Bis-diorganotin(IV) complexes with binucleating hydrazones derived from a methylene-bis-aromatic aldehyde as linker: Synthesis, spectral and structural characterization, antibacterial activity and DNA cleavage studies

Article abstract of DOI:10.1016/j.jorganchem.2017.10.040

Two bis-hydrazone, H₄L^a and H₄L^b, have been synthesized from reaction of 5,5′-methylene-bis-salicylaldehyde with benzhydrazide and furan-2-carbohydrazide, respectively. New organotin(IV) complexes, (R₂

Full text of DOI:10.1016/j.jorganchem.2017.10.040

Accepted Manuscript
Bis-diorganotin(IV) complexes with binucleating hydraznones derived from a
methylene-bis-aromatic aldehyde as linker: Synthesis, spectral and structural
characterization, antibacterial activity and DNA cleavage studies
Hamidreza Zafarian, Tahereh Sedaghat, Hossein Motamedi, Damian Trzybiński,
Krzysztof Woźniak
PII:
S0022-328X(17)30627-7
10.1016/j.jorganchem.2017.10.040
JOM 20160
DOI:
Reference:
To appear in: Journal of Organometallic Chemistry
Received Date: 31 July 2017
Revised Date: 25 October 2017
Accepted Date: 30 October 2017
Please cite this article as: H. Zafarian, T. Sedaghat, H. Motamedi, D. Trzybiński, K. Woźniak, Bis-
diorganotin(IV) complexes with binucleating hydraznones derived from a methylene-bis-aromatic
aldehyde as linker: Synthesis, spectral and structural characterization, antibacterial activity and DNA
cleavage studies, Journal of Organometallic Chemistry (2017), doi: 10.1016/j.jorganchem.2017.10.040.
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ACCEPTED MANUSCRIPT
Bis-diorganotin(IV) complexes with binucleating hydraznones derived from a methylene-
bis-aromatic aldehyde as linker: Synthesis, spectral and structural characterization,
antibacterial activity and DNA cleavage studies
Hamidreza Zafarian a, Tahereh Sedaghat a*, Hossein Motamedi b,c, Damian Trzybińskid,
Krzysztof Woźniakd
aDepartment of Chemistry, Faculty of Sciences, Shahid Chamran University of Ahvaz, Ahvaz,
Iran
bDepartment of Biology, Faculty of Sciences, Shahid Chamran University of Ahvaz, Ahvaz, Iran
c Biotechnology and Biological Science Research Center, Shahid Chamran University of Ahvaz,
Ahvaz, Iran
d
Department of Chemistry, Biological and Chemical Research Centre, University of Warsaw,
Żwirki i Wigury 101, 02-089 Warszawa, Poland
*corresponding author: tsedaghat@scu.ac.ir , Fax: 98 611 3331042
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Abstract
Two bis-hydrazone, H4La and H4Lb, have been synthesized from reaction of 5,5'-methylene-bis-
salicylaldehyde with benzhydrazide and furan-2-carbohydrazide, respectively. New
organotin(IV) complexes, (R2Sn)2L [L = La: R = Me (1), Ph (2); L= Lb: R = Me (3), Ph (4)] have
been synthesized by reaction of dihydrazone ligands with R2SnCl2 (R = Me or Ph). The
synthesized compounds have been investigated by elemental analysis and IR, 1H NMR, and
119Sn NMR spectroscopy. The structures of 1 and 2 have been also confirmed by X-ray
crystallography. The results show that the dihydrazone acts as a tetrabasic ligand in the enolic
form and is coordinated to two SnR2 moieties via ONO donor domains by the imine nitrogen and
phenolic and enolic oxygen atoms. All complexes are binuclear and the coordination number of
both tin is five. The in vitro antibacterial activity of ligands and complexes has been evaluated
against Gram-positive (Bacillus subtilis and Staphylococcus aureus) and Gram-negative
(Escherichia coli and Pseudomonas aeruginosa) bacteria and compared with standard drugs. The
synthesized compounds also have been investigated for the chromosomal and plasmid DNA
cleavage activity. The complexes significantly inhibited bacterial growth, while none of
compounds showed DNA cleavage activity.
Keywords: Hydrazone, Organotin, Antibacterial activity, Binuclear complexes
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Introduction
Organotin(IV) chemistry has received continuing attention during the past decades. The
considerable interest in these complexes is due to their industrial, agricultural and medicinal
applications and the diversity of their structures [1-6]. Among the non-platinum compounds
exhibiting anticancer properties, organotin complexes have a valuable place, so that up to now
many organotin(IV) compounds have been synthesized and their anticancer activity in
comparison to traditional metal anticancer drugs tested [7-10], although the toxicology of
organotin compounds may limit their clinical application [11-14]. Biocidal properties of
organotin(IV) compounds are dependent on the number and nature of the organic groups, the
structure and coordination number of complex and the nature of the donor ligand coordinated to
the tin atom [15, 16]. According to the literature, a judicious choice of the ligand attached to the
organotin(IV) fragment can improve the biological properties of the complex or reduce side
effects [15]. In the field of bioorganotin chemistry one of the interesting research areas is to use
bioactive ligands [17]. Among the bioactive ligands, hydrazones are very significant because of
their potential biological applications. The study of organotin complexes of hydrazones is highly
considered because of their therapeutic and antibacterial activity [18-20].
In the field of hydrazone chemistry, a special place is held by bis-acyl-/aroyl-hydrazones
containing amide, azomethine and phenol functional groups. These compounds recently are
recognized as polyfunctional ligands and are able to form supramolecular architectures and
mono- and polynuclear complexes. A survey of literature shows that although many transition
metal complexes of bis-hydrazones have been studied [21], but binuclear organotin(IV)
complexes of this type of ligands have not been reported much [22-29]. Bis-acyl-/aroyl-
hydrazones can be divided into two basic structural categories: those that are derived from a
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dihydrazide and those that are derived from a dialdehyde (or diketone). To our knowledge,
despite the some reports about chelating behavior of the former with organotins [22-29], there
are no work on structural chemistry of organotin(IV) complexes with the latter.
We have recently reported the synthesis, structural and antibacterial properties of a
series of dinuclear organotin(IV) complexes with bis-acyl-hydrazones derived from dihydrazides
[24, 25, 27, 29]. In continuation of our research works, in this study we planned to use a
methylene-bis-aromatic aldehyde as linkers for the synthesis of two new bis-hydrazones. Then
four new dinuclear organotin(IV) complexes have been synthesized from these hydrazones. We
visualized that the flexibility or distance introduced in this bifunctional aldehydes may be have
advantageous and interesting structural features. Spectral and structural properties and biological
activity of ligands and complexes have been reported.
2. Experimental
2.1. Materials and methods
All starting materials were purchased from Merck while diphenyltin dichloride was supplied
from Acros Company and all were used as received. Synthesis of 5,5'-methylene-bis-
salicylaldehyde involves the use of 1,3,5-trioxane in presence of catalytic amount of conc. H2SO4
in glacial CH3COOH as a solvent according to the procedure described in the literature [30]. The
IR spectra were obtained using a FT BOMEM MB102 spectrophotometer. The 1H and 119Sn
NMR spectra were recorded with Bruker Avance Ultrashield spectrometers using TMS and
SnMe4 as references, respectively. The elemental analyses for C, H, N and S were performed on
a Costech-ECS 4010 CHNSO analyzer.
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2.2. Synthesis of H4La
5,5'-methylene-bis-salicylaldehyde (0.256 g, 1 mmol) was added to a stirring solution of
benzhydrazide (0.272 g, 2 mmol) in ethanol (15 mL). The resulting solution was refluxed for 4 h.
The white solid was filtered and washed with ethanol and dried in vacuum over CaCl2. Yield:
0.415 g (84.6%). FT-IR (KBr, cm-1): ν(O−H), 3225; ν(N−H), 3150; ν(Ar−H), 3056; ν(C=O),
1652; ν(C=N), 1619. 1H NMR (250 MHz, DMSO-d6): δ = 12.05 (s, 2H, OH), 11.03 (s, 2H, NH),
8.60 (s, 2H, CH=N), 7.90 (d, 4H, H1, 3JHH = 6.7 Hz), 7.61-7.48 (m, 6H, H2,3), 7.40 (s, 2H, Ha),
7.13 (dd, 2H, Hb, 3JHH = 8.0 Hz), 6.85 (d, 2H, Hc, 3JHH = 8.2 Hz), 3.83 (s, 2H, CH2).
2.3. Synthesis of H4Lb
Ligand H4Lb was synthesized as described for 1 from 5,5'-methylene-bis-salicylaldehyde (0.256
g, 1 mmol) and furan-2-carbohydrazide (0.252 g, 2 mmol) in ethanol (15 mL). The resulting
solution was refluxed and the white solid was filtered after 4 h. The product was washed with
ethanol and dried in vacuum over CaCl2. Yield: 0.379 g (80.3%). FT-IR (KBr, cm-1): ν(O−H),
3222; ν(N−H), 3150; ν(Ar−H), 3056; ν(C=O), 1658; ν(C=N), 1620. 1H NMR (250 MHz,
DMSO-d6): δ = 12.08 (s, 2H, OH), 10.91 (s, 2H, NH), 8.63 (s, 2H, CH=N), 7.97 (s, 2H, H1), 7.42
(s, 2H, Ha), 7.31 (d, 2H, H3, 3JHH = 2.5 Hz), 7.15 (d, 2H, Hb, 3JHH = 7.5 Hz), 6.86 (d, 2H, Hc, 3JHH
= 7.5 Hz), 6.72 (s, 2H, H2), 3.86 (s, 2H, CH2).
2.4. Synthesis of Me4Sn2La (1)
A mixture of H4La (0.123 g, 0.25 mmol) and triethylamine (1 mmol) was stirred in ethanol (10
mL) for 20 min. After this time Me2SnCl2 (0.110 g, 0. 5 mmol) in ethanol (5 mL) was added.
The solution was refluxed for 4 h. A yellow precipitate was formed during the reaction. The
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product was collected, washed with ethanol (5 mL) and dried in vacuum over CaCl2. Yield:
0.141 g (71.9%). Light-yellow plate crystals suitable for X-ray crystallography were obtained in
benzene/chloroform solution. Anal. Calcd. for C33H32N4O4Sn2: C, 50.4; H, 4.1; N, 7.1%. Found:
C, 50.9; H, 3.8; N, 7.4%. FT-IR (KBr, cm-1): ν(C=N), 1616; νas(Sn−C), 637; νs(Sn−C), 570;
ν(Sn−O), 527; ν(Sn−N), 451. 1H NMR (250 MHz, DMSO-d6): δ = 8.81 (s, 2H, CH=N, 3J(119Sn-
1H) = 43.0 Hz), 8.00 (d, 4H, H1, 3JHH = 7.3 Hz), 7.53-7.42 (m, 6H, H2,3), 7.27 (s, 2H, Ha), 7.16 (d,
2H, Hb, 3JHH = 8.3 Hz), 6.63 (d, 2H, Hc, 3JHH = 8.5 Hz), 3.71 (s, 2H, CH2), 0.68 [s, 6H, Me2Sn,
2J(119Sn-1H) = 86.8 Hz]. 119Sn NMR (149 MHz, DMSO): δ = −211.3
2.5. Synthesis of Ph4Sn2La (2)
Compound 2 was synthesized as described for 1 from H4La (0.123 g, 0.25 mmol), triethylamine
(0.5 mmol) and Ph2SnCl2 (0.172 g, 0. 5 mmol). Yellow needle crystals suitable for X-ray
crystallography were obtained in benzene/chloroform solution.Yield: 0.214 g (82.9%). Anal.
Calcd for C53H40N4O4Sn2: C, 61.5; H, 3.9; N, 5.4%. Found: C, 61.4; H, 3.6; N, 5.7%. FT-IR
(KBr, cm-1): ν(Ar−H), 3053; ν(C=N), 1619; ν(Sn−O), 534; ν(Sn−N), 444. 1H NMR (250 MHz,
DMSO-d6): δ = 8.75 (s, 2H, CH=N, 3J(119Sn-1H) = 52.0 Hz), 8.12 (d, 4H, H1, 3JHH = 7.0 Hz),
7.63 (d, 8H, Hortho of SnPh2, 3JHH = 5.7 Hz), 7.35-7.32 (m, 14H, Hmeta,para of SnPh2 and Ha), 7.52-
7.49 (m, 6H, H2,3), 7.22 (d, 2H, Hb, 3JHH = 8.9 Hz), 6.86 (d, 2H, Hc, 3JHH = 8.5 Hz), 3.74 (s, 2H,
CH2). 119Sn NMR (149 MHz, DMSO): δ = −410.7
2.6. Synthesis of Me4Sn2Lb (3)
A mixture of H4Lb (0.118 g, 0.25 mmol) and triethylamine (1 mmol) was stirred in ethanol (10
mL) for 20 min. Then Me2SnCl2 (0.110 g, 0. 5 mmol) in ethanol (5 mL) was added. The solution
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was refluxed for 4 h. The product was obtained as yellow solid. The precipitate was filtered,
washed with ethanol (5 mL) and dried in vacuum over CaCl2. Yield: 0.588 g (79.2%). Anal.
Calcd for C27H28N4O6Sn2: C, 43.7; H, 3.8; N, 7.5%. Found: C, 43.4; H, 3.5; N, 7.7%. FT-IR
(KBr, cm-1): ν(C=N), 1617; νas(Sn−C), 625; νs(Sn−C), 568; ν(Sn−O), 525; ν(Sn−N), 484. 1H
NMR (250 MHz, DMSO-d6): δ = 8.73 (s, 2H, CH=N, 3J(119Sn-1H) = 36.2 Hz), 7.84 (s, 2H, H1),
7.23 (s, 2H, Ha), 7.14 (d, 2H, Hb, 3JHH = 8.7 Hz), 6.99 (d, 2H, H3, 3JHH = 3.0 Hz), 6.32-6.60 (m,
4H, H2,c), 3.70 (s, 2H, CH2), 0.67 [s, 6H, Me2Sn, 2J(119Sn-1H) = 88.5 Hz]. 119Sn NMR (149 MHz,
DMSO): δ = −224.1
2.7. Synthesis of Ph4Sn2Lb (4)
Compound 4 was synthesized as described for 3 from Ph2SnCl2 (0.172 g, 0. 5 mmol). The
product was obtained as yellow solid. Yield: 0.214 g (82.9%). Anal. Calcd for C49H36N4O6Sn2:
C, 58.0; H, 3.6; N, 5.5%. Found: C, 58.2; H, 3.7; N, 5.3%. FT-IR (KBr, cm-1): ν(C=N), 1616;
ν(Sn−O), 540; ν(Sn−N), 446. 1H NMR (250 MHz, DMSO-d6): δ = 8.74 (s, 2H, CH=N, 3J(119Sn-
1H) = 56.0 Hz), 8.14 (s, 2H, H1), 8.11 (s, 2H, Ha), 7.64-7.61 (m, 8H, Hortho of SnPh2), 7.57-7.47
(m, 4H, H2,3), 7.35-7.33 (m, 14H, Hmeta,para of SnPh2), 7.20 (d, 2H, Hb, 3JHH = 8.7 Hz), 6.86 (m,
2H, Hc, 3JHH = 8.5 Hz), 3.74 (s, 2H, CH2). 119Sn NMR (149 MHz, DMSO): δ = −422.0
2.8. Antibacterial tests
In order to evaluate the antibacterial activity of ligand and complexes four different
concentrations including 2.5, 5, 10 and 20 mg/mL were prepared in DMSO and sterile blank
discs (6.4mm) were saturated by these solutions. So, the effective dose per disc was as 0.1, 0.2,
0.4 and 0.8 mg, respectively. The Escherichia coli (ATCC25299), Pseudomonas aeruginosa
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(ATCC9027), Bacillus subtilis (ATCC6633) and Staphylococcus aureus (ATCC6538) were
selected as target bacterial species and the antibacterial effect of prepared compounds were
surveyed according to the Kirby-Bauer standard disc diffusion method. 0.5 McFarland
suspensions of bacterial cultures were lawn cultured on Mueller-Hinton agar (MHA, Merck,
Germany), the prepared discs were placed on these cultures and plates were incubated at 37°C
for 24 h. Finally, the inhibition zone diameter (mm) of each disc was measured and recorded. In
order to compare the results, the effect of standard antibiotic discs including Vancomycin,
Streptomycin, Penicillin, Nalidixic acid and Gentamicin were studied as previously mentioned.
Furthermore, the effect of DMSO saturated disc as negative control was also investigated against
bacterial species as previously described.
2.9. Gel electrophoresis assay
The DNA of B. subtilis and E. coli was extracted by boiling method. One mL of each bacterial
suspension was centrifuged at 10000 rpm for 10 min. The precipitate was dissolved in 1 mL of
sterile distilled water and boiled for 15 min. The mixture was centrifuged (5000 rpm, 1 min) and
the supernatant was harvested and mixed with cold ethanol (2.5 v/v) and stored overnight at -20
°C. Finally, following centrifugation at 13000 rpm for 10 min, the precipitate was dissolved in
100 µL of DNase free sterile water and stored at -20 °C. Plasmid DNA was also extracted by
plasmid extraction kit (Qiagen, Germany). 10 µL of 20 mg/mL solution of each compound in
DMSO was mixed with 10 µL of DNA and incubated at 37 °C for 2 h. A positive control was
also prepared by mixing 10 µL of H2O2 with 10 µL of DNA and untreated DNA was regarded as
negative control. These DNA samples were electrophoresed in 1% agarose containing DNA safe
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stain at 100 V for 50 min. A 1 Kb DNA ladder was used as size marker. The gel was documented
with UVI-Tec gel documentation system.
2.10. X-ray structure determination
Good quality single-crystals of 1 and 2 were selected for the X-ray diffraction experiments.
Diffraction data were collected at T = 100(2) K on the Agilent Technologies SuperNova Dual
Source (1) and Agilent Technologies Supernova Single Source (Mo) (2) diffractometers with
MoKα radiation (λ = 1.54184 Å) using CrysAlis RED software [31]. In both cases the analytical
numerical absorption correction using a multifaceted crystal model based on expressions derived
by R.C. Clark & J.S. Reid [32] implemented in SCALE3 ABSPACK scaling algorithm, was
applied [31]. The structural determination procedure was carried out using the SHELX package
[33]. The structures were solved with direct methods and then successive least-square refinement
was carried out based on the full-matrix least-squares method on F2 using the XLMP program
[33]. All H-atoms were positioned geometrically, with the C–H bond lengths set to be equal to
0.93 and 0.96 Å for the aromatic and methyl H-atoms, respectively, and constrained to ride on
their parent atoms with Uiso(H) = xUeq(C), where x = 1.2 for the aromatic, and x = 1.5 for the
methyl H-atoms. In the case of 2, few distinct peaks on the difference Fourier map are indicating
the presence of a disordered solvent molecule. All attempts to model this small disorder of
solvent molecules used for crystallization failed. Therefore, the solvent contribution has been
removed applying the appropriate MASK procedure in the Olex2 program [34]. Calculated void
volume was approximately 491.7 Å3 occupied by 49.6 electrons per unit cell. The figures for this
publication were prepared using Olex2 and ORTEP-3 programs [34, 35]. The molecular
interactions in crystals were identified using PLATON [36].
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3. Results and discussion
Dihydrazones, H4La and H4Lb, have been obtained from condensation of 5,5'-methylene-bis-
salicylaldehyde with benzhydrazide and furan-2-carbohydrazide, respectively. Therefore
methylene-bis-aromatic aldehyde acts as flexible linker for the preparation of binucleating
ligands (Figure 1). The flexibility present in the –CH2− moiety of the linker allows the ligand or
their complexes to adopt different orientations. It may be supposed that in solution there is a fast
dynamic equilibrium between different conformations [37]. These bis-hydrazone ligands have
potentially six donor atoms with four ionizable protons and two tridentate domain.
The binuclear organotin complexes 1-4 (Figure 1) were prepared by reaction of H4La and
H4Lb with R2SnCl2 (R = Me and Ph) in presence of triethylamine in 1:2:4 ratio. The new
complexes were characterized by elemental analysis and IR, 1H and 119SnNMR spectroscopy.
Stoichiometry of the complexes was confirmed by analytical data and the integrated 1H NMR
spectra. The structure of 1and 2 has been also determined by X-ray diffraction.
3.1. X-ray structures
The identity of 1 and 2 was proven by the single-crystal X-ray diffraction analysis. It turned out
that the complex 1 crystallizes in the monoclinic P21/c space group with four molecules of
compound in the unit cell (one in the asymmetric part of the unit cell), whereas the compound 2
is crystallizes in triclinic P-1 space group and in this case two molecules of complex are present
in the unit cell (again one in the asymmetric part of the unit cell - see Figure 2). The details of
crystallographic data and the refinement parameters are summarized in Table 1. Selected bond
lengths and angles are listed in Tables 2 and 3. Both investigated complexes are binuclear and
structural parameters describing two parts of molecule are similar. The dihydrazone moiety acts
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as a tetrabasic ligand and exists in the enol form. It is coordinated to the two Sn atoms via the
imine nitrogen atom and the enolate, and phenolate oxygen atoms. Thus each tridentate pocket
forms six and five-membered chelate ring around the SnR2 moiety. Above-mentioned chelate
rings are not planar, however the values of the torsion angles describing these molecular
fragments are quite small (Tables 2 and 3). The coordination sphere of each Sn atom is
completed by two carbon atoms of organic groups. Therefore, the coordination number of each
Sn atoms is five. The index of trigonality, τ, can be defined: τ = (α − β)/60, and it quantifies the
extent of distortion from either the ideal square pyramid or trigonal bipyramid, wherein α and β
are the two largest bond angles around the metal atom in the five-coordinated environment [38].
The trigonality index is equal to zero for an ideal square pyramidal geometry, while it becomes
unity for ideal trigonal bipyramidal geometry. In the complex 1, the τ value is 0.335 and 0.411
for Sn1 and Sn2 atoms, respectively, therefore the metal coordination geometry around both Sn
atoms can be described as highly distorted square pyramid. This distortion from perfect
geometries is mainly due to the rigidity of chelate rings, and facilitated by the large covalent
radius of tin(IV) [39, 40]. The imine nitrogen is chosen as apex of square pyramid because any
four donor atoms which define the two largest angles, α and β, should not be in apical position.
According to the complex 2 in this case the trigonality index is 0.427 and 0.520 for Sn1 and Sn2
atoms, respectively. These values indicate that the geometry around the Sn1 atom is highly
distorted square pyramid with one of the phenyl carbon atoms occupying the axial position. The
Sn2 atom coordination geometry is almost midway the idealized square-pyramidal and trigonal-
bipyramidal geometries. However, with particular precision, trigonal-bipyramidal with oxygen
atoms in the axial positions predominates. As in the case of 1, distortions from the ideal
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geometries in 2 are mainly caused by the rigidity of chelate rings, and facilitated by the large
covalent radius of tin (IV).
The Sn−N bond lengths are very similar to the sum of the covalent radii of Sn−N (2.15
Ǻ), but are considerably shorter than the sum of Van der Waals radii (3.75 Ǻ) [41, 42]. The
Sn−Ophenolic and Sn−Oenolic distances are also similar to the sum of the covalent radii of Sn−O
(2.10 Ǻ). Therefore, there is a very strong covalent bond between tin and oxygen and nitrogen
atoms. In the complex 1, the difference between the C−Sn−C angle from the X-ray diffraction
data, 134.85° and 130.13°, and the empirical estimation in solution (139.4° and 141.9°) calculating
in section 3.2, may be related to the removal of the crystal network pressure in solution and also
probable interaction with DMSO as a coordinating solvent.
In the crystal of 1, adjacent molecules of the investigated complex are held together by
the weak C−H···N hydrogen bonds and C−H···π contacts (Tables 1S and 2S) and this results in
the formation of infinite chains running along crystallographic b-direction (Figure 3a).
Neighboring chains in the crystal structure are further stabilized by the network of C−H···π
intermolecular interactions (Table 2S) and, finally, a complex supramolecular framework arises
(Figure 3b).
In the case of 2, the adjacent molecules of the complex are involved in the network of
intermolecular C−H···π contacts (Figure 4, Table 3S). These weak interactions stabilize the
crystal structure.
3.2. Spectroscopic studies
In the IR spectra of free ligands a band observed about 3220 cm-1 is attributable to stretching
vibration of OH indicating inter-/intra-molecular hydrogen bonding. In the spectra of complexes
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the absence of any bands for ν(O-H), ν(N-H) and ν(C=O) shows the complete deprotonation of
the ligand and coordination with tin in the enolate form [18]. The ν(C=N) band which appears
about 1620 cm-1 in the spectra of ligands is shifted to a lower frequency for complexes. This
observation indicates that the imine nitrogen atom is involved in coordination to the tin. In the IR
spectra of complexes new bands were observed in the range ~400-600 cm-1 related to Sn−N and
Sn−O stretching frequency. The appearance of these bands confirms coordination of nitrogen
and oxygen to the tin atom [43-45]. Presence of both νs(Sn−C) and νas(Sn−C) in the IR spectrum
of 1 and 3 suggests a nonlinear Me-Sn-Me configuration.
The 1H NMR spectral data of complexes in DMSO is presented in the experimental
section according to the atomic numbering shown in Figure 1. The complete absence of the
signals due to the acidic protons, –NH-N= and Ar-OH, suggests the complete deprotonation of
ligand and coordination to the tin in the enolate form. In the 1H NMR spectra of complexes, the
ratio of the integrals of the signals from the protons of the ligand to the protons of the organic
groups on the tin confirms a 2:1 ratio of metal to ligand in the complexes. The appearance of
only one set of signals in 1H NMR of H2La and H2Lb shows the magnetically equivalence of two
the parts of molecules. A signal attributed to two imine protons in the spectrum of free ligands is
slightly shifted downfield and accompanied by satellites due to 3J(119Sn-H) coupling in all
complexes. Appearance of only one signal for both imine protons flanked by satellites is an
evidence that the two imine nitrogen atoms are magnetically equivalent in solution and both are
coordinated to tin(IV) centers. The 1HNMR spectrum of 1 and 3 shows a singlet at upfield for
SnMe2 protons accompanied by satellites due to 2J(119Sn-1H). This coupling constant is larger
than uncomplexed Me2SnCl2 (68.7 Hz) indicates the increasing coordination number of tin [26].
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Substitution of 2J(119Sn-1H) in the Lockhart-Manders equation [46], θ = 0.016|2J|2 −1.32|2J| +
133.4, gives a value of 139.4° and 141.9° for Me-Sn-Me angles in 1 and 3, respectively.
The 119Sn NMR spectra of all complexes show only one sharp singlet indicates the
existence of a single species in solution and show the similar environment for both tin centers in
complex. The 119Sn chemical shifts show large up-field shift in comparison to the original
Me2SnCl2 (+137 ppm) and Ph2SnCl2 (-32 ppm) [47] which is in agreement with the increasing of
the coordination number of tin. These shifts are in the range reported empirically for five-
coordinate diorganotin(IV) complexes [37, 48-50], therefore the coordination number of both tin
in binuclear complexes is five in solution. The chemical shifts are appeared at up-field for
diphenyltin complexes in comparison to dimethyl ones, due to anisotropic shielding effects and
pi interactions [26].
3.3. Antibacterial activity and DNA cleavage
The synthesized ligands and their organotin(IV) complexes were screened against Bacillus
subtilis and Staphylococcus aureus (as Gram-positive bacteria) and Escherichia coli and
Pseudomonas aeruginosa (as Gram-negative bacteria) to assess their antibacterial activity. The
results are given in Table 4 in comparison with the standard antibacterial drugs, viz,
Vancomycin, Streptomycin, penicillin, Nalidixic acid and Gentamycin. An inhibition zone
diameter over 7 mm can represent activity against bacteria under investigation [51] . The
synthesized compounds also have been investigated for their chromosomal and plasmid DNA
cleavage activity by agarose gel electrophoresis method.
The results showed the free ligands are inactive against all tested bacteria. While all
complexes, except 4 against E.coli, significantly inhibited bacterial growth. None of compounds
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showed DNA cleavage activity against both chromosomal and plasmid DNA. The enhanced
antibacterial activity of the ligand on complexation with organotin(IV) precursors can be
explained according to Overton’s concept and Tweedy’s chelation theory [52, 53], as well as it
may be due to the intrinsic biological activity effects of organotin moiety [15, 27, 54]. On the
basis of Overton’s concept, lipophilicity is an important factor, which controls the antimicrobial
activity, because the lipid layer of the cell membrane favors the permeation of only the lipid-
soluble materials, i.e., hydrophobic substances. According to chelation theory, the polarity of
metal ions will be reduced upon complexation. As consequence, upon complexation the
lipophilic nature of the central Sn atom enhances which favors the passage of the complexes
through cell membrane [24, 29, 55-60]. Two main factors are responsible for this reduction in
polarity; firstly the partial sharing of metal positive charge with donor atoms of ligand and
secondly the overlap of ligand orbitals and electron delocalization over the whole chelate [61].
The higher activity of 1 and 2 than 3 and 4 may also be attributed to the lipophilicity increased
by the presence of two phenyl groups instead of furan rings. It is noteworthy that all complexes
especially 1 are remarkably active against P. aeruginosa while, the bacteria of the genus
Pseudomonas are resistant to many standard drugs [62, 63].
According to the results of antibacterial activity and DNA cleavage, all complexes can
inhibit the growth and multiplication of the bacteria by affecting bacterial cell envelope or
possibly interfering with metabolic pathways whereas, it is not harmful for DNA structure. The
absence of destructive effect on bacterial DNA can be an advantage; hence these complexes can
be used safely for bacterial growth control in environment without any side effects on eukaryotic
DNA. In other word, these compounds will not be mutagen for eukaryotic cells.
15

ACCEPTED MANUSCRIPT
Comparing the results of this research with our previous works [24, 27, 29, 54, 55, 60,
64] confirm that the lipophilicilty of both organic groups and donor ligand coordinated to the
organotin(IV) fragment has a great impact on the improvement of biological properties of
organotin(IV) compounds. Therefore a judicious choice of organic groups and the substituents in
the donor ligand can modulate the activity of the complex. Among the studied diorganotin(IV)
complexes, the high activity was exerted by [Ph2Sn(IV)]2+ complexes.
Conclusion
Dihydrazones which contain two similar ONO tridentate domains, are completely deprotonated
and bonded to two diorganotin moiety via the imine nitrogen and phenolic and enolic oxygen
atoms. All complexes are binuclear and both tin atoms have similar environment with
coordination number of five. In most cases, the complexes exhibit significantly antibacterial
activity against all tested bacteria, but do not show any DNA cleavage activity. Therefore DNA
cleavage is not considered as a bactericidal mechanism for these complexes.
Acknowledgment
Support of this work by Shahid Chamran University of Ahvaz, Ahvaz, Iran (Grant No. 1396) is
gratefully acknowledged. The crystallographic part of this study was carried out at the Biological
and Chemical Research Centre, University of Warsaw, established within the project co-financed
by European Union from the European Regional Development Fund under the Operational
Programme Innovative Economy, 2007 – 2013. This study was also supported by the National
Science Centre Poland MAESTRO grant-DEC-2012/04/A/ST5/00609 (DT and KW), which
enabled the X-ray structural analysis to be performed.
16

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Appendix A. Supplementary material
CCDC 1517341 and 1517372 contains the supplementary crystallographic data for 1 and 2,
respectively. These data can be obtained free of charge via
http://www.ccdc.cam.ac.uk/conts/retrieving.html, or from the Cambridge Crystallographic Data
Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: +44 1223 336 033; or e-mail:
deposit@ccdc.cam.ac.uk.
References
[1] P.J. Smith, Chemistry of tin, Springer Science & Business Media, 2012.
[2] M. Gielen, Tin chemistry: fundamentals, frontiers, and applications, John Wiley & Sons,
2008.
[3] S. Etezadi, A. Koppaka, M.M. Gamage, B. Captain, J. Organomet. Chem., 848 (2017) 122-
132.
[4] A. Koppaka, L. Zhu, V. Yempally, D. Isrow, P.J. Pellechia, B. Captain, J. Am. Chem. Soc.,
137 (2014) 445-456.
[5] O.T. Summerscales, M.M. Olmstead, P.P. Power, Organometallics, 30 (2011) 3468-3471.
[6] K.K. Pandey, P.P. Power, Organometallics, 30 (2011) 3353-3361.
[7] M.K. Amir, S. Khan, R. Zia ur, A. Shah, I.S. Butler, Inorg. Chim. Acta, 423 (2014) 14-25.
[8] C.E. Carraher, M.R. Roner, J. Organomet. Chem., 751 (2014) 67-82.
[9] S.K. Hadjikakou, N. Hadjiliadis, Coord. Chem. Rev., 253 (2009) 235-249.
[10] F. Arjmand, S. Parveen, S. Tabassum, C. Pettinari, Inorg. Chim. Acta, 423 (2014) 26-37.
[11] T. Hamasaki, T. Sato, H. Nagase, H. Kito, Mutat. Res. Gen. Toxicol., 300 (1993) 265-271.
[12] J.S. White, J.M. Tobin, J.J. Cooney, Can. J. Microbiol., 45 (1999) 541-554.
17

ACCEPTED MANUSCRIPT
[13] L. Niu, Y. Li, Q. Li, Inorg. Chim. Acta, 423 (2014) 2-13.
[14] A. Pagliarani, S. Nesci, V. Ventrella, Toxicol. in Vitro, 27 (2013) 978-990.
[15] C. Pellerito, L. Nagy, L. Pellerito, A. Szorcsik, J. Organomet. Chem., 691 (2006) 1733-
1747.
[16] X. Song, A. Zapata, G. Eng, J. Organomet. Chem., 691 (2006) 1756-1760.
[17] L. Pellerito, L. Nagy, Coord. Chem. Rev., 224 (2002) 111-150.
[18] K. Liu, H. Yan, G. Chang, Z. Li, M. Niu, M. Hong, Inorg. Chim. Acta, 464 (2017) 137-146.
[19] Y. Yang, M. Hong, L. Xu, J. Cui, G. Chang, D. Li, C.-z. Li, J. Organomet. Chem., 804
(2016) 48-58.
[20] C. González-García, A. Mata, F. Zani, M.A. Mendiola, E. López-Torres, J. Inorg. Biochem.,
163 (2016) 118-130.
[21] A.-M. Stadler, J. Harrowfield, Inorg. Chim. Acta, 362 (2009) 4298-4314.
[22] M.P. Degaonkar, V.G. Puranik, S.S. Tavale, S. Gopinathan, C. Gopinathan, B. Chem. Soc.
Jpn, 67 (1994) 1797-1801.
[23] H.-d. Yin, J.-c. Cui, Y.-l. Qiao, Polyhedron, 27 (2008) 2157-2166.
[24] T. Sedaghat, M. Aminian, G. Bruno, H. Amiri Rudbari, J. Organomet. Chem., 737 (2013)
26-31.
[25] T. Sedaghat, M. Aminian, H. Amiri Rudbari, G. Bruno, J. Organomet. Chem., 754 (2014)
26-31.
[26] S. Shujah, N. Muhammad, A. Shah, S. Ali, A. Meetsma, Z. Hussain, J. Organomet. Chem.,
759 (2014) 19-26.
[27] T. Sedaghat, M. Aminian, M. Azarkish, Phosphorus, Sulfur, and Silicon and the Related
Elements, 190 (2015) 352-359.
18

ACCEPTED MANUSCRIPT
[28] D.K. Dey, S.P. Dey, N.K. Karan, A. Lyčka, G.M. Rosair, J. Organomet. Chem., 749 (2014)
320-326.
[29] H. Zafarian, T. Sedaghat, H. Motamedi, H.A. Rudbari, J. Organomet. Chem., 825 (2016)
25-32.
[30] C. Marvel, N. Tarköy, J. Am. Chem. Soc., 79 (1957) 6000-6002.
[31] CrysAlis CCD and CrysAlis Red, Oxford Diffraction, Oxford Diffraction Ltd, Yarnton,
England, 2008.
[32] R. Clark, J. Reid, Acta Cryst. Sect. A 51 (1995) 887-897.
[33] G.M. Sheldrick, Acta Crystallogr., Sect. A: Found. Crystallogr., 64 (2008) 112-122.
[34] O.V. Dolomanov, L.J. Bourhis, R.J. Gildea, J.A. Howard, H. Puschmann, J. Applied Cryst.,
42 (2009) 339-341.
[35] L.J. Farrugia, J. Appl. Cryst., 45 (2012) 849-854.
[36] A. Spek, Acta Cryst. D, 65 (2009) 148-155.
[37] V. Barba, E. Vega, R. Luna, H. Höpfl, H.I. Beltrán, L.S. Zamudio-Rivera, J. Organomet.
Chem., 692 (2007) 731-739.
[38] A.W. Addison, T.N. Rao, J. Reedijk, J. van Rijn, G.C. Verschoor, J. Chem. Soc., Dalton
Trans., (1984) 1349-1356.
[39] C. Pettinari, F. Marchetti, R. Pettinari, D. Martini, A. Drozdov, S. Troyanov, Inorg. Chim.
Acta, 325 (2001) 103-114.
[40] S. Öztaş, E. Şahin, N. Ancın, S. Ide, M. Tüzün, J. Mol. Struct., 705 (2004) 107-112.
[41] B. Cordero, V. Gómez, A.E. Platero-Prats, M. Revés, J. Echeverría, E. Cremades, F.
Barragán, S. Alvarez, Dalton Trans., (2008) 2832-2838.
[42] S. Batsanov, Inorg. materials, 37 (2001) 871-885.
19

ACCEPTED MANUSCRIPT
[43] T. Sedaghat, M. Naseh, G. Bruno, H.A. Rudbari, H. Motamedi, J. Coord. Chem., 65 (2012)
1712-1723.
[44] B. Yearwood, S. Parkin, D.A. Atwood, Inorg. chim. Acta, 333 (2002) 124-131.
[45] D.K. Dey, S.P. Dey, N.K. Karan, A. Datta, A. Lycka, G.M. Rosair, J. Organomet. Chem.,
694 (2009) 2434-2441.
[46] T.P. Lockhart, W.F. Manders, Inorg. Chem., 25 (1986) 892-895.
[47] R. Palchaudhuri, P.J. Hergenrother, Curr. Opin. Biotech., 18 (2007) 497-503.
[48] J. Otera, Journal of Organometallic Chemistry, 221 (1981) 57-61.
[49] D. Kovala-Demertzi, P. Tauridou, U. Russo, M. Gielen, Inorg. Chim. Acta, 239 (1995) 177-
183.
[50] J. Otera, A. Kusaba, T. Hinoishi, Y. Kawasaki, J. Organomet. Chem., 228 (1982) 223-228.
[51] M.S. Refat, I.M. El-Deen, Z.M. Anwer, S. El-Ghol, J. Mol. Struct., 920 (2009) 149-162.
[52] B. Tweedy, Phytopathology, 55 (1964) 910-914.
[53] Y. Anjaneyulu, R.P. Rao, Synth.React.Inorg.Met.-Org. Chem., 16 (1986) 257-272.
[54] T. Sedaghat, L. Tahmasbi, H. Motamedi, R. Reyes-Martinez, D. Morales-Morales, J. Coord.
Chem., 66 (2013) 712-724.
[55] M. Khandani, T. Sedaghat, N. Erfani, M.R. Haghshenas, H.R. Khavasi, J. Mol. Struct., 1037
(2013) 136-143.
[56] R.V. Singh, P. Chaudhary, S. Chauhan, M. Swami, Spectrochim. Acta, Part A, 72 (2009)
260-268.
[57] B. Ruan, Y. Tian, R. Hu, H. Zhou, J. Wu, J. Yang, H. Zhu, Inorg. Chim. Acta, 365 (2011)
473-479.
20

ACCEPTED MANUSCRIPT
[58] M. Affan, M. Salam, F.B. Ahmad, F. White, H.M. Ali, Inorg. Chim. Acta, 387 (2012) 219-
225.
[59] F. Shaheen, S. Ali, A. Meetsma, Polyhedron, 31 (2012) 697-703.
[60] T. Sedaghat, Y. Ebrahimi, L. Carlucci, D.M. Proserpio, V. Nobakht, H. Motamedi, M.R.
Dayer, J. Organomet. Chem., 794 (2015) 223-230.
[61] S. Shujah, N. Muhammad, S. Ali, N. Khalid, M.N. Tahir, J. Organomet. Chem., 696 (2011)
2772-2781.
[62] R. Juan-Luis, F. Alian, Pseudomonas, Virulence and gene regulation, Springer, 2007.
[63] D.M. Livermore, Clin. Infect. Dis., 34 (2002) 634-640.
[64] T. Sedaghat, M. Yousefi, G. Bruno, H. Amiri Rudbari, H. Motamedi, V. Nobakht,
Polyhedron, 79 (2014) 88-96.
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Table 1 Crystallographic and structure refinement data for 1 and 2
2
Identification code
Empirical formula
Formula weight
Temperature/K
Crystal system
Space group
a/Å
1
C33H32N4O4Sn2
C53H40N4O4Sn2
786.01
1034.27
100(2)
100(2)
monoclinic
P21/c
triclinic
P-1
8.5659(3)
25.8115(8)
14.1311(4)
90.00
9.61550(12)
b/Å
14.91495(19)
c/Å
18.6982(2)
α/°
104.6543(11)
β/°
96.235(3)
90.00
91.3668(10)
γ/°
101.6051(10)
Volume/Å3
3105.88(17)
4
2533.41(5)
Z
2
ρcalcg/cm3
µ/mm-1
1.681
1.356
1.652
1.031
F(000)
1560.0
1036.0
Crystal size/mm
Radiation
0.28 × 0.22 × 0.06
MoKα (λ = 0.71073)
0.52 × 0.09 × 0.07
MoKα (λ = 0.71073)
3.16 to 52.74
2Θ range for data collection/° 3.3 to 56.56
Index ranges
-11 ≤ h ≤ 11, -34 ≤ k ≤ 34, -18 ≤ l ≤ 18
-14 ≤ h ≤ 14, -22 ≤ k ≤ 22, -28 ≤ l ≤ 28
162028
Reflections collected
Independent reflections
Data/restraints/parameters
Goodness-of-fit on F2
Final R indexes [I>=2σ (I)]
Final R indexes [all data]
39128
7718 [Rint = 0.0380, Rsigma = 0.0293]
7718/0/392
10337 [Rint = 0.0403, Rsigma = 0.0212]
10337/0/568
1.063
1.070
R1 = 0.0329, wR2 = 0.0726
R1 = 0.0426, wR2 = 0.0781
R1 = 0.0271, wR2 = 0.0724
R1 = 0.0302, wR2 = 0.0747
1.25/-0.43
Largest diff. peak/hole / e Å-3 1.39/-0.64

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Table 2. Bond lengths [Å] and angles [°] for complex 1
2.151(2)
2.092(2)
2.110(3)
2.108(4)
2.185(2)
2.149(2)
2.085(2)
2.117(3)
2.095(3)
2.186(3)
1.297(4)
1.308(4)
1.395(3)
1.302(4)
1.316(4)
1.302(4)
1.308(4)
1.396(3)
1.305(4)
1.324(4)
Sn1−O1
Sn1−O2
Sn1−C15
Sn1−C16
Sn1−N2
Sn2−O3
Sn2−O4
Sn2-C32
C1−O1
C1−N1
N1−N2
N2−C2
C4−O2
C18−O3
C18−N3
N3−N4
N4−C19
C21−O4
Sn2−C33
Sn2−N4
154.97(9)
93.78(11)
92.18(12)
91.59(12)
101.22(13)
72.87(9)
134.84(13)
82.98(9)
117.66(11)
106.87(11)
154.85(8)
94.67(11)
95.65(12)
97.53(12)
93.16(12)
72.31(9)
130.14(13)
82.55(9)
117.04(12)
112.58(12)
O1−Sn1-O2
O3−Sn2−O4
O3−Sn2−C32
O3−Sn2−C33
O4−Sn2−C32
O4−Sn2−C33
O3−Sn2−N4
C32−Sn2−C33
O4−Sn2−N4
N4−Sn2−C32
N4−Sn2−C33
O1−Sn1−C15
O1−Sn1−C16
O2−Sn1−C15
O2−Sn1−C16
O1−Sn1−N2
C15−Sn1−C16
O2−Sn1−N2
N2−Sn1−C15
N2−Sn1−C16
-2.0(4)
10.9(5)
-4.2(5)
2.8(3)
-13.5(4)
-26.9(4)
-0.7(5)
9.9(3)
N1− C1−O1−Sn1
C3−C4−O2−Sn1
C3−C2−N2 −Sn1
C1−N1−N2−Sn1
N3 −C18−O3−Sn2
C20−C21−O4−Sn2
C20−C19−N4−Sn2
C18−N3−N4−Sn2

ACCEPTED MANUSCRIPT
Table 3. Bond lengths [A] and angles [°] for complex 2
Sn1-O1
Sn1-O2
Sn1-C15
Sn1-C21
Sn1-N2
Sn2-O3
Sn2-O4
Sn2-C48
Sn2-C42
Sn2-N4
2.1192(16)
2.0691(15)
2.114(2)
1.302(3)
1.309(3)
1.399(2)
1.296(3)
1.332(3)
1.299(3
1.304(3)
1.399(3)
1.296(3)
1.319(3)
C1−O1
C1−N1
N1−N2
N2−C2
C4−O2
C28−O3
C28−N3
N3−N4
N4−C29
C31−O4
2.114(2)
2.1673(18)
2.1144(17)
2.1144(17)
2.118(2)
2.112(3)
2.1594(19)
O1-Sn1-O2
O1-Sn1-C15
O1-Sn1-C21
O2-Sn1-C15
O2-Sn1-C21
O1-Sn1-N2
C15-Sn1-C21
O2-Sn1-N2
N2-Sn1-C15
N2-Sn1-C21
154.89(6)
93.30(8)
105.54(8)
92.40(8)
100.51(8)
73.16(6)
124.75(8)
84.34(6)
129.22(7)
105.54(8)
O3-Sn2-O4
O3-Sn2-C42
O3-Sn2-C48
O4-Sn2-C42
O4-Sn2-C48
O3-Sn2-N4
C42-Sn2-C48
O4-Sn2-N4
N4-Sn2-C42
N4-Sn2-C48
157.17(7)
96.24(10)
94.58(9)
96.62(10)
94.17(9)
73.40(7)
122.85(9)
84.41(7)
110.94(9)
125.92(8)
-8.2(3)
17.6(3)
-8.3(3)
4.3(2)
7.3(3)
12.7(3)
1.1(3)
9.9(3)
N1− C1−O1−Sn1
C3−C4−O2−Sn1
C3−C2−N2 −Sn1
C1−N1−N2−Sn1
N3 −C28−O3−Sn2
C30−C31−O4−Sn2
C30−C29−N4−Sn2
C28−N3−N4−Sn2

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Table 4 Antibacterial activity data of ligands and organotin(IV) complexes
Conc.
(mg/disc)
0.1
0.2
0.4
0.8
0.1
0.2
0.4
0.8
0.1
0.2
0.4
0.8
0.1
0.2
0.4
0.8
0.1
0.2
0.4
0.8
0.1
0.2
0.4
0.8
30
Inhibition zone (mm)
Compound
H4La
E. Coli
n.a.
n.a.
n.a.
n.a.
n.a.
n.a.
n.a.
n.a.
20
21
21
23
11
11
12
14
n.a.
11
P. aeruginosa
S. aureus B. subtilis
n.a.
n.a.
n.a.
n.a.
n.a.
n.a.
n.a.
n.a.
19
n.a.
n.a.
n.a.
n.a.
n.a.
n.a.
n.a.
n.a.
19
n.a.
n.a.
n.a.
n.a.
n.a.
n.a.
n.a.
n.a.
20
20
20
21
10
13
13
19
n.a.
8
H4Lb
Sn2Me2La (1)
SnPh4La (2)
SnMe2Lb (3)
SnPh4Lb (4)
19
19
20
19
21
22
21
17
22
17
22
18
25
25
9
13
9
14
11
15
11
16
9
11
17
12
12
12
13
16
24
22
13
23
21
n.a.
n.a.
n.a.
n.a.
14
16
12
25
20
15
15
16
16
20
18
21
19
Vancomycin
Streptomycin
Penicilin
Nalidixic acid
Gentamicin
n.a.
n.a.
n.a.
n.a.
20
17
12
26
12
10
10
30
10
16
n.a. = no activity

ACCEPTED MANUSCRIPT
Figure 2. The asymmetric part of the unit cell of 1 and 2 with atom labeling scheme.
Displacement ellipsoids were drawn at the 50% probability level. Hydrogen atoms were omitted
for clarity.

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Figure 3 The arrangement of molecules in the crystal of 1, where: (a) infinite chain of molecules
involved in the weak C–H···N hydrogen bonds, running along the b-direction; (b) a general view
of the supramolecular framework of molecules along the c-direction. The C–H···N hydrogen
bonds are showed as dashed lines, while the weak C–H···π contacts by dotted lines. The H-
atoms not participating in the intermolecular interactions were omitted for clarity.

ACCEPTED MANUSCRIPT
Figure 4. The arrangement of molecules in the crystal of 2 viewed along the a-direction. The
weak C–H···π contacts are represented by dotted lines. The H-atoms not participating in the
above-mentioned interactions were omitted for clarity.

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H
H
N
a
R
N
R
N
N
O
O
b
HO
OH
c
1
2
O
1
H4La:
H4Lb:
R =
3
R =
2
3
R
N
N
R
N
N
O
O
Sn
R'
Sn
O
O
R'
R'
1: R = C6H5, R' = CH3
2: R = C6H5, R' = C6H5
3: R = C4H3O, R' = CH3
4: R = C4H3O, R' = C6H5
R'
Figure 1 Structure of ligands and complexes with numbering for 1H NMR assignments