Synthesis, characterization, crystal structure, and DNA interaction of tin complexes containing pyridyl ligands

Article abstract of DOI:10.1007/s00706-016-1835-2

Abstract: The reactions of 4′-aryl-2,2′:6′,2′′-terpyridines (aryl?=?phenyl, p-tolyl, p-anisyl, p-chlorophenyl, 4-pyridyl) and 3-phenyl-1,5-bis(2-pyridyl)-1,5-pentanedione with dimethyltin(IV) dichloride and tin(II) dichloride have been investigated. The resulting products have been fully characterized by elemental analysis and multinuclear (¹H, ¹³C, ¹¹⁹Sn) NMR spectroscopy and X-ray crystal structure determination in the case of [SnCl₂(pytpy)] (pytpy?=?4′-(4-pyridyl)-2,2′:6′,2′′-terpyridine). The crystal structure of [SnCl₂(pytpy)] reveals that tin(II) is pentacoordinated in a highly distorted square pyramidal geometry. Moreover, the binding interaction of complex [SnCl₂(pytpy)] with calf thymus-DNA (ct-DNA) has been investigated using UV–Vis spectroscopy. Data reveals that the groove binding is a mode of the interaction with a moderate binding constant of 7.2 (±0.2)?×?10³?M^?1. Graphical abstract: [Figure not available: see fulltext.]

Full text of DOI:10.1007/s00706-016-1835-2

Monatsh Chem
DOI 10.1007/s00706-016-1835-2
ORIGINAL PAPER
Synthesis, characterization, crystal structure, and DNA
interaction of tin complexes containing pyridyl ligands
Badri Z. Momeni1 Vahid Noroozi1
•
Received: 19 February 2016 / Accepted: 9 August 2016
Ó Springer-Verlag Wien 2016
Abstract The reactions of 40-aryl-2,20:60,200-terpyridines
(aryl = phenyl, p-tolyl, p-anisyl, p-chlorophenyl, 4-pyr-
idyl) and 3-phenyl-1,5-bis(2-pyridyl)-1,5-pentanedione
with dimethyltin(IV) dichloride and tin(II) dichloride have
been investigated. The resulting products have been fully
characterized by elemental analysis and multinuclear (1H,
13C, 119Sn) NMR spectroscopy and X-ray crystal structure
determination in the case of [SnCl2(pytpy)] (pytpy = 40-(4-
pyridyl)-2,20:60,200-terpyridine). The crystal structure of
[SnCl2(pytpy)] reveals that tin(II) is pentacoordinated in a
highly distorted square pyramidal geometry. Moreover, the
binding interaction of complex [SnCl2(pytpy)] with calf
thymus-DNA (ct-DNA) has been investigated using UV–
Vis spectroscopy. Data reveals that the groove binding is a
mode of the interaction with a moderate binding constant
Keywords Tin Á Terpyridyl Á NMR Á Crystal structure Á
DNA
Introduction
The diversity of applications related to terpyridines and
their metal complexes calls for a high structural variability
of the basic 2,20:60,200-terpyridine subunit. In fact, ter-
pyridine units have been incorporated into supramolecular
dendrimers [1–4] and polymers [5–7]. In particular,
nowadays, terpyridine designs featuring p-conjugated
substituents, commonly attached in 40 position, are of
increasing interest. In the field of metallo-supramolecular
chemistry, 40-functionalized terpyridines have favorite
properties to be employed in structure, and a multitude of
terpyridine-functionalized polymers has been derived from
this structural motif [8–13]. By far, the most conjugated
terpyridine-containing systems used today are based on the
of 7.2 ( 0.2) 9 103 M-1
.
Graphical abstract
¨
so-called Krohnke-motif, which features a functionalized
phenyl moiety at the 40-position of the terpyridine unit [14].
Tin complexes are an attended family of compounds,
with dominant applications in chemical vapor deposition
(CVD), PVC stabilizers, chemical sensors, nonlinear
optics, supramoleculer structures, as well as organic syn-
thesis and catalysis [15]. Also, they are potentially
suitable for medicinal and biocidal purposes, due to their
biological activity [16, 17]. In addition, the organotin
complexes containing N-donor ligands show anticancer
activity [18, 19]. Widespread antitumor studies of tin
complexes have attracted interests to design complexes
specially using N-donor ligands, to follow the structures of
cisplatin family model [15]. However, activity of tin(II)
complexes of N-donor ligands, such as terpyridines (as
multiple N-donors) because of the capability to bind
Electronic supplementary material The online version of this
article (doi:10.1007/s00706-016-1835-2) contains supplementary
material, which is available to authorized users.
& Badri Z. Momeni
momeni@kntu.ac.ir
1
Faculty of Chemistry, K. N. Toosi University of Technology,
P.O. Box 16315-1618, Tehran 15418, Iran
123

B. Z. Momeni, V. Noroozi
through the nitrogens of DNA base pairs, or other inter-
acting modes may have noticeable results for this purpose.
In one of previous research reports on organotin ter-
pyridine complexes, Lewis has studied the effect of
dimethyltin(IV) as a transient template in condensation of
ligand [20]. In another report, the cytotoxicity of fluores-
cent organotin complexes of terpyridine derivatives have
been studied [21]. Also, we have studied the preparation of
dimethyltin(IV) complexes based on the pyridyl ligands
using different spectroscopic methods and X-ray crystal-
lography to demonstrate the geometry of the resulting
complexes which indicated that the functional group on
terpyridine ligand affects the coordination geometry of
tin(IV) in solution and the counterion [22].
IR spectroscopy, 1H, 13C, and 119Sn NMR spectroscopy, and
single crystal X-ray diffraction analysis in the case of
[SnCl2(pytpy)]. Also, the interaction of ct-DNA with com-
plex 5 has been studied using UV–Vis spectroscopy.
Solution studies
The study of prepared complexes 1–6 in solution, their
characterization and structural behavior in this state was
done by multinuclear NMR spectroscopy, including 1H,
13C, and 119Sn. Assignments of the 1H and 13C NMR
spectra were mainly based on the previous published data
for free ligands [23, 24].
1
The H NMR spectra of all complexes can be assigned
In this paper, we have studied the synthesis of dime-
thyltin(IV) dichloride and tin(II) dichloride complexes
containing a series of pyridyl ligands (40-aryl-2,20:60,200-
terpyridines (aryl = phenyl (Phtpy) L1, p-tolyl (toltpy) L2,
p-anisyl (atpy) L3, p-chlorophenyl (CPtpy) L4, 4-pyridyl
(pytpy) L5), and 3-phenyl-1,5-bis(2-pyridyl)-1,5-pentane-
dione (L6); Scheme 1) to demonstrate the solution
behavior and coordination geometry of prepared com-
plexes using spectroscopy and crystallography, besides the
binding interaction study of complex 5 with DNA.
based on two distinguished regions of aromatic and ali-
phatic (methyl) functional groups. While the comparison of
the spectra of ligands and related complexes confirms the
complex formation, assignments were done based on the
spectral patterns of free ligands and dimethyltin(IV)
dichloride in above two regions.
Information about the structure of methyltin(IV) com-
pounds in solution can be also drawn from the coupling
constants for the methyl carbons bonded to tin and the tin-
hydrogen coupling. Details of the mechanism are available
in the literature [25, 26]. The 119/117Sn satellites were
identified based on the previous observations [27]. It is
revealed that the magnitude of tin–hydrogen coupling con-
stant 2J (119Sn–1H), is also related to Me–Sn–Me angle [28]:
Results and discussion
Â
À
ÁÃ
Â
À
ÁÃ
All adducts of organotin(IV) and tin(II) dichlorides have
been prepared by the reaction of proper amounts of multi-
dentate polypyridyl ligands L1–L6 with dimethyltin(IV) and
tin(II) compounds. In the case of dimethyltin(IV), formation
of terpyridyl complexes has been shown in Scheme 2. Then,
the products were fully characterized by elemental analysis,
2
1
1
h ¼ ð0:0161Þ 2J 119Sn À H À ð1:32Þ 2J 119Sn À H
þ 133:4
ð1Þ
It has also been found that the magnitude of 1J
119Sn-13C) is linearly related to the Me–Sn–Me bond
(
Scheme 1
X
4
N
3
2
5
6
1
4'
3'
2'
O
O
5'
1
N
1''
N
N
N
N
N
2''
6''
5''
6
5
6'
N
N
2
3
1'
3''
4''
4
L1
L2
)
X = H ( ), CH3 ( ),
L5
L6
L3 L4
OCH3 ( ), Cl (
123

Synthesis, characterization, crystal structure, and DNA interaction of tin complexes…
Scheme 2
+
N
N
Me
Sn Cl
Me
Cl-
or
+ SnMe2Cl2
N
X
N
X
(SnMe2Cl3)-
N
N
spectra, and sometimes deviation from this issue occurs
when there is also sensitivity to the type of the solvents.
2
Table 1 1H chemical shifts and coupling constants, J(119/117Sn–H),
for prepared organotin(IV) complexes
0
0
For instance, for complex 4, H3 ,5 singlet peak shifts to
downfield when acetone is used instead of chloroform as
NMR solvent. Since there are data for approximate cal-
culation of chemical shifts of benzene derivatives [31], it is
possible to predict chemical shifts for the positions on
Compound
Solvent
Chemical shift/d
2J (119/117Sn–H)/Hz
Me2SnCl2
CDCl3
CDCl3
CDCl3
CDCl3
CDCl3
Acetone
Acetone
1.19
1.23
1.20
1.21
1.23
1.16
1.21
68.6/65.7
90.6
1
2
3
4
93.2
1
phenyl groups with low deviations, both in H and in 13C
92.5
NMR. Moreover, in the case of 13C NMR of complexes 1
and 2, DEPTQ-135 experiment was used for assignment of
carbons with confidence.
89.5/86.2
94.6/90.7
85.4
6
The 119Sn NMR spectra of complexes 1–3 in CDCl3
show signals at d = -121, -116, and -121 ppm,
respectively, which are in the range of five-coordinated
tin(IV) centers. Also, complexes 2 and 3 show other sig-
nals, respectively, at -64 and -69 ppm. The 119Sn NMR
spectrum of 4 in acetone-d6 shows a weak signal at
-150 ppm and an unexpected signal at -632 ppm that is
remarkably more negative than six-coordinated tin(IV)
chemical shift and its value is comparable with heptaco-
ordinated tin(IV), despite difference with previous reports
[32]. Moreover, 119Sn NMR spectroscopy of complex 5 in
DMSO indicates a shifted peak to upfield at -630 ppm
which is associated with coordinative capability of DMSO
to interact with tin center [15].
Also, the study of complex 6 by 119Sn NMR shows a
signal at ?10 ppm that is identified as a four-coordinated
tin(IV) center in acetone-d6 solution. It is noticeable that it
differs with the primary four-coordinated SnMe2Cl2 com-
pound that shows a signal at d(119Sn) = ?137 ppm in
dichloromethane solution [33]. Elemental analysis data
suggests that complex 6 might be as [SnMe2Cl(L6)]ClÁL6,
and 13C NMR data confirms it and shows the presence of
free ligand as cocrystal in complex 6. 13C NMR data of
complex 6 has two series of peaks, one series for the half of
bonded to organotin(IV) and other series related to head
not in complex that are also common with free ligand. We
have reported similar kind of structure previously [22]. The
1H NMR spectra of complex 6 shows a singlet at 1.21 ppm
angle, h, in tetra-, penta-, and hexa-coordinated di-, tri-,
and tetramethyltin(IV) (Eq. 2) [29]:
À
Á
1J 119Sn À13 C ¼ 11:4hÀ 875
ð2Þ
1
The H NMR spectrum of each one of the prepared
complexes shows signal at d * 1.20 ppm for methyl
groups connected to tin(IV), with coupling constants over
two bonds 2J(119/117Sn–1H), in the range of 85.4 Hz
2
\ J (119/117Sn–H) \94.6 Hz (Table 1) different from the
coupling constants of primary compound Me2SnCl2, which
are 2J (119Sn–H) = 68.6 and 2J(117Sn–H) = 65.7 Hz in
CDCl3 [30]. Application of Eq. (1) for complex 3 results in
h * 149.1° (based on 2J(119Sn–1H) = 92.5 Hz) and
Eq. (2)
results
in
h * 145.8°
(based
on
1J(119Sn–13C) = 787 Hz), which both are resulting in
solution state and the difference is less than 5°.
The 1H NMR spectra of the complexes 2 and 3 in CDCl3
display a singlet at d = 2.43 ppm and a singlet at
3.71 ppm, respectively; according to methyl and methoxy
on para positions of phenyl groups [31].
Structural difference of complexes 1–4 is only in sub-
stitutions on para position of the phenyl groups, so it is
expectable to have similar electronic environments, and
therefore similarity in the positions of spectral signals of
the equivalent pyridyl rings. This subject is slightly obvi-
1
ous in H NMR spectra and more clearly in 13C NMR
123

B. Z. Momeni, V. Noroozi
and its satellites with 2J(119/117Sn–H) = 85.4 Hz are
DNA-complex 5 as two variables using Solver option to
minimize the sum of standard deviations (S7) of experi-
mental and calculated absorbance (S6) in each spectrum at
260 nm. Also, the results show good curve fitting for cal-
culated and experimental absorbance data, in Fig. S1 (more
details are available in Supplementary Material). This
method is effective since the whole components in solution
(i.e., ct-DNA, complex 5 and their combined compound)
have absorbance in the studied UV–Vis area.
2
observable. This value, besides other near J values in this
range for complexes 1–4, proposes hexacoordinated envi-
ronment for tin centers in solution. However, this is just a
1
qualitative indication [34]. Also, it is noteworthy that H
NMR spectra have been determined immediately after
resolving in solvent, but in the case of 119Sn and 13C NMR,
the spectra have been determined overnight that increases
the chance of dissociation and might reduce the coordina-
tion number.
119Sn NMR spectroscopy results mention that the stud-
ied chemical species have different complicated structural
behavior in solution state, especially the fact that all
complexes dissociate to ionic species in solution. This was
also confirmed qualitatively by preliminary conductivity
measurements of the complexes 1–3 in distilled water,
acetone, and CHCl3. The conductivity test shows an order
of conductance for these complexes: 3 * 1 [ 2, while
solutions in water rationally had the most conductance (i.e.,
3: 820 lS, 1: 810 lS, and 2: 490 lS for 2 mM solutions in
water).
TheresultingKB valueis7.2( 0.2) 9 103 M-1. Thisvalue
is comparable with the reported values for compounds
[Zn(Phtpy)Cl2] (1.60 9 103 M-1), [Cd(Phtpy)2](NO3)2
(7.42 9 103 M-1) [35], [Pt(tpy)(SC4H9)]? (8.4 9 103 M-1);
[Pt(tpy)(OH)]? (7 9 104 M-1); [Pt(tpy)Cys]? (1.0 9
105 M-1) [36]. Also, its value is between tin(II) complexes of
[Sn(oda)(bpy)(H2O)2] (5.35 9 103 M-1
)
and [Sn(oda)
(phen)(H2O)2] (2.52 9 104 M-1) (phen (1,10-phenanthro-
line), bpy (2,20- bipyridine), and oda (oxydiacetate)) [37].
Addition of increasing amounts of ct-DNA to solutions
of complex 5 resulted in the obvious hyperchromism ten-
dency of the absorption bands at 260 nm, which has the
characteristic of ct-DNA. However, since the tin(II) com-
plex spectrum has a maximum absorbance band at 244 nm,
there is no subject to conclude that the band shifted to
260 nm is a reason for bathochromic effect of intercalating
mode of action. Moreover, the hyperchromic effect with a
significant red shift may suggest a binding propensity to ct-
DNA, possibly by electrostatic interaction, and stabiliza-
tion of the complex DNA adducts [38]. Also,
hypochromism in time dependent spectra of 1:1 molar ratio
for ct-DNA: complex 5 (Fig. 2) was observed. Generally,
this indication arises from a contraction in the helix axis of
ct-DNA [39]. So, it is more likely to consider the interac-
tion of ct-DNA and the complex 5 as groove binding (non-
DNA binding studies
The binding of ct-DNA with metal complex was studied
using electronic absorption spectroscopy. Absorption spectra
were recorded for varying concentrations of complex 5 and
ct-DNA to obtain different ratios of ct-DNA: complex
mixtures. The results have been shown in Fig. 1. The
intrinsic binding constant, KB, was measured with an
approach by considering the observed absorbance values as
well as initial concentrations of complex 5 and ct-DNA
solutions in equilibrium equations (S1–S5). The method
performed by employing the spreadsheet Excel program to
analyze data and calculate KB based on some different initial
guess of binding constant and extinction coefficient of ct-
Fig. 2 Absorption spectra of the 1:1 molar ratio solution of ct-DNA
and tin (II) complex (c = 2.90 9 10-5 M); arrow shows obvious
decrease in the absorbance intensity after passing specific time
periods (for 2 (a), 7 (b), 17 (c), 32 (d) and 55 (e) min after mixing)
Fig. 1 Absorption spectra of ct-DNA and tin (II) complex solutions;
arrow shows the increasing amounts of ct-DNA: metal complex ratios
[ri = 4.96n; n = 1–8 (a–h]
123

Synthesis, characterization, crystal structure, and DNA interaction of tin complexes…
intercalative), despite the capability of the ligand part of
the complex (pytpy) to interact with base pairs.
From the value of the binding constant (KB), Gibbs free
energy (DG) of the complex DNA compound can be cal-
culated using Eq. (3):
known [43], and complex 5 is one of the rare examples of
reported five-coordinate tin(II) complexes with a terpyridyl
ligand [44]. As it is obvious in crystal data, a position
seems not coordinated around Sn(II), even with the pres-
ence of an expanded ligand (L5), which has one extra N-
donor site in comparison with other terpyridines, and
potential of connection to a metal center.
DG ¼ ÀRT ln KB
ð3Þ
Binding constant represents the bound compound
stability while the free energy indicates the spontaneity
or non-spontaneity of complex DNA binding. The free
energy value, -22.02 kJ mol-1, shows the spontaneity of
the interaction [40].
In distorted square pyramidal geometry around Sn(II),
two chlorine atoms have occupied trans positions and the
Cl(1)-Sn-Cl(1i) angle is 159.85° which significantly devi-
ates from linearity. Other trans positions occupied by
nitrogen atoms show N(2)–Sn(1)–N(2i) angle of 136.45°
which is significantly nonlinear, and steric effect of rigid
N-donation sites are responsible for it. Dihedral angles of
two connected rings in coordinated side of the ligand,
C(7)–C(1)–C(2)–C(6) and N(1)–C(1)–C(2)–N(2) are 7.8°
and 7.3°, respectively. It shows three pyridyl rings with
slightly nonparallel configuration. In previous report [44],
the side rings have 4.2° angles with central ring, when the
ligand is just 2,20:60,200-terpyridine. However, the fourth,
non-coordinated pyridyl ring is significantly out of the
plane and C(10)–(C9)–C(8)–C(7) dihedral angle is 23.6°.
All bond lengths are quite near to similar ones in reported
structure [44]. For instance, Sn(1)–N(1), Sn(1)–N(2), and
Description and discussion of the crystal structure
of 5
The molecular structure of [SnCl2(pytpy)] (5) is shown in
Fig. 3. The coordination geometry around Sn(II) can be
described as significantly distorted square pyramidal, since
its geometry parameter s = 0.39 (s = (b - a)/60°, where
b and a are the largest two angles in the coordination
center; s = 0 for a perfect square pyramidal and 1 for a
perfect trigonal bipyramidal [41, 42]). Nitrogen atom of the
middle pyridyl ring occupies axial position, while other
coordinated atoms, 2N and 2Cl, build up the equatorial
plane. In complex 5 similar to other tin(II) complexes, the
coordination sphere includes space for the stereochemi-
cally active lone electron pair [15]. Different examples of
2-, 3-, 4-, 6-, 7-, and 8-coordinate tin(II) complexes are
˚
Sn(1)–Cl(1) bonds, with 2.336, 2.382, and 2.688 A lengths,
respectively, have inconsiderable differences with bond
distances reported previously.
The pyridyl–terpyridine ligands in three dimensional
crystal structure of the complex 5 lie in antiparallel layers,
as is obvious in Fig. 4, which is viewed down through the
axis b.
Fig. 3 ORTEP diagram for [SnCl2(pytpy)]. Selected bond distances
˚
(A) Sn(1)–N(1) 2.336(3), Sn(1)–N(2) 2.382(3), Sn(1)–Cl(1)
2.6879(9). Selected bond angles (°) N(1)–Sn(1)–N(2) 68.23(6),
N(2)–Sn(1)–N(2i) 136.45(12), N(1)–Sn(1)–Cl(1) 79.93(2), N(2)–
Sn(1)–Cl(1) 83.67(7), N(2i)–Sn(1)–Cl(1) 88.88(7), N(1)–Sn(1)–
Cl(1) 79.93(2), Cl(1)–Sn(1)–Cl(1i) 159.85(4), C(1)–N(1)–C(1i)
119.3(3), C(1)–N(1)–Sn(1) 120.37(17), C(3)–N(2)–Sn(1) 120.5(2),
C(2)–N(2)–Sn(1) 119.5(2)
Fig. 4 Crystal structure of [SnCl2(pytpy)] along the b axis
123

B. Z. Momeni, V. Noroozi
(w), 1610 (m), 1545 (m), 1478 (m), 1413 (m), 1253 (m),
1110 (m), 1021 (m), 890 (w), 797 (s), 765 (s), 689
Experimental
(m) cm-1
;
1H NMR (CDCl3): d = 8.88 (d, 2H,
All chemicals were reagent grade and were used as
received. Elemental analyses were performed on a Perkin-
Elmer 2400 II elemental analyzer. A Bante510 benchtop
conductivity meter was used to test the conductance of
prepared complexes 1–3 in water, acetone, and CHCl3
solutions. IR spectra in the 4000–400 cm-1 were recorded
on KBr pellet using ABB Bomem Model FTLA200-100
spectrophotometer. UV–Vis spectra of solutions recorded
in quartz cuvettes using Analytic Jena SPECORD 210.
NMR data were recorded using Bruker Biospin GmbH
500 MHz and Bruker FT-NMR300 (300 MHz) spectrom-
eters. All the chemical shifts and coupling constants are
3J (HH) = 4.3 Hz, H6, 6 ), 8.78 (s, 2H, H3 , 5 ), 8.73 (d,
00
0
0
2H, 3J (HH) = 8.0 Hz, H3,
3J (HH) = 11.0 Hz, J (HH) = 4.5 Hz, H4, 4 ), 7.96 (d,
2H, 3J (HH) = 7.2 Hz, HPh2,6), 7.55 (dd, 2H, 3J = 7.2 Hz,
), 7.99 (dt, 2H,
300
3
00
3J
3J
(HH) = 5.9 Hz,
H5,
),
7.49
(dd,
1H,
500
(HH) = 5.3 Hz,
3J (HH) = 6.8 Hz, 3J (HH) = 5.3 Hz, HPh3,5), 1.23 (s,
HPh4),
7.46
(dd,
2H,
6H, J (119/117Sn–H) = 90.6 Hz, Me–Sn) ppm; 13C NMR
2
00
0
0
00
(CDCl3): d = 155.0 (C2, 2 ), 151.2 (C2 , 6 ), 149.0 (C6, 6 ),
0
147.0 (C4 ), 138.0 (CPh1), 137.7 (C4, 4 ), 129.4 (CPh3,5),
00
00
00
129.1 (CPh4), 127.5 (CPh2,6), 124.4 (C5, 5 ), 121.9 (C3, 3 ),
119.5 (C3 , 5 ), 16.8 (Me–Sn) ppm; 119Sn NMR (CDCl3):
reported in ppm and Hz, respectively. The H, 13C, and
1
0
0
119Sn NMR spectra are reported relative to TMS (1H, 13C)
and SnMe4 (119Sn). Calf thymus-DNA, 2-acetylpyridine,
and 4-pyridylcarbaldehyde were purchased from Sigma-
Aldrich and all substituted benzaldehydes, dimethyltin(IV)
dichloride, and Tris-Base buffer were purchased from
Merck.
d = -122 ppm.
{Chlorodimethyl[40-(4-methylphenyl)-2,20:60,200-ter-
pyridine-j3-N,N0,N00]tin(IV)} chloride dihydrate
(2, C24H23Cl2N3SnÁ2H2O)
ꢀ
Yield: 67 %; m.p.: 172–174 °C; IR (KBr): m = 3414 (br),
3037 (m), 2972 (m), 2920 (m), 2861 (m), 1603 (s), 1545
(m), 1476 (m), 1421 (m), 1396 (m), 1252 (w), 1112 (w),
1
Preparation of ligands L1–L6
The one-pot preparation method of Krohnke type 4 -aryl-
2,20:60,200-terpyridine ligands was performed to obtain
1017 (w), 795 (s) cm-1; H NMR (CDCl3): d = 9.05 (d,
0
¨
2H, 3J (HH) = 4.4 Hz, H6,
), 8.79 (d, 2H,
600
3J (HH) = 9.9 Hz, H3, 3 ), 8.77 (s, 2H, H3 , 5 ), 8.14 (t,
00
0
0
ligands L1–L5 according to the literature [23] with a
2H, 3J (HH) = 7.7 Hz, H4,
), 7.90 (d, 2H,
slight
modification.
2-Acetylpyridine
(0.56 cm3,
400
3J (HH) = 8.1 Hz, HPh2,6), 7.59 (m, 2H, H5, 5 ), 7.36 (d,
5.0 mmol) was added to a solution of 0.25 cm3 benzalde-
hyde (2.5 mmol) in 18 cm3 ethanol. After addition of the
mixture of 0.280 g KOH (5.0 mmol) and 0.5 cm3 NH3
(25 %, 6.5 mmol), the solution was stirred overnight at
room temperature, during which time as orange suspension
was appeared. The solid was collected by filtration and
washed with EtOH (3 9 6 cm3). Then, the crude solid
product was recrystallized by cooling the hot supersatu-
rated ethanolic solution. The preparation method of
diketone ligand (L6) was performed similar to the above
procedure for the preparation of substituted phenyl ter-
pyridines without the addition of ammonia. The prepared
ligand was characterized in good agreement with the
literature [24].
00
3
2H, J (HH) = 8.0 Hz, HPh3,5), 2.43 (s, 3H, Me-Ph), 1.20
(s, 6H, 2J (119/117Sn-H) = 93.2 Hz, Me-Sn) ppm; 13C
00
0
0
NMR (CDCl3): d = 152.9 (C2, 2 ), 152.3 (C2 , 6 ), 148.6
00
(C6, 6 ), 140.7 (CPh1), 139.4 (C4, 4 ), 133.8 (CPh4), 130.1
00
5, 500
3, 300
),
(CPh3,5), 127.5 (CPh2,6), 125.6 (C
), 123.1 (C
120.2 (C 3 , 5 ), 21.4 (Me-Ph), 18.8 (Me-Sn) ppm; 119Sn
0
0
NMR (CDCl3): d = -64, -116 ppm.
{Chlorodimethyl[40-(4-methoxyphenyl)-2,20:60,200-ter-
pyridine-j3-N,N0,N00]tin(IV)} trichlorodimethylstannate(IV)
(3, C26H29Cl4N3OSn2)
ꢀ
Yield: 70 %; m.p.: 185–187 °C; IR (KBr): m = 3426 (br),
3062 (w), 3014 (w), 2922 (m), 2839 (w), 1600 (s), 1530 (m),
1478 (m), 1408 (m), 1249 (s), 1183 (s), 1016 (s), 794
(s) cm-1
1H NMR (CDCl3): d = 9.35 (d, 2H,
{Chlorodimethyl(40-phenyl-2,20:60,200-terpyridine-j3-
N,N0,N00)tin(IV)} trichlorodimethylstannate(IV)
;
3
3J (HH) = 4.0 Hz, H6, 6 ), 9.07 (d, 2H, J (HH) = 7.8 Hz,
00
3
H3,3 ), 8.85 (s, 2H, H3 , 5 ), 8.49 (t, 2H, J (HH) = 7.5 Hz,
00
0
0
(1, C25H27Cl4N3Sn2)
3
H4, 4 ), 8.11 (d, 2H, J (HH) = 8.5 Hz, HPh2,6), 7.87 (t, 2H,
00
To a solution of 55 mg dimethyltin dichloride (0.25 mmol)
in 5 cm3 dichloromethane was added a solution of 77 mg
Phtpy (L1, 0.25 mmol) in 5 cm3 dichloromethane. The
mixture was then stirred overnight at room temperature. In
the case of soluble product, the solvent was evaporated to
concentrate. Then, the solid was formed by the addition of
diethyl ether. It was washed two times more with diethyl
3J (HH) = 5.9 Hz, H5, 5 ), 7.01 (d, 2H, J (HH) = 8.6 Hz,
3
00
2
H
Ph3,5); 3.71 (s, 3H, Me-O), 1.21 (s, 12H, J (119/117Sn–
H) = 92.5 Hz, Me–Sn) ppm; 13C NMR (CDCl3): d = 162.2
00
0
0
0
(CPh4), 154.7 (C2, 2 ), 150.1 (C2 , 6 ), 148.9 (C4 ), 147.9
00
(C6, 6 ), 141.7 (C4, 4 ), 129.8 (CPh2,6), 127.1 (C5, 5 ), 124.5
00
00
00
0
0
(C3, 3 ), 120.9 (C3 , 5 ), 115.1 (CPh3,5), 55.5 (Me-O), 18.4
1
(1J (119Sn-C) = 787 Hz, J (117Sn-C) = 751 Hz, Me-Sn)
ppm; 119Sn NMR (CDCl3): d = -69, -121 ppm.
ꢀ
ether. Yield: 60 %; m.p.: 173–175 °C; IR (KBr): m = 3454
123

Synthesis, characterization, crystal structure, and DNA interaction of tin complexes…
2
{Chlorodimethyl[40-(4-chlorophenyl)-2,20:60,200-terpyridine-
j3-N,N0,N00]tin(IV)} trichlorodimethylstannate(IV)
monohydrate (4, C25H26Cl5N3Sn2•H2O)
9H, J (119/117Sn–H) = 85.4 Hz, Me–Sn) ppm; 13C NMR
0
(acetone-d6): d = 200.5 (C=O), 154.9 (C2), 154.2 (C2 ),
0
149.8 (C6 ), 148.8 (C6), 145.8 (Ph1), 138.0 (C4 ), 137.0
0
Yield: 40 %; m.p.: 184–186 °C; IR (KBr): mꢀ = 3440 (br),
3065 (m), 3014 (w), 2917 (w), 1606 (s), 1543 (m), 1484 (s),
1427(m), 1397 (m), 1306 (w), 1251 (m), 1168 (w), 1088
(C4), 129.3 (Ph4), 129.0 (Ph3,5), 128.5 (C3), 128.2 (Ph2,6),
0
0
127.4 (C5), 126.9 (C5 ), 121.6 (C3 ), 41.9 (CH2), 37.2 (CH),
12.7 (Me–Sn, 1J (119/117Sn–C) = 845 Hz) ppm; distin-
guished 13C NMR data for free L6 (rather than common
peaks): d = 206.5 (C=O), 128.6, 128.3, 122.1, 44.5 (CH2)
ppm; 119Sn NMR (acetone-d6): d = 10 ppm.
1
(m), 1016 (s), 896 (w), 791 (s) cm-1; H NMR (CDCl3):
3
00
d = 9.21 (d, 2H, J (HH) = 4.8 Hz, H6, 6 ), 8.97 (d, 2H,
3J (HH) = 8.0 Hz, H3,3 ), 8.81 (s, 2H, H3 , 5 ), 8.34 (t, 2H,
00
0
0
3J (HH) = 7.8 Hz, H4, 4 ), 8.01 (d, 2H, J (HH) = 8.5 Hz,
3
00
H
Ph2,6), 7.75 (t, 2H, 3J (HH) = 6.3 Hz, H5, 5 ), 7.44 (d, 2H,
UV–Vis absorption spectra of DNA solutions
00
3J (HH) = 8.6 Hz, HPh3,5), 1.23 (s, 12H, 2J (119Sn–
H) = 89.5 Hz, 2J (117Sn–H) = 86.2 Hz, Me–Sn) ppm;
The stock solution of ct-DNA was prepared in Tris-Base
buffer, adjusted at neutral pH and stored overnight at 4 °C.
Solutions of ct-DNA and complex were scanned using
quartz cuvettes. The concentration of the nucleotide was
determined by UV–Vis absorption spectroscopy using the
molar absorption coefficient (e = 6600 M-1 cm-1) at
260 nm. Absorbance measurements were performed by
keeping the constant concentration of complex 5 (30 lM)
while varying the ct-DNA concentration. The samples were
incubated at room temperature for 7 min before each
spectral determination. Also, in other sample, time
dependent absorbance determination was performed by
13C NMR (acetone-d6): d = 155.7 (C2, 2 ), 154.6 (C2 , 6 ),
00
0
0
00
150.9 (C6, 6 ), 149.9 (C4 ), 139.1 (CPh1), 137.3 (C4, 4 ),
0
00
00
136.2 (CPh4), 130.3 (CPh3,5), 129.8 (CPh2,6), 126.0 (C5, 5 ),
122.7 (C3, 3 ), 120.0 (C3 , 5 ), 14.5 (Me–Sn) ppm; 119Sn
00
0
0
NMR (acetone-d6): d = -150, -632 ppm.
Dichloro[40-(pyridine-4-yl)-2,20:60,200-terpyridine-j3-
N,N0,N00]tin(II) monohydrate (5, C20H14N4Cl2Sn•H2O)
Tin(II) chloride (29 mg, 0.15 mmol) was dissolved in THF
and mixed with solution of 47 mg L5 (0.15 mmol) in
CH2Cl2. Immediately, an orange solid was appeared that
stirred for 24 h and then discarded by centrifuge and
washed with CH2Cl2. Yield: 78 %; m.p.: 266–268 °C; IR
ꢀ
(KBr): m = 3409 (br), 2922 (w), 1747 (w), 1601 (m), 1536
Table 2 Experimental details, crystal data and refinement parameters
for complex 5
(w), 1485 (w), 1407 (m), 1304 (w), 1251 (w), 1158 (w),
1091 (w), 1016 (m), 896 (w), 796 (s), 749 (m), 665
1
Chemical formula
C20H14Cl2N4Sn
499.96
(s) cm-1; H NMR (DMSO-d6): d = 8.86 (s, 2H, H3 , 5 ),
0
0
Formula weight/g mol-1
Crystal system, space group
Temperature/K
00
00
8.85-8.77 (m, 6H, H3, 3 , H6, 6 and HPy2,6), 8.14 (t, 2H,
Orthorhombic, Pbcn
295
3J (HH) = 7.6 Hz, H4, 4 ), 8.01 (d, 2H, J (HH) = 4.6,
Py3,5), 7.64 (t, 2H, J (HH) = 5.8 Hz, H5, 5 ) ppm; 13C
3
00
3
00
H
˚
a/A
11.485 (2)
18.360 (4)
9.1006 (18)
1919.0 (7)
4
00
00
NMR (DMSO-d6): d = 155.4 (C2, 2 ), 150.6 (C6, 6 ), 149.0
˚
b/A
0
(CPy2,6), 147.5 (C4 ), 144.7 (CPy4), 138.1 (C4, 4 ), 125.2
00
˚
c/A
00
00
0
0
(C5, 5 ), 121.7 (C3, 3 ), 121.5 (CPy3,5), 118.6 (C3 , 5 ) ppm;
3
˚
V/A
119Sn NMR (DMSO-d6): d = -630 ppm.
Z
F(000)
984
{Chlorodimethyl[3-phenyl-1,5-bis(pyridine-2-yl)pentane-
1,5-dione-j2-N,O]} chloride [3-phenyl-1,5-bis(pyridine-2-
yl)pentane-1,5-dione] dichloromethane disolvate
(6, C44H42Cl2N4O4Sn•CH2Cl2)
Dx/Mg/m-3
Radiation type
l/mm-1
1.731
˚
Mo Ka, k = 0.71073/A
1.62
ꢀ
Yield: 30 %; m.p.: 125–127 °C; IR (KBr): m = 3429 (br),
Crystal size/mm
0.22 9 0.14 9 0.13
3057 (w), 2919 (w), 1692 (s), 1586 (m), 1492 (w), 1410
(m), 1357 (m), 1288 (m), 1223 (w), 1154 (w), 996 (s), 781
(s), 759 (s), 701 (s) cm-1; 1H NMR (acetone-d6): d = 8.68
No. of measured, independent and 6372, 1880, 1657
observed [I [ 2r(I)] reflections
Rint
0.040
-1
(d, 2H, 3J (HH) = 4.7 Hz, H6,
), 7.94 (dt, 2H,
˚
(sin h/k)max/A
0.617
600
0
R[F2 [ 2r(F2)], wR(F2), S
No. of reflections
0.034, 0.082, 1.07
3J (HH) = 7.8 Hz, J (HH) = 1.6 Hz, H4,4 ), 7.91 (t, 2H,
4
3J (HH) = 7.8 Hz, H3, 3 ), 7.59 (m, 2H, H5, 5 ), 7.38 (d, 2H,
0
0
1880
125
3J (HH) = 7.6 Hz, HPh2,6), 7.23 (t, 2H, 3J (HH) = 7.3 Hz,
No. of parameters
3
Ph3,5), 7.11 (t, 1H, J (HH) = 7.1 Hz, HPh4), 4.12 (qui,
H
H-atom treatment
H atoms treated by a mixture of
independent and constrained
refinement
1H, 3J (HH) = 7.1 Hz, CH), 3.83 (dd, 2H,
2J (HH) = 17.3 Hz, 3J (HH) = 7.7 Hz, CH2), 3.56 (dd,
-3
˚
Dqmax, Dqmin/e A
0.38, -0.46
2
2H, J (HH) = 16.9 Hz, J (HH) = 6.3 Hz, CH2), 1.21 (s,
3
123

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keeping constant concentration of both metal complex and
ct-DNA (1:1), in given periods (Fig. 2).
X-ray crystal structure determination
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Red single crystals of complex 5 were grown from slow
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Crystallographic data were collected on an MAR345 dtb
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non-hydrogen atoms were refined anisotropically. Hydro-
gen atoms were added at ideal positions and refined using a
riding model. A summary of crystal data, experimental
details, and refinement results is given in Table 2. CCDC
995748 contains 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. Other supple-
mentary data related to this article is also available.
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Acknowledgments We thank the Science Research Council of K.
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