Synthesis, spectral and antibacterial studies on Ni(II) and Zn(II) complexes involving N -furfuryl- N -isopropyldithiocarbamate (f iprdtc) and Lewis bases: X-ray structure of [Ni(fiprdtc) (NCS)(PPh 3)]

Article abstract of DOI:10.1080/17415993.2012.751989

[Ni(fⁱprdtc)₂] (1), [Ni(fⁱprdtc)(PPh ₃)(NCS)] (2), [Ni(fⁱprdtc)(PPh₃) ₂]ClO₄ (3), [Zn(fⁱprdtc)₂] (4), [Zn(fⁱprdtc)₂ (1,10-phen)] (5) and [Zn(f ⁱprdtc)₂ (2,2′-bipy)] (6) (f ⁱprdtc=N- furfuryl-N-isopropyldithio- carbamate, 1,10-phen=1,10-phenanthroline and 2,2′-bipy=2,2′-bipyridine) complexes were prepared and characterized by elemental analysis, electronic, IR and NMR spectra and the structure of 2 was determined by single-crystal X-ray crystallography. UV-Vis spectral data of 1-3 are consistent with the formation of square planar complexes. IR spectra of the complexes show the contribution of the thioureide form to the structure. A single-crystal X-ray structural analysis of 2 proved four-coordinated nickel in a distorted square planar arrangement with a S₂PN donor set. Significant asymmetry in Ni-S bond distances was observed in [Ni S1=2.1655(8); Ni S2=2.2120(8) A]. This observation clearly supports the less effective trans of SCN^- over PPh₃. The observed shielding in N ¹³CS₂ chemical shifts of heteroleptic nickel complexes 2 and 3 when compared with homoleptic nickel complex 1 indicates the effect of PPh₃ on the mesomeric drift of electron density toward nickel through the thioureide C N bond. The N¹³CS₂ chemical shift of 5 and 6 are additionally deshielded compared with 4 owing to the increase in coordination number. Complexes were screened for in vitro antibacterial activity and significant activity has been found.

Full text of DOI:10.1080/17415993.2012.751989

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Synthesis, spectral and antibacterial
studies on Ni(II) and Zn(II)
complexes involving N-furfuryl-N-
isopropyldithiocarbamate (f iprdtc)
and Lewis bases: X-ray structure of
[Ni(f iprdtc)(NCS)(PPh3)]
Palanisamy Jamuna Rania, Subbiah Thirumarana & Samuele
Ciattinib
a Department of Chemistry, Annamalai University, Annamalainagar
608 002, Tamil Nadu, India
b Centro di Cristallografia Strutturale, Polo Scientifio di Sesto
Fiorentino, Via della Lastruccia No. 3, 50019 Sesto Fiorentino,
Firenze, Italy
Published online: 10 Jan 2013.
To cite this article: Palanisamy Jamuna Rani, Subbiah Thirumaran & Samuele Ciattini (2014)
Synthesis, spectral and antibacterial studies on Ni(II) and Zn(II) complexes involving N-furfuryl-N-
isopropyldithiocarbamate (f iprdtc) and Lewis bases: X-ray structure of [Ni(f iprdtc)(NCS)(PPh3)],
Journal of Sulfur Chemistry, 35:1, 106-116, DOI: 10.1080/17415993.2012.751989
To link to this article: http://dx.doi.org/10.1080/17415993.2012.751989
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Journal of Sulfur Chemistry, 2014
Vol. 35, No. 1, 106–116, http://dx.doi.org/10.1080/17415993.2012.751989
Synthesis, spectral and antibacterial studies on Ni(II) and Zn(II)
complexes involving N-furfuryl-N-isopropyldithiocarbamate
(fiprdtc) and Lewis bases: X-ray structure of
[Ni(fiprdtc)(NCS)(PPh3)]
Palanisamy Jamuna Rania, Subbiah Thirumarana* and Samuele Ciattinib
b
aDepartment of Chemistry, Annamalai University, Annamalainagar 608 002, Tamil Nadu, India; Centro
di Cristallografia Strutturale, Polo Scientifio di Sesto Fiorentino, Via della Lastruccia No. 3, 50019 Sesto
Fiorentino, Firenze, Italy
(Received 23 September 2012; final version received 18 November 2012)
[Ni(fiprdtc)2] (1), [Ni(fiprdtc)(PPh3)(NCS)] (2), [Ni(fiprdtc)(PPh3)2]ClO4 (3), [Zn(fiprdtc)2] (4),
[Zn(fiprdtc)2(1,10-phen)] (5) and [Zn(fiprdtc)2(2,2ꢀ-bipy)] (6) (fiprdtc = N-furfuryl-N-isopropyldithio-
carbamate, 1,10-phen = 1,10-phenanthroline and 2,2ꢀ-bipy = 2,2ꢀ-bipyridine) complexes were prepared
and characterized by elemental analysis, electronic, IR and NMR spectra and the structure of 2 was
determined by single-crystal X-ray crystallography. UV–Vis spectral data of 1–3 are consistent with the
formation of square planar complexes. IR spectra of the complexes show the contribution of the thioureide
form to the structure. A single-crystal X-ray structural analysis of 2 proved four-coordinated nickel in a
distorted square planar arrangement with a S2PN donor set. Significant asymmetry in Ni–S bond distances
−
−
was observed in [Ni S1 = 2.1655(8); Ni S2 = 2.2120(8)Å]. This observation clearly supports the less
effective trans of SCN− over PPh3. The observed shielding in N13CS2 chemical shifts of heteroleptic
nickel complexes 2 and 3 when compared with homoleptic nickel complex 1 indicates the effect of PPh3
on the mesomeric drift of electron density toward nickel through the thioureide C N bond. The N13CS2
chemical shift of 5 and 6 are additionally deshielded compared with 4 owing to the increase in coordination
−
number. Complexes were screened for in vitro antibacterial activity and significant activity has been found.
Keywords: divalent metal dithiocarbamate; spectroscopic characterization; single-crystal X-ray analysis;
antibacterial activity
*Corresponding author. Email: sthirumaran@yahoo.com
© 2013 Taylor & Francis

Journal of Sulfur Chemistry 107
1. Introduction
Dithiocarbamates and their complexes of various metal ions are used as fungicides (1), antioxi-
dants (2), analytical chemistry (3, 4), organic synthesis (5), polymer photostabilizers (6), and as
single-source precursors for the preparation of metal sulfide nanoparticles (7, 8). The phosphine
ligands because of their σ-donor and π-acceptor properties, larger steric demands, electronic and
energetic factors have been useful components in the metal complexes which provide interesting
chemical reactivity and physical properties, such as the conversion of light to chemical energies
and acting as chemical sensors and probes in biological imaging (9–12). Nickel(II) dithiocarba-
mate complexes react with phosphines to form complexes with the NiS2P2 chromophore (13).
Complexes containing the NiXS2P chromophore have shown catalytic activity, especially for
oligomerization of olefins (14–16). In the dithiocarbamates, the R1, R2 groups in the S2CNR1R2
moiety influence the stability, structure, physico-chemical and biological properties of the com-
plexes (17). Zinc(II) dithiocarbamate complexes are used in the world-wide rubber vulcanization
process (18–21). Zinc(II) complexes are partially unsaturated in dithiocarbamate complexes and
can therefore form adducts with nitrogenous bases (13). Many dithiocarbamate salts and com-
plexes have shown antibacterial activity (22–24). Suitable changes in substituents at the nitrogen of
dithiocarbamate can markedly affect the properties of the complexes. The aim of the present work
was to study the antibacterial activity of metal dithiocarbamate complexes containing furfuryl
group. We report synthesis, spectral and antibacterial studies on complexes involving N-furfuryl-
N-isopropyldithiocarbamate, Lewis bases, Ni(II) and Zn(II) and single-crystal X-ray structure of
[Ni(fiprdtc)(NCS)(PPh3)].
Scheme 1. Preparation of 1 and 4.
2. Results and discussion
Homoleptic and heteroleptic complexes were prepared according to the synthetic procedure
shown in Schemes 1–3. Furfuraldehyde was condensed with isopropylamine to form the imine.
Sodium borohydride reduction of imine in methanol–dichloromethane afforded secondary amine

108 P. Jamuna Rani et al.
Scheme 2. Preparation of 2 and 3.
Scheme 3. Preparation of 5 and 6.
as yellow oil. Complexes 1 and 4 were prepared from secondary amine in EtOH by reac-
tion with carbon disulfide and corresponding metal salt in water. The reaction under continued
reflux (3 h) between [Ni(fiprdtc)2], NiCl2, NH4SCN and PPh3 yielded [Ni(fiprdtc)(NCS)(PPh3)].
[Ni(fiprdtc)(PPh3)2]ClO4 complex was prepared by refluxing [Ni(fiprdtc)2], NiCl2, NaClO4 and
PPh3 in chloroform–methanol (3:2, 50 ml) mixture. The reaction of complex 4 with nitrogen
donor ligands (1,10-phen, 2,2ꢀ-bipy) yielded 5 and 6. The complexes are quite stable at ambient
conditions. They are soluble in chloroform, dichloromethane and acetonitrile and insoluble in
ethanol, methanol and water.

Journal of Sulfur Chemistry 109
2.1. IR spectra
Infrared spectra of 1–6 show νC N(thioureide) bands in the region 1498–1423 cm−1 indicating
−
the partial double bond character (25). In the case of heteroleptic Ni(II) complexes, the νC
−
N
values are found to be larger than those of the parent Ni(II) dithiocarbamate, due to the presence
of π-accepting phosphine (26). Adducts 5 and 6 exhibit lower νC
values compared to 4, due
−
N
to the change in coordination geometry from tetrahedral to octahedral (27). The νC S stretching
−
frequenciesareobservedintheregion1018–1011 cm−1 withoutanysplitting, supportingbidentate
coordination of the dithiocarbamate ligand (28).
2.2. 1H NMR spectra
1H NMR spectrum of N-furfuryl-N-isopropylamine shows a singlet at 4.82 ppm and a multiplet
at 2.78–2.84 ppm due to methylene protons of furfuryl group and methine proton of isopropyl
group, respectively. In the case of complexes, methylene (4.71–5.09 ppm) and methane (4.44–
5.54 ppm) protons are greatly deshielded in 1–6 due to complexation. The methylene and methine
protons adjacent to nitrogen of fiprdtc in heteroleptic complexes 2 and 3 are observed as four
−
broad signals. This is due to the C N bond rotation as observed in phosphine complexes (29).
2.3. 13C NMR spectra
Complexes 1–6 show N13CS2 signals in the region 200.8–208.9 ppm, indicating contribution
of double bond character to a formally single N–C bond in the dithiocarbamate. The complex
4 of zinc owing to a d10 electronic configuration, the δ (N13CS2) value is shifted to low field
compared to complex 1 (30). The presence of π-acid (triphenylphosphine) in 2 (205.2 ppm)
and 3 (200.8 ppm) increases the mesomeric drift of electron density from the dithiocarbamate
moiety toward the metal center contributes the upfield shift from the chemical shift value of
parent complex 1 (208.9 ppm). Additional coordination of nitrogen donors to 4 yields a decrease
of nitrogen–carbon partial double bond character and, as a result of that, the N13CS2 carbon of
nitrogen donor adducts 5 and 6 are additionally deshielded compared with parent complex 4.
2.4. Electronic spectral studies
In the electronic spectra of complex 1 two d–d transition bands are observed at 483 and 623 nm
2
2
2
2
2
corresponding to the dxy → dx −y and dz → dx −y transitions, respectively, supporting a square
planar structure (31). The bands at 481 and 482 nm for 2 and 3, respectively, can be attributed to
2
2
2
dz /dxy → dx −y metal orbital transitions and their positions and intensities are clearly indicative
of a square planar environment for the metal ion in the heteroleptic complexes 2 and 3 (32). No
transition was observed in the visible region for 4–6, consistent with the d10 configuration of the
zinc (33).
2.5. Crystallographic analysis of 2
The structure of 2 was confirmed by a single-crystal X-ray analysis. Details of the crystal data
and structure refinement parameters for 2 are summarized in Table 1. Selected bond distances
and angles are listed in Table 2. The ORTEP diagram is shown in Figure 1. X-ray structure
analysis confirmed four coordinated nickel in a distorted square planar arrangement. Thus, the
central nickel atom is coordinated by two sulfur atoms from fiprdtc, by one phosphorus atom
from PPh3 and by one nitrogen atom from NCS−. The geometry adopted by this complex is

110 P. Jamuna Rani et al.
Table 1. Crystal data, data collection and refinement parameters for [Ni(fiprdtc)
(NCS)(PPh3)].
Empirical formula
C28H27N2OPS3Ni
FW
593.38
Crystal dimensions (mm)
0.4 × 0.3 × 0.2
Crystal system
Space group
a (Å)
Monoclinic
P21/c
8.814(1)
b (Å)
19.693(1)
c (Å)
17.142(1)
90.00
101.596(3)
90.00
2914.7(4)
4
1.352
0.959
α (◦)
β (◦)
γ (◦)
V(Å3)
Z
Dc (g cm−3
)
μ (cm−1
F(000)
λ (Å)
)
1232
MoKα (0.71069)
4.22-29.16
θ range (◦)
Index ranges
−11 ≤ h ≤ 11, −24 ≤ k ≤ 24, −23 ≤ l ≤ 17
Reflections collected
Observed reflections Io > 2σ (I)
Number of parameters refined
Final R, Rw(obs, data)
GOOF
6787
4538
325
0.0803, 0.1314
1.008
Table 2. Selected bond distances (Å) and bond angles (◦) for 2.
Bond angle (◦)
Bond distance (Å)
Ni–N1
Ni–P1
Ni–S1
1.862(3)
N1–Ni–S1
172.75(8)
91.33(8)
95.90(3)
93.78(8)
78.97(3)
174.51(3)
87.16(11)
85.94(10)
107.84(16)
2.1931(8)
2.1655(8)
2.2120(8)
1.727(3)
1.717(3)
1.307(4)
1.606(4)
1.139(4)
N1–Ni–P1
S1–Ni–P1
N1–Ni–S2
S1–Ni–S2
P–Ni–S2
C20–S1–Ni
C20–S2–Ni
S1–C20–S2
Ni–S2
S1–C20
S2–C20
C20–N2
C19–S3
N1–C19
characterized using τ4-descriptor for four coordination ions suggested byYang et al. (34). The τ4
value of this complex is 0.09 which indicates that the coordination geometry is seesaw structure;
Ni–S bond distances [Ni–S1 = 2.1655(8); Ni–S2 = 2.2120(8)Å] are significantly different, due
to the different trans influences exerted by triphenylphosphine and NCS−. PPh3 being a good
π-acceptor has a greater trans influence and hence the Ni–S bond trans to P is longer than the
one trans to NCS anion.
The C–S [(S1–C20 = 1.727(3); S2–C20 = 1.717(3)Å] bond lengths of the NCS2 fragment are
nearly equal and are much shorter than typical C–S single bonds (ca. 1.81Å). The C20–N2 bond
distance of 1.307(4)Å is shorter than normal Csp2–Nsp2 bond length (ca. 1.35Å). This behavior
indicates that the electron density is delocalized over the entire NCS2 moiety. Similar behavior is
observed for related nickel complexes (13).
The Ni–N distance [1.862(3)Å] is significantly shorter than the distance reported for the octa-
hedral [Ni(en)2(NCS)2] (2.15Å) (35), which shows the effective bonding between the nickel atom
and NCS−. Ni–N1–C19 (thiocyanate) angle [170.9(3)◦] indicates deviation from the linearity and
is due to the steric effect of the adjacent bulky triphenyl phosphine ligand. But N–C–S angle

Journal of Sulfur Chemistry 111
Figure 1. ORTEP diagram of 2.
[179.7(3)◦] shows linearity of the thiocyanate group. The P–Ni–N angle is found to be 91.33(8)◦,
which supports the planarity of the molecule.
2.6. Antibacterial activity
The disc diffusion assay was conducted to determine if the tested compounds could inhibit the
growth of bacteria. The antibacterial activity of the complexes has been screened against Staphy-
lococcus aureus, Escherichia coli, Pseudomonas aeruginosa and Klebsiella pneumoniae. The
results are given in Table 3. Complex 4 exhibits more activity against S. aureus and K. pneu-
moniae. Its adducts 5 and 6 show less activity against all tested bacteria except that S. aureus.
Table 3. Antibacterial activity (diameter of inhibition zone (cm)) of complexes 1–6 against four different bacterial
pathogens.
Complex
Chloramphenicol
Disc content
Selected bacteria
(100 μg)
1
2
3
4
5
6
(μg/disc)
Staphylococcus aureus
Escherichia coli
2.0
2.0
1.8
2.0
1.0
1.0
0.2
0.8
0.5
0.5
0.2
0.8
1.0
1.0
0.1
0.2
0.4
0.4
0.1
0.3
0.2
0.5
0.2
0.2
0.5
2.0
0.3
0.5
1.0
3.0
0.2
0.5
0.5
0.5
0.5
1.8
1.0
1.0
0.2
0.3
0.5
0.5
0.5
0.5
0.8
1.0
0.5
0.5
0.5
1.0
0.8
0.8
200
400
200
400
200
400
200
400
Pseudomonas aeruginosa
Klebsiella pneumoniae

112 P. Jamuna Rani et al.
Complex 3 is more toxic against P. aeruginosa. Generally, all nickel complexes show less activity
against all tested bacteria.
3. Conclusions
New complexes [Ni(dtc)2], [Ni(dtc)(NCS)(PPh3)], [Ni(dtc)(PPh3)2]ClO4, [Zn(dtc)2], [Zn(dtc)2
(1,10-phen)] and [Zn(dtc)2(2,2ꢀ-bipy)] (dtc = fiprdtc) have been synthesized and characterized
by elemental analysis and spectroscopic studies. The spectral studies on complexes 1–3 indi-
cate that the central metal atom is in a planar environment. Single-crystal X-ray analysis of 2
confirmed that the nickel is in a distorted square planar environment with S2PN chromophore.
A significant asymmetry in the Ni–S bond in 2 [2.1655(8) and 2.2120(8)Å] supports the less
effective trans effect of NCS− over PPh3. The antibacterial activities of all complexes were
analyzed at the concentration of 200 and 400 μg/ml. All the complexes exhibit antibacterial
activity against four bacterial species. Zinc dithiocarbamate complex containing furfuryl group
(complex 4) has greater activity against S. aureus and K. pneumoniae, when compared with the
standard chloramphenicol. In future work, we aim to synthesis zinc dithiocarbamate complexes
containing halogenated furfuryl group with the expectation that they will show better antibacterial
activity.
4. Experimental
All reagents and solvents were commercially available high-grade materials (Merck/sd
Fine/Himedia) and used as received. Elemental analysis was performed by Perkin Elmer 2400
series(II) CHN analyzer. IR spectra were recorded on a Thermo Nicolet Avatar 330 FT-IR
spectrophotometer (range: 4000–400 cm−1) as KBr pellets. A Shimadzu UV-1650 PC double-
beam UV–Vis spectrophotometer was used for recording the electronic spectra. The spectra were
recorded in CHCl3 and the pure solvent was used as the reference. The NMR spectra were recorded
on Bruker 400/100 and 500/125 MHz NMR spectrometers at room temperature in CDCl3, using
TMS as internal reference.
4.1. X-ray crystallography
Diffraction data for 2 were recorded on an Xcalibur-3/CCD diffractometer using graphite
monochromated MoKα radiation (λ = 0.71069Å) at ambient temperature. The structure was
solved by SHELXS and refined by fullmatrix least-square methods in SHELXL-97 (36). All
the non-hydrogen atoms were refined anisotropically and the hydrogen atoms were refined
isotropically.
4.2. Synthesis of N-furfuryl-N-isopropylamine
Isopropylamine (0.4 ml, 4 mmol) and furfuraldehyde (0.4 ml, 5.1 mmol) were dissolved in
methanol (10 ml) and the solution was stirred for 2 h at room temperature. The solvent was
removed by evaporation. The resulting yellow oil was dissolved in methanol–dichloromethane
solvent mixture (1:1, 20 ml) and sodium borohydride (0.5 g, 13.8 mmol) was added slowly at
5◦C. The mixture was stirred at room temperature for 24 h. After evaporation of the solvent, the
resulting viscous liquid was washed with water and dichloromethane was added in order to extract
the product. Evaporation of the organic layer gave N-furfuryl-N-isopropylamine as yellow oil.

Journal of Sulfur Chemistry 113
1H NMR (400 MHz, CDCl3, ppm): δ = 1.07 (d, 6H, J = 6.0 Hz, methyl protons), 2.06 (b, 1H,
NH), 2.78–2.84 (m, 1H, methine proton), 4.82 [s, 2H, NCH2(furfuryl)], 6.16 [b, 1H, H–4 (furyl)],
6.30[dd, 1H, J = 1.2 Hz, H–3(furyl)], 7.34[d, 1H, J = 0.8 Hz, H–5(furyl)]. 13CNMR(100 MHz,
CDCl3, ppm): δ = 22.7 (methyl carbons), 43.8 (methine carbons), 47.6 [NCH2(furfuryl)], 106.6,
110.1, 141.7, 154.1(furyl carbons).
4.3. Preparation of [Ni(fiprdtc2] (1)
N-Furfuryl-N-isopropylamine (0.55 g, 4 mmol) and carbon disulfide (0.3 ml, 4 mmol) were dis-
solved in ethanol (20 ml) and stirred for 30 min. NiCl2 · 6H2O (0.47 g, 2 mmol) was dissolved in
10 ml of water and added to the solution with constant stirring. A green powder precipitated that
was filtered and dried (Scheme 1).
Yield 75%, mp 290◦C. IR (KBr, cm−1): ν = 2977, 2855 (νC H(aliph.)), 1466 (νC N), 1013
−
−
(νC ). UV–Vis (CHCl3, nm): λ = 391, 481, 623. 1H NMR (500 MHz, CDCl3, ppm): δ = 1.19
−
S
(d, J = 8.0 Hz, 12H, methyl protons), 4.73 [s, 4H, NCH2 (furfuryl)], 4.82–4.86 (m, 2H, methine
proton), 6.34 [b, 2H, H–4 (furyl)], 6.41 [b, 2H, H–3 (furyl)], 7.34 [b, 2H, H–5 (furyl)].
13C NMR (125 MHz, CDCl3, ppm): δ = 19.6 (methyl carbon), 40.6 (methine carbon), 50.9
[N–CH2(furfuryl)], 110.2, 110.8, 141.9, 148.6 (furyl carbons), 208.9 (CS2). Anal. calcd. for
C18H24N2S4O2Ni (%): C, 44.36; H, 4.96; N, 5.74. Found (%): C, 44.13; H, 4.87; N, 5.61.
4.4. Preparation of [Ni(fiprdtc)(NCS)(PPh3)] (2)
Amixtureof[Ni(fiprdtc)2)](0.487 g, 1.0 mmol), PPh3 (0.524 g, 2.0 mmol), NiCl2 · 6H2O(0.237 g,
1.0 mmol) and NH4NCS (0.152 g, 2.0 mL) was refluxed for 3 h in chloroform-methanol solvent
mixture (3:2, 50 mL). The purple red solution obtained was filtered and left for evaporation.
After 2 days, a purple red solid separated out which was recrystallized from chloroform. Suit-
able single crystals for X-ray structure analysis were obtained by repeated crystallization from
dichloromethane–acetonitrile solvent mixture.
Yield 72%, mp 250◦C. IR (KBr, cm−1): ν = 3058 (νC H(arom.)), 2973–2852 (νC H(aliph.)), 2091
−
−
(NCS), 1498(νC N), 1018(νC ). UV–Vis(CHCl3, nm):λ = 249, 331, 481. 1HNMR(500 MHz,
−
−
S
CDCl3, ppm): δ = [1.25 (d, J = 7.0 Hz), 1.19 (d, J = 7.0 Hz) (6H, two methyl protons)], 4.44–
4.79 (four signals, 3H, methine and methylene protons), 6.13–7.71 (m, aromatic protons). 13C
NMR (125 MHz, CDCl3, ppm): δ = 19.5 (methyl carbon), 40.8 (methine carbon), 51.4 [NCH2
(furfuryl)], 110.8–147.6 (aromatic carbons), 205.2 (CS2). Anal. calcd. for C28H27N2S3N2OPNi
(%): C, 56.60; H, 4.58; N, 4.74. Found (%): C, 56.21; H, 4.36; N, 4.61.
4.5. Preparation of [Ni(fiprdtc)(PPh3)2]ClO4(3)
A mixture of [Ni(fiprdtc)2] (0.487 g, 1.0 mmol), NiCl2 · 6H2O (0.237 g, 1.0 mmol), PPh3 (1.048 g
4.0 mmol) and NaClO4 (0.242 g, 1.0 mmol) was refluxed for 3 h in chloroform–methanol solvent
mixture (3:2, 50 ml). The purple red solution obtained was filtered and left for evaporation. After
2 days, red solid separated out, which was recrystallized from chloroform. The complex analyzed
to [Ni(fiprdtc)(PPh3)2]ClO4.
Yield 65%, mp 230◦C. IR (KBr, cm−1): ν = 3051 (νC H(arom.)), 2973–2852 (νC H(aliph.)),
−
−
1
1490 (νC ), 1091 (ClO4), 1018 (ν S). UV–Vis (CHCl3, nm): λ = 248, 330, 482. H NMR
−
−
N
C
(500 MHz, CDCl3, ppm): δ = 1.22 (d, J = 6.0 Hz) and 1.14 (d, J = 6.5 Hz) (6H, two methyl
protons), 4.45–4.82 (four signals, 3H, methine and methylene protons), 6.16–7.76 (m, aro-
matic protons). 13C NMR (100 MHz, CDCl3, ppm): δ = 19.7 (methyl carbon), 41.4 (methine

114 P. Jamuna Rani et al.
carbon), 52.2 [NCH2(furfuryl)], 110.9–147.0 (aromatic carbons), 200.8 (CS2). Anal. calcd. for
C45H42O5P2S2NClNi (%): C, 58.21; H, 4.55; N, 1.51. Found (%): C, 58.02; H, 4.38; N, 1.42.
4.6. Preparation of complex [Zn(fiprdtc)2] (4)
A method similar to that described for the synthesis of 1 was adopted; however, ZnSO4 · 7H2O
(0.58 g, 2.0 mmol) was used instead of NiCl2 · 6H2O. White precipitate of complex was
separated out.
Yield 70%, mp 142◦C. IR (KBr, cm−1): ν = 2974–2854 (νC H(aliph.)), 1452 (νC N), 1014
−
−
(νC ). UV–Vis (CHCl3, nm): λ = 266, 290, 315. 1H NMR (500 MHz, CDCl3, ppm): δ = 1.25
−
S
(d, 12H, J = 8.5 Hz, methyl protons), 5.04 [s, 4H, NCH2 (furfuryl)], 5.26–5.32 (m, 2H, methine
protons), 6.35 [dd, 2H, J = 2.5 Hz, H–4 (furyl)], 6.49 [d, 2H, J = 5.0 Hz, H–3 (furyl)], 7.36 [t,
2H, J = 2 Hz, H–5 (furyl)]. 13C NMR (100 MHz, CDCl3, ppm): δ = 19.7, 20.0 (methyl carbon),
44.3 (methine carbon), 55.9 [NCH2 (furfuryl)], 109.9, 110.8, 141.6, 142.0, 149.1 (furyl), 205.2
(CS2). Anal. calcd. for C18H24S4N2O2Zn (%): C, 43.76; H, 4.89; N, 5.67. Found (%): C, 43.52;
H, 4.71; N, 5.54.
4.7. Preparation of complex [Zn(fiprdtc)2(1,10-phen)] (5)
Adduct was prepared by adding a hot solution of 1,10-phenanthroline (2 mmol) in ethanol to a
hot solution of complex 4 (0.494 g, 1.0 mmol) in chloroform. The resulting solution was cooled
and then added with petroleum ether (boiling range: 40–60◦C). Yellow precipitate of the adduct
was separated out (Scheme 3).
Yield 63%, mp 137◦C. IR (KBr, cm−1): ν = 3053 (νC H(arom.)), 2969–2926 (νC H(aliph.)),
−
−
1623, 1584, 1513 (1,10-phen), 1423 (νC N), 1011 (νC ). UV–Vis (CHCl3, nm): λ = 262, 299,
−
−
S
1
318. H NMR (500 MHz, CDCl3, ppm): δ = 1.16 (d, 12H, J = 8.5 Hz, methyl protons), 5.09
[s, 4H, NCH2 (furfuryl)], 5.47–5.54 (m, 2H, methine protons), 6.28 [b, 2H, H–4 (furyl)], 6.40
[d, 2H, J = 3.5 Hz, H–3 (furyl)], 7.27 [t, 2H, J = 6.0 Hz, H–5 (furyl)], 7.77 [dd, J = 5.5 and 6 Hz,
H–3 (1,10-phen)], 7.88 [s, 2H, H–5 (1,10-phen)], 8.37 [d, 2H, J = 10 Hz, H–4 (1,10-phen)], 9.55
[b, 2H, H–2 (1,10-phen)]. 13C NMR (125 MHz, CDCl3, ppm): δ = 20.1 (methyl carbon), 44.4
(methine carbon), 55.2 [NCH2(furfuryl)], 108.7, 110.5, 141.8, 151.0 (furyl), 124.1 [C–3 (1,10-
phen)], 126.5 [C–5 (1,10-phen)], 128.7 [C–4a (1,10-phen)], 137.1 [C–4 (1,10-phen)], 149.4 [C–2
(1,10-phen)], 208.2 (CS2). Anal. calcd. for C30H32N4S4O2Zn (%): C, 53.44; H, 4.78; N, 8.30.
Found (%): C, 53.12; H, 4.80; N, 8.17.
4.8. Preparation of complex [Zn(fiprdtc)(2,2-bipy)] (6)
A method similar to that described for the synthesis of 5 was adopted; however, 2,2ꢀ-bipyridine
(2 mmol) was used instead of 1,10-phenanthroline. Yellow precipitate of the adduct was
separated out.
Yield 60%, mp 110◦C. IR (KBr, cm−1): ν = 3052 (νC H(arom.)), 2969–2855 (νC H(aliph.)), 1622,
−
−
1597, 1578 (2,2-bipy), 1433 (νC N), 1013 (νC ). UV–Vis (CHCl3, nm): λ = 260, 280, 323. 1H
−
−
S
NMR (500 MHz, CDCl3, ppm): δ = 1.22 (d, 2H, J = 8.5 Hz, methyl protons), 5.05 [s, 4H, NCH2
(furfuryl)], 5.32–5.39 (m, 2H, methine protons), 6.33 [dd, 2H, J = 2.0 and 2.5 Hz, H–4 (furyl)],
6.47 [d, 2H, J = 1.0 Hz, H–5 (furyl)], 7.36 [t, 2H, J = 10.0 Hz, H–4 (2,2ꢀ-bipy)], 7.86 [t, 2H,
J = 2.5 Hz, H–5 (2,2ꢀ-bipy)], 8.33 [d, 2H, J = 3.0 Hz, H–6 (2,2ꢀ-bipy)], 8.86 [d, 2H, J = 5.0 Hz,
H–3 (2,2ꢀ-bipy)]. 13C NMR (125 MHz, CDCl3, ppm): δ = 20.1 (methyl carbon), 44.4 (methine
carbon), 55.7 [NCH2 (furfuryl)], 109.5, 110.7, 141.4, 154.5 (furyl), 121.0 [C–6 (2,2ꢀ-bipy)], 124.2
[C–4 (2,2ꢀ-bipy)], 137.4 [C–5 (2,2ꢀ-bipy)], 149.2 [C–1 (2,2ꢀ-bipy)], 149.6 [C–3 (2,2ꢀ-bipy)], 206.1

Journal of Sulfur Chemistry 115
(CS2). Anal. calcd. for C28H32S4N4O2Zn (%): C, 54.04; H, 5.18; N, 4.50. Found (%): C, 53.82;
H, 5.01; N, 4.31.
4.9. Antibacterial assay (disc diffusion method)
The disc diffusion assay was used to determine antibacterial activity of the complexes using
Gram-positive and Gram-negative strains of bacteria viz., S. aureus, E. coli,P. aeruginosa and
K. pneumoniae. Base plates were prepared by pouring 10 ml of autoclaved Muller-Hinton agar
into sterile petridishes (9 cm) and allowing them to settle. Sterile blank discs (6 mm) were impreg-
nated with 15 μl of a known concentration of stock solution of tested complexes to obtain discs
containing 200 and 400 μg of each complexes. Impregnated discs were air dried and cautiously
placed on the surface of Mueller-Hinton agar plates freshly inoculated with microorganisms.After
10 min at room temperature, the plated culture was incubated for 24 h at 37◦C. Experiments were
conducted in quadruplicate (four discs with identical concentration of the same compound) and
commercial antibiotic Chloramphenicol (100 μg) impregnated discs used as positive controls.
Susceptibility diameter zone was reported as the average value of replicates measurements.
Supplementary material
Crystallographic data have been deposited with the Cambridge Crystallographic Centre: Deposi-
tion number CCDC-901936 for 2. Copies of the data can be obtained free of charge on application
to CCDC, 12 Union Road, Cambridge CBZ IEZ, UK.
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