A theoretical insight for solvent effect on myoglobin assay of W(CO)4L2 type novel complexes with DFT/TDDFT

Article abstract of DOI:10.1016/j.molstruc.2016.07.002

Novel tetracarbonyl complexes of type W(CO)₄L₂ (L: 4-chlorobenzylimidazoline; 4-methylbenzylimidazoline; 3,5-dimethylbenzylimidazoline; 2,4,6-trimethylbenzylimidazoline; 2,3,5,6- tetramethylbenzylimidazoline) were synthesized. Then n

Full text of DOI:10.1016/j.molstruc.2016.07.002

Journal of Molecular Structure 1123 (2016) 433e440
Contents lists available at ScienceDirect
Journal of Molecular Structure
journal homepage: http://www.elsevier.com/locate/molstruc
A theoretical insight for solvent effect on myoglobin assay of W(CO)4L2
type novel complexes with DFT/TDDFT
,
*
b
b
b
c
Elvan Üstün a , Serpil Demir , Feyzullah Cos¸ kun , Murat Kaloglu , Onur S¸ ahin ,
ꢀ
d
b
_
€
€
Orhan Büyükgüngor , Ismail Ozdemir
a Department of Chemistry, Faculty of Art and Science, Ordu University, 52200, Ordu, Turkey
Department of Chemistry, Faculty of Science, Inonü University, 44280, Malatya, Turkey
c Sinop University, Scientific and Tech. Research Application and Research Center, 57000, Sinop, Turkey
d Ondokuz Mayıs University, Department of Physics, 55139, Samsun, Turkey
b
_
€
a r t i c l e i n f o
a b s t r a c t
Article history:
Novel tetracarbonyl complexes
of
type
W(CO)4L2
(L:
4-chlorobenzylimidazoline;
4-
Received 4 May 2016
Received in revised form
30 June 2016
Accepted 1 July 2016
Available online 6 July 2016
methylbenzylimidazoline; 3,5-dimethylbenzylimidazoline; 2,4,6-trimethylbenzylimidazoline; 2,3,5,6-
tetramethylbenzylimidazoline) were synthesized. Then newly synthesized novel compounds were
characterized by IR, 1H NMR, 13C NMR and LC-MS. The characterizations of two of the complexes have
also been confirmed with single crystal X-Ray diffraction and DFT optimization results of these com-
plexes have been compared with single crystal results. We have investigated the solvent effect on the
structure and metal-to-ligand charge transfer (MLCT) transitions with DFT/TDDFT calculations with
ORCA package program with BP86 functional.
Keywords:
PhotoCORMs
Imidazoline
© 2016 Elsevier B.V. All rights reserved.
CO-releasing molecules
DFT/TDDFT
Tungsten carbonyl complexes
1. Introduction
Therefore, exogenous CO supplement is being accepted as an
effective therapeutic way. Clinical trials using CO gas administered
Metal carbonyl complexes are important milestones in devel-
opment of organometallic chemistry. Although early metal car-
bonyls were mostly used as catalyst [1], pharmaceutical
applications of recent carbonyl complexes have accelerated the
researches. Several practical applications of these complexes have
to patients by inhalation through the lungs are insecure for both the
patients and the medical staff due to the inability to control de-
livery of CO [11]. Therefore, CO-releasing molecules (CORMs)
became a reliable way out and metal carbonyl complexes are the
most promising candidates for this mission [12e24]. There are
been tested for probes in polymerization processes [2], labeling of
various ways to ensure CO-release, one of which is to irradiate the
̇
̇
biomolecules [3], and exploitation of solar energy [4]. The interest
complexes with UV-light with certain wavelength. These kinds of
dark-stable and light-sensitive complexes are called as photo-
CORMs [25e31].
̇
in these metal carbonyl complexes was reanimated after the recent
publications by Motterlini et al. [5] who carried out CO-releasing
properties of certain complexes of this family and this is the main
subject of this manuscript.
Carbon monoxide (CO) is produced during the degradation of
heme by the enzyme heme oxygenase [6,7], even though it is
known as a toxic gas. The studies which shown the increment of the
ratio of CO in case of illness [8e10] gave rise to new researches
about bioactivity analyses of CO and have received considerable
attention after the favorable results about functions of CO in tissue.
Myoglobin assay is the most commonly used method for
measuring CO-releasing properties of carbonyl complexes. It is
principally based on following the transformation of deoxy-
myoglobin to carbonmonoxy-myoglobin by UVeVis Spectropho-
tometer [5]. The photoCORMs have to be sensitive to certain
wavelength of UV/Vis light but dark-stable in used solvent or sol-
vent systems. Electronic transitions of molecules are the major
landmark to make decision for proper wavelength of UV lamp. A
photoCORM which has maxima on longer wavelength (preferably
visible region) of UV spectra could be stimulated with a lower en-
ergy UV-lamp and is more advantageous for possible therapeutic
* Corresponding author.
E-mail address: elvanustun77@gmail.com (E. Üstün).
http://dx.doi.org/10.1016/j.molstruc.2016.07.002
0022-2860/© 2016 Elsevier B.V. All rights reserved.

434
E. Üstün et al. / Journal of Molecular Structure 1123 (2016) 433e440
applications [32]. Moreover, the darkstability and the electronic
transitions of molecules depend on solvent. Therefore, it is impor-
tant to have an insight about possible effect of solvents for reliable
results and also to keep from waste of time, source, and labor.
The secondary ligands of CORMs have an influence on rate and
amount of releasing CO and also solubility and stability of com-
plexes. These ligands which also remain residual in tissue must be
selected carefully. Furthermore, the well-selected ligands could
strengthen the bioactivity synergistically. Imidazoline which is a
prominent class of organic chemistry is an important bioactive
molecule. Many imidazoline derivatives have been investigated as
antihyperglycemic, antiinflammatory, antihypertensive, anti-
hypercholesterolemic, and antidepressant reagents [33e39]. It
should be also noted here that peripheral groups which can easily
be substituted imidazoline changes the chemistry of both imida-
zoline and main organometallic compound.
even could be obtained commercially [53], imidazoline forms
which were used in this study have not been encountered in any
scientific papers. The most effective method for characterization
-like many organic molecules-is 1H NMR spectroscopy. Triplets for
dorsal CH2-CH2 part of imidazoline are characteristic and have
come out between 2.85 and 3.82 ppm. Measured singlets between
6.70 and 7.03 ppm for NCHN and 3.98e4.12 ppm for elbow CH2
connection of imidazoline-phenyl are also obvious evident. Addi-
tionally, the 1H NMR signals for CH3 on benzyl rings, 13C NMR shifts
and IR bands for all imidazoline ligands have been observed as
expected. The characterization of ligands also have confirmed by
elemental analysis.
Although only small changes are expected in 1H NMR spectra of
complexes, carbonyls’ carbons could be observed in 13C NMR. Three
carbonyl shifts were recorded for 1 and 4 by chemical surrounding
of carbonyl, but 2 and 3 had two signals while 5 had only a single
one in 204.8 ppm. IR spectroscopy is a valuable method because of
the unique bands of metal carbonyls and IR spectra of complexes
have exhibited three absorption bands of the appropriate intensity
pattern for the M(CO)4 fragment of C2V local symmetry. The IR
bands and LC-MS spectra of all complexes have confirmed the
estimated structures.
The structures of 4 and 5 were additionally established by X-Ray
structural analysis. The ORTEP drawing of 4 is shown in Fig. 2.
Complexes 4 and 5 have distorted octahedral geometries and the
imidazoline ligands were bonded to tungsten with cis-geometry.
The crystallographic parameters of the molecules are given in
Table 1.
The ORCA program package with the RI-BP86 and a TZV basis set
were used for theoretical geometry optimization of all complexes.
Some calculated bond lengths and angles of 4 and 5 have been
compared with single crystal X-Ray results (Table 2). The deviations
between calculated bond lengths and those obtained by crystal-
lography have been recorded in 0.02 Å, while bond angle de-
viations do not exceed 2.1%, in absolute terms, less than 3.85ꢀ.
These results mean that ORCA package with these functionals could
be used for calculation of structural parameters of all this kind of
molecules, so the Cartesian coordinates of all studied molecules
were given in Supporting Information part for possible further
studies.
UVeVis spectroscopy is major for in-vitro bioactivity studies of
organometallic compounds (i.e., antioxidant activity, CO-releasing
activity), but the spectra of compounds are appraised negligible
because of generally used indirect measurement methods. How-
ever, each compound has differences with regard to stability and
UV bands in different solvents and this is an important deficiency of
methods which irradiation used in. In this study, we especially
wanted to have an insight about the solvent effects on photo-
CORMs; because the reliable wavelength in CO-releasing analyzing
process is selected according to UVeVis maxima of molecule which
depends on the solvent used. The complex 1 displayed maxima on
321 nm in DMSO and on 288 nm in acetonitrile while complex 3
Irradiation into the low-lying metal-to-ligand charge transfer
(MLCT) bands, which belong to transitions from the metal to the
lowest p* orbital of the ligand, may give rise to photodissociation of
carbonyl ligand and this is, in fact, the main mechanism of CO
release with UV-light. An understanding of photochemistry of
transition metal compounds requires knowledge of the properties
of molecular orbitals, spectra and appropriate excited states. Den-
sity functional theory (DFT) and time-dependent DFT approach
(TDDFT) plays a crucial role in characterization of the excited states
coordination complexes [40e45]. Furthermore, applications of
TDDFT approaches have recently been reported on transition metal
complexes and got good results. Structures and electronic transi-
tions predicted with the popular BP86 functional are no worse or in
many cases are even slightly better than those predicted by the
hybrid B3LYP functional [46e51].
The main objective of this study is to investigate the solvent
effects on MLCT transitions of potential photoactivatable CO-
releasing molecules with theoretical methods. For this purpose,
we synthesized novel tetracarbonyl complexes of type W(CO)4L2 [L:
4-chlorobenzylimidazoline (L1), 4-methylbenzylimidazoline (L2),
3,5-dimethylbenzylimidazoline
trimethylbenzylimidazoline
(L3),
(L4),
2,4,6-
2,3,5,6-
tetramethylbenzylimidazoline (L5)]. The molecules were charac-
terized by IR, 1H NMR, 13C NMR and LC-MS. The characterizations
of two of the molecules have also been confirmed by single crystal
X-Ray diffraction. DFT optimization results of these two complexes
were also compared with the single crystal characteristics. The
solvent effects on the structure and MLCT transitions have been
investigated with DFT/TDDFT calculations using ORCA package
program [41,46e48].
2. Discussion
Imidazoline ligands (Fig. 1) were synthesized as in method of
Çetinkaya et al. [52] with high yield (80e90%) and characterized.
Although imidazole form of ligands were synthesized before and
Positions
Ligand
L1
2
H
3
H
4
Cl
5
H
6
H
L2
H
H
CH3
H
H
H
L3
H
CH3
H
CH3
H
H
L4
CH3
CH3
CH3
H
CH3
CH3
L5
CH3
CH3
Fig. 1. Imidazoline derivative ligands of type W(CO)4L2 complexes.

E. Üstün et al. / Journal of Molecular Structure 1123 (2016) 433e440
435
Fig. 2. An ORTEP drawing of 4 with the atomic numbering scheme.
Table 1
Table 2
Crystallographic parameters of 4 and 5.
Selected experimental and calculatedb molecular parameters (bond lengths and
angles) for 4 and 5 in gas phasea.
4
5
4
5
Empirical Formula
Formula weight
Dimensions (mm)
Crystal system
Space group
a (Å)
C
30H36N4O4W
C32H40N4O4W
728.53
0.44 ꢁ 0.39 ꢁ 0.16
Monoclinic
P2 1/c
8.9422 (3)
19.1742 (6)
18.5366 (7)
90
92.474 (3)
90
3175.31 (19)
4
1.524
296
3.68
700.49
Experimental
Theoretical
Experimental
Theoretical
0.539 ꢁ 0.324 ꢁ 0.184
Monoclinic
C 12/c1
14.8659 (8)
9.0291 (4)
23.1920 (11)
90
105.455 (1)
90
3000.4 (3)
4
1.5506
100
3.889
0.71073
28.29
W1eC1
W1eC2
C1eO1
C2eO2
W1eN1
N1eC3
N2eC6
C6eC7
C1eW1eC2
C1eW1eC1i
N1eW1eN1i
N1eW1eC1
N1eW1eC2
W1eC1eO1
N1eC3eN2
N2eC6eC7
2.03(19)
1.95(19)
1.15(2)
1.17(2)
2.23(15)
1.29(2)
2.02
1.96
1.20
1.20
2.23
1.32
1.48
1.52
85.95
171.06
84.03
92.20
176.16
178.14
116.18
113.60
2.01(6)
1.96(5)
1.17(7)
1.16(6)
2.24(3)
1.29(5)
1.45(6)
1.52(7)
87.80(2)
169.00(2)
81.44(14)
96.06(19)
177.62(16)
171.50(5)
117.50(4)
112.40(4)
2.02
1.96
1.20
1.20
2.24
1.32
1.48
1.52
86.31
167.07
84.20
94.00
175.70
170.90
116.30
113.80
b (Å)
c (Å)
a
b
g
(ꢀ)
(ꢀ)
(ꢀ)
1.46(2)
1.51(3)
86.31(7)
171.64(11)
80.18(8)
92.39(6)
176.37(7)
176.83(17)
116.81(16)
112.67(15)
V (Å3)
Z
rcalc (g cmꢂ3
T (K)
)
m
(mmꢂ1
)
l
(Å) (Mo Ka)
Qmax (ꢀ)
0.71073
27.1
20751
7001/5236
371
2
Reflection measured
Unique refl./[(I ꢃ 2u(I)]
Variables
16190
3733/3578
179
a
Bond lengths in Angstrom and bond angles in degrees.
Computed at the RI-BP86/TZV (ZORA) level of theory.
b
R (I> ¼ 2u(I))
0.0157
0.0352
0.4876/ꢂ1.2653
0.066
0.084
1.04/ꢂ1.31
wR (I> ¼ 2u(I))
Largest different map
peak/hole in e Å3-
reported and contributions >20% are listed in tables. In methanol,
HOMO of molecule intensively consists of transition metal orbitals
while LUMO is formed completely from carbonyl orbitals, thus the
HOMO-LUMO transition is a kind of MLCT which is expected to
occur in 570.6 nm theoretically, but this transition could not be
observed in UV-spectra practically because of weak oscillation
strength. Electronic states with highest oscillating force are state 24
and state 31 in which electrons flow from metal to imidazoline and
these states mostly include HOMO-1 / LUMO þ 7 and HOMO-
1 / LUMO þ 8, respectively (Table 4). However, the highest oscil-
lator transition of the same molecule in hexane consists of electron
flow completely from carbonyl to imidazoline and is entirely in-
dependent from tungsten atom (Table 5). Electronic transition an-
alyses for all five molecules in hexane, methanol and DMF could be
also seen in Supporting Information files.
The MLCT energies are very sensitive to the nature of solvent.
The wavelength of MLCT absorption depends on solvent type in
addition to solvent polarity. We also analyzed how the solvent
affected the HOMO-LUMO transition energy and the energy levels
of frontier orbitals (Fig. 4). The molecule 2 was analyzed exemplary,
there were no clear differences between energy levels in gas phase
and in hexane, but acetonitrile evidently reduced the energies of
frontier orbitals. HOMO-LUMO energy gap was evaluated for
had maxima on 320 nm in DMSO, on 296 nm in toluene, and on
253 nm in ethyl acetate (Fig. 3a, Table S1). On the other hand, the
darkstability of the molecules in different solvents changes the CO-
releasing capacity and this could be a shadow on reliability of ex-
periments and used method (Fig. 3b). There are some restrictions
on the choice of solvents in biochemical texts [54,55] and it is
obvious that CO-releasing analysis process of photoCORMs must be
evaluated according to solvent alteration.
All five molecules were structurally optimized by DFT with
ORCA package taking into account eight different organic solvents
(acetonitrile, carbon tetrachloride, dimethylformamide, hexane,
methanol, tetrahydrofuran, toluene and, water) with COSMO model
and some bond lengths and angles of 4 were compared with each
other in Table 3. Tungsten compounds containing aromatic ligands
usually exhibit intense metal-to-ligand charge transfer (MLCT)
transitions in UVeVis spectrum. Electronic transitions and
contributor molecular orbitals were analyzed firstly with the aim of
providing the participation to spectra bands in different solvents.
Only strong transitions with an oscillator strength >0.01 are

436
E. Üstün et al. / Journal of Molecular Structure 1123 (2016) 433e440
Fig. 3. Solvent effects on UVeVis spectra (a) and darkstability (b) of 3.
without further purification. All reactions were carried out under
an atmosphere of pure argon by using standard Schlenk and vac-
uum techniques. Solvents were freshly distilled after refluxing over
metallic sodium or phosphorous pentoxide for 3e4 days. IR spectra
were recorded on pure solid samples with a Shimadzu IRAffinity-1
ATR spectrometer. Intensities of stretching vibrations were marked
as strong(s), medium (m), weak (w), or shoulder (sh). NMR spectra
were recorded on a Bruker Ultra Shield 300 MHz spectrometer.
Table 3
Comparison of calculatedb selected bond lengths and anglesa for 4 in different sol-
vents with experimental values from X-ray analysis.
Exp.
CCl4
MeOH
Acetonitrile
W1eC1
W1eC2
C1eO1
C2eO2
W1eN1
N1eC3
N2eC6
C6eC7
C1eW1eC2
C1eW1eC1i
N1eW1eN1i
N1eW1eC1
W1eC1eO1
N1eC3eN2
N2eC6eC7
2.03(19)
1.95(19)
1.15(2)
1.17(2)
2.23(15)
1.29(2)
2.017
1.958
1.200
1.206
2.233
1.323
1.478
1.518
84.9
166.2
82.8
95.2
170.2
116.1
113.6
2.017
1.955
1.202
1.212
2.221
1.326
1.480
1.518
84.5
163.9
82.0
96.1
168.1
116.1
113.6
2.017
1.955
1.201
1.212
2.220
1.327
1.480
1.518
84.1
163.9
82.0
96.0
168.1
116.1
113.6
Chemical shifts
d in parts per million indicate a downfield shift
relative to tetramethylsilane (TMS) and were referenced relative to
the signal of the solvents. Coupling constants J are given in hertz.
Individual peaks are marked as singlet (s), doublet (d), triplet (t), or
multiplet (m). Absorption spectra were measured using a Shimadzu
UV-1800 in quartz cuvettes (d ¼ 1 cm). Elemental analysis (C, H,
and N) of ligands was carried out using a CHNS-932 (LECO).
1.46(2)
1.51(3)
86.31(7)
171.64(11)
80.18(8)
92.39(6)
176.83(17)
116.81(16)
112.67(15)
4.2. Synthesis of ligands
a
Bond lengths in Angstrom and bond angles in degrees.
Computed at the RI-BP86/TZV (ZORA)/COSMO level of theory.
b
All ligands were prepared by similar methods. Small pieces of
lithium (45 mmol, 312 mg) were added slowly to ethylene diamine
at 110 ꢀC. The solution was allowed to reach room temperature after
stirring for 1 h and n-alkylbenzylchloride (50 mmol) and toluene
(40 mL) were added. Precipitated lithium chloride was filtered and
the N-(n-alkylbenzyl)ethylenediamine was isolated by distillation
from the oily mixture (120 ꢀC/0.01 mmHg) after solvents were
removed under vacuum. N-(n-alkylbenzyl)ethylenediamine
(35 mmol) and N,N-dimethylformamide dimethylacetal (40 mmol)
were stirred for 2 h at 100 ꢀC and methanol and dimethyl amine
were separated at 120 ꢀC by distillation. The last product was iso-
lated from yellow oily residue by distillation under vacuum (124 ꢀC/
0.01 mmHg).
molecule 2, and also for all molecules in all eight solvents in this
study. In fact, we could not see a meaningful relation depending on
solvents, dipole moments, and dielectric constants; but there are
lots of theoretical studies for catching an equation between a mo-
lecular parameter and HOMO-LUMO transition energy and our
calculation results were added to Supporting Information for
possible further studies of other groups (Table S16).
3. Conclusion
We have synthesized four novel tungsten carbonyl complexes of
type W(CO)4L2 with imidazoline derivative ligands. These com-
pounds were fully characterized by spectroscopic methods. We
have investigated frontier molecular orbitals, electronic transitions,
and singlet excitation density differences of the compounds by
using DFT/TDDFT methods. The results confirm that increment of
4.2.1. N-4-chlorobenzylimidazoline [L1]
1H NMR
(
d,
300 MHz, CDCl3): 3.03 (t, 2H, J ¼ 9.75 Hz,
NCH2CH2N), 3.76 (t, 2H, J ¼ 9.78 NCH2CH2N), 4.18 (s, 2H,
NCH2C6H4Cl-4), 7.14 and 7.25 (d, J ¼ 8.4 Hz, 4H, NCH2C6H4Cl-4), 6.89
p-back bonding leads to deceleration of CO release and the ancil-
(s, 1H, NCHN). 13C NMR
(d, 75 MHz, CDCl3): 48.1 and
lary ligands play remarkable role in the W-CO bond labialization
process.
51.1(NCH2CH2N), 55.2 (NCH2C6H4Cl-4), 128.8, 129.1, 133.3 and 135.6
(NCH2C6H4Cl-4), 157.3 (NCHN). Anal. Calc. for C11H14N2Cl (194.06):
C, 61.70; H, 5.70; N, 14.39. Found: C, 61.68; H, 5.73; N, 14.38%.
4. Material and method
4.1. General remarks
4.2.2. N-4-methylbenzylimidazoline [L2]
1H NMR (
d
, 300 MHz, CDCl3): 2.13 (s, 3H, NCH2C6H4(CH3)-4),
All chemicals were purchased from Sigma Aldrich and used
3.98 (s, 2H, NCH2C6H4(CH3)-4), 6.90e6.93 (m, 4H, NCH2C6H4(CH3)-

E. Üstün et al. / Journal of Molecular Structure 1123 (2016) 433e440
437
Table 4
Energies (in nm), Oscillator Strength (fosc), Main Orbital Contributions, and Type of Transition Involved in the Most Important Singlet Excitations for 3 in Methanol Calculated
with TDDFT/BP86.
State
1
Molecular orbitals
Main transitions
11
12
18
19
24
31
4), 2.85 and 3.58 (t, J ¼ 9.8 Hz, 4H, NCH2CH2N), 6.70 (s, 1H, NCHN).
13C NMR (
, 75 MHz, CDCl3): 21.11 (NCH2C6H4(CH3)-4), 55.18
4.2.3. N-3,5-dimetylbenzylimidazoline [L3]
1H NMR (
, 300 MHz, CDCl3): 2.30 and 2.40 (s, 6H, 3,5-
d
d
(NCH2C6H4(CH3)-4), 127.76, 128.23, 129.03, 129.37, 133.93, 137.33
(NCH2C6H4(CH3)-4), 50.03 and 51.46 (NCH2CH2N), 157.52 (NCHN).
Anal. Calc. for C11H14N2 (174.12): C, 75.82; H, 8.10; N, 16.08. Found:
C, 75.83; H, 8.08; N, 16.06%.
CH2C6H3(CH3)2), 4.12 (s, 2H, 3,5-CH2C6H3(CH3)2), 6.72 (s, 2H, 3,5-
CH2C6H3(CH3)2), 6.81 (s, 1H, 3,5-CH2C6H3(CH3)2), 3.11 and 3.58 (t,
J ¼ 9.6 Hz, 4H, NCH2CH2N), 7.03 (s, 1H, NCHN). 13C NMR (
d, 75 MHz,
CDCl3): 20.03 (3,5-CH2C6H3(CH3)2), 45.3, 49.0 (NCH2CH2N), 52.4

438
E. Üstün et al. / Journal of Molecular Structure 1123 (2016) 433e440
Table 5
4.3. Synthesis of W(CO)4L2 (1e5)
Energies (in nm), Oscillator Strength (fosc), Main Orbital Contributions, and Type of
Transition Involved in the Most Important Singlet Excitations for 3 in Hexane
Calculated with TDDFT/BP86.
All molecules were prepared by similar methods. W(CO)6
(10 mmol) and n-alkylimidazoline ligand (10.1 mmol) were mixed
with toluene (20 mL) in empty Schlenk tube which was heated and
evacuated with vacuum before use. Solution was refluxed for 1 day
under argon and the crude product was precipitated after evapo-
ration of solvent. The yellow product was crystalized with
dichloromethane/hexane and dried under vacuum.
State
l
/nm
fosc
Main transitions
Type of transitions
1
8
560.9
447.9
0.0165
0.0437
166 / 167 (95.6%)
166 / 171 (25.3%)
166 / 173 (53.4%)
166 / 174 (69.7%)
165 / 171 (73.5%)
165 / 173 (91.2%)
165 / 174 (76.4%)
164 / 173 (86.7%)
163 / 168 (74.4%)
162 / 168 (38.7%)
165 / 176 (24.6%)
W/CO / CO (MLCT/LLCT)
W/CO / imid (MLCT/LLCT)
W/CO / imid (MLCT/LLCT)
W/CO / imid (MLCT/LLCT)
W/CO / imid (MLCT/LLCT)
W/CO / imid (MLCT/LLCT)
W/CO / imid (MLCT/LLCT)
W/CO / imid (MLCT/LLCT)
imid / CO (LLCT)
9
447.7
427.0
415.9
386.1
390.3
316.7
287.6
0.0329
0.0316
0.0121
0.0198
0.0110
0.0453
0.0155
13
19
21
22
30
39
4.3.1. (Bis-(N-4-chlorobenzylimidazoline)tetracarbonyltungsten [1]
1H NMR (
d
, 300 MHz, DMSO-d6): 3.22 and 3.72 (t, 4H, J ¼ 10.2 Hz,
NCH2CH2N), 4.47 (s, 2H, NCH2C6H4Cl-4), 7.32 and 7.43 (d, J ¼ 8.4 Hz,
4H, NCH2C6H4Cl-4), 7.65 (s, 1H, NCHN). 13C NMR (
, 75 MHz, DMSO-
imid / CO (LLCT)
imid / CO (LLCT)
d
d6): 48.1 and 49.5 (NCH2CH2N), 60.1 (NCH2C6H4Cl-4), 129.1, 130.3,
132.7, 136.1 (NCH2C6H4Cl-4), 163.3 (NCHN), 192.1, 198.4, 204.8 (CO).
Anal. Calc. for C24H22N4O4Cl2W (685.20): C, 42.07; H, 3.24; N, 8.18.
Found: C, 42.11; H, 3.28; N, 8.22%. IR (cmꢂ1, ATR): 1604 (m, C-N),
1791, 1889, 1997(s, CO).
(3,5-CH2C6H3(CH3)2), 127.2, 128.8, 136.4, 137.8 (3,5-CH2C6H3(CH3)2),
157.8 (NCHN). Anal. Calc. for C12H16N2 (188.13): C, 76.55; H, 8.57; N,
14.88. Found: C, 76.53; H, 8.59; N, 14.87%.
4.3.2. (Bis-(N-4-metylbenzylimidazoline)tetracarbonyltungsten [2]
1H NMR (
d
, 300 MHz, DMSO-d6): 3.12 (t, 2H, J ¼ 5.1 Hz,
4.2.4. N-2,4,6-trimetylbenzylimidazoline [L4]
NCH2CH2N), 3.62 (t, 2H, J ¼ 5.1 Hz, NCH2CH2N), 4.34 (s, 2H,
NCH2C6H4CH3-4), 7.07e7.10 (m, 4H, NCH2C6H4 CH3-4), 2.20 (s, 4H,
1H NMR (
d, 300 MHz, CDCl3): 2.29 and 2.42 (s, 9H, 2,4,6-
CH2C6H2(CH3)3), 4.17 (s, 2H, 2,4,6-CH2C6H2(CH3)3), 6.84 (s, 2H,
2,4,6-CH2C6H2(CH3)3), 3.14 and 3.74 (t, J ¼ 9.6 Hz, 4H, NCH2CH2N),
NCH2C6H4CH3-4), 7.55 (s, 1H, NCHN). 13C NMR (
d, 75 MHz, DMSO-
d6): 47.9 and 50.0 (NCH2CH2N), 60.0 (NCH2C6H4CH3-4),128.4,129.6,
133.8, 137.3 (NCH2C6H4CH3-4), 21.1 (s, 4H, NCH2C6H4CH3-4), 163.2
(NCHN), 204.8, 214.1 (CO). Anal. Calc. for C26H28N4O4W (644.36): C,
6.97 (s,1H, NCHN). 13C NMR (
d, 75 MHz, CDCl3): 19.9 and 21.1 (2,4,6-
CH2C6H2(CH3)3),
45.7,
49.1
(NCH2CH2N),
55.2
(2,4,6-
CH2C6H2(CH3)3), 129.5, 129.8, 137.5, 137.6 (2,4,6-CH2C6H2(CH3)3),
156.8 (NCHN). Anal. Calc. for C13H18N2 (202.15): C, 77.18; H, 8.97; N,
13.85. Found: C, 77.17; H, 8.98; N, 13.85%.
48.46; H, 4.38; N, 8.69. Found: C, 48.07; H, 4.50; N, 8.35%. IR (cmꢂ1
,
ATR): 1604 (m, C-N), 1791, 1890, 1995 (s, CO).
4.3.3. (Bis-(N-3,5-dimetylbenzylimidazoline)tetracarbonyltungsten
[3]
4.2.5. N-2,3,5,6-tetrametylbenzylimidazoline [L5]
1H NMR (300 MHz, DMSO-D6)
d
(ppm) ¼ 2.23 (s, 6H, 3,5-
1H NMR (
d
, 300 MHz, CDCl3): 2.24, 2.26 (s, 12H, NCH2C6H(CH3)4-
CH2C6H3(CH3)2), 4.39 (s, 2H, 3,5-CH2C6H3(CH3)3), 6.88 (s, 2H, 3,5-
CH2C6H3(CH3)3), 6.93 (s, 1H, 3,5-CH2C6H3(CH3)3),3.22 and 3.72 (t,
J ¼ 9.9 Hz, 4H, NCH2CH2N), 7.64 (s, 1H, NCHN). 13C NMR (500 MHz,
2,3,5,6), 4.28 (s, 2H, NCH2C6H(CH3)4-2,3,5,6), 3.27 and 3.82 (t,
J ¼ 10.0 Hz, 4H, NCH2CH2N), 6.69 (s, 1H, NCH2C6H(CH3)4-2,3,5,6),
6.98 (s, 1H, NCHN). 13C NMR (
d, 75 MHz, CDCl3): 15.5, 20.5
DMSO-D6)
d
(ppm) ¼ 21.3 (3,5-CH2C6H3(CH3)2), 48.0 and 50.3
(NCH2C6H(CH3)4-2,3,5,6), 54.5 (NCH2C6H(CH3)4-2,3,5,6), 46.3, 49.2
(NCH2CH2N), 131.6, 132.0, 133.4, 134.1, (NCH2C6H(CH3)4-2,3,5,6),
156.4 (NCHN). Anal. Calc. for C13H18N2 (216.16): C, 77.73; H, 9.32; N,
12.95. Found: C, 77.71; H, 9.33; N, 12.96%.
(NCH2CH2N), 59.9 (3,5-CH2C6H3(CH3)2), 126.0, 129.5136.0, 138.2 (3,5-
CH2C6H3(CH3)2), 163.4 (NCHN), 204.9, 214.3 (CO). Anal. Calc. for
C
28H34N4O4W (672.42): C, 50.01; H, 4.80; N, 8.33%. Found: C, 50.10; H,
4.72; N, 8.25.%. IR (cmꢂ1, ATR): 1609 (m, C-N),1794,1855,1950 (s, CO).
Fig. 4. Diagram of electronic levels of 2 corresponding to gas phase, hexane, and acetonitrile.

E. Üstün et al. / Journal of Molecular Structure 1123 (2016) 433e440
439
4.3.4. (Bis-(N-2,4,6-trimetylbenzylimidazoline)
tetracarbonyltungsten [4]
References
1H NMR (300 MHz, DMSO-D6)
d
(ppm) ¼ 2.30 and 2.32 (s, 9H,
[1] D.C. Gross, P.C. Ford, Inorg. Chem. 21 (1982) 1704e1706.
[2] A.J. Lees, Coord. Chem. Rev. 177 (1998) 3.
[3] N. Metzler-Nolte, Angew. Chem. Int. Ed. 40 (2001) 1040.
[4] V. Balzani, A. Juris, M. Venturi, S. Campagna, S. Serroni, Chem. Rev. 96 (1996)
2,4,6-CH2C6H2(CH3)3), 4.29 (s, 2H, 2,4,6-CH2C6H2(CH3)3), 6.91 (s,
2H, 2,4,6-CH2C6H2(CH3)3), 3.28 and 3.78 (t, J ¼ 5.4 Hz, 4H,
NCH2CH2N), 6.91 (s, 1H, NCHN). 13C NMR (500 MHz, DMSO-D6)
759.
[5] R. Motterlini, J.E. Clark, R. Foresti, P. Sarathchandra, B.E. Mann, C.J. Green, Circ.
d
(ppm) ¼ 19.8 and 21.0 (2,4,6-CH2C6H2(CH3)3), 45.1 and 48.9
Res. 90 (2002) e17ee24.
(NCH2CH2N), 59.6 (2,4,6-CH2C6H2(CH3)3), 129.6, 129.7, 127.8, 137.2
(2,4,6-CH2C6H2(CH3)3), 161.0 (NCHN), 191.2, 204.1, 213.7 (CO). Anal.
Calc. for C30H36N4O4W (700.47): C, 51.44; H, 5.18; N, 8.00. Found: C,
51.38; H, 5.15; N, 8.07%. IR (cmꢂ1, ATR): 1598 (m, C-N), 1787, 1837,
1990 (s, CO).
€
[6] T. Sjostrand, Nature 164 (1949) 580e581.
[7] R. Tenhunen, H.S. Marver, R. Schmid, Proc. Natl. Acad. Sci.U. S. A. 61 (1968)
748e755.
[8] L.R. Goldbaum, R.G. Ramirez, K.B. Absalon, Aviat. Space Environ. Med. 46
(1975) 1289e1291.
[9] R. Motterlini, B.E. Mann, D.A. Scapens, WO 2008/003953, 20070704.
[10] B.E. Mann, Organometallics 31 (2012) 5728e5735.
[11] National Institute of Health Clinical Center, Carbon monoxide to Prevent lung
Inflammation, 14 Apr 2012 show/NCT00094406, http://www.clinicaltrials.
gov/ct2/.
[12] S.H. Crook, B.E. Mann, A.J.H.M. Meijer, H. Adams, D. Scapens, P. Sawle,
R. Motterlini, Dalton Trans. 40 (2011) 4230e4235.
[13] I.J.S. Fairlamb, A.K. Duhme-Klair, J.M. Lynam, B.E. Moulton, C.T. O’Brien,
P. Sawle, J. Hammad, R. Motterlini, Bioorg. Med. Chem. Lett. 16 (2006)
995e998.
4.3.5. (Bis-(N-2,3,5,6-tetrametylbenzylimidazoline)
tetracarbonyltungsten [5]
1H NMR (
d
, 300 MHz, DMSO-d6): 3.19 (t, 2H, J ¼ 10.5 Hz,
NCH2CH2N), 3.63 (t, 2H, J ¼ 10.5 Hz, NCH2CH2N), 4.51 (s, 2H,
NCH2C6H4(CH3)4), 6.97 (s, 1H, NCH2C6H4(CH3)4), 2.16 (s, 6H,
NCH2C6H4(CH3)4), 2.18 (s, 6H, NCH2C6H4(CH3)4), 7.34 (s, 1H, NCHN).
[14] I.J.S. Fairlamb, J.M. Lynam, B.E. Moulton, I.E. Taylor, A.K. Duhme-Klair, P. Sawle,
R. Motterlini, Dalton Trans. (2007) 3603e3605.
13C NMR (
d, 75 MHz, DMSO-d6): 45.1 and 48.2 (NCH2CH2N), 59.7
(NCH2C6H4(CH3)4), 131.8, 133.6134.0 (NCH2C6H4(CH3)4), 20.6
(NCH2C6H4(CH3)4), 15.7 (NCH2C6H4(CH3)4), 162.5 (NCHN), 204.8
(CO). Anal. Calc. for C32H40N4O4W (728.52): C, 52.76; H, 5.53; N,
7.69. Found: C, 52.80; H, 5.60; N, 7.65%. IR (cmꢂ1, ATR): 1596 (m, C-
N), 1785, 1810, 1988 (s, CO).
[15] R. Foresti, M.G. Bani-Hani, R. Motterlini, Intensive Care Med. 34 (2008)
649e658.
[16] R. Foresti, J. Hammad, J.E. Clark, T.R. Johnson, B.E. Mann, A. Friebe, C.J. Green,
R. Motterlini, Br. J. Pharmacol. 142 (2004) 453e460.
[17] L. Hewison, S.H. Crook, T.R. Johnson, B.E. Mann, H. Adams, S.E. Plant, P. Sawle,
R. Motterlini, Dalton Trans. 39 (2010) 8967e8975.
[18] X. Jiang, L. Long, H. Wang, L. Chen, X. Liu, Dalton Trans. 43 (2014) 9968e9975.
€
[19] R. Kretschmer, G. Gessner, H. Gorls, S.H. Heinemann, M. Westerhausen,
4.4. Calculation method
J. Inorg. Biochem. 105 (2011) 6e9.
[20] L. Kromer, A.C. Coelho, I. Bento, A.R. Marques, C.C. Romao, J. Organomet. Chem.
760 (2014) 89e100.
[21] P.C. Kunz, W. Huber, A. Rojas, U. Schatzschneider, B. Spingler, Eur. J. Inorg.
Chem. (2009) 5358e5366.
[22] H. Liu, P. Wang, Q. Zhao, X. Chen, B. Liu, B. Zhang, Q. Zheng, Appl. Organo-
metal. Chem. 28 (2014) 169e179.
[23] C.C. Romao, W.A. Blatter, J.D. Seixas, G.J.L. Bernardes, Chem. Soc. Rev. 41
(2012) 3571e3583.
[24] M.J. Ryan, N.L. Jernigan, H.A. Drummond, G.R. McLemore, J.M. Rimoldi,
S.R. Poreddy, R.S.V. Gadepalli, D.E. Stec, Pharmacol. Res. 54 (2006) 24e29.
[25] D. Scapens, H. Adams, T.R. Johnson, B.E. Mann, P. Sawle, R. Aqil, T. Perrior,
R. Motterlini, Dalton Trans. (2007) 4962e4973.
DFT/TDDFT calculations for full unconstrained geometry opti-
mizations and electronic transitions were carried out with ORCA
[24] version 2.8 using the exchange functional according to Becke
[15] and the correlation functional suggested by Perdew [16,17],
hereafter called BP, with the resolution-of-the-identity (RI)
approximation, a TZV [18] basis set, the tightscf and grid4 options.
The COSMO solvation model was used for analyzing the solvent ef-
fects on all calculations. Scalar relativistic effects were treated using
the Zeroth Order Regular Approximation(ZORA) formalism [19e21].
To speed up the calculations TZV/J auxiliary basis set was used [23].
[26] U. Schatzschneider, Eur. J. Inorg. Chem. (2010) 1451e1467.
[27] U. Schatzschneider, Inorganica Chim. Acta 374 (2011) 19e23.
[28] I. Charraborty, S.J. Carrington, P.K. Mascharak, Chem. Med. Chem. 9 (2014)
1266e1274.
4.5. X-ray crystallography
€
[29] G. Dordelmann, T. Meinhardt, T. Sowik, A. Krueger, U. Schatzschneider, Chem.
Commun. 48 (2012) 11528e11530.
[30] M.A. Gonzales, P.K. Mascharak, J. Inorg. Biochem. 133 (2014) 127e135.
[31] P. Govender, S. Pai, U. Schatzschneider, G.S. Smith, Inorg. Chem. 52 (2013)
5470e5478.
[32] K. Szacilowski, W. Macyk, A. Drzewiencka-Matuszek, M. Brindell, G. Stochel,
Chem. Rev. 105 (2005) 2647e2694.
Suitable crystals of 4 and 5 were selected for data collection
which were performed on Bruker X8-Apex II (for 4) and STOE IPDS
II (for 5) diffractometer equipped with a graphite-monochromatic
Mo-Ka radiation at 296 K. The structures were solved by direct
methods using SHELXS-97 [56] and refined by full-matrix least-
squares methods on F2 using SHELXL-97 [56] from within the
WINGX [57] suite of software. All non-hydrogen atoms were
refined with anisotropic parameters. The H atoms were located
from different maps and then treated as riding atoms with C-H
distances of 0.93e0.97 Å. Molecular diagrams were created using
MERCURY [58]. Details of data collection and crystal structure de-
terminations are given in Table 1. The molecular structure of mol-
ecules with the atom labeling is shown in Fig. 2.
[33] N. Macinnes, S. Duty, Br. J. Pharmacol. 143 (2004) 952e959.
[34] D.R. Crouch, Tetrahedron 65 (2009) 2387e2397.
[35] X. Guinchard, Y. Vallee, J.N. Denis, J. Org. Chem. 72 (2007) 3972e3975.
[36] C. Dardonville, I. Rozas, Med. Res. Rev. 24 (2004) 639e661.
[37] R. Tyagi, V.K. Tyagi, S.K. Pandey, J. oleo. Sci. 56 (2007) 211e222.
[38] H. Liu, D.M. Du, Adv. Synth. Catal. 351 (2009) 489e519.
[39] M. Schlenk, I. Ott, R. Gust, J. Med. Chem. 51 (2008) 7318e7322.
[40] B. Pathak, D. Majumdar, J. Leszczynski, Int. J. Quantum Chem. 109 (2009)
2263e2272.
[41] F. Neese, J. Biol. Inorg. Chem. 11 (2006) 702e711.
[42] P. Datta, A.K. Patra, C. Sinha, Polyhedron 28 (2009) 525e533.
[43] M.A. Gonzalez, S.J. Carrington, N.L. Fry, J.L. Martinez, P.K. Mascharak, Inorg.
Chem. 51 (2012) 11930e11940.
[44] G. Abbas, M. al-Rashida, A. Irfan, U.A. Rana, I. Shakir, J. Struct. Chem. 55 (2014)
30e37.
[45] A. Irfan, J. Zhang, Y. Chang, Chem. Phys. Lett. 483 (2009) 143e146.
[46] F. Neese, Coord. Chem. Rev. 253 (2009) 526e563.
[47] F. Neese, Comput. Mol. Struct. 2 (2012) 73e78.
Acknowledgements
Support of Scientific and Technological Research Council of
_
_
€
Turkey (TÜBITAK, Project No: 112T320) and Inonü University BAP
[Project Number: 2014/5] are gratefully acknowledged.
[48] E. van Lenthe, R. van Leeuwen, E.J. Baerends, J.G. Snijders, Int. J. Quantum
Chem. 57 (1996) 281.
[49] E. van Lenthe, E.J. Baerends, J.G. Snijders, J. Chem. Phys. 101 (1994) 9783.
[50] F. Weigend, R. Ahlrichs, Phys. Chem. Chem. Phys. 7 (2005) 3297.
[51] L. Goerigk, S. Grimme, Phys. Chem. Chem. Phys. 13 (2011) 6670e6688.
Appendix A. Supplementary data
_
€
[52] B. Çetinkaya, E. Çetinkaya, P.B. Hitchcook, M.F. Lappert, I. Ozdemir, J. Chem.
Soc., Dalton Trans. (1997) 1359e1362.
Supplementary data related to this article can be found at http://
dx.doi.org/10.1016/j.molstruc.2016.07.002.
[53] Imidazole form of L1: National Center for Biotechnology Information.

440
E. Üstün et al. / Journal of Molecular Structure 1123 (2016) 433e440
PubChem Compound Database; CID¼2779191, https://pubchem.ncbi.nlm.nih.
Techn. Environ. Policy 7 (2005) 42e50.
gov/compound/2779191; L2: CID¼12229395, https://pubchem.ncbi.nlm.nih.
gov/compound/12229395;L3:CID¼53320468,https://pubchem.ncbi.nlm.nih.
gov/compound/53320468;L4: CID¼583968, https://pubchem.ncbi.nlm.nih.
gov/compound/583968; L5: CID¼2991668, https://pubchem.ncbi.nlm.nih.
gov/compound/2991668.
[55] D.M. Manuta, A.J. Lees, Inorg. Chem. 22 (1983) 3825e3828.
[56] G.M. Sheldrick, Acta Cryst. A64 (2008) 112.
[57] L.J. Farrugia, J. Apply. Cryst. 32 (1999) 837.
[58] Mercury, version 3.0; CCDC, available online via ccdc.cam.ac.uk/products/
mercury.
[54] C. Jimenez-Gonzalez, A.D. Curzons, D.J.C. Constable, V.L. Cunningham, Clean.