibition Staphylococcus
Klebsiella
Cell
Compound
(%)
(%)
aureus
pneumoniae Count × 104 Activity
(C F5) As
–
–
1.4
1.4
1.3
–
1.7
1.4
1.7
1.3
1.4
–
30
30
35
–
15
30
15
35
30
–
–
+ + +
++
+
++
(C6F5)3AsCl
0.7
1.2
1.7
–
1.4
1.3
1.4
1.3
1.6
1.7
2.0
65
40
15
–
30
35
30
35
20
15
–
++
++
–
10.72 1.28
10.17 0.67
09.93 0.88
09.29 0.62
09.85 0.94
09.34 0.58
10.19 0.96
10.12 0.67
10.33 1.13
10.34 1.22
Positive:
–
+
+
+
+
+
+
+
–
6
3
2
1
2
3
4
5
6
7
8
9
++
++
+
++
++
+
–
+
++
++
+
–
1.7
2.0
15
–
+
+
–
Control
–
–
40.28 3.29
Negative:
10.22 1.25
2 and 5 exhibit little activity and compound 2 was
found inactive against A. niger. Again, compounds 7–
9 showed moderate to poor activity against both the
strains. The naproxene derivative 3 showed moder-
ate activity, whereas derivative 6 was inactive against
A. flavus and poorly active against A. niger.
poor activity against K. pneumoniae and no activity
against S. aureus.
Antitumor Activity
The in vitro antitumor activity of compounds 1–9
along with (C6F5)3As and (C6F5)3AsCl2 was carried
out against human breast adenocarcinoma cell line
(MCF-7) (Table 5). (C6F5)3As and (C6F5)3AsCl2 did
not show any activity, whereas compounds 1, 2, and
7 exhibited low activity. Again, compounds 8 and 9
were inactive and compounds 3 and 6 showed poor
activity.
Antibacterial Activity
All the studied pentafluorophenylarsenic(V) deriva-
tives of carboxylic acids 1–9 along with (C6F5)3As
and (C6F5)3AsCl2 were screened for their in vitro an-
tibacterial activity against two human pathogenic
strains, namely, Staphylococcus aureus and Kleb-
siella pneumoniae (Table 5). (C6F5)3As does not show
any activity against S. aureus but showed moder-
ate activity against K. pneumoniae. Compounds 1
and 4 along with (C6F5)2AsCl2 were moderately ac-
tive against K. pneumoniae. (C6F5)2AsCl2 shows sig-
nificantly higher activity against S. aureus. It seems
that the introduction of chlorine atom significantly
enhances antibacterial activity because of the par-
tial ionic character of chlorine atom in (C6F5)3AsCl2
[12]. Surprisingly, compound 2 was markedly inac-
tive against K. pneumoniae and poorly active against
S. aureus. Compounds 3 and 7–9 were moderately
active against both the strains, but compounds 8 and
9 were poorly active and compound 8 showed no in-
hibition against K. pneumoniae. Compound 3 was
moderately active, whereas compound 6 exhibited
EXPERIMENTAL
Pentafluorophenylarsenic(V) and its dichloride were
prepared by reported method [1,2]. Naproxene, a
nonsteroidal anti-inflammatory drug, was procured
in the form of tablets (500 mg/tablet) and ex-
tracted;m.p. 156◦C). The carboxylic acids (all from
Aldrich) were used in the form of their silver salts.
IR spectra were recorded in solid state, us-
ing KBr pellets, on FT-IR spectrophotometer
(Schimadzu 8201 PC, Shimadzu Corporation Kyoto,
1
Japan) over the spectral range 4000–400 cm−1. H,
19F, and 13C NMR spectra were recorded on a Bruker
spectrometer (Bruker Corporation, US), using TMS,
CF3COOH, and CDCl3 as references, respectively.
The stoichiometry of compounds was established by
elemental analysis on a semimicro scale using an
Heteroatom Chemistry DOI 10.1002/hc

186 Mishra et al.
(10 μg mL−1 in ethanol) was placed on the nutri-
ent agar plate at 37◦C for 72 h. The inhibition zone
around the dried impregnated discs was measured
after 72 h. The activity was classified as “highly active
(+ + +)” (diameter = 10–15 mm), “moderately active
(++)” (diameter = 5–10 mm), “slightly active (+)”
(diameter ꢂ 5 mm), and “inactive (−)” (diameter <
5 mm).
The human breast cancer cell line (MCF-7)
was incubated with test compounds at dosages of
1.0 μg mL−1 for 96 h and the cell growth count
was measured by the MTT [3-(4,5-dimethylthiazol-
2-yl)-2,5-diphenyltetrazolium bromide] assay [25].
17-β-Estradiol and the culture medium were used
as the positive control and the negative control,
respectively. The MTT was dissolved in phosphate
buffer solution at a concentration of 5 mg mL−1. The
50 μL of the MTT solution was added to each well
and mixed thoroughly to dissolve the crystals of the
purple-colored zone. The plates were then read on
a microplate reader at a wavelength of 670 nm. The
readings were presented as optical density.
elemental analyzer (Elementar Vario EL III, Carlo
Erba 1108, Milan, Italy).
Synthesis of (C6 F5)3As(OCOC6 H4(o-OH))2 (1)
A solution of tris(pentafluorophenyl) arsenic(V)
dichloride (0.646 g, 1.0 mmol) and freshly pre-
pared anhydrous silver salt of salicylic acid (0.490 g,
2.0 mmol) in dry THF (30 mL) was stirred in an
atmosphere of nitrogen under anhydrous and dark
conditions at room temperature for 24 h. The white
precipitate of AgCl thus formed was filtered off. The
filtrate on concentration under vacuum followed by
the addition of n-hexane afforded off-white amor-
phous solid 1. The product was recrystallized from
a mixture of THF and n-hexane (1:2); yield 0.578 g
(68.0%); m.p. 146◦C.
O
(7)
Synthesis of
(C6F5)3As O C(O) CH(C6H5)
A
solution of tris(pentafluorophenyl)arsenic(V)
dichloride (0.646 g, 1.0 mmol), silver salt of mandelic
acid (0.518 g, 2.0 mmol) and triethylamine (0.2 mL)
in THF (30 mL) was stirred in an atmosphere of
nitrogen under anhydrous and dark conditions at
room temperature for 24 h. The solid mixture of sil-
ver chloride, [Et3N·HCl], and unreacted silver salt
of carboxylic acid was filtered off. The filtrate on
concentration in vacuo followed by the addition of
petroleum ether (60–80◦C; 2 mL) yielded off-white
amorphous solid 7. The product was crystallized
from a mixture of petroleum ether (60–80◦C) and
dichloromethane (4:1); yield 0.472 g (65.0%); m.p.
102◦C.
CONCLUSIONS
Thus, from the IR and NMR (1H, 19F, and 13C) spec-
tral studies aided by molecular weight and conduc-
tance measurements, it is evident that carboxylic
acids behave as monodentate ligands. This may
be attributed to the presence of pentafluorophenyl
ring resulting in the donation of electron density
from unshared p-electrons of fluorine to π-system
ring and thus increasing electron density at ipso-
carbon, which ultimately decreases the Lewis acid
character of the central metal atom and decreases
the tendency to accept the electron from the lig-
ands. Thus, in these newly synthesized carboxylates,
the arsenic is in pentacoordinated state imparting
trigonal-bipyramidal (TBP) structure around the ar-
senic atom, in which electronegative groups occupy
apical positions and the three C6F5 groups are sit-
uated at the equatorial positions (Fig. 1). The pre-
ferred geometry of five-coordinate group 15 ele-
ments is TBP, which is a fluxional, stereochemically
nonrigid, or pseudorotating arrangement rapidly
interconverting to square-pyramidal structures
(Fig. 2). This has been established in case of anti-
mony [20], and the same is expected for pentafluo-
rophenylarsenic(V) carboxylates resulting in the for-
mation of cycloarsenates.
Biological Activity
The antifungal activity of compounds was tested
by potato dextrose agar plate diffusion method [22]
with 10 μg mL−1 of test compound against A. niger
and A. flavus. The percentage inhibition of com-
pounds was calculated by reported method [23].
C − T
Percentage inhibition =
× 100
C
where C is the diameter of fungus in control and T
the diameter of fungus in test compounds.
Antibacterial activity of compounds was de-
termined by disc-diffusion method [24]. The ster-
ile disc of 5-mm diameter of filter paper (What-
man No. 1) impregnated with the test compound
To investigate the efficacy of the synthesized
pentafluorophenyl arsenic(V) derivatives of car-
boxylic acids, an attempt is being made to correlate
their antitumor and antimicrobial activities. From
Heteroatom Chemistry DOI 10.1002/hc

Synthesis, Characterization, and Biological Activity of Tris(pentafluorophenyl)arsenic(V) Derivatives 187
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ACKNOWLEDGMENTS
The authors are grateful to National Botanical
Research Institute, Lucknow, India, for measuring
biological activity of compounds, and Regional So-
phisticated Instrumentation Centre, Central Drug
Research Institute, Lucknow, India, for microana-
lytical and spectral data.
Heteroatom Chemistry DOI 10.1002/hc