Nitric oxide functionalized molybdenum(0) pyrazolone Schiff base complexes: Thermal and biochemical study

Article abstract of DOI:10.1039/c8ra05956j

This work describes the synthesis and characterization of three molybdenum dinitrosyl Schiff base complexes of the general formula [Mo(NO)₂(L)(OH)], where L is N-(dehydroacetic acid)-4-aminoantipyrene (dha-aapH), N-(4-acetylidene-3-methyl-1-phe

Full text of DOI:10.1039/c8ra05956j

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Nitric oxide functionalized molybdenum(0)
pyrazolone Schiff base complexes: thermal and
biochemical study†
Cite this: RSC Adv., 2018, 8, 35102
Jan Mohammad Mir * and Ram Charitra Maurya
This work describes the synthesis and characterization of three molybdenum dinitrosyl Schiff base complexes
2
of the general formula [Mo(NO) (L)(OH)], where L is N-(dehydroacetic acid)-4-aminoantipyrene (dha-aapH),
N-(4-acetylidene-3-methyl-1-phenyl-2-pyrazolin-5-one)-4-aminoantipyrine (amphp-aapH) or N-(3-
methyl-1-phenyl-4-propionylidene-2-pyrazolin-5-one)-4-aminoantipyrine (mphpp-aapH). The complexes
were formulated on the basis of spectroscopic analyses, elemental composition, magnetic susceptibility
measurements, molar conductance behaviour and determination of the respective decomposition
temperatures. A comparative experimental-theoretical approach was followed to elucidate the structure of
the complexes. Fourier transform infra-red (FT-IR) spectroscopy, thermo-gravimetry (TG) and electronic
spectral insights were mainly focused on the confirmation of the formation of the complexes. The
computational density functional theory (DFT) calculations evaluated in the study involve the molecular
specification for the use of LANL2DZ/RB3LYP formalism for metal atoms and 6-311G/RB3LYP for the
remaining non-metal atoms. The study reveals a suitable cis-octahedral geometry for the complexes. The
TG curve of one of the representative complexes was evaluated to find the respective thermodynamic and
kinetic parameters using various physical methods. The Freeman & Carroll (FC) differential method, the
Horowitz and Metzger (HM) approximation method, the Coats–Redfern method and the Broido method
were employed to present a comparative thermal analysis of the complex. The Broido method proved the
best fit to the results for the compound under question. In addition to structural and thermal analyses, the
study also deals with the in vitro antimicrobial and anticancer sensitivity of the complexes. The results
revealed potent biological properties of the representative complex containing dha-aapH. Cell toxicity tests
against COLO-205 human cancer cell line using
a
3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-
Received 12th July 2018
Accepted 28th September 2018
ꢀ1
tetrazolium bromide (MTT) assay showed an IC50 value of 53.13 mgm mL for the Schiff base and 10.51
ꢀ1
mgm L for the respective complex. Similarly the same complex proved to be an effective antimicrobial
agent against Aspergillus, Pseudomonas, E. coli and Streptococcus. The results indicated a more
pronounced activity against Pseudomonas and Streptococcus than the other two microbial species.
DOI: 10.1039/c8ra05956j
rsc.li/rsc-advances
biosynthetic pathway, MoaA and MoaC, convert GTP into cyclic
pyranopterin monophosphate (cPMP). The importance of
Introduction
4
Molybdenum (Mo) is found in the active sites of enzymes such molybdenum nitrosyl complexes, mimicking some biological
5
as nitrogenase, aldehyde oxidase, xanthine oxidase, sulte phenomena has been updated recently. Similarly, analogues of
oxidase, xanthine dehydrogenase and nitrate reductase. In this metal have been found to possess special role in catal-
6
–13
attempts to nd the antioxidant activity of various citrus fruit ysis.
extracts molybdenum has been shown to have a special role.
Nitric oxide tagged metal complexes of this class may
1
14–16
serve as efficient tools to carry out apoptosis.
Dini-
Molybdopterin has very recently been updated as one of the few trosylmolybdenum(0) complexes have also been reported to
molybdenum-containing compounds synthesized in nature. In catalyze oligomerization and polymerization reactions of
2,3
17–20
animals, guanosine triphosphate (GTP) acts as a precursor. It alkenes and alkynes and olen metathesis.
In particular,
has been found that the rst two enzymes in the molybdopterin dinitrosyl complexes of iron have been proved to be biological
21
intermediates formed during non-heme interaction with iron.
Due to the biomimetic action of molybdenum in nitrite reduc-
tion it is assumed that a NO-labeled complex of molybdenum
could act as an intermediate in the natural nitrogen xation
Coordination, Bioinorganic and Computational Chemistry Laboratory, Department of
P. G. Studies and Research in Chemistry and Pharmacy, R. D. University, Jabalpur, M.
P., India. E-mail: mirjanmohammad@gmail.com; Tel: +918492801701
22
process. Recently NO assisted Mo-mediated catalysis has
†
Electronic supplementary information (ESI) available: Refer supplemental
23
proven helpful in hydrodesulfurization.
material for Tables S1–S13 and Fig. S1–S9. See DOI: 10.1039/c8ra05956j
35102 | RSC Adv., 2018, 8, 35102–35130
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Nitric oxide expression in relation to hypertension, cancer and was purchased from BDH Chemicals, Mumbai. 3-Methyl-1-phenyl-
various other aspects has attracted chemists to tag the molecule 2-pyrozoline-5-one was supplied by Johnson Chemical Co., Bom-
with a framework for dwelling benecial effects especially bay. Acetyl chloride and propionyl chloride were procured from
24–33
releasing and scavenging properties.
In addition to experi- Thomas Baker Chemicals Ltd, Mumbai. Hydroxylamine hydro-
mental interests towards nitric oxide bound compounds, well chloride was acquired from Sisco Chem. Pvt. Ltd, Mumbai. All the
fascinated investigations have been reportedly updated with chemicals were used as supplied without any further purication
34–37
respect to theoretical science of this class of compounds.
and were of AR Grade.
There has been great ambiguity for the use of functionals and
basis sets corresponding to such type of study. The use of various
functionals and basis sets with respect to nitrosyl complexes to go
through the chemical nature of NO as neutral or charged species
Synthesis of 4-acyl-3-methyl-1-phenyl-2-pyrazolin-5-one
derivatives
38–43
has gained much importance in this regard.
4-Acyl-3-methyl-1-phenyl-2-pyrazolin-5-one derivatives were
52
The selection of ligand for complexation is an important and prepared by following the procedure reported earlier and were
careful job for synthesizing a complex. Pyrazolone based Schiff recrystallized from a methanol–water (9 : 1) mixture. The reac-
base as ONO donor ligand is the second co-ligand aer NO tar- tion scheme related to the synthesis of 4-acyl-3-methyl-1-phenyl-
geted in this study. Such types of cyclic ligands have been found 2-pyrazolin-5-one is shown in Scheme 2.
44–46
signicant in various aspects.
It has been revealed that pyr-
azole containing pharmacoactive agents play important role in
medicinal chemistry. Pyrazolone derivatives are counted among
47
Synthesis of Schiff bases
typical ICT (Intramolecular Charge Transfer) compounds having The Schiff base ligands were prepared by taking 1 : 1 ethanolic
48–50
well pronounced transport tendency.
The derivatives of this solution of dhaH (1.68 g, 10 mmol) or amphp (2.16 g, 10 mmol)
class of compounds show uorescence because of the double or mphpp (2.30 g, 10 mmol) and 4-aminoantipyrine (2.03 g, 10
51
bond hindering, which occurs due to cyclization.
mmol) and reuxing the resulting solution for 5 h (Scheme 3).
In continuation of the interest towards synthetic chemistry The reaction mixture was then poured into distilled water (250
and characterization based on various techniques, encompassing mL), when a yellow precipitate was obtained. It was ltered,
both theoretical and experimental approaches over metal nitrosyl washed several times with water and then dried in vacuo. The
complexes, a systematic study of the preparations and charac- physico-chemical analytical data of the Schiff base ligands are
terization of dinitrosyl complexes of Mo with the 4-amino- given in Table 1.
antipyrene based Schiff bases was aimed (Scheme 1). TG-base
thermodynamic/kinetic and the biochemical study of these
metallic systems are scarcely found. So in addition to formulation
Synthesis of dinitrosylmolybdenum(0) complexes
of the complexes, thermally evolved kinetic and thermodynamic
parameters, in vitro antimicrobial and anticancer aspects are
among the applied interests of the complexes reported herein.
All the complexes were prepared by following the method re-
53
ported elsewhere. The reaction scheme demonstrating the
synthesis of dinitrosyl complexes has been shown in Scheme 4.
Their elemental analysis data, color, % yield, decomposition
temperature and molar conductivities have been indicated in
Table 2. All the complexes were tested for their solubility and
Experimental section
Ammonium heptamolybdate tetrahydrate and dehydroacetic acid were found partially soluble in ethanol and methanol, insoluble
were products of Aldrich chemical Co., USA. 4-Aminoantipyrine in water and soluble in DMSO and chloroform.
Scheme 1 2-D structure of compounds used for the synthesis of the Schiff bases.
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Scheme 2 Reaction scheme for the preparation of 2-pyrazoline derivatives.
Analytical techniques applied in the study
The medium was sterilized by autoclaving at 15 lbs pressure at
ꢁ
121 C for 15 minutes. The autoclaved medium was mixed well
Carbon, hydrogen and nitrogen were determined micro
analytically on Heraeus Carlo Erba 1108 elemental analyzer. The
molybdenum content in each of the synthesized complexes was
and poured onto 100 mm Petriplates (25–30 mL per plate) while
still molten. The antimicrobial screening was performed using
54
agar-well diffusion method. Petriplates containing 20 mL
Muller Hinton medium were seeded with 24 h culture of
bacterial strains. Wells were cut and 20 mL of the given sample
(of different concentrations) were added. The plates were then
2 9 6 2
determined gravimetrically as MoO (C H ON) by the method
53
reported earlier. The identication of the coordinated nitrosyl
group in the resulting complexes was made by the chemical
53
method reported earlier.
ꢁ
incubated at 37 C for 24 hours. The antimicrobial activity was
Magnetic measurements were performed by vibrating sample
magnetometer method at RSIC, IIT Chennai. Electronic spectra
of the complexes were recorded in dimethylformamide on an
ATI Unicam UV-1-100 UV-Vis. Spectrometer in our laboratory.
Conductance measurements were made at room temperatures in
dimethylformamide using a Toshniwal conductivity bridge and
dip-type cell with a smooth platinum electrode of cell constant
assayed by measuring the diameter of the inhibition zone
formed around the well. Aspergillus, Pseudomonas, E. coli and
Streptococcus were the cultures that were used. Ooxacin as
antibacterial and uconazole as antifungal were the standard
drugs used for comparing antimicrobial properties of the model
molecular systems against the selected microbes.
Cell toxicity tests were investigated according to the method
1.02. Decomposition temperatures of the Schiff bases and the
55
developed by Mosmann. COLO-205 human cancer Cell line
was used for 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetra-
zolium bromide (MTT) assay. Cells were plated in 96 well plates
at 5000–7000 cell density per well. Cells were grown overnight in
100 mL of 10% FBS. Aer 24 hours cells were replenished with
fresh media and the test samples were added to the cells.
chelates were recorded using an electrothermal apparatus having
the capacity to record temperatures up to 360 C. The IR spectra
ꢁ
were recorded on a Perkin Elmer FTIR spectrophotometer using
KBr pellets in our laboratory. Thermogravimetry curves of the
ꢁ
complexes were recorded in the temperature range 50–1000 C at
ꢁ
ꢀ1
the heating rate of 15 C min using a Mettler Toledo Stare System
at the Regional Sophisticated Instrumentation Centre, Nagpur.
ꢀ1
Different concentrations (10, 20, 40, & 80 mg L ) of [dha-aapH]
Schiff base and its [Mo(NO) (dha-aap)OH] complex were added
2
to wells in triplicates. Cells were incubated with the solution
ꢁ
compounds for 24 hours at 37 C in 5% CO
2
. Aer 24 hours 20
Biological assays
ꢀ
1
mL of MTT dye (5 mg mL ) were added to each well and further
incubated for 3 hours. Before read-out, precipitates formed
were dissolved in 150 mL of DMSO using shaker for 15 minutes.
All the steps performed aer MTT additions were performed in
For testing the antimicrobial sensitivity, rst a suitable medium
was prepared by dissolving all components viz., yeast (2 gm),
peptone (2 gm), dextrose (1 gm) and agar–agar (2 gm) in 100 mL
distilled water and boiled to dissolve the medium completely.
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Scheme 3 Reaction schemes for the preparation of Schiff bases and associated keto–enol tautomerization.
dark. Absorbance was measured at 590 nm. Cell inhibition was
determined by the following equation:
% cell survival ¼ {(A ꢀ A )/(A ꢀ A )} ꢂ 100
t
b
c
b
%
cell inhibition ¼ 100 ꢀ cell survival
%
cell inhibition ¼ 100 ꢀ {(A
t
ꢀ A
b
)/(A
c
ꢀ A )} ꢂ 100
b
where, A ¼ absorbance value of test compound, A ¼ absor-
t
b
Computational methods
bance value of blank, A
c
¼ absorbance value of control.
Absorbance values that are lower than the control cells indicate Density functional calculations were employed to investigate
a reduction in the rate of cell proliferation. Conversely, a higher the vibrational properties and structural characteristics of the
absorbance rate indicates an increase in cell proliferation. Rarely, two representative compounds (amphp-aapH) (II) as ligand and
an increase in proliferation may be offset by cell death; evidence of the respective complex [Mo(NO) (amphp-aap)(OH)] (2). The
2
cell death may be inferred from morphological changes.
density functional theory (DFT) calculations with B3LYP/6-
Table 1 Physical and elemental analysis data of Schiff base ligands
Analysis, found/(calc.) %
Decom.
temp. ( C)
Yield
(%)
ꢁ
Compound (empirical formula) (F.W.)
C
H
N
Colour
(
(
(
dha-aapH) (I), C19
amphp-aapH) (II), (C23
mphpp-aapH) (III), (C24
H
19
N
H
3
O
4
) (353)
) (401)
) (415)
64.00, (64.58)
68.50, (68.81)
69.20, (69.38)
5.10, (5.42)
5.66, (5.77)
6.00, (6.06)
11.30, (11.89)
17.30, (17.44)
16.66, (16.86)
155
160
170
70
55
65
Light yellow
Light brown
Golden yellow
23
N
5
O
N O
5 2
2
H
25
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Scheme 4 Schematic presentation of the synthesis of dinitrosylmolybdenum(0) complexes.
311+G specied for non-metallic content and B3LYP/LANL2DZ present investigation may exist in enol form as shown in
for Mo were used, respectively. The observed bands were Scheme 3. The ring nitrogen in these ligands is found to be inert
assigned on the bases of results of normal coordinate analysis. towards coordination to molybdenum as revealed by no change
ꢀ1
All harmonic frequencies obtained were compared with real in n(C]N) (1583–1589 cm ) of the free ligands aer
values to conrm each of the equilibrium geometries calculated complexation. In fact, n(C]N) mode seems to be merged with
56
corresponding to a minimum on the potential energy surface.
n(C–O) (cyclic) mode in the respective complexes. For a carbonyl
Additionally, some of the calculated harmonic frequencies, donor, a signicant shi of n(C]O) to lower wave number takes
particularly the NO stretch frequencies, were directly compared place because of the coordination through carbonyl oxygen. The
with the experimental frequencies. The assignment of the n(C]O) for the cyclic carbonyl group at 1670, 1674 and
ꢀ
1
calculated wave numbers was aided by the animation option of 1669 cm
Gauss View 5.0 graphical interface for Gaussian programs, mphpp-aapH, respectively, is shied to lower wave numbers
in uncoordinated dha-aapH, amphp-aapH and
ꢀ
1
which gives a visual presentation of the shape of the vibrational and appears at 1575, 1581 and 1575 cm in the respective
The Cartesian representation of the theoretical force complexes. This indicates that the cyclic carbonyl oxygen is
constants are usually computed at optimized geometry by bonded to molybdenum in these complexes. The FT-IR spectra
57,58
modes.
60
ꢀ
1
assuming C point group symmetry. The energies of the highest of these ligands exhibit a strong band at 1632–1643 cm
s
occupied molecular orbital (HOMO) and lowest unoccupied assignable to n(C]N) (azomethine). In the spectra of the
molecular orbital (LUMO) levels were used for determining the respective complexes this band is shied to lower frequency,
59,100–106
existence of intramolecular charge transfer (ICT).
UV- suggesting the coordination of the azomethine nitrogen to the
visible spectral calculation conned to TD-DFT approach were
also separately computed for the two model systems.
ꢀ1
Table 3 Important FT-IR spectral bands (cm ) observed from of
Schiff base ligands
Results and discussion
Comparative theoretical and experimental infrared spectral
studies
n(C]N)
azomethine
n(C]N)
cyclic
Schiff bases
n(C]O)
n(OH)
n(C–OH)
The important infrared spectral bands of the Schiff base ligands
and their complexes along with their tentative assignments are
given in Tables 3 and 4, respectively. All the ligands used in the III
I
II
1670
1674
1669
1643
1625
1632
1583
1585
1589
3422
3419
3423
1155
1129
1162
Table 2 Physical and elemental analysis data of molybdenumdinitrosyl complexes
Analysis, found/(calc.) %
Compound (empirical formula)
Decom.
temp. (C)
Yield
(%)
Lm
(U cm mol
ꢀ
1
2
ꢀ1
(F.W.)
C
H
N
Mo
Color
)
[
(
[
(
[
(
Mo(NO)
19MoN
Mo(NO) (amphp-aap)(OH)] (2),
23MoN ) (573)
Mo(NO) (mphpp-aap)(OH)] (3),
25MoN ) (587)
2
(dha-aap)(OH)] (1),
43.00,
(43.44)
48.00,
(48.17)
49.00,
(49.07)
3.10,
(3.65)
3.98,
(4.01)
4.13,
(4.26)
12.90,
(13.33)
17.00,
(17.10)
16.50,
(16.70)
17.90,
(18.27)
16.20,
(16.49)
16.20,
(16.35)
195
70
60
57
Canary
yellow
Golden
yellow
Middle
buff
26.4
C
19
H
5 7
O
) (525)
2
170
30.7
C
23
H
7 5
O
2
200
25.3
C
24
H
7 5
O
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ꢀ1
Table 4 Important FT-IR spectral bands (cm ) observed for molybdenumdinitrosyl complexes
+
Complexes
n(NO)
n(C]O) (ketonic)
n(C]N) (azomethine)
n(C–O) (enolic)
1164
n(HO)
3428
3410
3413
n(Mo–NO)
621
1
2
3
1773
1575
1581
1575
1598
1604
1602
1
645
1775
650
1774
653
1186
656
1
1174
620
1
61
metal centre. In all the complexes, the absence of a broad question of identication of functional groups solved by infra-red
ꢀ
1
band centred at 3419–3440 cm and the presence of a medium spectroscopy based on the computed and observed wave numbers
ꢀ
1
band at 1164–1186 cm due to n(C–O) (enolic) indicate the are presented. Considering the composition of model compounds
deprotonation and coordination of enolic oxygen to the metal under study it is found that both the experimental spectra and
62
centre. The appearance of two strong bands in the region spectra generated through Gaussian calculations are in close
ꢀ
1
1
6
773–1775 and 1645–1653 cm
and a weak band at 620– approx with one another. From the graphical interpretation, Fig. 3
ꢀ1
+
56 cm may be assigned to n(NO) and n(Mo–NO), respec- and 4, it is noteworthy that the applied LANL2DZ/RB3LYP and
tively, which are in agreement with previously reported results.
The appearance of two n(NO) bands in the spectra of all the main wave numbers (cm ) computed for the ligand along with
63
RB3LYP/6-311G calculations fetch reliable frequency data. The
+
ꢀ1
synthesized complexes suggests the presence of
a
cis- the particular assignments include n(OH), 3154; n(C]O) (ketonic),
2
+
64,65
[
Mo(NO)2] moiety in the complexes.
The appearance of 1691; n(C]N) (pyrazoline ring), 1513; n(C–O) (enolic), 1123; n(C]
ꢀ
1
n(OH) mode at 3410–3430 cm in all the complexes under N) (azomethine), 1636. The dinitrosyl complex is well characterized
study is most probably due to presence of a coordinated theoretically by highlighting the main frequency ranges entailed
hydroxyl group. The experimental FT-IR spectra of Schiff base with the respective functional groups to mark the level of change
2+
ligands, I, II and III have been shown in Fig S1–S3.† The that occurred to the ligand on complexation with the [Mo(NO)
2
] .
respective FT-IR spectra of the complexes 1, 2 and 3 are given in The absence of n(OH), 3154 and the existence of n(OH, coordi-
+
Fig S4–S6,† respectively.
nated), 3738; n(C]O) (ketonic), 1596; n(NO ), 1713, 1614; n(C]N)
+
Theoretical FT-IR spectra of the representative ligand II and its (azomethine), 1585; n(C–O) (enolic), 1238; n(Mo–NO ), 630. It is
complex are given in Fig. 1 and 2, respectively. DFT scheme for the thus well established that the assumed cis geometry (C2v
calculation was same as described in geometrical optimization symmetry) with respect to the two NO ligands is comparable with
(vide supra) for both the compounds. The results are indicative of theoretical outcomes. Other remarkable changes noticed on behalf
the absence of any imaginary frequency and hence stem the arrival of the ligand coordination are also obvious.
of energy minimal surface for the optimized geometries. The main
Fig. 1 Theoretical FT-IR spectrum of ligand II.
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Fig. 2 Theoretical FT-IR spectrum of complex 2.
Experimental and theoretical electronic spectral studies
different types of bindings inside the system. The conrmation
of this fashion can be directly co-related with the respective
molecular orbital diagram designed for these type of metallic
complexes given in Scheme 5.
In order to explore the theoretical electronic spectral anal-
ysis, the TD-DFT LANL2DZ/RB3LYP and 6-311G/RB3LYP was
applied for the representative ligand II and the complex 2.
Pattern of electronic spectra of all the complexes carried out
experimentally indicate the presence of an octahedral geometry
around molybdenum that was correlated theoretically as well.
DFT processed UV-visible spectra and simplied MO diagram
Experimental-electronic spectra of the complexes (Fig. S7–S9†)
ꢀ
3
were recorded in 10
molar dimethyl DMF solutions. The
electronic spectral peaks observed in each of the complexes
along with their molar extinction coefficients are present in
Table 5. All the complexes in the present investigation display

ve transitions. The assignments of these transitions have been
given in the same table, and are based on molecular orbital
diagram applicable to hexa coordinated dinitrosyl complexes
66
reported elsewhere. These observations are in agreement with
67
the results reported in the similar type of metallic systems.
The presence of ve excitation probabilities indicates the
(imposed over the spectra) for the ligand and complex are
shown in Fig. 5 and 6, respectively. The particular alpha MO
Fig. 3 A plot of observed FT-IR frequency versus theoretical data of ligand II.
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Fig. 4 A plot of observed FT-IR frequency versus theoretical data of complex 2.
Table 5 Electronic spectral data of complexes
Molar conductance behaviour and magnetic susceptibility
insights
assignment The molar conductance measured in 10 M DMF solutions of
Peak
ꢀ
1
ꢀ1
ꢀ1
ꢀ3
Complexes
l
max
n (cm
)
(3, litre cm mol
)
ꢀ1
2
ꢀ1
these complexes are in the range 25.3–45.4 L cm mol and
1
274
36 496
33 783
30 769
28 653
22 797
34 129
30 395
28 089
25 839
22 522
33 898
31 645
28 490
27 397
21 881
3722
4312
4582
4821
1942
4110
5255
5046
3021
2722
4411
4666
5141
5054
3480
1b
1b
1b
1b
1b
1b
1b
1b
1b
1b
1b
1b
1b
1b
1b
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
/ 2a
/ 3a
2
thereby indicate the non-electrolytic nature of the complexes
2
3
3
4
96
25
49
40
1
68
under investigation. The high molar conductance values are
most probably due to strong donor capacity of dimethylforma-
mide, which may lead to the displacement of anionic ligands
/ 2b
/ 1b
/ 2a
/ 2a
/ 3a
/ 2b
/ 1b
/ 2a
/ 2a
/ 3a
2
1
1
2
1
2
3
293
68
and change of electrolyte type. The magnetic susceptibility
3
3
3
4
29
56
87
44
measurements of these complexes indicate that they are
diamagnetic and, hence, they should have ground states with
2
1
1
2
1
2
1
2
a molecular orbital conguration ( a
2
)
( a
1
)
2
and ( b )
1
2
1
69
289
following the molecular orbital diagram reported earlier. This
result is consistent with the low-spin {Mo(NO)2} electron
6
3
3
3
4
13
39
57
16
/ 2b
/ 1b
/ 2a
2
1
conguration of Mo(0) in these complexes. The diamagnetic
and non electrolytic nature of these complexes also supports the
1
+
presence of two NO groupings in all of these complexes.
Thermal analysis
levels showing the possible transitions along with the energy
required have been shown separately for the complex in Table 6.
From the data obtainable from the log le of the respective
complex conned to three possible excitations show the oscil-
lator strengths f 0.005, 0.0021 and 0.0043 for lmax 1033.79 nm
Thermal methods of analysis are those techniques in which
changes in physical and/or chemical properties of a substance
are measured as a function of temperature. Methods that deal
with changes in weight, dimensions or changes in energy come
within this explanation. Thermogravimetry technique is
entailed with the change in the weight of a substance recorded
as a function of temperature or time, DTA (differential thermal
analysis) in which the temperature difference between
a substance and reference material as a function of temperature
is recorded, DSC (differential scanning calorimetry) nds the
application by giving a record of energy difference inputs into
a substance and a reference material versus temperature func-
tion, EG (evolved gas analysis) where qualitative and quantita-
tive evaluations of volatile products formed during thermal
analysis are made and while as in TMA (thermo mechanical
analysis) in which changes in dimensions of a substance are
(1.1993 eV), lmax 683.87 nm (1.8130 eV) and lmax 574.47 nm
(2.1582 eV), respectively. The non-zero oscillator strengths
indicate that the values are acceptable to a considerable extent.
Besides the above the excitation coefficients for the particular
excitation have been used to calculate the percentage contri-
bution of electronic transition for both the model compounds.
From the data it is obvious that while 132 / 133 is the rst
preferred electronic transition, which are the respective HOMO
/
LUMO transitions of the dinitrosyl complex. Hence, the
theoretical results indicate the relevance of the level of theory
used for the electronic studies and an excellent NO-releasing
capability is thus favoured.
70
measured as a function of heat (temperature).
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Scheme 5 Molecular orbital scheme for cis-dinitrosyl complexes of C2v symmetry.
ꢁ
ꢀ1
The thermo-gravimetric analysis (TGA) for the representative heating rate of 15 C min . The rst weight loss of 2.65%
ꢁ
dinitrosylmolybdenum(0) complex, 3 was carried out within the displayed by the compound at150 C corresponds to the elimi-
temperature range from ambient temperature to 1000 C at the nation of one hydroxyl group from the complex (calcd 2.89%).
ꢁ
Fig. 5 TD-DFT UV-visible spectrum of ligand II with the overlayed MO levels.
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Fig. 6 TD-DFT UV-visible spectrum of complex 2 with overlayed MO levels.
71–73
The compound exhibits some more weight losses, which we provides the ample information.
The evaluation of kinetic
again could not correlate separately. However, the weight loss and thermodynamic parameters involved in pyrolysis of
ꢁ
observed (83.5%) at 715 C corresponds to the elimination of compounds subjected to the investigation has gained keen
one hydroxo-, two nitrosyl-, and one ligand-group(s) from the interest based on choice of method out of various ways devel-
complex (calcd 83.65%). The thermo-analytical curve of the oped so far. In the present work Freeman and Carroll (FC)
compound is Fig. 7. Therefore, the TG-curve corroborates some differential method, Horowitz and Metzger method, Coats and
of the assumptions made on the basis of infrared spectral Redfern method and Broido method have been used to deal
studies for these complexes (vide supra).
with the comparison studies of such methods to explore the
thermodynamic and kinetic aspects of the concerned thermal
behaviour of the representative complex.
TG-based thermodynamics and kinetic studies
Freeman and Carroll, using Arrhenius equation gave the
74
following equation:
Thermal analysis is the means through which information
concerning the thermal stability of the investigated complexes
is obtained. In order to decide the number and stage of
decomposition of water/hydroxyl or solvent molecules and
whether they are inside or outside the coordination sphere TGA
ꢀ
ꢁ
dW=dt
E
a
ln
¼ ln Z ꢀ
(i)
W
r
RT
where W is the total loss in weight up to time t,
Table 6 TD-DFT UV-visible data of [Mo(NO)
2
(amphp-aap)(OH)] (2) complex and the possible electronic transitions
Excitation coefficient (C)
Excited state
Excitation contribution (%)
1
Singlet A, 1.1993 eV, lmax ¼ 1033.79 nm, f ¼ 0.0005
1
1
1
30 / 133
31 / 133
32 / 133
0.21499
ꢀ0.26490
0.60770
9.24
14.03
73.86
2
Singlet A, 1.8130 eV, lmax ¼ 683.87 nm, f ¼ 0.0021
1
1
1
1
29 / 133
30 / 133
31 / 133
32 / 133
0.43924
0.22547
38.59
10.17
35.32
13.35
ꢀ0.42022
ꢀ0.25833
3
Singlet A, 2.1582 eV, lmax ¼ 574.47 nm, f ¼ 0.0043
1
1
1
29 / 133
31 / 133
32 / 133
0.49951
0.44629
0.18713
49.90
39.83
7.00
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Fig. 7 Thermo-analytical curve of complex 3.
W ¼ W ꢀ W,
where W ¼ mass loss at the completion of the reaction, W
r
¼ W
N
r
f
ꢀ
W, W is the mass loss at time ‘t’, T is the peak temperature, R
m
W
f
is the weight loss at the completion of the reaction. R is the the gas constant, q ¼ T ꢀ T and other terms same meaning as
m
gas constant and dW/dt is the weight time gradient, Z is the pre- described earlier.
ꢀ
ꢁ
WN
Wr
exponential factor and E
a
is the energy of activation.
ꢀ
ꢁ
A plot of log log
against q should gives a straight line
can be ob-
dW=dt
A plot of ln
Wr
against 1/T should be linear for
Ea
with slope
2, from which from which E
a
st
decomposition following 1 order kinetics. The slope of plot
2:303RTm
gives the value of E , while the intercept is equal to ln Z, from tained. The frequency factor Z may be calculated using equation
a
which the pre exponential factor Z can be calculated. Having as
known the value of Z, the change in entropy DS can be calcu-
E
a
Z
¼
(vi)
lated using equation
2
RT
m
f expð ꢀE=RT Þ
m
ꢂ
ꢃ
Zh
DS ¼ R ln
(ii) where f is the constant heating rate, the thermodynamic
B m
K T
parameters can be calculated as in previous case.
76
The Coats–Red fern equations are in the following form:
DH ¼ E
a
ꢀ RT
(iii)
(iv)
"
#
1
n
1
ꢀ ð1 ꢀ aÞ
M
ln
ln
¼
for ns1
(vii)
2
DG ¼ DH ꢀ TDS
ð1 ꢀ nÞT
T þ B
ꢀꢀ
lnð1 ꢀ aÞ
ꢁ
M
where, K
and T is the DTG peak temperature.
Horowitz and Metzger approximation involves the following
B
is the Boltzmann's constant, h is Planck's constant
¼
for n ¼ 1
(viii)
m
2
T
T þ B
7
5
where a represents the fraction of sample decomposed at time t,
dened by
expressions:
ꢀ
ꢁ
*
E q
a
W
N
log log
¼
ꢀ log 2:303
(v)
2
ðW
0
ꢀ W
t
Þ
W
r
2:303RTm
a ¼
(ix)
ðW
0
ꢀ W
N
Þ
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W
0
, W
t
and W
N
are the weight of sample before the degradation,
T ¼ T + bt
(xiv)
(xv)
0
ꢁ
at temperature t C and aer total conversion respectively. T is
the derivative peak temperature
dy
A
E=RT
¼ ꢀb
e
dt
dn
E
a
ln AR
M ¼ ꢀ
& B ¼
where, b ¼ dT/t, the heating rate.
R
fE
a
Eqn (xv) is integrated as:
E
a
, R, A and f are the heat of activation, the universal gas
ð
ð
1
T
dy
dn
A
ꢀ
E=RT
constant, pre-exponential factor and heating rate respectively.
The correlation coefficient ‘r’ was computed using the least
square method for different values of n (n ¼ 0.33, 0.5, 0.66 and
ðiÞ
¼ b
e
dt
(xvi)
Y
T0
ꢀ3
1
), by plotting the LHS of eqn (iii) or (iv) versus T ꢂ 10
For the rst order kinetics (n ¼ 1) in which complex degrades
The n values which gave the best t (n z 1) were chosen as usually:
the order parameter for the decomposition stage of interest.
From the intercept and linear slope of such stage, the A and E
ð
ꢂ ꢃ
1
dy
1
a
ðiiÞ
¼ ꢀln y ¼ ln
(xvii)
y
y
Y
values were determined. DS was also computed using the
relationship;
ꢀ
ꢂ
ꢃ
ꢁ
On integrating and taking log of both sides of eqn (xvii),
following equation is obtained.
Ah
kT
DS ¼ R ln
ꢀ 1
(x)
ꢀ
ꢂ ꢃꢁ
ꢂ
ꢃ
1
E
DH and DG are calculated using eqn (ii) and (iii); where k is the
Boltzmann's constant and h is the Planck's constant.
ln ln
¼
ln T þ constant
(xviii)
y
RTmþ1
Broido has developed a model and put forward a simple and
ꢀ
ꢂ ꢃꢁ
77
1
y
sensitive graphical method for the treatment of TGA data.
According to this method the weight at any time t (W ) is related
to the fraction of initial molecular weight as shown below
Thus a plot of ln ln
vs. 1/T yields straight line, whose
t
slope is directly related to E
a
:
N
W
t
ꢀ W
a
ꢀE ¼ slope ꢂ 2.303 ꢂ R
(xix)
a
Y ¼ N ¼ W
(xi)
0
0
ꢀ W
a
where E is the activation energy and R is the gas constant.
Application of this method is used to determine the kinetic
a
where W is the initial weight of the materials and W is the
weight of residue at the end of decomposition:
0
a
parameter for the complexes.
For isolated pyrolysis,
ꢀ
ꢂ ꢃꢁ
ꢂ
ꢃ
ꢀ
ꢁ
1
ꢀE
a
1
RZ
dy
ln ln
¼
þ
(xx)
n
2
¼
ꢀKy
(xii)
Y
R
T
E fT
a
m
dt
Wf ꢀ WN
where, Y ¼
and Z can be calculated from the relation
W0 ꢀ WN
If, K ¼ Aeꢀ
E/RT
ꢂ
ꢃ
ꢀ
ꢁ
(xiii)
Eaf
RTm2
1
T
RZ
Z ¼
þ
EafTm2
and if T is linear fraction of time t, therefore:
Table 7 Overall TGA evaluated thermodynamic parameters of (3)
ꢀ1
ꢀ1
ꢀ1
ꢀ1
ꢀ1
2
S. no. Methods
Decomp. step Peak temp. (K)
E
a
(kJ mol
)
DH (kJ mol
)
DS (kJ mol
)
DG (kJ mol
)
ln Z (s
)
R
st
1
2
3
4
5
Freeman Carroll
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
530
710
907
530
710
907
530
710
907
530
710
907
530
710
907
24.543
18.781
95.386
10.757
9.652
94.508
ꢀ1.6196
ꢀ0.472
0.311
0.078
0.048
0.096
8.440
20.136
12.878
87.845
6.350
ꢀ0.243
ꢀ0.260
ꢀ0.020
ꢀ0.242
ꢀ0.248
ꢀ0.334
ꢀ0.230
ꢀ0.231
0.232
ꢀ0.104
ꢀ0.324
ꢀ0.324
ꢀ0.205
ꢀ0.266
ꢀ0.227
148.923
197.478
105.475
134.610
179.829
404.987
115.875
157.635
203.194
50.793
235.895
286.424
112.550
192.710
250.02
0.798
ꢀ0.9
11.4
0.955
0.473
ꢀ9.66
2.322
2.582
2.611
17.521
ꢀ8.652
ꢀ8.455
5.399
0.942
0.804
0.966
0.976
0.981
0.976
0.967
0.900
0.957
0.982
0.961
0.982
0.967
0.911
0.970
nd
rd
st
Horowitz
nd
rd
st
3.749
ꢀ102.049
ꢀ6.026
ꢀ6.375
ꢀ7.230
ꢀ4.327
ꢀ5.855
ꢀ7.440
4.033
Coats & Redfern
Broido method
Average
nd
rd
st
nd
rd
st
nd
rd
7.002
47.575
1.100
7.218
ꢀ1.624
ꢀ1.026
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Fig. 8 Freeman Carroll plots for the three thermal decomposition steps of complex 3.
The thermogram of the representative compound provided complexes namely, activation energy (E
a
), enthalpy (DH),
ample proof in all the methods reecting the order of the entropy (DS) and free energy changes (DG) were also calculated
decomposition of the order (n) of unity. The kinetic and ther- against the methods described above. The relevant parameters
modynamic parameters of the thermal degradation of the of each involved method at each step of decomposition were
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Fig. 9 Horowitz–Metzger plots for the three thermal decomposition steps of complex 3.
evaluated and are given Tables 7 and S1–S13.† The respective or limitations over one another. Hence, the different values and
graphical presentations have also been given in Fig. 8–11. As all the comparative presentation conrm these assumptions. The
the methods employed in the study have certain advancements summary of overall results can be explained as:
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Fig. 10 Coats Redfern the three thermal decomposition steps of complex 3.
The value of change in entropy is an important factor excited form as compared to the respective reactants of pyrol-
78
describing the thermal stability of a coordination core. Low ysis.
In the later steps, numerical assignment shows
negative value of this factor is an indicative of more stable increasing trend for the values of DG, although no regular trend
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Fig. 11 Broido the three thermal decomposition steps of complex 3.
is observed in the values of either E
fact that TDS increases from one step to another, override in the loss will be lower than that of the precedent species.
values of DH is noticeable. Increasing values of DG for the structural rigidity of the remaining compound gets increased
a
or DH. It is because of the subsequent steps of a given complex shows that the rate of mass
79,80
The
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Table 8 Optimized parameters of the representative complex 2
Bond length
(angstrom)
ꢁ
ꢁ
S. no.
Atom connectivity
Atom connectivity
Bond angle ( )
Atom connectivity
Dihedral angle ( )
1
2
3
4
5
6
7
8
9
N(1)–N(2)
N(1)–C(5)
N(1)–C(7)
N(2)–C(3)
C(3)–C(4)
C(3)–C(13)
C(4)–C(5)
C(4)–C(14)
C(5)–O(6)
O(6)–Mo(36)
C(7)–C(8)
1.4169
1.3824
1.4305
1.3357
1.4550
1.5063
1.4418
1.4302
1.3079
2.0825
1.4131
1.4132
1.4060
1.0818
1.4070
1.0875
1.4089
1.0872
1.4037
1.0877
1.0829
1.0972
1.0942
1.0972
1.5222
1.3441
1.0961
1.0927
2.7989
1.0919
1.4486
1.3905
1.4094
1.2861
1.3807
2.2273
1.4288
1.4344
1.4790
1.4083
1.0909
1.0991
1.0925
1.5003
1.0964
1.0919
1.0983
1.4085
1.4101
1.4055
1.0845
1.4084
1.0866
1.4087
1.0867
1.4054
1.0869
1.0867
2.2596
1.2258
1.8718
1.2199
N(2)–N(1)–C(5)
N(2)–N(1)–C(7)
C(5)–N(1)–C(7)
N(1)–N(2)–C(3)
111.1227
118.5364
130.3396
106.2830
111.4977
117.1144
131.3541
104.3830
129.3448
126.2483
106.7018
122.5241
130.7492
123.8363
121.4570
118.4472
120.0955
119.3591
119.8808
120.7601
120.9753
118.9494
120.0753
119.1756
120.4110
120.4133
120.6755
120.0669
119.2576
119.7189
119.0313
121.2498
112.0380
108.2810
112.1750
108.3076
107.8519
108.0491
118.1067
121.0630
120.7153
112.9048
108.8040
83.6577
110.9281
107.4605
56.0457
163.0053
107.9014
76.8812
107.0607
116.4175
136.2783
125.9228
107.7631
126.2938
108.5794
108.6248
127.2127
122.6405
116.7843
107.0216
C(5)–N(1)–N(2)–C(3)
C(7)–N(1)–N(2)–C(3)
N(2)–N(1)–C(5)–C(4)
N(2)–N(1)–C(5)–O(6)
C(7)–N(1)–C(5)–C(4)
C(7)–N(1)–C(5)–O(6)
N(2)–N(1)–C(7)–8(C)
N(2)–N(1)–C(7)–C(12)
C(5)–N(1)–C(7)–C(8)
C(5)–N(1)–C(7)–C(12)
N(1)–N(2)–C(3)–C(4)
ꢀ0.6383
178.9895
ꢀ0.0469
178.3201
ꢀ179.6179
ꢀ1.2509
178.9105
ꢀ0.9442
ꢀ1.5450
178.6002
1.0728
179.1989
ꢀ1.0998
177.1843
ꢀ178.8776
ꢀ0.5936
ꢀ123.0107
ꢀ3.6297
115.5143
54.6664
N(2)–C(3)–C(4)
N(2)C–(3)–C(13)
C(4)–C(3)–C(13)
C(3)–C(4)–C(5)
C(3)–C(4)–C(14)
C(5)–C(4)–C(14)
N(1)–C(5)–C(4)
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
C(7)–C(12)
C(8)–C(9)
N(1)–C(5)–O(6)
C(4)–C(5)–O(6)
N(1)–N(2)–C(3)–C(13)
N(2)-C(3)–C(4)–C(5)
C(8)–H(37)
C(9)C–(10)
C(9)–H(38)
C(10)–C(11)
C(10)–H(39)
C(11)–C(12)
C(11)–H(40)
C(12)–H(41)
C(13)–H(42)
C(13)–H(43)
C(13)–H(44)
C(14)–C(15)
C(14)–N(30)
C(15)–H(45)
C(15)–H(46)
C(15)–H(51)
C(15)–H(59)
C(16)–C(17)
C(16)–C(22)
C(16)–N(30)
C(17)–O(18)
C(17)–C(26)
O(18)–Mo(36)
N(19)–N(20)
N(19)–(24)
N(20)–C(21)
N(20)–C(22)
C(21)–H(47)
C(21)–H(48)
C(21)–H(49)
C(22)–C(23)
C(23)–H(50)
C(23)–H(51)
C(23)–H(52)
C(24)–C(25)
C(24)–C(29)
C(25)–C(26)
C(25)–H(53)
C(26)–C(27)
C(26)–H(54)
C(27)–C(28)
C(27)–H(55)
C(28)–C(29)
C(28)–H(56)
C(29)–H(57)
N(30)–Mo(36)
N(31)–O(32)
N(31)–Mo(36)
N(33)–O(34)
C(5)–O(6)–Mo(36)
N(1)–C(7)–C(8)
N(1)–C(7)–C(12)
C(8)–C(7)–C(12)
C(7)–C(8)–C(9)
N(2)–C(3)–C(4)–C(14)
C(13)–C(3)–C(4)–C(5)
C(13)–C(3)–C(4)–C(14)
N(2)–C(3)–C(13)–H(42)
N(2)–C(3)–C(13)–H(43)
N(2)–C(3)–C(13)–H(44)
C(4)–C(3)–C(13)–H(42)
C(4)–C(3)–C(13)–H(43)
C(4)–C(3)–C(13)–H(44)
C(3)–C(4)–C(5)–N(1)
C(7)–C(8)–H(37)
C(9)–C(8)–H(37)
C(8)–C(9)–C(10)
C(8)–C(9)–H(38)
C(10)–C(9)–H(38)
C(9)–C(10)–C(11)
C(9)–C(10)–H(39)
C(11)–C(10)–H(39)
C(10)–C(11)–C(12)
C(10)–C(11)–H(40)
(12)–C(11)–H(40)
C(7)–C(12)–C(11)
C(7)–C(12)–H(41)
C(11)–C(12)–H(41)
C(3)–C(13)–H(42)
C(3)–C(13)–H(43)
C(3)–C(13)–H(44)
H(42)–C(13)–H(43)
H(42)–C(13)–H(44)
H(43)–C(13)–H(44)
C(4)–C(14)–C(15)
C(4)–C(14)–N(30)
C(15)–C(14)–N(30)
C(14)–C(15)–H(45)
C(14)–C(15)–H(46)
C(14)–C(15)–H(51)
C(14)–C(15)–H(59)
H(45)–C(15)–H(46)
H(45)–C(15)–H(51)
H(46)–C(15)–H(51)
H(46)–C(15)–H(59)
H(51)–C(15)–H(59)
C(17)–C(16)–C(22)
C(17)–C(16)–N(30)
C(22)–C(16)–N(30)
C(16)–C(17)–O(18)
C(16)–C(17)–N(19)
O(18)–C(17)–N(19)
C(17)–O(18)–Mo(36)
C(17)–N(19)–N(20)
C(17)–N(19)–C(24)
N(20)–N(19)–C(24)
N(19)–N(20)–C(21)
N(19)–N(20)–C(22)
174.0474
ꢀ66.8086
0.6517
ꢀ177.5308
ꢀ177.7028
4.1147
C(3)–C(4)–C(5)–O(6)
C(14)–C(4)–C(5)–N(1)
C(14)–C(4)–C(5)–O(6)
C(3)–C(4)–C(14)–C(15)
C(3)–C(4)–C(14)–N(30)
C(5)–C(4)–C(14)–C(15)
C(5)–C(4)–C(14)–N(30)
N(1)–C(5)–O(6)–Mo(36)
C(4)–C(5)–O(6)–Mo(36)
C(5)–O(6)–Mo(36)–O(18)
C(5)–O(6)–Mo(36)–N(30)
C(5)–O(6)–Mo(36)–N(31)
C(5)–O(6)–Mo(36)–N(33)
C(5)–O(6)–Mo(36)–O(35)
N(1)–C(7)–C(8)–C(9)
N(1)–C(7)–C(8)–H(37)
C(12)–C(7)–C(8)–C(9)
C(12)–C(7)–C(8)–H(37)
N(1)–C(7)–C(12)–C(11)
N(1)–C(7)–C(12)–H(41)
C(8)–C(7)–C(12)–C(11)
C(8)–C(7)–C(12)–H(41)
C(7)–C(8)–C(9)–C(10)
C(7)–C(8)–C(9)–H(38)
H(37)–C(8)–C(9)–C(10)
H(37)–C(8)–C(9)–H(38)
C(8)–C(9)–C(10)–C(11)
C(8)–C(9)–C(10)–H(39)
H(38)–C(9)–C(10)–C(11)
H(38)–C(9)–C(10)–H(39)
C(9)–C(10)–C(11)–C(12)
C(9)–C(10)–C(11)–H(40)
H(39)–C(10)–C(11)–C(12)
H(39)–C(10)–C(11)–H(40)
C(10)–C(11)–C(12)–C(7)
C(10)–C(11)–C(12)–H(41)
H(40)–C(11)–C(12)–C(7)
H(40)–C(11)–C(12)–H(41)
C(4)–C(14)–C(15)–H(45)
14.6302
ꢀ169.2415
ꢀ167.431
8.6973
ꢀ169.9575
7.9777
ꢀ5.5974
ꢀ19.2260
ꢀ109.8906
158.1447
60.4738
ꢀ179.9293
0.1013
ꢀ0.0769
179.9537
179.8937
ꢀ0.0733
0.0369
ꢀ179.9301
0.0714
ꢀ179.9715
ꢀ179.9595
ꢀ0.0025
ꢀ0.0251
179.9615
ꢀ179.9817
0.0050
ꢀ0.0160
ꢀ180.0051
179.9973
0.0083
0.0099
179.9762
179.9991
ꢀ0.0347
ꢀ75.6720
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Table 8 (Contd.)
Bond length
(angstrom)
ꢁ
ꢁ
S. no.
Atom connectivity
Atom connectivity
Bond angle ( )
Atom connectivity
Dihedral angle ( )
6
6
6
6
6
6
6
7
7
7
7
7
7
7
7
7
7
8
8
8
8
8
8
8
8
8
8
9
9
9
9
9
9
9
9
9
9
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
N(33)–Mo(36)
O(35)–Mo(36)
O(35)–H(58)
1.8258
1.9982
0.9770
C(21)–N(20)–C(22)
N(20)–C(21)–H(47)
N(20)–C(21)–H(48)
N(20)–C(21)–H(49)
H(47)–C(21)–H(48)
H(47)–C(21)–H(49)
H(48)–C(21)–H(49)
C(16)–C(22)–N(20)
C(16)–C(22)–C(23)
N(20)–C(22)–C(23)
C(22)–C(23)–H(50)
C(22)–C(23)–H(51)
C(22)–C(23)–H(52)
H(50)–C(23)–H(51)
H(50)–C(23)–H(52)
H(51)–C(23)–H(52)
N(19)–C(24)–C(25)
N(19)–C(24)–C(29)
C(25)–C(24)–C(29)
C(24)–C(25)–C(26)
C(24)–C(25)–H(53)
C(26)–C(25)–H(53)
C(25)–C(26), (27)
C(25)–C(26)–H(54)
C(27)–C(26)–H(54)
C(26)–C(27)–C(28)
C(26)–C(27)–H(55)
C(28)–C(27)–H(55)
C(27)–C(28)–C(29)
C(27)–C(28)–H(56)
C(29)-C(28)–H(56)
C(24)–C(29)–C(28)
C(24)–C(29)–H(57)
C(28)–C(29)–H(57)
C(14)–N(30)–C(16)
C(14)–N(30)–Mo(36)
C(16)–N(30)–Mo(36)
Mo(36)–O(35)–H(58)
O(6)–Mo(36)–O(18)
O(6)–Mo(36)–N(30)
O(6)–Mo(36)–N(31)
O(6)–Mo(36)–N(33)
O(6)–Mo(36)–O(35)
O(18)–Mo(36)–N(30)
O(18)–Mo(36)–N(31)
O(18)–Mo(36)–N(33)
O(18)–Mo(36)–O(35)
N(30)–Mo(36)–N(31)
N(30)–Mo(36)–N(33)
N(30)–Mo(36)–O(35)
N(31)–Mo(36)–N(33)
N(31)–Mo(36)–O(35)
N(33)–Mo(36)–O(35)
C(15)–H–(51)–C(23)
122.5219
109.4412
111.7617
108.5134
109.0236
108.2197
109.8128
109.0522
130.3368
120.4189
111.3545
109.6027
112.3257
107.3773
107.8412
108.1619
118.8474
120.2177
120.9133
119.1193
119.9464
120.9216
120.5469
119.3406
120.1122
119.7778
120.1215
120.0984
120.2899
120.1302
119.5706
119.3367
119.9739
120.6705
125.0868
123.2236
107.9961
123.5183
165.0647
86.9854
C(4)–C(14)–C(15)–H(46)
C(4)–C(14)–C(15)–H(51)
C(4)–C(14)–C(15)–H(59)
N(30)–C(14)–C(15)–H(45)
N(30)–C(14)–C(15)–H(46)
N(30)–C(14)–C(15)–H(51)
N(30)–C(14)–C(15)–H(59)
C(4)–C(14)–N(30)–C(16)
C(4)–C(14)–N(30)–Mo(36)
C(15)–C(14)–N(30)–C(16)
C(15)–C(14)–N(30)–Mo(36)
C(14)–C(15)–H(51)–C(23)
H(45)–C(15)–H(51)–C(23)
H(46)–C(15)–H(51)–C(23)
H(59)–C(15)–H(51)–C(23)
C(22)–C(16)–C(17)–O(18)
C(22)–C(16)–C(17)–N(19)
N(30)–C(16)–C(17)–O(18)
N(30)–C(16)–C(17)–N(19)
C(17)–C(16)–C(22)–N(20)
C(17)–C(16)–C(22)–C(23)
N(30)–C(16)–C(22)–N(20)
N(30)–C(16)–C(22)–C(23)
C(17)–C(16)–N(30)–C(14)
C(17)–C(16)–N(30)–Mo(36)
C(22)–C(16)–N(30)–C(14)
C(22)–C(16)–N(30)–Mo(36)
C(16)–C(17)–O(18)–Mo(36)
N(19)–C(17)–O(18)–Mo(36)
C(16)–C(17)–N(19)–N(20)
C(16)–C(17)–N(19)–C(24)
O(18)–C(17)–N(19)–N(20)
O(18)–C(17)–N(19)–C(24)
C(17)–O(18)–Mo(36)–O(6)
C(17)–O(18)–Mo(36)–N(30)
C(17)–O(18)–Mo(36)–N(31)
C(17)–O(18)–Mo(36)–N(33)
C(17)–O(18)–Mo(36)–O(35)
C(17)–N(19)–N(20)–C(21)
C(17)–N(19)–N(20)–C(22)
C(24)–N(19)–N(20)–C(21)
C(24)–N(19)–N(20)–C(22)
C(17)–N(19)–C(24)–C(25)
C(17)–N(19)–C(24)–C(29)
N(20)–N(19)–C(24)–C(25)
N(20)–N(19)–C(24)–C(29)
N(19)–N(20)–C(21)–H(47)
N(19)–N(20)–C(21)–H(48)
N(19)–N(20)–C(21)–H(49)
C(22)–N(20)–C(21)–H(47)
C(22)–N(20)–C(21)–H(48)
C(22)–N(20)–C(21)–H(49)
N(19)–N(20)–C(22)–C(16)
N(19)–N(20)–C(22), (23)
C(21)–N(20)–C(22)–C(16)
C(21)–N(20)–C(22)–C(23)
C(16)–C(22)–C(23)–H(50)
C(16)–C(22)–C(23)–H(51)
C(16)–C(22)–C(23)–H(52)
N(20)–C(22)–C(23)–H(50)
N(20)–C(22)–C(23)–H(51)
N(20)–C(22)–C(23)–H(52)
43.5349
ꢀ124.5978
162.0808
108.1856
ꢀ132.6075
59.2598
ꢀ14.0616
174.9123
ꢀ29.3835
ꢀ9.0602
146.644
ꢀ114.8123
122.0302
106.9489
ꢀ1.5508
ꢀ173.3069
5.1364
1.9510
ꢀ179.6057
ꢀ7.1042
167.7644
179.0453
ꢀ6.0861
145.8735
ꢀ12.9098
ꢀ40.6926
160.5240
10.4761
ꢀ167.6845
ꢀ1.2310
164.8452
177.2049
ꢀ16.7189
ꢀ26.4786
ꢀ12.5851
78.8398
5
6
7
8
9
169.7075
ꢀ92.9858
ꢀ144.7408
ꢀ3.0788
48.4139
00
01
02
03
04
05
06
07
08
09
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
95.9567
98.1548
88.7987
78.5034
87.8804
96.1922
85.1668
90.9729
174.2325
79.6522
91.0906
169.2742
97.7632
102.0338
ꢀ169.9242
50.2825
ꢀ128.0426
ꢀ145.4292
36.2457
ꢀ47.8118
73.0582
ꢀ165.7069
176.8915
ꢀ62.2385
58.9964
6.3785
ꢀ169.0870
145.3274
ꢀ30.1381
ꢀ128.0683
ꢀ9.4058
110.8553
46.3056
164.9681
ꢀ74.7707
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Table 8 (Contd.)
Bond length
(angstrom)
ꢁ
ꢁ
S. no.
Atom connectivity
Atom connectivity
Bond angle ( )
Atom connectivity
Dihedral angle ( )
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
C(22)–C(23)–H(51)–C(15)
H(50)–C(23)–H(51)–C(15)
H(52)–C(23)–H(51)–C(15)
N(19)–C(24)–C(25)–C(26)
N(19)–C(24)–C(25)–H(53)
C(29)–C(24)–C(25)–C(26)
C(29)–C(24)–C(25)–H(53)
N(19)–C(24)–C(29)–C(28)
N(19)–C(24)–C(29)–H(57)
C(25)–C(24)–C(29)–C(28)
C(25)–C(24)–C(29)–H(57)
C(24)–C(25)–C(26)–C(27)
C(24)–C(25)–C(26)–H(54)
H(53)–C(25)–C(26)–C(27)
H(53)–C(25)–C(26)–H(54)
C(25)–C(26)–C(27)–C(28)
C(25)–C(26)–C(27)–H(55)
H(54)–C(26)–C(27)–C(28)
H(54)–C(26)–C(27)–H(55)
C(26)–C(27)–C(28)–C(29)
C(26)–C(27)–C(28)–H(56)
H(55)–C(27)–C(28)–C(29)
H(55)–C(27)–C(28)–H(56)
C(27)–C(28)–C(29)–C(24)
C(27)–C(28)–C(29)–H(57)
H(56)–C(28)–C(29)–C(24)
H(56)–C(28)–C(29)–H(57)
C(14)–N(30)–Mo(36)–O(6)
C(14)–N(30)–Mo(36)–O(18)
C(14)–N(30)–Mo(36)–N(31)
C(14)–N(30)–Mo(36)–N(33)
C(14)–N(30)–Mo(36)–O(35)
C(16)–N(30)–Mo(36)–O(6)
C(16)–N(30)–Mo(36)–O(18)
C(16)–N(30)–Mo(36)–N(31)
C(16)–N(30)–Mo(36)–N(33)
C(16)–N(30)–Mo(36)–O(35)
H(58)–O(35)–Mo(36)–O(6)
H(58)–O(35)–Mo(36)–O(18)
H(58)–O(35)–Mo(36)–N(30)
H(58)–O(35)–Mo(36)–(31)
H(58)–O(35)–Mo(36)–N(33)
60.2175
ꢀ178.6863
ꢀ62.5489
ꢀ178.6483
0.0665
ꢀ0.3353
178.3795
179.5510
1.1207
1.2610
ꢀ177.1693
ꢀ0.7502
179.4331
ꢀ179.4521
0.7313
0.8981
ꢀ179.6406
ꢀ179.2867
0.1747
0.0439
178.9355
ꢀ179.4175
ꢀ0.5259
ꢀ1.1085
177.3106
179.9937
ꢀ1.5872
30.6846
ꢀ145.7624
126.5990
ꢀ122.4507
ꢀ58.6436
ꢀ170.0474
13.5055
ꢀ74.133
36.8173
100.6244
98.8864
ꢀ94.7888
ꢀ173.9592
ꢀ144.5603
0.8193
aer the expulsion of one or more species, as compared with the content. The various bond lengths, bond angles and dihedral
precedent complex. From the values of DG we may conrm the angles generated from the equilibrium structure of one of the
coordination core where there attains increase in its value. It is representative complex 2, using Gaussian 09 soware are given
known that the order has no intrinsic meaning, but is rather in the Table 8. The computed bond lengths, such as, Mo(36)–
81
a mathematical smoothing parameter. In the present case the O(6), Mo(36)–O(18), Mo(36)–O(35), Mo(36)–N(30), Mo(36)–N(31)
reaction order of all the decomposition stages of all the and Mo(36)–N(33) in the present complex are 2.08248, 2.22730,
˚
methods are found to nearly equal to one.
1.99819, 2.25960, 1.87183 and 1.82578 A, respectively. The
signicant computed bond angles in the complex, such as,
Mo(36)–O(35)–H(58), O(6)–Mo(36)–O(18), O(6)–Mo(36)–N(30),
O(6)–Mo(36)–N(31), O(6)–Mo(36)–N(33), O(6)–Mo(36)–O(35),
DFT based geometry optimization
The optimized geometry of both the model compounds fur- O(18)–Mo(36)–N(30), O(18)–Mo(36)–N(31), O(18)–Mo(36)–N(33),
ꢀ1
nished the zero point energy 280.99 kcal mol for the repre- O(18)–Mo(36)–O(35), N(30)–Mo(36)–N(31), N(30)–Mo(36)–N(33),
ꢀ
1
sentative complex, whereas 267.22 kcal mol was the result N(30)–Mo(36)–O(35), N(31)–Mo(36)–N(33), N(31)–Mo(36)–O(35),
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
obtained for the respective ligand. It directly reects that the N(33)–Mo(36)–O(35) 123.52 , 165.10 , 86.98 , 95.96 , 98.15 ,
ꢁ
ꢁ
ꢁ
ꢁ
stability pronounces more in complex because of lower energy 88.80 , 78.50 , 87.88 , 96.19 , 85.17 , 90.97 , 174.23 , 79.65 ,
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ꢁ ꢁ ꢁ
1.09 , 169.27 , 97.76 respectively, suggest the octahedral [LUMO+1] and third lowest unoccupied MOs, [LUMO+1] were
9
structure of the present as well as the other complexes under worked out for ligand II and its respective dinitrosyl complex 2
investigation. The optimized structure of the representative as shown in Fig. 13 and 14, respectively. The computed energies
complex is shown in Fig. 12. One of the interesting facts about of these six molecular orbitals observed for the ligand II are
the calculated bond angles is the prediction of linear nitrosyl ꢀ6.3434 eV, ꢀ5.9970 eV, ꢀ5.7678 eV, ꢀ1.2928 eV, ꢀ1.1342 eV
group for the model complex by considering the bond angles and ꢀ0.8863 eV respectively, and the energy gaps (DE) between
ꢁ
like Mo(36)–N(33)–O(34), 176.807 and Mo(36)–N(31)–O(32), [HOMO–LUMO], [HOMOꢀ1–LUMO+1], [HOMOꢀ2–LUMO+2]
ꢁ
1
72.092 .
for the ligand are 4.475 eV, 4.8628 eV and 5.4571 eV, respec-
tively. Similarly four (MOs), viz., [HOMOꢀ2], [HOMOꢀ1],
[HOMO], [LUMO], [LUMO+1] and [LUMO+2] are worked out for
DFT based molecular orbital analysis
the complex 2 and the observed energies in the same order are
as ꢀ5.7847 eV, ꢀ5.7104 eV, ꢀ5.2048 eV, ꢀ2.7100 eV, ꢀ1.8741 eV
and 0.6602 eV, while the energy gap between [HOMO–LUMO],
Highest occupied molecular orbital (HOMO) and lowest unoc-
cupied molecular orbital (LUMO) are also collectively called as
frontier orbitals because these are very important parameters
[
HOMOꢀ1–LUMO+1] and [HOMOꢀ1–LUMO+1] are: 2.4948 eV,
82
3.8363 eV and 5.1245 eV respectively. The electronic llings of
MO's in both ligand and its complex verify their diamagnetic
behaviour.
for describing chemical behaviour. The HOMO is referred as
primarily electron donor and the LUMO on the other hand is
electron acceptor, and the gap between HOMO and LUMO
83
The energy of the frontier orbitals for molecules in term of
ionization energy (IE) and electron affinity (IA) of the (amphp-
aapH) and its complex are fetchable according to Koopmans's
characterizes the molecular chemical stability. Six important
molecular orbitals (MOs) namely, third highest [HOMOꢀ2],
second highest [HOMOꢀ1], and highest occupied MOs
84
theorem. Similarly, the absolute electro negativity (cabs) and
[HOMO], the lowest [LUMO], second lowest unoccupied MOs
Fig. 12 2D and 3D optimized structure of complex 2.
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Fig. 13 HOMO–LOMO structure with energy level diagram of ligand II.
85
absolute hardness (h) are related to IA and EA. Hard molecules absolute hardness (h), electrophilicity index (u) and global
characterize a large HOMO–LUMO gap, and so molecules soness (S) of the two selected model compounds calculated so
85
show narrow gap. The absolute electro negativity (cabs), far are represented in Table 9.
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Fig. 14 HOMO–LOMO structure with energy level diagram of complex 2.
Antimicrobial study
and Aspergillus, by agar well diffusion method. The inhibition
zones in millimeters of shown by the model complex are given
in Table 10. IC50 values of the complex indicate that it has good
degree of antimicrobial properties. IC50 values of 128 against
The antimicrobial activity of the representative complex 1 was
tested against some Gram negative, Gram positive and fungal
strains of microbes including Pseudomonas, E. coli, Streptococcus
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Table 9 Absolute electronegativity (cabs), absolute hardness (h), electrophilicity index (u), global softness (S) of (amphp-aapH) (II) and complex
Mo(NO) (amphp-aap)(OH)] (2)
[
2
Compounds
c
abs (eV)
h (eV)
u (debye per eV)
S (eV)
m (debye)
(
amphp-aapH)
3.5303
3.9574
2.2375
1.2474
14.0057
72.9611
0.4469
0.8017
7.9168
13.4916
[
Mo(NO) (amphp-aap)(OH)]
2
Streptococcus, 134 against Pseudomonas, 288 against E. Coli and It is noteworthy to state here that the inhibition zones were
19 against Aspergillus have been found. The Petriplates dis- shown to have remarkably increased on increasing the
2
playing the inhibition zones have been shown in Fig. 15. The concentration of the compounds under investigation.
increase in the biological activity of the metal complexes can be
explained on the basis of chelation theory and overtones Antiproliferative effects on colo-205 human cancer cells
86–88
concept.
According to chelation theory, the delocalization of
Expression of nitric oxide in cancerous cells triggered the
possible applications of nitrosyl complexes in treating cancer.
In the present investigation the selected cancer cell line is
related with the dreadful colon cancer which is the second
most common cause of cancer-related death aer lung cancer.
Literature survey shows that risk parameters conned to
nutrition and genes result in additive effects of the tumor. On
other hand the co-relation of NO (nitric oxide) with apoptosis
induction upon COLO 205 represents important asset of the
targeted theme. Antiproliferative tests were carried out sepa-
p electrons over the whole chelate ring enhances the lip-
ophilicity and the polarity of the metal atom is reduced due to
the overlap of the ligand orbital and partial share of positive
89–91
charge of metal atom with ligands.
So, increase in lipophilic
character results in an increase in permeability through the
lipid layers of cell membrane and the metal binding sites on
enzymes of microorganism are blocked. Overtone's concept is
based on cell permeability, wherein the lipid membrane that
surrounds the cell favours the passage of only the lipophilic
materials due to which lipo-solubility is an important factor,
93
rately for ligand I and its respective complex using MTT assay.
92
which controls the antimicrobial action. It is observed that
different compounds show antimicrobial activity of low varia-
tion range against bacterial and fungal species. This difference
depends either on the impermeability of the cells of the
microorganism which, in case of Gram positive is single layered
and in the case of Gram negative is multilayered structure or
differences in ribosomes of microbial cells. It can possibly
be concluded that the chelation increased the activity of
these complexes. The present results show that dinitrosyl
molybdenum Schiff base complexes possess better cytotoxicity
than the corresponding Schiff base ligand against the same
microbes. Although the complexes are active, they did not reach
the effectiveness of the conventional bactericide ooxacin and
fungicide uconazole. However, it may be mentioned that the
activity index (A.I.) given against each concentration, Fig. 16,
showing excellent biological effects in case of the complex:
Doxorubicin with 2% dimethylsulfoxide (DMSO) was used as
standard control. Fig. 17 shows the exhibited dose-dependent
antiproliferative activity against colo-205 human cancer cells
of the target compounds and signicantly reduced the growth
rate of colo-205 cancer cells. It has been shown that the dini-
trosyl complex of molybdenum bears better cytotoxic activity as
compared to the corresponding Schiff base. The related data of
cell inhibition and cell survival have been given in Table 11.
Inhibition zone of sample ðmmÞ
A:I: ¼
Inhibition zone of standard ðmmÞ
2 2
Table 10 Antimicrobial screening of [Mo(NO) (dha-aap)(H O)]
a
a
ZI and AI
ZI and AI at ZI and AI at
ꢀ
1
ꢀ1
at 100 mg
mL con.
75 mg mL
50 mg mL
ꢀ1
con.
con.
1
mg
ꢀ
1
Strain
ZI AI
ZI
AI
ZI
AI
mL (std.)
Streptococcus 42.75 0.91 39.0 0.83 31.25 0.67 46.75(Ooxacin)
Pseudomonas 41.50 0.92 37.0 0.82 29.75 0.66 45.25(Ooxacin)
E. coli
24.50 0.74 21.50 0.65 17.75 0.53 33.25(Ooxacin)
Aspergillus
26.50 0.85 22.50 0.72 16.75 0.54 31.0(Fluconazole)
a
Z. I. is the zone of inhibition and A. I. is the activity index at the Fig. 15 Petri-plates showing zones of antimicrobial actions at
different concentrations by the complex 1.
particular concentration of the sample.
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populations analysis are the tools which help to build up
94,95
insights regards the potential characteristics of a molecule.
Molecular charge analysis and electron density plots as
biological speculative tools
Drug/medicinal properties depicted by compounds are mainly
focused with regard to lipophilicity, size and charge analysis.
Depending on the electronic charge on the chelating atoms one
may depict the bonding capability of a molecule. In order to
quantify and compare specic interactions pertaining to the
pictorial presentation of orbitals, numerical values serve as the
keys to intensify their value. In case of donation versus back
donation in transition metals and s/p bonding it may prove
helpful by assigning charges to the constituent atoms of a mole-
cule. Pictorial presentation of orbitals are instant informative,
however for the purpose to quantify and compare specic inter-
Fig. 16 Graphical presentation of inhibition zones against the partic-
ꢀ1
ꢀ1
ular strains at different concentrations (a ¼ 50 mg mL , b ¼ 75 mg mL
ꢀ1
and c ¼100 mg mL ) shown by complex 1.
actions numerical values are the keys to intensify the informative
From IC50 values 53.13 in the Schiff base and 10.51 in its
complex, it is established that latter bears more anticancer
potentiality. Both the biological assays are found supportive in
the assumption that the complexes bears better biological
relevance as compared to the free ligands. The reasons lying
behind this factual observation can be explained on the basis of
theoretical results also. Electron density plots and charge
96–99
representation.
For instance, donation versus back donation
in transition metal complexes, single, double and triple bonding
in organic compounds. Assigning charges to atoms is very useful
idea for performing a rough idea of charge distribution in
a molecule. The total electron density is expanded in terms of
molecular orbitals and then each orbital can be extrapolated in
terms of a set of atomic orbitals (the basis set).
Fig. 17 Dose dependant anti-proliferative data of the model compounds I and 1.
Table 11 Antiproliferative data of (dha-aapH) ligand and its dinitrosyl complex
Control
absorbance
Concentration
mg mL
% cell
survival
% cell
death
ꢀ
1
Absorbance
(
dha-aapH)
1.21
10
0.118
0.284
0.311
0.536
0.188
0.243
0.360
0.421
90.24
76.53
74.30
55.70
87.21
83.47
75.51
71.36
27.11
40.83
43.06
61.65
44.76
60.27
56.46
60.61
2
4
8
0
0
0
[
Mo(NO)
2
(dha-aap)(OH)] (I)
1.47
10
2
4
8
0
0
0
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X
electron density each atom has we can determine the atomic
partial charge
rðrÞ ¼
h r ðrÞ
(xxi)
i
i
i
*
i
Ð
r ðrÞ ¼ j ðrÞj ðrÞ and h
i
accounts for the orbital occupation
i
i
q
A
¼ Z
A
ꢀ r
A
(r)dr
(xxviii)
X
j ðrÞ ¼
C
aica
(xxii)
i
a
However, there is a problem; the charge can be distributed in
different ways by different methods qualitatively. As there is no
observable property associated with the “partial charge” and
So,
X
*
a
riðrÞ ¼
C
ai
C
bic c
(xxiii) also there isn't any reference value to which computed values
can be compared. Thus there is also no way to evaluate the
accuracy. It is very important not to over interpret data provided
by population methods as partial charges are articial, they do
b
ab
So,
X
X
*
a
rðrÞ ¼
hi
C
bic c
(xxiv)
b
not present an observable property of atoms or molecules.
One localization ad population analysis method that very
popular is the natural bond order analysis. In this method natural
i
ab
If we interchange the summation indices, which basically atomic orbitals that are effective orbitals of an atom in the
means we change the order in which we sum up all the indi- particular molecular environment (rather than isolated or in gas
vidual terms:
phases) are determined. There are also the maximum occupancy
orbitals. NBOs are localized at few centre MOs that reect Lewis
like bonding structure. The natural atomic charges of a repre-
XX
*
a
rðrÞ ¼
hiCai
C
bic c
(xxv)
b
ab
i
2
sentative complex, [Mo(NO) (amphp-aap)(OH)] obtained by NBO
*
a
and Mulliken population analysis with B3LYP/LANL2DZ basis set
are compared in Fig. 18. The comparison between Mulliken's net
charges and the atomic natural ones is not an easy task since the
theoretical background of the two methods was very different.
Looking at the results there are surprising differences between
(xxvii) the Mulliken's and the NBO charges. The observation of the data
S
ab ¼ c c is the overlap matrix
(xxvi)
b
P
Dab ¼
hiCaiCbi is the density matrix and we write r(r) in
i
a simplied form,
X
rðrÞ ¼
ab ab
D S
ab
3 5 7 16
of the complex 2 shows that the atoms namely C , C , C , C14, C ,
C17,C22, C24, Mo36 and all hydrogen bear positive charge both in
NBO and Mulliken analyses. The remaining atoms possess
negatively charges over them in both the analysis. It is noticeable
that N33 atom of one of the two NO ligands, is negatively charged
in Mulliken scale but has positive partial charge in NBO analysis.
This demonstrates the redistribution of charges when compared
Population analysis methods divide up DabSab to obtain
numbers that tell us where the electron density in a system
resides. A few of more common wave function population
analyses methods include Mulliken, Lowdin, Roby, Mayer,
Cioslowski, Charge decomposition analysis (CDA) and Natural
100–105
with the NPA analysis of representative Schiff base.
Bond Order (NBO).
Population methods also assign each atom a partial charge.
Each atom centre is positively charged core (charge Z ) sur-
ꢄ ꢅ
ð
0
3
0
N
r r d r
ꢆ
X
Z
A
A
VðrÞ ¼
ꢀ
ꢆ
(xxix)
jr ꢀ R
j
A
ꢆr ꢀ r
0
ꢆ
rounded by shielding electron, once we know how much
A
Fig. 18 Graphical presentation of Mulliken and NBO population analysis of complex 2.
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Fig. 19 Electron density plot and incremental distinction of highly electropositive and highly electronegative regions of complex 2.
The MESP diagram is used to understand the interactive potential electrophilic sites. The molecular electrostatic poten-
behavior of a molecule, in that negative regions can be regarded tials of the model complex is given in Fig. 19, displaying molec-
as nucleophilic centers, whereas the positive regions are ular shape, size and electrostatic potential values. The MESP map
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of the complex indicates the coordination sphere is the region of
most negative potential. The hydrogen and nitrogen atoms in
a ligand bear the region of maximum positive charge. It is
noteworthy here that the two hydrogens attached to the electro-
negative oxygen of the coordinated water molecule are most
electropositive. The predominance of green region in the MESP
surfaces corresponds to a potential halfway between the two
extremes red and dark blue color. A scheme has been devel-
oped by changing numerical assignment decreased by one unit,
a stage reached when the two most electropositive and the most
electronegative region become quite distinctive as shown in
Fig. 19.
7 S. M. O. Quintal, H. I. S. Nogueira, H. M. Carapuca, V. Felix
and M. G. B. Drew, J. Chem. Soc., Dalton Trans., 2001, 0,
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106
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Conclusions
The comparative experimental and theoretical study of pyr-
azolone Schiff base dinitrosylmolybdenum(0) complexes revealed
that the complexes bear a cis-octahedral geometry. The experi-
mental and theoretical data were found in excellent agreement
with one another. The evaluation of thermal chemistry using
different methods indicate the Freeman Carrol method exhibits
quite different readings as compared with other three methods
regarding the TG-based kinetic and thermodynamic studies. In
vitro anticancer and antimicrobial actions also exhibited high
potent anticancer and antimicrobial activity of the compounds.
Overall, the investigation suggests that the compounds reported
so far are good future tools to be biologically tested against more
virulent diseases.
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Conflicts of interest
24 L. L. Thomson, F. G. Lawton, R. G. Knowles, J. E. Basley,
V. Riversomoreno and S. Moncada, Cancer Res., 1994, 54,
No conict(s) of interest is declared by the authors.
1
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2
Acknowledgements
2
The authors thankfully acknowledge Vice Chancellor, R. D.
University Jabalpur, India, for his support in developing the lab
infrastructure. SAIF, IIT Mumbai, UGC networking Centre
Hyderabad Central University, PBRI, Bhopal, Food Science
Department Kashmir University and IIT, Chennai are also
gratefully acknowledged for rendering necessary lab facilities.
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