Organotin(IV) Complexes with 2-acetylpyridine benzoyl hydrazones: Antimicrobial activity

Article abstract of DOI:10.1590/S0103-50532010000700012

Reaction of n-butyltin trichloride, [BuⁿSnCl₃], and phenyltin trichloride, [PhSnCl₃], with 2-acetylpyridine benzoyl hydrazone (H2AcPh), 2-acetylpyridine para-chloro-benzoyl hydrazone (H2AcpClPh) and 2-acetylpyridine para-n

Full text of DOI:10.1590/S0103-50532010000700012

J. Braz. Chem. Soc., Vol. 00, No. 00, 1247-1257, 2010.
Printed in Brazil - ©2010 Sociedade Brasileira de Química
0103 - 5053 $6.00+0.00
Organotin(IV) Complexes with 2-Acetylpyridine Benzoyl Hydrazones:
Antimicrobial Activity
Angel A. R. Despaigne,a,# Lorena F. Vieira,a Isolda C. Mendes,a
Fernanda B. da Costa,a Nivaldo L. Spezialib and Heloisa Beraldo*,a
aDepartamento de Química and bDepartamento de Física, Universidade Federal de Minas Gerais,
31270-901 Belo Horizonte-MG, Brazil
Reações de tricloreto de n-butilestanho, [BunSnCl3], e tricloreto de fenilestanho, [PhSnCl3],
com 2-acetilpiridina benzoil hidrazona (H2AcPh), 2-acetilpiridina-para-cloro-benzoil hidrazona
(H2AcpClPh) e 2-acetilpiridina-para-nitro benzoil hidrazona (H2AcpNO2Ph) produziram os
complexos [BunSn(2AcPh)Cl2] (1), [BunSn(2AcpClPh)Cl2] (2), [BunSn(2AcpNO2Ph)Cl2] (3),
[PhSn(2AcPh)Cl2] (4), [PhSn(2AcpClPh)Cl2] (5) e [PhSn(2AcpNO2Ph)Cl2] (6). H2AcpClPh
revelou-se a hidrazona mais ativa contra Staphylococcus aureus e Candida albicans. Pela
coordenação a atividade antibacteriana tanto do metal quanto das hidrazonas aumenta
significativamente. Os complexos 2 e 5 revelaram-se os mais ativos como agentes antimicrobianos.
Reaction of n-butyltin trichloride, [BunSnCl3], and phenyltin trichloride, [PhSnCl3], with
2-acetylpyridine benzoyl hydrazone (H2AcPh), 2-acetylpyridine para-chloro-benzoyl hydrazone
(H2AcpClPh) and 2-acetylpyridine para-nitro-benzoyl hydrazone (H2AcpNO2Ph) gave
[BunSn(2AcPh)Cl2] (1), [BunSn(2AcpClPh)Cl2] (2), [BunSn(2AcpNO2Ph)Cl2] (3), [PhSn(2AcPh)
Cl2] (4), [PhSn(2AcpClPh)Cl2] (5) and [PhSn(2AcpNO2Ph)Cl2] (6) as products. Among the
hydrazones H2AcpClPh proved to be the most active against Staphylococcus aureus and Candida
albicans. Upon coordination the antibacterial activity of both tin and the hydrazones significantly
increases. Complexes 2 and 5 revealed to be the most active as antimicrobial agents.
Keywords: 2-acetylpyridine benzoyl hydrazones, organotin(IV) complexes, crystal structures,
antimicrobial activity
Introduction
potential applications as catalysts,12 luminescent probes,13
and molecular sensors.14 Moreover, metal complexes with
hydrazones present antimicrobial,15-17 DNA-binding and
cytotoxic activities.17 It has also been shown that metal
complexes with hydrazones can be potent inhibitors of cell
growth and DNA syntheses.18
TincompoundspresentapplicationsasPVCstabilizers,19
for chemical vapor decomposition (CVD),20 in non-linear
optics21 and in catalyses.22 Organotin complexes present
innumerous pharmacological applications as antitumorals,23
antimicrobials24,25 and biocides.26 The cytotoxic activity of
a variety of organotin complexes against tumor cell lines
has been demonstrated by some of us.27,28
Hydrazones are a versatile class of compounds
which present a wide range of biological applications
as antimicrobial,1 antitubecular,2 anticonvulsant,3 anti-
inflammatory,4 cytotoxic5 and vasodilator6 agents.
Moreover, 9-acridanone-hydrazones proved to be active
against Schistosoma mansoni7 and quinoxaline-N-
acylhydrazones showed trypanocidal activity.8 In addition,
methyl pyrazinylketone isonicotinoyl hydrazones have been
synthesized in an attempt to develop novel chelators with
high affinity for iron for the treatment of iron overload
disease.9
Hydrazones also proved to be useful as sensitive
analytical reagents for the determination of trace amounts
of metal ions.10,11 Metal complexes with hydrazones have
In recent works we started an investigation on metal
complexesofpyridine-derivedhydrazones.29-31 Inthepresent
paper organotin(IV) complexes were prepared by reacting
[BunSnCl3] and [PhSnCl3] with 2-acetylpyridine-benzoyl
hydrazone (H2AcPh), 2-acetylpyridine para-chloro-
benzoyl hydrazone (H2AcpClPh) and 2-acetylpyridine
*e-mail: hberaldo@ufmg.br
#On leave from Universidad de Oriente, Santiago de Cuba, Cuba

1248
Organotin(IV) Complexes with 2-Acetylpyridine Benzoyl Hydrazones: Antimicrobial Activity
J. Braz. Chem. Soc.
para-nitro-benzoyl hydrazone (H2AcpNO2Ph) (see
Figure 1). The antimicrobial activity of the hydrazones
and their organotin(IV) complexes was evaluated against
Candida albicans and Staphylococcus aureus.
(H2AcpClPh) were prepared as described in the
literature.32,33 2-Acetylpyridine-para-nitro-benzoyl
hydrazone (H2AcpNO2Ph) was obtained by mixing
equimolar amounts of 2-acetylpyridine with the para-nitro-
benzoyl hydrazide in methanol with addition of three drops
of acetic acid as catalyst. The reaction mixture was kept
under reflux for 6 h. After cooling to room temperature the
resulting solid was filtered off, washed with ethanol and
ether and dried in vaccuum.
H2AcpNO2Ph: Color: Beige; Yield: 88%; mp
220-224 °C. Selected IR bands (nmax/cm-1): n(NH) 3188 m;
n(C=O) 1676 s; n(C=C) + n(CN) 1580 m; 1458 m; 1429 m;
r(py) 615 m. 1H NMR (dmso-d6, 400 MHz, d ppm): 11.21
(s, 1H, NH); 8.64 (d, 1H, H6); 8.38 [d, 2H, H(11,13)]; 8.19
[d, 2H, H(10,14)]; 8.16(d,1H, H3); 7.91 (t, 2H, H4); 7.47(t,
1H, H5); 2.50 (s, 3H, CH3). 13C NMR (dmso-d6, 400 MHz,
ppm): d 162.69(C6); 154.76 (C7); 149.10 (C2); 148.57(C6);
139.61(C12); 136.61 (C4); 134.06(C9); 129.52(C10,14);
124.25 (C5); 123.30(C11,13); 120.43 (C3).
Figure 1. Generic structure of 2-acetylpyridine benzoyl hydrazones (E
and Z configurational isomers).
Experimental
Apparatus
Synthesis of [BunSn(2AcPh)Cl2] (1), [BunSn(2AcpClPh)Cl2]
(2), [BunSn(2AcpNO2Ph)Cl2] (3), [PhSn(2AcPh)Cl2] (4),
[PhSn(2AcpClPh)Cl2] (5) and [PhSn(2AcpNO2Ph)Cl2] (6)
Partial elemental analyses were performed on a Perkin
Elmer CHN 2400 analyzer. Infrared spectra were recorded
on a Perkin Elmer FT-IR Spectrum GX spectrometer using
CsI pellets; an YSI model 31 conductivity bridge was
employed for molar conductivity measurements; NMR
spectra were obtained with a Bruker DPX-200 (200 MHz)
spectrometer or with a Bruker DRX-400 Avance (400
MHz) spectrometer using deuterated dimethylsulfoxide
The organotin(IV) complexes were obtained by
refluxing an ethanol solution of the desired hydrazone
with [BunSnCl3] or [PhSnCl3] in 1:1 ligand-to-metal molar
ratio. The solids were washed with ethanol followed
by diethylether and then dried in vaccuum. Crystals of
complexes 1, 2, 3 and 5 were obtained from their ethanolic
solutions and were stable in the air. Slow evaporation
of 6 in 1:9 dmso:acetone solution gave crystals of
1
(dmso-d6) or deuterated chloroform (CDCl3). The H
and 13C NMR chemical shifts in ppm are reported from
internal tetramethylsilane (tms) on the % scale. The
119Sn NMR spectra were measured relative to Sn(CH3)4.
Bruker standard experiments were performed using
decoupling sequences for 13C and 119Sn. Splitting patterns
are designated as follows: s singlet; d doublet; t triplet; q
quartet; m multiplet.
•
[PhSn(2AcpNO2Ph)Cl2] dmso, (6a).
n - B u t y l ( d i c h l o r o ) ( 2 - a c e t y l p y r i d i n e -
phenylhydrazonato)tin(IV), [BunSn(2AcPh)Cl2], (1):
Color:Yellow.Yield: 71%. Anal. Calc. (C18H21Cl2N3OSn):
C, 44.88; H, 4.36; N, 8.66. Found: C, 44.87; H, 4.16;
N, 8.96%. Selected IR bands (nmax/cm-1): n (CH3) 2952
m; ns(CH3) 2869 m; nas(CH2) 2925 m; nass(CH2) 2853
m; n(C-H)ar 3060 m; n(C=N) 1599 m; sas(CH2) 1460;
n-Butyltin trichloride, phenyltin trichloride,
2-acetylpyridine, benzoyl hidrazide, 4-chloro benzoyl
hidrazide, and 4-nitro benzoyl hidrazide were purchased
from Sigma-Aldrich and used without further purification.
All other chemicals and solvents were of analytical grade.
sas(CH3) 1421; ss(CH3) 1380; r(py) 649 m; n(M-Nimine
)
492; n(M-O) 392; n(M-C) 349; n(M-Cl) 250; n(M-Npy)
228. H NMR (CDCl3, 200 MHz, ppm): d 8.62 (d, 1H,
1
Syntheses of 2-acetylpyridine-benzoyllhydrazone
(H2AcPh), 2-acetylpyridine-para-chloro-benzoyl hydrazone
(H2AcpClPh) and 2-acetylpyridine-para-nitro-benzoyl
hydrazone (H2AcpNO2Ph)
H6); 8.34 (d, 2H, H10,14); 8.20 (t, 1H, H4); 8.01(d, 1H,
H3); 7.74 (t, 1H, H5); 7.49(m, 3H, H11,13, H12); 2.82 (s,
3H, H15); 2.33(t, 2H, H16); 2.07(m, 2H, H17); 1.61(m,
2H, H18); 1.05(t, 3H, H19). 13C NMR (CDCl3,200 MHz,
ppm): d 171.38(C8); 145.13(C6); 144.68(C7); 144.16(C2);
142.49(C4); 132.51(C12); 132.42(C9); 129.00(C10,14);
2-Acetylpyridine-benzoyl hydrazone (H2AcPh)
and 2-acetylpyridine-para-chloro-benzoyl hydrazone

Vol. 21, No. 7, 2010
Despaigne et al.
1249
128.15(C11,13); 127.05(C5); 125.06(C3); 35.50(C16);
27.51(C17); 25.60(C18); 13.68(C19); 13.53(C15).
119Sn NMR (CDCl3, 200 MHz, ppm): d -414.39. Molar
IR bands (nmax/cm-1): n(C-H)ar 3061 m; n(C=N) 1600 m;
r(py) 650 m; n(M-Nimine) 494; n(M-C) 441; n(M-O) 395;
n(M-Cl) 242; n(M-Npy) 229. 1H NMR (CDCl3, 200 MHz,
ppm) main signals: d 8.41(m, 1H, H4); 8.40(m, 1H, H6);
8.33(d, 2H, H17,21); 8.21(d, 2H, H10,14); 8.04(d, 1H, H3);
7.60(m, 1H, H5); 7.59(m, 3H, H18,19,20); 7.50(m, 1H,
-1
conductivity (1×10-3 mol L-1, dmf): 11.56 W cm2 mol-1.
n-Butyl(dichloro)(2-acetylpyridine-para-chloro-
phenylhydrazonato)tin(IV), [BunSn(2AcpClPh)Cl2], (2):
Color:Yellow.Yield: 83%. Anal. Calc. (C18H21Cl3N3OSn):
C, 41.62; H, 3.88; N, 8.09. Found: C, 41.77; H, 3.41; N,
8.39%. Selected IR bands (nmax/cm-1): nas(CH3) 2957 m;
ns(CH3) 2870 m; nas(CH2) 2928 m; ns(CH2) 2859 m; n(C-H)
ar 3081 m; n(C=N) 1599 m; sas(CH2) 1448; sas(CH3) 1448;
ss(CH3) 1386; r(py) 647 m; n(M-Nimine) 481; n(M-O) 402;
n(M-C) 360; n(M-Cl) 250; n(M-Npy) 228. 1H NMR (CDCl3,
200 MHz, ppm): d 8.63(d, 1H, H6); 8.24(d, 2H, H10,14);
8.20(m, 1H, H4); 8.02(d, 1H, H3); 7.67(t, 1H, H5); 7.44(d,
2H, H11,13); 2.81(s, 3H, H15); 2.32(t, 2H, H16); 2.08(m,
2H, H17); 1.60(m, 2H, H18); 1.05(s, 3H, H19). 13C NMR
(CDCl3, 200 MHz, ppm): d 170.50 (C8); 145.28(C6);
145.05(C7); 144.14(C2); 142.56(C4); 138.66(C12);
130.98(C9); 130.43(C11,13); 128.13(C10,14); 127.26(C5);
125.20(C3); 35.60(C16); 27.52(C17); 25.61(C18);
13.68(C19); 13.56(C15). 119Sn NMR (CDCl3, 200 MHz,
ppm): d -413.66. Molar conductivity (1×10-3 mol L-1, dmf):
13
H12); 7.44(m, 2H, H11,13); 2.88(s, 3H, H15). C NMR
(CDCl3, 200 MHz, ppm) main signals: d 171.53(C8);
145.06(C6); 144.11(C2); 142.61(C4); 139.92(C16);
136.62(C17,21); 132.59(C12); 132.16(C9); 131.13(C19);
129.08(C10,14,18,19); 128.17(C11,13); 126.99(C5);
124.04(C3); 13.45(C15). 119Sn NMR (CDCl3, 200 MHz,
ppm): d -443.37. Molar conductivity (1×10-3 mol L-1, dmf):
-1
20.51 W cm2 mol-1.
Phenyl(dichloro)(2-acetylpyridine-para-chloro-
phenylhydrazonato)tin(IV), [PhSn(2AcpClPh)Cl2] (5):
Color:Yellow.Yield: 86%. Anal. Calc. (C20H16Cl3N3OSn):
C, 44.53; H, 2.99; N, 7.99. Found: C, 43.57; H, 2.82; N,
8.04%. Selected IR bands (nmax/cm-1): n(C-H)ar 3050 m;
n(C=N) 1597 m; r(py) 647 m; n(M-Nimine) 476; n(M-C)
1
443; n(M-O) 403; n(M-Cl) 260; n(M-Npy)233. H NMR
(CDCl3, 200 MHz, ppm): d 8.42(m, 1H, H6); 8.40(m, 1H,
H4); 8.27(d, 2H, H17,21); 8.21(d, 2H, H11,13); 8.06(d, 1H,
H3); 7.63(t, 1H, H5); 7.59(m, 3H, H18,19,20); 7.41(d, 2H,
H10,14); 2.88(s, 3H, C15). 13C NMR (CDCl3, 200 MHz,
ppm): d 170.58(C8); 145.11(C6); 144.46(C7); 144.07(C2);
142.77(C4); 139.75(C16); 138.76(C12); 136.50(C17,21);
131.22(C19); 131.00(C9); 130.47(18,20); 129.13(C11,13);
128.50(C10,14); 127.12(C5); 125.04(C3); 13.47(C15).
119Sn NMR (CDCl3, 200 MHz, ppm): d -442.65. Molar
-1
14.33 W cm2 mol-1.
n-Butyl(dichloro)(2-acetylpyridine-para-nitro-
phenylhydrazonato)tin(IV), [BunSn(2AcpNO2Ph)Cl2], (3):
Color:Yellow.Yield: 74%.Anal. Calc. (C18H20Cl2N4O3Sn):
C, 40.79; H, 3.80; N, 10.57. Found: C, 40.92; H, 3.72; N,
10.48%. Selected IR bands (nmax/cm-1): nas(CH3) 2956 m;
ns(CH3) 2869 m; nas(CH2) 2927 m; ns(CH2) 2858 m; n(C-H)
ar 3077 m; n(C=N) 1596 m; sas(CH2) 1456; sas(CH3) 1443;
ss(CH3) 1384; r(py) 649 m; n(M-Nimine) 479; n(M-O)
-1
conductivity (1×10-3 mol L-1, dmf): 20.53 W cm2 mol-1.
Phenyl(dichloro)(2-acetylpyridine-para-nitro-
phenylhydrazonato)tin(IV), [PhSn(2AcpNO2Ph)Cl2], (6):
Color:Yellow.Yield: 82%.Anal. Calc. (C20H16Cl2N4O3Sn):
C, 43.68; H, 2.93; N, 10.19. Found: C, 43.23; H, 3.00;
N, 10.28%. Selected IR bands (nmax/cm-1): n(C-H)ar
1
394; n(M-C) 364; n(M-Cl) 249; n(M-Npy) 214. H NMR
(CDCl3, 200 MHz, ppm): d 8.68(d, 1H, H6); 8.49(d, 2H,
H10,14); 8.30(m, 2H, H11,13); 8.28(m, 1H, H4); 8.11(d,
1H, H3); 7.84(t, 1H, H5); 2.87(s, 3H, H15); 2.34(t, 2H,
H16); 2.05(m, 2H, H17); 1.61(m, 2H, H18); 1.05(t, 3H,
H19). 13C NMR (CDCl3, 200 MHz, ppm): 169.36(C8);
150.00(C7); 146.89(C2); 145.51(C6); 143.93(C12);
142.62(C4); 138.41(C9); 129.85(C10,14); 127.60(C5);
125.45(C3); 123.21(C11,13); 35.79(C16); 27.52(C17);
25.61(C18); 13.73(C19); 13.68(C15). 119Sn NMR
(CDCl3, 200 MHz, ppm): d -412.33. Molar conductivity
3058 m; n(C=N) 1596 m; r(py) 649 m; n(M-Nimine
)
486; n(M-C) 450; n(M-O) 394; n(M-Cl) 250; n(M-Npy)
1
231. H NMR (CDCl3, 200 MHz, ppm): d 8.50(d, 2H,
H11,13); 8.42(m, 1H, H6); 8.41(m, 1H, H4); 8.28(m,
2H, H17,21); 8.25(m, 2H; H10,14); 8.13(d, 1H, H3);
7.70(t, 1H, H5); 7.61(m, 3H, H18,19,20); 2.93(s, 3H;
H15). 13C NMR (CDCl3, 200 MHz, ppm): d 169.41(C8);
150.06(C7); 146.32(C2,C12); 145.28(C6); 142.79(C4);
139.48(C16); 138.43(C9); 136.45(C17,21); 131.36(C19);
129.99(C18,20); 129.21(C11,13); 127.56(C10,14);
125.38(C5); 123.27(C3); 13.64(C15). 119Sn NMR
(CDCl3, 200 MHz, ppm): d -441.42. Molar conductivity
-1
(1×10-3 mol L-1, dmf): 10.66 W cm2 mol-1.
Phenyl(dichloro)(2-acetylpyridine-phenylhydrazonato)
tin(IV), [PhSn(2AcPh)Cl2], (4): Color: Yellow. Yield:
85%. Anal. Calc. (C20H17Cl2N3OSn): C, 47.57; H, 3.39;
N, 8.32. Found: C, 46.66; H, 3.06; N, 8.80%. Selected
-1
(1×10-3 mol L-1, dmf): 18.75 W cm2 mol-1.

1250
Organotin(IV) Complexes with 2-Acetylpyridine Benzoyl Hydrazones: Antimicrobial Activity
J. Braz. Chem. Soc.
X-ray crystallography
atoms, except for those involved in disorder systems for
which isotropic ADP was used. Although some hydrogen
atoms could be identified in a Fourier difference map, in the
final model they were geometrically positioned and refined
using a riding model. Criteria of a satisfactory complete
analysis were the ratios of rms shift to standard deviation
less than 0.001 and no significant features in final difference
maps. Molecular graphics were obtained from ORTEP.37
A summary of the crystal’s data, experimental details and
refinement results are listed in Table 1.
Crystals of [BunSn(2AcPh)Cl2] (1), [BunSn(2AcpClPh)
Cl2] (2), [BunSn(2AcpNO2Ph)Cl2] (3), [PhSn(2AcPh)Cl2]
(4) and [PhSn(2AcpNO2Ph)Cl2] dmso (6a) were mounted
•
on glass fibers and used for data collection. X-ray diffraction
data collection was performed on a Oxford-Diffraction
GEMINI diffractometer (LabCri) using graphite-Enhance
Source MoKa radiation (l = 0.71069 Å) at 293(2) K. Data
integrationandscalingofthereflectionswereperformedwith
the Crysalis suite.34 Final unit cell parameters were based on
the fitting of all reflections positions. The structures were
solved by direct methods using the program SHELXS-9735
and refined by full-matrix least-squares techniques against
F2 using SHELXL-97.36 Positional and anisotropic atomic
displacement parameters were refined for non hydrogen
In vitro antimicrobial activity
Antimicrobial activity was evaluated by minimum
inhibitory concentration (MIC) using the macrodilution
test.38 S. aureus ATCC6538 stored in Brain Heart Infusion
Table 1. Crystal data and refinement results for [BunSn(2AcPh)Cl3] (1), [BunSn(2AcpClPh)Cl3] (2), [BunSn(2AcpNO2Ph)Cl3] (3), [PhSn(2AcPh)Cl3] (4)
•
and [PhSn(2AcpNO2Ph)Cl3] dmso (6a)
Compound
1
C18H21Cl2N3OSn
484.97
2
C18H20Cl3N3OSn
519.41
3
C18H20Cl2N4O3Sn
529.97
4
C20H17Cl2N3OSn
504.96
6a
C22H22Cl2N4O4SSn
628.09
Empirical Formula
Formula Weight
Crystal System
Space Group
orthorhombic
F d d 2
orthorhombic
F d d 2
triclinic
triclinic
monoclinic
P21/c
P–1
P–1
Unit cell dimensions
a, Å
b, Å
c, Å
a, o
b, o
27.440(4)
22.024(4)
13.316(2)
90
26.6226(17)
23.9627(18)
13.3438(7)
90
12.9843(4)
13.3554(6)
14.1000(7)
111.487(4)
94.407(3)
105.649(3)
2148.31(16)
4 / 1.639
1.464
11.4662(3)
12.5545(3)
16.2705(4)
112.147(2)
95.650(2)
101.670(2)
2084.75(9)
4 / 1.609
1.496
14.4967(4)
13.4617(4)
13.3607(3)
90
90
90
102.523(3)
90
g, o
90
90
Volume, Å3
Z / Density calc., Mg/m3
Absorption coefficient, mm–1
8047(2)
16 / 1.601
1.546
8512.7(10)
16 / 1.621
1.589
2545.31(12)
4 / 1.639
1.332
F(000)
3872
4128
1056
1000
1256
Crystal size, mm
0.27 × 0.24 × 0.12 0.29 × 0.24 × 0.18 0.28 × 0.25 × 0.10 0.24 × 0.18 × 0.09 0.19 × 0.19 × 0.05
q range for data collection, o
Index range, q
2.86 to 26.37
3.07 to 26.37
2.76 to 26.37
2.61 to 26.37
2.79 to 26.37
–34 ≤ h ≤ 31
–27 ≤ k ≤ 23
–15 ≤ l ≤ 16
–24 ≤ h ≤ 33
–29 ≤ k ≤ 29
–13 ≤ l ≤ 16
–16 ≤ h ≤ 16
–13 ≤ k ≤ 16
–17 ≤ l ≤ 16
–14 ≤ h ≤ 11
–14 ≤ k ≤ 15
–20 ≤ l ≤ 19
–18 ≤ h ≤ 18
–16 ≤ k ≤ 16
–16 ≤ l ≤ 13
Completeness to q = 26.37 o
Absorption correction
99.9%
none
99.6%
none
99.9%
none
99.9%
none
99.9%
none
Goodness-of-fit on F2
0.927
1.072
0.814
0.869
0.829
Reflections collected/unique (Rint)
12047 / 3852
(0.0647)
6718 / 3555
(0.0319)
19702 / 8769
(0.0474)
18566 / 8525
(0.0295)
14702 / 5212
(0.0447)
Absolute structure parameter
Data / restraints / parameters
Observed reflections, I > 2s(I)
Final R indices [I > 2s(I)]
0.03(5)
3852 / 11 / 224
2232
0.06(5)
3555 / 6 / 235
2405
-
-
-
8769 / 8 / 470
4288
8525 / 0 / 487
5929
5212 / 0 / 307
3261
R1 = 0.0477,
wR2 = 0.1077
R1= 0.0483,
wR2 = 0.1335
R1= 0.0442,
wR2 = 0. 0963
R1= 0.0257,
wR2 = 0.0441
R1= 0.0324,
wR2 = 0.0543
R indices (all data)
R1 = 0.0879,
wR2 = 0.1166
R1 = 0.0740,
wR2 = 0.1460
R1 = 0.1028,
wR2 = 0.1055
R1 = 0.0469,
wR2 = 0.0463
R1 = 0.0655,
wR2 = 0.0580
Larg. peak and hole, e Å–3
1.047 / -0.660
0.739 /-1.179
0.951 / -0.490
0.309 / -0.279
0.968 / -0.569

Vol. 21, No. 7, 2010
Despaigne et al.
1251
(BHI) broth were subcultured for testing in the same
medium and grown at 37 °C. Then the bacterial cells were
suspended in BHI, according to Clinical and Laboratory
Standards Institute (CLSI) guidelines,39 to produce a
suspension of about 105 CFU (colony forming units) mL-1.
C. albicans ATCC18804 stored in Sabouraud broth was
sub-cultured for testing in the same medium and grown at
37 °C. Then the yeast cells were suspended according to
the McFarland protocol39 in saline solution to produce a
suspension of about 103 cells mL-1.
For both the antibacterial and antifungal activity
evaluations serial dilutions of the compounds, previously
dissolved in dmso, were prepared in test tubes. A 24-h
old inoculum (100 mL) was added to each tube. The MIC,
defined as the lowest concentration of the test compound
which inhibits the visible growth after 20 h, was determined
after incubation at 37 °C. Tests using tetracycline (in the
case of S. aureus) or fluconazole (in the case of C. albicans)
as reference and dmso as negative control were carried out
in parallel. The final dmso concentration never exceeded
1%. In all cases no inhibition was observed with 5% v/v
dmso. All tests were performed in triplicates with full
agreement between the results.
The pyridine in-plane deformation mode at
620-625 cm-1 in the spectra of the hydrazones shifts
to 647-650 cm-1 in those of the complexes, suggesting
coordination of the heteroaromatic nitrogen.29-31
In addition, new absorptions at 495-475 cm-1 and
450-350 cm-1 have been attributed to n(Sn-Nimine) and
n(Sn–C) respectively; absorptions at 230-215 cm−1
were assigned to n(Sn-Npy),25,28,40 and bands in the
405-390 cm-1 range have been assigned to n(Sn-O).
An absorption at 260-250 cm-1 has been attributed
to n(Sn-Cl).25,28,40 Therefore, the infrared data for the
complexes indicate coordination of the hydrazones
through the Npy-N-O chelating system, as confirmed by
the X-ray structure determinations for 1-4 and 6a.
NMR spectra
The 1H and 13C NMR spectra of the hydrazones were
recorded in dmso-d6 as well as in CDCl3 except in the case
of H2AcpNO2Ph, which is insoluble in CDCl3. The spectra
of complexes 1-6 were recorded only in CDCl3 since some
of them interact with dmso-d6.
1
The H resonances were assigned on the basis of
chemical shifts, multiplicities and coupling constants. The
carbon type (C, CH) was determined by using distortionless
enhancement by polarization transfer (DEPT135)
experiments. The assignments of the protonated carbons
were made by 2D heteronuclear multiple quantum
coherence experiments (HMQC). A 119Sn NMR study was
performed for all complexes.
The NMR spectra of H2AcPh in CDCl3 show only one
signal for each hydrogen and each carbon, indicating the
presence of only one configurational isomer. The signal
of N3-H was observed at d 9.22, suggesting the presence
of the E isomer. The spectra recorded after 24 h do not
show any changes. The spectra recorded in dmso-d6 show
two signals for each hydrogen and carbon, in accordance
with the presence of the E and Z isomers (see Figure 1) in
solution.29-31 The signals of N3-H at d 10.90 and d 15.80
were attributed to the E and Z isomers respectively (97%
of E and 3% of Z). The high frequency signal of the Z
isomer is characteristic of N3-H hydrogen-bonded to the
heteroaromatic nitrogen while the signal at d 10.90 is
characteristic of N3-H hydrogen-bonded to the solvent, as
previously observed by us.29-31
Results and Discussion
Microanalyses and molar conductivity data suggest the
formation of the following complexes: [BunSn(2AcPh)Cl2]
(1), [BunSn(2AcpClPh)Cl2] (2), [BunSn(2AcpNO2Ph)Cl2]
(3), [PhSn(2AcPh)Cl2] (4), [PhSn(2AcpClPh)Cl2] (5) and
[PhSn(2AcpNO2Ph)Cl2] (6), in which an anionic hydrazone
is attached to the metal centre along with a n-butyl or a
phenyl group and the remaining coordination sites are
occupied by two chloride ions. X-ray diffraction analysis
confirms the structures of 1-4 and 6 (as its dmso solvate,
•
[PhSn(2AcpNO2Ph)Cl2] dmso, 6a).
Spectroscopic characterization
Infrared spectra
The n(N-H) and n(C=O) absorptions at 3180-3287 cm-1
and 1655-1676 cm-1 in the spectra of the uncomplexed
hydrazones were not found in the spectra of complexes
(1-6), in accordance with the presence of anionic ligands
in the products.
H2AcpNO2Ph is soluble in dmso-d6 but insoluble
1
The n(C=C) + n(C=N) composed mode observed at
1590-1460 cm-1 in the spectra of the hydrazones undergoes
small shifts in the spectra of the complexes. However a new
n(C=N) absorption due to the formation of a second C=N
bond was observed at 1625-1632 cm-1 in the spectra of 1-6,
indicating coordination of an anionic hydrazone.
in CDCl3. In the H and 13C NMR spectra (dmso-d6) of
H2AcpNO2Ph only one signal has been observed for
each hydrogen and each carbon. The signal of N3-H
was found at d 11.22, suggesting the presence of the E
configurational isomer, in which N3-H is hydrogen-bonded
to the solvent.29-31

1252
Organotin(IV) Complexes with 2-Acetylpyridine Benzoyl Hydrazones: Antimicrobial Activity
J. Braz. Chem. Soc.
The 1H and 13C NMR spectra of H2AcpClPh in dmso-d6
Npy-N-O chelating system. Hence the hydrazones adopt
the E configuration in the complexes, as confirmed by
crystal structure determinations of complexes 1-4 and 6a.
Moreover, the signal of N3-H was not observed in the 1H
NMR spectra of the complexes, according to deprotonation
of the hydrazones upon coordination.
In the spectra of complexes 1-3, new signals at d 2.35-
1.05 and at d 35.80-13.60 were attributed to the hydrogens
and carbons, respectively, of the n-butyl group attached to
the metal.28 In the spectra of complexes 4-6, the signals at
d 8.33-7.59 and at d 136.62-129.08 were attributed to the
hydrogens and carbons, respectively, of the phenyl group
coordinated to tin.40
In the 119Sn NMR spectra of complexes 1-6 (CDCl3)
only one signal was observed at d – 414 (1), d – 413 (2),
d – 412 (3), d – 443 (4), d – 442 (5) and d – 441 (6) ppm,
compatible with the presence of one tin site in solution.
The values of the 119Sn signals are at the boundary
between six- and seven-coordinated tin(IV) as reported
in the literature.42 However, considering that the spectra
were recorded in a non-coordinating solvent (CDCl3),
only six-coordinated species must be present in solution.
The shielding effect on 119Sn of the chloride ions could
explain the lower frequencies observed for the 119Sn
signals with respect to that expected for a six-coordinated
monorganotin(IV).42
show duplicated signals for the hydrogens, in accordance
with the presence of two configurational isomers. The
signals of N3-H at d 10.96 and d 15.86 were attributed to
the E (98%) and Z (2%) isomers, respectively.29-31 Due to the
low solubility of H2AcpClPh in dmso-d6 only some of the
signals of hydrogens could be attributed and no attribution
was possible for the carbons of the Z isomer.
The spectra of this compound in CDCl3 also show
duplicated signals. However in this case the spectra are
characteristic of the presence of the keto and enol forms.41
In fact no signal of N3-H was observed for the first isomer,
according to the presence of the enol form. In addition, the
signal of C-O was observed at d 167.44. The resemblance in
position of the carbon signals of H2AcpClPh with those of
H2AcPh in the same solvent suggests that the enol isomer
adopts the E configuration. As an example, the signal of
C15 (acetyl) was observed at d 11.36, close to the signal
for the same hydrogen at d 10.89 observed for the E isomer
of H2AcPh in CDCl3. The keto isomer exhibits the signal
of N3-H at d 15.83, characteristic of the Z configuration,
and the signal of C=O at d 163.40.
Only one signal was observed for each hydrogen and
each carbon in the spectra of complexes 1-6, suggesting the
presence of only one configurational isomer. The signals
of C=N, C=O and the pyridine carbons undergo significant
shifts in the complexes indicating coordination through the
Figure 2. Molecular plot of the asymmetric units of [(Bun)Sn(2AcPh)Cl2] (1), [(Bun)Sn(2AcpClPh)Cl2] (2) and [(Bun)Sn(2AcpNO2Ph)Cl2] (3) showing
the labeling scheme of the non-H atoms and their displacement ellipsoids at the 50% probability level.

Vol. 21, No. 7, 2010
Despaigne et al.
1253
•
Figure 3. Molecular plot of the asymmetric units of [PhSn(2AcPh)Cl2] (4) and [PhSn(2AcpNO2Ph)Cl2] dmso (6a) showing the labeling scheme of the
non-H atoms and their displacement ellipsoids at the 50% probability level.
X-ray diffraction analysis
angle between the pyridine and the hydrazone planes
varies from 1.5(6) to 7.5(3)°, while the angle between
the hydrazone and the phenyl planes varies in the 0.5(2)
to 14.9(2)° range. Therefore the hydrazone ligand in all
complexes is almost planar. Complexes 3 and 6a show the
highest deviation from planarity for the angle between the
hydrazone chain and the phenyl ring.
The molecular structure of H2AcPh has been
determined previously by other authors.43 The hydrazone
adopts the EZ conformation in relation to the C7=N2 and
N3-C8 bonds. The expected lengthening of the C8–O1
bonds from 1.219(2) Å in H2AcPh43 to 1.279(11) Å
in 1 and 1.292(3) and 1.302(3) Å in 4, together with
the shortening of the N3–C8 bond from 1.347(3) Å in
H2AcPh43 to 1.337(12)Å in 1 and 1.321(3) and 1.327(3)Å
in 4, were observed (see Table 2). Therefore the C8–O1
bond changes from a double to a predominantly single
bond whereas N3–C8 acquires some double bond
character. The bond distances between tin and the imine
nitrogen in the complexes, 2.184(4)-2.161(7) Å, are
slightly shorter than the distance between tin and the
pyridine nitrogen, 2.288(4)-2.2354(18)Å. The Sn–O bond
lengths lie in the 2.0916(17)-2.108(3) Å range.
Figures2and3areperspectiveviewsof[BunSn(2AcPh)Cl2]
(1), [BunSn(2AcpClPh)Cl2] (2), [BunSn(2AcpNO2Ph)Cl2]
(3),[PhSn(2AcPh)Cl2](4)and[PhSn(2AcpNO2Ph)Cl2] dmso
•
(6a). Selected intramolecular bond distances and angles of
the complexes are given inTables 2 and 3. The distances and
angles in all complexes are similar. In all complexes tin(IV)
is coordinated to a tridentate anionic ligand, a n-butyl
(1-3) or a phenyl (4 and 6a) group and two chloride ions
trans to each other in an distorted octahedral environment.
In the crystal structures of 3 and 4, two symmetrically
independent molecules were found in the asymmetric unit
(see Figure 2 and Figure 3).
In complexes 1-4 and 6a the N1–Sn–O1 angle of ca.
144.3-146.7° deviates markedly from the ideal value of
180°, probably due to the spatial requirements of the
ligand chelating system. By contrast, the Cl1–Sn–Cl2 and
N2–Sn–C16 angles, which do not involve sterical hindrance,
are approximately 167.3-171.4° and 172.5-179.1° (see
Table 3). In all complexes the metal atom lies in the plane
calculated for the N1N2O1C16 atoms. In structures 1-3 the
distance of the tin atom to the calculated plane varies from
0.023Å to 0.059 Å; in structures 4 and 6a this distance is
smaller (0.002 to 0.009 Å).
Bond distances in the five complexes are similar to those
found in other tin(IV) complexes with hydrazones, as in
trans-dimethyl[2,6-diacetylpyridinebis(2-theoylhydrazone)]
tin(IV)44, where N3–C8 and C8-O1 bond distances of
1.322(8)Å and 1.286(7)Å, respectively, and Sn-C, Sn-Npy,
Sn-Nimine and Sn-O bond distances of 2.102(6), 2.327(4),
2.255(5) and 2.209(4) Å, respectively, were observed.
In all structures the hydrazone skeleton (C7(C15)
N2N3C8O1) is planar, with medium deviation of the fitted
atoms from the calculated plane ranging from 0.0055
to 0.0266 Å. In 1-4 and 6a the hydrazone adopts the E
configuration in relation to the C7=N2 double bond. The

1254
Organotin(IV) Complexes with 2-Acetylpyridine Benzoyl Hydrazones: Antimicrobial Activity
J. Braz. Chem. Soc.
A twisting of approximately 180° in the C2–C7 bond of
the hydrazone to match the steric requirements of tridentate
coordination was evidenced. Hence some angles undergo
significant changes on complexation. The C8–N3–N2
angle goes from 117.02(13)° in H2AcPh43 to 110.7(7)°
in 1 and to 109.5(2)° and 109.8(2)° in 4; N3–C8–O goes
from 123.32(15)° in the free base43 to 125.7(8)° in 1 and
to 126.4(2)° and 125.2(2)° in 4.
The molecular packings of all complexes show weak
interactions involving Cl, H and O atoms with formation of
molecular chains as shown in Figure 4. 1-4 show interactions
…
between adjacent molecules involving Cl Hpy. In 4 and 6a
…
short Cl H contacts are observed involving chlorides and
…
hydrogens from the hydrazone phenyl ring. In 6a Cl
H
O
…
interactions were observed as well, along with short H
contacts involving the oxygens from dmso and from the nitro
group and hydrogens from pyridine and dmso.
Figure 4. Molecular structure scheme of [PhSn(2AcPh)Cl2] (4) showing
short intermolecular contacts between Cl H and O H atoms.
…
…
Table 2. Selected bond lengths (Å) for [BunSn(2AcPh)Cl2] (1), [BunSn(2AcpClPh)Cl2] (2), [BunSn(2AcpNO2Ph)Cl2] (3), [PhSn(2AcPh)Cl2] (4) and
•
[PhSn(2AcpNO2Ph)Cl2] dmso (6a)
Bond
1
2
3
4
6a
C2-C7
1.495(11)
1.505(12)
1.253(11)
1.381(9)
1.337(12)
1.455(12)
1.279(11)
2.108(6)
2.246(8)
2.171(7)
2.456(2)
2.494(3)
2.119(9)
1.504(13)
1.474(12)
1.298(10)
1.363(10)
1.305(11)
1.475(13)
1.309(11)
2.105(7)
2.280(8)
2.161(7)
2.460(2)
2.455(3)
2.166(12)
1.456(7)
1.484(7)
1.283(6)
1.381(6)
1.346(6)
1.471(7)
1.275(6)
2.096(4)
2.278(4)
2.184(4)
2.445(2)
2.500(2)
2.140(7)
1.483(7)
1.474(7)
1.279(6)
1.390(5)
1.308(7)
1.480(7)
1.305(6)
2.108(3)
2.288(4)
2.175(4)
2.445(2)
2.473(2)
2.137(8)
1.487(3)
1.479(3)
1.285(3)
1.381(2)
1.321(3)
1.490(3)
1.292(3)
2.0996(14)
2.2354(18)
2.165(2)
2.4584(7)
2.4532(7)
2.138(3)
1.467(4)
1.486(3)
1.478(4)
1.479(4)
1.282(4)
1.375(3)
1.313(4)
1.487(4)
1.293(3)
2.104(2)
2.264(3)
2.170(3)
2.4771(9)
2.4452(9)
2.135(3)
C7-C15
C7-N2
N2-N3
N3-C8
C8-C9
1.285(3)
1.369(3)
1.327(3)
1.470(3)
C8-O1
Sn1-O1
Sn1-N1
Sn1-N2
Sn1-Cl1
Sn1-Cl2
Sn1-C16
1.302(3)
2.0916(17)
2.2484(19)
2.1713(18)
2.4705(7)
2.4471(7)
2.124(2)
Table 3. Selected angles (°) for [BunSn(2AcPh)Cl2] (1), [BunSn(2AcpClPh)Cl2] (2), [BunSn(2AcpNO2Ph)Cl2] (3), [PhSn(2AcPh)Cl2] (4) and
•
[PhSn(2AcpNO2Ph)Cl2] dmso (6a)
Angle
1
2
3
4
6a
C2-C7-N2
N2-C7-C15
C7-N2-N3
C8-N3-N2
N3-C8-C9
N3-C8-O1
C9-C8-O1
N2-Sn1-C16
N1-Sn1-O1
Cl1-Sn1-Cl2
116.4(7)
125.7(8)
123.0(7)
110.7(7)
116.6(9)
125.7(8)
117.6(8)
175.5(3)
146.7(2)
167.76(12)
114.1(8)
123.9(8)
120.2(7)
111.2(7)
117.2(9)
124.0(8)
118.8(8)
176.1(5)
145.3(3)
169.41(13)
114.5(5)
123.4(5)
121.5(4)
109.6(4)
115.5(5)
125.5(5)
119.0(4)
174.7(2)
144.96(16)
168.97(5)
113.6(5)
124.6(5)
119.7(4)
109.3(4)
115.5(5)
127.1(5)
117.3(5)
172.5(2)
144.32(15)
171.36(6)
114.0(2)
124.0(2)
121.5(2)
109.5(2)
116.0(2)
126.4(2)
117.7(2)
179.06(8)
146.12(7)
169.54(2)
115.0(2)
122.5(2)
122.2(2)
109.8(2)
117.6(2)
125.2(2)
117.6(2)
178.82(9)
145.88(6)
167.30(2)
114.7(3)
123.6(3)
121.7(3)
110.1(3)
115.9(3)
126.5(3)
117.6(3)
176.71(11)
145.97(9)
170.75(3)

Vol. 21, No. 7, 2010
Despaigne et al.
1255
Antimicrobial activity
[PhSn(2AcpNO2Ph)Cl2] < [PhSn(2AcpClPh)Cl2]. The
most active complexes were those with H2AcpClPh (2
and 5), with MIC values similar to that determined for
tetracycline.
Among the hydrazones H2AcpClPh exhibited the
highest activity against C. albicans. Upon coordination
the antifungal activity of the hydrazones increased in
complexes 3 and 6, but remained the same in the other
cases. The antifungal activity increased in complexes 2, 3,
5 and 6 relative to the organotin salts.
Like in the case of the antibacterial activity, the best
results were obtained for the organotin complexes with
H2AcpClPh. The MIC values for complexes 2 and 5
(0.045 mmol mL-1) were the same, suggesting that the
n-butyl or the phenyl group in the metal coordination sphere
have the same effect. This value of MIC is of the same order
of magnitude of that obtained for fluconazole. Likewise, the
MIC values are the same for complexes 3 and 6.
The minimum inhibitory concentrations (MICs) of
the hydrazones and their organotin complexes against
S. aureus and C. albicans are reported in Table 4. Among
the hydrazones the antibacterial activity follows the order
H2AcPh < H2AcpNO2Ph < H2AcpClPh, suggesting that
the electron-withdrawing effect of the nitro and chloro
groups probably favors the antibacterial effect. The
calculated values of log P45 were: 1.98 for H2AcPh, 2.58
for H2AcpClPh and 1.92 for H2AcpNO2Ph. Therefore the
higher lipophilicity of H2AcpClPh probably accounts in
part for its higher activity.
Table 4. Minimum inhibitory concentrations (MIC) of the hydrazones and
their organotin complexes against Staphylococcus aureus and Candida
albicans
Compound
MIC / (mmol mL–1) MIC / (mmol mL–1)
C. albicans
0.213
0.210
0.206
0.046
0.045
0.046
> 0.179
0.096
0.093
> 0.86
0.158
-
S. aureus
0.428
0.255
0.132
0.197
0.059
0.057
0.353
0.125
0.114
> 1.88
0.249
0.020
-
H2AcPh
Conclusions
[BunSn(2AcPh)Cl2] (1)
[PhSn(2AcPh)Cl2] (4)
H2AcpClPh
Organotin compounds are known for their innumerous
bioactivities but are also often rather toxic.46,47 Coordination
of organotin salts with organic ligands could be an
interesting strategy for activity improvement48 or toxicity
reduction. In the present work we demonstrated that
coordination of organotin salts to hydrazones might
improve the pharmacological profile of both metal and
ligands.49
[BunSn(2AcpClPh)Cl2] (2)
[PhSn(2AcpClPh)Cl2] (5)
H2AcpNO2Ph
[BunSn(2AcpNO2Ph)Cl2] (3)
[PhSn(2AcpNO2Ph)Cl2] (6)
[BunSnCl3]
[PhSnCl3]
Supplementary Information
Tetracycline
Fluconazole
0.033
Crystallographic data have been deposited with the
Cambridge Crystallographic Data Centre (deposition
numbers CCDC 747621 (1), CCDC 747620 (2), CCDC
747624 (3), CCDC 747623 (4) and CCDC 747622 (6a)).
Copies of available material can be obtained by request to
CCDC, 12 Union Road, Cambridge CB2 1EZ, UK (fax
44-1223-336033 or e-mail: deposit@ccdc.cam.ac.uk).
[BunSnCl3] proved to be inactive against S. aureus while
[PhSnCl3] exhibited antibacterial activity in the assayed
concentrations. The hydrazones showed antibacterial
activity with MIC values similar to the phenyltin salt.
Upon coordination the antibacterial activities of both the
hydrazones and tin substantially increase. A synergistic
effect involving tin and the hydrazone might be responsible
for this enhancement.
Acknowledgments
The complex of H2AcPh with phenyltin is more
active than its n-butyltin analogue, but the n-butyltin
and phenyltin complexes with the other two hydrazones
are equally active. The activities of the n-butyltin
complexes with the different hydrazones follows the
order [BunSn(2AcPh)Cl2] < [BunSn(2AcpNO2Ph)Cl2] <
[BunSn(2AcpClPh)Cl2], which is the same order of
activity of the free hydrazones. However, the activities
of the phenyltin complexes are [PhSn(2AcPh)Cl2] =
This work was supported by FAPEMIG, CNPq and
Instituto do Milênio em Inovação e Desenvolvimento de
Novos Fármacos e Medicamentos (IM-INOFAR) (Proc.
CNPq 573.564/2008-6), Brazil.
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