Synthesis, characterization, biocide and toxicological activities of di-n-butyl- and diphenyl-tinIV-salicyliden-β-amino alcohol derivatives

Article abstract of DOI:10.1021/ic048628o

The one pot reaction of salicylaldehyde 1, β-amino alcohols 2a-2c, and di-n-butyltin^IV oxide 3a or diphenyltin^IV oxide 3b produced five diorganotin^IV compounds, 4a-4c, 5a, and 5c, in good yields. All compounds were characterized by IR, ¹H, ¹³C, and ¹¹⁹Sn NMR spectroscopy, and elemental analysis; furthermore, compounds 4b, 4c, 5a, and 5c were characterized by X-ray diffraction analysis. After the structural characterization, all of the compounds were tested in vitro against Bacillus subtilis (Gram-positive, strain ATCC 6633), Escherichia coli (Gram-negative, strain DH5α), Pseudomonas aeruginosa (Gram-negative, strain BH3), Desulfovibrio longus (strain DSM 6739), and Desulfomicrobium aspheronum (strain DSM 5918) to assess their antimicrobial activity. Compounds 4 and 5 demonstrated a wide range of bactericidal activities against the tested aerobic (one Gram-positive and two Gram-negative subtypes) and anaerobic bacteria (two sulfate-reducing bacteria, SRB). Compound 5 had better bactericidal performances than compound 4. For all of the compounds, the acute toxicity was measured using luminescent bacteria toxicity (LBT-Microtox) tests to track their further environmental impact. According to these results and in order to fulfill environmental regulations, the toxicity of the compounds studied herein can be modulated through the proper selection of the disubstituted tin^IV moiety.

Full text of DOI:10.1021/ic048628o

Inorg. Chem. 2005, 44, 5370−5378
Synthesis, Characterization, Biocide and Toxicological Activities of
Di-n-butyl- and Diphenyl-tinIV-Salicyliden-
-Amino Alcohol Derivatives
â
Luis S. Zamudio-Rivera,*,† Rocio George-Tellez,† Gerson Lo´pez-Mendoza,† Adela Morales-Pacheco,†
Eugenio Flores,† Herbert Hopfl,‡ Victor Barba,‡ Francisco J. Ferna´ndez,§ Nathalie Cabirol,| and
Hiram I. Beltra´n*,†
1
Programa de Ingenier´ıa Molecular, Instituto Mexicano del Petro´leo, Eje Central La´zaro Ca´rdenas
No.152, Apartado Postal 14-805, 07730 Me´xico, D.F, Centro de InVestigaciones Qu´ımicas,
UniVersidad Auto´noma del Estado de Morelos, AV. UniVersidad 1001, C. P. 62210 CuernaVaca,
Me´xico, Departamento de Biotecnolog´ıa. UniVersidad Auto´noma Metropolitana-Iztapalapa. Apdo.
Postal 55-535, 09340 Me´xico, D.F, and Instituto de Ingenier´ıa. UniVersidad Nacional Auto´noma
de Me´xico, Circuito Escolar S/N, Ciudad UniVersitaria, 04510 Coyoaca´n, Me´xico, D.F.
Received September 30, 2004
The one pot reaction of salicylaldehyde 1,
â
-amino alcohols 2a
−
2c, and di-n-butyltinIV oxide 3a or diphenyltinIV
−4c, 5a, and 5c, in good yields. All compounds were characterized
oxide 3b produced five diorganotinIV compounds, 4a
1
by IR, H, 13C, and 119Sn NMR spectroscopy, and elemental analysis; furthermore, compounds 4b, 4c, 5a, and 5c
were characterized by X-ray diffraction analysis. After the structural characterization, all of the compounds were
tested in vitro against Bacillus subtilis (Gram-positive, strain ATCC 6633), Escherichia coli (Gram-negative, strain
DH5R), Pseudomonas aeruginosa (Gram-negative, strain BH3), Desulfovibrio longus (strain DSM 6739), and
Desulfomicrobium aspheronum (strain DSM 5918) to assess their antimicrobial activity. Compounds 4 and 5
demonstrated a wide range of bactericidal activities against the tested aerobic (one Gram-positive and two Gram-
negative subtypes) and anaerobic bacteria (two sulfate-reducing bacteria, SRB). Compound 5 had better bactericidal
performances than compound 4. For all of the compounds, the acute toxicity was measured using luminescent
bacteria toxicity (LBT-Microtox) tests to track their further environmental impact. According to these results and in
order to fulfill environmental regulations, the toxicity of the compounds studied herein can be modulated through
the proper selection of the disubstituted tinIV moiety.
Introduction
associated with the bio-corrosion and fouling problems are
Gram-positive, Gram-negative, and sulfate-reducing bacteria
(SRB).2 Different molecular prototypes containing tin atoms
in their structure have shown good activity against these
bacterial groups.4-8 According to Lascourre`ges et al., the
mono- and diorganotinIV derivatives are more active than
the corresponding triorganotinIV derivatives against the SRB.4
Moreover, the use of some triorganotinIV molecules as bio-
cides has been banned recently because of their high toxicity
toward marine organisms.9 Hence, the future tendencies
The problems of bio-corrosion and fouling in the oil
industry are commonly controlled through the use of biocides
and dispersants.1-3 The main groups of microorganisms
* To whom correspondence should be addressed. E-mail: lzamudio@
imp.mx (L.S.Z.-R.); hbeltran@imp.mx. (H.I.B.).
† Programa de Ingenier´ıa Molecular, Instituto Mexicano del Petro´leo.
‡ Centro de Investigaciones Qu´ımicas, Universidad Auto´noma del Estado
de Morelos.
§ Departamento de Biotecnolog´ıa, Universidad Auto´noma Metropolitana-
Iztapalapa.
| Instituto de Ingenier´ıa, Universidad Nacional Auto´noma de Me´xico.
(1) O’Reilly, K. T.; Moir, M. E.; O’Rear, D. J. US Pat. 2003, 2003/
0162845 A1.
(4) Lascourre`ges, J. F.; Caumette, P.; Donard, O. X. F. Appl. Organomet.
Chem. 2000, 14, 98.
(5) Gielen, M. Appl. Organomet. Chem. 2002, 16, 481.
(6) Nath, M.; Yadav, R.; Gielen, M.; Dalil, H.; de Vos, D.; Eng, G. Appl.
Organomet. Chem. 1997, 11, 727.
(2) Chan, K. Y.; Xu, L. C.; Fang, H. P. F. EnViron. Sci. Technol. 2002,
36, 1720.
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and Environment in Oil and Gas Exploration and Production Confer-
ence, the Hague, the Netherlands, November 11-14 1991; Society of
Petroleum Engineers, Inc.: Richardson, TX, 1991; 23357, p 355.
(7) Blunden, S. J.; Cusack, P. A.; Hill, R. The Industrial Uses of Tin
Chemicals; Royal Society of Chemistry: London, 1985.
(8) Goh, N. N.; Chu, C. K.; Khoo, L. E.; Whalen, D.; Eng, G.; Smith, F.
E.; Hynes, R. C. Appl. Organomet. Chem. 1998, 12, 457.
5370 Inorganic Chemistry, Vol. 44, No. 15, 2005
10.1021/ic048628o CCC: $30.25
© 2005 American Chemical Society
Published on Web 06/21/2005

DiorganotinIV Compounds
direct the research lines to new organotinIV compounds for
which molecular design should take care of the balance
between toxicity and specific biocide activity.1,9
Scheme 1. Numbering and Preparation of Compounds 4 and 5
A search of the CCDB10 revealed only 33 X-ray structures
of diorganotinIV compounds with methyl, vinyl, n-butyl, and
phenyl substituents attached to the tin atoms that have been
constructed from rigid O, N, O-tridentate ligands with five-
or six-membered fused rings. From these X-ray data, there
are 24 amino acid-containing structures and only 9 amino-
phenol derivatives. These compounds are mainly mono-
meric, even in solution, and in the solid state.11-14 The
Sn-O‚‚‚Sn-O or solvent‚‚‚Sn coordination modes are
mostly preferred in the di-n-butyltinIV derivatives.11-16 In one
of the most recent studies, intermolecular Sn‚‚‚O interactions
were shown to result in dimeric aggregates when the tin
moiety is nBu2SnIV;15,16 in contrast, compounds with
Ph2SnIV functionality barely show such interactions.15,16
These differences would be important for the balance of the
biocide activity and the toxicity in new tin prototypes.
Moreover, the strength of such Sn‚‚‚O interactions was
shown to be modulated through chemical substitution with
electro-withdrawing or electro-releasing groups, which when
used in such a way are chemical balancers of a specific
activity.
Herein, we describe the structural and spectroscopic
characterization of a series of nBu2SnIV and Ph2SnIV sali-
cylidene â-amino alcoholates whose activities have been
measured against aerobic bacteria (Bacillus subtilis, Gram-
positive, strain ATCC 6633; Escherichia coli, Gram-negative,
strain DH5R; and Pseudomonas aeruginosa, Gram-negative,
strain BH3) and against anaerobic bacteria (DesulfoVibrio
longus, strain DSM 6739 and Desulfomicrobium aspher-
onum, strain DSM 5918). The acute toxicological activity
of each compound was measured using the Microtox
luminescent bacteria toxicity (LBT-Microtox) test; the sensi-
tive Photobacterium phosphoreum (Vibrio fischering) was
used as the standard,17a instead of other mammalian cell
lines,17b according to the simplicity of the organisms. The
comparative study allowed us to identify a relationship
between activity and structure.
Results and Discussion
DiorganotinIV derivatives of â-amino alcohols of the type
proposed herein were not found in the literature; therefore,
their preparation, full spectroscopic characterization, X-ray
structures (four derivatives), biocide activity, and acute
toxicity tests are condensed within the present contribution.
Synthetic Procedure. The method involves 1:1:1 stoi-
chiometric addition of salicylaldehyde 1, â-amino alcohols
2a-2c, and di-n-butyltinIV oxide 3a or diphenyltinIV oxide
3b to a 4:1 solvent mixture of toluene and butanol, which
was refluxed for 8 h to produce 4a-4c, 5a, and 5c in yields
of 70 to 92% (Scheme 1). The structural elucidation of the
resulting tin compounds was accomplished by H, 13C, and
1
119Sn NMR, IR, mass spectrometry, elemental analysis, and
single-crystal X-ray crystallographic studies for 4b, 4c, 5a,
and 5c. In the case of 5b (R1 ) H, R2 ) CH3, R3 ) Ph), the
1H, 13C, and 119Sn NMR spectra provided evidence of
oligomeric structures both in coordinating and noncoordi-
nating deuterated solvents. Attempts to obtain monomeric
5b were unsuccessful, and further chromatographic purifica-
tion led to the hydrolysis reaction of the tinIV derivative.7
As a consequence, the structure of 5b could not be
established with certainty, therefore banning further system-
atic studies.
(9) Dubey, S. K.; Roy, U. Appl. Organomet. Chem. 2003, 17, 17.
(10) (a) http://www.ccdc.cam.ac.uk. (b) Allen, F. M. Acta Crystallogr. 2002,
B58, 380. (c) Bruno, I. J.; Cole, J. C.; Edington, P. R.; Kessler, M.;
Macrae, C. F.; McCabe, P.; Pearson, J.; Taylor, R. Acta Crystallogr.
2002, B58, 389. (d) Bruno, I. J.; Cole, J. C.; Lommerse, J. P. M.;
Rowland, R. S.; Taylor, R.; Verdonk, M. J. Comput.-Aided Mol. Des.
1997, 11, 525.
(11) Narula, S. P.; Bharadwaj, S. K.; Sharda, Y.; Day, R. O.; Howe, L.;
Holmes, R. R. Organometallics 1992, 11, 2206.
(12) Dakternieks, D.; Jurkschat, K.; van Dreumel, S.; Tiekink, E. R. T.
Inorg. Chem. 1997, 36, 2023.
Solution NMR of 4a, 4b, 4c, 5a, and 5c. The coupling
types, such as one bond, and the long range heteronuclear
coupling constant for the NMR spectra were systematically
determined for all of the compounds reported herein, in
analogy to previous studies already published for diorganotin
derivatives.5-9,11-16 The 1H NMR spectra shows single signals
for H7 that appears between 8.38 and 8.25 ppm, as well as
the corresponding signals for the iminic salicylidene moi-
ety.15,16 The 1H signals for the â-imino alcohol moiety appear
(13) Dakternieks, D.; Baul, T. S. B.; Dutta, S.; Tiekink, E. R. T.
Organometallics 1998, 17, 3058.
shielded and coupled depending on the substitution. The 13
C
(14) Narula, S. P.; Kaur, S.; Shankar, R.; Verma, S.; Venugopalan, P.;
Sharma, S. K.; Chadha, R. K. Inorg. Chem. 1999, 38, 4777.
(15) (a) Reyes, H.; Garc´ıa, C.; Farfa´n, N.; Santillan, R.; Lacroix, P. G.;
Lepetit, C.; Nakatani, K. J. Organomet. Chem. 2004, 689, 2303. (b)
Farfan, N.; Mancilla, T.; Santillan, R.; Gutierrez, A.; Zamudio-Rivera,
L. S.; Beltra´n, H. I. J. Organomet. Chem. 2004, 689, 3481.
(16) Beltra´n, H. I.; Zamudio-Rivera, L. S.; Mancilla, T.; Santillan, R.;
Farfa´n, N. Chem.sEur. J. 2003, 9, 2291.
NMR data show that signals for C7 appear between 171.5
and 170.6 ppm, indicating a deshielding caused by the
polarization of the CdN bond.15,16 For compounds 4b, 4c,
and 5c, the di-n-butyl and di-phenyl, 1H and 13C signals are
anisochronous because of the presence of stereogenic cen-
ters.15,16 Meanwhile, for compounds 4a and 5a, the re-
spective signals are isochronous.15,16
(17) (a) Bulich, A. A.; Tung, K. K.; Scheibner, G. J. Biolumin. Chemilumin.
1990, 5, 71. (b) Kahru, A.; Tomson, K.; Pall, T.; Ku¨lm, I. Water Sci.
Technol. 1996, 33, 147.
Inorganic Chemistry, Vol. 44, No. 15, 2005 5371

Zamudio-Rivera et al.
Figure 1. X-ray structures of 4b and 4c. The numbering is the same as that in Figure 2.
The 119Sn NMR measurements were obtained in nonco-
ordinating (CDCl3) and coordinating (DMSO-d6) solvents
for the 4 series. The chemical shifts range from -194.6 to
-189.5 ppm, in CDCl3, indicative of pentacoordinated tin
atoms.15,16 For experiments in DMSO-d6, the observed shifts
range from -206.1 to -201.7 ppm and since the solvent
molecules coordinate to tin, shifting the signal to the region
corresponding to hexacoordinated species.15,16 The 5 series
show the 119Sn NMR signals between -337.3 and -334.6
ppm in CDCl3;15-17 meanwhile in DMSO-d6, the signals
remain almost unmoved, indicating the same coordination
number, even in coordinating solvents.
values were also measured to ascertain such a comparison,
and their range is between 96.9 and 86.2 Hz. Therefore, a
2J-3J mixed coupling system for the C4 and C5 positions
in compounds 4a, 4b, 4c, 5a, and 5c is discarded. From the
analysis of the latter statements, two main contributions have
been found: the former is highly dependent on the length
of the coupling (n ) 2 and 3) and the latter is mainly
dependent on the chemical system through which the coupled
atoms are being connected.
X-ray Structures. Compounds 4b, 4c, 5a, and 5c were
successfully crystallized, and their structures were determined
by single-crystal X-ray diffraction analysis. Figures 1 and 2
show the examples for the penta- and hexacoordinated tin-
containing structures. The collection data details are con-
densed in Table 1, and selected geometrical parameters are
shown in Table 2.
Compounds 4b and 4c crystallized with distorted octahe-
dral (DOC) geometry around the tin atom.11-13 The O, N,
O-tridentate ligand is in a mer orientation to the tin
octahedron. The two n-butyl substituents are trans to each
other, allowing the intramolecular coordination of the O3
with tin to build a dimeric species. The resulting Sn2‚‚‚O3
bond has a magnitude of 2.500(2) Å for 4b and 2.457(3) Å
for 4c. These values are smaller than the sum of the van der
Waals radii (2.17 Å for tin and 1.52 Å for oxygen).16
Additionally, the Sn-O‚‚‚Sn-O torsion angles show evi-
dence of coplanarity because there is a 1° deviation of the
two different dimeric molecules.15,16 The dimeric assembly
occurs via the formation of a Sn2O2 four-membered ring.15,16
The O‚‚‚Sn bonding occurs with the oxygen atom at the five-
membered ring.
Compounds 5a and 5c crystallized with trigonal bipyra-
midal (TBP) geometry surrounding the tin atom.15,16 The two
oxygen-donating atoms of the O, N, O-tridentate ligand are
in axial positions, and the nitrogen atom occupies one
equatorial position. The two phenyl groups attached to tin
occupy the other two equatorial positions. Compound 5c
cocrystallized with 0.5 equiv of a water molecule per
asymmetric unit, forming a hydrogen bond between the O3
and the hydrogen atom of the water with a bond length of
2.017(3) Å.
For some of the compounds, the measurement of
n
| J(119/117Sn-13C)|, where n ) 1, 2, and 3, was feasible
through aromatic and aliphatic systems. These measurements
are a method for determining important structural details
among different derivatives and should be taken into account
for the present study. The coupling constants for the aromatic
salicylidene system behave in a manner very similar to that
found for the analogous amino acid derivatives.16 The
coupling constants for the â-imino alcohol moiety, including
the C4 and C5 positions, are not directly comparable to those
observed for the R-iminoacid fragment where the values of
| J(119/117Sn-13C-)| for an sp2 carbon atom and a bridging
2
sp3 oxygen atom are between 21.6 and 14.6 Hz.16 The
2
values of | J(119/117Sn-13C5)| for an sp3 carbon atom and a
bridging sp2 nitrogen atom are between 16.9 and 12.8 Hz.16
For the compounds from this study, the magnitude of
| J(119/117Sn-13C4)| for an sp3 carbon atom and a bridging
2
sp3 oxygen atom are between 22.5 and 18.4 Hz. They are
very similar to the values found for the R-iminoacid
2
derivatives. The magnitudes for | J(119/117Sn-13C5)| for an
sp3 carbon atom and a bridging sp2 nitrogen atom are be-
tween 44.4 and 33.1 Hz. These values are somewhat
divergent from those found for the R-iminoacid derivatives.
Keep in mind that at this position there is more chemical
2
similarity between the fragments. The | J(119/117Sn-13Câ)|
values were measured (taken as reference for a free aliphatic
system and therefore without cyclic restraints) to assess more
evidence within these observations; their range was found
3
to be between 34.6 and 30.5 Hz. The | J(119/117Sn-13Cγ)|
5372 Inorganic Chemistry, Vol. 44, No. 15, 2005

DiorganotinIV Compounds
Figure 2. X-ray structures of 5a and 5c.
Table 1. Collection Data and Refinement Parameters for Compounds 4b, 4c, 5a, and 5c
4b
4c
5a
5c
molecular formula
mol wt
C18H29NO2Sn
410.11
C19H31NO2Sn
424.14
C21H19NO2Sn
436.06
C23H23NO2Sn‚1/2H2O
473.12
cryst syst
space group
a (Å)
b (Å)
c (Å)
monoclinic
P21/c
12.1690(12)
17.9743(17)
8.7980(9)
90
99.699(2)
90
1896.6(3)
4
monoclinic
P21/c
9.4206(12)
17.690(2)
11.6191(15)
90
100.862(2)
90
2083.9(3)
4
triclinic
P1h
monoclinic
C2/c
16.3162(14)
10.1829(9)
24.627(2)
90
93.682(2)
90
4083.3(6)
8
9.0118(11)
9.4311(11)
11.2241(13)
86.643(2)
78.387(2)
70.979(2)
883.38(18)
2
R (deg)
â (deg)
γ (deg)
vol (Å3)
Z
F (mg/m3)
1.436
1.354
1.70 to 25.00
18142
1.481
1.353
2.12 to 25.00
18214
1.639
1.460
1.85 to 24.99
6992
1.539
1.272
1.66 to 25.00
9955
µ (mm-1
)
θ range (deg)
collected reflns
individual reflns [R(int)]
θ completeness [%]
data/restrictions/params
GOF on F2
3343 [0.028]
25.00° [100]
3343/38/279
1.060
3342 [0.059]
25.00° [100]
3342/0/332
1.083
3104 [0.029]
24.99° [99.5]
3104/0/226
1.042
3603 [0.025]
25.00° [100]
3603/1/253
1.098
final indices [I > σ(I)] R1
final indices (all data) wR2
∆Fmin(e‚Å3)
0.024
0.061
-0.25
0.34
0.035
0.074
-0.79
1.00
0.022
0.052
-0.37
0.60
0.026
0.059
-0.27
0.55
∆Fmax(e‚Å3)
The N6-Sn2 bond distances are 2.244(2), 2.237(3), 2.186-
(2), and 2.175(2) Å, the Sn2-O1 bond distances are 2.234-
(2), 2.268(2), 2.107(2), and 2.100(2) Å, and the Sn2-O3
bond distances are 2.087(2), 2.100(2), 2.049(2), and 2.074-
(2) Å for 4b, 4c, 5a, and 5c, respectively. By analyzing the
three sets of distances, one can see that the first two values
are longer because they are related to hexacoordinated tin
atoms, and the latter values are shorter because of the
bonding to pentacoordinated tin atoms. The bond angles
between both r carbons and the tin atoms (C-Sn-C) also
depend on the coordination number of tin. They are 145.89-
(13)° for 4b, 151.90(16)° for 4c, 126.14(8)° for 5a, and
Inorganic Chemistry, Vol. 44, No. 15, 2005 5373

Zamudio-Rivera et al.
Table 2. Selected Geometrical Parameters for Compounds 4b, 4c, 5a, and 5c
4b
4c
5a
5c
bond lengths (Å)
N(6)-Sn(2)
C-Sn(2)
2.244(2)
2.116(3)
2.122(3)
2.234(2)
2.087(2)
2.500(2)
1.286(3)
1.292(3)
2.237(3)
2.138(4)
2.120(4)
2.268(2)
2.100(2)
2.457(3)
1.285(5)
1.298(4)
1.414(4)
1.527(5)
1.475(5)
1.443(5)
1.417(5)
0.916(39)
2.186(2)
2.119(2)
2.130(2)
2.107(2)
2.049(2)
2.175(2)
2.120(3)
2.125(3)
2.100(2)
2.074(2)
-
1.290(3)
1.315(3)
1.410(3)
1.523(4)
1.477(3)
1.436(3)
1.424(3)
0.938(26)
C-Sn(2)
O(1)-Sn(2)
O(3)-Sn(2)
O(3)‚‚‚Sn(2)
N(6)-C(7)
C(9)-O(1)
C(4)-O(3)
C(4)-C(5)
N(6)-C(5)
C(7)-C(8)
C(8)-C(9)
C(7)-H(7)
-
1.291(3)
1.318(3)
1.402(3)
1.527(4)
1.470(3)
1.433(3)
1.421(3)
0.893(29)
1.397(4), 1.432(11)a
1.447(5), 1.381(12)a
1.467(4)
1.424(8)
1.411(4)
0.918(3)
bond angles (deg)
151.90(16)
C-Sn(2)-C
145.89(13)
153.51(7)
78.07(8)
126.14(8)
124.73(9)
159.21(7)
81.75(7)
78.21(7)
123.10(9)
112.08(8)
90.36(9)
94.55(9)
98.04(9)
95.91(9)
128.73(15)
111.86(15)
127.60(17)
111.99(15)
122.9(2)
105.4(2)
110.2(2)
122.4(2)
126.8(2)
-
O(1)-Sn(2)-O(3)
N(6)-Sn(2)-O(1)
N(6)-Sn(2)-O(3)
N(6)-Sn(2)-C
152.94(9)
77.59(10)
75.54(10)
103.63(14)
100.65(14)
83.26(13)
88.36(13)
100.03(13)
99.55(13)
127.3(2)
112.9(2)
128.0(3)
115.9(2)
122.7(3)
105.2(3)
110.1(3)
123.2(3)
127.0(4)
111.70(10)
68.30(10)
159.26(7)
82.20(7)
78.04(7)
124.71(8)
109.07(8)
93.67(8)
91.14(8)
94.91(8)
98.66(8)
131.97(14)
111.65(16)
128.20(16)
112.73(15)
123.0(2)
107.0(2)
109.5(2)
123.3(2)
127.2(2)
-
75.44(7)
105.28(11)
105.45(10)
85.81(11)
N(6)-Sn(2)-C
O(1)-Sn(2)-C
O(1)-Sn(2)-C
86.35(11)
O(3)-Sn(2)-C
100.87(11)
100.85(11)
132.68(18)
110.95(16)
130.13(19)
116.67(18), 115.6(5)a
123.2(3)
O(3)-Sn(2)-C
Sn(2)-O(1)-C(9)
Sn(2)-N(6)-C(5)
Sn(2)-N(6)-C(7)
Sn(2)-O(3)-C(4)
O(1)-C(9)-C(8)
C(4)-C(5)-N(6)
O(3)-C(4)-C(5)
C(7)-C(8)-C(9)
N(6)-C(7)-C(8)
Sn(2)-O(3)‚‚‚Sn(2)
O(3)-Sn(2)‚‚‚O(3)
110.1(3), 115.6(5)a
111.2(3), 113.1(8)a
123.0(2)
128.0(3)
110.17(7)
69.83(7)
-
-
dihedral angles [deg]
Sn(2)-O(1)-C(9)-C(10)
N(6)-C(7)-C(8)-C(13)
Sn(2)-O(3)-C(4)-C(5)
C(7)-N(6)-C(5)-C(4)
156.2(3)
145.2(3)
-170.8(4)
41.7(4)
-159.19(16)
174.4(2)
-48.0(2)
148.9(2)
-147.57(19)
170.8(3)
-46.4(3)
140.8(2)
-173.3(3)
38.9(5), -35.7(12)a
177.0(8), -145.0(4)a
-132.3(4)
deviation from mean C(7)-C(8)-C(9)-C(10)-C(11)-C(12)-C(13)-O(1) plane (Å)
Sn(2)
N(6)
0.580(2)
0.185(1)
-0.989(4)
-0.199(5)
-0.505(2)
-0.145(3)
-0.786(2)
-0.261(3)
a There are two values reported because disorder occurred for this fragment.
124.73(9)° for 5c ( the average value for TBP compounds
is 126.99°, denying molecules which contain abnormal
packing effects that significantly modify the geometry of
tin).15,16 The O1-Sn2-O3 bond angle values are 153.51-
(7)° for 4b, 152.94(9)° for 4c, 159.26(7)° for 5a, and 159.21-
(7)° for 5c. The first two values are smaller because of the
steric and electronic demands of the sixth ligand.
As a consequence of ring fusion, the O3-Sn2-N6 bond
angles in the five-membered rings have values of 75.44(7)°
for 4b, 75.54(10)° for 4c, 78.04(7)° for 5a, and 78.21(7)°
for 5c, while the angles of the O1-Sn2-N6 bonds are 78.07-
(8)° for 4b, 77.59(10)° for 4c, 82.20(7)° for 5a, and 81.75-
(7)° for 5c. The first two values for each angle are smaller
than the following two values. This trend is also caused by
the increment in coordination number and the proximity of
a second molecule.
effects on the growth of B. subtilis, E. coli, P. aeruginosa,
D, longus, and D. aspheronum strains (Table 3).
From the data compiled in Table 4, it is evident that
compound 5 exhibited better antibacterial activity against
aerobic bacteria at concentrations ranging from 1 × 10-2
to 25 ppm than that exhibited by compound 4, the con-
centrations of which range from 1 × 10-2 to 50 ppm. The
data show that there is an increased activity against P.
aeruginosa, whereby three different compounds result in
the inhibition of the growth of the microorganism at
concentrations as low as 1 × 10-2 ppm. In the case of the
B. subtilis strain, the effect is moderate with only two
compounds having a minimum inhibitory concentration
(MIC, defined in the Experimental Section) of around 1 ppm.
Finally, the tests with E. coli are indicative that all of the
compounds have higher inhibitive doses with MICs near 25
ppm.
Biocide Activity. The bactericidal efficiencies of com-
pounds 4 and 5 have been determined to examine their
applicability as biocides. They have shown good activity.
The compounds exhibited varying degrees of inhibitory
It is remarkable that the bacteria of the genus Pseudomonas
are a group of microorganisms that show very high metabolic
versatility, and therefore a large number of biocides feed
5374 Inorganic Chemistry, Vol. 44, No. 15, 2005

DiorganotinIV Compounds
Table 3. Antibacterial Activity of Compounds 4 and 5 Varying the Concentrationa
concentration (ppm)
compound
0.01
0.1
1
2.5
5
10
25
50
75
100
B. subtilis
16.6
4a
4b
4c
5a
5d
ligand
(- - -)
(- - -)
(- - -)
(- - -)
(- - -)
(- - -)
(- - -)
(- - -)
(- - -)
(- - -)
(---)
(- - -)
(- - -)
(- - -)
13.4
(- - -)
(- - -)
(- - -)
14.9
13.3
14.1
13.0
(- - -)
17.9
18.1
16.0
19.4
18.4
(- - -)
20.4
20.0
18.1
22.1
20.0
(- - -)
21.4
21.4
20.4
22.9
20.1
(- - -)
21.9
22.03
21.3
22.6
22.2
(- - -)
22.4
22.4
23.3
22.8
22.9
(- - -)
16.8
14.8
19.5
16.7
(- - -)
(- - -)
E. coli
(- - -)
(- - -)
(- - -)
13.1
4a
4b
4c
5a
(- - -)
(- - -)
(- - -)
(- - -)
(- - -)
(- - -)
(- - -)
(- - -)
(- - -)
(- - -)
(- - -)
(- - -)
(- - -)
(- - -)
(- - -)
(- - -)
(- - -)
(- - -)
(- - -)
(- - -)
(- - -)
(- - -)
(- - -)
(- - -)
(- - -)
(- - -)
(- - -)
13.6
(- - -)
(- - -)
10.45
11.3
(- - -)
(- - -)
10.6
11.5
12.3
11.2
18.1
10.6
(- - -)
25.2
12.3
13.6
12.5
17.9
11.3
(- - -)
13.03
14.6
13.6
20.7
11.4
(- - -)
5d
(- - -)
(- - -)
ligand
(- - -)
poly-1b
P. aeruginosa
11.7
4a
4b
4c
5a
(- - -)
(- - -)
10.5
10.1
11.2
(- - -)
(- - -)
11.2
10.8
11.9
(- - -)
(- - -)
10.8
11.5
11.2
11.0
14.2
12.3
11.8
12.2
(- - -)
12.9
16.0
14.8
15.9
13.3
(- - -)
12.9
16.8
14.8
21.9
17.8
(- - -)
14.3
18.8
15.0
24.8
22.6
(- - -)
20.0
17.0
21.9
23.7
26.3
24.7
(- - -)
20.4
26.2
24.3
27.0
26.0
(- - -)
15.1
13.0
13.9
13.4
5d
ligand
(- - -)
(- - -)
(- - -)
(- - -)
poly-1b
D. longus
(+)
4b
4c
5a
(+)
(+)
(+)
(+)
(+)
(+)
(+)
(+)
(+)
(+)
(+)
(+)
(+)
(+)
(+)
(+)
(+)
(+)
(+)
(+)
(+)
(-)
(-)
(-)
(-)
(-)
(-)
(+)
(+)
D. aspheronum
4b
4c
5a
(+)
(+)
(+)
(+)
(+)
(+)
(+)
(+)
(+)
(+)
(+)
(+)
(+)
(+)
(+)
(+)
(+)
(+)
(+)
(+)
(+)
(+)
(+)
(+)
(-)
(-)
(-)
(-)
(-)
(-)
a (- - -) denotes no inhibition zone formation. For B. subtilis, E. coli, and P. aeruginosa, the diameter of the inhibition zone (mm) was measured after 16
h of incubation at 30 °C. For D. longus and D. aspheronum, the presence (+) and absence (-) of growth was measured. Measurements taken from Sun et
al. (ref 21a). b Reported organotin compounds (ref 21b) have shown inhibition zones between 18 and 8 mm at 500 and 1000 ppm concentrations and
therefore they are more active than those of the Streptomycin reference (ref 21b and 21c)
Table 4. Agar MICs of the Antimicrobial Agents Following Incubation
A number of biocides have limited effects against specific
Gram-positive or -negative subsets of microorganisms. P.
at 30 °C for a Period of 16 ha
average (mode) MIC (ppm)
aeruginosa and E. coli, both Gram-negative bacteria, showed
very different susceptibility to the biocides described in this
work. On the other hand, there is not a great difference
between the data obtained from P. aeruginosa (Gram-
negative) and B. subtilis (Gram-positive). Thus, the differ-
ences in composition and ultrastructure (at the cell wall of
the bacteria) are not the key to explain the different activities
of the biocides against the different microorganisms. A
mechanism of action, based on the chemical structure of the
compounds, involves the formation of X-Sn bonds (X )
Npuric and pyrimidinic, Ocarboxylate) at active biological centers resulting
in an interference with the normal cell processes.7-9
compound
B. subtilis
E. coli
P. aeruginosa
4a
4b
4c
5a
5c
ligand
5
2.5
2.5
1
1
-
25
25
50
5
25
-
2.5
2.5
1 × 10-2
1 × 10-2
1 × 10-2
-
these bacteria.19 Compounds 4 and 5 are specifically inhibi-
tive against its growth.
To clarify that the inhibitory efficiency is a result of the
R2SnIV (R ) nBu and Ph) moiety presence, we tested the
ligand corresponding to 4a and 5a, and the results show no
inhibitory effect for all of the bacteria used (as measured by
MIC determination).
By taking the latter results as definite criteria, we
performed the further anaerobic bacteria (SRB) tests only
for 4b, 4c, and 5a, which show the same efficacy at 75 ppm.
The variation in the effectiveness of the biocide com-
pounds against different microorganisms depends on, among
other things, the permeability across the bacterial cell wall.20
Acute Toxicity Assays. The luminescent bacteria toxicity
(LBT-Microtox) tests were performed for all diorganotin
compounds. It is worth mentioning that the LBT-Microtox
assay was first used for lixiviates and residual water solutions
for industrial field applications.17 In the remnant references,
acute toxicity tests performed in several mammalian cell lines
were often trackers of such activities.22 Nevertheless, the
latter reviews stated that within this branded Microtox, plenty
of other new protocols were developed to test different types
(18) Bondi, A. J. Phys. Chem. 1964, 68, 441.
(19) Spiers, A. J.; Buckling, A.; Rainey, P. B. Microbiology 2000, 146,
(20) Saxena, C.; Singh, R. V. Phosphorus, Sulfur Silicon Relat. Elem. 1994,
97, 17.
2345.
Inorganic Chemistry, Vol. 44, No. 15, 2005 5375

Zamudio-Rivera et al.
Table 5. Acute Toxicity of Compounds 4 and 5 in P. phosphoreuma
EC50 EC50
consists of the in situ formation of a tridentate Schiff base
ligand followed by the addition of di-n-butyl- or diphenyl-
tinIV oxide.
compound
(5 min) toxicity rating (15 min) toxicity rating
4a
4b
4c
5a
5c
ligand
2.39 moderately toxic
80.42 slightly toxic
23.70 slightly toxic
4.50 moderately toxic
0.43 highly toxic
2.06 moderately toxic
67.66 slightly toxic
72.41 slightly toxic
The 1H, 13C, and 119Sn NMR data allowed us to establish
the formation of the products that supported the N-Sn bond
formation and specify the coordination number of the tin
atom as five when CDCl3 was employed as solvent.
Meanwhile, when DMSO-d6 was used as the solvent, the
coordination number of the tin atom increases to six.
The solid-state structures of compounds 5a and 5d have
a TBP tin atom, while compounds 4b and 4c crystallized
within dimeric arrangements via the intramolecular self-
assembly of tin atoms with donor oxygen atoms to build a
Sn2O2 four-membered ring moiety.
The title compounds were tested in vitro against B. subtilis
(strain ATCC 6633), E. coli (strain DH5R), P. aeruginosa
(strain BH3), D. longus (strain DSM 6739), and D. aspher-
onum (strain DSM 5918) demonstrating a wide range of
bactericidal activity.
Moreover, compound 5 displayed an enhanced bactericidal
activity in comparison to that of compound 4 indicating that
the SnIVPh2 moiety is responsible for this increase.
Acute toxicity tests were also performed to evaluate the
ecological impact of compounds 4 and 5; the results show
moderate toxicity in all cases.
A brief discussion and qualitative connection between the
solution and solid-state coordination modes of diorganotin
molecules with the biocide activities and the acute toxicity
tests is also presented, showing a modulated biologic effect
depending on chemical structure.
-
-
-
-
617.43 nontoxic
318.66 nontoxic
fatty diamineb,c
chlorinated
aromaticb,c
-
-
-
-
1.1
moderately toxic
0.52 highly toxic
a (-) indicates no measurement recorded because of the observed toxicity.
b See ref 3 for further details. c Commercial product cited for comparison.
of toxicity for pure chemical compounds.23 This alternative
protocol was performed also to reduce or refine some of the
mammalian cell procedures with high proficiency in the
obtained results, and therefore, it has became one of the
streamlined tests for this means.17,24
Herein, the LBT-Microtox tests (lately called Microtox)
for specific acute toxicity measurements were carried out to
select the most environmentally benign compound as a
biocide prototype. The 5 and 15 min EC50 values for 4a,
4b, 4c, 5a, and 5c obtained in a commercial LBT-Microtox
assay are listed in Table 5. The values for the 5 min Microtox
EC50 for compounds 4 and 5 ranged from 0.426 mg/L (5d)
to 80.42 mg/L (4b). The less toxic compounds were the 4
series, specifically 4b and 4c which display only slightly
toxic values at both 5 and 15 min. On the other hand, the
ligand exhibited practically nontoxic behavior (617.43 mg/
L). The toxicity levels were maintained, even through 30
min kinetic tests.
Qualitative Structure Activity Relationships. In solution,
the coordination number of the tinIV atom, in compound 4,
can be incremented from five to at least six with the addition
of coordinating solvents such as DMSO-d6. Meanwhile, with
noncoordinating solvents, such as CDCl3, the coordination
number is maintained. This statement gives further insight
into the understanding of the lower toxicity and lower biocide
activity of the 4 series compared to that of the 5 series. The
series 4 compounds are dimeric in the solid state through
Sn2O2 four-member ring formation, which is not observed
for series 5 compounds. These molecular modes can be a
first principle model of intermolecular interaction and, in a
superlative mode, analogous to the supramolecular recogni-
tion of microorganisms, often called molecular-macromo-
lecular docking.
Experimental Section
All reagents and solvents were purchased as reagent grade quality
and were used as received. Salicylaldehyde (1), â-amino alcohols
(2a-d), di-n-butyltinIV oxide (3a), and diphenyltinIV oxide (3b)
were purchased from Aldrich, and toluene and butanol were
purchased from Fermont.
The solution NMR experiments were performed on Varian
Mercury 200-4 nucleus and 200-BB spectrometers at room tem-
perature; chemical shifts (ppm) are relative to TMS and SnMe4,
and the coupling constants are quoted in Hz. Infrared spectra were
recorded as KBr pellets on a Bruker Tensor 27 FT-IR spectropho-
tometer. Melting points were measured in open capillary tubes on
a Gallenkamp MFB 595 apparatus and have not been corrected.
Elemental analysis determinations were obtained on a Perkin Elmer
CHNO/S apparatus.
The X-ray single-crystal structure determinations for 4b, 4c, 5a,
and 5c were performed on a BRUKER-AXS APEX diffractometer
with a CCD area detector (λ(Mo KR) ) 0.71073 Å, graphite
monochromator). Frames were collected at T ) 173 or 298 K via
ω and æ rotation at 10 s per frame (SMART).25 The measured
intensities were reduced to F2 and corrected for absorption with
SADABS (SAINT-NT).26 Structure solution, refinement, and data
output were carried out with the SHELXTL-NT27 program package.
Conclusions
An efficient one-step procedure was established to prepare
a series of 2,2-di-n-butyl- and 2,2-diphenyl-6-aza-1,3-dioxa-
2-stanna-benzocyclononenes (4a-d, 5a, and 5d) which
(21) (a) Sun, G.; Wheatley, W. B.; Worley S. D. Ind. Eng. Chem. Res.
1994, 33, 168. (b) Jain, M.; Gaur, S.; Singh, V. P.; Singh, R. V. App.
Organomet. Chem. 2004, 18, 73. (c) Nagpal, P.; Singh, R. V. Appl.
Organomet. Chem. 2004, 18, 221.
(22) US Congress, Office of Technology Assessment. AlternatiVes to
Animal Use in Research, Testing and Education; OTA-BA-273; US
Government Printing Office: Washington, DC, 1986.
(24) (a) Ren, S. J.; Frymier, P. D. Chemosphere 2005, 58, 543. (b)
Steinberg, S. M.; Poziomek, E. J.; Engelmann, W. H.; Rogers, K. R.
Chemosphere 1995, 30, 2155.
(25) SMART, version 5.618; Bruker AXS: Madison, WI, 2000.
(26) SAINT + NT, version 6.04; Bruker AXS: Madison, WI, 2001.
(27) SHELXTL-NT, version 6.10; Bruker AXS: Madison, WI, 2000.
(23) Microtox Tabulations of Pure Chemical Compounds; Strategic Diag-
nostics Inc.: Newark, DE, 2003.
5376 Inorganic Chemistry, Vol. 44, No. 15, 2005

DiorganotinIV Compounds
All software manipulations were done in the WIN-GX28 environ-
ment. Molecular perspectives were drawn using the ORTEP 329
drawing application. All of the heavier atoms were found using
Fourier difference maps and refined with an anisotropic scheme.
Some hydrogen atoms were also found using Fourier difference
maps and were refined with an isotropic scheme; the remaining
hydrogen atoms were geometrically modeled and calculated for the
refinement.
C, 52.87; H, 7.22, N, 3.46. Crystals suitable for X-ray diffraction
analysis were obtained from a 6:1 solvent mixture of hexane and
dichloromethane.
2,2-Di-n-butyl-6-aza-1,3-dioxa-5-ethyl-2-stanna-benzocyclonon-
ene (4c). Yellow powder. Yield: 78%. mp: 56-58 °C.1H NMR:
δ 8.25 (sb, 1H, 3J(119/117Sn-1H) ) 40.8, H7), 7.24 (ddd, Jo ) 8.4,
7.0, Jm ) 1.4, 1H, H11), 7.03 (dd, Jo ) 7.0, Jm ) 8.4, 1H, H13),
6.66 (d, Jo ) 8.4, 1H, H10), 6.55 (dd, Jo ) 8.4, 7.0, 1H, H12),
4.04 (d, J ) 9.9, 3J(119/117Sn-1H) ) 48.8, 1H, H4a), 3.90 (dd, J )
9.9, 3.6, 1H, H4b), 3.17 (dt, J ) 7.1, 3.6, 3J(119/117Sn-1H) )
35.8, 1H, H5), 1.88 (sx, J ) 7.1, 1H, H14a), 1.73-1.17 (m,
13H, R-CH2-, â-CH2-, γ-CH2-), 0.93 (t, J ) 7.1, 3H, H15),
0.86 (t, J ) 7.4, 2H, δ-CH3), 0.78 (t, J ) 7.4, 2H, δ-CH3).
13C NMR: δ 170.6 (2J(119/117Sn-13C) ) 8.0, C7), 170.0
(2J(119/117Sn-13C) ) 29.5, C9), 136.2 (C11), 134.8 (C13), 122.7
(C10), 117.4 (3J(119/117Sn-13C) ) 23.1, C8), 115.8 (C12), 70.6
(2J(119/117Sn-13C) ) 33.1, C5), 66.5 (2J(119/117Sn-13C) ) 21.9, C4),
27.7 (â-CH2-), 27.6 (â-CH2-), 27.4 (γ-CH2-), 27.3 (γ-CH2-),
27.2 (C14), 21.9 (J(119Sn-13C) ) 648.6, J(117Sn-13C) ) 614.5,
R-CH2-), 20.7 (J(119Sn-13C) ) 609.6, J(117Sn-13C) ) 582.2,
R-CH2-), 14.2 (δ-CH3), 11.2 (C15). 119Sn NMR: δ -192.8
(CDCl3), -201.7 (DMSO-d6). IR (KBr): ν 2958, 2918, 2852, 1606
(CdN), 1584 (CdN), 1532, 1476, 1464, 1438, 1386, 1288, 1276,
1210, 1148, 836, 526 cm-1. Calcd for C19H31NO2Sn: C, 53.80; H,
7.37; N, 3.30. Found: C, 53.62; H, 7.20, N, 3.07. Crystals suitable
for X-ray diffraction analysis were obtained from an 8:1 solvent
mixture of hexane and dichloromethane.
General Synthetic Procedure. Preparation of 2,2-di-n-butyl-
6-aza-1,3-dioxa-2-stanna-benzocyclononene (4a). Salicylaldehyde
(1, 0.5 g, 4.09 mmol), ethanolamine (2a, 0.447 g, 4.09 mmol) and
di-n-butyltinIV oxide (3, 1.02 g, 4.09 mmol) were added to 100
mL of a 4:1 mixture of toluene and butanol in a previously dried
flask; the resulting saturated solution was refluxed for 8 h.
Compound 3 was not soluble under the reaction conditions, but
after 2 or 3 h, it condenses with the in situ formed tridentate ligand.
After the reaction was completed, the crude product was evaporated
under reduced pressure, and the solid was dissolved in 10 mL of
dichloromethane and precipitated by solvent polarity change with
hexane or petroleum ether to yield compound 4a as a yellow
powder.
All of the compounds were prepared using the same molar ratios
described for 4a.
2,2-Di-n-butyl-6-aza-1,3-dioxa-2-stanna-benzocyclononene (4a).
1
Yellow powder. Yield: 84%. mp: 72-74 °C. H NMR: δ 8.35
(sb, 1H, 3J(119/117Sn-1H) ) 39.8, H7), 7.27 (ddd, Jo ) 8.4, 7.0, Jm
) 1.4, 1H, H11), 7.04 (dd, Jo ) 7.6, Jm ) 1.4, 1H, H13), 6.69 (d,
Jo ) 8.4, 1H, H10), 6.58 (dd, Jo ) 7.6, 7.0, 1H, H12), 4.05 (t,
J ) 5.4, 3J(119/117Sn-1H) ) 26.8, 2H, H4), 3.62 (t, J ) 5.4,
3J(119/117Sn-1H) ) 20.4, 2H, H5), 1.34 (t, J ) 7.4, 4H, R-CH2-),
1.62 (sq, J ) 7.4, 4H, â-CH2-), 1.30 (sx, J ) 7.4, 4H,
γ-CH2-), 0.85 (t, J ) 7.4, 4H, δ-CH3). 13C NMR: δ 171.4
(2J(119/117Sn-13C) ) 8.4, C7), 170.0 (C9), 136.3 (C11), 134.7 (C13),
122.7 (C10), 117.3 (C8), 115.8 (C12), 63.4 (2J(119/117Sn-13C))22.1,
C4), 60.7 (2J(119/117Sn-13C) ) 37.0, C5), 27.9 (2J(119/117Sn-13C)
2,2-Di-phenyl-6-aza-1,3-dioxa-2-stanna-benzocyclononene (5a).
Yellow powder. Yield: 92%. mp: 203 °C (dec). 1H NMR: δ 8.38
3
(sb, 1H, J(119/117Sn-1H) ) 50.4, H7), 7.93 (dd, Jo ) 7.8, Jm
)
4.4, J(119/117Sn-1H) ) 75.6, 4H, H-ortho-Sn-Ph), 7.44 (ddd, Jo
) 7.8, 7.0, Jm ) 1.8, 1H, H11), 7.41-7.36 (m, 6H, H-meta-,
H-para-Sn-Ph), 7.09 (dd, Jo ) 7.8, Jm ) 1.8, 1H, H13), 7.08 (d,
Jo ) 7.8, 1H, H10), 6.58 (dd, Jo ) 7.8, 7.0 1H, H12), 4.26
(t, J ) 5.3, 3J(119/117Sn-1H) ) 35.8, 2H, H4), 3.74 (t, J )
5.3, 3J(119/117Sn-1H) ) 22.0, 2H, H5). 13C NMR: δ 171.5
(2J(119/117Sn-13C) ) 9.6, C7), 169.6 (2J(119/117Sn-13C) ) 32.1, C9),
140.4 (J(119Sn-13C) ) 982.3, J(117Sn-13C) ) 939.4, C-ipso-SnPh),
136.6 (C11), 136.6 (2J(119/117Sn-13C) ) 50.5, C-ortho-SnPh),
134.8 (C13), 129.9 (4J(119/117Sn-13C) ) 16.8, C-para-SnPh),
128.5 (3J(119/117Sn-13C) ) 81.1, C-meta-SnPh), 122.8 (C10),
3
3
) 30.5, â-CH2-), 27.3 (3J(119Sn-13C) ) 90.0, J(117Sn-13C) )
86.2, γ-CH2-), 21.5 (J(119Sn-13C) ) 628.3, J(117Sn-13C) ) 599.8,
R-CH2-), 14.2 (δ-CH3). 119Sn NMR: δ -194.6 (CDCl3), -202.0
(DMSO-d6). IR (KBr): ν 2935, 2921, 2850, 2860, 1626 (CdN),
1527, 1450, 1466, 1146, 1060, 869, 759, 600 cm-1. Calcd for
C17H27NO2Sn: C, 51.55; H, 6.87; N, 3.54. Found: C, 51.74; H,
7.01; N, 3.38.
117.3 (3J(119/117Sn-13C)
) 26.4, C8), 116.5 (C12), 63.0
(2J(119/117Sn-13C) ) 18.4, C4), 60.3 (2J(119/117Sn-13C) ) 44.4, C5).
119Sn NMR: δ -337.3 (CDCl3), -339.7 (DMSO-d6). IR (KBr): ν
2909, 2865, 2811, 1628 (CdN), 1541 (CdN), 1467, 1448,
2,2-Di-n-butyl-6-aza-1,3-dioxa-4-methyl-2-stanna-benzocy-
clononene (4b). Yellow powder. Yield: 72%. mp: 119-121 °C.1H
NMR: δ 8.34 (sb, 1H, 3J(119/117Sn-1H) ) 39.8, H7), 7.28 (ddd, Jo
) 8.6, 6.8, Jm ) 1.5, 1H, H11), 7.04 (dd, Jo ) 7.8, Jm ) 1.5, 1H,
H13), 6.71 (d, Jo ) 8.6, 1H, H10), 6.59 (dd, Jo ) 7.8, 6.8, 1H,
H12), 4.01 (m, 1H, H5), 3.62 (t, J ) 5.4, 3J(119/117Sn-1H) )
20.4, 2H, H5), 1.44-1.29 (m, 4H, R-CH2-), 1.73-1.48 (m, 4H,
â-CH2-), 1.42-1.15 (m, 4H, γ-CH2-), 1.23 (d, J ) 6, 3H, H14),
0.87 (t, J ) 7.4, 2H, δ-CH3), 0.84 (t, J ) 7.4, 2H, δ-CH3). 13C
NMR: δ 170.9 (2J(119/117Sn-13C) ) 8.0, C7), 170.2 (C9), 136.2
(C11), 134.7 (C13), 122.8 (C10), 117.3 (C8), 115.7 (C12), 68.15
(2J(119/117Sn-13C) ) 22.5, C4), 66.5 (2J(119/117Sn-13C) ) 36.2, C5),
27.9 (2J(119/117Sn-13C) ) 30.5, â-CH2-), 27.3 (3J(119Sn-13C) )
90.0, 3J(117Sn-13C) ) 86.2, γ-CH2-), 21.5 (J(119Sn-13C) ) 628.3,
J(117Sn-13C) ) 599.8, R-CH2-), 14.2 (δ-CH3). 119Sn NMR: δ
-189.5 (CDCl3), -206.1 (DMSO-d6). IR (KBr): ν 2955, 2923,
2852, 1624 (CdN), 1527 (CdN), 1464, 1451, 1145, 861, 596
cm-1.Calcd for C18H29NO2Sn: C, 52.72; H, 7.13; N, 3.42. Found:
1318, 1099, 1055, 793, 756, 739, 699, 662, 580, 522 cm-1
.
Calcd for C21H19NO2Sn: C, 57.84; H, 4.39; N, 3.21. Found: C,
57.69; H, 4.28, N, 3.10. Suitable crystals for the X-ray diffraction
analysis were obtained from the mother liquors after one week of
evaporation.
2,2-Di-phenyl-6-aza-1,3-dioxa-5-ethyl-2-stanna-benzocyclonon-
1
ene (5c). Yellow solid. Yield: 70%. mp: 117-119 °C. H NMR:
3
δ 8.27 (sb, 1H, J(119/117Sn-1H) ) 51.4, H7), 8.02-7.98 (m, 2H,
H-ortho-Sn-Ph), 7.85-7.80 (m, 2H, H-ortho-Sn-Ph), 7.39-7.31
(m, 7H, H-11, H-meta-, H-para-Sn-Ph), 7.08-7.02 (m, 2H,
H-13, H10), 6.65 (t, Jo ) 7.5, 1H, H12), 4.28 (d, J ) 9.6,
3J(119/117Sn-1H) ) 64.0, 1H, H4a), 4.10 (dd, J ) 9.6, 3.8, 1H, H4b),
3.28 (dt, J ) 7.2, 3.8, 3J(119/117Sn-1H) ) 42.0, 1H, H5), 1.88 (sx,
J ) 7.2, 1H, H14a), 1.71 (sx, J ) 7.2, 1H, H14b), 0.93 (t, J ) 7.2,
3H, H15). 13C NMR: δ 170.8 (C7), 169.6 (2J(119/117Sn-13C) )
30.6, C9), 140.7 (J(119Sn-13C) ) 1005.6, J(117Sn-13C) ) 960.5.4,
C-ipso-SnPh), 140.2 (J(119Sn-13C) ) 956.3, J(117Sn-13C) )
911.9, C-ipso-SnPh), 136.6 (2J(119/117Sn-13C) ) 50.5, C-ortho-
(28) Farrugia, L. J. Appl. Crystallogr. 1999, 32, 837.
(29) Farrugia, L. J. Appl. Crystallogr. 1997, 30, 565.
Inorganic Chemistry, Vol. 44, No. 15, 2005 5377

Zamudio-Rivera et al.
SnPh), 136.5 (C11), 134.9 (C13), 129.9 (4J(119/117Sn-13C) ) 15.3,
C-para-SnPh), 128.6 (3J(119/117Sn-13C) ) 78.1, C-meta-SnPh),
128.5 (3J(119/117Sn-13C) ) 84.2, C-meta-SnPh), 122.9 (C10),
Anaerobic bacteria. The anaerobic strains used in this work
were grown in 40 mL flasks in a Postgate C modified medium as
follows: The headspace, in the bottles of medium, was flushed
with nitrogen, and the bottles were sealed (the bottle caps had a
concentric 4.8 mm hole to allow the rubber liner to be punctured
with a syringe when required). The title compounds were injected
into the bottles at seven different concentrations from 1 to 75 ppm,
and then the flasks were inoculated with 1 mL of stock SRBs
culture. All bottles were incubated at 32 °C for 7 days. After this
time, the minimum inhibitory concentration for each compound was
determined by recording the presence or absence of visible growth
in the bottles, compared with positive (bottles without chemicals)
and negative (bottles not inoculated with culture) controls. Two
parallel series with the same conditions were set up for each
compound.
117.3 (3J(119/117Sn-13C)
) 27.6, C8), 116.6 (C12), 70.6
(2J(119/117Sn-13C) ) 38.2, C5), 66.0 (2J(119/117Sn-13C) ) 18.4, C4),
27.9 (C14), 11.7 (C15). 119Sn NMR: δ -334.6 (CDCl3), -337.2
(DMSO-d6). IR (KBr): ν 3051, 2970, 2928, 2882, 2826, 1616
(CdN), 1540 (CdN), 1467, 1445, 1429, 1308, 1203, 1151, 1118,
1088, 765, 733, 699, 592 cm-1. Calcd for C23H23NO2Sn: C, 59.52;
H, 4.99; N, 3.02. Found: C, 59.40; H, 4.78, N, 3.05. Suitable
crystals for the X-ray diffraction analysis were obtained after the
dissolution of 5c in 20 mL of a 6:1 solvent mixture of heptanes
and dichloromethane.
Microbiology. The compounds synthesized were screened in
vitro for their antibacterial activity against three strains of aerobic
bacteria, one Gram-positive (B. subtilis ATCC 6633) and two Gram-
negative (E. coli DH5R and P. aeruginosa BH3) and against two
anaerobic species (D. longus, DSM 6739, and D. aspheronum, DSM
5918). Antimicrobial assays were done by using the agar well
diffusion method30,31 to determine the minimum inhibitory con-
centrations (MICs).
Aerobic bacteria. Seeding agar was prepared in flat-bottomed
90 mm Petri dishes by cooling the TBS molten medium32 to 40 °C
and then adding the required amount of bacterial suspension (8 ×
108 bacteria per mL). Four wells per dish were dug in the media
with the help of a sterile metallic borer with centers of at least 24
mm. Each compound was dissolved in DMSO, at concentrations
of 1 × 10-3, 1 × 10-2, 1.0, 2.5, 5, 10, 25, 50, 75, and 100 ppm.
Fifty microliter samples of each dilution were applied by triplicate
into the corresponding wells, and after that, the Petri dishes were
cooled to 4 °C for 60 min to allow diffusion of the compounds
through the medium. DMSO controls were also included in the
assay. The plates were then incubated at a suitable growth
temperature for the bacteria (30 °C ( 2 °C) for 16 h. The zone of
inhibition of bacterial growth formed around each slot was
accurately measured.
Acute toxicity assays. The acute toxicity of the chemicals
synthesized was assessed using a Microtox analyzer. In the test, a
vial of the P. phosphoreum (V. fischering) culture was reconstituted
in 1 mL of solution and maintained at 3 °C in an incubator well on
the analyzer. For each test, a serial dilution of the compounds was
prepared in 2% brine. In addition, a series of brine solutions
containing approximately 106 colony forming units of P. phos-
phoreum were prepared in glass cuvettes by pipetting 10 µL of the
reconstituted bacterial suspension into 500 µL of 2% brine. As a
bacterial population control, these solutions were incubated in
temperature-controlled wells (6 °C) for 15 min and measured.
Hence, the activity of treated compounds was recorded after 5 and
15 min of exposure. The results of Microtox test are expressed in
terms of the EC50 value.
Acknowledgment. We thank Programa de Ingenier´ıa
Molecular-IMP for financial support from project D.00178.
Supporting Information Available: Crystallographic data in
CIF format for compounds 4b, 4c, 5a, and 5c. This material is
available free of charge via the Internet at http://pubs.acs.org. Full
crystallographic data, CCDC numbers 269982 for 4b, 269983 for
4c, 269984 for 5a, and 269985 for 5c, is available from the
Cambridge Crystallographic Data Center, CCDC, 12 Union Road,
Cambridge CB21EZ, UK (Fax: +44-1223-336033. E-mail:
deposit@ccdc.cam.ac.uk. Website: http://www.ccdc.cam.ac.uk).
(30) Chohan, Z. H.; Scozzafava, A.; Supuran, C. T. Synth. React. Inorg.
Met.-Org. Chem. 2003, 33, 241.
(31) Atta-ur-Rahman; Choudhary, M. I.; Thomsen, W. J. Bioassay Tech-
niques for Drug DeVelopment. Harwood Academic OPA N. V.;
Amsterdam, The Netherlands, 2001; p 16.
(32) Sambrook, J.; Fritsch, E. F.; Maniatis, T. Molecular Cloning:
A
Laboratory Manual, 3rd ed; Cold Spring Harbor Laboratory: New
York, 2001; 3 vols.
IC048628O
5378 Inorganic Chemistry, Vol. 44, No. 15, 2005