Novel Pyrazoline-based Organometallic Compounds Containing Ferrocenyl and Quinoline units: Synthesis, Characterization and Microbial susceptibilities

Article abstract of DOI:10.1002/aoc.4257

Some novel pyrazoline-based organometallic compounds were synthesized as new leads in antimicrobial chemotherapy. The structures of compounds were elucidated by different spectroscopic techniques and elemental analyses. All compounds were investigated for in vitro antimicrobial studies against fifteen ATTC bacterial and fungal strains. The microbial susceptibility of these compounds revealed that all the tested compounds gave good minimum inhibitory concentration (MIC) values against the tested organisms that are either similar or even better than the reference drugs amoxicillin and fluconazole, which gave MIC values 8-64?μg/ml against bacterial and 64?μg/ml against fungal strains, respectively. Among all compounds, compound (4d). 1-(5-(4-chlorophenyl)-3-ferrocenyl-4,5-dihydropyrazol-1-yl)-2-quinolin-8-yloxy) ethanone, emerged out the most promising antimicrobial organometallic derivative with MIC values against all the strains ranging from 8-32?μg/ml. Other compounds gave a range of MIC values between 16-64?μg/ml against S. bovis, 16-32?μg/ml against E. coli, and C. tropicalis except compound (4d) which gave MIC 8?μg/ml against S. bovis and E. coli, whereas 32?μg/ml against C. tropicalis. Collectively, these compounds gave a lower MIC value between 32-64?μg/ml against both of the biofilm forming strains namely, P. aeruginosa and S. mutans. The results of microbial susceptibility concluded that these novel organometallic compounds are new leads in antimicrobial chemotherapy and can be very useful for further optimization work on microbial chemotherapy.

Full text of DOI:10.1002/aoc.4257

Received: 8 November 2017
DOI: 10.1002/aoc.4257
Revised: 5 December 2017
Accepted: 6 December 2017
F U L L P A P E R
Novel Pyrazoline‐based Organometallic Compounds
Containing Ferrocenyl and Quinoline units: Synthesis,
Characterization and Microbial susceptibilities
Humaira Parveen1
| Raedah Aiyed Suliman Alatawi1 | Meshari A. Alsharif1 |
Mohammed Issa Alahmdi1 | Sayeed Mukhtar1 | Salman Ahmad Khan2 | Sadaf Hasan3 |
Asad U. Khan3
1 Department of Chemistry, Faculty of
Some novel pyrazoline‐based organometallic compounds were synthesized as
new leads in antimicrobial chemotherapy. The structures of compounds were
elucidated by different spectroscopic techniques and elemental analyses. All
compounds were investigated for in vitro antimicrobial studies against fifteen
ATTC bacterial and fungal strains. The microbial susceptibility of these com-
pounds revealed that all the tested compounds gave good minimum inhibitory
concentration (MIC) values against the tested organisms that are either similar
or even better than the reference drugs amoxicillin and fluconazole, which gave
MIC values 8‐64 μg/ml against bacterial and 64 μg/ml against fungal strains,
respectively. Among all compounds, compound (4d)
Science, University of Tabuk, Tabuk‐
71491, Kingdom of Saudi Arabia
2 Department of Chemistry, Faculty of
Science, King Abdul Aziz University,
Jeddah, Kingdom of Saudi Arabia
3 Interdisciplinary Biotechnology Unit,
Aligarh Muslim University, Aligarh
202002, India
Correspondence
Humaira Parveen, Department of
Chemistry, Faculty of Science, University
of Tabuk, Tabuk‐71491, Kingdom of Saudi
Arabia.
1‐(5‐(4‐chlorophenyl)‐3‐ferrocenyl‐4,5‐dihydropyrazol‐1‐yl)‐2‐quinolin‐8‐yloxy)
ethanone, emerged out the most promising antimicrobial organometallic deriv-
ative with MIC values against all the strains ranging from 8‐32 μg/ml. Other
compounds gave a range of MIC values between 16‐64 μg/ml against S. bovis,
16‐32 μg/ml against E. coli, and C. tropicalis except compound (4d) which gave
MIC 8 μg/ml against S. bovis and E. coli, whereas 32 μg/ml against C. tropicalis.
Collectively, these compounds gave a lower MIC value between 32‐64 μg/ml
against both of the biofilm forming strains namely, P. aeruginosa and S.
mutans. The results of microbial susceptibility concluded that these novel
organometallic compounds are new leads in antimicrobial chemotherapy and
can be very useful for further optimization work on microbial chemotherapy.
Email: h.nabi@ut.edu.sa
Funding information
Deanship of Scientific Research, Univer-
sity of Tabuk, Saudi Arabia, Grant/Award
Number: S‐0230‐1437
KEYWORDS
antibacterial studies, antifungal studies, ferrocenyl and quinoline units, new leads in microbial
chemotherapy, novel pyrazoline‐based organometallics
1 | INTRODUCTION
medicinal chemists. It has been reported that the presence
of metals influence the properties of a drug, which in turn
Recently, a considerable amount of research on biologi-
cally active organometallic compounds has been
reported[1–6] and has attracted growing interest of
increase or make significant changes in biological activity
with respect to the core drug molecules.[7–13] Extensive
literature survey on ferrocene has revealed that high
Appl Organometal Chem. 2018;e4257.
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Copyright © 2018 John Wiley & Sons, Ltd.
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https://doi.org/10.1002/aoc.4257

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PARVEEN ET AL.
stability, formal oxidation potential, lipophilicity, low tox-
icity and iron redox activity of ferrocene have testified it an
interesting pharmacophore for drug design to develop
more potent and effective curative agents,[14] for example
ferroquine (antimalarial drug) which is in phase II clinical
trials,[15] ferrocifen (anticancer drug),[16] ferrocenyl conju-
gates of antiestrogen tamoxifen[17] and antiandrogen
nilutamide.[18] Recently, some novel ferrocenyl quinolines
have also been reported as useful scaffolds for bioactive
molecule development.[3,19]
Scheme 1. The lead compounds (ferrocenyl chalcones
1a‐1f) were prepared by Claisen–Schmidt condensation
of acetyl ferrocene with substituted aromatic aldehydes
in the presence of potassium hydroxide and absolute
ethanol, according to reported procedure.[46] Compound
(2), ethyl (quinolin‐8‐yloxy) acetate was prepared by
refluxing a mixture of 8‐ hydroxy quinoline, ethyl
chloroacetate and anhydrous potassium carbonate in dry
acetone, which was converted into 2‐(quinolin‐8‐yloxy)
acetohydrazide (3) by it with hydrazine hydrate in the
presence of absolute ethanol.
Moreover, pyrazoline and its derivatives have long
been targeted for synthetic investigations as they possess
a plethora of biological activities such as anti‐inflamma-
tory,[20–26] antimicrobial,[27–31] anti‐fungal,[32] anticancer,[33]
The cyclization of ferrocenyl chalcones with 2‐
(quinolin‐8‐yloxy) acetohydrazide (3) in the presence of
sodium hydroxide and absolute ethanol afforded novel
pyrazoline‐based organometallic compounds (4a‐4f). The
structures of all newly synthesized compounds (4a‐4f)
were established by different spectroscopic techniques
such as Infra Red, Nuclear Magnetic Resonance (1H‐
NMR and 13C NMR spectra) and Mass spectrometry.
The purity of compounds was confirmed by elemental
analysis which was found in accordance with 0.3%.
The Infra‐Red spectra of the target compounds (4d),
showed the characteristic band for (C=N) stretch at
1572 cm‐1 which indicated the formation of ring. Other
characteristic band was observed at 1257 cm‐1 due to the
(C‐N) stretch vibrations which further confirmed the for-
mation of the pyrazoline ring. The bands for (C‐O‐C)
and (C=O) were appeared at 1121 cm‐1 and 1632 cm‐1,
respectively.
antitumor,[34]
antidepressant[35,36]
anticonvulsant,[37]
antiamoebic[38,39] and antibacterial.[40]
On the basis of above observations and as a part of our
ongoing research focused on the synthesis of biologically
active heterocycles/organometallics,[41–45] we have
synthesized some novel pyrazoline‐based organometallic
compounds containing ferrocenyl and quinoline units
and evaluated for in vitro antimicrobial studies against
fifteen ATCC bacterial and fungal stains to investigate
pharmaceutical applications of these compounds.
2 | RESULTS AND DISCUSSION
2.1 | Synthesis and characterization
The synthesis of novel pyrazoline‐based organometallic
compounds (4a‐4f) was performed as illustrated in
The structure of (4d) was further confirmed by its 1H‐
NMR spectrum which provided diagnostic signals for the
(b)
(a)
(c)
(d)
SCHEME 1 General synthesis of
pyrazoline‐based organometallics (4a‐4f)
with ferrocenyl and quinoline units

PARVEEN ET AL.
3 of 8
positional elucidation of the protons. The assignments of
all signals corresponding to individual H‐atom and C‐
atom has been carried out on the basis of typical chemical
shift (δ) values and coupling constants (J).
The C‐4 protons (Ha and Hb) of pyrazoline ring are
geminal protons and appeared
microdilution method.[47,48] For antibacterial studies, 4
Gram‐positive bacteria (S. bovis, E. faecalis, Methicillin‐
resistant S. aureus and S. mutans) and 4 Gram‐negative
bacteria (P. aeruginosa, K. pneumoniae, E. coli, and E. clo-
acae) were used. Amoxicillin was used as a reference drug
to compare antibacterial effect of compounds. It has been
noted that amoxicillin gave a minimum inhibitory con-
centration (MIC) in the range of 8‐64 μg/ml against the
tested bacterial strains. The results of antibacterial activity
revealed that all compounds gave good minimum inhibi-
tory concentration (MIC) values against the tested organ-
isms. Among all compounds, compound (4d) emerged as
the most promising antimicrobial organometallic deriva-
tive with very low MIC values against all the bacterial
strains ranging from 8‐32 μg/ml. Other compounds gave
a range of MIC value between 16‐64 μg/ml against S.
bovis, 16‐32 μg/ml against E. coli, and C. tropicalis except
(4d) which gave MIC 8 μg/ml against S. bovis and E. coli
(similar to amoxicillin), whereas 32 μg/ml against C.
tropicalis. Collectively, these compounds gave a lower
MIC value between 32‐64 μg/ml against both of the
biofilm forming strains namely, P. aeruginosa and S.
mutans. The results of antibacterial assay are mentioned
in Table 1.
at δ 3.69 and δ 3.78 ppm, respectively, as doublet of
doublets in compound (4d).
The C‐5 proton (Hx) of the pyrazoline ring were was
also appeared as doublet of doublets at δ 5.92 ppm due
to vicinal coupling with two non equivalent geminal pro-
tons (Ha and Hb) at C‐4 carbon, suggesting the formation
of pyrazoline ring in organometallic compound (4d). A
singlet at δ 4.92 ppm was appeared and has been assigned
to the ‐OCH2 protons. In addition two singlets were
appeared at δ 4.78 and δ 4.49 ppm, which were attributed
to the four protons of monosubstituted Cp of ferrocenyl
group of the compound (4d). Another characteristic sin-
glet at δ 4.19 ppm was assigned to the five protons of
unsubstituted Cp of ferrocenyl group. All other aromatic
and aliphatic protons were observed with expected chem-
ical shift and integral values and are presented in the data
given in the experimental section.
Further evidence regarding the formation of
pyrazoline‐based organometallic compound (4d) was
obtained by its 13C NMR spectrum. The fourth carbon
(C‐4) and fifth carbon (C‐5) of the pyrazoline ring reso-
nated at δ 44.2 and δ 58.9 ppm, respectively. All com-
pounds also showed a signal at δ 150.9‐154.5 ppm,
attributed to third carbon (C‐3) of pyrazoline ring. The
carbons at ferrocenyl and aromatic rings resonated at
their usual positions and their data are given in the exper-
imental section.
2.3 | In vitro antifungal activity
The antifungal activity of target compounds (4a‐4f) was
screened against seven fungal (Candida albicans‐ ATCC®
18804, Candida dubliniensis‐ ATCC® MYA‐646, Candida
glabrata‐ ATCC® 2001, Candida parapsilosis‐ ATCC®
22019, Candida tropicalis‐ ATCC® 750, Candida kefyr‐
ATCC® 8553 and Candida krusei‐ ATCC® 14243) strains.
Fluconazole was used as reference drug (widely used for
the treatment of Candida infections) to compare antifun-
gal effect of compounds. It has been observed that, flucon-
azole gave a minimum inhibitory concentration (MIC)
value 64 μg/mL against all the tested fungal strains. The
results of antifungal studies suggested that all the tested
compounds gave MIC value either similar or even better
than the reference drug fluconazole, for example, all com-
pounds showed MIC value 64 μg/ml against C.
dubliniensis, which is similar to fluconazole. On the other
hand, Compounds (4a‐4c, 4e) and (4f) exhibited MIC
value 32 μg/ml against C. albicans and C. parapsilosis,
which is better than fluconazole. In case of other fungal
strains, all compounds showed MIC value in the range
of 16‐32 μg/ml except compound (4d) which showed
most promising that is much better antifungal activity
(MIC value 16 μg/mL) against C. albicans, C. dubliniensis,
C. parapsilosis, C. kefyr and C. krusei than the reference
drug fluconazole. The results of antifungal activity are
mentioned in Table 2.
The structure of novel organometallic compound (4d)
was further confirmed by mass spectrometry, which
showed a particular molecular ion [M++1] peak at m/z
550.83 corresponding to its molecular weight.
2.2 | In vitro antimicrobial assay
All novel organometallics (4a‐4f) were evaluated for anti-
microbial activity against fifteen ATCC bacterial (Pseudo-
monas aeruginosa‐ ATCC® 15692™, Streptococcus bovis‐
ATCC® 33317™, Enterococcus faecalis‐ ATCC® 19433™,
Klebsiella pneumoniae‐ ATCC®13883, Escherichia coli‐
ATCC® 11775™, Enterobacter cloacae ATCC® 13047™,
Methicillin‐resistant Staphylococcus aureus‐ ATCC®
33591 and Streptococcus mutans‐ ATCC® 25175™) and
fungal (Candida albicans‐ ATCC® 18804, Candida
dubliniensis‐ ATCC® MYA‐646, Candida glabrata‐ ATCC®
2001, Candida parapsilosis‐ ATCC® 22019, Candida
tropicalis‐ ATCC® 750, Candida kefyr‐ ATCC® 8553 and
Candida krusei‐ ATCC® 14243) strains by broth

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PARVEEN ET AL.
TABLE 1 MIC (μg/ml) values of novel compounds (4a‐4f) on the tested ATCC bacterial strains
4a: R=H, 4b: R=OH, 4c: R=NO2, 4d: R=Cl, 4e: R=OCH3, 4f: R=3,4,5‐TriOCH3.
Codes of
ATCC Bacterial strains
compounds
P. aeruginosa S. bovis E. faecalis K. pneumoniae E. coli E. cloacae MRSA S. mutans
4a
32
32
32
16
32
64
64
32
32
32
8
16
32
16
16
16
32
8
32
32
32
32
32
32
16
32
16
16
8
32
32
64
16
32
32
16
64
32
32
32
32
64
16
32
32
32
16
32
32
64
4b
4c
4d
4e
16
32
8
32
32
8
4f
Amoxicillin
TABLE 2 MIC (μg/ml) values of novel compounds (4a‐4f) on the tested ATCC fungal strains
ATCC Fungal strains
Codes of compounds
C. albicans C. dubliniensis C. glabrata C. parapsilosis C. tropicalis C. kefyr C. krusei
4a
32
32
32
16
32
64
64
32
32
32
8
16
32
16
16
16
32
64
32
32
32
32
32
32
64
32
16
16
8
32
32
64
16
32
32
64
32
32
32
16
64
64
64
4b
4c
4d
4e
16
32
64
32
32
64
4f
Fluconazole
(MIC) values against the tested organisms that are either
similar or even better than the reference drugs amoxicillin
(MIC values 8‐64 μg/mL against the tested bacterial
strains) and fluconazole (MIC values 64 μg/ml against
the tested fungal strains). Compound (4d) was emerged
as the most promising antimicrobial organometallic deriv-
ative with very interesting MIC value against all the
strains ranging from 8‐32 μg/ml. Other compounds gave
a range of MIC value between 16‐64 μg/ml against S.
bovis, 16‐32 μg/ml against E. coli, and C. tropicalis except
(4d) which gave MIC 8 μg/ml against S. bovis and E. coli,
whereas 32 μg/ml against C. tropicalis. Collectively, these
compounds gave a lower MIC value between 32‐64 μg/ml
against both of the biofilm forming strains namely, P.
aeruginosa and S. mutans. These results concluded that
these novel organometallics can be employed as a two in
one formulation to develop potent microbial agents and
3 | CONCLUSION
Some novel pyrazoline‐based organometallic compounds
containing ferrocenyl and quinoline units were synthe-
sized as new leads in antimicrobial chemotherapy. In vitro
antimicrobial activity of compounds was examined by
broth microdilution method against fifteen ATTC (Bacte-
rial: Pseudomonas aeruginosa, Streptococcus bovis, Entero-
coccus faecalis, Klebsiella pneumoniae, Escherichia coli,
Enterobacter cloacae, Methicillin‐resistant Staphylococcus
aureus (MRSA) and Streptococcus mutans; fungal: Can-
dida albicans, Candida dubliniensis, Candida glabrata,
Candida parapsilosis, Candida tropicalis, Candida kefyr
and Candida krusei) strains. The results of antimicrobial
studies suggested that all these organometallics are new
leads in antimicrobial chemotherapy as they exhibited
an extra ordinary minimum inhibitory concentration

PARVEEN ET AL.
5 of 8
can be very useful for further optimization work in micro-
bial chemotherapy.
ethyl chloroacetate (20 mmol) and anhydrous potassium
carbonate (20 mmol) in dry acetone (65 ml) was refluxed
for 10 hours which led to the formation of compound
(2). The resulting solid was filtered, dried under reduced
pressure and crystallized by using ethanol to yield pure
compound (2).
4 | EXPERIMENTAL
Acetylferrocene, substituted aromatic aldehydes, other
chemicals and reagents were purchased from Sigma
Aldrich (St. Louis, MO, USA). Thin‐layer chromatography
(TLC) was performed on precoated aluminum sheets
(silica gel 60 F254, Merck Germany) and spots were
visualized under UV light. Elemental analyses were per-
formed on Heraeus Vario EL III analyzer. The results were
4.3 | General procedure for the synthesis
of 2‐(quinolin‐8‐yloxy) acetohydrazide (3)
The synthesis of 2‐(quinolin‐8‐yloxy) acetohydrazide (3)
was performed according to reported procedure.[49] In a
round bottom flask a mixture of ethyl (quinolin‐8‐yloxy)
acetate (2) (10 mmol), hydrazine hydrate (20 mmol), and
absolute ethanol (100 ml) was refluxed for 5‐6 hours.
The progress of reaction was monitored by TLC. The
resulting solid product was filtered, washed first with
water then with cold ethanol, dried under
within
0.3% of the theoretical values. Melting points
were determined on Thomas Hoover capillary melting
apparatus and are uncorrected. IR spectra were recorded
on Perkin‐Elmer model 1600 FT‐IR RX1 spectrophotome-
1
ter as KBr discs. H NMR and 13C NMR spectra were
recorded on Bruker AVANCE 400 spectrometer using
CDCl3 as solvent with tetramethylsilane (TMS) as internal
standard. Splitting patterns are designated as follows; s,
singlet; d, doublet; m, multiplet. Chemical shift (δ) values
are given in ppm. ESI‐MS was recorded on a MICROMASS
QUATTRO II triple quadrupole mass spectrometer.
4.3.1 | 2‐(Quinolin‐8‐yloxy) acetohydrazide (3)
Yield 85%; m.pt: 140 °C; yellow solid. Analysis calculated
for C11H11N3O2: C 60.80, H 5.12, N 19.28%. Found: C
60.71, H 5.08, N 19.36 %. IR νmax (cm‐1): 3465 (NH,
CONH), 3036 (Ar–H), 2929 (C‐H), 1670 (C=O), 1440
4.1 | General procedure for the synthesis
of ferrocenyl chalcones (1a‐1f)
1
(C=C), 1180 (N–N), 1065 (C‐O‐C); H NMR (CDCl3) δ
Ferrocenyl chalcones (1a‐1f) were synthesized according
to our reported method[46] and their data has been found
in agreement with the reported ones.[46] A mixture of
acetyl ferrocene (6 mmol) and potassium hydroxide
(0.4 g) was dissolved in absolute ethanol (50 ml) and
stirred for 15 minutes at room temperature, then a
solution of substituted aromatic aldehydes (prepared in
absolute ethanol) was added drop wise to the reaction
mixture and was further stirred at room temperature.
The reaction was monitored by TLC on precoated silica
gel sheets. After complete conversion the reaction
mixture was neutralized by 2 M hydrochloric acid
(HCl), leading to the formation of a deep red precipitate
which was filtered and first washed with water alone
several times then with cold ethanol‐water mixture, dried
under reduced pressure to obtain pure respective
ferrocenyl chalcone.
(ppm): 10.6 (s, 1H, CONH), 8.85 (dd, 1H, H‐2′ quinoline,
J2 = 4 Hz, J2′4′= 1.6 Hz), 8.18 (dd, 1H, H‐4′ quinoline,
̍
J
3′4′=8.4 Hz, J2′4′=1.6 Hz), 7.18‐7.53 (m, 4H, quinoline
ring), 4.91 (s, 2H, OCH2), 4.83 (2H, CO NH2); 13C‐NMR
(CDCl3) δ(ppm): 168.4 (C=O), 157.3‐109.6 (Ar‐C), 69.8
(OCH2); ESI‐MS m/z: [M++1] 218.09.
4.4 | General procedure for the synthesis
of novel pyrazoline‐based organometallic
compounds (4a‐4f)
A mixture of ferrocenyl chalcone (1a‐1f) (4.28 mmol), 2‐
(quinolin‐8‐yloxy) acetohydrazide (3) (4.28 mmol) and
sodium hydroxide (10 mmol) in ethanol (100 ml), was
refluxed for 12 hours and progress of reaction was
checked by TLC on precoated silica gel sheets. Afer
completion of reaction, the mixture was cooled and
poured on chilled water leading to the formation of solid
mass which was extracted with petroleum ether (3 ×
50 ml). The organic layer was dried over anhydrous
sodium sulphate. Evaporation of organic solvent under
reduced pressure gave gummy red colored mass which
was recrystallized with acetone and hexane to afford pure
compounds (4a‐4f).
4.2 | General procedure for the synthesis
of ethyl (quinolin‐8‐yloxy) acetate (2)
Ethyl (quinolin‐8‐yloxy) acetate (2) was prepared by
following reported procedure,[49] compared its data with
the reported data and was found in agreement as reported
earlier.[49] A mixture of 8‐ hydroxy quinoline (20 mmol),

6 of 8
PARVEEN ET AL.
(ppm): 8.88 (dd, 1H, H‐2′ quinoline, J2′3′ = 3.6 Hz, J2′4′
=
4.4.1 | 1‐(5‐Phenyl)‐3‐ferrocenyl‐4,5‐
dihydropyrazol‐1‐yl)‐2‐quinolin‐8‐yloxy)
ethanone (4a)
1.6 Hz), 8.22 (d, 1H, H‐4′ quinoline, J3′4′=8.0 Hz), 7.23‐
7.71 (m, 8H, Ar‐H), 6.02 (dd, 1H, Hx, Jax= 4.8, Jbx=11.2 Hz,
pyrazoline), 4.96 (s, 2H, OCH2), 4.75 (s, 2H, ferrocene),
4.41 (s, 2H, ferrocene), 4.21 (s, 5H, ferrocene), 3.81 (dd,
1H, Hb, Jab=16.8, Jbx=11.2 Hz, pyrazoline), 3.62 (dd, 1H,
Ha, Jab=16.8, Jax= 4.8 Hz, pyrazoline); 13C‐NMR (CDCl3)
δ(ppm): 166.2 (C=O), 150.9 (C‐3, pyrazoline), 148.0‐
118.5 (Ar‐C), 80.5 (ipso‐C5H4), 77.3, 77.0 (meta‐C5H4),
76.7, 72.4 (C5H5), 70.9, 70.0 (ortho‐C5H4), 69.6
(CH2), 60.7, 44.1 (C‐5 and C‐4, pyrazoline) ESI‐MS m/z:
[M++1] 561.11.
Yield 72%; m.pt: 119 °C; red solid. Analysis calculated for
C30H25FeN3O2: C 69.91, H 4.89, N 8.15%. Found: C 69.85,
H 4.73, N 8.22 %. IR νmax (cm‐1): 3032 (Ar–H), 2926 (C‐H),
1630 (C=O), 1563 (C=N), 1443 (C=C), 1254 (C–N), 1120
1
(C‐O‐C); H NMR (CDCl3) δ (ppm): 8.85 (dd, 1H, H‐2′
quinoline, J2′3′=4 Hz, J2′4′= 1.6 Hz), 8.18 (d, 1H, H‐4′
quinoline, J3′4′=8.4 Hz), 7.18‐7.74 (m, 9H, Ar‐H), 5.92
(dd, 1H, Hx, Jax= 4.8, Jbx=11.2 Hz, pyrazoline), 4.93 (s,
2H, OCH2), 4.76 (s, 2H, ferrocene), 4.49 (s, 2H, ferrocene),
4.19 (s, 5H, ferrocene), 3.57 (dd, 1H, Hb, Jab=17.4,
Jbx=11.2 Hz, pyrazoline), 3.66 (dd, 1H, Ha, Jab=17.4,
Jax= 4.8 Hz, pyrazoline); 13C‐NMR (CDCl3) δ (ppm):
166.3 (C=O), 151.4 (C‐3, pyrazoline), 148‐110.3 (Ar‐C),
80.8 (ipso‐C5H4), 77.3, 77.0 (meta‐C5H4), 76.7,
72.4 (C5H5), 70.9, 70.0 (ortho‐C5H4), 68.7 (CH2), 60.2,
44.1 (C‐5 and C‐4, pyrazoline) ESI‐MS m/z: [M++1]
516.13.
4.4.4 | 1‐(5‐(4‐Chlorophenyl)‐3‐ferrocenyl‐
4,5‐dihydropyrazol‐1‐yl)‐2‐quinolin‐8‐yloxy)
ethanone (4d)
Yield 81%; m.pt: 189 °C; Red solid. Analysis calculated for
C30H24ClFeN3O3: C 65.53, H 4.40, N 7.64%. Found: C
65.48, H 4.44, N 7.58 %. IR νmax (cm‐1): 3032 (Ar–H),
2927 (C‐H), 1632 (C=O), 1572 (C=N), 1442 (C=C), 1257
(C–N), 1121 (C‐O‐C); 1H NMR (CDCl3) δ (ppm): 8.92
(dd, 1H, H‐2′ quinoline, J2′3′=4.0 Hz, J2′4′= 1.6 Hz), 8.21
(d, 1H, H‐4′ quinoline, J3′4′=8.4 Hz), 7.24‐7.75 (m, 8H,
Ar‐H), 5.92 (dd, 1H, Hx, Jax= 4.8, Jbx=11.7 Hz,
pyrazoline), 4.91 (s, 2H, OCH2), 4.78 (s, 2H, ferrocene),
4.49 (s, 2H, ferrocene), 4.19 (s, 5H, ferrocene), 3.78 (dd,
1H, Hb, Jab=16.8, Jbx=11.7 Hz, pyrazoline), 3.69 (dd, 1H,
Ha, Jab=16.8, Jax= 4.8 Hz, pyrazoline); 13C‐NMR (CDCl3)
δ(ppm): 165.5 (C=O), 154.2 (C‐3, pyrazoline), 147.9‐
106.9 (Ar‐C), 80.6 (ipso‐C5H4), 77.3, 77.0 (meta‐C5H4),
76.7, 72.7 (C5H5), 70.1, 69.7 (ortho‐C5H4), 66.5
(CH2), 58.9, 44.2 (C‐5 and C‐4, pyrazoline) ESI‐MS m/z:
[M++1] 550.83.
4.4.2 | 1‐(5‐(4‐Hydroxyphenyl)‐3‐
ferrocenyl‐4,5‐dihydropyrazol‐1‐yl)‐2‐
quinolin‐8‐yloxy) ethanone (4b)
Yield 78%; m.pt: 224 °C; Maroon solid. Analysis calcu-
lated for C30H25FeN3O3: C 67.81, H 4.74, N 7.91%. Found:
C 67.85, H 4.4.86, N 7.98 %. IR νmax (cm‐1): 3036 (Ar–H),
2924 (C‐H), 1634 (C=O), 1571 (C=N), 1448 (C=C), 1257
1
(C–N), 1114 (C‐O‐C); H NMR (CDCl3) δ (ppm): 8.87
(dd, 1H, H‐2′ quinoline, J2′3′= 3.9 Hz, J2′4′= 1.6 Hz), 8.19
(d, 1H, H‐4′ quinoline, J3′4′=8.0 Hz), 7.24‐7.70 (m, 8H,
Ar‐H), 6.31 (dd, 1H, Hx, Jax= 4.2, Jbx=11.2 Hz,
pyrazoline), 4.95 (s, 2H, OCH2), 4.72 (s, 2H, ferrocene),
4.69 (s, 1H, OH), 4.42 (s, 2H, ferrocene), 4.19 (s, 5H, ferro-
cene), 3.74 (dd, 1H, Hb, Jab=17.4, Jbx=11.2 Hz,
pyrazoline), 3.65 (dd, 1H, Ha, Jab=17.4, Jax= 4.2 Hz,
pyrazoline); 13C‐NMR (CDCl3) δ(ppm): 165.9 (C=O),
151.2 (C‐3, pyrazoline), 148.2‐116.4 (Ar‐C), 80.5 (ipso‐
C5H4), 77.2, 77.0 (meta‐C5H4), 76.7, 72.8 (C5H5), 70.1,
69.7 (ortho‐C5H4), 68.2 (CH2), 61.2, 44.1 (C‐5 and C‐4,
pyrazoline) ESI‐MS m/z: [M++1] 532.12.
4.4.5 | 1‐(5‐(4‐Methoxyphenyl)‐3‐
ferrocenyl‐4,5‐dihydropyrazol‐1‐yl)‐2‐
quinolin‐8‐yloxy) ethanone (4e)
Yield 72%; m.pt: 210 °C; Deep red solid. Analysis calcu-
lated for C31H27FeN3O3: C 68.27, H 4.99, N 7.70 %. Found:
C 68.21, H 4.90, N 7.68 %. IR νmax (cm‐1): 3034 (Ar–H),
2924 (C‐H), 1636 (C=O), 1571 (C=N), 1445 (C=C), 1253
(C–N), 1120 (C‐O‐C); 1H NMR (CDCl3) δ (ppm): 8.91
(dd, 1H, H‐2′ quinoline, J2′3′=3.6 Hz, J2′4′= 1.6 Hz), 8.23
(d, 1H, H‐4′ quinoline, J3′4′=8.4 Hz), 7.22‐7.74 (m, 8H,
Ar‐H), 5.99 (dd, 1H, Hx, Jax= 4.2, Jbx=11.7 Hz,
pyrazoline), 4.92 (s, 2H, OCH2), 4.79 (s, 2H, ferrocene),
4.45 (s, 2H, ferrocene), 4.21 (s, 5H, ferrocene), 3.86 (s,
3H, OCH3), 3.75 (dd, 1H, Hb, Jab=18.0, Jbx=11.7 Hz,
pyrazoline), 3.67 (dd, 1H, Ha, Jab=18.0, Jax= 4.2 Hz,
pyrazoline); 13C‐NMR (CDCl3) δ(ppm): 161.3 (C=O),
152.9 (C‐3, pyrazoline), 147.9‐115.2 (Ar‐C), 80.2 (ipso‐
4.4.3 | 1‐(5‐(4‐Nitrophenyl)‐3‐ferrocenyl‐
4,5‐dihydropyrazol‐1‐yl)‐2‐quinolin‐8‐yloxy)
ethanone (4c)
Yield 61%; m.pt: 255 °C; Dark red solid. Analysis calcu-
lated for C30H24FeN4O4: C 64.30, H 4.32, N 10.01 %.
Found: C 63.78, H 4.44, N 10.15 %. IR νmax (cm‐1): 3031
(Ar–H), 2929 (C‐H), 1630 (C=O), 1575 (C=N), 1441
1
(C=C), 1255 (C–N), 1119 (C‐O‐C); H NMR (CDCl3) δ

PARVEEN ET AL.
7 of 8
C5H4), 77.3, 77.0 (meta‐C5H4), 76.9, 71.7 (C5H5), 70.9,
70.2 (ortho‐C5H4), 69.0 (CH2), 60.6 (C‐5 pyrazoline), 55.5
(O‐ CH3), 43.9 (C‐4, pyrazoline) ESI‐MS m/z: [M++1]
546.41.
5.1 | Determination of minimum
inhibitory concentration (MIC)
The minimum inhibitory concentration (MIC) was deter-
mined by using a broth microdilution method.[48] Stock
standard solutions at 2 mg/ml were prepared in DMSO
for all the compounds to be tested. Working solutions
were prepared by dilution in microtiter plates at concen-
trations between 512 μg/ml and 0.244 μg/mL using nutri-
ent medium as the diluent. DMSO (50 μL) was used as
control and did not show any inhibitory activity. The bac-
terial suspension for each strain was added in the wells of
the microtiter plate at the concentration of 105‐106 cfu/ml
(colony forming units/ml). Each inoculum was prepared
in its respective medium and was diluted to 1:100 for
the broth micro dilution procedure. The plates were
incubated at 37 °C with bacterial strains and at 30 °C for
fungal stains and the minimum inhibitory concentration
(MIC) was recorded after 24 hours. Bacterial and fungal
growth was shown by the presence of turbidity in the
wells. The MIC was determined as the lowest concentra-
tion of the compound that completely inhibited the visible
bacterial/fungal growth (turbidity) of the organism after
24 hour of incubation. All these determinations represent
the mean of three independent experiments. The results
of antimicrobial activity are summarized in Table 1 and
Table 2.
4.4.6 | 1‐(5‐(3,4,5‐Trimethoxyphenyl)‐3‐
ferrocenyl‐4,5‐dihydropyrazol‐1‐yl)‐2‐
quinolin‐8‐yloxy) ethanone (4f)
Yield 69%; m.pt: 212 °C; reddish solid. Analysis calculated
for C33H31FeN3O5: C 65.46, H 5.16, N 6.94 %. Found:
C 65.39, H 5.22, N 6.97 %. IR νmax (cm‐1): 3030 (Ar–H),
2922 (C‐H), 1635 (C=O), 1574 (C=N), 1448 (C=C),
1255(C–N), 1120 (C‐O‐C); 1H NMR (CDCl3) δ (ppm):
8.90 (dd, 1H, H‐2′ quinoline, J2′3′=4.0 Hz, J2′4′= 1.6 Hz),
8.24 (d, 1H, H‐4′ quinoline, J3′4′=8.4 Hz), 7.24‐7.68
(m, 6H, Ar‐H), 6.17 (dd, 1H, Hx, Jax= 4.8, Jbx=11.7 Hz,
pyrazoline), 4.94 (s, 2H, OCH2), 4.78 (s, 2H, ferrocene),
4.41 (s, 2H, ferrocene), 4.22 (s, 5H, ferrocene), 3.87
(s, 6H, 2 × OCH3), 3.82 (s, 3H, OCH3) 3.68 (dd, 1H, Hb,
Jab=18.0, Jbx=11.7 Hz, pyrazoline), 3.52 (dd, 1H, Ha,
Jab=18.0, Jax= 4.8 Hz, pyrazoline); 13C‐NMR (CDCl3)
δ(ppm): 162.8 (C=O), 152.4 (C‐3, pyrazoline),
147.9‐119.5 (Ar‐C), 80.6 (ipso‐C5H4), 77.3, 77.1(meta‐
C5H4), 76.8, 72.7 (C5H5), 70.1, 69.8 (ortho‐C5H4),
696.2 (CH2), 59.5 (C‐5 pyrazoline), 55.8 (3×O‐CH3), 44.6
(C‐4, pyrazoline) ESI‐MS m/z: [M++1] 606.46.
ACKNOWLEDGEMENTS
The authors would like to thank, the Deanship of
Scientific Research, University of Tabuk, Tabuk, Saudi
Arabia for the financial support for this research work
via Grant No. S‐0230‐1437.
5 | IN VITRO ANTIMICROBIAL ASSAY
All novel organometallics (4a‐4f) were investigated for
antimicrobial studies against eight bacterial (Pseudomo-
nas aeruginosa, Streptococcus bovis, Enterococcus faecalis,
Klebsiella pneumoniae, Escherichia coli, Enterobacter cloa-
cae, Methicillin‐resistant Staphylococcus aureus and
Streptococcus mutans) and seven fungal (Candida
albicans, Candida dubliniensis, Candida glabrata,
Candida parapsilosis, Candida tropicalis, Candida kefyr
and Candida krusei)) strains by broth microdilution
method.[48] Inocula were prepared from an overnight
nutrient broth culture plate of the bacterial test strains
and yeast peptone dextrose (YPD) culture plate for fungal
test organisms (Himedia Labs, Mumbai, India). Inoculum
for the minimum inhibitory concentration (MIC) test
was prepared by taking two or three considerably
isolated colonies from respective agar culture plate. These
colonies were picked up by a sterile loop and were
transferred into a tube containing 4 to 5 ml of respective
sterile liquid medium. This broth was incubated at
37 °C until it attained a desired turbidity.[47]
ORCID
Humaira Parveen http://orcid.org/0000-0001-8365-0014
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How to cite this article: Parveen H, Alatawi
RAS, Alsharif MA, et al. Novel Pyrazoline‐based
Organometallic Compounds Containing Ferrocenyl
and Quinoline units: Synthesis, Characterization
and Microbial susceptibilities. Appl Organometal
Chem. 2018;e4257. https://doi.org/10.1002/aoc.4257
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