Bioactive hepta- and penta-coordinated supramolecular diorganotin(IV) Schiff bases

Article abstract of DOI:10.1016/j.jorganchem.2013.05.019

This article describes the synthesis, characterization and bioactivity of dimethyl (1), diethyl (2), diphenyl (3), di-n-octyl (4), di-tert-butyl (5), n-butylchlorotin(IV) (6) derivatives of N0-(2-hydroxy-3- methoxybenzylidene) formohydrazide ligand. On the basis of presence or absence of steric factor, these compounds are either mononuclear in which Sn atom is in distorted trigonal bipyramidal geometry (3) or homobimetallic with each Sn atom in pentagonal bipyramidal environment (1). Packing diagrams suggest that the H/N, H/φ and φ/ φ interactions play a seminal role in generating fascinating supramolecular structures. These complexes show good antileishmanial, antiurease, antibacterial and antifungal activities. Moreover, the antileishmanial activity of 3 and 5 is comparable with standard antileishmanial drug Amphotericin B.

Full text of DOI:10.1016/j.jorganchem.2013.05.019

Journal of Organometallic Chemistry 741-742 (2013) 59e66
Contents lists available at SciVerse ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Bioactive hepta- and penta-coordinated supramolecular
diorganotin(IV) Schiff bases
,
b
,
a,
c
a
a,
*
Shaukat Shujah a
, Zia-ur-Rehman , Niaz Muhammad , Afzal Shah , Saqib Ali
,
**
*
Nasir Khalid d, Auke Meetsma e
a Department of Chemistry, Quaid-i-Azam University, Islamabad 45320, Pakistan
b Department of Chemistry, Kohat University of Science & Technology, Kohat, Pakistan
c Department of Chemistry, Abdul Wali Khan University Mardan, Pakistan
d Chemistry Division, Pakistan Institute of Nuclear Science and Technology, PO Nilore, Islamabad, Pakistan
e Crystal Structure Center, Chemical Physics, Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, NL-9747 AG Groningen, The
Netherlands
a r t i c l e i n f o
a b s t r a c t
Article history:
This article describes the synthesis, characterization and bioactivity of dimethyl (1), diethyl (2), diphenyl
(3), di-n-octyl (4), di-tert-butyl (5), n-butylchlorotin(IV) (6) derivatives of N0-(2-hydroxy-3-
methoxybenzylidene)formohydrazide ligand. On the basis of presence or absence of steric factor, these
compounds are either mononuclear in which Sn atom is in distorted trigonal bipyramidal geometry (3)
or homobimetallic with each Sn atom in pentagonal bipyramidal environment (1). Packing diagrams
Received 14 March 2013
Received in revised form
6 May 2013
Accepted 14 May 2013
suggest that the H/N, H/
p and p/p interactions play a seminal role in generating fascinating su-
Keywords:
pramolecular structures. These complexes show good antileishmanial, antiurease, antibacterial and
antifungal activities. Moreover, the antileishmanial activity of 3 and 5 is comparable with standard
antileishmanial drug Amphotericin B.
Supramolecular
Hepta-coordinated organtin
Antileishmanial
Antiurease
Ó 2013 Elsevier B.V. All rights reserved.
Antibacterial
Antifungal
1. Introduction
meets well with the above two mentioned criteria. In addition to
this, fine-tuning of chemical, physical, and structural properties of
Supramolecular organometallic compounds generated through
non-covalent interactions such as coordinative bonds, hydrogen
the supramolecular system can be made by modulating the organic
groups attached to the tin atom.
bonds, or
p
/
p
interactions are of particular interest due to their
In recent years, organotin Schiff bases have been paid equitable
attention due to their stimulating structural features and because of
their versatile applications in various fields like catalysis, biotech-
nology, analytical and medicinal chemistry [4e6]. In ONO tri-
dentate ligands based derivatives of organotins, the tin atom is
typically penta-coordinate with a trigonal bipyramidal or square-
pyramidal geometry [7]. In addition to this, supramolecular archi-
tectures can be achieved through self-organization of molecules by
non-covalent forces including hydrogen bonding, hydrophobic,
interesting structural architectures and applications in various
fields [1,2]. Although considerable advancement has been made in
the field of supramolecular chemistry yet little is known about
assemblies derived from organometallic building blocks. Moreover,
in comparison to transition metals and lanthanides, few supra-
molecular aggregates containing main group elements are known
because of their less kinetic and thermal stability, and because of
the inappropriate size of the metal center to coordinate with
chelating-ligand functions [3] Among the main group elements tin-
directed self-assembly has received the most attention because it
hydrophilic effects, electrostatic and p/p interactions etc. [8].
In view of all these considerations, we aimed to synthesis and
characterize monometallic (trigonal bipyramidal) and bimetallic
(pentagonal bipyramidal) organotin(IV) derivatives of N0-(2-
hydroxy-3-methoxybenzylidene)formohydrazide ligand and sub-
sequently screened them for antimicrobial and antiurease activ-
ities. Some of these compounds have promising antileishmanial
activity, and after further investigations may emerge as new tin-
based antileishmanial agents.
* Corresponding authors. Tel.: þ92 5190642208; fax: þ92 512873869.
** Corresponding author. Department of Chemistry, Quaid-i-Azam University,
Islamabad 45320, Pakistan.
E-mail addresses: shaukat.shujah@yahoo.com (S. Shujah), zrehman@qau.edu.pk
( Zia-ur-Rehman), drsa54@yahoo.com (S. Ali).
0022-328X/$ e see front matter Ó 2013 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.jorganchem.2013.05.019

60
S. Shujah et al. / Journal of Organometallic Chemistry 741-742 (2013) 59e66
2. Experimental
The mass spectra were recorded on a MAT-311A Finnigan
(Germany). The m/z values were evaluated assuming that H ¼ 1,
2.1. Chemicals and instrumentation
C ¼ 12, N ¼ 14, O ¼ 16, Cl ¼ 35 and Sn ¼ 120.
The X-ray diffraction data were collected on a Bruker SMART
APEX CCD diffractometer, equipped with a 4 K CCD detector. Data
integration and global cell refinement was performed with the
program SAINT. The program suite SAINTPLUS was used for space
group determination (XPREP). The structure was solved by Patter-
son method; extension of the model was accomplished by direct
method and applied to different structure factors using the pro-
gram DIRDIF. All refinement calculations and graphics were per-
formed with the program PLUTO and PLATON package [10].
Organotin(IV) dichlorides, dioctyltin(IV) oxide, n-butyl-
chlorotin(IV) dihydroxide, formic hydrazide and 2-hydroxy-3-
methoxybenzaldehyde were procured from Aldrich. The organic
solvents used were of Merck, Germany. These solvents were freshly
dried using standard procedures [9].
The melting points were recorded on an electrothermal
melting point apparatus, model MP-D Mitamura Rieken Kogyo
(Japan) by using capillary tubes and are uncorrected. The infrared
(IR) spectra were recorded using NaCl cells or KBr pellets on a Bio-
Rad Excaliber FT-IR, model FTS 300 MX spectrophotometer (USA)
in the frequency range of 4000e400 cmꢀ1. Multinuclear NMR (1H,
13C, and 119Sn) spectra were recorded on a Bruker ARX 300 MHz-
2.2. Synthesis
2.2.1. Synthesis of N0-(2-hydroxy-3-methoxybenzylidene)
formohydrazide (H2L)
FT-NMR and
a
Bruker 400 MHz-FT-NMR spectrometers
Switzerland using CDCl3 as an internal reference. Chemical shifts
An ethanolic solution of 2-hydroxy-3-methoxybenzaldehyde
2.53 g (16.65 mmol) was added slowly to the solution of formic
hydrazide 1.0 g (16.65 mmol), in ethanol with constant stirring at
room temperature. The mixture was refluxed for 1 h and on cooling
yellow crystalline solid was obtained (Scheme 1a and b).
(d) and coupling constants (J) are given in ppm and Hz, respec-
tively. The multiplicities of signals in 1H NMR are given with
chemical shifts; (s ¼ singlet, d ¼ doublet, t ¼ triplet, q ¼ quartet,
m ¼ multiplet).
amido form
iminol form
R/Cl
Scheme 1. Synthesis of N0-(2-hydoxy-3-methoxybenxylidene)formohydrazide (H2L) (a,b) diorganotin(IV) and butylchloridetin(IV) derivatives (cee).

S. Shujah et al. / Journal of Organometallic Chemistry 741-742 (2013) 59e66
61
Yield 83%, m.p. 176e177 ꢁC. Anal. Calc. for C9H10N2O3 (M ¼ 194):
2.2.4. Diphenyltin(IV) [N0-(3-methoxy-2-oxidobenzylidene)-N-
(oxidomethylene)hydrazine] (3)
C, 55.67; H, 5.19; N, 14.43 Found: C, 55.70; H, 5.21; N, 14.39%. EI-MS,
m/z (%): [C9H10N2O3]þ 194 (100.0), [C8H9N2O2]þ 165 (3.9),
[C8H7NO2]þ 149 (81.3), [C8H6NO]þ 132 (9.9), [C7H7O2]þ 123 (7.2),
Compound 3 was prepared in the same way as 1, using following
precursors quantities: N0-(2-hydroxy-3-methoxybenzylidene)for-
mohydrazide 0.58 g (3.0 mmol), diphenyltin(IV) dichloride 1.03 g
(3.0 mmol), triethylamine 0.84 mL (6.0 mmol) were reacted in 1:1:2
ratio. Solid product was recrystallized from chloroform and n-
hexane (4:1) mixture.
[C7H5NO]þ 119 (19.2), [C6H5]þ 77 (11.7) FT-IR (cmꢀ1): 3173m, nNeH
;
3385m, nOeH; 1691s, nC]O; 1625 nC]N; 1055 nNeN. 1H NMR (ppm):
H-3: 6.97 (dd, 1H, phenyl, 3JHeH ¼ 8.1), H-4: 6.79 (t, 1H, phenyl, 3JHe
3
¼ 8.1), H-5: 7.22 (dd, 1H, phenyl, JHeH ¼ 7.8), H-7: 8.36 (s, 1H,
H
CH]N), H-8: 11.66 (s,1H, CHO), H-9: 3.83 (s, 3H, OCH3), NH: 8.66 (s,
1H, NH), OH: 10.10 (s, 1H, OH), 13C NMR (ppm): C-7: 143.3 (HC]N);
C-8: 165.2 (CHONH); 146.4, 148.4, 120.7, 119.6, 118.4, 113.4 (PheC):
C-9: 56.3 (OCH3).
Yield 82%, m.p. 120e121 ꢁC. Anal. Calc. for C21H18N2O3Sn
(M ¼ 466): C, 54.23; H, 3.90; N, 6.02. Found: C, 54.21; H, 3.91; N,
6.05%. EI-MS, m/z (%): [(C9H8N2O3)Sn(C6H5)2]þ 466 (100.0);
[(C9H8N2O3) Sn(C6H5)]þ 389 (13.1); [(C9H8N2O3)Sn]þ 312 (11.4);
[(C8H6NO2Sn)]þ 268 (3.1); [Sn(C6H5)2]þ 274 (4.1); [SnC6H5]þ 197
2.2.2. Synthesis of dimethyltin(IV) [N0-(3-methoxy-2-oxidobenzyli-
dene)-N-(oxidomethylene)hydrazine] (1)
(39.8); [Sn]þ 120(15.8). FT-IR (cmꢀ1): 1604s, nC]N; 1074m, nNeN
;
589m, nSneO; 450w, nSneN.
1H NMR (ppm): H-3: 6.84 (dd, 1H,
A 250 mL two-necked flask containing 100 mL toluene, equip-
ped with a reflux condenser was charged with N0-(2-hydroxy-3-
methoxybenzylidene)formohydrazide 0.58 g (3.0 mmol), and trie-
thylamine 0.84 mL (6.0 mmol) along with a magnetic bar. To the
solution of triethylammonium salt of the ligand, dimethytin(IV)
dichloride (0.66 g, 3.0 mmol) in dry toluene was added drop wise
with stirring at room temperature. When the solution turned yel-
low, then it was stirred for 5 h at room temperature. The white
precipitates of Et3NHCl formed during the reaction were filtered.
The filtrate was concentrated by rotary evaporator to obtain yellow
solid. The product was recrystallized from CHCl3/n-hexane (4:1)
mixture (Scheme 1c and d).
phenyl, 3JHeH ¼ 7.8), H-4: 6.74 (t, 1H, phenyl, 3JHeH ¼ 7.8), H-5: 7.06
3
(dd, 1H, phenyl, JHeH ¼ 7.8), H-7: 8.64 [(s, 1H, CH]N, 3J(119Sne
1H) ¼ 51 Hz)], H-8: 7.66 (s, 1H, N]OCH), H-9: 3.88 (s, 3H, OCH3), H-
b
: 7.87e7.90 (m, 4H, phenyl), H-g, H-d: 7.40e7.49 (m, 6H, phenyl)
13C NMR (ppm): C-7: 158.0 (HC]N); C-8: 163.7 (CHONH); 163.1,
151.8, 126.1, 117.0, 116.7, 116.2 (PheC): C-9: 56.5 (OCH3), Ca: 138.5,
Cb: 136.2 2J[119Sne13C] ¼ 57 Hz, Cg: 129.0, 3J[119Sne13C] ¼ 98 Hz, Cd:
130.7 4J[119Sne13C] ¼ 18 Hz, 119Sn NMR:
(ppm) ¼ ꢀ338.
d
2.2.5. Di-n-octyltin(IV)[N0-(3-methoxy-2-oxidobenzylidene)-N-(oxi-
domethylene)hydrazine] (4)
Compound 4 was prepared by refluxing N0-(2-hydroxy-3-
methoxybenzylidene)formohydrazide 0.58 g (3.0 mmol) with dio-
ctyltin(IV) oxide 1.09 g (3.0 mmol) in 100 mL dry toluene in 1:1
ratio. The water formed during the reaction was removed by Deane
Stark apparatus. The yellow solution obtained was rotary evapo-
rated under reduced pressure and the solid formed was recrystal-
lized from chloroform and n-hexane (4:1) mixture (Scheme 1e).
Yield 75%, m.p. 70e72 ꢁC. Anal. Calc. for C25H42N2O3Sn
(M ¼ 538): C, 55.88; H, 7.88; N, 5.21 Found: C, 55.91; H, 7.86; N,
5.23%. EI-MS, m/z (%): [(C9H8N2O3)Sn (C8H17)2]þ 538 (39.0);
[(C9H8N2O3)Sn(C8H17)]þ 425 (15.9); [(C9H8N2O3)Sn]þ 312 (100.0);
[(C8H6NO2Sn)]þ 268 (5.9); [Sn]þ 120 (4.3); [C4H9]þ 57 (36.8). FT-IR
Yield 84%, m.p. 140e141 ꢁC. Anal. Calc. for C11H14N2O3Sn
(M ¼ 342): C, 38.75; H, 4.14; N, 8.22, Found: C, 38.78; H, 4.12; N,
8.19%. EI-MS, m/z (%): [(C9H8N2O3)Sn(CH3)2]þ 342 (100.0);
[(C9H8N2O3) Sn(CH3)]þ 327 (43.7); [(C9H8N2O3)Sn]þ 312 (96.0);
[(C8H6NO2Sn)]þ 268 (8.2); [Sn(CH3)2]þ 150 (5.6); [SnCH3]þ 135
(28.3); [Sn]þ 120 (12.8). FT-IR (cmꢀ1): 1623s, nC]N; 1072m, nNeN
;
586m, nSneO; 478w, nSneN. 1H NMR (ppm): H-3: 6.82 (d, 1H, phenyl,
3JHeH ¼ 7.8), H-4: 6.70 (t, 1H, phenyl, 3JHeH ¼ 7.8), H-5: 6.94 (d, 1H,
3
phenyl, JHeH
¼
7.8), H-7: 8.62 [(s, 1H, CH]N, 3J(119Sne
1H) ¼ 46 Hz)], H-8: 7.63 (s, 1H, N]OCH), H-9: 3.87 (s, 3H, OCH3), H-
a
: 0.88 (s, 6H, 2CH3), 2J(119/117Sne1H) ¼ 80, 76 Hz. 13C NMR (ppm):
C-7: 156.9 (HC]N); C-8: 163.7 (CHONH); 163.1, 151.2, 126.0, 116.6,
(cmꢀ1): 1618s, nC]N; 1082m, nNeN; 590m, nSneO; 480w, nSneN 1H
.
115.9, 115.7 (PheC): C-9: 56.1 (OCH3), Ca: 2.61 1J[119/117Sne
NMR (ppm): H-3: 6.79 (dd, 1H, phenyl), H-4: 6.67 (t, 1H, phenyl,
3JHeH ¼ 7.8), H-5: 6.93 (dd,1H, phenyl, 3JHeH ¼ 7.8), H-7: 8.61 [(s,1H,
CH]N, 3J(119Sne1H) ¼ 41 Hz)], H-8: 7.66 (s, 1H, N]OCH), H-9: 3.86
13C] ¼ 657, 627 Hz, 119Sn NMR:
d
(ppm) ¼ ꢀ164.
2.2.3. Diethyltin(IV) [N0-(3-methoxy-2-oxidobenzylidene)-N-(oxido-
methylene)hydrazine] (2)
(s, 3H, OCH3), H-
a
, H-
b
: 1.50e1.57 (m, 8H, 2CH2), H-
g
, H-g0 1.21e
3
1.27 (br, 16H, 2CH2 CH2CH2 CH2), H-d0 0.86 (t, 6H, CH3, JHe
Compound 2 was prepared in the same way as 1, using following
precursors quantities: N0-(2-hydroxy-3-methoxybenzylidene)for-
mohydrazide 0.58 g (3.0 mmol), diethyltin(IV) dichloride 0.74 g
(3.0 mmol), triethylamine 0.84 mL (6.0 mmol) were reacted in 1:1:2
ratio. Solid product was recrystallized from chloroform and n-
hexane (4:1) mixture.
¼ 7.8 ¼ 6.8 Hz), 13C NMR (ppm): C-7: 157.7 (HC]N); C-8: 164.0
H
(CHONH); 162.8, 151.3, 126.0, 116.2, 116.0, 115.8 (PheC): C-9: 56.2
(OCH3), Ca: 23.3, 1J[119/117Sne13C] ¼ 595, 571 Hz, Cb: 24.7 2J[119Sne
13C] ¼ 38 Hz, Cg: 33.4, 3J[119Sne13C] ¼ 86 Hz, Cd: 29.2, C-
a
0: 29.1, C-
b
0: 31.8, C-
g
0: 22.7, C-
d
0: 14.1, 119Sn NMR:
d(ppm) ¼ ꢀ200.
Yield 88%, m.p. 182e183 ꢁC. Anal. Calc. for C13H18N2O3Sn
(M ¼ 370): C, 42.31; H, 4.92; N, 7.59 Found: C, 42.28; H, 4.90; N,
7.56%. EI-MS, m/z (%): [(C9H8N2O3)Sn(C2H5)2]þ 370 (83.0);
[(C9H8N2O3) Sn(C2H5)]þ 341 (61.8); [(C9H8N2O3)Sn]þ 312 (100.0);
[(C8H6NO2Sn)]þ 268 (6.8); [Sn]þ 120 (5.2). FT-IR (cmꢀ1): 1618s,
nC]N; 1068m, nNeN; 582m, nSneO, 472w, nSneN. 1H NMR (ppm): H-
2.2.6. Di-tert-butyltin(IV) [N0-(3-methoxy-2-oxidobenzylidene)-N-
(oxidomethylene)hydrazine] (5)
Compound 5 was prepared in the same way as 1, using following
precursors quantities: N0-(2-hydroxy-3-methoxybenzylidene)for-
mohydrazide 0.58 g (3.0 mmol), di-tert-butyltin(IV) dichloride
0.91 g (3.0 mmol), triethylamine 0.84 mL (6.0 mmol) were reacted
in 1:1:2 ratio. Solid product was recrystallized from chloroform and
n-hexane (4:1) mixture.
3
3
3: 6.79 (dd, 1H, phenyl, JHeH ¼ 7.8), H-4: 6.66 (t, 1H, phenyl, JHe
3
¼ 7.8), H-5: 6.93 (dd, 1H, phenyl, JHeH ¼ 7.8), H-7: 8.64 [(s, 1H,
H
CH]N, 3J(119Sne1H) ¼ 42 Hz)], H-8: 7.68 (s, 1H, N]OCH), H-9:
Yield 80%, m.p. 120e121 ꢁC. Anal. Calc. for C17H26N2O3Sn
(M ¼ 426): C, 48.03; H, 6.16; N, 6.59 Found: C, 48.06; H, 6.20; N,
6.61%. EI-MS, m/z (%): [(C9H8N2O3)Sn(C(CH3)3)2]þ 426 (11.6);
[(C9H8N2O3)Sn]þ 312 (100.0); [(C8H6NO2Sn)]þ 268 (7.3); [Sn]þ 120
3.87 (s, 3H, OCH3), H-
a
: 1.54 (q, 2H, 2CH2), 2J(119Sne1H) ¼ 72 Hz,
3
H-
b
: 1.28 (t, 3H, CH3, JHeH ¼ 7.8). 13C NMR (ppm): C-7: 157.8
(HC]N); C-8: 164.1 (CHONH); 162.9, 151.2, 126.1, 116.2, 115.9,
115.8 (PheC): C-9: 56.2 (OCH3), Ca: 15.7, 1J[119/117Sne13C] ¼ 621,
(5.7); [C4H9]þ 57 (36.7). FT-IR (cmꢀ1): 1616s, nC]N; 1078m, nNeN
;
593 Hz, Cb: 9.2 2J[119Sne13C]
¼
46 Hz, 119Sn NMR:
582m, nSneO; 468w nSneN. 1H NMR (ppm): H-3: 6.80 (dd, 1H, phenyl,
3JHeH ¼ 8.1), H-4: 6.63 (t, 1H, phenyl, 3JHeH ¼ 7.8), H-5: 6.95 (dd, 1H,
d
(ppm) ¼ ꢀ199.7.

62
S. Shujah et al. / Journal of Organometallic Chemistry 741-742 (2013) 59e66
117.8, 116.4, 115.9 (PheC): C-9: 57.1 (OCH3), Ca: 40.9, 1J[119/117Sne
Table 1
(CeSneC) angles (ꢁ) based on NMR parameters of organotin(IV) complexes 1e6.
13C] ¼ 581, 556 Hz, Cb: 29.6, 119Sn NMR:
(ppm) ¼ ꢀ289.
d
Comp. No. Compound 1J(119Sn,13C) (Hz) 2J(119Sn,1H) (Hz) Angle (ꢁ)
2.2.7. n-Butylchlorotin(IV) [N0-(3-methoxy-2-oxidobenzylidene)-N-
(oxidomethylene) hydrazine] (6)
Compound 6 was prepared in the same way as 4, using following
precursors quantities: N0-(2-hydroxy-3-methoxybenzylidene)for-
mohydrazide 0.58 g (3.0 mmol), n-butylchlorotin(IV) dihydroxide
0.74 g (3.0 mmol) were reacted in 1:1 ratio. Solid product was
recrystallized from chloroform and n-hexane (4:1).
1
2
3
4
5
6
Me2SnL
Et2SnL
Ph2SnL
Oct2SnL
t-Bu2SnL
BuClSnL
657
621
e
80
72
e
134.4 130.8
131.2 121.8
e
e
e
e
e
595
581
e
e
134.4
133.1
e
e
e
Yield 77%, m.p. 210e212 ꢁC. Anal. Calc. for C13H17ClN2O3Sn
(M ¼ 194): C, 38.70; H, 4.25; N, 6.94 Found: C, 38.68; H, 4.21; N,
6.91%. EI-MS, m/z (%): [(C9H8N2O3) Sn(C4H9)Cl]þ 404 (43.2);
[(C9H8N2O3)Sn(C4H9)]þ 369 (15.2); [(C9H8N2O3)SnCl]þ 347 (4.7);
[(C9H8N2O3)Sn]þ 312 (100.0); [(C8H6NO2Sn)]þ 268 (9.1); [SnCl]þ
155 (29.7); [Sn]þ 120 (7.9); [C4H9]þ 57 (100.0). FT-IR (cmꢀ1): 1620s,
nC]N; 1082m, nNeN; 578m, nSneO; 470w, nSneN. 1H NMR (ppm): H-3:
3
3
6.80 (dd, 1H, phenyl, JHeH ¼ 7.8), H-4: 6.66 (t, 1H, phenyl, JHe
3
¼ 7.8), H-5: 6.94 (dd, 1H, phenyl, JHeH ¼ 7.8), H-7: 8.61 [(s, 1H,
H
CH]N, 3J(119Sne1H) ¼ 42 Hz)], H-8: 7.66 (s, 1H, N]OCH), H-9: 3.86
(s, 3H, OCH3), H-a: 1.51e1.67 (m, 2H, 2CH2), H-b: 1.51e1.67 (m 2H,
CH2), H-
g
: 1.34 (q, 4H, 2CH2, 3JHeH ¼ 7.2), H-
d
: 0.87 (t, 6H, 2CH3, 3JHe
¼ 7.2), 13C NMR (ppm): C-7: 1567.6 (HC]N); C-8: 162.2 (CHONH);
H
159.5, 151.5, 126.5, 117.4, 117.2, 116.7 (PheC): C-9: 56.4 (OCH3), Ca:
25.6, Cb: 28.5, Cg: 27.4, Cd: 14.2, 119Sn NMR:
d
(ppm) ¼ ꢀ201.
3. Results and discussion
3.1. Spectroscopic studies
In the IR spectrum of ligand (H2L) absorption bands were
observed at 3175, 3385, 1691 and 1612 cmꢀ1 due to the stretching
vibrations of the NeH, OeH, C]O and C]N groups, respectively.
The significant differences in the IR spectra of ligand and complexes
Fig. 1. Molecular structure of compound 1 (molecule a).
3
phenyl, JHeH
¼
7.8), H-7: 8.63 [(s, 1H, CH]N, 3J(119Sne
1H) ¼ 38 Hz)], H-8: 7.72 (s, 1H, N]OCH), H-9: 3.86 (s, 3H, OCH3), H-
(1e6) were the disappearance of n(NeH), n(OeH) and n(C]O)
b
: 1.34 (s, 18H, 2CH3), 3J(119/117Sne1H) ¼ 111, 106 Hz, 13C NMR
(ppm): C-7: 159.5 (HC]N); C-8: 163.9 (CHONH); 162.5, 151.6, 126.3,
Table 3
ꢁ
ꢀ
Selected bond lengths (A) and bond angles ( ) of dimer di-nuclear molecule a and b
of compound 1.
Table 2
Molecule (1) (x ¼ 1)
Molecule (2) (x ¼ 2)
Crystal data and structure refinement parameters for compounds 1 and 3.
Bond lengths
SnxeOx1
Complex No.
1
3
2.231(3)
2.186(3)
2.246(3)
2.585(4)
2.105(4)
2.108(3)
2.555(3)
2.233(2)
2.209(2)
2.246(3)
2.617(2)
2.113(4)
2.117(4)
2.557(3)
SnxeOx2
SnxeNx1
SnxeOx3
SnxeCx10
SnxeCx11
SnxeOx1
Bond angles
Empirical formula
Formula mass
Crystal system
Space group
C22H28N4O6Sn2
681.91
triclinic
P-1
6.688(5)
9.979(8)
18.66(15)
99.06(14)
96.82(13)
99.61(13)
1198.8(16)
2
C21H18N2O3Sn
465.10
monoclinic
P21/n
11.628(5)
11.156(5)
15.388(7)
90.00
108.70(6)
90.00
ꢀ
a (A)
ꢀ
b (A)
ꢀ
c (A)
a
b
g
(ꢁ)
(ꢁ)
(ꢁ)
Ox1eSnxeOx2
Ox1eSnxeNx1
Ox1eSnxeCx10
Ox1eSnxeOx3
Ox2eSnxeNx1
Ox2eSnxeCx10
Ox2eSnxeOx3
Nx1eSnxeCx11
Nx1eSnxeOx3
Cx10eSnxeOx1
Cx11eSnxeOx1
Ox1eSnxeOx3
Ox1eSnxeCx11
Ox2eSnxeCx11
Nx1eSnxeCx10
Nx1eSnxeOx1
Cx10eSnxeCx11
Cx10eSnxeOx3
Ox1eSnxeOx1
Cx11eSnxeOx3
152.72(10)
81.16(10)
92.85(13)
135.97(9)
71.63(10)
92.65(13)
71.32(9)
97.81(12)
142.75(10)
83.02(12)
84.01(12)
62.29(9)
91.65(13)
90.11(13)
97.55(13)
154.87(10)
164.48(14)
80.44(12)
73.73(9)
151.89(10)
80.59(10)
90.94(12)
136.18(9)
71.80(11)
89.29(12)
71.83(9)
93.55(12)
142.97(9)
83.07(12)
83.98(12)
62.71(8)
93.71(12)
90.11(13)
97.55(13)
154.87(10)
164.48(14)
80.44(12)
73.48(9)
3
ꢀ
V (A )
1890.59(15)
4
Block
Z
Crystal habit
size (mm)
T (K)
Block
0.49 ꢂ 0.36 ꢂ 0.11 0.21 ꢂ 0.19 ꢂ 0.14
100 (1)
1.889
21.29
672
10,689
5645
100 (1)
1.634
13.75
928
16,898
4693
r
(g cmꢀ3
)
m
(Mo Ka) (mmꢀ1
)
F(000)
Total reflections
Independent reflections
For (Fo ꢃ 4.0 (Fo))
R(F) ¼ (jjFoj ꢀ jFcjj)/jFoj
s
5042
0.0300
3929
0.0295
For Fo > 4.0
s (Fo)
wR(F2) ¼ [[w(Fo2 ꢀ Fc2)2]/[w(F2o)2]]1/2 0.1011
0.0700
1.048
2.60e29.12
4693/0/316
Goodness-of-fit
1.183
2.56e29.51
5645/0/419
q
range (ꢁ)
Data/restrictions/params
86.01(11)
86.08(11)

S. Shujah et al. / Journal of Organometallic Chemistry 741-742 (2013) 59e66
63
480 cmꢀ1 indicate the presence of SneO and SneN bonds,
respectively [15].
The 1H NMR signals at 10.10, 11.66 and 8.66 ppm in the ligand
are due to eOH, CHO and eNHN] protons. In the diorgnaotin(IV)
complexes (1e6), all these signals were disappeared due to the
conversion of amido form of the ligand to imine form (Scheme 1b)
and subsequent deprotonation. The down field shift in the eCH]N
proton resonance to 8.61e8.64 ppm with 3J (119Sn, 1H) coupling
constant of 38e51 Hz confirmed the shift of electron density from
azomethine nitrogen to Sn atom. This coordination was further
confirmed by the single crystal X-ray structures of compounds 1
and 3. No significant shift in the signal of methoxy protons was
observed because of the monomeric nature of all complexes (1e6)
in solution. This observation is in marked contrast to the solid state
structure in which the methoxy oxygen is coordinated to the tin
atom (single crystal structure of complex 1). All the other protons of
the ligand and the R groups bonded to Sn atom were appeared in
their expected regions. The 2J(119Sn, 1H) coupling constant of
complex 1 (80 Hz) and complex 2 (72 Hz) correspond to CeSneC
angel of 130.8ꢁ and 121.8ꢁ, calculated using Lockhart’s equation
(Table 1),
q
¼ 0.0161 [2J]2 e 1.32 [2J] þ 133.4, support the penta
coordinated Sn atom in non-coordinating solvents [16].
The characteristic resonance peaks in the 13C NMR spectra of
complexes were recorded in CDCl3. In the 13C NMR spectrum of the
ligand, C-7 (HC]N) and C-8 (CHONH) were appeared at 143.3 and
165.2 ppm, respectively. The complexes showed a down field shift
of phenyl carbon resonances, especially C-1 due to the formation of
SneO bond [17]. The 1J [119Sne13C] coupling constants were used to
establish the coordination around tin in solution [18]. The calcu-
lated coupling constants (556e657 Hz) further support the idea of
penta coordinated Sn atom in solutions for complexes 1e6 [19]. The
signals for rest of the carbons were observed as expected.
The 119Sn NMR resonances for dimethyl, diethyl, di-tert-butyl
and di-octyl complexes were observed at ꢀ164, ꢀ200, ꢀ289
and ꢀ200 ppm, respectively. For diphenyl complex the anisotropic
shielding effects and pi interactions caused the signal to appear
at ꢀ338 ppm. The 119Sn NMR chemical shifts for all the complexes
(1e6) demonstrated the presence of five coordinate tin(IV) cores
[12,20e22].
Fig. 2. (a) Supramolecular single wavy layer of compound 1 mediated by H13/N22
ꢀ
ꢀ
ꢀ
ꢀ
(2.643 A), O22/H17 (2.448 A),
p/H17 (2.777 A) and H28/N12 (2.594 A) intermo-
lecular non-covalent interactions. (b) Two wavy layers are connected through
(3.282 A) interactions (blue dotted lines). (For interpretation of the references to color
p/p
ꢀ
in this figure legend, the reader is referred to the web version of this article.)
bands due to deprotonation and enolization of the ligand, thus
suggest the coordination of phenolic and enolic oxygens to the
diorganotin(IV) moiety [11]. The
n(C]N) band is shifted to lower
frequency indicating the coordination of azomethine nitrogen to tin
center [12]. The band at 1055 cmꢀ1 due to
n(NeN) is shifted to
higher frequencies at 1068e1082 cmꢀ1 in the spectra of organo-
tin(IV) complexes (1e6). The increase in the frequency of this band
is attributed to an increase in bond length and decrease in repulsion
of the lone pairs of electrons on the nitrogen atoms [13,14]. The IR
bands observed in the regions of 578e590 cmꢀ1 and 450e
3.2. X-ray crystal structure of complexes (1and 3)
The asymmetric unit of centrosymmetric dinuclear complex (1)
consists of half of the dimer. The molecular structure and atomic
numbering scheme for one of the di-nuclear molecule is given in
Fig.1. The crystallographic data, selected bond lengths and angles of
the dinuclear molecules ‘a’ and ‘b’ of complex 1 are listed in Tables 2
and 3. Each molecule possesses a dinuclear centrosymmetric
Table 4
ꢁ
ꢀ
Selected bond lengths (A) and bond angles ( ) of complex 3.
Bond lengths
SneO(1)
SneO(2)
SneN(1)
SneC(10)
2.067(17)
2.124(18)
2.158(2)
2.120(2)
SneC(16)
N(1)eN(2)
N(1)eC(7)
N(2)eC(8)
2.119(2)
1.410(3)
1.291(3)
1.290(4)
Bond angles
O(1)eSneO(2)
O(1)eSneN(1)
O(1)eSneC(10)
O(1)eSneC(16)
O(2)eSneN(1)
O(2)eSneC(10)
O(2)eSneC(16)
N(1)eSneC(10)
N(1)eSneC(16)
157.84(8)
84.04(7)
96.99(8)
94.38(8)
74.18(8)
95.03(8)
93.90(8)
112.28(9)
122.43(9)
C(10)eSneC(16)
SneO(1)eC(1)
SneO(2)eC(8)
SneN(1)eN(2)
SneN(1)eC(7)
SneC(10)eC(11)
SneC(10)eC(15)
SneC(16)eC(17)
SneC(16)eC(21)
124.93(9)
132.92(15)
112.53(18)
115.64(16)
128.39(16)
120.20(2)
120.00(2)
120.52(18)
120.53(18)
Fig. 3. Molecular structure of compound 3.

64
S. Shujah et al. / Journal of Organometallic Chemistry 741-742 (2013) 59e66
ꢀ
ꢀ
Fig. 4. Two Y-shaped chains connected together via H9ꢂ/
p
(2.813 A) and H19/
p
(2.864 A) interactions. Hydrogens of phenyl rings not involve in non-covalent interactions are
omitted for clarity.
dimeric structure with a four membered planar Sn2O2 ring. The Sne
O4NC2 core in molecule a and b is O(x1)eSnxeO(x3) 62.29(9)ꢁ and
62.71(8)ꢁ, respectively, whereas the other angles are N(x1)eSnxe
O(x2) {71.63(10)ꢁ and 71.80(11)ꢁ], O(x2)eSnxeO(x3) {71.32(9)ꢁ and
71.83(9)ꢁ}, O(x1)eSnxeO(x1) {73.73(9)ꢁ and 73.48(9)o} and O(x1)e
SnxeN(x1) {81.16(10)ꢁ and 85.59(10)ꢁ}. The SnxeO(x1) {2.231(3)
ꢀ
O bond distances are 2.231(3) and 2.555(3) A for molecule a and
ꢀ
2.233(2) and 2.557(3) A for molecule b. Each dinuclear molecule
contains two formula unit bridged together through phenolic and
methoxy oxygen atoms. The Sn(x) atom and O(x1), C(x1), C(x6),
C(x7), N(x1) atoms form a six membered ring, while Sn, O(x2), C(x8),
N(x1), N(x2) and Sn(x), O(x1), C(x1), C(x2), O(x3) atoms form five
membered rings. Each (CH3)2Sn(IV) moiety is bonded to four oxygen
atoms and a nitrogen forming O4NC2 core around the tin atom. The
ligand is non-planar probably due to the steric requirements of the
five- and six-membered rings. The geometry around the Sn atom
can be characterized as a distorted pentagonal bipyramidal with the
methyl groups in apical positions with C(x10)eSnxeC(x11) angle of
164.48(14)ꢁ. The smallest angle within the plane formed by the
ꢀ
and 2.233(2) A} and SnxeO(2) {2.186(3) and 2.209(2)} bond lengths
ꢀ
are less than the sum of van der Waals radii of the Sn and O (3.68 A).
The SnxeN(x1) interaction is strong enough to be called as bond
ꢀ
because the bond distance (2.246(3) A) is well below the sum of the
ꢀ
van der Waals radii of the Sn and N (3.75 A). Packing diagram offer a
wavy supramolecular structure to compound 1 mediated by
ꢀ
ꢀ
ꢀ
H13/N22 (2.643 A), O22/H17 (2.448 A),
p/H17 (2.777 A) and
ꢀ
H28/N12 (2.594 A) intermolecular non-covalent interactions
(Fig. 2a). The adjacent wavy layers are connected to one another via
ꢀ
p/p
(3.282 A) interactions (Fig. 2b). These interactions are com-
parable with the literature values [23e29].
The single-crystal X-ray diffraction (XRD) study of complex 3
shows its mononuclear nature which is in marked contrast to the
complex 1 (Fig. 3). This may be due to the bulky phenyl groups that
Table 5
Antileishmanial activityaed of ligand and its organotin(IV)
complexes.
Compound
IC50
(m
g/mL) ꢄ S.D
H2L
(1)
(2)
(3)
(4)
(5)
(6)
21.8 ꢄ 0.01
3.06 ꢄ 0.02
6.41 ꢄ 0.06
2.03 ꢄ 0.03
8.25 ꢄ 0.11
1.26 ꢄ 0.02
3.91 ꢄ 0.03
a
Test organism: Leishmania major (DESTO).
Standard drug: Amphotericin B (
Incubation period: 72 h.
b
c
m
g/mL) ꢄ S.D ¼ 0.50 ꢄ 0.02.
d
Incubation temperature: 22 ꢄ 1 ꢁC.
Table 6
Antiurease activity of ligand and its organotin(IV) complexes.aed
Compound No.
% Inhibition
H2L
(1)
(2)
(3)
(4)
(5)
(6)
48.8
62.6
18.1
35.5
42.6
36.1
30.5
IC50 ꢄ S.D [
m
M]
e
101.0 ꢄ 2.16
e
e
e
e
e
a
Sample Concentration [mM] 0.5.
b
c
Standard: thiourea, IC50 ꢄ SEM [ M], 21.0 ꢄ 0.11.
m
ꢀ
Fig. 5. (a) Showing point of contact (
p/
p
3.385 A) between two differently oriented
Proposed implications of inhibitor: acute ulcer.
d
Y-shaped cleft units. (b) Overall view of two Y-shaped cleft units.
IC50 reported for those compounds whose % inhibition is more than 55%.

S. Shujah et al. / Journal of Organometallic Chemistry 741-742 (2013) 59e66
65
with the large covalent radius of tin(IV). The nitrogen (SneN1:
2.158(2) E) and the carbon atoms (SneC10: 2.120(17) and SneC16:
2.119(18) E) occupy the equatorial plane, whereas the oxygen atoms
(SneO1: 2.067(2) and SneO2: 2.124(2) E) are in axial positions,
with O1eSneO2 bond angle of 157.84(8)ꢁ. The Sn(1)eN(1) distance
(2.158(2) E) is close to the sum of the non-polar covalent radii
(2.15 E), but is considerably less than the sum of the van der Waals
radii (3.75 E) indicating a strong tinenitrogen interaction (Table 4).
1D Y-shaped chain (Fig. 4) is formed by the interactions of H9ꢂ
ꢀ
with
p
electronic cloud of N2CHO moiety [H9ꢂ/
p
(2.813 A)]. Two
neighboring Y-shaped chains are cleft together via edge-to-face
ꢀ
CH/
p interactions (2.864 A). These two cleft chains are held
ꢀ
together with next similar unit by
p/p (3.385 A) contacts as
shown in Fig. 5a and b, thus generating 1D microporous channels
when viewed along b-axis (Fig. 6). Such material may find appli-
cations in separation, storage, transport, and catalysis [3].
4. Biological activities
Fig. 6. Microporous channels in the structure of compound 3 when viewed along b-
axis.
4.1. Antileishmanial activity
hinder the coordination of methoxy oxygen to the Sn atom. Here,
the tin center is coordinated by five donor atoms, two oxygens and
a nitrogen from the ligand, and two carbon of the phenyl groups.
The calculated s of 0.5 suggests that geometry is a midway between
square-pyramidal and trigonal bipyramidal geometry. The distor-
The ligand and complexes (1e6) were screened against the
pathogenic Leishmania major using Amphotericin B (0.50 mg/mL)
as standard drug (Table 5). All the studied organotin(IV) derivatives
were found more active than corresponding free ligand which
imply the vital role of Sn atom in the antileishmanial activity. The
tion is mainly due to the rigidity of the chelating rings together
Fig. 7. Antibacterial activity of H2L and its organotin(IV) derivatives against various bacteria.
Fig. 8. Antifungal activity of H2L and its organotin(IV) derivatives against various fungi.

66
S. Shujah et al. / Journal of Organometallic Chemistry 741-742 (2013) 59e66
tert-dibutyltin(IV) and diphenyltin(IV) derivatives (5 and 3) showed
comparable activity to the standard drug. This can be attributed to
their high lipophilic character. Two factors, planarity and low mo-
lecular weight, which facilitate smooth diffusion are presumably
turn into high activity of the diphenyltin(IV) complex (3). The same
factor seems responsible for the lowest activity of the dioctyltin(IV)
complex (4).
each Sn atom in pentagonal bipyramidal environment (1). This dual
nature can be attributed to the steric factor in the former. Packing
diagram offered a wavy supramolecular layer structure to com-
ꢀ
ꢀ
pound 1 mediated by H13/N22 (2.643 A), O22/H17 (2.448 A),
ꢀ
ꢀ
p
/H17 (2.777 A) and H28/N12 (2.594 A) intermolecular non-
covalent interactions. For compound 3, 1D Y-shaped chain were
formed by H9ꢂ/ interactions. Two neighboring Y-shaped chains
were cleft together via edge-to-face CH/
The combination of various such cleft units via
p
ꢀ
p
interactions (2.864 A).
ꢀ
4.2. Antiurease activity
p/p (3.385 A)
contacts generated 1D microporous channels when viewed along b-
axis. Such material may find applications in separation, storage,
transport, and catalysis. These complexes presented good anti-
leishmanial, antiurease, antibacterial and antifungal activities and
the significance of Snwas clearly visible. Compound 3 and 5 have the
potential to be used as antileishmanial agents due to their compa-
rable activity with standard antileishmanial drug Amphotericin B.
In vitro antiurease activity at 0.5 mM concentration against jack
bean urease was undertaken for free ligand and its complexes ac-
cording to the literature protocol [30], using thiourea as the stan-
dard inhibitor having an IC50 ꢄ S.D [ M] value of 21 ꢄ0.01 (Table 6).
m
As evident from the results, the parent ligand and its organotin(IV)
derivatives are moderate urease inhibitors except compound 1
which shows promising activity with IC50 ꢄ S.D [
mM] value of
101 ꢄ 2.16. This is probably due to its ability to establish secondary
Appendix A. Supplementary material
interactions with the active site of enzyme.
CCDC 688811 and 698810 contain the supplementary crystal-
lographic data for this paper. These data can be obtained free of
charge from The Cambridge Crystallographic Data Centre via www.
ccdc.cam.ac.uk/data_request/cif.
4.3. Antibacterial activity
The parent ligand and complexes (1e6) also show their inhibi-
tory effect against two gram-positive (Bacillus subtilis, Staphylo-
coccus aureus) and four gram-negative bacteria (Escherichia coli,
Shigella flexenari, Pseudomonas aeruginosa, Salmonella typhi), using
Imipenem (C12H17N3O4S) as a standard drug for comparison (Fig. 7).
In general, the diorganotin(IV) derivatives were found more active
against gram-positive bacteria than gram negative bacteria. This
fact can be attributed to ease of permeation of the complexes in the
formers owing to the simplicity of the cell membrane structure.
The most probable reason for high antibacterial activity of
organotin derivatives than the parent ligand is due to the reduction
in the polarity of the Sn(IV) atom upon complexation with the
ligand. This reduction in polarity is because of the partial sharing of
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electrons delocalization within the whole chelating ring. As a
consequence the lipophilic nature of the central Sn atom increases,
which in turn enhances the permeation of the complexes through
the lipid layer of the cell membrane.
4.4. Antifungal activity
The % inhibition of the synthesized compounds was studied
in vitro against six human pathogenic fungal strains including
yeasts (Candida albicans ATCC 2192, Candida glabrata ATCC 90030),
dermatophytes (Microsporum canis ATCC 9865, Trichphyton long-
ifusus ATCC 22397), opportunistic molds (Aspergillus flavus ATCC
1030 and Fusarium solani ATCC 11712) using the agar tube dilution
test (Fig. 8). The ligand was found active only against Aspergillus
flavis with inhibitory action almost equal to the standard drug
Amphotericin B. Compound 3 was highly active against Candida
glaberata, and fairly active against C. albicans. Trichophyton long-
ifusus was the only strain resistive to all complexes.
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In summing up, six new diorganotin(IV) derivatives of N0-(2-
hydroxy-3-methoxybenzylidene)formohydrazide ligand were syn-
thesized and characterized. Based on X-ray single crystal analysis,
these compounds were either mononuclear in which Sn atom is in
distorted trigonal bipyramidal geometry (3) or homobimetallic with
[29] C. Janiak, T.G. Scharmann, Polyhedron 22 (2003) 1123e1133.
[30] M. Serwar, T. Akhtar, S. Hameed, K.M. Khan, ARKIVOC vii (2009) 210e221.