Efficient synthesis and evaluation of bis-pyridinium/bis-quinolinium metallosalophens as antibiotic and antitumor candidates

Article abstract of DOI:10.1016/j.molstruc.2016.08.059

Inspired with the pharmacological diversity of salophens and in our endeavor to explore a new strategy which may conflict the invasion of drug resistance, we report herein efficient synthetic routes for the synthesis of new RO-salophen(Cl), pyridinium/quinolinium-based salophens (3a-e) and metallosalophens (4a-j). These new architectures have been structurally characterized by elemental and spectral analysis as well pharmacologically evaluated for their in?vitro antimicrobial, against a common panel of pathogenic bacterial and fungal strains, and anticancer activities against human colon carcinoma (HCT-116) cell lines. Antimicrobial assay results revealed that all tested compounds exhibited moderate to superb broad-spectrum efficacy in comparison to the standard antibiotic with a preferential ability to perform as a fungicides than to act as bactericides. Noteworthy, VO(II)-salophens are more effective in reduction HCT-116?cell viability than Cu(II)-salophens. For example, VO(II)-salophen3 (4f) (IC₅₀?=?2.13?μg/mL) was ca. 10-fold more efficient than Cu(II)-salophen3 (4e) (IC₅₀?=?20.30?μg/mL).

Full text of DOI:10.1016/j.molstruc.2016.08.059

Journal of Molecular Structure 1128 (2017) 162e173
Contents lists available at ScienceDirect
Journal of Molecular Structure
journal homepage: http://www.elsevier.com/locate/molstruc
Efficient synthesis and evaluation of bis-pyridinium/bis-quinolinium
metallosalophens as antibiotic and antitumor candidates
, c,
Reda F.M. Elshaarawy a *, Ibrahim M. Eldeen b, Eman M. Hassan a
a Chemistry Department, Faculty of Science, Suez University, 43518 Suez, Egypt
b Department of Chemistry, Faculty of Science, Port Said University, Port Said, Egypt
c
€
Institut für Anorganische Chemie und Strukturchemie, Heinrich-Heine Universitat Düsseldorf, 40204 Düsseldorf, Germany
a r t i c l e i n f o
a b s t r a c t
Article history:
Inspired with the pharmacological diversity of salophens and in our endeavor to explore a new strategy
which may conflict the invasion of drug resistance, we report herein efficient synthetic routes for the
synthesis of new RO-salophen(Cl), pyridinium/quinolinium-based salophens (3a-e) and metal-
losalophens (4a-j). These new architectures have been structurally characterized by elemental and
spectral analysis as well pharmacologically evaluated for their in vitro antimicrobial, against a common
panel of pathogenic bacterial and fungal strains, and anticancer activities against human colon carcinoma
(HCT-116) cell lines. Antimicrobial assay results revealed that all tested compounds exhibited moderate
to superb broad-spectrum efficacy in comparison to the standard antibiotic with a preferential ability to
perform as a fungicides than to act as bactericides. Noteworthy, VO(II)-salophens are more effective in
Received 8 June 2016
Received in revised form
9 August 2016
Accepted 21 August 2016
Available online 26 August 2016
Keywords:
Salophens
Metallosalophens
Pyridinium
Antimicrobial
Anticancer
reduction HCT-116 cell viability than Cu(II)-salophens. For example, VO(II)-salophen3 (4f) (IC50 ¼ 2.13
mg/
mL) was ca. 10-fold more efficient than Cu(II)-salophen3 (4e) (IC50 ¼ 20.30
m
g/mL).
© 2016 Elsevier B.V. All rights reserved.
1. Introduction
with various oxidation states [6] which have diverse applications in
several fields including catalysis [7], antimicrobial [8,9], anticancer
[10], sensors [11], magnetic [12] and non-linear optical (NLO) ap-
plications [13].
Recently, the relentless growth of multidrug-resistant (MDR)
becomes a serious chemotherapeutic issue [1,2] due to a lack of
patient response to the drug and the outbreak of the disease.
Hence, there is urgent call to explore a novel strategy to negate this
drug resistance. Among proposed strategies, development of new
generation of pharmacological agents with innovative modes of
action that able to nullify the current resistance mechanisms [3,4]
are at the forefront of attention for many biomedical researchers.
Since the preparation of the N-N'-bis (salicylidene) ethylenedi-
amine and its copper(II)/nickel(II) complexes [5] coupled with the
discovery of new generation of chelating ligands, salen Schiff-bases,
many chemists have endeavored to synthesize a wide range of
salens and salophens ligands due to their ability to coordinate to a
wide range of metal ions to form metallosalens/metallosalophens
Among metal ions, much attention has been paid to copper(II)
and oxovanadium(IV) ions because of their admirable structural
and pharmacological features, in particular their complexes. Cop-
per is an essential element for our life as it is played a critical role in
diverse of Cu-dependent enzymatic process that are the keys fea-
tures in many biological systems [14]. Moreover, copper(II) com-
plexes have been found to exhibit multiple pharmacological
activities such as antiulcer [15], anti-amoebic [16], anti-diabetic
[17] anticonvulsant [18], anti-inflammatory [19], antimicrobial
[20] and antitumor [21]. Notably, vanadyl complexes containing N-
donor chelating ligands have shown very interesting biochemical
and pharmacological efficacies such as insulin-mimetic profile [22],
antiparasitic [23] and antitumor activities [24].
In the race of fabrication of new pharmaceutical drugs, ionic
liquids (ILs) have attracted a considerable attention due to their
amphiphilic nature which may realizes considerable enhancements
in controlling the aqueous solubility, pharmacokinetic properties,
stability, polymorphism of drug, delivery options, or even
customized pharmaceutical cocktails [25].
* Corresponding author. Permanent address: Chemistry Department, Faculty of
Science, Suez University, 43518 Suez, Egypt. Current address: Institut für Anorga-
€
nische Chemie und Strukturchemie, Heinriche-Heine-Universitat Düsseldorf, D-
40225 Düsseldorf, Germany
E-mail addresses: reda_elshaarawi@science.suez.edu.eg, Reda.El-Shaarawy@
uni-duesseldorf.de (R.F.M. Elshaarawy).
http://dx.doi.org/10.1016/j.molstruc.2016.08.059
0022-2860/© 2016 Elsevier B.V. All rights reserved.

R.F.M. Elshaarawy et al. / Journal of Molecular Structure 1128 (2017) 162e173
163
Interestingly, antimicrobial assessments of pyridinium and
quinolinium ionic liquid (IL)-based architectures revealed signifi-
cant broad-spectrum biocidal activities [26]. Moreover, many ionic
liquids display biocidal efficacy against Gram-positive/-negative
bacteria, fungi and algae [27,28].
In resumption our ongoing programs directed toward the
development of novel potent and therapeutic agents [28,29] we
report herein a synthetic strategy and in vitro biological (antimi-
crobial and anticancer) evaluation of new pyridinium and
quinolinium-based salophen-type ligands and their metal com-
plexes (Scheme 1) which may allow us to develop novel therapeutic
strategy to combat antibiotic resistance and offer potent anticancer
agents.
Intersetingly, the possible structural and geometrical features of
our metallosalophen complexes could be identified by comparing
with the spectral studies of the related salen and salophen com-
plexes isolated in the former work [30,31]. As the crystallographic
data collected from X-ray diffraction analysis for Cu(II) salophen-
and salen-type ligands [30] reveal that the central Cu(II) ion was
situated in a slightly distorted square-planar environment with
CuN2O2 coordination core. On other hand, X-ray crystallography
obtained from VO(II)-salophens demonstrate that the tetradentate
(ONNO) salophen ligand coordinates the vanadium(IV) ion in four
equatorial sites while the terminal O atom of vanadyl ion occupies
the axial position to form a distorted square pyramidal geometry
[31].
Scheme 1. Proposed salophen-type Schiff bases that used in this work.
nitrogen laser pulsing at a repetition rate of 10 Hz. The 2 þ charge
assignment of ions in ESI-MS was confirmed by the m/z ¼ 0.5 dif-
ference between the isotope peaks (x, xþ1, xþ2). The molar con-
ductances of 10ꢀ3 mol/L solution of various compounds have been
measured at ambient temperature with a digital conductivity me-
ter (S30 SevenEasy™ conductivity, Mettler-Toledo Electronics, LLC,
Polaris Parkway, Columbus). The overall accuracy of the conduc-
tance measurements was found to be 0.2%.
2. Experimental
2.1. Materials
Chemicals were obtained from the following suppliers and used
without further purification: salicylaldehyde (Sal), quinoline (Qn),
2-methylpyridine (2-picoline, 2-MePy) (SigmaeAldrich), para-
formaldehyde ((CH2O)n) (Roth), 4-Chloro-o-phenylenediamine (4-
Cl-Phen) and isoquinoline (iso-Qn) (Alfa Aesar), anhydrous zinc
2.3. Synthesis of salicylaldehyde ionic liquids (Sal-ILs, 2a-c)
To a vigorously stirred solution of N-heterocyclic derivatives
(19.50 mmol) in dry toluene (25 mL) at room temperature was
added a solution of 5-chloromethyle salicylaldehyde 1 (4.15 g,
19.50 mmol) in dry toluene (50 mL), drop-wise over 30 min, under
nitrogen atmosphere. The resulting solution was stirred under ni-
trogen atmosphere at 60 ꢁC for 24 h. After cooling, the isolated
products were washed intensively with 5 ꢂ 5 mL dry toluene,
several with ether (5 ꢂ 10 mL), to remove the unreacted materials,
and dried under vacuum to give the desired products which used
for the following preparations without further purification. Sam-
ples of the isolated products were characterized as follows;
chloride (ZnCl2) (GRüssing GmbH), o-phenylenediamine (Phen) and
copper(II) chloride dihydrate (CuCl2$2H2O), (ADWIC) and vanadyl
sulfate pentahydrate (VOSO4$5H2O) (VWR). 5-chloromethyl-sali-
cylaldehyde (1) was synthesized as described in the literature [28]
and obtained as white needles (73.0% Yield). 1H NMR (200 MHz,
CDCl3)
d (ppm): 11.12 (s, 1H, AreOH) 9.93 (s, 1H, AreHC]O), 7.57
(m, 2H, 2 x AreH), 7.00 (d, 1H, JHH ¼ 8.34 Hz, AreH), 4.58 (s, 2H,
CH2eAr).
2.2. Instrumentation
2.3.1. 3-(3-Formyl-4-hydroxybenzyl)-2-methylpyridinium chloride
(2a)
Elemental analyses C, H, N, were performed with a Per-
kineElmer 263 elemental analyzer. FT-IR spectra were recorded on
Obtained as pale yellow solid in 91% yield. FTIR (KBr, cmꢀ1):
a
BRUKER Tensor-37 FT-IR spectrophotometer in the range
400e4000 cmꢀ1 as KBr disc in the 4000e550 cmꢀ1 region with
2 cmꢀ1 resolution. For signal intensities the following abbreviations
were used: br (broad), sh (sharp), w (weak), m (medium), s
(strong), vs (very strong). UV/Vis spectra were measured at 25 ꢁC in
DMSO (10ꢀ3 mol/L) on a Shimadzu UV-2450 spectrophotometer
using quartz cuvettes (1 cm). NMR-spectra were obtained with a
Bruker Avance DRX200 (200 MHz for 1H) or Bruker Avance DRX500
(125 MHz for 13C) spectrometer with calibration to the residual
proton solvent signal in DMSO-d6 (1H NMR: 2.52 ppm, 13C NMR:
39.5 ppm), CDCl3 (1H NMR: 7.26 ppm, 13C NMR: 77.16 ppm) against
3385 (m, br,
nCH2), 1661 (vs, sh, n(C
bend)), 1149 (s, sh,
(HeC]C þ HeC]N)bend, Py). 1H NMR (200 MHz,
CDCl3) (ppm): 10.83 (s, 1H, AreOH) 10.30 (s, 1H, AreHC]O), 9.15
n
(OeH)), 2959 (m, sh,
n
asym(CeH), CH3), 2884 (m, sh,
]O)), 1573, 1485, 1455 (s, sh, n(C
]CAr þ CeH-
n
d
(d, J ¼ 2.10 Hz, 1H, PyeH), 8.68 (m, 2H, 2 x PyeH), 7.84 (d, 1H,
J ¼ 1.39 Hz, PyeH), 7.75 (d, JHH ¼ 1.41 Hz,1H, AreH), 7.38 (m, 2H, 2 x
AreH), 5.45 (s, 2H,eCH2eAr), 2.73 (s, 3H, CH3). 13C NMR (75 MHz,
CDCl3)
d (ppm): 163.88, 160.76, 151.06, 142.28, 136.95, 135.54,
133.24, 131.19, 129.58, 127.86, 123.77, 64.61 and 25.29. ESI MS: In
positive mode peaks at m/z 228.10 (100%, [C14H14NO2]þ, MꢀCl)
a.m.u.
TMS (
d
¼ 0.00 ppm) for 1H and 13C NMR. Multiplicities of the signals
were specified s (singlet), d (doublet), t (triplet), q (quartet) or m
(multiplet). The mass spectra were acquired in the linear mode for
positive ions on a UHR-QTOF maXis 4G (Bruker Daltonics) and
2.3.2. 3-(3-Formyl-4-hydroxybenzyl)-quinolinium chloride (2b)
Obtained as dark yellow solid in 86% yield. FTIR (KBr, cmꢀ1):
B
RUKER Ultraflex MALDI-TOF instrument equipped with a 337 nm
3369 (m, br, n(OeH)), 1666 (vs, sh, n(C]O)), 1574, 1487, 1453 (s, sh,

164
R.F.M. Elshaarawy et al. / Journal of Molecular Structure 1128 (2017) 162e173
n(C
]
CAr þ CeHbend)), 1156 (s, sh,
n
(HeC]C þ HeC]N)bend, Py). 1H NMR
J1 ¼ J2 ¼ 8.10 Hz, 1 H, AreH), 4.09 (q, 4 H, 2 x OeCH2), 1.37 (t,
(200 MHz, CDCl3)
d
(ppm): 11.22 (s, 1H, AreOH) 10.59 (s, 1H,
J1 ¼ J2 ¼ 7.00 Hz, 6 H, 2 x OeCH2CH3). 13C NMR (125 MHz, DMSO-d6)
AreHC]O), 9.14 (d, J ¼ 7.31 Hz, 1H, PyeH), 8.70 (m, 2H, 2 x PyeH),
8.51 (m, 2H, 2 x AreH), 8.26 (m, 2H, 2 x AreH), 7.59 (s, 1H, AreH),
7.19 (m, 2H, 2 x AreH), 5.58 (s, 2H,eCH2eAr). 13C NMR (75 MHz,
d (ppm): 160.93, 156.13, 151.01, 150.89, 148.64, 148.58, 143.04,
141.99, 132.00, 130.19, 128.53, 124.24, 124.11, 120.89, 120.06, 119.81,
119.77, 118.28, 118.02, 116.09, 65.13 and 15.15. EI-MS: m/z (intensity)
438.8 (100%) ([C24H23ClN2O4]þ
,
Mþꢃ). Anal. Calcd. (%) for
ꢃ
CDCl3)
d
(ppm): 196.13, 162.74, 153.86, 148.03, 140.89, 138.98,
136.58, 135.77, 132.37, 131.61, 129.34, 128.18, 127.24, 124.78, 122.22,
119.58 and 65.31. ESI MS: In positive mode peaks at m/z 264.23
(69%, [C17H14NO2, MꢀCl]þ) a.m.u.
C
24H23ClN2O4 (M ¼ 438.90 g/mol): C, 65.68; H, 5.28; N, 6.38. Found
(%): C, 65.59; H, 5.29; N, 6.35. Conductivity ¼ 16 S/cm.
m
2.4.3. N,N0-Bis-(5-(chlorido-2-methylpyridinium)-salicylidene)-o-
phenylenediimine (H2salophen3, 3c)
2.3.3. 3-(3-Formyl-4-hydroxybenzyl)-isoquinolinium chloride (2c)
Obtained as dark yellow solid in 89% yield. FTIR (KBr, cmꢀ1):
Obtained as yellowish brown solid in 74.2% yield; mp ¼ 212 ꢁC.
3419 (m, br,
n(C
CAr þ CeHbend)), 1155 (s, sh,
(200 MHz, DMSO-d6) (ppm): 10.98 (s, 1 H, AreOH), 10.33 (s, 1 H,
n
(OeH)), 1655 (vs, sh, n(C
]
O)), 1581, 1485, 1453 (s, sh,
FT-IR (KBr, cmꢀ1): 3389 (s, br,
n(OeH)), 3050 (s, br, n(CeH), Ar), 2930
]
n
(HeC]C þ HeC]N)bend, Py). 1H NMR
(s, br, n(CH3)), 1613 (v, sh, n(C
sh, n(C CAr þ CeHbend)), 1271 (s, sh,
HeC]N)bend, Py), 894 (w, br), 822 (m, sh), 749 (s, sh), 581 (m, br). 1H
NMR (200 MHz, DMSO-d6) (ppm): 13.79 (s, 2 H, 2 x AreOH), 9.22
]N), azomethine), 1504, 1467, 1388 (s,
d
]
n
(AreO)), 1163 (s, sh, (HeC]C þ
n
AreHC]O), 9.61 (d, J ¼ 6.76 Hz,1 H, PyeH), 8.78 (m, 2 H, 2 x PyeH),
8.49 (d, J ¼ 7.1 Hz, 1 H, AreH), 8.13 (d, J ¼ 6.98 Hz, 1 H, AreH), 7.41
(m, 3H, 3 x AreH), 7.15 (m, 1H, AreH), 5.38 (s, 2H, N(3)
d
(d, J ¼ 4.3 Hz, 2H, 2 x PyeH), 8.78 (s, 2 H, 2 x HeC]N), 8.53 (t,
J ¼ 7.9 Hz, 2H, 2 x PyeH), 8.20 (d, J ¼ 8.2 Hz, 2H, 2 x PyeH), 7.95 (d,
J ¼ 8.2 Hz, 2H, 2 x PyeH), 7.80e7.71 (m, 2H, 2 x AreH), 7.49 (d,
J ¼ 7.2 Hz, 4H, 4 x AreH), 7.31e7.23 (m, 2H, 2 x AreH), 7.16 (dd,
J ¼ 11.9, 8.4 Hz, 2H, 2 x AreH), 5.35 (s, 4H, 2 x eCH2eAr), 2.97 (s, 6H,
eCH2eAr).13C NMR (125 MHz, DMSO-d6)
d (ppm): 196.09, 161.17,
154.02, 148.22, 140.87, 138.64, 136.23, 135.12, 132.72, 131.81, 128.78,
127.22, 123.99, 122.21, 120.10and 64.16. ESI MS: In positive mode
peaks at m/z 264.10 (58%, [C17H14NO2, MꢀCl]þ) a.m.u.
2 x CH3). 13C NMR (125 MHz, DMSO-d6)
d (ppm): 171.67, 160.07,
2.4. Synthesis of salophen-type ligands (3a-e)
157.52, 155.93, 153.90, 146.32, 145.99, 133.26, 130.63, 128.89, 127.32,
126.25, 124.19, 122.41, 118.82, 117.78, 57.60, and 25.21. ESI-MS: m/z
(intensity) 564.05 (<5%) (C34H32ClN4O2, [MꢀCl]þ), 529.10 (57.38%)
(C34H32N4O2, [Mꢀ2Cl]2þ). Anal. Calcd. (%) for C34H32Cl2N4O2
(M ¼ 599.55 g/mol): C, 68.11; H, 5.38; N, 9.34. Found (%): C, 68.02;
To a stirred solution of the respective salicylaldehyde or Sal-IL
(0.04 mol, two equivalents) in absolute ethanol (60 mL) was
added, dropwise, an ethanolic solution (10 mL) of aromatic diamine
(Phen or 4-Cl-Phen) (0.02 mol, one equivalent). The reaction
mixture was then stirred under reflux for 2 h. Afterwards, the
mixture was cooled to room temperature or in ice, and the products
formed were collected by filtration, washed with cold absolute
ethanol and recrystallized from ethanol/ethyl acetate (1:3 v/v)
mixture. The products were dried in a desiccator over (P2O5).
Samples of the isolated solids were characterized as follows;
H, 5.43; N, 8.99. Conductivity ¼ 95
mS/cm.
2.4.4. N,N0-Bis-(5-(chlorido-quinolinium)-salicylidene)-o-
phenylenediimine (H2salophen4, 3d)
Obtained as deep brown solid in 70.8% yield; mp > 300 ꢁC. FTIR
(KBr, cmꢀ1): 3379 (s, br,
n
(OeH)), 3190 (m, sh,
sym(CeH), Ar), 2924 (s, br, (CeH)), 1601 (s, sh, n(C
methine), 1497, 1456, 1377 (s, sh, n(C CAr þ CeHbend)), 1273 (s, sh,
(AreO)), 1157 (s, sh, (HeC]C þ HeC]N)bend, Py), 972 (m, br), 871 (m,
sh), 744 (vs, sh), 621 (w, br), 579 (w, br). 1H NMR (500 MHz, DMSO-
d6)
n
asym(CeH), Ar), 3051
(m, sh,
n
n
]N), azo-
]
2.4.1. N,N0-Bis(3-methoxysalicylidene)-4-chloro-o-
phenylenediamine (H2salophen1, 3a)
n
n
Obtained as brown solid in 73.9% yield; mp 203 ꢁC. FT-IR (KBr,
d
(ppm): 13.90 (s, 2H, 2 x AreOH), 9.99 (d, J ¼ 4.6 Hz, 2H, 2 x
cmꢀ1): 3512 (m, br,
n
(OeH)), 3282 (m, sh,
sym(CeH), Ar), 2976 (m, sh, n(CH3)), 1616 (s, sh, n(C
thine), 1598, 1477, 1390 (s, sh, n(C CeHbend)), 1321 (m, sh,
(CeH)), 1249 (s, sh, (AreO)), 1054 (s, sh), 931 (m, sh), 740 (m, sh),
656 (m, sh), 597 (m, br), 500 (m, sh), 434 (m, sh). 1H NMR (300 MHz,
DMSO-d6) (ppm): 12.69 (s, 2 H, 2 x AreOH), 8.95 (s, 2 H, 2 x HeC]
n
asym(CeH), Ar), 3059 (m,
PyeH), 9.15 (t, J ¼ 7.8 Hz, 2H, 2 x PyeH), 8.83 (s, 2H, 2 x HeC]N),
8.60e8.48 (m, 4 H, 4 x AreH), 8.33 (d, J ¼ 7.9 Hz, 2H, 2 x PyeH), 8.10
(t, J ¼ 6.8 Hz, 2H, 2 x AreH), 7.95e7.80 (m, 4 H, 4 x AreH), 7.64e7.48
(m, 3 H, 3 x AreH), 7.31 (d, J ¼ 6.7 Hz, 2H, 2 x AreH), 7.14 (d,
J ¼ 8.4 Hz, 2H, 2 x AreH), 7.03e6.96 (m, 1 H, AreH), 6.06 (s, 4H, 2 x
sh,
n
]N), azome-
]
CAr
þ
n
n
d
eCH2eAr). 13C NMR (125 MHz, DMSO-d6)
d (ppm): 163.58, 160.47,
N), 7.52 (d, J ¼ 8.08 Hz, 4 H, 4 x AreH), 7.20 (d, J ¼ 7.83 Hz, 3 H, 3 x
157.49, 155.33, 153.56, 146.32, 145.99, 140.28, 136.17, 133.26, 131.09
130.63, 128.89, 127.32, 126.25, 124.19, 121.41, 118.93, 118.46, 117.81
and 63.02. ESI-MS: m/z (intensity) 536.10 (12.11%) (C40H32ClN4O2,
[MꢀCl]þ), 600.56 (61.23%) (C40H32ClN4O2, [Mꢀ2Cl]2þ). Anal. Calcd.
(%) for C40H32Cl2N4O2 (M ¼ 671.61 g/mol): C, 71.53; H, 4.80; N, 8.34.
AreH), 6.92 (s, br, 2 H, 2 x AreH), 3.82 (s, 6 H, 2 x OeCH3). 13C NMR
(125 MHz, DMSO-d6)
d (ppm): 160.83, 155.83, 151.05, 150.96,
148.28, 143.76, 141.60, 132.03, 127.58, 124.24, 124.10, 121.72, 120.06,
119.81, 119.77, 119.05, 119.02, 116.28, 116.09 and 56.15. EI-MS: m/z
(intensity) 410.00 (100%) ([C22H19ClN2O4]þꢃ, Mþꢃ). Anal. Calcd. (%)
for C22H19ClN2O4 (M ¼ 410.85 g/mol): C, 64.31; H, 4.66; N, 6.82.
Found (%): C, 71.39; H, 4.86; N, 8.31. Conductivity ¼ 128
mS/cm.
Found (%): C, 64.24; H, 4.69; N, 6.69. Conductivity ¼ 23
mS/cm.
2.4.5. N,N0-Bis-(5-(chlorido-isoquinolinium)-salicylidene)-o-
phenylenediimine (H2salophen5, 3e)
2.4.2. N,N0-Bis(3-ethoxysalicylidene)-4-chloro-o-phenylenediamine
(H2salophen2, 3b)
Obtained as brown solid in 73.4% yield; mp > 300 ꢁC. FTIR (KBr,
cmꢀ1): 3371 (s, br,
n
n
(OeH)), 3151 (m, sh,
sym(CeH), Ar), 2970 (s, br, (CeH)), 1640 (s, sh, azomethine), 1616 (s,
N)), 1512, 1470, 1396 (s, sh, n(C CAr þ CeHbend)), 1280 (s, sh,
(HeC]C þ HeC]N)bend, Py), 1018 (m, sh), 980
(w, br), 879 (m, sh), 829 (s, sh), 756 (vs, sh), 648 (w, br), 582 (w, br),
475 (m, sh). 1H NMR (500 MHz, DMSO-d6)
(ppm): 13.88 (s, 2H, 2 x
nasym(CeH), Ar), 3020 (m, sh,
Obtained as orange solid in 83.7% yield; mp > 300 ꢁC. FT-IR (KBr,
n
cmꢀ1): 3430 (m, br,
n
n
(OeH)), 3131 (m, sh,
sym(CeH), Ar), 2940 (m, sh, n(CH3)), 1613 (s, sh, n(C
1575,1463,1409 (s, sh, n(C CAr þ CeHbend)),1252 (s, sh,
(m, sh), 969 (s, sh), 855 (m, sh), 733 (m, sh), 580 (w, br), 437 (w, br).
1H NMR (300 MHz, DMSO-d6)
(ppm): 13.17 (s, 2 H, 2 x Ar-OH),
n
asym(CeH), Ar), 3074 (m, sh,
N), azomethine),
(AreO)),1081
sh, n(C
]
]
]
n(AreO)), 1157 (s, sh, n
]
n
d
d
AreOH), 10.38 (s, 2H, 2 x PyeH), 9.31 (d, J ¼ 5.1 Hz, 2H, 2 x PyeH),
8.87 (s, 2H, 2 x HeC]N), 8.71e8.57 (m, 4 H, 4 x AreH), 8.36 (d,
J ¼ 7.7 Hz, 2H, 2 x PyeH), 8.12 (t, J ¼ 7.1 Hz, 2H, 2 x AreH), 7.00e7.85
(m, 4 H, 4 x AreH), 7.83e7.76 (m, 2 H, 2 x AreH), 7.52 (d, J ¼ 6.9 Hz,
8.91 (s, 2 H, 2 x HeC]N), 7.72 (d, J ¼ 5.90 Hz, 2 H, 2 x AreH), 7.62 (t,
J1 ¼ J2 ¼ 8.40 Hz, 2 H, 2 x AreH), 7.46e7.34 (m, 1 H, AreH),
7.33e7.21 (m, 2 H, 2 x AreH), 7.11e7.03 (m, 1 H, AreH), 6.93 (t,

R.F.M. Elshaarawy et al. / Journal of Molecular Structure 1128 (2017) 162e173
165
2H, 2 x AreH), 7.33 (d, J ¼ 8.1 Hz, 2H, 2 x AreH), 7.05e6.95 (m, 2 H, 2
x AreH), 6.10 (s, 4H, 2 x eCH2eAr). 13C NMR (125 MHz, DMSO-d6)
(ppm): 164.54, 160.84, 156.01, 153.78, 152.13, 147.78, 145.99,
2.5.5. [Cu(salphen3)]·H2O (4e)
Obtained as dirty green solid in 87.3% yield; mp 295 ꢁC. FT-IR
(KBr, cmꢀ1): 3421 (s, br,
(OeH)), 3255 (m, sh, (CeH), Ar), 2963 (m,
sh, n(CH3)), 1619 (s, sh, n(C N), azomethine), 1469, 1319 (s, sh,
n(C (AreO)), 556 (m, sh, (CueN)), 440
CAr þ CeHbend)), 1264 (s, sh,
(m, sh,
([C34H30ClCuN4O2]þ,
d
n
n
140.28, 136.17, 132.98, 131.09 130.63, 128.89, 127.35, 126.25, 124.22,
122.63, 119.76, 118.46, 119.05 and 62.41. ESI-MS: m/z (intensity)
536.11 (8.90%) (C40H32ClN4O2, [MꢀCl]þ), 600.50 (66.14%)
(C40H32ClN4O2, [Mꢀ2Cl]2þ). Anal. Calcd. (%) for C40H32Cl2N4O2
(M ¼ 671.61 g/mol): C, 71.53; H, 4.80; N, 8.34. Found (%): C, 71.50; H,
]
]
n
n
n
(CueO)). ESI-MS: m/z (intensity) 625.90 (89.09%)
[MꢀCl]2þ),
590.00
(53.13%)
([C34H30CuN4O2]2þ, [Mꢀ2Cl]2þ). Anal. Calcd. (%) for C34H30Cl2Cu-
N4O2$H2O (M ¼ 679.09 g/mol): C, 60.13; H, 4.75; N, 8.25. Found (%):
4.83; N, 8.32. Conductivity ¼ 53
mS/cm.
C, 59.98; H, 4.83; N, 8.18. Conductivity ¼ 46
mS/cm.
2.5. General procedure for the preparation H2salophens complexes
2.5.6. [VO(salphen3)]·H2O (4f)
A hot (60 ꢁC) methanolic solution (5 mL) of appropriate metal
salt (0.664 mmol) was added to a hot (60 ꢁC) solution of H2salo-
phens 3a-e (0.664 mmol) in methanol (15 mL). Then, the reaction
mixture was stirred under reflux temperature for 3 h. After that, the
isolated complexes were collected by filtration from the hot solu-
tions, washed with hot methanol (3 ꢂ 3 mL) and diethyl ether
(3 ꢂ 3 mL) thereafter dried in air. Samples of the isolated solids
were characterized as follows;
Obtained as black solid in 58.9% yield; mp > 300 ꢁC. FT-IR (KBr,
cmꢀ1): 3391 (s, br,
n(CH3)), 1620 (s, sh, n(C
n(C
CAr þ CeHbend)), 1265 (s, sh,
sh, (VeN)), 468 (m, sh, n(VeO)). ESI-MS: m/z (intensity) 629.00
n
(OeH)), 3144 (m, sh,
N), azomethine), 1555, 1465, 1404 (s, sh,
(AreO)), 976 (m, sh, n(V O)), 605 (m,
n(CeH), Ar), 2925 (m, sh,
]
]
n
]
n
(34.18%) ([C34H30ClN4O3V]þ, [MꢀCl]2þ), 593.50 (69.89%)
([C34H30N4O3V]2þ
,
[Mꢀ2Cl]2þ).
Anal.
Calcd.
(%)
for
C34H30Cl2N4O3V$H2O (M ¼ 682.49 g/mol): C, 59.83; H, 4.73; N, 8.21.
Found (%): C, 60.01; H, 4.68; N, 8.17. Conductivity ¼ 61
mS/cm.
2.5.1. [Cu(salophen1)]·H2O (4a)
Obtained as brown solid in 82.8% yield; mp 295 ꢁC. FT-IR (KBr,
2.5.7. [Cu(salphen4)]·H2O (4g)
cmꢀ1): 3452 (s, br,
n
(OeH)), 3051 (m, sh,
n(CH3)), 1605 (s, sh, n(C N), azomethine), 1539, 1443, 1377 (s, sh,
n(C (AreO)), 528 (m, sh, (CueN)), 444
CAr þ CeHbend)), 1242 (s, sh,
n
(CeH), Ar), 2931 (m, sh,
Obtained as dark greenish blue solid in 71.3% yield; mp > 300 ꢁC.
]
FT-IR (KBr, cmꢀ1): 3437 (s, br,
(m, sh, (CeH)), 1608 (s, sh, n(C
sh, n(C CAr þ CeHbend)), 1242 (s, sh,
(m, sh,
([C40H30ClCuN4O2]þ,
n
(OeH)), 3059 (m, sh,
n(CeH), Ar), 2935
]
n
n
n
]N), azomethine), 1543, 1446, 1400 (s,
(m, sh,
n
(CueO)). EI-MS: m/z (intensity) 490.38 (10.12%)
]
n
(AreO)), 594 (m, sh,
n
(CueN)), 440
([C22H17ClN2O4$H2O]þ
,
(M$H2O)þꢃ),
454.90
(48.63%)
n(CueO)). ESI-MS: m/z (intensity) 697.60 (21.18%)
ꢃ
([C22H17ClN2O4]þ
,
Mþꢃ). Anal. Calcd. (%) for C22H19ClN2O4
[MꢀCl]2þ),
662.20
(50.00%)
ꢃ
(M ¼ 490.40 g/mol): C, 53.88; H, 3.91; N, 5.71. Found (%):C, 53.59; H,
([C40H30CuN4O2]2þ, [Mꢀ2Cl]2þ). Anal. Calcd. (%) for C40H30Cl2Cu-
N4O2$H2O (M ¼ 751.16 g/mol): C, 63.96; H, 4.29; N, 7.46. Found
4.02; N, 5.60. Conductivity ¼ 25
mS/cm.
(%):C, 63.87; H, 4.34; N, 7.41. Conductivity ¼ 52
mS/cm.
2.5.2. [VO(salphen1)]·H2O (4b)
Obtained as brown solid in 65.7% yield; mp > 300 ꢁC. FT-IR (KBr,
2.5.8. [VO(salphen4)]·H2O (4h)
cmꢀ1): 3440 (m, br,
n(CH3)), 1603 (s, sh, n(C
n(C
CAr þ CeHbend)), 1241 (s, sh,
sh,
n
(OeH)), 3087 (m, sh,
N), azomethine), 1536, 1441, 1383 (s, sh,
(AreO)), 951 (m, sh, n(V O)), 518 (m,
(VeO)). EI-MS: m/z (intensity) 459.30 (8.70%)
n
(CeH), Ar), 2943 (m, sh,
Obtained as black solid in 67.2% yield; mp 280 ꢁC. FT-IR (KBr,
]
cmꢀ1): 3410 (m, br,
n
n
(OeH)), 3051 (m, sh,
(CeH)), 1608 (s, sh, n(C N), azomethine), 1543, 1439, 1404 (s, sh,
CAr þ CeHbend)), 1250 (s, sh, (AreO)), 976 (m, sh, n(V O)), 617 (m,
(VeN)), 444 (m, sh,
(91.09%) ([C40H30N4O3V]2þ
n(CeH), Ar), 2931 (m, sh,
]
n
]
]
n
(VeN)), 463 (m, sh,
n
n(C
]
n
]
([C22H18N2O5V$H2O]þ
,
(M$H2O)þꢃ),
441.30
(53.12%)
sh,
n
n(VeO)). ESI-MS: m/z (intensity) 665.50
,
ꢃ
([C22H18N2O5V]þ
,
Mþꢃ). Anal. Calcd. (%) for C22H20N2O6V
[Mꢀ2Cl]2þ). Anal. Calcd. (%) for
ꢃ
(M ¼ 459.35 g/mol): C, 57.52; H, 4.39; N, 6.10. Found (%):C, 57.43; H,
C
40H30Cl2N4O3V$H2O (M ¼ 754.55 g/mol): C, 63.67; H, 4.27; N, 7.43.
4.41; N, 6.05. Conductivity ¼ 22
mS/cm.
Found (%): C, 63.58; H, 4.31; N, 7.29.
2.5.3. [Cu(salphen2)]·H2O (4c)
2.5.9. [Cu(salphen5)]·H2O (4i)
Obtained as brown solid in 85.1% yield; mp 285 ꢁC. FT-IR (KBr,
Obtained as brown solid in 87.1% yield; mp > 300 ꢁC. FT-IR (KBr,
cmꢀ1): 3420 (s, br,
sym(CeH), Ar), 2963 (m, sh, n(CH3)), 1607 (s, sh, n(C
1556, 1442, 1439 (s, sh, n(C CAr þ CeHbend)), 1242 (s, sh,
(CueO)). EI-MS: m/z (intensity) 518.40
n
(OeH)), 3147 (m, sh,
n
asym(CeH), Ar), 3055 (m, sh,
N), azomethine),
(AreO)), 525
cmꢀ1): 3418 (s, br,
n
(OeH)), 3056 (m, sh,
n(CeH), Ar), 2936 (m, sh,
n
]
n
(CeH)), 1616 (s, sh, n(C N), azomethine), 1539, 1466, 1396 (s, sh,
]
]
n
n(C
]
CAr þ CeHbend)), 1273 (s, sh,
n
(AreO)), 552 (m, sh,
n
(CueN)), 443
(m, sh,
n
(CueN)), 440 (m, sh,
n
(m, sh,
n(CueO)). ESI-MS: m/z (intensity) 697.60 (36.56%)
(16.23%) ([C24H21ClN2O4$H2O]þ
,
(M$H2O)þꢃ), 482.90 (15.31%)
([C40H30ClCuN4O2]þ,
[MꢀCl]2þ),
662.20
(48.19%)
ꢃ
([C24H21ClN2O4]þ
,
Mþꢃ). Anal. Calcd. (%) for C22H19ClN2O4
([C40H30CuN4O2]2þ, [Mꢀ2Cl]2þ). Anal. Calcd. (%) for C40H30Cl2Cu-
N4O2$H2O (M ¼ 751.16 g/mol): C, 63.96; H, 4.29; N, 7.46. Found
ꢃ
(M ¼ 518.45 g/mol): C, 55.60; H, 4.47; N, 5.40. Found (%):C, 55.69; H,
4.45; N, 5.51. Conductivity ¼ 15
mS/cm.
(%):C, 64.03; H, 4.35; N, 7.39. Conductivity ¼ 48
mS/cm.
2.5.4. [VO(salphen2)]·H2O (4d)
2.5.10. [VO(salphen5)]·H2O (4j)
Obtained as faint brown solid in 79.7% yield; mp > 300 ꢁC. FT-IR
Obtained as brown solid in 71.6% yield; mp > 300 ꢁC. FT-IR (KBr,
(KBr, cmꢀ1): 3445 (m, br,
(m, sh, sym(CeH), Ar), 2928 (m, sh,
azomethine), 1497, 1451, 1400 (s, sh, n(C
(AreO)), 953 (m, sh, n(V O)), 517 (m, sh,
n
(OeH)), 3186 (m, sh,
(CeH)), 1605 (s, sh, n(C
CAr þ CeHbend)), 1246 (s, sh,
(VeN)), 466 (m, sh, (VeO)).
nasym(CeH), Ar), 3032
cmꢀ1): 3414 (m, br,
n
n
(OeH)), 3078 (m, sh,
(CeH)), 1620 (s, sh, n(C N), azomethine), 1551, 1466, 1373 (s, sh,
CAr þ CeHbend)), 1271 (s, sh, (AreO)), 976 (m, sh, n(V O)), 617 (m,
(VeN)), 442 (m, sh,
(18.18%)
([C40H30N4O3V]2þ
n(CeH), Ar), 2931 (m, sh,
n
n
]
N)
,
]
]
n(C
]
n
]
n
]
n
n
sh,
n
n(VeO)). ESI-MS: m/z (intensity) 701.90
EI-MS: m/z (intensity) 486.3 (13.78%) ([C24H23ClN2O6V]þꢃ, Mþꢃ).
Anal. Calcd. (%) for C24H23ClN2O6V$H2O (M ¼ 521.84 g/mol): C,
55.24; H, 4.44; N, 5.37. Found (%):C, 55.20; H, 4.47; N, 5.28.
([C40H30ClN4O3V]þ,
[MꢀCl]þ),
665.50
Calcd.
(78.23%)
(%) for
,
[Mꢀ2Cl]2þ).
Anal.
C40H30Cl2N4O3V$H2O (M ¼ 754.55 g/mol): C, 63.67; H, 4.27; N, 7.43.
Conductivity ¼ 14
m
S/cm.
Found (%): C, 63.65; H, 4.29; N, 7.40. Conductivity ¼ 367
mS/cm.

166
R.F.M. Elshaarawy et al. / Journal of Molecular Structure 1128 (2017) 162e173
2.6. Antimicrobial assays
the tested sample in DMSO was added after 24 h of seeding. The
monolayers were then washed with sterile a phosphate buffered
saline (0.01 M, pH 7.2) with simultaneous treatment of the cells
with 100 mL from different dilutions of tested sample in a fresh
maintenance medium and incubated at 37 ꢁC for 48 h. A control of
untreated cells was cultured in absence of tested sample. A positive
control containing doxorubicin® drug was used for comparison. Six
wells were used for each concentration of the examined sample.
Every 24 h the observation under the inverted microscope was
carried out. The number of the surviving cells was determined by
staining the cells with crystal violet [33] followed by cells lysing
using 33% glacial acetic acid and then record the absorbance at
590 nm using ELISA reader (SunRise, TECAN, inc, USA) after well
mixing. The absorbance values collected from untreated cells were
considered as 100% proliferation.
The number of viable cells was determined using ELISA reader
as previously mentioned before and the percentage of viability was
calculated as {(1-(ODt/ODc)) x 100} where ODt is the mean optical
density of wells treated with the tested sample and ODc is the
mean optical density of untreated cells. The 50% inhibitory con-
centration (IC50), the concentration required to cause toxic effect in
50% of intact cells, was estimated from graphic plots.
2.6.1. Reagents
Dimethylsulphoxide
(DMSO),
ampicillin
(C16H19N3O4S,
349.41 g molꢀ1), gentamicin (C21H43N5O7, 477.60 g molꢀ1), anti-
bacterial drugs, and amphotericin B (C47H73NO17, 923.49 g molꢀ1),
antifungal drug, were obtained from Sigma Chemical Co. (St. Louis,
MO, USA).
2.6.2. Microbial cultures
Strains used in this study were provided by the National Orga-
nization for Drug Control and Research (NODCAR), Cairo, Egypt. The
tested strains are Staphylococcus aureus (S. Aureus, RCMB 010027)
representative for gram-positive bacteria, Escherichia coli (E. Coli,
RCMB 010059), representative for gram-negative bacteria, and
Aspergillus fumigates (A. fumigates, RCMB 02569) as well Candida
albicans (C. albicans, RCMB 05038). Stock cultures grown aerobically
on nutrient broth (NB) agar slants (Hi-Media) at 37 ꢁC were
maintained at 4 ꢁC. Pre-cultures containing 105 CFU/mL (CFU ¼
Colony Forming Units), grown aerobically in Mueller Hinton (MH)
liquid medium (Hi-Media) at 37 ꢁC for 5 h, were used as inoculum
for all experiments.
2.6.3. Antimicrobial susceptibility
Antimicrobial susceptibility of the bacterial strains was carried
out by agar well diffusion method [32] for the target compounds as
well as standard drugs, ampicillin, gentamicin and amphotericin B.
The diameters of the zones of inhibition (ZOI, mm) were measured
accurately as indicative of antimicrobial activity.
3. Results and discussion
3.1. Chemistry
3.1.1. Synthesis of RO-salophen(Cl) and pyridinium/quinolinium-
based salophens (3a-e)
2.6.4. Determination of MIC90
An integrated ionic liquids and Schiff-base condensation stra-
tegies have been used to provide a convenient route for fabrication
of our targeted salophens. The key condensing agents salicylalde-
hydes ionic liquids (Sal-ILs, 2a-c) were synthesized starting from
commercially available salicylaldehyde via a consecutive two-steps
protocol which starts with chloromethylation of salicylaldehyde to
afford 5-chloromethyl-salicylaldehyde (1) that used as alkylating
agent for quaternization of 2-methylpyridine (2-picoline, 2-MePy),
quinoline (Qn) and isoquinoline (iso-Qn) to yeild pyridinium- and
quinolinium-based Sal-ILs (2a-c) with high purity (see Scheme 2).
Eventually, RO-salophen(Cl)-type ligands (3a,b) have been pre-
pared by efficient Schiff-base condensation of 4-Cl-Phen with o-
vanillin or 3-ethoxysalicylaldehyde while pyridinium- and
quinolinium-based salophens (3c-e) were synthesized by Schiff-
base condensation between o-phen and pyridinium-/quinoli-
nium-Sal-ILs (2a-c) as condensing agents (cf. Scheme 2). The RO-
salophen(Cl) and pyridinium/quinolinium-based salophens (3a-e)
were isolated in a pure state and satisfied yield. Moreover, their
structural features were elucidated by FTIR, UV/Vis, 1H NMR, 13C
NMR, ESI-MS, EI-MS and conductivity measurements, as well.
As parameters of the antibacterial efficacy, the minimum
inhibitory concentration which inhibit 90% of tested microor-
ganism growth when compared to control (MIC90) of the most
potent compounds against infection isolates were determined us-
ing the macro-dilution broth susceptibility test. Stationaryephases
for tested microbial species were prepared at 37 ꢁC and used to
inoculated fresh 5.0 mL of bacterial cultures to an OD600 of 0.05.
These 5.0 mL cultures were then incubated at 37 ꢁC until an OD600
of 0.10 was achieved from which standardized bacterial suspen-
sions were prepared to a final cell density of 6 ꢂ 105 CFU/mL.
Different concentrations from the tested sample (0e320 mg/mL) in
DMSO were prepared and mixed with 5.0 mL of the standardized
bacterial suspension then added to the plates and incubated for
24 h at 37 ꢁC. The CFU were counted for each dilution and compared
to the growth of untreated controls.
2.7. In vitro anticancer activity
2.7.1. Cell cultures
Human colon carcinoma (HCT-116) cells were obtained from the
American type culture collection (ATCC, Rockville, MD). The cells
were grown on RPMI-1640 medium supplemented with 10% inac-
3.1.2. Synthesis of the metallosalophens (3a-j)
tivated fetal calf serum and 50
m
g/mL gentamycin. The cells were
The copper(II) and oxovanadium(IV) complexes of our fabri-
cated salophen-type ligands, [M(salphen1-5)]$H2O (4a-j), were
maintained at 37 ꢁC in a humidified atmosphere with 5% CO2 and
were sub-cultured two to three times a week.
prepared by refluxing a methanolic solution containing the
respective salt and the parent salophen under aerobic conditions
(see Scheme 3).
2.7.2. Antitumor assay
The antitumor activity was evaluated against HCT-116 (human
colon cancer) cell lines. The cancer cells were grown as monolayers
in growth RPMI-1640 medium supplemented with 10% inactivated
Unfortunately all trails for growing X-ray quality single crystals
of metallo-salophens (4a-j) were unsuccessful. Yet, the proposed
plausible structural skeletons for metallo-salophens (4a-j) were
suggested based upon elemental and spectral analysis (FTIR,
UVeVis) and conductivity measurements. Furthermore, matching
of our proposed structures with those of reported metallo-
salophens analogues in Table 1.
fetal calf serum and 50
mg/mL gentamycin. The monolayers of
104 cells adhered at the bottom of the wells in a 69-well microtiter
plates were incubated for 24 h at 37 ꢁC in a humidified incubator
with 5% CO2. Fresh medium containing different concentrations of

R.F.M. Elshaarawy et al. / Journal of Molecular Structure 1128 (2017) 162e173
167
Scheme 2. Schematic diagram for the synthesis of salicylaldehyde ionic liquids (Sal-ILs-, 2a-c), and their salophen-type ligands (3a-e).
Scheme 3. Synthesis of metallosalophens (4a-j).
3.2. Characterizations of the salophens and their complexes
conductance data, 48e367 mS/cm.
The electron impact mass spectra (EI-MS) of new RO-
salophen(Cl) (3a,b) are synonymous with their known stability as
reveled by maximum contribution (100%) of a molecular ion peak
[M]þꢃ, a molecular mass signature. This stability is significantly
reduced upon chelation of these ligands with Cu(II)/VO(II) ions as
3.2.1. Microanalytical data, conductivity and mass spectrometry
RO-salophen(Cl) and pyridinium/quinolinium-based salophens
(3a-e) and their complexes (4a-j) were prepared in convinced
yields, gave satisfactory C, H, and N elemental analyses, which are
in good agreement with our proposed structural formulas for the
parent salophens and their chelate complexes (see the experi-
mental section).
demonstrated by the high level of fragmentation and low contri-
bution of the molecular mass signature, [M]þ
.
ꢃ
The common peculiarities for positive mode electrospray ioni-
zation mass spectra of pyridinium/quinolinium-based salophens
(3c-e) and their complexes (4e-j) represented in removal of one
counter ion, Clꢀ, from the compound producing singly-charged
cations, [MꢀClꢀ]þ, Subsequent loss of the second anion, single or
both ionic liquid compartments to form new singly or doubly-
charged species, [Mꢀ2 Clꢀ]2þ, [Mꢀ(MePy or Qn or iso-Qn)]2þ and
Collected molar conductance values of RO-salophen(Cl) (3a,b)
and their complexes (4a-d) in EtOH (1 ꢂ 10ꢀ3 M) at 25 ꢁC are in the
range of 14e25 mS/cm which are in agreement with the non-ionic
nature of these architectures. On other hand, the electrolytic na-
ture of pyridinium/quinolinium-based salophens (3c-e) and their
complexes (4e-j) was concluded from thier observed molar

168
R.F.M. Elshaarawy et al. / Journal of Molecular Structure 1128 (2017) 162e173
Table 1
Simultaneous emerging of new peaks with marked shifts (see
Fig. 1) in the IR markers of metallosalophen complexes (4a-j) in
comparison to those of parent salophens (3a-e) demonstrated
successful binding of salophens to metal centers and, additionally,
suggest a plausible modes of salophen-metal chelation mode.
The common spectral peculiarities of the IR spectra of metal-
losalophens represented in: (i) two characteristic energy-shifts of
the azomethine and aryleO stretches (check Fig. 1 and Table 2)
arising from the binding of metal ion by the donor atoms set in
salophens. (ii) red-shifting or blue-shifting of the azomethine
(HeC]N) stretching vibration by þ7 cmꢀ1 to ꢀ26 cmꢀ1 confirming
the participation of azomethine nitrogen in coordination to the
metal center which further confirmed by the prominence of new
peak at the rang of 617e525 cmꢀ1 ascribable to MeN vibration. (iii)
Also, a remarkable blue shifting of the aryleO (phenolic CeO)
stretch to lower frequency by 6e29 cmꢀ1 is in an agreement with
the deprotonation of phenolic OH and replacement of phenolic
proton by metal ion and growth of novel absorption bands at the
rang of 468e440 cmꢀ1, typical for MeO vibration, provide further
evidence for our concluding remark. (v) In conclusion, infrared
spectroscopic data revealed that, new salophens architectures act
as dianionic tetradentate N2O2-chelating ligands. (v) Appearance of
Some literature Cu(II)/VO(II)-salophens from Cambridge Structural Database (CSD).
Entry
Structure
Reference
[30a]
BUVQUG
NALJAN
[30b]
AGIXOE
[30c]
[31a]
MAMMET
n
(OeH) bands around 3430 cmꢀ1 confirms the hydrate nature for the
new complexes as the reveled from their microanalytical data (see
experimental section).
EYEGAR
[31b]
3.2.3. NMR studies and tautomerism scenario in solution
Collected NMR (1H and 13C) spectral data could provide us with
precious information about the possible dynamic enolimine/
ketoenamine tautomeric equilibria and the relative tautomer's
populations, in our salophens 3a-e by comparing their NMR spectra
with literature NMR studies of the related salophen Schiff-base li-
gands isolated in the previous work [36].
Examination of the NMR spectra of RO-salophen(Cl)-type li-
gands (3a,b) (see experimental section) leads us to highlight the
following aspects: (i) The characteristic singlets around 12.93 ppm
(2H) and 8.93 ppm (2H) could be ascribed to the resonances of
phenolic OeH and azomethinic protons (HeC]N), respectively. (ii)
This multiplicity pattern suggested that the central RO-salophen
backbone is in the expected pure O-protonated tautomeric form,
bis-(enolimine) (cf. Scheme 4), and the downfield shift of phenolic
proton signal in all RO-salophens is assignable to an involvement of
such proton in a stable six-membered intramolecular H-bonded
chelating ring with the azomethinic nitrogen. (iii) The aromatic and
methylene protons are slight affected by RO exchange from OMe to
OEt, depending on the different arrangement adopted by the
protons.
[Mꢀ(MePyHþ or QnHþ or iso-QnHþ)ꢀ(MePy or Qn or iso-Qn)]þ,
respectively.
3.2.2. IR spectroscopic data
IR spectra recorded for the new salophens (3a-e) provide
informative evidences confirming successful anchoring of 3-
alkoxysalicyldehyde or salicylaldehyde ionic liquids with 4-Cl-
Phen and Phen, respectively, via Schiff-base condensation, as
revealed from the concluding IR spectral remarks for (3a-e): (i)
extremely intense broad band observed at the range of
3442
70 cmꢀ1 along with
a maxima at the range of
1265 15 cmꢀ1 arise from phenolic OeH stretching involved in
Contrary, for first glance in the 1H NMR spectra of the
pyridinium/quinolinium-based salophens (3c-e) seem to be quite
complicated ascribable to the presence of two sets of signals due to
the coexistence of pair of tautomers with different populations, bis-
(enolimine) coupled with some contribution of the ionic
phenolate-iminium tautomeric form (cf. Scheme 4). Where the two
singlets around 13.80 ppm, equivalent to two protons, of phenolic
OeH is characteristic for bis-(enolimine) tautomer and around
13.50 ppm, nearly equivalent for 1H, is typical for OeH of
enolimine/phenolate-iminium tautomer. The azomethinic protons
resonate as a singlet around 8.80 ppm (~2H) which is in consistent
with the bis-(enolimine) tautomer skeleton and a singlet/doublet
set (8.62/8.43 ppm) (~1H/~1H) which is in agreement with
enolimine/phenolate-iminium tautomer mixture. Thus, 1H NMR
spectrum demonstrates that, in salophens (3c-e) the central back-
bone is in the enolimine form with some contribution of the
enolimine/phenolate-iminium form in the solution (cf. Scheme 4).
Further evidence for the O-protonated tautomer could be given
_
internal hydrogen bonded system (OeHcN). (ii) Displacement of
the azomethine (eHC]Ne) stretch of 3a-e to lower wavenumber,
around 1613 cmꢀ1, in comparison with that of the free azomethine
moiety [34,35] provide further evidence for the involvement of
azomethine fragment in intramolecular hydrogen bonding (C]
_
NcOeH). (iii) Three prominent peaks at the ranges of
1528e1497 cmꢀ1, 1159e1153 cmꢀ1 and 756e739 cmꢀ1 are char-
acteristic for the ionic liquid compartments. (iv) Noteworthy,
absence absorption mode, around 1700 cmꢀ1, assignable to the
carbonyl stretching vibration of keto-enamine tautomeric form
provide a strong evidence for the predominance of an enol-imine
tautomer in ketoeenol tautomeric equilibrium of salophens (i.e
the central core of salophens is in the expected O-protonated enol-
imine tautomeric form in the solid state) (see Scheme 4). Inter-
estingly, these salophens are in bis-enolimine I tautomeric form
which has more stable six-membered H-bonded chelating ring
than five-membered H-bonded chelating ring in bis-enolimine II.

R.F.M. Elshaarawy et al. / Journal of Molecular Structure 1128 (2017) 162e173
169
Scheme 4. All possible tautomeric forms and intra molecular hydrogen-bonding in RO-salophen(Cl) backbone.
Fig. 1. Partial IR segment, for comparison the azomethine and phenolate stretches and their splitting patterns in salophene 3c and its complexes 4e,f.
by 13C NMR spectra where Claramunt et al. observed that the CO
fragment exhibited 13C resonance varies from ~160 ppm, assignable
to phenolic CeOH typical for pure enol-imine, to ~180 ppm
attributable to carbonyl group of a pure keto-enamine tautomer
[37]. These concluding remarks make the 13C spectra a powerful
160.0 ppm typical for enol-imines tautomer [38] which prove bis-
(enolimine1) identity for these architectures. However, 13C NMR
spectra of pyridinium-/quinolinium-salophens (3c-e) demon-
strated the coexistence of bis-(enolimine) and phenolate-iminium
tautomeric forms in solution as reveled from the observed signals
around 160 ppm, characteristic for bis-(enolimine), and at the
range of 171e164 ppm, intermediate between that of enolimine
tool to discern the relative tautomeric population. Noteworthy, 13
C
NMR spectra of RO-salophen(Cl) (3a,b) exhibit resonance at ca

170
R.F.M. Elshaarawy et al. / Journal of Molecular Structure 1128 (2017) 162e173
Table 2
Assignment of segment of vibrations for salophens (3a-e)/metallosalophens (4a-j).
Compd.
n
(OeH)
n(C]
Dn(C]
n(PheO)
Dn(PheO)
n(MeN)
n(MeO)
N)
N)
H2salophen1 (3a)
3512
3452
3440
3430
3420
3445
3389
3421
3391
3379
3437
3410
3371
3418
3414
1616
1605
1603
1613
1607
1605
1613
1619
1620
1601
1608
1608
1640
1616
1620
e
1249
1242
1241
1252
1242
1246
1271
1264
1265
1273
1242
1250
1280
1273
1271
e
e
e
[Cu(salophen1)]$H2O (4a)
[VO(salophen1)]$H2O (4b)
H2salophen2 (3b)
[Cu(salophen2)]$H2O (4c)
[VO(salophen2)]$H2O (4d)
H2salophen3 (3c)
[Cu(salophen3)]$H2O (4e)
[VO(salophen3)]$H2O (4f)
H2salophen4 (3d)
[Cu(salophen4)]$H2O (4g)
[VO(salophen4)]$H2O (4h)
H2salophen5 (3e)
ꢀ11
ꢀ13
e
ꢀ7
ꢀ8
e
528
518
e
444
463
e
ꢀ6
ꢀ8
e
ꢀ10
ꢀ6
e
525
517
e
440
466
e
þ6
þ7
e
ꢀ7
ꢀ6
e
556
605
e
440
468
e
þ7
þ7
e
ꢀ29
ꢀ23
e
594
617
e
440
444
e
[Cu(salophen5)]$H2O (4i)
[VO(salophen5)]$H2O (4j)
ꢀ24
ꢀ20
ꢀ7
ꢀ9
552
617
443
442
and ketoenamine.
aqueous solubility and enhancing the pharmacological action.
3.2.4. Electronic absorption spectroscopy
3.3.1. Antimicrobial activity profile
The electronic absorption spectra of the salophens (3a-e) and
their copper(II)/oxovanadium(IV) complexes (4a-j) were recorded
in DMSO (10ꢀ3 M) in the range 200e800 nm at room temperature.
In salophens (3a-e) the absorption around 222 and 259 nm origi-
RO-salophen(Cl), pyridinium/quinolinium-based salophens (3a-
e) and metallosalophens (4a-j) were in vitro evaluated in compar-
ison with standard antibiotics (antibacterial, ampicillin and
gentamicin; antifungal, amphotericin B) for their efficacy to curb
the growth of a common panel of pathogenic microbial species
inclusive S. aureus (RCMB 010027), a gram-positive bacteria (Gþ),
nate from the characteristic
p/p* and n/p* transitions associ-
ated with the phenolic chromophore [39], while an intense peak
E. coli (RCMB 010059),
a
gram-negative bacteria (Gꢀ), and
around 327 nm may be ascribed to the
the azomethine group [41],
p/p* transition involving
A. fumigates (RCMB 02569) as well C. albicans (RCMB 05038), as
fungal pathogens. The collected zone of inhibition (ZOI) values
(Fig. 2) domenestrate a synergistic antibiotic efficacy of new salo-
phens and their complexes against all tested bacterial and fungal
strains. This enhanced and synergistic biopotency of salophens and
their complexes may be ascribed for consolidation of diverse potent
pharmacophores into a single architecture (salophens or M-salo-
phens) which exerts overall collective effects in terms of microbi-
ological efficiency. Foremost, the azomethine, a hydrogen-bonding
The features and data collected from the electronic spectra of
the copper(II) and oxovanadium(IV) complexes could be used for
assigning the stereochemistries of these complexes based on the
positions and types of ded transitions. Notably, electronic spectra
of the copper(II) complexes display a broad band at the range of
623e546 nm due the ded transition in a square-planar environ-
ment [40]. As well, absorption peak observed around 440 nm is
ascribed to a charge transfer (CT) from the non-bonding orbital of
the oxygen atoms to the vacant copper(II) d orbitals [41]. Further
evidence for the involvement of Cu(II) in a four-coordinate square-
planar environment is the observation of absorption peak at the
range of 352e342 nm in the electronic spectra of Cu(II)-salphen
complexes [42].
acceptor (HBA), and phenolic hydroxyl pharmacophores,
a
hydrogen-bonding donor/acceptor (HBD/HBA), of N-salicylidene
fragment may interact with the active sites which have distributed
in the components of the microbial cell via hydrogen-bonding
causing an interference with normal cell process and enzymatic
reactions [45]. Additionally, the pyridinium terminals of
pyridinium/quinolinium-based salophens undergoes electrostatic
interactions with the negatively charged microbial outer wall [46],
moreover, the hydrophobic pharmacophore (methyl terminal)
enhance the penetration of the microbial cell wall and subse-
quently disrupt the cytoplasmic membrane with simultaneous
release of cell constituents causing, eventually, pathogen death.
As revealed from Fig. 2, all salophen Schiff bases demonstrated
lower antimicrobal potency than their Cu(II)-complexes while
comparable antimicrobial efficacy to oxovanadium(IV) salophen
complexes. The boosted antimicrobial activities of Cu(II)-complexes
can be explained on the basis of: (i) Overtone's concept [47] and
Tweedy's Chelation theory [48] which attributed the higher anti-
microbial efficacy of complexes to their enhanced liposolubility
action owing to diminishing the polarity of the copper ion through
coordination as a result of partial sharing of the cationic charge of
the Cu(II) ion with donor sites of salophen. This increased lip-
ophilicity facilitates penetration of target complex into lipid
membrane of pathogen along with blocking metal active enzymatic
binding sites in the microorganisms. (ii) Cu(II)/Cu(I) redox cycle
which may catalyzes releasing of reactive oxygen species (ROS) into
microbial cell, targeting for many biochemical reactions that critical
for the microbial cell such as oxidation of thioproteins, DNA failure,
The geometries of the oxovanadium(IV) salphen complexes
were assigned based on the molecular orbital treatment model
postulated by Ballhausen and Gray [43]. According to this model,
three d-d peaks were expected for five-coordinated VO2þ ion. Two
of these ligand field bands are easily observed in a low-energy re-
gion at the range of 909e625 nm (band I, n1) and 690e526 (band II,
n2) ascribed to 2B2g /2E, (dxy/dxz, dyz) and 2B2g/2B1g (dxy/d2x-
d2y) transitions, respectively, while the third band (band III, n3
)
attributed to 2B2/2A1 (dxy/d2z) transition may be masked by
charge transfer absorptions in a high-energy range of 476e333 nm
[49,44]. The electronic spectra of all oxovanadium(IV) salphen
complexes exhibited all three peaks in the ranges of 706e684 nm,
672-535 nm and 473-334 nm characteristic for n1, n2 and n3,
respectively, typical for a vanadyl (VO2þ) ion in a five-coordinate
coordination geometry in accordance with Ballhausen and Gray
ligand field model.
3.3. Pharmacology
Many clinical trials of new bioactive archtictures end in failure
due to their low efficacy associated with thier limited bioavail-
ability or solubility. Thus, anchoring of bioactive archtictures to
ionic liquid terminals may offer synergistic effects of improving

R.F.M. Elshaarawy et al. / Journal of Molecular Structure 1128 (2017) 162e173
171
Fig. 2. Graph of zone of inhibition (ZOI, mm) for most potent compounds against different microbial species.
lipoproteins and lipid peroxidation and the displacement of Cu-
3.3.2. Preliminary in vitro antitumor assay
containing metalloprotein [49]. Once, the Cu(II)-salophen pene-
trate the bacterial cell, it catalyze the cellular oxygen to readily
oxidizes the thioprotein (R-SH) followed by an odd-electron
transfer reduction of copper(II)-salophen into form Cu(I)-
salophen. Furthermore, oxidation disulfide linkage in cysteine
provide other pathway to create reduced Cu(I)-salophen. This
Cu(II)/Cu(I) redox cycle is superoxide dismutase (SOD)-activity
mimic, where Cu(I)-salophen catalyzes the odd-electron reduction
of cellular oxygen (O2) into reactive superoxide species (Oꢀ2 ) and
peroxide (H2O2), while Cu(II)-salophen catalyzes the dismutation of
highly reactive superoxide (Oꢀ2 ) into oxygen (O2) (see Scheme 5).
ROS formed during this cycle, Oꢀ2 and H2O2, are nonspecifically
exert oxidative destruction for proteins, nucleic acids, lipids and
sugars resulting in enhanced antimicrobial actions. Moreover, the
reduced Cu(I)-salophens may inhibit DNA and ATP production via
inhibition of mitochondrial respiration. In conclusion, the quasi-
reversible odd-electron CuII/CuI redox cycle gives precious infor-
mation for mode of antimicrobial action of our Cu(II)-salophens.
Interestingly, the majority of tested compounds more potent as
fungicides with remarkably potent inhibitory activity against
C. albicans. This may be attributed to the difference in the structure
of microbial cell-wall and/or mode of antibiotic-resistance by mi-
crobial species. Noteworthy, the effectiveness of the salophen Schiff
bases and their complexes in inducing staphylococcalcidal action
compared to E. coli-cidal effect may be ascribed to the rigid multi-
layered structure of the outer membrane for E. coli which
composed predominately of well-packed blocks of lipopolysac-
charide that provides the bacterium cell an effective permeability
barrier to the passage of antibacterial agents [50].
Preliminary in vitro antitumor studies of representative samples
of metallosalophens (4a-j) were addressed in comparison to stan-
dard antitumor drug, doxorubicin (C27H29NO11, 543.52 g/mol),
against human colon carcinoma (HCT-116) cell lines. Noticeable
that all selected complexes exhibit growth inhibitory effects against
cisplatin-insensitive colon cancer cell lines HCT-116 cell lines with a
structure-dependent efficacy profile as revealed from the collected
cell viability values shown in Fig. 3. Intersetingly, metal center co-
ordinated to salophen ligands can modulate the anticancer activity
of the complex where the cell viability data coupled with IC50
values demonstrated that VO(II)-salophens have higher antitumor
activities than Cu(II)-salophens. For example, VO(II)-salophen2 (4f)
(IC50 ¼ 2.13
m
g/mL) was ca. 10-fold more cytotoxic against HCT-
116 cell lines than Cu(II)-salophen2 (4e) (IC50 ¼ 20.30
mg/mL). This
may be ascribed to good “chemical nuclease” activity,
Among assaying compounds, Cu(II)-salophens bearing a-pico-
linium and quinolinium compartments, [Cu(salphen3)]$H2O (4e)
and [Cu(salphen4)]$H2O (4g), were found to be the most potent and
broad-spectrum antimicrobial agents (MIC90S.aureus
¼
26.50/
g/mL; MIC90A.
g/mL,
21.25
m
g/mL; MIC90E.coli
¼
30.15/25.50
m
¼ 45.25/36.25
mg/mL; MIC90C. albicans ¼ 18.50/15.35
m
fumigates
respectively). Inspired with this notice, further structural refine-
ment and more microbiological assessments for these compounds
may offer new generation of promising antibiotic candidates that
play critical role in fighting microbial infections.
Fig. 3. Concentration-dependent antitumor efficacy assessment of representative
samples of metallosalophens against human HCT116 cell lines.
Scheme 5. Oꢀ2 dismutation mediated by the SOD [CuII/CuI -salophen] redox cycle confined in the microbial species.

172
R.F.M. Elshaarawy et al. / Journal of Molecular Structure 1128 (2017) 162e173
biocompatibility and efficient photoinduced DNA cleavage activity
of Vanadium(IV) ion in vanadyl core [51].
Remarkable that, the higher effectiveness of pyridinium
salophen-derived complexes (4e-j) as HCT-116 antitumor agents in
comparison to of RO-salophen(Cl)-derived complexes (4a-d) as
revealed from observed cell viability data and IC50 values (4c,
References
[1] A. Tanitame, Y. Oyamada, K. Ofuji, M. Fujimoto, K. Suzuki, T. Ueda, H. Terauchi,
M. Kawasaki, K. Nagai, M. Wachi, J. Yamagishi, Bioorg. Med. Chem. 12 (2004)
5515e5524.
[2] D.T. Chu, J.J. Plattner, L. Katz, J. Med. Chem. 39 (1996) 3853e3874.
[3] T. Miyamoto, J. Matsumoto, K. Chiba, H. Egawa, K. Shibamori, A. Minamida,
Y. Nishimura, H. Okada, M. Kataoka, M. Fujita, T. Hirose, J. Nakano, J. Med.
Chem. 33 (1990) 1645e1656.
[4] N. Nakada, H. Shimada, T. Hirata, Y. Aoki, T. Kamiyama, J. Watanabe,
M. Arisawa, Antimicrob. Agents Chemother. 37 (1993) 2656e2661.
[5] J.V. Dubsky, A. Sokol, Collect. Czech. Chem. Commun. 3 (1931) 548e549.
[6] K. Nakajima, K. Kojima, M. Kojima, J. Fujita, Bull. Chem. Soc. Jpn. 63 (1990)
2620e2630.
IC50 ¼ 25.40
mg/mL; 4e, IC50 ¼ 20.30
mg/mL). This could be attrib-
uted to the amphiphilic behaviour of methylpyridinium ionic liquid
terminal where the hydrophilic cationic segment, pyridinium,
exhibit strong electrostatic interactions with the anionic phosphate
groups of DNA. Moreover, the non-polarizing effect of methyl group
significantly affected the DNA-metallosalophen van der Waal's
interaction whereas the hydrophobic nature of methyl fragment
increases the van der Waal's energy of methylpyridinium salophen-
derived complexes, in comparison to other complexes, which leads
to an enhancement in DNA-metallosalophen association via van der
Waal's forces. Furthermore, based on literature, it might be said
that the van der Waal's forces have played a more significant role
than hydrogen-bonding in the binding of different compounds to
DNA [52].
[7] (a) M. Pooyan, A. Ghaffari, M. Behzad, H. Amiri Rudbari, G. Bruno, J. Coord.
Chem. 66 (2013) 4255e4267;
(b) R. Kumar, K. Mahiya, P. Mathur, Dalton Trans. 42 (2013) 8553e8557.
[8] (a) S.Y.E.I. Sheikhshoaie, J.C.M. Dusek, Z.T.V. Eigner, M. Khaleghi, RSC Adv. 5
ꢀ
(2015) 95104e95117;
(b) M. Nath, P.K. Sainia, Dalton Trans. 40 (2011) 7077e7121;
(c) A.R.H. Pramanik, C.P. Paul, P. Mondal, C.R. Bhattacharjee, J. Mol. Struct.
1100 (2015) 496e505.
[9] (a) T.M. Fasina, O.O. Ogundele, I. Ayeni, J. Chem. Pharm. Res. 6 (6) (2014)
816e819;
(b) M.E.M. Zayed, R.M. El-Shishtawy, Asian J. Chem. 25 (5) (2013) 2719e2721;
(c) A.S. Gaballa, M.S. Asker, A.S. Barakat, S.M. Teleb, Spectrochim. Acta Mol.
Biomol. Spectrosc. 67A (1) (2007) 114e121.
[10] (a) S.Y. Ebrahimipour, I. Sheikhshoaie, M. Mohamadi, S. Suarez, R. Baggio,
M. Khaleghi, M. Torkzadeh-Mahani, A. Mostafavi, Spectrochim. Acta Mol.
Biomol. Spectrosc. A142 (2015) 410e422;
4. Conclusion
(b) P.K. Sasmal, R. Majumdar, R.R. Dighe, A.R. Chakravarty, Dalton Trans. 39
(2010) 7104e7113.
[11] X.-M. Wang, R.-Q. Fan, P. Wang, L.-S. Qiang, Y.-L. Yang, Y.-L. Wang, Inorg.
Chem. Commun. 51 (2015) 29e35.
[12] D. Zhang, Z. Zhao, P. Wang, X. Chen, J. Coord. Chem. 65 (2012) 2549e2560.
[13] C.R. Nayar, R. Ravikumar, J. Coord. Chem. 67 (2014) 1e16.
[14] (a) W.M. Willingham, J.R. Sorrenson, J. Trace Elem. Med. 3 (1986) 139e152;
(b) H. Tapiero, T.M. Townsend, K.D. Tew, Biomed. Pharmacother. 57 (2003)
386e398.
[15] M.J.F.A. Tuorkey, K.K. Abdul, Aziz, Biomed. Pharmacother. 63 (2009) 194e201.
[16] S. Sharma, F. Athar, M.R. Maurya, A. Azam, Eur. J. Med. Chem. 40 (2005)
1414e1419.
The aim of our protocol to develop new pharmacological can-
didates with synergistic antibacterial, antifungal and anticancer
performance. In this endeavor, the biocidal activities of newly
designed and synthesized RO-salophen(Cl), pyridinium/quinoli-
nium-based salophens (3a-e) and metallosalophens (4a-j) have
been investigated against a common panel of pathogenic bacterial
and fungal strains. Moreover, the antitumor efficacy of these ar-
chitectures against human colon carcinoma (HCT-116) cell lines has
been addressed. The observed ZOIs and MIC values demonstrated a
moderate to superb broad-spectrum antimicrobial efficacy of sal-
ophens and metallosalophens in comparison to the standard anti-
biotic with a preferential ability to perform as a fungicides than to
act as bactericides (in most cases, the growth inhibition of
C. albicans > A. fumigates > S. aureus > E. coli). Interestingly, Cu(II)-
salophens complexes exhibited higher antimicrobal potency than
VO(II)-salophens and parent salophens. [Cu(salphen4)]$H2O (4g)
was found to be the most potent and broad-spectrum antimicrobial
[17] N. Yasumatsu, Y. Yoshikawa, Y. Adachi, H. Sakurai, Bioorg. Med. Chem. 15
(2007) 4917e4922.
[18] M.S.Y. Veitia, F. Dumas, G. Morgant, J.R.J. Sorenson, Y. Frapart, A. Tomas,
Biochimie 91 (2009) 1286e1293.
[19] (a) K.D. Rainsford, K. Brune, M.W. Whitehouse, Proceedings of the Symposium
€
on Aspirin and Related Drugs: Their Actions and Uses, Birkhauser Verlag:
Basel, Switzerland; Stuttgart, West Germany, 1977, pp. 109e117. ISBN 3-
7643-0902-4;
(b) D.D. Kovala, J. Inorg. Biochem. 79 (2000) 153e157.
[20] T. Suksrichavalit, S. Prachayasittikul, C. Nantasenamat, N.-A.C. Isarankura,
V. Prachayasittikul, Eur. J. Chem. 44 (2009) 3259e3265.
[21] M.A. Rivero, R.A. De Vizcaya, N. Plant, L. Ruiz, M. Dobrota, Chem. Biol. Interact.
165 (2007) 189e199.
[22] (a) A.M. Evangelou, Crit. Rev. Oncol. Hematol. 42 (2002) 249;
(b) R.S. Ray, B. Ghosh, A. Rana, M. Chatterjee, Int. J. Cancer 120 (2007) 13e23.
[23] J. Benítez, L. Becco, I. Correia, S.M. Leal, H. Guiset, J.C. Pessoa, J. Lorenzo,
F. Aviles, P. Escobar, V. Moreno, B. Garat, D. Gambino, J. Inorg. Biochem. 105
(2011) 303e312.
[24] (a) A. Adach, M. Daszkiewicz, M. Tyszka-Czochara, B. Barszcz, RSC Adv. 5
(2015) 85470e85479;
(b) S. Holmes, C.J. Carrano, Inorg. Chem. 30 (1991) 1231e1235.
[25] W.L. Hough, M. Smiglak, H. Rodrıguez, R.P. Swatloski, S.K. Spear, D.T. Daly,
J. Pernak, J.E. Grisel, R.D. Carliss, M.D. Soutullo, New J. Chem. 31 (2007)
1429e1436.
agent (MIC90S.aureus ¼ 21.25
m
g/mL; MIC90E.coli ¼ 25.50
m
g/mL;
MIC90A. g/mL; MIC90C.
¼ 36.25
m
¼ 15.35
mg/mL).
fumigates
albicans
Structureeactivity relationship for new metallosalophens against
HCT-116 cell lines revealed a correlation between the hydrophobic-
hydrophilic balance of target compound, as tuned by the sub-
stituents on the salicylidene fragment and coordinated metal ion,
and its anticancer activity. Prominently, VO(II)-salophens are more
effective in reduction HCT-116 cell viability than Cu(II)-salophens.
For example, VO(II)-salophen2 (4f) (IC50 ¼ 2.13
m
g/mL) was ca. 10-
fold more efficient than Cu(II)-salophen2 (4e) (IC50 ¼ 20.30
mg/mL).
Also, pyridinium salophen-derived complexes (4e-j) are more
effective as HCT-116 antitumor agents in comparison to salophens
without ionic terminals.
[26] (a) R.F.M. Elshaarawy, A.A. Refaee, E.A. El-Sawi, Carbohydr. Polym. 146 (2016)
376e387;
(b) R.F.M. Elshaarawy, F.H.A. Mustafa, A. Herbst, A.E.M. Farag, C. Janiak, RSC
Adv. 6 (25) (2016) 20901e20915;
(c) R.F.M. Elshaarawy, T.B. Mostafa, A.A. Refaee, E.A. El-Sawi, RSC Adv. 5 (84)
(2015) 68260e68269;
(d) K.M. Docherty, J.C.F. Kulpa, Green Chem. 7 (2005) 185e189.
[27] (a) E.E. Alberto, L.L. Rossato, S.H. Alves, D. Alves, A.L. Braga, Org. Biomol. Chem.
9 (2011) 1001e1003;
(b) J. Pernak, K. Sobaszkiewicz, I. Mirska, Green Chem. 5 (2003) 52e56.
[28] (a) R.F.M. Elshaarawy, C. Janiak, Tetrahedron 70 (43) (2014) 8023e8032;
(b) R.F.M. Elshaarawy, Z.H. Kheiralla, A.A. Rushdy, C. Janiak, Inorg. Chim. Acta
421 (2014) 110e122;
Acknowledgment
R.F.M.E. would like to thank Prof. Christoph Janiak, Institut für
Anorganische Chemie und Strukturchemie, Heinrich-Heine Uni-
€
versitat Düsseldorf, for her generous support.
(c) R.F.M. Elshaarawy, C. Janiak, Eur. J. Med. Chem. 75 (2014) 31e42;
(d) L. Carson, P.K.W. Chau, M.J. Earle, M.A. Gilea, B.F. Gilmore, S.P. Gorman,
M.T. McCann, K.R. Seddon, Green Chem. 11 (4) (2009) 492e497.
[29] (a) R.F.M. Elshaarawy, H.K. Ibrahim, E. Eltamany, I. Mohy-Eldeen, Maced. J.
Chem. Chem. Eng. 27 (1) (2008) 65e79;
Appendix A. Supplementary data
Supplementary data related to this article can be found at http://
dx.doi.org/10.1016/j.molstruc.2016.08.059.

R.F.M. Elshaarawy et al. / Journal of Molecular Structure 1128 (2017) 162e173
173
(b) M.S. Refat, I.M. El-Deen, R.F.M. El-Shaarawy, Russ. J. Gen. Chem. 84 (3)
(1994) 1067e1070.
(2008) 593e601.
[39] (a) S.M. Crawford, Spectrochim. Acta 19 (1963) 255e270;
(b) B. Bosnich, J. Am. Chem. Soc. 90 (1968) 627e632;
(c) S. Di Bella, I. Fragala, I. Ledoux, M.A. Diaz-Garcia, T.J. Marks, J. Am. Chem.
Soc. 119 (1997) 9550e9557.
[40] (a) V.B. Arion, P. Rapta, J. Telser, S.S. Shova, M. Breza, K. Luspai, J. Kozisek,
Inorg. Chem. 50 (2011) 2918e2931;
[30] (a) C.-H. Li, J.-H. Jiang, P. Yang, L.-M. Tao, X. Li, S.-X. Xiao, X. Peng, X. Tao, J.-
Q. Xie, Y. Zhu, M.-A. Xie, Q.-G. Li, J. Therm. Anal. Calorim. 119 (2015)
1285e1292;
ꢀ
ꢀ ꢀ
(b) A. Jamshidvand, H. Kargar, R. Kia, M.N. Tahir, Acta Crystallogr. Sect. E
Struct. Rep. Online 66 (2010) m1473em1479;
(c) P.U. Naik, G.J. McManus, M.J. Zaworotko, R.D. Singer, Dalton Trans. (2008)
4834e4836.
[31] (a) P. Plitt, H. Pritzkow, T. Oeser, R. Kraemer, J. Inorg. Biochem. 99 (2005)
1230e1237;
(b) H. Houjou, T. Motoyama, K. Araki, Eur. J. Inorg. Chem. (2009) 533e538.
[41] S. Amani, G.A. van Albada, J. Reedijk, Transit. Metal. Chem. 24 (1999)
104e107.
[42] P. Talukder, A. Datta, S. Mitra, G. Rosair, Z. Naturforsch. 59b (2004) 655e660.
[43] C.J. Ballhausen, H.B. Gray, Inorg. Chem. 1 (1962) 111e122.
[44] A.A. Nejo, G.A. Kolawole, A.O. Nejo, T.V. Segapelo, C.J. Muller, Aust. J. Chem. 64
(2011) 1574e1579.
(b) J. Rahchamani, M. Behzad, A. Bezaatpour, V. Jahed, G. Dutkiewicz,
M. Kubicki, M. Salehi, Polyhedron 30 (2011) 2611e2618.
[32] C. Perez, P.M. Bazerque, Acta Biol. Med. Exp. 15 (1990) 113e115.
[33] T. Mosmann, J. Immunol. Methods 65 (1983) 55e63.
[34] M. Azam, Z. Hussain, I. Warad, S.I. Al-Resayes, M.S. Khan, M. Shakir,
A. Trzesowska-Kruszynskae, R. Kruszynski, Dalton Trans. 41 (2012)
10854e10864.
[35] M.R. Mauryaa, A.K. Chandrakar, S. Chand, J. Mol. Cat. A 270 (2007) 225e235.
[36] (a) N.B. Pahor, M. Calligaris, P. Delise, G. Dodic, G. Nardin, L. Randaccio, Dalton
Trans. (1976) 2478e2483;
[45] R. Prabhakaran, A.A. Geetha, M. Thilagavathi, R. Karvembu, V. Krishnan,
H. Bertagnolli, K. Natarajan, J. Inorg. Biochem. 98 (2004) 2131e2140.
ꢁ
[46] F. Baudrion, A. Perichaud, E. Vacelet, Biofouling 14 (2000) 317e331.
[47] N. Dharamaraj, P. Viswanathamurthi, K. Natarajan, Transit. Met. Chem. 26
(2001) 105e109.
[48] R. Malhota, S. Kumar, K.S. Dhindsa, Indian J. Chem. 32A (1993) 457e459.
[49] (a) J.J. Harrison, R.J. Turner, D.A. Joo, M.A. Stan, C.S. Chan, N.D. Allan,
H.A. Vrionis, M.E. Olson, H. Ceri, Antimicrob. Agents Chemother. 52 (2008)
2870e2881;
(b) K. Lippe, D. Gerlach, E. Kroke, J.R. Wagler, Organometallics 28 (2008)
621e629;
(c) A.D. Cort, F. Gasparrini, L. Lunazzi, L. Mandolini, A. Mazzanti, C. Pasquini,
M. Pierini, R. Rompietti, L. Schiaffino, J. Org. Chem. 70 (2005) 8877e8883;
(d) C.-G.F. von Richthofen, A. Stammler, H. Bogge, T. Glaser, J. Org. Chem. 77
(b) S.J. Stohs, D. Bagchi, Free Radic. Biol. Med. 18 (1995) 321e336.
[50] N.A. Amro, L.P. Kotra, K. Wadu-Mesthrige, A. Bulychev, S. Mobashery, G.-Y. Liu,
Langmuir 16 (2000) 2789e2796.
€
(2012) 1435e1448.
[51] P.K. Sasmal, A.K. Patra, M. Nethaji, A.R. Chakravarty, Inorg. Chem. 46 (2007)
11112e11121.
[52] I. Ali, W.A. Wani, K. Saleem, M.-F. Hsieh, RSC Adv. 4 (2014) 29629e29641.
[37] R.M. Claramunt, C. Lopez, M.D. Santa María, D. Sanz, J. Prog. Nucl. Magn.
Reson. Spectrosc. 49 (2006) 169e206.
[38] S.H. Alarcon, A.C. Olivieri, M. Gonzalez-Sierra, J. Chem. Soc. Perkin Trans.
́