Synthesis, structural characterization, in vitro cytotoxicities, DNA-binding and BSA interaction of diorganotin (IV) complexes derived from hydrazone Schiff base

Article abstract of DOI:10.1016/j.jorganchem.2013.12.037

Five diorganotin(IV) complexes of benzoylformic acid 3-hydroxy-2-naphthoyl hydrazone, [R₂SnLY]₂ (L = 3-HO-C₁₀H ₆CON₂C(C₆H₅)CO₂) with Y = H₂O, R = CH₃ (1), Y = EtOH, R = Ph (3), Y = EtOH, R = o-Cl-Bz (4), Y = EtOH, R = o-F-Bz (5), and [R₂SnLY] with Y = EtOH, R = n-Bu (2) were prepared, which were structurally characterized by X-ray crystallography, elemental, IR and NMR (¹H and ¹³C) spectroscopy. Structural analysis reveal that the ligand presents as tridentate ligand with ONO donors and coordinates to the tin center in an enolic form. Compound 2 is a monomer while the other compounds are weakly bridged dimers with weak Sn?O interactions. In vitro cytotoxicities of compounds 1, 3 and the ligand were determined to explore their potential anticancer activities. DNA-binding properties of 1 and 3 with calf thymus DNA (ct-DNA) were investigated by fluorescence quenching method with ethidium bromide (abbr. EB)-DNA system. Furthermore, the protein fluorescence quenching studies reveal that there are strong binding interactions between compounds 1, 3 and bovine serum albumins (BSA). Synchronous fluorescence spectra show that both the tryptophan and tyrosine residues in BSA are affected by the two compounds.

Full text of DOI:10.1016/j.jorganchem.2013.12.037

Accepted Manuscript
Synthesis, structural characterization, in vitro cytotoxicities, DNA-binding and BSA
interaction of diorganotin (IV) complexes derived from hydrazone Schiff base
Fei Wang, Handong Yin, Jichun Cui, Yanwei Zhang, Honglin Geng, Min Hong
PII:
S0022-328X(13)00918-2
10.1016/j.jorganchem.2013.12.037
JOM 18423
DOI:
Reference:
To appear in: Journal of Organometallic Chemistry
Received Date: 30 August 2013
Revised Date: 20 December 2013
Accepted Date: 21 December 2013
Please cite this article as: F. Wang, H. Yin, J. Cui, Y. Zhang, H. Geng, M. Hong, Synthesis, structural
characterization, in vitro cytotoxicities, DNA-binding and BSA interaction of diorganotin (IV) complexes
derived from hydrazone Schiff base, Journal of Organometallic Chemistry (2014), doi: 10.1016/
j.jorganchem.2013.12.037.
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Graphical Abstract-Synopsis
Synthesis, structural characterization, in vitro cytotoxicities,
DNA-binding and BSA interaction of diorganotin (IV) complexes
derived from hydrazone Schiff base
Fei Wang, Handong Yin , Jichun Cui, Yanwei Zhang, Honglin Geng, Min Hong*
Shandong Provincial Key Laboratory of Chemical Energy Storage and Novel Cell Technology, School of
Chemistry and Chemical Engineering, Liaocheng University, Liaocheng 252059, China
Synopsis
Five diorganotin(IV) complexes containing hydrazone Schiff base were synthesized and
characterized. The in vitro cytotoxicities of two compounds as well as the ligand were investigated
against several human cancer cell lines. Additionally, bioactivity mechanism such as
DNA-binding and BSA-binding were explored via fluorescence spectra.
Corresponding author. Tel.:/Fax: +866358239121.
E-mail address: handongyin@163.com (H.D. Yin); hongminlcu@163.com (M. Hong).

ACCEPTED MANUSCRIPT
Graphical Abstract-Pictogram
Synthesis, structural characterization, in vitro cytotoxicities,
DNA-binding and BSA interaction of diorganotin (IV) complexes
derived from hydrazone Schiff base
Fei Wang, Handong Yin , Jichun Cui, Yanwei Zhang, Honglin Geng, Min Hong*
Shandong Provincial Key Laboratory of Chemical Energy Storage and Novel Cell Technology, School of
Chemistry and Chemical Engineering, Liaocheng University, Liaocheng 252059, China
Pictogram
Corresponding author. Tel.:/Fax: +866358239121.
E-mail address: handongyin@163.com (H.D. Yin); hongminlcu@163.com (M. Hong).

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Highlight
1. Five diorganotin(IV) complexes were synthesized and characterized.
2. The cytotoxicities of two compounds and the ligand were tested by the SRB and MTT test.
3. Biological investigations like DNA binding and protein binding were carried out using two
compounds by fluorescent spectra.

ACCEPTED MANUSCRIPT
Synthesis, structural characterization, in vitro cytotoxicities,
DNA-binding and BSA interaction of diorganotin (IV) complexes derived
from hydrazone Schiff base
Fei Wang, Handong Yin , Jichun Cui, Yanwei Zhang, Honglin Geng, Min Hong*
Shandong Provincial Key Laboratory of Chemical Energy Storage and Novel Cell Technology, School of Chemistry and
Chemical Engineering, Liaocheng University, Liaocheng 252059, China
Abstract
Five diorganotin(IV) complexes of benzoylformic acid 3-hydroxy-2-naphthoyl hydrazone,
[R2SnLY]2 (L = 3-HO-C10H6CON2C(C6H5)CO2) with Y = H2O, R = CH3 (1), Y = EtOH, R = Ph (3), Y =
EtOH, R = o-Cl-Bz (4), Y = EtOH, R = o-F-Bz (5), and [R2SnLY] with Y = EtOH, R = n-Bu (2) were
prepared, which were structurally characterized by X-ray crystallography, elemental, IR and NMR (1H
and 13C ) spectroscopy. Structural analysis reveal that the ligand presents as tridentate ligand with ONO
donors and coordinates to the tin center in an enolic form. Compound 2 is a monomer while the other
compounds are weakly-bridged dimers with weak Sn…O interactions. In vitro cytotoxicities of
compounds 1, 3 and the ligand were determined to explore their potential anticancer activities. DNA
binding properties of 1 and 3 with calf thymus DNA (ct-DNA) were investigated by fluorescence
quenching method with ethidium bromide (abbr. EB)-DNA system. Furthermore, the protein
fluorescence quenching studies reveal that there are strong binding interactions between compounds 1ꢀ
3 and bovine serum albumins (BSA). Synchronous fluorescence spectra shows both the tryptophan and
tyrosine residues in BSA are affected by the two compounds.
Keywords: Diorganotin(IV); Hydrazone; Crystal structure; Cytotoxicity activity; DNA-binding;
BSA-binding.
1. Introduction
The quest for alternative drugs to the well-known cisplatin and its derivatives, which are still used
in more than 50% of the treatment regimes for patients suffering from cancer, is highly needed [1,2].
Corresponding author. Tel.:/Fax: +866358239121.
E-mail address: handongyin@163.com (H.D. Yin); hongminlcu@163.com (M. Hong).
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These platinum compounds suffer from two main disadvantages: inefficient against platinum-resistant
tumors and severe side effects. Furthermore, as a consequence of its particular chemical structure,
cisplatin in particular offers little possibility for rational improvements to increase its tumor specificity
and thereby reduce undesired side effects [3]. Hence, attempts are being made to replace cisplatin with
suitable alternatives and numerous metal-based complexes have been synthesized and tested for their
anticancer activities. Among them, organotin complexes show promising antitumor activities against a
wide panel of tumors or tumor cell lines and many organotin complexes were screened against a variety
of cell lines and were found to be active both in vitro and in vivo [4-8]. A. Alama and his coworkers
investigated the cytotoxicities of tri-n-butyltin(IV) lupinylsulfide hydrogen fumarate in vitro and
antitumor activity in vivo [9]. X.M. Shang prepared a serial of organotin carboxylates and reported their
relationship between their properties (electrochemical behavior, structural rearrangements) and
antitumor activities [10]. Another two di-n-butyltin(IV) derivatives synthesized by X.M. Shang were
reported to displayed an arrest in the G0/G1 phase and a decrease of S phase of the cell cycle in KB
cells at low concentrations of the two complexes [11]. Recent studies demonstrated that some tri- and
diorganotin(IV) complexes were selectively mediated through the induction of apoptosis [12].
Hydrazone attracted special attention from researchers due to their well-known chelating capability
and structural flexibility that can provide rigidity to the skeletal framework of the prepared metal
complexes [13-15]. Based on the chelating ability, certain hydrazones were synthesized and applied in
the treatment of iron over-loaded diseases, such as β-thalas semia major [16]. Fascinating chemical
behaviors and biological essentialities such as antibacterial, antiproliferative, antimalarial and antitumor
were also favored by researchers in the area of medicine and drugs. One ortho-hydroxy N-acyl
hydrazone was reported to enhance the enzymatic activity of procaspase-3 in vitro and induce apoptosis
in cancer cells [17]. A number of hydrazones such as 311 and PIH have been shown to have
anti-proliferative activities [18, 19]. J.Q. Tong synthesized one hydrazone and studied the BSA binding
abilities of the hydrazone employing several different techniques [20]. Meanwhile, large numbers of
hydrazone-containing metal chelates were also synthesized. M. Alagesan and co-workers reported the
synthesis, crystal structure and biological properties (DNA-bind, BSA-bind and in vitro cytotoxicities)
of two copper(II) hydrazone complexes [21]. D.S. Raja synthesized
a
water soluble
cobalt(II)-hydrazone polymer and investigated the DNA binding, protein interaction, radical scavenging
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as well as anticancer activity of the complex [22]. E. Ramachandran and co-workers reported five
thiosemicarbazone ligands and their corresponding palladium(II) complexes [23]. Besides, hydrazone
Schiff bases were widely used as fluorescent probes for their fluorescence [24].
Though the exact antitumor mechanism presented by the mental-based anticancer agents remains
unknown, lots of studies show that many anticancer agents could bind or cleave DNA. DNA is viewed
as one of the main molecular targets in the design of anticancer compounds [25]. Organotin compounds
are important species among these anticancer drugs which could interact with DNA. Our study found
organotin complexes containing Schiff base could interact with CT-DNA through intercalation with
different extent [26]. Besides, the interaction between anticancer agents and serum albumins which
involved in the transport of metal ions and metal complexes through the blood stream are also widely
investigated [27,28]. Because the nature and magnitude of drug–albumin interactions could influence
the pharmacokinetics of drugs significantly. Further, it has been demonstrated that free radicals can
damage proteins, lipids, and DNA of bio-tissues, leading to increased rates of cancer and fortunately
antioxidants can prevent this damage due to their free radical scavenging activity [29]. Thus, radical
scavenging is viewed as another property to be measured on anticancer agents. Despite the wealth of
information available on these topics, limited reports are available on the related organotin complexes.
Hence, in view of the great potential of hydrazone in drug design and the remarkable anticancer
performance of organotin(IV) species, the synthesis, structural characterization, in vitro cytotoxicity,
DNA and BSA interaction investigations of a series of organotin complexes with hydrazone are
reported here and demonstrate a huge potential of this type of organometallics in medicinal chemistry.
2. Results and Discussion
2.1. Syntheses of diorganotin(IV) compounds
Complexes 1–5 were obtained by the reaction of the ligand/R2SnCl2/EtONa in a 1:1:2 molar ratio in
ethanol/toluene (1:1) under refluxing. The synthetic procedures are shown in Scheme 1.
2.2. Spectroscopic data
Comparing the IR spectra of the complexes with the free ligand, a remarkable difference is the
complete disappearance of C=O stretching frequencies (1649 cm-1), which confirms that the ligand
coordinates with the tin in the enolic form. The frequency separation between asymmetric stretching
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vibration and symmetric stretching vibrations of COO lies between 230 and 282 cm-1 for compounds
1-5, indicating the monodentate coordination mode of carboxylate group [29]. This is in accordance
with the X-ray structure analysis. Strong bands at region 650-600 cm-1 in compounds 1, 3, 4 and 5 are
assigned to a bridge Sn-O-Sn [30]. New bands at 470–481 cm-1 are characteristic of Sn–N absorption,
respectively [31].
1
In the H NMR spectra of free ligand, single resonance for COOH group is observed at δ = 13.38
ppm. The absent of COOH group in the 1H NMR spectra of compounds 1-5 indicates the deprotonation
of COOH group. The values are consistent with those reported for other R2Sn(O2CR')2 systems [32,33].
1
Signal of -NH- could not be found in the H NMR spectra of compounds 1-5, suggesting the
coordination to the central tin atom in the enolic form. Signal resonance for naphthoic hydroxyl can be
observed at 10.83-12.33 ppm in all complexes which strongly suggests that the naphthoic hydroxyl
oxygen atom does not participate in coordination to the tin atom. Comparing with the ligand, the 13C
NMR values of COO, CONH shift to downfield about 8 ppm and 3 ppm due to the coordination of
COOH and -NH- groups, while there is only little downfield of C=N and C-OH groups. The shift is a
consequence of an electron density transfer from the ligand to the acceptor. The δ values of naphthoic
hydrogens and carbons are consistent with those reported values[34,35].
2.3. X-ray crystallography
2.3.1. X-ray crystallography of complexes 1, 3, 4 and 5.
The molecular structures of the compounds 1, 3, 4 and 5 are illustrated in Fig. 1, respectively.
Crystal data are listed in Table 1. Selected bond distances and angles are listed in Table 2. We take
complex 1 as an example to describe their structural characteristics.
In complex 1, the Sn atom exists in a distorted pentagonal–bipyramidal configuration, being
coordinated by three O atoms and one N atom from the ligand, one O atom from the water molecule and
two C atoms from trans alkyl groups. The axial C(20)-Sn(1)-C(21) angle is not 180º but 166.0(2)º,
which proves the distortion of the geometry. Atom O(1) of the carboxylate residue also binds more
weakly to the other Sn atom, Sni, generating an Sn2O2 four-membered ring [symmetry code: -x, -y+1,
-z+1]. The sum of the angles subtended at the Sn atom in the equatorial plane is typical for the ideal
value of 360.01º for complex 1 for Sn(1), so that the Sn(1), O(1), N(1), O(3), O1#1and O(5) atoms are
almost in the same plane. The distance of Sn(1)-O(1)#1 [2.661(3)Å] is longer than the sum of the
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covalent radii of Sn and O (2.56Å), but is signficantly shorter than the sum of the van der Waals radii of
tin and oxygen (3.68Å). Such Sn…O bond should be considered as weak bonding interaction. The
Sn(1)-O(5) bond length is 2.373(3)Å and is longer than those analogous complexes [29,36] which can
be attributed to the formation of intramolecular hydrogen bonds (O5-H5…O2#1). The distance of
Sn(1)-O(3) [2.216(3)Å] is shorter than the sum of the covalent radii of Sn and O (2.56Å), indicating
strong Sn…O interaction. The Sn(1)-N(1) distance [2.299(4) Å] is a little longer than the sum of the
covalent radii of Sn and N (2.15 Å). As described above, structure of compound 1 can be described as
weakly-bridged dimers with weak Sn…O interactions and the coordination geometries of tin atom can
also be described as trans-C2SnO4N pentagonal bipyramid with two alkyl groups occupying trans
positions. Undoubtedly, intramolecular and intermolecular hydrogen bonds observed in compound 1
contribute to the stability and compactness of the dimmer (Table 4).
The bond length of C(9)-O(3) [1.270(5)Å] lie between double (1.224Å) and single-bond (1.430Å)
lengths. Compared with the length of a C=N double bond (1.38Å) and a C-N single bond (1.470Å),
C(9)-N(2) [1.345(5)Å] bond as well as C(2)-N(1) [1.292(5)Å] should be classified as C=N double bonds.
N(1)-N(2) bonds [1.378(5)Å] fall within the normal range of N-N single-bond [37,38]. These data
indicate that a C=N-N=C conjugated system is introduced into the inner coordination sphere and the
ligand functions as a tridentate chelate with ONO donors. Additionally, the tridentate ligand forms two
five-membered chelate ring with the central Sn atom, which contribute to the stability of the crystals.
As for complexes 3, 4 and 5, the coordination environment is similar to complex 1. The axial angle
is 171.66(12)º, 161.85(18)º and 163.2(3)º for complexes 3, 4 and 5, respectively. Atom O1 of the
carboxylate residue binds more weakly to the other Sn atom, Sni, generating an Sn2O2 four-membered
ring [symmetry code: (3) -x+2, -y+1, -z; (4) -x, -y, -z+1; (5) -x+1, -y+1, -z] with the distance of
Sn1-O1#1[3: 2.581(2)Å; 4: 2.628(3)Å; 5: 2.638(4)Å]. The Sn(1)-O(3) bond lengths [2.182(2)Å for 3,
2.162(3) Å for 4 and 2.181(4) Å for 5] are shorter than the bond lengths observed in complex 1. As for
Sn(1)-N(1) bond length, complex 4 shows the shortest length with 2.244(3) Å, while complex 4 shows
the longest bond length of Sn(1)-O(5) [ 2.428(3) Å]. The Sn(1)-O(1) varies from 2.349(3) Å (complex 4)
to 2.393(4) Å (complex 5). Other bond lengths such as C(9)-O(3), C(9)-N(2), C(2)-N(1) and N(1)-N(2)
are similar to complex 1. Hydrogen bonds [O(4)-H(4)...N(2) and O(5)-H(5)...O(2)#1] can be observed in
complexes 3, 4 and 5.
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2.3.2. Crystal structure of complex 2
For compound 2, the molecular structure is best described as monomer due to the long distance of
Sn(1)-O(1)#1 [2.819(4)Å, #1: 1-x, 2-y, -z]. The Sn atom adopts a six-coordinate geometry, with the
equatorial positions occupied by three oxygen atoms [O(1), O(3), O(5)] and one nitrogen N(1) (Fig. 2).
The Schiff base coordinates to the Sn atom as a tridentate ligand via the azomethine N atom, the
hydroxyl O atom and the carbonyl O atom. The O atoms from the ligand coordinate to the Sn atom with
one short [Sn(1)-O(3) 2.175(4) Å] and one long Sn-O bond [Sn(1)-O(1) 2.304(4) Å]. Atoms O(1), O(3),
O(5) and N(1) are coplanar with angles subtended at the Sn atom in the equatorial plane is 360.02º. The
axial angle C(21)-Sn(1)-C(24) [162.5(4)º] deviates from the ideal value of 180º (Table 3). Thus the
coordination environment is a distorted octahedral geometry. The bond length of C(9)-O(3), C(9)-N(2)
as well as C(2)-N(1) are similar to the above complexes. Hydrogen bonds can also be observed in
compound 2 (Table 4).
2.4. In vitro cytotoxicities activity
The in vitro cytotoxicities of complexes 1, 3 and the free ligand were determined by SRB and
MTT-based assay to understand the possible relationship between the different tin(IV) moieties (bearing
dimethyl and diphenyl groups), the ligand and the cytotoxicities activity. Complexes were tested for
cytotoxicities activity on seven tumor cell lines: human lung cancer cell line (A549), human
hepatocellular carcinoma cell line (SMMC-7721), murine leukemia cell line (P388), human colon
carcinoma (WiDr), human colon cell line (HCT-116) and non-cancer cell human umbilical vein
endothelial cells (HUVEC). The results are expressed as IC50 (in ꢀg/ml) and the corresponding IC50
values are listed in Table 5. Possible structure-activity relationships could be recognized as follows:
(1) Diphenyl (IV) compound 3 was more potent than dimethyltin compound 1 in inhibiting the
growth of most of the cell lines tested here. Complex 3 is the most efficient antitumor agent for
SMMC-7721, A549, P388, HCT-116 and HUVEC cells while complex 1 exhibits the highest activities
against WiDr cells. Among them, the most outstanding result is obtained from the activity of complex 3
in HCT-116 tumor cells (4.00 ꢀg/ml). Besides, the ligand exhibit almost non-inhibition for cellular
proliferation. As far as one complex concerned, every organotin complexes tested here showed some
degree of selectivity toward the seven tumor lines. Take compound 3 for example, about 4-fold
improvement of the antitumor potency in HCT-116 cells compared to Caco-2 cells, 2-fold improvement
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in SMMC-7721 cells than A549 cells.
(2) Every tumor cell line reported here exhibits different resistance to different organotin
compounds. A549 cells exhibit somewhat low sensitivity to both complexes. WiDr cells show similar
moderate resistance and SMMC-7721, HCT-116 and P388 cells exhibit high sensitivity. Compared to
compound 3, compound 1 is less toxic toward non-cancer cell (HUVEC).
(3) Analyses of crystal structures of 1 and 3 demonstrate that they have similar coordination
geometry. Changes of the organic group result in different inhibition for the same cancer cell. In our
experiments, complex 3 shows the antitumor effect of 4.24, 3.38 and 2.58 times more potent than
complex 1 in HCT-116, SMMC-7721 and P388 cell lines, respectively. To some extent, our results are
in accordance with the previous studies [8,9,39].
2.5. Fluorescence spectra
The interaction of complexes 1 and 3 with DNA has been evaluated by the ethidium bromide (abbr.
EB)-DNA system with limited EB bound to excess of DNA, which can be used to distinguish
intercalating and non-intercalative ligands [40]. Competitive binding of other intercalators leads to a
loss of fluorescence because of depletion of the EB-DNA complex [40,41]. As shown in Fig. 3, the
fluorescent intensity of EB in the bound form is remarkably quenched upon adding organotin complexes
and a dose-response phenomenon is observed. However, complex 1 causes the lower fluorescence value
to decrease, indicating lower DNA-binding ability. According to the classical Stern–Volmer equation:
I/I0 = 1 + Ksqr
where I0 and I represent fluorescence intensities in the absence and presence of the samples,
respectively; r corresponds to the concentration ratio of the sample to DNA. Ksq, the linear
Stern–Volmer constant, can be obtained from the slope of I0/I versus r linear plot. From the insets in Fig.
3, the values of Ksq for 1 and 3 can be calculated as 0.2372 and 3.626, respectively, indicating stronger
interaction between complex 3 and DNA. The quenching plot of 1 is in good agreement with the linear
Stern–Volmer equation and can be defined as intercalative mode with DNA. Compared with 1, the exact
interaction between DNA and 3 can be more complicated since the linear relationship is not well
presented and may exist other interactions between 3 and DNA. To some extent, this result can partly
explain the cytotoxicities of the two complexes for the same cancer cell. Organotin complex 3 with
stronger DNA-binding ability exhibited higher cytotoxic activity in SMMC-7721, A549, P388 and
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HCT-116 cells possibly due to their ability to interact with DNA.
2.6. Protein binding studies
2.6.1.Fluorescence Quenching Studies.
The interaction of diorganotin(IV) complexes (1 and 3) with BSA is monitored by studying the
quenching of the fluorescence of BSA with increasing concentration of organotin(IV) complexes.
Tryptophan residue makes major contribution to the intrinsic fluorescence of protein. The emission is
sensitive to the changes in the local environment of the tryptophan and can be attenuated by binding of a
small molecule at or near this residue. As can be seen from Fig. 4 and Fig. S2(A), the fluorescence
intensities of the protein are decreased regularly with increasing concentration of the probe compounds,
indicating the binding of complexes to the protein. Addition of the compounds to BSA resulted in a
significant decrease in the fluorescence intensity of BSA at 344 nm, up to 47.78 and 46.79 % of the
initial fluorescence intensity of BSA accompanied by a hypsochromic shift of 4 and 2 nm for complexes
1 and 3, respectively. Commonly, fluorescence quenching can be described by the following
Stern−Volmer equation :
I0/I = 1 + Ksv[Q] = 1 + kqτ0[Q].
where I0 and I are the steady-state fluorescence intensities in the absence and presence of quencher,
respectively, Ksv is the Stern−Volmer quenching constant, [Q] is the total concentration of quencher, kq
is the bimolecular quenching constant, and τ0 is the average lifetime of protein in the absence of
quencher, and its value is 10−8 s [43]. Ksv can be obtained by a slope from the plot of F0/F vs. [Q] (Fig.
5A and Table 6). All plots represent a good linear relationship, indicating a single quenching mechanism,
either static (the formation of a complex between quencher and fluorophore) or dynamic (a collisional
process) [44]. The Kq values (∼1013 M−1 s−1) of the complexes 1 and 3 are higher than the maximum
scatter collision-quenching constant of diverse kinds of quenchers for biopolymers fluorescence (2
×1010 M−1 s−1) indicating the existence of static quenching mechanism [45]. Based on the plot of log
(I0-I)/I versus log [Q] (Fig. 5B), the number of binding sites [(n = 1.237 (complex 1), 1.162 (complex 3)]
and binding constant [Kbin = 1.72×106 M-1(1), 6.82×105 M-1 (3)] can been obtained. The values of Kq
and Kbin indicate strong interaction between the BSA protein and the two organotin complexes,
suggesting they can easily be stored in protein.
2.6.2. Characteristics of the synchronous fluorescence spectra
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Structural changes of BSA particularly the vicinity of the fluorophore groups induced by compounds
can be reflected by the synchronous fluorescence spectra of BSA. The synchronization fluorescence
spectrum has been reported to be an effective approach to distinguish the tryptophan (Trp) (ꢁλ = 60 nm)
and tyrosine (Tyr) (ꢁλ =15 nm ) residues in protein [46]. The effect of organotin complexes on BSA
synchronous fluorescence spectroscopy with ꢁλ = 15 nm and Δλ = 60 nm are shown in Fig. 4 and Fig.
S2, respectively. According to the above result, two diorganotin complexes demonstrate similar BSA
binding ability and now they show similar synchronous spectroscopy. Take complex 3 for example, in
the synchronous fluorescence spectra of BSA at ꢁλ = 15 nm, additions of the complex 3 result in a
decrease of BSA at 282 nm, up to 72.9% of the initial fluorescence intensity with no shift in their
emission wavelength maxima. On the other hand, in the case of ꢁλ = 60, a decrease of up to 52.6 % at
282 nm of the initial fluorescence intensity of BSA accompanied with a blue shift of 2 nm could be
observed. The above results suggest that the fluorescence intensity of both tryptophan and tyrosine
residues of BSA are affected but to the larger extent in the case of former by the complexes.
3. Conclusions
A series of diorganotin(IV) compounds, bearing benzoylformic acid 3-hydroxy-2-naphthoyl
hydrazone, are isolated and structurally characterized. For 1, 3, 4 and 5, all complexes present as
centrosymmetric dimeric structures with weak Sn…O interactions while complex 2 presents as a
monomer. For 1 and 3, change of the organo group leads to different inhibitions for the same
tumorigenic cells. Complex 3 is highly active against two tumor cell lines (SMMC-7721 and HCT-116),
whereas complex 1 shows the lowest IC50 on WiDr cells. Fluorescence spectra reveal that complex 3
exhibits stronger DNA-binding ability than complex 1. BSA-binding properties investigations reveal
that complexes 1 and 3 exhibit similar strong binding ability toward BSA, suggesting these compounds
can easily be stored in protein. Synchronous fluorescence spectra show both the tryptophan and tyrosine
residues in BSA are affected by the two compounds.
4. Experimental details
4.1. Materials and measurements
Dimethyltin dichloride, di-n-butyltin dichloride and diphenyltin dichloride were commercially
available and they were used without further purification. Di-o-chlorobenzyltin chloride and
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di-o-fluorobenzyltin chloride were prepared by the methods reported in the literature [47]. Analytical
grade solvents used in this work were undried. Elemental analyses were performed on a PE-2400-II
elemental analyzer. IR spectra were recorded on a Nicolet-5700 spectrophotometer using KBr discs. 1H,
and 13C NMR spectra were recorded on a Varian Mercury Plus-400 NMR spectrometer. Chemical shifts
were given in ppm relative to Me4Si(1H, 13C) in CDCl3 or DMSO solvent. UV-vis was performed on a
UV-2550 ultraviolet spectrophotometer. Fluorescence spectra were recorded on a F-7000 FL
spectrophotometer.
4.2. Determination of crystal structures
Diffraction data for 1-5 were obtained on a Bruker Smart 1000 CCD diffractometer (graphite mo
nochromated Mo-Ka radiation, λ= 0.71073 Å). All data were corrected using SADABS and the final
refinement was performed by full-matrix least-squares with anisotropic thermal parameters for
non-hydrogen atoms on F2 using SHELX-97. The hydrogen atoms were added theoretically, riding on
the concerned atoms and refined with fixed thermal factors. The carbons (C32) of an ethanol in 3 and
the atoms (C28, C29, C30, C31, C32, C33, C34, C35, F1, F2) of one di-o-fluorobenzyl group in 5 were
disordered. The site occupation factors of these disordered atoms were adjusted (0.5 for each atom) to
give reasonable thermal parameters.
4.3. Preparation of Schiff base ligand
20 mL ethanol solution of 2-picolinic acid (10 mmol, 1.23 g) was added dropwise to an ethanol
solution (40 mL) containing 3-hydroxy-2-naphthoic acid hydrazide (10 mmol, 2.02 g). The mixture was
heated under reflux with stirring for 3 h. The crude product was precipitated when the solution cooled
down. Then the product was filtered and washed with ethanol for three times. Yield: 88%, M.p.
199~200 °C. Anal. Calc. for C19H14N2O4 (334.33): C: 68.26; H: 4.22; N: 8.38 %ꢁfound C: 68.35; H:
1
4.25; N: 8.34 %. IR (KBr, cm–1): 3413 (s, NH); 3252 (s, COOH); 1649 (s, C=O); 1596 (s, C=N). H
NMR (d-DMSO, ppm): 13.37 (s, 1H, COOH), 11.74 (s, 1H, OH), 11.45 (s, 1H, NH), 8.68(s, 1H, H1)ꢀ
7.95(d, 1H, J=4 Hz, H8), 7.77(d, 2H, J=4 Hz, H12), 7.72(d, 1H, J=8Hz, H5), 7.52-7.44(m, 3H, H13, H14 ),
7.36-7.33 (m, 2H, H6, H7). 7.20(s, 1H, H4),13C NMR (d-DMSO, ppm): 164.4(COOH), 162.6(C=N),
153.3(C3), 144.3(CONH), 136.8(C10), 135.0(C11), 134.0, 130.2, 129.8, 129.2, 129.0, 128.5, 127.9, 126.3,
124.6(C7), 120.9(C2), 111.3(C4).
4.4. Syntheses of complexes 1–5
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The complexes were prepared under nitrogen atmosphere. Benzoylformic acid
3-hydroxy-2-naphthoyl hydrazone (0.334g, 1.0 mmol), EtONa (0.136g, 2.0 mmol) were added to a
stirred solution of 30 mL ethanol/toluene (1:1) in a round bottomed flask and stirred for 0.5 h.
Dialkylltin dichloride (1.0 mmol) was then added to the reactor. The reaction mixture was stirred and
heated at reflux for 8 h and then filtrated. The filtrate was evaporated in vacuum. The obtained solid was
recrystallized from dichloromethane/ethanol (1:1). Yellow block crystals were slowly formed at room
temperature.
4.4.1. {Me2Sn[3-HO-C10H6CON2C(C6H5)CO2](H2O)}2 (1)
Yield: 63%, M.p.: >300 °C. Anal. Calc. for C42H40N4O10Sn2: C, 50.54; H, 4.04; N, 5.61%. Found:
C,50.78; H, 4.08; N,5.72%. IR (KBr, cm–1): 3432 (m, H2O); 1641 (s, υasCOO); 1388 (s, υsCOO); 1576
(m, C=N-N=C); 631 (s, Sn-O-Sn); 525 (w, Sn-C); 475 (m, Sn-N). 1H NMR (d-DMSO, δ ppm): 12.33 (s,
1H, Ar-OH), 8.53(s, 1H, H1), 7.84(d, 1H, J=8 Hz, H8), 7.73(d, 2H, J=8 Hz, H12),7.63(d, 1H, J=8 Hz, H5),
7.53-7.50(m, 3H, H13, H14), 7.42(t, 1H, J=8 Hz, H6), 7.26(t, 1H, J=8 Hz, H7), 7.10(s, 1H, H4), 3.38 (s,
2H, H2O), 0.90 (s, 6H, Sn-CH3). 13C NMR (d-DMSO , ppm): 172.11 (COO), 162.3 (C=N), 154.6 (C3),
147.4 (CONH), 135.2 (C10), 129.6 (C11), 129.4, 128.5 128.4, 127.4 126.5, 126.2, 125.3, 124.2 (aromatic
carbons), 121.5 (C7), 117.8 (C2), 109.0 (C4), 10.1 (Sn–CH3).
4.4.2. n-Bu2Sn[3-HO-C10H6CON2C(C6H5)CO2]·(C2H5OH) (2)
Yield: 85 %, M.p.: 200-201ꢂ. Anal. Calc. for C29H36N2O5Sn: C, 56.98; H, 5.94; N, 4.58%; Found: C,
56.87; H, 5.58; N,4.32%. IR (KBr, cm–1): 1639 (s, υasCOO); 1390 (s, υsCOO); 1579 (m, C=N-N=C);
546 (m, Sn-O); 525 (w, Sn-C); 476 (m, Sn-N). 1H NMR (CDCl3, δ ppm): 11.37 (s, 1H, Ar-OH), 8.64(s,
1H, H1), 7.97-7.95(m, 2H), 7.84(d, 1H, J=8 Hz, H8), 7.67-7.62(m, 5H), 7.47(t, 1H, J=6 Hz, H6), 7.30(t,
1H, J=8 Hz, H7). 1.85-1.79 (m, 2H, Sn-C1H2), 1.70-1.64 (m, 2H, -C2H2-), 1.44-1.35 (m, 2H, -C3H2-),
0.90 (t, 3H, -C4H3, J= 6.0 Hz). 13C NMR (CDCl3, δ ppm): 176.1 (COO), 163.7 (C=N), 156.0 (C3), 151.5
(CONH)ꢀ137.9 (C10), 132.6 (C11), 132.3, 130.9, 129.3, 129.1ꢀ128.9, 128.6, 127.6, 126.5(aromatic
carbons), 123.9 (C7), 117.6 (C2), 111.9 (C4), 27.1(Sn-C1H2-), 26.6 (-C2H2-), 23.3 (-C3H2-), 13.6(-C4H3).
4.4.3. {Ph2Sn[3-HO-C10H6CON2C(C6H5)CO2] (C2H5OH)}2 (3)
Yield: 58%, M.p.: 254-255ꢂ. Anal. Calc. for C66H56N4O10Sn2: C, 60.86; H, 4.33; N, 4.30%;. Found: C,
60.89; H, 3.89; N,4.65%. IR (KBr, cm–1): 1637 (s, υasCOO); 1386 (s, υsCOO); 1573 (m, C=N-N=C);
1
630 (s, Sn-O-Sn); 522 (w, Sn-C); 475 (m, Sn-N). H NMR (CDCl3, δ ppm): 10.86 (s, 2H, Ar-OH),
11

ACCEPTED MANUSCRIPT
8.59(s, 1H, H1), 7.73-7.71(m, 3H)ꢀ7.68-7.63(m, 4H), 7.41(d, 1H, J=8 Hz), 7.32-7.21(m, 11H), 7.09(t,
1H, J=8Hz), 7.01-6.98(m, 2H), 3.41(q, 2H, -OCH2-, J=12 Hz), 1.59(s, 1H, R-OH), 1.25(t, 3H, J=6 Hz,
-OCH2-CH3). 13C NMR (CDCl3, δ ppm): 176.0 (COO), 162.4 (C=N), 155.9 (C3), 151.7 (CONH), 138.0
(C10), 136.4(C-Sn), 135.4, 132.6, 131.8, 131.1, 130.2, 129.8, 129.3, 128.5, 128.3, 127.5, 126.4 (aromatic
carbons), 124.0 (C7), 117.2 (C2), 112.0 (C4), 58.7(-OCH2-), 18.6 (-OCH2-CH3).
4.4.4. {(o-Cl-Bz)2Sn[3-HO-C10H6CON2C(C6H5)CO2]2(C2H5OH)}2 (4)
Yield: 72%, M.p.: 243-244℃. Anal. Calc. for C70H60Cl4N4Sn2: C, 62.91; H, 4.53; N, 4.19; Found:C,
62.89; H, 4.50; N, 4.22; IR (KBr, cm-1): 1637 (s, υasCOO); 1390 (s, υsCOO); 1574 (m, C=N-N=C); 634
1
(s, Sn-O-Sn); 526 (w, Sn-C); 474 (m, Sn-N). H NMR (CDCl3, δ ppm): 10.83 (s, 2H, Ar-OH), 8.20 (s,
1H, H1), 7.78-7.73(m 3H), 7.64(d, 1H, J=8 Hz), 7.57-7.55(m 3H ), 7.47(t, 1H, J=8 Hz), 7.31 (t, 1H, J=6
Hz), 7.24-7.20(m, 4H), 7.16(s, 1H, H4), 7.02-6.99(m, 4H), 2.99 (s, 4H, ArCH2Sn). 13C NMR (CDCl3, δ
ppm): 175.0 (COO), 163.2 (C=N), 155.8 (C3), 151.6 (CONH), 137.5(C10), 134.2(C-Cl),
133.2(C11),132.6，132.3, 130.8, 129.5, 129.3, 129.0, 128.6, 128.5, 127.8, 127.5, 126.4(aromatic
carbons), 123.8 (C7), 117.2 (C2), 111.6 (C4), 29.7 (ArCH2Sn).
4.4.5. {(o-F-Bz)2Sn[3-OH-C10H6CON2C(C6H5)CO2](C2H5OH)}2 (5)
Yield: 71%, M.p.: 113-114 °C. Anal. Calc. for C70H60F4N4O10Sn2: C, 59.20; H, 4.55; N, 3.84; Found: C,
59.01; H, 4.34; N, 4.56%. IR (KBr, cm–1): 1636(s, υasCOO); 1388(s, υsCOO); 1575(m, C=N-N=C);
1
633 (s, O-Sn-O); 525(w, Sn-C); 474 (m, Sn-N). H NMR (d-DMSO, δ ppm): 11.76(s, 1H, -ArOH),
8.48(s, 1H, H1), 7.88(d, 1H, J=8 Hz, H8), 7.62(d, 1H, J=8 Hz, H5), 7.43(t, 1H, J=8 Hz, H6), 7.28(t, 1H,
J=8 Hz, H7), 7.00(s, 1H, H4), 6.96(t, 2H, J=8 Hz, H13) 7.36-7.37(m, 3H), 7.10-7.09(m, 2H), 6.86-6.81(m,
2H), 6.71-6.66(m, 4H), 3.52(q, 2H, -OCH2-,J=8 Hz), 3.36(s, 1H, R-OH), 1.12(t, 3H, J=6 Hz,
-OCH2-CH3), 2.98(s, 4H, ArCH2Sn). 13C NMR (d-DMSO, δ ppm): 172.5 (COO), 162.6 (C=N),
160.2(C-F), 154.9 (C3), 147.8 (CONH), 135.5 (C10), 129.7(C11), 129.3, 128.4, 127.7, 126.7, 126.2,
125.7, 125.1, 125.0, 124.6, 122.2 (aromatic carbons), 121.8(C7), 118.2(C2), 109.2(C4), 55.7(-OCH2-),
17.4(-OCH2-CH3), 29.8 (ArCH2Sn).
4.5. In vitro cytotoxic activity
Stock solutions of complexes 1, 3 and the ligand were dissolved in DMSO at a concentrations of 10
mg/ml and diluted by cell culture medium to various working concentration. To avoid DMSO toxicity,
the concentration of DMSO was less than 0.1% (v/v) in all experiments.
12

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Briefly, cells were seeded onto 96-well flat-bottom plates for 24 hours before treatment to allow
attachment of cell to the wall of the plate, then fed with dilutions of each drug. The plates were
incubated at 37 , 5ꢃ CO2 for a period of 48 h. After 48 h, cells were fixed, washed, and stained with
sulforhodamine B stain. Excess stain was washed out with acetic acid and attached stain was recovered
with EDTA buffer. Color intensity was measured in an ELISA reader. The relation between surviving
fraction and tested compound concentrations is plotted to get the survival curve of each tumor cell line
after the cytotoxicity of the specified compound and IC50 (dose of the tested compound which reduces
survival to 50%) were evaluated.
As for MTT assay, the procedure was performed by the methods reported in the literature [6]. MTT
was added after exposed to organotin complexes for 48 h. 4 h later, the absorbance of the plates was
read at 490 nm with a ELx808 Absorbance Microplate Reader (Bio-Tek Co., USA).
4.6. Fluorescence spectra
Ethidium bromide
(EB)
and
ct-DNA were
dissolved
in
10
mmol
L-1
trihydroxymethylaminomethane (tris)-HCl buffer solution and the ct-DNA concentration per nucleotide
was determined by absorption spectroscopy using the molar absorption coefficient (6600 L mol-1 cm-1 )
at 260 nm, while the EB concentration was calculated by the ratio of the mass to its molecular weight.
The title compounds were dissolved in DMSO and the concentration was determined in the same way as
EB. The organotin complexes were added to the solution containing 25 ꢀmol L-1 ct-DNA and 3 ꢀmol L-1
EB at different concentrations (0, 12.5, 25, 37.5, 50, 62.5 ꢀM). After 2 h, fluorescence quenching
spectra were recorded at 530-700 nm with all samples excited at 258 nm.
4.7. Protein binding studies
The stock solution of proteins (100 ꢀM) was prepared by dissolving the solid BSA in 10 mM
phosphate buffer (pH = 7.4) and stored at 4°C for further use. A concentrated stock solution of the
compounds was prepared in DMSO at concentrations of 2.5×10-3 M and diluted by phosphate buffer.
Titrations were done manually by using a trace syringe and the fluorescence spectra were recorded with
excitation wavelength of BSA at 280 nm and the emission at 290-450 nm by keeping the concentration
of BSA constant (1.0 ꢀM) while varying the complex concentration from 0 to 10 ꢀM at room
temperature. For synchronous fluorescence spectra, the concentration of BSA was kept at 1.0 ꢀM and
the compounds of different concentrations were added and the spectra were measured at two different
13

ACCEPTED MANUSCRIPT
Δλ values (difference between the excitation and emission wavelengths of BSA), such as 15 and 60
nm.
5. Supplementary material
CCDC 919033 (for 1), 919034 (for 2), 919028 (for 3), 919029 (for 4) and 919030 (for 5) contain the
supplementary crystallographic data for this paper. 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.
Acknowledgements
We acknowledge the National Natural Foundation of China (21105042) and the Natural Science
Foundation of Shandong Province (ZR2011BM007, ZR2010BQ021, ZR2011BQ015) for financial
support. And this work was supported by Shandong “Tai–Shan Scholar Research Fund”.
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17

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Scheme Captions
Scheme 1. The reaction procedures.
Figure Captions
Fig. 1. Crystal structure of complexes 1, 3, 4 and 5 (hydrogen atoms are omitted for clarity). Atoms
drawn at 30% probability.
Fig. 2. Crystal structure of complex 2 (hydrogen atoms are omitted for clarity). Atoms drawn at 30%
probability.
Fig. 3. Effects of complexes 1 (A) and 3 (B) on the fluorescence spectra of EB-DNA system,
respectively. [DNA] = 25 µmol L-1 [EB] =3 µmol L-1, from 1 to 6, [VOL]/[DNA] = 0, 0.5, 1.0,
,
1.5, 2.0, 2.5, respectively; Inset: plot of I0/I vs. r (r = [VOL]/[DNA]). λex = 258 nm.
Fig. 4. Effects of complex 3 on the fluorescence (A) and synchronous spectra of BSA system (B, C).
[BSA] = 1.0 ꢀM, from 1 to 9, [VOL] = 0, 1.25, 2.5, 3.75, 5.0, 6.25, 7.5, 8.75, 10 ꢀM ,
respectively. ꢁλ = 60 nm (B) and ꢁλ = 15 nm (C), λex = 280 nm.
Fig. 5. Stern–Volmer plots (A) and Scatchard plots (B) of the fluorescence titration of complexes 1 and
3 with BSA.
Fig. S1. Absorption spectra of complexes 1(e), 2(d), 3(f), 4(a) and 5(b) and the ligand(c) at 1 × 10−4
M
in DMSO.
Fig. S2. Effects of complex 1 on the fluorescence(A) and synchronous spectra of BSA system. [BSA] =
1.0 ꢀM, from 1 to 9, [VOL] = 0, 1.25, 2.5, 3.75, 5.0, 6.25, 7.5, 8.75, 10 ꢀM , respectively. ꢁλ =
60 nm (B) and ꢁλ = 15 nm (C), λex = 280 nm.
Table Captions
Table 1. Crystal data and structure refinement parameters for complexes 1-5.
Table 2. Selected bond lengths (Å) and angles (ꢄ) for complexes 1, 3, 4 and 5.
Table 3. Selected bond lengths (Å) and angles (ꢄ) for complex 2
Table 4. Hydrogen bonding geometries for complexes 1-5.
Table 5. Half maximal inhibitory concentration (ug/ml) of complexes 1, 3 and the ligand against tumor
cell lines (n=3)..
Table 6. The quenching constant, binding constant and number of binding sites for the interactions of
complexes 1 and 3 with BSA.
18

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Table1. Crystal data and structure refinement parameters for complexes 1-5
Complex
1
2
3
4
5
C42H40N4O10S C29H36N2O5S C66H56N4O10S C70H60Cl4N4O10
C70H60F4N4O10
Sn2
Empirical formula
n2
n
n2
Sn2
Formula weight
Wavelength (Å)
Crystal system
Space group
a (Å)
998.16
611.29
1302.53
1496.40
1430.60
0.71073
Monoclinic
P21/C
0.71073
Monoclinic
P21/C
0.71073
Triclinic
P-1
0.71073
Triclinic
P-1
0.71073
Monoclinic
P21/C
7.3461(6)
19.9138(10)
13.8773(11)
90
9.1890(10)
10.1621(11)
15.9512(17)
100.576(2)
93.6980(10)
91.5290(10)
1460.0(3)
2
11.6700(12)
12.4841(14)
12.7469(13)
61.2340(10)
66.1330(10)
88.998(2)
1451.9(3)
1
14.8371(16)
11.1193(11)
19.7634(18)
90
14.9860(15)
10.8631(9)
20.179(2)
90
b (Å)
c (Å)
α (º)
β (º)
97.2290(10)
90
96.034(2)
90
96.7490(10)
90
γ (º)
V (Å3)
2014.0(3)
4
3242.5(6)
2
3262.2(6)
2
Z
Dcalc (Mg/m3)
ꢀ (mm-1)
F(000)
1.296
1.390
1.490
1.533
1.456
1.296
0.913
0.924
0.998
0.838
988
628
660
1512
1448
0.49 х 0.45 x 0.49 x 0.48 x 0.45 x 0.30 x 0.49
x
0.47
x
0.30 x 0.18 x
0.14
Crystal size (mm)
0.20
8946
3536
0.37
7576
5063
0.18
7600
5037
0.47
Reflections collected
15992
5713
15754
5736
Unique
[Rint]
reflections
[R(int)=0.060 [R(int)=0.020 [R(int)=0.019 [R(int)=
[R(int)=
0.0447]
3]
1]
6]
0.0321]
Data/restraints/parame
ters
5063 / 494 /
338
3536 / 0 / 264
5037 / 6 / 374 5713 / 0 / 407
5736 / 0 / 501
1.060
Goodness-of-fit on F2
1.037
1.072
1.125
1.089
R1 = 0.0358
Final R indices [I>2σ R1 = 0.0416
R1 = 0.0506
R1 = 0.0329
wR2 = 0.0633
R1 = 0.0491,
R1 = 0.0505
wR2 = 0.1025
R1 = 0.0928
wR2 = 0.1301
(I)]
wR2 = 0.0965 wR2= 0.1227
R1 = 0.0631 R1 = 0.0807
wR2 = 0.0811
R1 = 0.0616
R indices (all data)
wR2 = 0.1090 wR2 = 0.1547 wR2 = 0.0734 wR2 = 0.1002

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Table 2. Selected bond lengths (Å) and angles (º) for complexes 1, 3, 4 and 5
Complex
1
3
4
5
Sn(1)-O(3)
2.216(3)
2.299(4)
2.361(3)
2.373(3)
2.661(3)
1.345(5)
1.270(5)
1.292(5)
1.280(5)
1.238(5)
2.182(2)
2.294(3)
2.361(2)
2.315(2)
2.581(2)
1.331(4)
1.274(4)
1.293(4)
1.282(4)
1.234(4)
2.162(3)
2.244(3)
2.349(3)
2.428(3)
2.628(3)
1.332(5)
1.278(5)
1.290(5)
1.287(5)
1.232(5)
70.71(11)
68.94(11)
75.26(11)
65.12(10)
79.94(10)
2.181(4)
2.274(5)
2.393(4)
2.417(5)
2.638(4)
1.339(8)
1.287(7)
1.294(7)
1.289(7)
1.245(7)
70.56(16)
68.49(15)
75.99(16)
65.58(15)
79.41(15)
Sn(1)-N(1)
Sn(1)-O(1)
Sn(1)-O(5)
Sn(1)-O(1)#1
N(2)-C(9)
O(3)-C(9)
N(1)-C(2)
O(1)-C(1)
O(2)-C(1)
O(3)-Sn(1)-N(1)
N(1)-Sn(1)-O(1)
O(3)-Sn(1)-O(5)
O(1)-Sn(1)-O1#1
O(5)-Sn(1)-O1#1
C(20)-Sn(1)-C(21)
C(20)-Sn(1)-C(26)
C(20)-Sn(1)-C(27)
69.45(11) 69.54(8)
68.42(12) 68.34(8)
75.98(11) 76.05(8)
66.56(10) 67.71(8)
79.60(10) 78.37(7)
166.0(2)
171.66(13)
161.85(18) 163.2(3)
Symmetry transformations used to generate equivalent atoms: Complex 1: -x, 1-y, 1-z; Complex 3: -x+2, -y+1, -z;
Complex 4: -x, -y, -z+1; Complex 5: -x+1, -y+1, -z;
Table 3. Selected bond lengths (Å) and angles (º) for complex 2
Complex 2
Sn(1)-O(3)
Sn(1)-N(1)
Sn(1)-O(1)
Sn(1)-O(5)
2.175(4)
2.257(5)
2.304(4)
2.415(5)
O(3)-C(9)
N(1)-C(2)
O(1)-C(1)
O(2)-C(1)
1.288(7)
1.290(8)
1.275(7)
1.232(8)

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Sn(1)-C(24)
N(2)-C(9)
2.107(9)
1.324(8)
Sn(1)-C(20)
2.119(8)
O(3)-Sn(1)-N(1) 70.06(16)
N(1)-Sn(1)-O(1)
69.65(15) O(3)-Sn(1)-O(5) 78.95(16)
C(20)-Sn(1)-C(24) 162.5(4)
Table 4. Hydrogen bonding geometries for complexes 1-5
d(D-H) d(H...A) d(D...A)
<(DHA)
D-H...A
1
O(5)-H(5B)...O(4)#1 0.85
O(5)-H(5A)...O(2)#2 0.85
1.96
1.81
1.85
2.46
2.799(5) 167.7
2.656(4) 174.2
2.573(5) 146.9
2.788(5) 100.6
O(4)-H(4)...N(2)
C(10)-H(10)...O(3)
2
0.82
0.93
O(4)-H(4)...N(2)
O(5)-H(5)...O(2)#1
C(10)-H(10)...O(3)
3
0.82
0.82
0.93
1.90
1.82
2.42
2.615(6) 145.4
2.619(7) 166.4
2.759(8) 101.6
O(4)-H(4)...N(2)
O(5)-H(5)...O(2)#1
O(5)-H(5)...O(1)#1
4
0.82
0.85
1.85
1.75
2.65
2.580(4) 146.9
2.589(3) 167.9
3.101(3) 114.5
0.85
O(4)-H(4)...N(2)
O(5)-H(5)...O(2)#1
5
0.82
0.82
1.83
1.86
2.563(5) 147.3
2.628(5) 156.2
O(4)-H(4)...N(2)
O(5)-H(5)...O(2)#1
1.85
1.83
2.579(7) 147.1
2.628(7) 163.2
0.82
0.82
Symmetry code: (#1 for 1) x, -y+3/2, z-1/2; (#2 for 1) -x, -y+1, -z+1; (#1 for 2) -x+1, -y+2, -z; (#1 for 3) -x+2,
-y+1, -z; (#1 for 4) -x, -y, -z+1; (#1 for 5) -x+1, -y+1, -z;

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Table 5. Half maximal inhibitory concentration (ug/ml) of complexes 1, 3 and the ligand against tumor cell lines
(n=3).
IC50 (ug/ml)
Complex
SRB
MTT
SMMC-7721
21.96±1.20
8.47±0.70
>100
A549
P388
WiDr
HCT-116 A549
29.45±0.30 24.46±0.37 12.48±0.50
20.19±3.16 12.37±3.12 17.58±0.33
16.94
4.00
>100
53
30.36
18.32
>100
>60
1
3
>100
--
>100
>100
Ligand
cisplatin
--
Table 6. The quenching constant, binding constant and number of binding sites for the interactions of complexes 1
and 3 with BSA.
Compound
Ksv
Kq
n
Kbin
1
3
1.0877×105 1.0877×1013 1.237 1.72×106
1.0301×105 1.0301×1013 1.162 6.82×105

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