Copper(I)/(II) or silver(I) ions towards 2-mercaptopyrimidine: An exploration of a chemical variability with possible biological implication

Article abstract of DOI:10.1016/j.ica.2011.10.024

Direct reaction of copper(I) chloride with 2-mercaptopyrimidine (pmtH) in the presence of the triphenylphosphine (tpp) in 1:1:2 M ratio forms the mixed ligand Cu(I) complex with formula [CuCl(tpp)₂(pmtH)] (1). The dimeric {[Cu(tpp)(pmt)]₂ 0.5(MeOH)} (2) complex was derived from the reaction of 1 with twofold molar amount of sodium hydroxide. However, the reaction of copper(II) sulfate or nitrate with pmtH and tpp in 1:2:2 M ratio, unexpectedly results in the formation of the [CuSH(tpp)₂(pmtH)] (3) complex. Further studies have shown that the [Cu(tpp)₂(pmt)] (4) complex is formed by reacting copper(II) acetate with pmtH in the presence of tpp in 1:2:2 M ratio, while in the absent of tpp, the Cu(CH₃COO) ₂ or CuSO₄ is found to oxidizes pmtH to its corresponding disulfide (pmt)₂. For comparison the mixed ligand silver(I) chloride or nitrate complexes with formula [AgCl(tpp)₂(pmtH)] (5) or [Ag(NO₃)(tpp)₂(pmtH)] (6) are also synthesized by reacting of the AgCl or AgNO₃ with pmtH and tpp in 1:2:2 M ratio. The complexes have been characterized by elemental analyses, m.p., vibrational spectroscopy (mid-, far-FT-IR and Raman), ¹H NMR, UV-Vis, ESI-MS, TG-DTA spectroscopic techniques and single crystal X-ray crystallography at ambient conditions. Photolysis of 1-6, was also studied and the results showed formation of triphenylphosphine oxide. The complexes 1-6, were used to study their influence upon the catalytic peroxidation of the linoleic acid by the enzyme lipoxygenase (LOX) experimentally and theoretically. The binding of 1-4 with LOX was also investigated by saturation transfer difference ¹H NMR experiments (STD).

Full text of DOI:10.1016/j.ica.2011.10.024

Inorganica Chimica Acta 382 (2012) 146–157
Contents lists available at SciVerse ScienceDirect
Inorganica Chimica Acta
journal homepage: www.elsevier.com/locate/ica
Copper(I)/(II) or silver(I) ions towards 2-mercaptopyrimidine: An exploration
of a chemical variability with possible biological implication
G.K. Batsala a, V. Dokorou a,c, N. Kourkoumelis b, M.J. Manos d, A.J. Tasiopoulos d, T. Mavromoustakos e
ˇ ˇ f,g
ˇ
M. Simcic , S. Golic-Grdadolnik f,g, S.K. Hadjikakou a,
⇑
a Section of Inorganic and Analytical Chemistry, Department of Chemistry, University of Ioannina, 45110 Ioannina, Greece
b Medical Physics Laboratory, Medical School, University of Ioannina, Ioannina, Greece
c X-ray Unit, Department of Chemistry, University of Ioannina, Ioannina, Greece
d Department of Chemistry, University of Cyprus, 1678 Nicosia, Cyprus
e Organic Chemistry Laboratory, Department of Chemistry, University of Athens, Greece
f Laboratory of Biomolecular Structure, National Institute of Chemistry, Hajdrihova 19, SI-1001 Ljubljana, Slovenia
g EN-FIST Centre of Excellence, Dunajska 156, SI-1000 Ljubljana, Slovenia
a r t i c l e i n f o
a b s t r a c t
Article history:
Direct reaction of copper(I) chloride with 2-mercaptopyrimidine (pmtH) in the presence of the triphen-
ylphosphine (tpp) in 1:1:2 M ratio forms the mixed ligand Cu(I) complex with formula
[CuCl(tpp)2(pmtH)] (1). The dimeric {[Cu(tpp)(pmt)]2 0.5(MeOH)} (2) complex was derived from the
reaction of 1 with twofold molar amount of sodium hydroxide. However, the reaction of copper(II) sulfate
or nitrate with pmtH and tpp in 1:2:2 M ratio, unexpectedly results in the formation of the
[CuSH(tpp)2(pmtH)] (3) complex. Further studies have shown that the [Cu(tpp)2(pmt)] (4) complex is
formed by reacting copper(II) acetate with pmtH in the presence of tpp in 1:2:2 M ratio, while in the
absent of tpp, the Cu(CH3COO)2 or CuSO4 is found to oxidizes pmtH to its corresponding disulfide
(pmt)2. For comparison the mixed ligand silver(I) chloride or nitrate complexes with formula
[AgCl(tpp)2(pmtH)] (5) or [Ag(NO3)(tpp)2(pmtH)] (6) are also synthesized by reacting of the AgCl or
AgNO3 with pmtH and tpp in 1:2:2 M ratio. The complexes have been characterized by elemental anal-
yses, m.p., vibrational spectroscopy (mid-, far-FT-IR and Raman), 1H NMR, UV–Vis, ESI-MS, TG–DTA spec-
troscopic techniques and single crystal X-ray crystallography at ambient conditions. Photolysis of 1–6,
was also studied and the results showed formation of triphenylphosphine oxide. The complexes 1–6,
were used to study their influence upon the catalytic peroxidation of the linoleic acid by the enzyme
lipoxygenase (LOX) experimentally and theoretically. The binding of 1–4 with LOX was also investigated
by saturation transfer difference 1H NMR experiments (STD).
Received 25 June 2011
Received in revised form 21 September
2011
Accepted 6 October 2011
Available online 20 October 2011
Keywords:
Bioinorganic chemistry
Copper(I) complexes
Silver(I) complexes
Crystal structures
Photolysis
Ó 2011 Elsevier B.V. All rights reserved.
1. Introduction
simultaneous oxidation of thiol ligands to the corresponding
disulfides and this is also the case when copper(II) ions react with
A great number of metalloproteins and metalloenzymes such as
cytochrome oxidase [1], hemocyanin [2], tyrosinase [3], etc. con-
tain copper ions which undergo cyclic redox processes in vivo.
Although, Cu(II) ions are usually associated with oxygen and nitro-
gen, and occasionally sulfur atoms of protein residues, ions of Cu(I)
are likely to coordinate to sulfur containing groups. The high
content of cysteine in these proteins suggests involvement of
Cu(I)–sulphur interactions [4]. This led to comprehensive studies
of copper ions – sulphur containing ligands, interactions [5–7].
Ottersen et al. [5a,5b] and Simmons et al. [5c] have concluded
that copper(II) ions are readily reduced to copper(I) with the
cysteine residues of proteins (Eq. (1)) [5a–c].
2Cu2þ þ 2RSH ! 2Cu1þ þ RS-SR þ 2Hþ
ð1Þ
Wallace [5d] earlier has shown that, although disulfide was pro-
duced from the reaction between Cu(II) and thiol, however, in
some cases disulfides react with cupric ions to produce sulphides
[5d]. Recently, the isolation of CuS and Cu1.8S by reacting copper(II)
with thiourea was reported [5e]. The products have been charac-
terized with powder diffraction X-ray crystallography [5e].
Copper(I), on the other hand, is an important metal ion, which
has a strong tendency to form covalent bonds with ligands contain-
ing S or P donor atoms [6,7]. Copper(I) compounds, often, forms
oligomers and polymers with various coordination network types
[8]. These show short Cu–Cu contacts (known as cuprophilicity)
[6,7], which are less than twice the van der Waals radius of Cu
⇑
Corresponding author. Tel.: +30 26510 08374; fax: +30 26510 08786.
E-mail address: shadjika@uoi.gr (S.K. Hadjikakou).
0020-1693/$ - see front matter Ó 2011 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2011.10.024

G.K. Batsala et al. / Inorganica Chimica Acta 382 (2012) 146–157
147
(2.00–2.27 Å) [9]. Metal complexes with a d10 configuration, in par-
ticular those containing phosphine ligands, are also known to exhi-
bit interesting photophysical and photochemical properties [10].
Lipoxygenase (LOX) is an enzyme which catalyzes the oxidation
of arachidonic acid to leukotrienes, in an essential mechanism for
the cell life involving in inflammation mechanism [11a,11b]. LOX
inhibition is found to induce apoptosis [11c], while the lipid perox-
ides derived from fatty acids metabolism by LOX can regulate cel-
lular proliferation [11d]. Thus, LOX inhibition provides a potential
novel target for the treatment and chemoprevention for a number
of different cancers.
This paper, reports our studies on the structural and bioinor-
ganic chemistry properties of [CuCl(tpp)2(pmtH)] (1), {[Cu(tpp)-
(pmt)]2 0.5(MeOH)} (2), [CuSH(tpp)2(pmtH)] (3), [Cu(tpp)2(pmt)]
(4) and [AgCl(tpp)2(pmtH)] (5), [Ag(NO3)(tpp)2(pmtH)] (6) com-
plexes where pmtH = 2-mercaptopyrimidine and tpp = triphenyl-
phosphine (Chart 1). Although the crystal structures of 1, 4, 6
and (pmt)2 are already known [12,13], we proceed, however, their
redetermination as they were needed to the understanding of the
chemical behavior of the thione ligand used towards copper or sil-
ver ions.
further studied by reacting 1 with an excess sodium hydroxide
which gives the dimeric {[Cu(tpp)(pmt)]2 0.5(MeOH)} (2) complex.
In this case two [Cu(tpp)(pmt)] units come close to each other
through
l
2-SꢀꢀꢀCu and NꢀꢀꢀCu inter-unit interactions forming a di-
mer with strong Cu–Cu (d10–d10) contacts as a consequence (See
also Crystal structures). However, the reaction of copper(II) sulfate
or nitrate with pmtH and tpp in 1:2:2 M ratio, results in the forma-
tion of the [CuSH(tpp)2(pmtH)] (3) complex. The formation of 3
was detected in ESI-MS spectra by the presence of the fragments
at 735.3 m/e due to the formation of [CuSH(tpp)2(pmtH)]Åꢁ specie
towards the fragment at 734.5 m/e which corresponds to the
[CuCl(tpp)2(pmtH)]Åꢁ in ESI-MS spectra of complexes 1. The –SH
group was identified from m
(S–H) vibration band at 2640 cmꢁ1 in
the FT-IR spectrum of 3. The desulfuration of the thiol ligand and
the formation of CuSH is also observed during irradiation of the
[{(Ph3P)2Cu}2(dto)] (dto = dithioxalate) complex, where the
[(Ph3P)2(py)CuSH] complex was finally isolated [14]. In our case
the CuSH could be resulted by the redox reaction between Cu(II)
and pmtH [5]. However, we were unable to elucidate the fate of
the pyrimidine residue although, the stoichiometry of the reaction
(1:2; Cu(II):pmtH) and the reduction of Cu(II) to Cu(I) further sup-
port our assumption about the source of –SH from desulfuration of
pmtH. Besides, the formation and isolation of the disulfide (pmt)2,
when Cu(CH3COO)2 or CuSO4 reacts with pmtH further support the
proposed mechanism. However, copper(II) acetate reacts with
pmtH in the presence of tpp in 1:2:2 M ratio, to form the
[Cu(tpp)2(pmt)] (4) complex, probably due to the hydrolysis of
the copper(II) acetate and the basisity of the media. No desulfura-
tion or redox reaction occurs in case the interaction between sil-
ver(I) chloride or nitrate with the same ligands. The complexes of
formulae [AgCl(tpp)2(pmtH)] (5) or [Ag(NO3)(tpp)2(pmtH)] (6)
are synthesized by reacting AgCl or AgNO3 with pmtH and tpp in
1:2:2 M ration.
2. Results and discussion
2.1. General aspects
Complexes 1–6 have been prepared as shown in Scheme 1.
Crystals of complexes 1–6 and those of disulfide (pmt)2 have been
prepared by slow evaporation of the solutions, which remain after
the filtration of the reaction solutions (Scheme 1). The crystals of
complexes are air stable when they store in darkness at room tem-
perature. The formulae of the complexes were firstly deduced from
their elemental analysis, m.p., their spectroscopic data and single
crystal X-ray crystallography at ambient conditions. The structures
of compounds 1, 4 and 6 are identical with those already known
[12]. However, since this study aims in the elucidation of the
chemical reactivity of copper(I)/(II) or silver(I) ions towards 2-mer-
captopyrimidine and in the exploration of a chemical and struc-
tural variability of this interaction, we proceed their refinement
here again, for comparison with those of 2, 3 and 5. Moreover,
the structure of the disulfide (pmt)2, derived from the reaction of
copper acetate with 2-mercaptopyrimidine is a new polymorph
and it is reported here for the first time [13]. Table 1 summarized
synthetic condition, unit cell parameters and significant bond dis-
tances and angles of the already reported structures of 1, 4, 6 and
(pmt)2 [12,13].
2.2. Crystal structures of {[Cu(tpp)(pmt)]2 0.5(MeOH)} (2),
[CuSH(tpp)2(pmtH)] (3: 3a and 3b) and [AgCl(tpp)2(pmtH)] (5)
complexes
The structures of complexes 2, 3 and 5 were determined by
X-ray diffraction at 293(2) K. ORTEP diagrams of complexes 2, 3
and 5 are shown in Figs. 1–3, while selected bond distances and
angles are given in Table 2.
Complex 2 is di-nuclear with two copper ions under tetrahedral
geometrical environment around each copper center. One phos-
phine and one deprotonated thione ligand coordinate to Cu(I)
ion. The thione ligand chelates the copper(I) through N,S donor
atoms. The tetrahedral coordination sphere around copper atoms
Thus, the reaction of copper(I) chloride with 2-mercaptopyrim-
idine (pmtH) in the presence of triphenylphosphine (tpp) which
stabilizes the + 1 oxidation state of Cu(I) ions, in 1:1:2 M ratio
forms the mixed ligand Cu(I) complex of formula
[CuCl(tpp)2(pmtH)] (1). The acidic behavior of the H(N) proton is
consists of one P from a tpp ligand and two
l2-S and one N atoms
from a deprotonated thione. Two 2-S atoms bridge the two sub-
l
0
units. The Cu1–Cu1a distance is 2.6990(17) ÅA and is significant
shorter than twofold van der Waals radius of Cu (2.00–2.27 Å)
[9], indicating d10–d10 interaction between copper atoms [15].
Since several biological systems contain sulfur-bridged Cu(I) clus-
ters with short Cu–Cu distances the study of such interaction is
of interest [15]. This CuꢀꢀꢀCu distance in 2 is among the shortest
found for complexes containing the Cu2S2 core (Cu–Cu varying be-
tween 2.519 and 2.888 Å (Table 3) [6a,15–17] and is also, compa-
rable with the Cu–Cu distance in case of Cu8S12 bridged cluster
(2.79–2.91 Å [15]).
P
N
Inter-molecular linkages, in case of 2, via N1ꢀꢀꢀC23
(solv) = 2.86(2) Å interactions (Fig. S1) lead to a polymeric assem-
bly forming one dimensional infinite ribbon structure.
N
H
S
Complex 3 is monomer. Two phosphorus from two tpp ligands
and one sulfur atoms from pmtH ligand are coordinated to Cu(I)
cation. The tetrahedral geometry is completed by –SH group. Crys-
tals of 3 were synthesized by reacting either CuSO4 (3a) or
pmtH
tpp
Chart 1. Molecular formula of 2-mercaptopyrimidine (pmyH) and triphenylphos-
phine (tpp).

148
G.K. Batsala et al. / Inorganica Chimica Acta 382 (2012) 146–157
N
S
N
PPh3
Cu
Cl
PPh3
HN
MeOH/MeCN
MeOH/MeCN
NaOH
CuCl + HN
N
+ 2 Ph3P
Cu
Cu
(2)
S
Ph3P
Ph3P
S
N
S
(1)
N
N
PPh3
Cu
CuSO4 or
HN
N
MeOH/MeCN
reflux
+ 2
HN
N
+ 2 Ph3P
Cu(NO3)2
(3: 3a; SO4, 3b; NO3)
S
Ph3P
Ph3P
SH
S
S
EtOH
+ 2 HN
N
+ 2 Ph3P
Cu
Cu(CH3COO)2
N
Ph3P
N
(4)
S
N
N
Cu(CH3COO)2 or
CuSO4
MeOH/MeCN
MeOH/MeCN
HN
N
+ 2
S
S
(pmt)2
N
S
N
PPh3
Ag
AgCl or
HN
+ 2 HN
N
+ 2 Ph3P
AgNO3
X=Cl (5), NO3 (6)
S
Ph3P
X
N
S
Scheme 1. Preparation reactions of complexes 1–6.
Cu(NO3)2 (3b) (Scheme 1). Both complexes crystallizes in the same
space group (P21/c) with identical unit cell dimensions (3a:
a = 14.4520(10), b = 10.1450(10), c = 24.382(2) Å, b = 94.500(10)°,
3b: a = 14.440(4), b = 10.139(3), c = 24.379(4) Å, b = 94.49(2)°).
Moreover, crystals of 3a and 3b show similar unit cell dimension
(2.4647(4) Å) and Ag1–P2 (2.4572(4) Å) bond lengths are longer
than the corresponding ones found in the CuCl(tpp)2(pmtH) ana-
logue (Cu1–Cl1 = 2.3621(9), Cu1–S1 = 2.3691(10), Cu–P1 = 2.2748
(10) and Cu–P2 = 2.2852(11) Å) [12a,12b]. The bond angles around
the metal center lie between 97° and 123° (Table 1) and they var-
ied from the ideal value of 108°280 of ideal tetrahedron due to the
different strength of valance shell electron pairs repulsions
(VSEPR) because of the different electronegativity of the donor
atoms (P, S and Cl) bonded to Cu(I) ion.
with those found for
1 (space group: P21/c, a = 14.3006(3),
b = 10.0842(2), c = 24.1240(5), b = 94.280(2)°) indicating that the
tetrahedron packet similarly in the crystal lattice in theses
complexes. However, ESI-MS spectra (fragments at 735.3 and
734.5 m/e respectively corresponding to the [CuSH(tpp)2(pmtH)]Åꢁ
and [CuCl(tpp)2(pmtH)]Åꢁ species) further support the formation of
the CuSH from the reaction of copper(II) sulfate or nitrate with
pmtH. The Cu1–S1 bond distance is 2.3652(6) Å. This is in the
range of the Cu–S distance (2.322 Å) found in the [(Ph3P)2(py)-
CuSH] [14]. The latter was formed by decomposition after irradia-
tion of the complex [{(Ph3P)2Cu}2(dto)] (dto = dithioxalate).
Complex 5 is also monomer with disorder tetrahedral geometry
around Ag(I) ion. Two phosphorus from two tpp ligands and one
chloride atoms from pmtH ligand are coordinated to the metal cen-
ter. The unit cell dimensions (14.2375(3), 10.2000(2), 24.6616(7)
b = 94.184(2)o) are close to those found for 1 and in 3a, 3b (see
above). The Ag1–Cl1 (2.6061(4) Å), Ag1–S1 (2.6151(4) Å), Ag1–P1
2.3. Thermal decomposition
TG/DTA analysis (under nitrogen) of complexes 1 and 3–5
shows similar decomposition patterns. Thus, complexes 1 and 3–
5 are stable until 200 °C and then decomposes in one endothermic
step (200–300 °C) which corresponds to the mass loss of two tpp
ligands (1: found: 77%, calc. 71%, 3: found: 71%, calc. 71%, 4: found:
72%, calc. 75% and 5: found: 69%, calc. 67%). In case of 2 the TG/DTA
diagram shows that the compound decomposes in two endother-
mic steps (130–150 and 200–250 °C), which correspond to the
mass loss of two tpp (found: 31% and 40%, calc. 30%). TG/DTA dia-
gram of 6 shows that the compound also, decomposes in two

G.K. Batsala et al. / Inorganica Chimica Acta 382 (2012) 146–157
149
steps; one exothermic decomposition step between 70 and 125 °C
which corresponds to the mass loss of one nitric group (found: 6%,
calc. 8%) and one endothermic peak between 200 and 300 °C which
corresponds to the mass loss of two tpp ligands (found: 66%, calc.
65%).
2.4. Continuous photolysis
Since the formation of CuSH was also observed when
[{(Ph3P)2Cu}2(dto)] (dto = dithioxalate) complex irradiated by UV
light to form the [(Ph3P)2(py)CuSH] complex the continues photol-
ysis of complexes 1–6 was also studied. The ultra-violet spectra of
complexes 1–6 in chloroform are dominated by absorption bands
with kmax at approximate 390, 290–260 and 240 nm respectively
(kmax nm (e); 1: 393 (1682), 292 (12372), 240 (17257), 2: 393
(949), 262 (20820), 240 (17231), 3: 393 (3692), 292 (32269), 240
(31767), 4: 393 (949), 290 (20820), 240 (17231), 5: 393 (920),
276 (29642), 259 (30205), 240 (26793) and 6: 364 (1748), 276
(24521), 259 (22662), 240 (23952)). Bands at app. 290–260 nm
and 240 nm are ascribed to the intra-ligand (p⁄
p) transitions
of triphenylphosphine and thione ligands [18–20], while bands at
app. 390 nm are ascribed to the CT band of thione [20]. Free tri-
phenylphosphine shows a broad band with kmax at 262 nm with a
molar absorption coefficient of 11900 [20] while the spectrum of
free thione in chloroform consist of absorption bands at 380.5 and
291.5 nm having
e values 1560 and 13460 respectively [20].
The light sensitivity of complexes 1–6 under UVC radiation was
also studied. Irradiation of 1–6 with UVC radiation in chloroform
solution at room temperature causes the decomposition of the
complexes within time. Fig. 4 shows the UV spectral changes in
the region of 225–400 nm of a 5 ꢂ 10ꢁ5 M CHCl3 solution of com-
plex 2, 3 and 5 during irradiation (0, 15, 30, 45, 60, 75, 90 and
105 s) with ultraviolet light at room temperature. In complexes
1, 3, 4, 5 and 6, a monotonic reduction of the absorbance is ob-
served with no appearance of new bands indicating the decompo-
sition of the complex. However, in case of 2 an increasing of the
absorbance is observed initially, followed by a monotonic reduc-
tion of the absorbance. Thus, UV light, may be causes splitting of
2 to its components, which then could be decomposes similarly
to the monomeric complexes 1, 3, 4, 5 and 6.
For the characterization of the photoproduct, a solution of
60 mg of complexes 1–6 in 10 cm3 chloroform was irradiated for
1 h in a quartz conical flask under aerobic conditions. The process
was monitored by TLC. The solutions were filtered off and the fil-
trates were concentrated to dryness. The product generated in all
cases was verified from its physical (m.p. = 149–151 °C) and spec-
tral (FT-IR) data which are identical with the corresponding data of
triphenylphoshine oxide [18]. Fig. 5 shows the FT-IR spectrum of
complex 3 (A) and the correspondiong of its photoproduct derived
upon continues photolysis of 3 (B) in contrast to the spectrum of
triphenylphoshine oxide (C). The presence of the m(P@O) vibration
band at 1376 cmꢁ1 in the IR spectra of the complexes indicates the
phosphine oxide formation [18]. Reva et al. have previously con-
cluded that irradiation of tpp with UV light in the presence of oxy-
gen lead to the formation of triphenylphoshine oxide [21].
Therefore, based on these findings, tpp ligand is released in solu-
tions of 1 and 2 during photolysis which followed by its oxidation
to triphenylphoshine oxide by air.
2.5. Study of the peroxidation of linoleic acid with the enzyme
lipoxygenase in the presence of complexes 1–6
In order to investigate the modification in an enzyme activity
caused by the copper or silver complexes the influence of com-
plexes 1–6 on the oxidation of linoleic acid by lipoxygenase was
studied in a wide concentration interval. The activity of the

150
G.K. Batsala et al. / Inorganica Chimica Acta 382 (2012) 146–157
Fig. 1. (A) ORTEP diagram of compound 2 together with the atomic numbering scheme. Thermal ellipsoids drawn at the 50% probability level. Solvent molecule is omitted for
clarity.
Fig. 2. ORTEP diagram of compound 3 together with the atomic numbering scheme. Thermal ellipsoids drawn at the 50% probability level.
enzyme (A, %) in the presence of the complex was calculated using
a known procedure [22a]. The concentrations at which the enzy-
matic activity is inhibited by 50% (IC50) for the complexes are: 24
the dimmer complex 2 showed the strongest inhibitory activity
among the compounds tested.
The binding of 1, 2, 3 and 4 towards LOX was also investigated
(1), 7 (2), 30 (3), 19 (4), 28 (5) and 47 (6)
lM, respectively, Thus
by saturation transfer difference 1H NMR experiment. On the top of

G.K. Batsala et al. / Inorganica Chimica Acta 382 (2012) 146–157
151
Fig. 3. ORTEP diagram of compound 5 together with the atomic numbering scheme. Thermal ellipsoids drawn at the 50% probability level.
Table 2
Selected bond lengths (Å) and angles (°) of complexes 2, 3 and 5.
Complex 2
Complex 3a
Complex 3b
Complex 5
(a) Bond lengths
Cu1–S1
Cu1–P1
(a) Bond lengths
Cu1–S1
Cu1–S2
Cu1–P1
Cu1–P2
(a) Bond lengths
Cu1–S1
Cu1–S2
Cu1–P1
Cu1–P2
2.671(3)
2.198(2)
2.051(7)
2.313(3)
2.6990(17)
1.734(10)
2.3652(6)
2.3718(5)
2.2861(6)
2.2770(5)
1.692(2)
2.3629(6)
2.3697(5)
2.2842(6)
2.2735(5)
1.687(2)
Ag1–Cl1
Ag1–S1
Ag1–P1
Ag1–P2
S1–C37
2.6061(4)
2.6151(4)
2.4647(4)
2.4572(4)
Cu1–N2
Cu1–S1a
Cu1–Cu1a
S1–C9
S1–C37
S1–C37
1.6913(16)
(b) Angles
(b) Angles
(b) Angles
S1–Cu1–P1
S1–Cu1–N2
Cu1a–Cu1–S1
S1–Cu1–S1a
Cu1a–S1–Cu1
119.62(9)
65.7(3)
51.02(7)
111.67(9)
65.11(7)
S1–Cu1–S2
S1–Cu1–P1
S1–Cu1–P2
S2–Cu1–P1
S2–Cu1–P2
P1–Cu1–P2
108.69(2)
98.03(2)
111.87(2)
113.85(2)
102.33(2)
121.87(2)
S1–Cu1–S2
S1–Cu1–P1
S1–Cu1–P2
S2–Cu1–P1
S2–Cu1–P2
P1–Cu1–P2
108.76(2)
97.94(2)
111.85(2)
113.97(2)
102.23(2)
121.90(2)
Cl1–Ag1–S1
Cl1–Ag1–P1
Cl1–Ag1–P2
S1–Ag1–P1
S1–Ag1–P2
P1–Ag1–P2
103.56(1)
98.43(1)
110.80(1)
116.61(1)
102.71(1)
123.18(1)
Fig. 6A–D the aromatic region of the off-resonance NMR spectra are
shown and on the bottom the on-resonance saturation transfer dif-
ference 1H NMR spectra of the complexes 1, 2, 3 and 4. Resonance
signals attributed to the aromatic protons of the ligands ca 7.8–
7.5 ppm of the complexes studied are present in the binding mode
of the protein. Signals at 7.5–7.65 ppm are attributed to triphenyl-
phosphine, while those at 7.7–7.8 ppm to 2-mercaptopyrimidine.
Thus, both components of the complexes, pmtH and triphenyl-
phosphine have binding affinity at LOX receptor [22b]. This exper-
iment provides direct evidence for the binding affinity of the
complexes with LOX and supports experimental results reported
above.
seem to be any preferable binding pocket for all the complexes
indicating different interaction relationships towards the enzyme
inhibition. Close values of binding energy are perceived even for
completely different poses and binding orientations. Since the re-
sults might be misleading regarding the topological parameters,
our conclusions are based on the total binding energy of the inhib-
itors and substrate. The binding energy (E) of the substrate (S: lin-
oleic acid) to its binding site in the enzyme LOX (E) when ES
(enzyme:substrate) complex formed, is E = ꢁ100.2 kJ/mol. The cor-
responding binding energies of inhibitors (I), in EI (enzyme:inhib-
itor) and ESI (enzyme:substrate:inhibitor) are calculated and
shown along with the experimental IC50 values in Table 4.
The complexes with the lowest EI (1, 2, 3, 5) reside to the active
site of the protein as this was identified by our group [23] while
their energy is higher than that of the ES. It is noteworthy to men-
tion that among amino acid residues which form the docking cav-
ity of the inhibitor 1, 2, 3 and 5 in EI complex, cysteine is included
2.6. Computational studies
Molecular docking studies have been used to further assess the
inhibitory effectiveness of the complexes on LOX. There does not

152
G.K. Batsala et al. / Inorganica Chimica Acta 382 (2012) 146–157
Table 3
0
Reported copper–copper (ÅA) distances in complexes.
0
Complex
Ref.
(CuꢀꢀꢀCu) (AÅ)
2.6990(17)
2.796
⁄
{[Cu(tpp)(pmt)] 0.5(MeOH)}2
[Cu2L(SCN)2]
Cu(tu)3BF4
Cu(S-dmtu)3BF4
[CuSCN(pytH)2]2
2
AZFRCU
CUDMTB20
CUTUBF30
EGEWIW
EKALIL
FOSTOX
FULXOZ
GEZWOX
[16a]
[16b]
[16b]
[16c]
[16d]
[16e]
[16f]
[16g]
[16h]
[6a]
[17a]
[17b]
[17c]
[17d]
[17e]
[17f]
[16g]
2.840(3)
2.828
2.888
[Cu(C9H6NS)]n
2.7922(8)
2.845(1)
2.613(3)
2.681(2)
2.641(2)
2.764(l)
2.797(3)
2.519
2.547(1)
2.759(2)
2.5526(5)
2.701(5)
2.928(1)
[Cu2(MePh-mpt)2(PPh3)2]
[Cu(SC6H4CH3-o)(l,l0-phenanthroline]2 CH3CN
{[Cu2(bzimztH)5]}2(ClO4)2 7H2O
[Cu4(l2-dppm)3(l2-l2-NS2)(l2-l2-NS2)]
[Cu(tmtp)(bzimtH)Cl]2
KUTSIB
LAZLUT
MECZUQ
MRIMCU
PAKSOJ
PUTRIF
[Cu(siig)(pp)]
[Cu7(StBu)4(hfa)3(PMe3)3]
{[CuI10CuII2(MMI)12(MeCN)4](BPh4)(MeCN)4}
[Cu6(dmpymt)6]
[Cu2{
[AuIIICuI8
[Cu(bztzdtH)(PPh3)Br]2
l
-SC(NH2)2}2{SC(NH2)2}4]2+
(l
-dppm)3(tdt)5]+
TAVYIZ
TAZHEH
⁄This work, L = 20-membered macrocyclic Schiff base, tu = thiourea, S-dmtu dimethylthiourea, pytH = 2-mercaptopyridine,
C9H6NS = 8-thioquinoline, MePh-mpt = methylphenylpyruvate thiosemicarbazone, PPh3 = triphenylphosphine, HSC6H4CH3-o =
o-tolylthiole, bzimztH = 2-mercaptobenzimidazole, dppm = bis-(diphenylphoshino) methane, NS22ꢁ = 1,8-naphthalenedithiolate,
tmtp = tris(m-tolyl)phosphine, bzimtH = benzimidazole-2-thione, Hsiig = 1,2:5,6-di-O-isopropylidene-3-thio-a-o-glucofuranose,
pp = 1,2-bis(diphenylphosphinoethene), hfa = hexafluoroacetylacetonate, MMI = N-methyl-2-mercaptoimidazole, Hdmpymt =
4,6-dimethylpyrimidine-2-thione, tdt = toluene-3,4-dithiolate, dppm = bis(diphenylphosphino)methane, bztzdtH = benz-1,
3-thiazolidine-2-thione.
(Table 4). When the substrate is present, all molecules bind away
to another pocket which is thermodynamically far more favorable
for 1, 2, 3 and 5 than the EI analogous and comparable to the EI
complex in the case of 4 and 6. The stability of the ESI complexes
features a positive correlation with the inhibitory effect evaluated
experimentally although this finding is probably coincidental since
the effectiveness of irreversible inhibitors cannot be assessed by
IC50 values.
Spectroscopic data (UV and NMR) show that complexes 1–6, in-
hibit the catalytic peroxidation of linoleic acid by the enzyme LOX.
Docking calculations also show that among amino acid residues
which form the docking cavity of the inhibitor 1, 2, 3 and 5 in EI
complex, cysteine is included (Table 4). Since sulfur containing
amino acids, such as cysteine, are known to play an important role
on the proteins function by stabilizing their intermolecular assem-
blies thought –SH hydrogen bonding interactions or –S–S– bonds,
the desulfuration of the thiols upon redox reaction with copper(II)
salts might be modulating protein activity.
3. Conclusions
4. Experimental
The complexes 1–6 were studied here for their structural, pho-
tochemical and bioinorganic properties. 2-Mercaptopyrimidine is
readily coordinated to copper(I) chloride in the presence of tpp
to form the monomer complex [CuCl(tpp)2(pmtH)] (1). This is also
the case when silver chloride and nitrate is used, where the
[AgCl(tpp)2(pmtH)] (5) or [Ag(NO3)(tpp)2(pmtH)] (6) complexes
are formed. The acidic behavior of the H(N) proton in 1 was proved
by the formation of the dimeric {[Cu(tpp)(pmt)] 0.5(MeOH)}2 (2)
complex when 1 reacts with sodium hydroxide. In this case two
[Cu(tpp)(pmt)] units come close to form the dimer due to strong
4.1. Materials and instruments
All solvents used were reagent grade. Copper(I) chloride (Rie-
del–deHaen), triphenylphosphine (Merk) ligand (Aldrich-Merk)
were used with no other purification prior to use. Elemental anal-
yses for C, H, N, and S were carried out with a Carlo Erba EA MODEL
1108. Melting points were measured in open tubes with a STUART
scientific apparatus and are uncorrected. Infra-red spectra in the
region of 4000–370 cmꢁ1 were obtain in KBr discs while far-in-
fra-red spectra in the region of 400–50 cmꢁ1 were obtain in poly-
l
2-S and N–Cu inter-unit interactions with Cu–Cu (d10–d10) con-
0
tacts as a consequence. The CuꢀꢀꢀCu distance of 2.700(2) ÅA in 2, is
significant shorter from the twofold of copper Waals radius
(4.00–4.54 Å) [3]. Therefore this distance could be defined as
Cu–Cu bonding interaction.
The reaction of copper(II) sulfate or nitrate with pmtH and tpp,
on the other hand, results in the formation of the [CuSH(tpp)2-
(pmtH)] (3) complex. The formation CuSH could be explained by
the redox reaction between Cu(II) and pmtH [5] (Scheme 2).
Besides, the formation of the disulfide (pmt)2, when Cu(CH3COO)2
or CuSO4 reacts with pmtH further support the proposed reaction
path.
Irradiation of 1–6 with UVC light caused their decomposition
and the formation of triphenylphosphine oxide. In contrary, to
the formation of CuSH which derived during irradiation of the
[{(Ph3P)2Cu}2(dto)] (dto = dithioxalate) complex [14], no any depo-
sition of CuSH, by desulfuration of the thiole ligand, was observed
in the case of 1–6 complexes.
ethylene discs, with
a
Perkin-Elmer Spectrum GX FT-IR
spectrometer. A Jasco UV/Vis/NIR V 570 series spectrophotometer
was used to obtain the electronic absorption spectra. Thermal
studies were carried out on a Shimadzu DTG-60 simultaneous
DTA–TG apparatus, under a N2 flow (50 cm3 minꢁ1) at a heating
rate of 10 °C minꢁ1
.
4.2. Synthesis and crystallization of [CuCl(tpp)2(pmtH)] (1),
{[Cu(tpp)(pmt)]2 0.5(MeOH)} (2), [CuSH(tpp)2(pmtH)] (3),
[Cu(tpp)2(pmt)] (4), [AgCl(tpp)2(pmtH)] (5) and
[Ag(NO3)(tpp)2(pmtH)] (6) complexes
The synthesis and characterization of 1, 4, 6 and (pmt)2 are
already reported [12,13]. However, these compounds and the
complexes 2, 3 and 5 were prepared also here as follows:
1 mmol (0.262 g) triphenylphosphine and 0.5 mmol (0.056 g)

G.K. Batsala et al. / Inorganica Chimica Acta 382 (2012) 146–157
153
1.4
1.2
1
(Α)
b
a
0.8
0.6
0.4
0.2
0
c
d
e
200
250
300
350
400
450
500
(Β) 1.2
a
1
b
c
0.8
0.6
0.4
0.2
0
d
e
f
g
h
200
250
300
350
400
450
500
1
(C)
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
a
b
c
d
e
f
g
h
200
250
300
350
400
450
500
Fig. 4. UV absorption spectrum of 5 ꢂ 10ꢁ5 M CHCl3 solution containing 2 (A), 3 (B) or 5 (C), after irradiation with UVC light at room temperature for 0 (a), 15 (b), 30 (c), 45
(d), 60 (e), 75 (f), 90 (g) and 105 (h) s.
2-mercaptoryrimidine were suspended to 20 cm3 methanol/ace-
tonitrile solution (1:1) which contains 0.5 mmol of copper(I)
chloride (0.052 g) (1), silver chloride (0.072 g) (5) or silver
nitrate (0.085 g) (6). The mixture was stirred until a clear solu-
tion is formed. The clear solution was then filtered off and kept
in darkness at r.t. After 24 h orange (1) or yellow (5, 6), crystals,
of complexes suitable for single crystal analysis by X-ray crystal-
lography, were filter off.
in 20 cm3 methanol/acetonitrile (1:1) is heated under reflux, until
a clear solution. The solution was filtered off and the clear solution
was kept in darkness at r.t. After few days orange crystals, of com-
plex 3 suitable for single crystal analysis by X-ray crystallography,
was filter off.
Copper(II) acetate1-hydrate, (0.5 mmol, 0.263 g), triphenyl-
phosphine (1 mmol, 0.262 g) and 2-mercaptoryrimidine (1 mmol,
0.113 g) are suspended in 15 cm3 ethanol. The mixture is stirred
until a clear solution is formed. The solution was then filtered off
and it kept in darkness at r.t. After few days, light orange crystals,
of complex 4 suitable for single crystal analysis by X-ray crystallog-
raphy, was filter off. The disulfite of 2-mercaptopyrimidiner was
prepared as follows: copper(II) acetate1-hydrate, (0.5 mmol,
0.263 g) and 2-mercaptoryrimidine (1 mmol, 0.113 g) were dis-
solved in 20 ml methanol/acetonitrile (1:1). The clear solution
was filtered off and it was kept in darkness at r.t. After few days
pale orange crystals, of (pmt)2 suitable for single crystal analysis
by X-ray crystallography, was filter off.
Methanol solution (10 cm3) of 2 mmol NaOH (0.008 g) was
added to a suspension of 20 cm3 methanol/acetonitrile (1:1) which
contains 1 mmol [CuCl(tpp)2(pmtH)] (0.074 g) and the solution was
stirred, until a clear solution is formed. The solution was filtered off
and it kept in darkness at r.t. Few days after, yellow crystals of 2,
suitable for single crystal analysis by X-ray crystallography were fil-
ter off.
A
suspension of 0.5 mmol copper(II) sulfate pentahydrate
(0.124) g or copper(II) nitrate trihydrate (0.121 g), 1 mmol triphen-
ylphosphine (0.262 g) and 1 mmol 2-mercaptoryrimidine (0.112 g)

154
G.K. Batsala et al. / Inorganica Chimica Acta 382 (2012) 146–157
Fig. 5. FT-IR spectrum of complex 3 (A) and its photoproduct derived upon continues photolysis of 3 (B) in contrast to the corresponding spectrum of triphenylphoshine oxide
(C).
Complex 1: orange crystal, yield: 80%, melting point: 193–
197 °C. Elemental analysis, Anal. Calc. for C40H34ClCuN2P2S: C,
65.3; H, 4.55; N, 3.81; S, 4.36. Found: C, 65.7; H, 4.67; N, 3.34; S,
4.88%. IR (cmꢁ1), (KBr): 1608vs, 1434s, 1174s, 997m, 517s; Far-IR
(cmꢁ1), (polyethylene): 241m, 205m, 120vs; MS m/z: 735.5
247m, 191m, 139vs; MS m/z: 631 [Ag(tpp)2]+, UV–Vis (CHCl3): kmax
(loge): 392 nm (2.96), 275 nm (4.47), 258 nm (4.48), 240 nm
(4.43); Raman (cmꢁ1): 171 m, 210 m, 319 m.
Complex 6: yellow crystal, yield: 86%, melting point: 155–
160 °C. Elemental analysis, Anal. Calc. for C40H34AgN3O3P2S: C,
59.57; H, 4.24; N, 5.21; S, 3.97. Found: C, 59.90; H, 4.21; N, 5.00;
S, 4.10. IR (cmꢁ1), (KBr): 1608vs, 1478s, 1186s, 984m, 506s; Far-
IR (cmꢁ1), (polyethylene): 247m, 191m, 139vs; MS m/z: 851
[CuCl(tpp)2(pmtH)]ꢁ., 587 [Cu(tpp)2]+; UV–Vis (CHCl3): kmax (log
e):
392 nm (3.22), 291 nm (4.09), 239 nm (4.24); Raman (cmꢁ1): 207s,
414 m, 441 m.
Complex 2: yellow crystal, yield: 10%, melting point: >260 °C.
Elemental analysis, Anal. Calc. for C44H36Cu2N4P2S2: C, 60.47; H,
4.15; N, 6.41; S, 7.34. Found: C, 59.4; H, 4.25; N, 6.50, S, 7.55%. IR
(cmꢁ1), (KBr): 1567s, 1377vs, 1178s, 1094m, 504s; Far-IR (cmꢁ1),
[Ag(tpp)2]+, UV–Vis (CHCl3): kmax (log
e): 393 nm (3.13), 278 nm
(4.15), 239 nm (4.19); Raman (cmꢁ1): 126m, 179m, 324m.
4.3. X-ray structure determination
(polyethylene):
225vs,
210s,
125 ms;
MS
m/z:
808
):
[Cu(tpp)2(pmtH)2]+, 587 [Cu(tpp)2]+; UV–Vis (CHCl3): kmax (log
e
Intensity data for the crystals of 1, 3 and 5 were collected on an
Oxford Diffraction CCD instrument [24a], while a Bruker P4 diffrac-
tometer was used for 2, 4 and 6 using graphite-monochromated
Mo radiation (k = 0.71073 Å). Cell parameters were determined
by least-squares refinement of the diffraction data from 25 reflec-
tions [24b,24c].
All data were corrected for Lorentz-polarization effects and
absorption [24a,24b]. The structures were solved with direct
methods with SHELXS97 [24c] and refined by full-matrix least-
squares procedures on F2 with SHELXL-97 [24d] All non-hydrogen
atoms were refined anisotropically, hydrogen atoms were located
at calculated positions and refined via the ‘‘riding model’’ with
isotropic thermal parameters fixed at 1.2 (1.3 for CH3 groups)
times the Ueq value of the appropriate carrier atom. Significant
crystal data for the structure 2, 3a, 3b, 5 and (pmt)2 are given
in Table 5.
392 nm (2.98), 261 nm (4.32), 239 nm (4.24); Raman (cmꢁ1):
123m, 320m, 418s, 440m.
Complex 3: orange crystal, yield: 10% (15% when copper(II) ni-
trate trihydrate was used), melting point: 194–199 °C. Elemental
analysis, Anal. Calc. for C40H35CuN2P2S2: C, 65.52; H, 4.81; N,
3.82; S, 8.74. Found: C, 65.45; H, 4.62; N, 3.41; S, 8.44%. IR
(cmꢁ1), (KBr): 1607m, 1575vs, 1175s, 1094m, 508s; Far-IR
(cmꢁ1), (polyethylene): 205m, 123m; MS m/z: 734.6
[CuSH(tpp)2(pmtH)]ꢁ, 587 [Cu(tpp)2]+; UV–Vis (CHCl3): kmax
(loge): 392 nm (3.57), 291 nm (4.50), 239 nm (4.50); Raman
(cmꢁ1): 414s, 444m.
Complex 4: light orange crystal, yield: 42%, melting point: 153–
157 °C. Elemental analysis, Anal. Calc. for C40H33CuN2P2S: C, 68.71;
H, 4.75; N, 4.01; S, 4.58. Found: C, 69.10; H, 4.35; N, 3.90; S, 4.92%.
IR (cmꢁ1), (KBr): 1567s, 1370vs, 1181 ms, 1094s, 516s; Far-IR
(cmꢁ1), (polyethylene): 221 m, 205m, 124s; MS m/z: 587
[Cu(tpp)2]+; UV–Vis (CHCl3) kmax (log
e
): 392 nm (3.12), 261 nm
4.4. Photolysis studies
(4.45), 239 nm (4.37); Raman (cmꢁ1): 350m, 418s, 435m.
Complex 5: yellow crystal, yield: 74%, melting point: 175–
180 °C. Elemental analysis, Anal. Calc. for C40H34ClAgN2P2S: C,
61.59; H, 4.39; N, 3.59; S, 4.11. Found: C, H, N. IR (cmꢁ1), (KBr):
1608s, 1435s, 1175s, 1095m, 506s; Far-IR (cmꢁ1), (polyethylene):
A TUV 15W G15 T8 low-pressure mercury vapour discharge
lamps with a tubular glass envelope UVC lamp, 15 watt, manufac-
tured by Phillips was used for the photolysis. The photolysis was
performed as follows: A 5 ꢂ 10ꢁ5 M solution of 1–6 in chloroform

G.K. Batsala et al. / Inorganica Chimica Acta 382 (2012) 146–157
155
8.10
8.00
7.90
7.80
7.70
7.60
7.50
7.40
7.30
7.20
7.10
ppm
(A)
8.00
7.90
7.80
7.70
7.60
7.50
7.40
7.30
7.20
ppm (f1)
(B)
8.00
7.90
7.80
7.70
7.60
7.50
7.40
7.30
7.20
1H (ppm)
(C)
8.00
7.90
7.80
7.70
7.60
7.50
7.40
7.30
7.20
ppm
(D)
Fig. 6. Off-resonance reference NMR spectrum (top) and on-resonance saturation transfer difference NMR spectrum (bottom) for the 1 (A), 2 (B), 3 (C) and 4 (D) complexes.
Spectra are not to scale, on-resonance saturation transfer difference NMR spectrum has approximately 200-fold (1), 50-fold (2), 60-fold (3) and 25-fold (3) lower intensity
compared to the corresponding reference spectra.
was kept in a 1 cm quartz cell under aerobic conditions and the
solution was irradiated with ultraviolet light (all spectrum).
The cell was placed at a distance of 20 cm from the UV source.
Characterization of the photo-products was carried out on a solu-
tion of 0.060 g of 1–6 in 10 cm3 chloroform which was irradiated
for 1 h in a quartz conical flask under aerobic conditions.

156
G.K. Batsala et al. / Inorganica Chimica Acta 382 (2012) 146–157
Table 4
Binding energies of inhibitors (I), in enzyme:inhibitor (EI) and enzyme:substrate:inhibitor (ESI) complexes along with the experimental IC50 values.
Complexes EI (kJ/
ESI (kJ/
mol)
Amino acid residues form the docking cavity of the inhibitor in EI complex
IC50
M)
mol)
(
l
1
2
ꢁ64.9
ꢁ95.0
ꢁ98.8
Arg533, Arg767, Asn128, Asn534, Asn535, Asn769, Asn835, Asp243, Asp768, Cys127, Gln766, Glu244, His515, His531,
Leu246, Leu527, Lys526, Phe108, Pro530, Ser129, Thr529, Trp772, Tyr184, Tyr525, Tyr532, Val126, Val520, Val762
Ala145, Arg141, Arg182, Arg533, Arg767, Asn128, Asn146, Asn534, Asn769, Asp243, Asp768, Cys127, Glu244, His515,
His522, Leu169, Leu246, Leu527, Lys526, Phe108, Phe143, Phe144, Pro530, Ser129, Thr529, Trp772, Tyr184, Tyr525,
Tyr532, Val126, Val520
24
ꢁ40.35
7
3
4
5
6
ꢁ69.7
ꢁ98.1
ꢁ19.5
ꢁ98.9
ꢁ87.6
ꢁ100.8
ꢁ97.1
ꢁ85.0
Arg533, Arg767, Asn128, Asn534, Asn769, Asn835, Asp243, Asp768, Cys127, Glu244, His515, Leu246, Lys110, Lys526,
Phe108, Pro530, Thr529, Trp772, Tyr525, Tyr532, Val126, Val520, Val762
Ala426, Ala710, Arg712, Asn424, Asn550, Gln267, Glu271, Glu282, Glu554, Ile281, Ile738, Ile746, Leu423, Leu558, Leu742, 19
Lys741, Phe274, Phe557, Pro559, Pro743, Ser425, Ser560, Ser740, Thr555, Thr556, Thr709, Thr739
Arg141, Arg182, Arg533, Arg767, Asn128, Asn534, Asn769, Asn835, Asp243, Asp768, Cys127, Glu244, His515, His531,
Leu246, Leu527, Lys526, Phe108, Phe143, Phe144, Pro530, Ser129, Thr529, Trp772, Tyr525, Tyr532, Val126, Val520, Val762
Arg318, Gln329, Gln334, Glu315, Glu752, Gly827, His331, Leu316, Leu828, Lys326, Phe327, Pro328, Pro330, Pro699,
Thr756, Thr829, Tyr293, Tyr317, Tyr698
30
28
47
N
N
N
N
N
N
- 2 H+
S
S
2 Cu(II) + 4
SH
2 CuSH +
CuSH + pmtH + 2 tpp
[CuSH(tpp)2(pmtH)] (3)
C
Scheme 2.
Table 5
Structure refinement details for the complexes 3–7.
2
3a
3b
5
(pmt)2
Empirical formula
Formula weight
T (K)
C44H36Cu2N4P2S2 0.5(CH3OH)
896.52
293(2)
C40H34CuN2P2S2
732.32
293(2)
C40H34CuN2P2S2
732.32
293(2)
C40H34AgClN2P2S
780.02
293(2)
C8H6N4S2
222.31
293(2)
Crystal system
Space group
a (Å)
b (Å)
c (Å)
orthorhombic
Pbcn
monoclinic
P21/c
14.3078(3)
10.0923(2)
24.1358(4)
90
monoclinic
P21/c
14.2936(4)
10.0800(2)
24.1214(6)
90
monoclinic
P21/c
14.2375(3)
10.2000(2)
24.6616(7)
90
tetragonal
ꢀ
P421c
19.171(4)
11.667(2)
18.729(3)
90
13.3340(3)
13.3340(3)
10.8086(4)
90
a
(°)
b (°)
90
90
94.255(2)
90
3475.57(12)
4
1.400
3.123
94.207(2)
90
3466.03(15)
4
1.403
3.131
94.184(2)
90
3571.87(14)
4
1.451
0.819
90
90
c
(°)
V (Å3)
4189.1(13)
4
1.430
1921.72(9)
8
1.537
Z
q
l
(g cmꢁ3
(mmꢁ1
)
)
1.231
0.515
hmin < 2h < hmax
Data collected, Uniq. Data,
Independent reflections (Rint
2.04 < 2h < 24.99
4532, 3640
1758 (0.068)
0.0789, 0.2223, 1.06
3.1 < 2h < 62.1
11058, 5367
4729 (0.020)
0.0270, 0.0749, 1.03
3.1 < 2h < 62.4
11129, 5361
4872 (0.018)
2.9 < 2h < 29.3
46190, 8847
7627 (0.033)
0.0237, 0.0576, 1.06
3.1 < 2h < 25.0
5062, 1630
1473 (0.037)
)
R1, wR2 [I > 2
r
(I)], S
0.0284, 0.0787, 1.03
0.0263, 0.0546, 0.96
4.5. Saturation transfer difference 1H NMR experiments
pulses separated by a 1 ms delay. Off-resonance irradiation fre-
quency for the reference spectrum was applied at 30 ppm. Water
suppression was achieved with excitation sculpting [25]. Spectra
were zero filled twice and line broadening function of 1 Hz was
applied.
NMR samples for the saturation transfer difference experiments
were prepared in 99.9% D2O buffer containing 20 mM Tris (98%
D11), 7 mM (ND4)2SO4 (98% D8), 3.5 mM MgCl2 and 0.3 mM DTT
(98% D10), pD 9. Ligand concentration was 0.4 mM and the protein
concentration was 0.004 mM resulting in protein–ligand ratio of
1:100.
5. Computational details
The saturation transfer difference NMR experiments [22b] were
recorded on Varian 800 MHz spectrometer equipped with cold
probe with spectral width of 9058 Hz, 8192 complex data points
and 4000–7000 scans. Relaxation delay was set to 10 s. Selective
on-resonance irradiation frequency was set to 0.32 ppm with satu-
ration time of 0.4 s. In case of compound 3 saturation time of 2 s
was used to improve poor signal to noise ratio in STD spectrum.
Selective saturation was achieved by a train of 50 ms Gauss-shaped
Computational modelling of the inhibition effect of the com-
plexes through docking studies, was performed with the grid based
version of the MolDock algorithm [26a] as this is implemented in
Molegro Virtual Docker software package (www.molegro.com).
The three dimensional coordinates of lipoxygenase (LOX) (pdb ID:
1F8N) were obtained from the Protein Data Bank. (www.rcsb.org/
pdb). All solvent molecules were removed from the protein

G.K. Batsala et al. / Inorganica Chimica Acta 382 (2012) 146–157
157
(c) X.-Z. Ding, C.A. Kuszynski, T.H. El-Metwally, T.E. Adrian, Biochem. Biophys.
Res. Commun. 266 (1999) 392;
(d) G.P. Pidgeon, J. Lysaght, S. Krishnamoorthy, J.V. Reynolds, K. O’Byrne, D. Nie,
K.V. Honn, Cancer Metastasis Rev. 26 (2007) 503.
structure. Molecular structures of ligands were obtained by X-ray
crystallography. Preceding the docking however, all structures
were optimized under the quick PM3 parameterization scheme
[26b] to exclude lattice effects non applicable to our theoretical set-
up. The default parameters were used regarding charges, bonds or-
der and geometrical flexibility with no other constrains. The
docking space was an extensive spherical domain at the centre of
the enzyme and the final poses were sorted using the ‘‘reranking
score’’ scheme.
[12] (a) D. Li, W.-J. Shi, T. Wu, S.W. Ng, Acta Crystallogr., Sect. E: Struct. Rep. Online
60 (2004) m776;
(b) T.S. Lobana, P. Kaur, A. Castineiras, P. Turner, T.W. Failes, Struct. Chem. 19
(2008) 727;
(c) C.-X. Ruan, W.-J. Shi, Acta Crystallogr., Sect. E: Struct. Rep. Online 63 (2007)
m2412;
(d) P. Aslanidis, P. Karagiannidis, P.D. Akrivos, B. Krebs, M. Lage, Inorg. Chim.
Acta 254 (1997) 277.
[13] (a) S. Furberg, J. Solbakk, Acta Chem. Scand. 27 (1973) 2536;
(b) G.B. Jensen, G. Smith, D.S. Sagatys, P.C. Healy, J.M. White, Acta Crystallogr.,
Sect. E: Struct. Rep. Online 60 (2004) o2438.
Acknowledgments
[14] P. Strauch, W. Dietzsch, L. Golic, Z. Anorg. Allg. Chem. 623 (1997) 129.
[15] (a) S. Sculfort, P. Braunstein, Chem. Soc. Rev. 40 (2011) 2741;
(b) P. Pyykko, Chem. Rev. 97 (1997) 597.
[16] (a) S.M. Nelson, F.S. Esho, M.G.B. Drew, Chem. Commun. (1981) 388;
(b) I.F. Taylor Junior, M.S. Weininger, E.L. Amma, Inorg. Chem. 13 (1974) 2835;
(c) H.-G. Zhu, H. Cai, Y. Xu, Z. Yu, X.-Z. You, C.H.L. Kennard, J. Coord. Chem. 49
(1999) 75;
This research was carried out in partial fulfillment of the
requirements for the Master thesis of G.B. within the graduate pro-
gram of the Department of Chemistry under the supervision of
S.K.H., at the University of Ioannina, Greece.
(d) G.-H. Zhang, N.-Z. Wu, X.-L. Jin, P. Wang, H.-Y. Guo, Chin. J. Chem. 21 (2003)
40;
Appendix A. Supplementary material
(e) M. Belicchi-Ferrari, F. Bisceglie, E. Buluggiu, G. Pelosi, P. Tarasconi,
Polyhedron 28 (2009) 1160;
(f) R.K. Chadha, R. Kumar, D.G. Tuck, Can. J. Chem. 65 (1987) 1336;
(g) E.S. Raper, J.R. Creighton, J.D. Wilson, W. Clegg, A. Milne, Inorg. Chim. Acta
149 (1988) 265;
CCDC 820433 (1), 820431 (2), 820426 (3a), 820427 (3b),
820430 (4), 820429 (5), 820432 (6) and 820428 (pmt)2 contains
the supplementary crystallographic data for this paper. These data
can be obtained free of charge from The Cambridge Crystallo-
graphic Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.ica.2011.10.024.
(h) H. Xu, J.H.K. Yip, Inorg. Chem. 42 (2003) 4492.
[17] (a) M. Spescha, G. Rihs, Helv. Chim. Acta 76 (1993) 1219;
(b) S. Schneider, J.A.S. Roberts, M.R. Salata, T.J. Marks, Angew. Chem., Int. Ed. 45
(2006) 1733;
(c) Y. Agnus, R. Louis, R. Weiss, Chem. Commun. (1980) 867;
(d) R. Castro, M.L. Duran, J.A. Garcia-Vazquez, J. Romero, A. Sousa, E.E.
Castellano, J. Zukerman-Schpector, J. Chem. Soc., Dalton Trans. (1992) 2559;
(e) K. Johnson, J.W. Steed, J. Chem. Soc., Dalton Trans. (1998) 2601;
(f) Y.-D. Chen, L.-Y. Zhang, Y.-H. Qin, Z.-N. Chen, Inorg. Chem. 44 (2005) 6456;
J. Lang, K. Tatsumi, K. Yu, Polyhedron 15 (1996) 2127.
References
[1] T. Tsukihara, H. Aoyama, E. Yamashita, T. Tomizaki, H. Yamaguchi, K.
Shinzawa-Itoh, R. Nakashima, R. Yaono, S. Yoshikawa, Science 269 (1995)
1069.
[18] K. Lazarou, B. Bednarz, M. Kubicki, I.I. Verginadis, K. Charalabopoulos, N.
Kourkoumelis, S.K. Hadjikakou, Inorg. Chim. Acta 363 (2010) 763.
[19] (a) P.F. Barron, J.C. Dyason, P.C. Healy, L.M. Engelhardt, C. Pakawatchai, V.A.
Patrick, A.H. White, J. Chem Soc., Dalton Trans. (1987) 1099;
(b) K. Folting, J. Huffman, W. Mahoney, J.M. Stryker, K.G. Caulton, Acta
Crystallogr., Sect. C: Cryst. Struct. Commun. 43 (1987) 1490;
(c) T. Krauter, B. Neumuller, Polyhedron 15 (1996) 2851;
(d) V.G. Albano, P. Bellon, M. Sansoni, J. Chem. Soc., A (1971) 2420;
(e) A. Machado, G.N. ManzonideOliveira, H. Fenner, R.A. Burrow, Acta
Crystallogr., Sect. C: Cryst. Struct. Commun. 64 (2008) m233.
[20] M. Kubicki, S.K. Hadjikakou, M.N. Xanthopoulou, Polyhedron 20 (2001) 2179.
[21] I. Reva, L. Lapinski, M.J. Nowak, Chem. Phys. Lett. 467 (2008) 97.
[22] (a) M.N. Xanthopoulou, S.K. Hadjikakou, N. Hadjiliadis, M. Kubicki, S.
Karkabounas, K. Charalabopoulos, N. Kourkoumelis, T. Bakas, J. Organomet.
Chem. 691 (2006) 1780;
(b) M. Mayer, B. Meyer, J. Am. Chem. Soc. 123 (2001) 6108.
[23] (a) M.N. Xanthopoulou, S.K. Hadjikakou, N. Hadjiliadis, E.R. Milaeva, J.A.
Gracheva, V.-Y. Tyurin, N. Kourkoumelis, K.C. Christoforidis, A.K. Metsios, S.
Karkabounas, K. Charalabopoulos, Eur. J. Med. Chem. 43 (2008) 327;
(b) I. Ozturk, S. Filimonova, S.K. Hadjikakou, N. Kourkoumelis, V. Dokorou, M.J.
Manos, A.J. Tasiopoulos, M.M. Barsan, I.S. Butler, E.R. Milaeva, J. Balzarini, N.
Hadjiliadis, Inorg. Chem. 49 (2010) 488;
[2] F. Kubowitz, Biochem. Z. 299 (1938) 32.
[3] C.R. Dawson, M.F. Mallette, Adv. Protein Chem. 2 (1945) 179.
[4] (a) B.L. Vallee, W.E.C. Wacker, Proteins 5 (1970) 41. 83, 143;
(b) L. Banci, I. Bertini, F. Cantini, I.C. Felli, L. Gonnelli, N. Hadjiliadis, R.
Pierattelli, A. Rosato, P. Voulgaris, Nat. Chem. Biol. 2 (2006) 367.
[5] (a) T. Ottersen, L. Warner, K. Seffh, Inorg. Chem. 13 (1974) 1904;
(b) L.G. Warner, T. Ottersen, K. Seff, Inorg. Chem. 13 (1974) 2819;
(c) C.J. Simmons, M. Lundeen, K. Seff, Inorg. Chem. 18 (1979) 3444;
(d) T. Wallace, J. Org. Chem. 31 (1966) 3071;
(e) P. Kumar, M. Gusain, R. Nagarajan, Inorg. Chem. 50 (2011) 3065.
[6] (a) S.K. Hadjikakou, C.D. Antoniadis, P. Aslanidis, P.J. Cox, A.C. Tsipis, Eur. J.
Inorg. Chem. (2005) 1442;
(b) P. Aslanidis, P.J. Cox, P. Karagiannidis, S.K. Hadjikakou, C.D. Antoniadis, Eur.
J. Inorg. Chem. (2002) 2216;
(c) P. Karagiannidis, S.K. Hadjikakou, P. Aslanidis, A. Huntas, Inorg. Chim. Acta
178 (1990) 27;
(d) S.K. Hadjikakou, P. Aslanidis, P.D. Akrivos, P. Karagiannidis, B. Kojic-Prodic,
M. Luic, Inorg. Chim. Acta 197 (1992) 31;
(e) P. Aslanidis, S.K. Hadjikakou, P. Karagiannidis, B. Kojic-Prodic, M. Luic,
Polyhedron 12 (1994) 3119.
(c) V.I. Balas, S.K. Hadjikakou, N. Hadjiliadis, N. Kourkoumelis, M.E. Light, M.
Hursthouse, A.K. Metsios, S. Karkabounas, Bioinorg. Chem. Appl. (2008) Article
ID 654137.
[7] (a) P.D. Akrivos, S.K. Hadjikakou, P. Karagiannidis, D. Mentzafos, A. Terzis,
Inorg. Chim. Acta 206 (1993) 163;
(b) S.K. Hadjikakou, P.D. Akrivos, P. Karagiannidis, D. Mentzafos, A. Terzis,
Inorg. Chim. Acta 210 (1993) 27.
[8] (a) B.-J. Liaw, T.S. Lobana, Y.-W. Lin, J.-C. Wang, C.W. Liu, Inorg. Chem. 44
(2005) 9921;
(b) J.T. Gill, J.J. Mayerle, P.S. Welcker, D.F. Lewis, D.A. Ucko, D.J. Barton, D.
Stowens, S.J. Lippard, Inorg. Chem. 15 (1976) 1155.
[9] S.S. Batsanov, Inorg. Mater. 37 (2001) 871.
[24] (a) Oxford Diffraction, CRYSALIS CCD and CRYSALIS RED, version p171.29.2,
Oxford Diffraction Ltd., Abingdon, Oxford, England, (2006);
(b) CrysAlis RED, Oxford Diffraction Ltd., Version 1.171.31.5 (release 28-08-
2006 CrysAlis171.NET);
(c) G.M. Sheldrick, SHELXS97 Program for Crystal Structure solution, University
of Goettingen, Germany, (1997);
(d) G.M. Sheldrick, Acta Crystallogr., Sect. A46 (1990) 467;
(e) G.M. Sheldrick, SHELXL-97, Program for the Refinement of Crystal Structures,
University of Gottingen, Gottingen, Germany, (1997).
[25] (a) H.L. Hwang, A.J. Shaka, J. Magn. Reson. Ser. A 112 (1995) 275;
(b) C. Dalvit, J. Biomol. NMR 11 (1998) 437.
[10] (a) C.-H. Li, S.C.F. Kui, I.H.T. Sham, S.S.-Y. Chui, C.-M. Che, Eur. J. Inorg. Chem.
(2008) 2421;
(b) P.C. Ford, E. Cariati, J. Bourassa, Chem. Rev. 99 (1999) 3625;
(c) V.W.-W. Yam, K.K.-W. Lo, Chem. Soc. Rev. 28 (1999) 323.
[11] (a) B. Samuelsson, S.E. Dahlen, J. Lindgren, C.A. Rouzer, C.N. Serhan, Science
237 (1987) 1171;
}
}
[26] (a) R. Thomsen, M.H. Christensen, J. Med. Chem. 49 (2006) 3315;
(b) J.J.P. Stewart, J. Comput. Chem. 10 (1989) 210.
(b) M.J. Knapp, J.P. Klinman, Biochemistry 42 (2003) 11466;