Synthesis, crystal structure and catecholase activity of a Ni(II) complex derived from a tetradentate Schiff base ligand

Article abstract of DOI:10.1007/s12039-014-0742-5

A new nickel(II) complex [Ni(L)] (1) [H₂L = 1,1^′-(1E,1^′E)-(propane-1,3-diylbis(azan-1-yl-1-ylidene))bis(methan-1-yl-1-ylidene)dinaphthalen-2-ol] was synthesized and X-ray crystallographically characterized. 1 crystallizes

Full text of DOI:10.1007/s12039-014-0742-5

J. Chem. Sci. Vol. 126, No. 6, November 2014, pp. 1635–1640. ꢀc Indian Academy of Sciences.
Synthesis, crystal structure and catecholase activity of a Ni(II) complex
derived from a tetradentate Schiff base ligand
a
b
a
PRADIPTA KUMAR BASU , MERRY MITRA , AMRITA GHOSH ,
c
d
b,∗
LATIBUDDIN THANDER , CHIA -HER LIN and RAJARSHI GHOSH
Department of Chemistry, Durgapur Government College, Durgapur, Burdwan 713 214, India
Department of Chemistry, The University of Burdwan, Burdwan 713 104, India
Department of Chemistry, Hooghly Mohsin College, Chinsurah, Hooghly 712 101, India
Department of Chemistry, Chung Yuan Christian University, Chung Li, Taiwan 32023, Republic of China
a
b
c
d
e-mail: rajarshi_chem@yahoo.co.in
MS received 23 July 2014; revised 4 September 2014; accepted 16 September 2014
ꢁ
ꢁ
Abstract. A new nickel(II) complex [Ni(L)] (1) [H2L = 1,1 -(1E,1 E)-(propane-1,3-diylbis(azan-1-yl-1-
ylidene))bis(methan-1-yl-1-ylidene)dinaphthalen-2-ol] was synthesized and X-ray crystallographically char-
acterized. 1 crystallizes in orthorhombic crystal system with Cmc21 space group. The unit cell dimensions
of the crystal are a = 30.6345(4)Å, b = 8.45340(10)Å, c = 7.75180(10)Å. Structural analysis reveals a
tetradentate chelation behaviour of the dianionic ligand H2L having a distorted square planar geometry around
Ni(II) with NiN2O2 chromophore in 1. The title complex 1 behaves as an effective catalyst towards oxida-
tion of 3,5-ditertiarybutyl catechol (3,5-DTBC) in acetonitrile to its corresponding quinone derivative in air.
−
5
−1
The reaction follows first-order reaction kinetics with rate constant 4.28 × 10 min . The reaction follows
−
1
Michaelis-Menten enzymatic kinetics with a turnover number of (Kcat ) 140.72h in acetonitrile.
Keywords. Nickel(II); Schiff base; X-ray structure; Catecholase activity.
1
. Introduction
derivatives to their corresponding quinones. Moreover,
the straightforward structure-property relationship in
catecholase activity is yet to be explored appropriately.
Therefore designing new molecules with catecholase
activity is attractive even today.
Herein, we report the synthesis and crystallographic
characterization of a mononuclear Ni(II) complex with
a dianionic (N,O) donor Schiff base ligand which catal-
yses a 3,5-ditertiarybutyl catechol to the correspond-
ing quinone derivative in acetonitrile in air. An inves-
tigation of Michaelis-Menten enzyme kinetics along
with the calculation of turnover number of the catalytic
reaction is also reported.
Oxidation of a range of o-diphenols (catechols) in
presence of the enzyme catecholase to corresponding
quinone is known as catecholase activity1 which is
a very important process in bacteria, fungi and plants.
Crystal structure determination of the met-form of cat-
echolase in 1988 revealed that the active site of the
enzyme consists of a hydroxo bridged dicopper(II) cen-
tre in which each copper(II) centre is coordinated to
three histidine nitrogens and adopts a trigonal pyrami-
–5
6
dal environment with one nitrogen in the apical site.
As soon as this discovery was made, a huge number of
dicopper(II) molecules with several nitrogen contain-
ing ligands and bridging moieties designed to model
catecholase. Some monocopper(II) compounds and
compounds with Mn(II/III),
Zn(II) have also been reported in literature that mimic
catecholase activity. Recent investigations have shown
that a few nickel(II) complexes with Schiff base lig-
ands can also mediate such catalytic oxidation. All
these findings reveal that the metal ion oxidation state,
ligand environment, nuclearity of the complexes, etc.
play important role(s) in catalyzing catechols and its
1
–5
7
2. Experimental
7
e,8
9
10
Fe(III), Co(II/III),
11
2.1 Materials
Nickel dichloride (NiCl . 6H O), 1,3-diaminopropane,
2
2
12
3,5-di-tert-butylcatechol (Aldrich, UK) and all other
solvents were purchased from the respective concerns
and used as received. Solvents were dried according to
standard procedure and distilled prior to use.
The starting material, 2-hydroxy-1-naphthaldehyde
was prepared according to the published procedure in
∗
For correspondence
1
635

1
636
Pradipta Kumar Basu et al.
radiation (λ = 0.71073 Å) at 293(2) K. Systemati-
CHO
N
N
cally absent reflections led to the identification of space
groups Cmc21 for 1. Of the 9247 total reflections for the
complex, 2510 with [I > 2r(I)] were used for structure
solutions. The structures were solved by direct meth-
OH
NH2
NH2
HO
OH
(
1 mole)
EtOH, reflux, 3h
(
2 moles)
H2L
ods, and the structure solution and refinement were
ꢁ
2
Scheme 1. Synthesis of the Schiff base ligand: 1,1 -(1E, based on |F |. All non-hydrogen atoms were refined
ꢁ
1
1
E)-(propane-1,3-diylbis(azan-1-yl-1-ylidene))bis(methan-
-yl-1-ylidene)dinaphthalen-2-ol.
with anisotropic displacement parameters whereas
hydrogen atoms were placed in calculated positions
when possible and given isotropic U values 1.2 times
13
literature. The ligand H L was synthesised (scheme 1) that of the atom to which they are bonded. The final dif-
2
by refluxing 2-hydroxy-1-naphthaldehyde(1.0 g, 5.8 ferences Fourier map showed the maximum and min-
−3
mmol) with 1,3-diaminopropane (0.215 g, 2.9 mmol) in imum peak heights at 0.7897 and −0.8656 eÅ for
3
0 mL dehydrated ethanol. After 3 h, the reaction solu- 1 with no chemical significance. All calculations were
tion was evaporated under reduced pressure to yield a carried out using SHELXL-97 and ORTEP-32. The
yellow coloured solid, which was dried under vacuum crystal data and data collection parameters are listed in
14
15
and stored over CaCl for subsequent use.
table 1.
2
−4
−3
For catecholase activity study, 1 × 10 mol dm so-
−2
lution of 1 (0.0009 g) was treated with 1 × 10 mol
−3
3. Results and Discussion
dm (100 equivalents) of 3,5-DTBC (0.0222 g) under
aerobic conditions.
3.1 Synthesis and formulation
2.2 Physical measurements
Reaction at room temperature with required molar ratio
among nickel(II) salt and H L in acetonitrile produces
2
Elemental analyses (carbon, hydrogen and nitrogen)
were performed on a Perkin-Elmer 2400 CHNS/O ele-
mental analyzer. UV-Vis and IR spectra (KBr discs,
the complex 1 in good yield. The complex was charac-
terized by microanalytical (C, H and N), spectroscopic
and other physicochemical results. The microanalytical
data are in good conformity with the formulations of 1.
The moisture insensitive complexes are stable over long
periods of time in powdery and crystalline states, and
are soluble in methanol, acetonitrile, etc. In the IR
−1
4000–300 cm ) were recorded using a Shimadzu UV-
Vis 2450 spectrophotometer and Perkin-Elmer FT-IR
1
model RX1 spectrometer, respectively. The H NMR
spectral data were collected in CDCl on a Bruker
3
400 MHz spectrometer.
−1
spectra, relatively intense peaks around 1593 cm due
to the C=N stretching frequency, and weak bands in
−1
the range 2980–2900 cm due to the aliphatic C-H
stretching frequency, appear in both the complexes.
2.3 Preparation of 1
Compound 1 was prepared by dropwise addition of H L
2
(
0.1 g, 0.262 mmol) solution in acetonitrile (15 mL)
into a stirring solution of nickel dichloride (0.062 g,
.262 mmol) in methanol-acetonitrile mixture (15 mL).
3
.2 X-ray structure
0
1
crystallizes in the orthorhombic space group Cmc21.
The resulting red-brown coloured solution was kept in
open air for slow evaporation. After 2–3 days, the deep
brown crystals of 1 was collected, washed with hexane
and dried in vacuo over silica gel indicator.
The thermal ellipsoid plot of 1 is given in figure 1. Ni(II)
in 1 adopts a square planar geometry with NiN O2
2
chromophore as is evident from the bond angle-bond
distance table (table 2). The imine nitrogens (N1 and
N1*) and phenoxooxygens (O1 and O1*) coordinate
to the metal centre. The N1 and N1*, and O1 and
O1* are in mutually cis orientation. Each of the metal-
nitrogen and metal-oxygen bond distances are 1.873(2)
and 1.845(19) Å, respectively. In the complex there is
Yield: 88.5%, Anal. calc. forC H N O Ni (1): C,
25
20
2
2
6
6
8.38; H, 4.59; N, 6.38; Found: C, 68.24; H, 4.50; N,
−1
.32. Selected IR bands (KBr pellet, cm ): 1593(s).
UV-Vis (λ, nm, MeOH): 416, 334, 313, 266, 217.
no deviation of the metal centre from the N O square
plane. The bond angle and bond distances of the com-
2.4 X-ray diffraction study
2
2
Single crystal data of 1 were collected on a Bruker plex are comparable with the other reported square
16
AXS KAPPA APEX II diffractometer using Mo-Kα planar nickel(II) complexes.

Catecholase activity of a Ni(II) complex
1637
Table 1. Crystal data and structure refinement for 1.
Empirical formula
Formula weight
Temperature
C25H20N2O2Ni
439.14
293(2) K
Wavelength
Crystal system
Space group
0.71073Å
Orthorhombic
C m c 21
Unit cell dimensions
a = 30.6345(4)Å
b = 8.45340(10)Å
c = 7.75180(10)Å
α = 90◦
◦
β = 90
◦
γ = 90
3
Volume
2007.45(4)Å
Z
4
3
Density (calculated)
Absorption coefficient
F(000)
1.453 Mg/m
0.991 mm
912
−
1
3
Crystal size
Theta range for data collection
0.25 × 0.15 × 0.15 mm
◦
1.33 to 28.28
Index ranges
−33 <= h <= 40, −11 <= k <= 9, −10 <= l <= 10
Reflections collected
Independent reflections
Completeness to theta = 28.28
Absorption correction
Max. and min. transmission
Refinement method
Data / restraints / parameters
Goodness-of-fit on F2
Final R indices [I> 2sigma(I)]
R indices (all data)
Absolute structure parameter
Largest diff. peak and hole
9247
2510 [R(int) = 0.0285]
100.0 %
◦
multi scan
0.8656 and 0.7897
Full-matrix least-squares on F
2
2510/ 1/140
1.011
R1 = 0.0352, wR2 = 0.0778
R1 = 0.0562, wR2 = 0.0866
0.027(17)
−3
0.530 and −0.170 e.Å
3
.3 Catecholase activity: Spectrophotometric study
which is highly stable and shows a maximum absorp-
7
e
tion at 401 nm in methanol. Solution of 1 was treated
with 100 equivalents of 3,5-DTBC under aerobic condi-
tions. The repetitive UV-Vis spectral scan was recorded
in pure acetonitrile (figure 2). Spectral bands at 416,
In order to study the catecholase activity of the com-
plex 1, 3,5-DTBC with two bulky t-butyl substituents
on the ring and low quinone-catechol reduction poten-
tial has been chosen as substrate. This makes it eas-
ily oxidized to the corresponding o-quinone, 3,5-DTBQ
334, 313, 266 and 217 nm appear in the electronic spec-
trum of complex 1, whereas 3,5-DTBC shows a single
Figure 1. ORTEP of 1 with 30% thermal ellipsoid plot.

1
638
Pradipta Kumar Basu et al.
◦
Table 2. Bond lengths [Å] and angles [ ] for 1.
Bond distances
1.8458(19)
1.873(2)
Ni(1)-O(1)
Ni(1)-N(1)
Ni(1)-O(1*)
Ni(1)-N(1*)
1.8458(19)
1.873(2)
Bond angles
O(1)-Ni(1)-O(1*)
O(1)-Ni(1)-N(1*)
N(1)-Ni(1)-N(1*)
82.53(12)
173.62(9)
95.08(14)
O(1)-Ni(1)-N(1)
O(1*)-Ni(1)-N(1*)
91.18(9)
91.18(9)
band at 282 nm. As the reaction proceeds, there is a 3.4 Enzyme kinetics study
gradual decrease in intensity of the band at 282 nm due
Kinetic experiments were performed spectrophotomet-
to the catechol and a new band is formed at 415 nm
which indicates the formation of the respective quinone
derivative. The product 3,5-DTBQ was purified by col-
umn chromatography, isolated in high yield (89.70%)
by slow evaporation of the eluant and was identified
rically with complex 1 and the substrate 3,5-DTBC in
◦
acetonitrile, thermostated at 20 C. 0.04 mL of the com-
plex solution, with a constant concentration of 1 ×
−4
10
M, was added to 2 mL of 3,5-DTBC of a partic-
1
1
ular concentration (varying its concentration from 1 ×
by H NMR spectroscopy (figure S1). HNMR (CDCl ,
3
−
3
−2
1
0
M to 1 × 10 M) to achieve the ultimate concen-
4
00 MHz): δH = 1.16 (s, 9H), 1.20 (s, 9H), 6.15 (d,
−4
tration of the complex as 1 × 10 M. The conversion of
J = 2.4 Hz, 1H), 6.86 (d, J = 2.4 Hz, 1H).
3
,-5-DTBC to 3,5-DTBQ was monitored with time at a
In order to find out the reaction rate between 3,5-
DTBC and 1, the reaction kinetics between them was
studied by observing the time dependent change in
absorbance at a wavelength of 415 nm. The colour
of the solution was gradually turned into deep brown
indicative of gradual conversion of 3,5-DTBC to 3,5-
DTBQ. The difference in absorbance ꢀA at 415 nm,
wavelength of 415 nm for solutions in MeCN. The rate
for each concentration of the substrate was determined
by the initial rate method.
The rate versus concentration of substrate data were
analyzed on the basis of Michaelis-Menten approach
of enzymatic kinetics to get the Lineweaver-Burk (dou-
ble reciprocal) plot as well as the values of the various
was plotted against time to obtain the velocity (r ) for
o
kinetic parameters Vmax, K and K . The observed rate
that particular catalyst to substrate concentration ratio
M
cat
vs. [substrate] plot in acetonitrile solution as well as
Lineweaver-Burk plot is given in figure 4. The kinetic
(
figure 3). A first-order catalytic reaction was observed,
−5
−1
with velocity 4.28 × 10 min for 1.
0
0
0
0
0
0
.05
.04
.03
.02
.01
.00
0
0
0
0
0
0
0
.0030
.0025
.0020
.0015
.0010
.0005
.0000
3
50
400
450
500
550
0
10
20
30
40
50
60
(
nm)
Time (min)
Figure 2. Change in spectral pattern of complex 1 after Figure 3. A plot of the difference in absorbance (ꢀA) vs
addition of 3,5-DTBC during 6 h of reaction in acetonitrile. time.

Catecholase activity of a Ni(II) complex
1639
0
0
0
0
0
0
0
0
0
.0000040
.0000035
.0000030
.0000025
.0000020
.0000015
.0000010
.0000005
.0000000
5
4
4
3
3
2
00000
50000
00000
50000
00000
50000
0
200
400
600
800
1000
1
/[Substrate]
0.000
0.002
0.004
0.006
0.008
0.010
[
Substrate] (M)
Figure 4. Plot of rate vs. [substrate] in presence of 1 in MeCN; inset:Lineweaver-Burk plot.
Table 3. Kinetic parameters for the oxidation of 3,5-DTBC catalyzed by 1.
−
−1
Kcat (h )
Solvent
MeCN
Vmax (Ms 1
)
Std. error
KM(M)
Std. error
3.91 × 10−
6
4.74 × 10−7
9.47 × 10−4
7.30 × 10−5
140.72
parameters are listed in table 3. The turnover number Supplementary Information
−1
(
K ) found is 140.72 h in MeCN.
cat
CCDC No. 1009492 contains the supplementary crys-
tallographic data for 1. These data can be obtained
free of charge via http://www.ccdc.cam.ac.uk/conts/
retrieving.html, or from the Cambridge Crystallo-
4. Conclusion
We have designed and synthesized a new nickel(II) graphic Data Centre, 12 Union Road, Cambridge
compound 1 which has been characterized by X- CB2 1EZ, UK; fax: (+44) 1223-336-033; or e-mail:
ray crystallography. The newly synthesized compound deposit@ccdc.cam.ac.uk
catalyses the oxidation of 3,5-ditertiarybutyl cate-
chol to its corresponding quinone form in acetoni-
trile solution. Kinetic investigation revealed that the
reaction followed the first order path with rate con-
Acknowledgement
−5
−1
stant 4.28 × 10 min . The turnover number reported MM and AG are thankful to The University of Burd-
−1
for this very catalytic reaction is 140.72 h which wan and DST, New Delhi (Govt. of India), respectively
is quite high in comparison to a recently reported for their senior research fellowships. The financial
12a
work.
support from the DST (F. No. SR/FT/CS-83/2010 dt.

1
640
Pradipta Kumar Basu et al.
1
1-02-2011) UGC and DBT, New Delhi (Govt. of
A R, Lin C-H, Ribas J and Ghosh R 2013 Polyhedron
1 15
6
India) are also gratefully acknowledged.
8
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A 2012 Inorg. Chem. 51 4265; (b) Mukherjee S,
Weyhermüller T, Bothe E, Wieghardt
K
and
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