Copper(II) complexes with neutral Schiff bases: Syntheses, crystal structures and DNA interactions

Article abstract of DOI:10.1016/j.poly.2011.10.037

The synthesis and X-ray structural characterisation of a new Cu(II) complex, [Cu(L¹)Cl](ClO₄)·CH₃OH (1) [L¹ = N,N′-bis((pyridine-2-yl)phenylidene)-1,3-diaminopropan-2- ol], has been described in this work. The s

Full text of DOI:10.1016/j.poly.2011.10.037

Polyhedron 31 (2012) 671–675
Contents lists available at SciVerse ScienceDirect
Polyhedron
journal homepage: www.elsevier.com/locate/poly
Copper(II) complexes with neutral Schiff bases: Syntheses, crystal structures
and DNA interactions
Abhijit Pal a,1, Bhaskar Biswas a,1, Sunil Kanti Mondal b, Chia-Her Lin c, Rajarshi Ghosh a,
⇑
a Department of Chemistry, The University of Burdwan, Burdwan 713 104, India
b Department of Biotechnology, The University of Burdwan, Burdwan 713 104, India
c Department of Chemistry, Chung Yuan Christian University, Chung Li, Taiwan 32023, ROC
a r t i c l e i n f o
a b s t r a c t
The synthesis and X-ray structural characterisation of a new Cu(II) complex, [Cu(L1)Cl](ClO4)ꢀCH3OH (1)
[L1 = N,N0-bis((pyridine-2-yl)phenylidene)-1,3-diaminopropan-2-ol], has been described in this work. The
structural study reveals that the Cu(II) centre in 1 has a square pyramidal geometry with a trigonality
Article history:
Received 23 September 2011
Accepted 24 October 2011
Available online 13 November 2011
index
s = 0.43, being coordinated by the organic ligand and a chloro group. The interaction of complex
1 and another complex previously reported by our group, [Cu(L2)](ClO4)2 (2) [L2 = N-(1-pyridin-2-yl-
phenylidene)-N0-[2-({2-[(1-pyridin-2-ylphenylidene)amino]ethyl}amino)ethyl]ethane-1,2diamine], with
calf thymus DNA (CT-DNA) has been investigated using absorption and emission spectral studies. The
binding constant (Kb) and the linear Stern–Volmer quenching constant (Ksv) have been determined.
Ó 2011 Elsevier Ltd. All rights reserved.
This work is our tribute to Sir P.C. Rây on the
eve of his 150th birth anniversary
Keywords:
Copper(II)
Schiff bases
DNA interactions
Spectrophotometry
Fluorimetry
1. Introduction
ethane-1,2diamine, Scheme 1] [7] with CT-DNA by absorption and
emission spectral studies.
The design and synthesis of new cationic complexes that interact
with DNA are of considerable interest nowadays as the affinity and
selectivity of molecules in binding to nucleic acids are valuable for
the rational design of new diagnostic and therapeutic agents [1–5].
These metal complexes are known to bind to DNA through a series
2. Experimental
2.1. Materials
of interactions, such as
p-stacking interactions associated with
High purity 2-benzoylpyridine (Fluka, Germany), copper(II)
chloride dihydrate (E. Merck, India), sodium perchlorate (Alfa
Aesar, Germany) and 1,3-diaminopropan-2-ol (Aldrich, UK) were
purchased from the respective concerns and used as received.
The calf thymus (CT) DNA and ethidium bromide (EB) were ob-
tained from Sigma.
Caution! Perchlorate salts of metal ions are potentially
explosive, especially in the presence of organic ligands. Only a
small amount of material should be prepared and handled with
care.
intercalation of aromatic heterocyclic groups between the base pairs,
hydrogen-bonding and van der Waals interactions in the case of bind-
ing to the groove of the DNA helix [6]. Copper, with its relevant oxida-
tion states +1 and +2, has been extensively used in metal mediated
DNA cleavage [2–5]. Copper(II) complexes under certain ligand
environments have also been shown to bring about photocleavage
of DNA as well as RNA [2–4]. In this present report, we determine
the binding constants (Kb) and the linear Stern–Volmer quenching
constants (Ksv) for the interaction of the new Cu(II) complex
[Cu(L1)Cl](ClO4)ꢀCH3OH (1) [L1 = N,N0-bis((pyridine-2-yl)phe nylid-
ene)-1,3-diaminopropan-2-ol, Scheme 1] and a previously reported
complex, [Cu(L2)](ClO4)2 (2) [L2 = N-(1-pyridin-2-yl-phenylidene)-
N0-[2-({2-[(1-pyridin-2-ylphenylidene)amino]ethyl}amino) ethyl]
2.2. Physical measurements
Elemental analyses (carbon, hydrogen and nitrogen) were per-
formed on a Perkin-Elmer 2400 CHNS/O elemental analyzer. IR
spectra (KBr discs, 4000–300 cmꢁ1) were recorded using a Per-
kin-Elmer FT-IR model RX1 spectrometer. Ground-state absorption
and steady-state fluorescence measurements were made with a
⇑
Corresponding author. Tel.: +91 342 2533913x424; fax: +91 342 2530452.
E-mail address: rajarshi_chem@yahoo.co.in (R. Ghosh).
These two authors have made an equal contribution to this work.
1
0277-5387/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2011.10.037

672
A. Pal et al. / Polyhedron 31 (2012) 671–675
Table 1
N
N
N
Crystal data and structure refinement parameters for 1.
O
H
Empirical formula
Formula weight
T (K)
Wavelength (Å)
Crystal system
Space group
Unit cell dimensions
a (Å)
C28H28N4O6Cl2Cu
650.98
295(2)
0.71073
orthorhombic
P212121
C
C
N
L 1
8.3120(2)
9.8493(2)
b (Å)
c (Å)
34.7109(7)
a
b (°)
(°)
90
90
N
N
N
N
C
c
(°)
90
C
V (Å3)
2841.69(11)
Z
4
Dcalc (mg/m3)
1.522
1.006
1340
N
N
Absorption coefficient (mmꢁ1
F(000)
)
L 2
Crystal size (mm3)
0.45 ꢂ 0.35 ꢂ 0.32
Theta range for data collection (°)
Index ranges
2.15–28.33
Scheme 1.
ꢁ11 6 h 6 11, ꢁ13 6 k 6 13,
ꢁ45 6 l 6 39
Reflections collected
26597
Jasco model V-530 UV–Vis spectrophotometer and a Hitachi model
F-4010 spectrofluorimeter, respectively.
Independent reflections
Completeness to theta = 28.33°
Absorption correction
Tmax and Tmin
7037 [Rint = 0.0570]
99.4%
semi-empirical from equivalents
0.725 and 0.662
full-matrix least-squares on F2
7037/1/371
2.3. Preparation of the Schiff bases and the complexes
Refinement method
Data/restraints/parameters
The Schiff base L1 was prepared following a reported method [8]
with a little modification. The details are given below:
2-Benzoylpyridine (0.366 g, 2 mmol) was refluxed with 1,3-dia-
minopropan-2-ol (0.086 g, 1 mmol) in 30 ml dehydrated alcohol.
After 10 h the reaction solution was evaporated under reduced
pressure to yield a gummy mass, which was dried and stored in va-
cuo over CaCl2 for subsequent use. Yield, 0.469 g (72%). Anal. Calc.
for C27H23N4O (L1): C, 77.23; H, 5.52; N, 13.34. Found: C, 76.52; H,
4.90; N, 12.92%. IR (KBr, cmꢁ1): 1632 (s), 3375 (s).
The synthetic procedure for complex 2 is described elsewhere
[7]. Complex 1 was synthesized from the chloride salt of copper(II)
using a 1:1 molar ratio of the metal salt and L1 in MeOH at room
temperature. X-ray quality single crystals of 1 separated out within
a week.
Goodness-of-fit (GOF) on F2
1.047
Final R indices [I > 2
R indices (all data)
Absolute structure parameter
Largest difference in peak and hole
r
(I)]
R1 = 0.0584, wR2 = 0.1555
R1 = 0.0875, wR2 = 0.1691
0.013(19)
0.775 and ꢁ0.680
(e Åꢁ3
)
ꢁ0.680 e Åꢁ3 for 1 with no chemical significance. All calculations
were carried out using SHELXL-97 [9] and ORTEP-32 [10]. The crys-
tal data and data collection parameters are listed in Table 1.
3. Results and discussion
3.1. Synthesis and formulation
2.3.1. Preparation of 1
The ligand L1 was synthesized by refluxing 1,3-diaminopropan-
2-ol with 2-benzoylpyridine in 1:2 molar ratio in dehydrated alco-
hol. Compound 1 was prepared using the chloride salt of copper(II)
and L1 in a proper molar ratio as appeared in the compound. The
compound was recrystallised from a methanol–water mixture. It
was characterised using microanalytical, spectroscopic and other
physicochemical results. The exact coordination sphere was deter-
mined by single crystal X-ray crystallography. In the IR spectrum
A methanolic solution (5 cm3) of L1 (0.419 g, 1 mmol) was
added dropwise to a solution of CuCl2ꢀ2H2O (0.170 g, 1 mmol) in
the same solvent (10 cm3). NaClO4 (0.122 g, 1 mmol) was then
mixed in the reaction mixture. The deep green solution was filtered
and the supernatant liquid was kept in air for slow evaporation.
Yield: 0.469 g (72% based on metal salt). Anal. Calc. for
C
28H28N4O6Cl2Cu (1): C, 51.66; H, 4.33; N, 8.60. Found: C, 51.30;
H, 4.17; N, 8.06%. IR (KBr, cmꢁ1): 1618, 1593 (
C@N), 472 ( Cl),
3224 ( OH), 1286, 1117, 1084, 625 (mClO ); UV–Vis (kmax, nm): 268.
m
m
the well resolved peak at 1592 cmꢁ1 is attributed to
m(C@N) [11].
m
4
The compound shows weak bands in the range 2980–2900 cmꢁ1
that are assignable to the aliphatic C–H stretching frequency.
2.4. X-ray diffraction studies
Single crystal data of 1 were collected on a Bruker AXS KAPPA
APEX II diffractometer using MoK radiation (k = 0.71073 Å) at
3.2. X-ray structures
a
295(2) K. Systematically absent reflections led to the identification
of space group P212121 for 1. Of the 26597 total reflections for the
complex, 7037 with [I > 2r(I)] were used for structure solutions.
The structures were solved by direct methods, and the structure
solution and refinement were based on |F2|. All non-hydrogen
atoms were refined with anisotropic displacement parameters
whereas hydrogen atoms were placed in calculated positions were
possible and given isotropic U values 1.2 times that of the atom to
which they are bonded. The final differences Fourier map showed
the maximum and minimum peak heights at 0.775 and
Oak Ridge Thermal Ellipsoid Plots (ORTEP) of 1 and 2 are repre-
sented in Figs. 1 and 2. The structure of 2 is described in our pre-
vious report [7]. Bond angles and distances for the structure of 1
are listed in Table 2. The coordination geometry at the copper(II)
centre of 1 is best described as a square pyramid, as exemplified
by its
s
value (
s
= 0.43) [12]2 with a CuN4Cl chromophore. The imine
2
s
=(a
ꢁ b)/60;
a
= largest L–M–L bond angle, b = second largest bond angle; If the
s
value is in between 0 and 0.5, then the geometry is square pyramid (Sq py) and if the
value is in between 0.5 and 1.0, then the geometry is trigonal bipyramid (TBP).

A. Pal et al. / Polyhedron 31 (2012) 671–675
673
3.3. DNA interactions
3.3.1. Spectrophotometric investigation
The mode in which the complexes are bound to DNA was inves-
tigated by absorption spectra. Hyperchromic and hypochromic ef-
fects are spectral features concerning changes in the double-helix
structure of DNA. These spectral changes reflect the changes in
the conformation and structure of DNA after the complex binds
to it [6,13]. The addition of 1 and 2 separately to DNA caused an
appreciable increase in the absorption intensity, which is a typical
hyperchromic effect (Figs. 3 and 4). Both the compounds show a
maximum absorbance at 268 nm in absence of DNA. They have
no labile reaction centre (replaceable H2O or anything else) and
hence cannot coordinate with nucleotide bases. Spectrophotomet-
ric investigations also support this. Complexation of Cu(II) with
DNA bases is expected to show appreciable changes to the elec-
tronic spectrum. However, no marked changes were observed in
the electronic spectra of the complexes (kmax for both 1 and 2 ap-
pear at 274 nm in presence of DNA) on addition of DNA, ruling out
the possibility of coordinative binding to DNA donor atoms. It has
been shown that the intercalators will shift the wavelength of the
maximum absorbance towards longer wavelengths and virtually
show hypochromism [14]. In the present case, however, with the
addition of DNA these Cu(II) systems exhibit a small increase in
kmax. The kmax values for the complexes change from 268 to
274 nm. These small shifts in kmax are accompanied by a small in-
crease in the absorbance intensity. So these changes in kmax cannot
account for coordinative binding. It is more in keeping with groove
binding, leading to small perturbations [6]. Such small increases in
kmax and hyperchromicity have been observed in the case of some
porphyrin and copper complexes on their interaction with DNA
[15]. This hyperchromism in the absorption intensity may proba-
bly be due to the dissociation of ligand aggregates [16] or due to
its external contact (surface binding) with the duplex [17].
Fig. 1. ORTEP representation of 1 with 30% ellipsoid probability.
The binding constants, Kb, for complexes 1 and 2 have been
determined from the plot of [DNA]/(eA
ꢁ
eF) versus [DNA] and have
been found to be 5.47 ꢂ 104 and 1.33 ꢂ 104 Mꢁ1, respectively (Figs.
5 and 6). The Kb values are lower than those reported for typical
intercalators (for ethidium bromide and [Ru(phen)2(dppz)]2
2+
)
[6a]. The observed value of the binding constant is more in keeping
with the groove binding of the Cu(II) complex 2 with DNA, as ob-
served in the case of the binding of tris(1,10 phenanthroline)ruthe-
nium(II) to DNA [6a].
Fig. 2. ORTEP view of 2 with 30% ellipsoid probability [7].
Table 2
2.0
e
Bond lengths (Å) and angles (°) for 1.
Bond distances
a
Cu(1)–N(1)
Cu(1)–N(2)
Cu(1)–Cl(1)
1.970(4)
1.971(4)
2.5293(15)
Cu(1)–N(3)
Cu(1)–N(4)
2.020(3)
1.987(4)
1.5
Bond angles
1.0
0.5
0.0
N(1)–Cu(1)–N(2)
N(1)–Cu(1)–N(4)
N(2)–Cu(1)–N(4)
N(1)–Cu(1)–N(3)
N(4)–Cu(1)–Cl(1)
N(3)–Cu(1)–Cl(1)
177.10(16)
96.06(16)
81.58(15)
80.70(15)
115.04(13)
93.65(11)
N(2)–Cu(1)–N(3)
N(4)–Cu(1)–N(3)
N(1)–Cu(1)–Cl(1)
N(2)–Cu(1)–Cl(1)
102.18(15)
151.13(16)
88.81(13)
90.67(11)
240
260
280
300
λ, nm
320
340
360
nitrogens (N1, N4) and pyridine nitrogens (N2, N3) occupy the equa-
torial plane of the square pyramid. The chloride atom resides in the
axial position. Here the Cu–N bond distances range from 2.020(3) to
1.970(4) Å. The Cu–Cl bond distance is 2.5293(15) Å.
Fig. 3. Electronic spectra of 1 through titration with CT-DNA in Tris–HCl buffer;
[Complex] = 1.0 ꢂ 10ꢁ4; [DNA]: (a) 0.0, (b) 2.0 ꢂ 10ꢁ6, (c) 4.0 ꢂ 10ꢁ6, (d) 6.0 ꢂ 10ꢁ6
,
(e) 8.0 ꢂ 10ꢁ6 (mol Lꢁ1). The increase of DNA concentration is indicated by an
arrow.

674
A. Pal et al. / Polyhedron 31 (2012) 671–675
f
0.60
0.55
0.50
0.45
0.40
0.35
0.30
0.25
0.20
4.0
3.5
3.0
2.5
2.0
1.5
1.0
a
2
4
6
8
10
[DNA]X106
250 260 270 280 290 300 310 320 330 340 350
λ , nm
Fig. 6. Plot of [DNA]/(eA ꢁ eF) vs. [DNA] for the titration of CT-DNA with 2 in Tris–
HCl buffer, binding constant Kb = 1.33 ꢂ 104 Mꢁ1 (R = 0.9909 for five points).
Fig. 4. Electronic spectra of 2 through titration with CT-DNA in Tris–HCl buffer;
[Complex] = 1.97 ꢂ 10ꢁ5 (M); [DNA]: (a) 0.0, (b) 2.0 ꢂ 10ꢁ6, (c) 4.0 ꢂ 10ꢁ6, (d)
6.0 ꢂ 10ꢁ6, (e) 8.0 ꢂ 10ꢁ6, (f) 1.0 ꢂ 10ꢁ5 (mol Lꢁ1). The increase of DNA concentra-
tion is indicated by an arrow.
8000
a
7000
3.3.2. Ethidium bromide fluorescence quenching experiments
Ethidium bromide (EB) is chemically known as 3,8-diamino-5-
ethyl-6-phenylphenanthridinium bromide. It is a large, flat basic
molecule that resembles a DNA base pair. Because of its chemical
structure, it can intercalate into a DNA strand. EB has been used
to probe the interaction of a complex with DNA. To evaluate the
interaction mode of complexes 1 and 2, EB fluorescence intensity
quenching experiments were carried out. In fact the EB fluores-
cence intensity will be enhanced in the presence of DNA because
of its intercalation into the helix, and it is quenched by the addition
of another molecule that displaces EB from DNA [18]. Here, a sig-
nificant decrease of the fluorescence intensity of EB bound to
DNA was recorded by increasing the concentration of the com-
plexes (Figs. 7 and 8). This observation of EB fluorescence quench-
ing leads us to deduce that the copper(II) complexes may interact
with DNA through a groove binding mode, releasing some EB mol-
ecules from the EB–DNA system [19]. The quenching of EB bound
to DNA by the copper(II) complexes is in agreement with the linear
Stern–Volmer equation:
e
6000
5000
4000
3000
2000
1000
0
560 580 600 620 640 660 680 700 720 740
λ, nm
Fig. 7. Emission spectra of the CT-DNA–EB system in Tris–HCl buffer based on the
titration of 1. kex = 524 nm; [DNA] = 1.0 ꢂ 10ꢁ5; [complex]: (a) 0.0, (b) 0.97 ꢂ 10ꢁ5
,
(c) 1.94 ꢂ 10ꢁ5, (d) 2.91 ꢂ 10ꢁ5, (e) 3.88 ꢂ 10ꢁ5 (mol Lꢁ1). The arrow indicates the
increase of the complex concentration.
I0=I ¼ 1 þ Ksv½complexꢃ
8000
where I0 and
I represent the fluorescence intensities in the
a
absence and presence of quencher, respectively. Ksv is the linear
7000
e
6000
5000
4000
3000
2000
1000
0
14
12
10
8
6
560 580 600 620 640 660 680 700 720 740
λ, nm
2
3
4
5
6
7
8
[DNA]X106
Fig. 8. Emission spectra of the CT-DNA–EB system in Tris–HCl buffer based on the
titration of copper(II) complex 2. kex = 522 nm; [DNA] = 1.0 ꢂ 10ꢁ5; [complex]: (a)
0.0, (b) 1.0 ꢂ 10ꢁ5, (c) 2.0 ꢂ 10ꢁ5, (d) 3.0 ꢂ 10ꢁ5, (e) 4.0 ꢂ 10ꢁ5 (mol Lꢁ1). The arrow
indicates the increase of the complex concentration.
Fig. 5. Plot of [DNA]/(eA
ꢁ eF) vs. [DNA] for the titration of CT-DNA with 1 in Tris–
HCl buffer, binding constant Kb = 5.47 ꢂ 104 Mꢁ1 (R = 0.98432 for five points).

A. Pal et al. / Polyhedron 31 (2012) 671–675
675
1.9
1.8
1.7
1.6
1.5
1.4
1.3
1.2
1.1
interact with CT-DNA. The binding constants for the complexes
are found to be 5.47 ꢂ 104 and 1.33 ꢂ 104 Mꢁ1, respectively. The
linear Stern–Volmer quenching constants were determined as
1.92 ꢂ 104 (R = 0.996 for four points) and 1.49 ꢂ 104 (R = 0.99585
for four points), respectively. The spectral features indicate a
groove binding mode interaction of the complexes to DNA.
Acknowledgement
Financial support by the Department of Science and Technol-
ogy, New Delhi, India (F. No. SR/FT/CS-83/2010 dt. 11-02-2011) is
gratefully acknowledged by RG.
Appendix A. Supplementary data
CCDC 835459 contains the supplementary crystallographic data
for complex 1. These data can be obtained free of charge via http://
www.ccdc.cam.ac.uk/conts/retrieving.html, or from the Cambridge
Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ,
UK; fax: (+44) 1223-336-033; or e-mail: deposit@ccdc.cam.ac.uk.
10
15
20
25
30
35
40
6
[complex] x10
Fig. 9. Plot of I0/I vs. [complex] for the titration of CT-DNA–EB system with 1 using
a
spectrofluorimeter; linear Stern–Volmer quenching constant (Ksv
)
for
1 = 1.92 ꢂ 104 (R = 0.996 for four points).
References
[1] (a) N.H. Willams, B. Takasaki, M. Wall, J. Chin, Acc. Chem. Res. 32 (1999) 485;
(b) B. Lippert, Coord. Chem. Rev. 200–202 (2000) 487;
(c) C. Liu, M. Wang, T. Zhang, H. Sun, Coord. Chem. Rev. 248 (2004) 147.
[2] (a) X.-B. Yang, Y. Huang, J.-S. Zhang, S.-K. Yuan, R.-Q. Zeng, Inorg. Chem.
Commun. 13 (2010) 1421;
(b) S. Anbu, M. Kandaswamy, Polyhedron 30 (2011) 123.
[3] (a) S. Dhar, M. Nethaji, A.R. Chakravarty, Inorg. Chem. 45 (2006) 11043;
(b) P.K. Sasmal, A.K. Patra, M. Nethaji, A.R. Chakravarty, Inorg. Chem. 46 (2007)
11112.
1.6
1.5
1.4
1.3
1.2
1.1
[4] (a) V. Uma, A. Castineiras, B.U. Nair, Polyhedron 26 (2007) 3008;
(b) K. Dhara, J. Ratha, M. Manassero, X.-Y. Wang, S. Gao, P. Banerjee, J. Inorg.
Biochem. 101 (2007) 95.
[5] (a) G. Garc´ıa-Friaza, A. Ferna´ndez-Botello, J.M. Pe´rez, M.J. Prieto, V. Moreno, J.
Inorg. Biochem. 100 (2006) 1368;
(b) J. Sun, S. Wu, H.-Y. Chen, F. Gao, J. Liu, L.-N. Ji, Z.-W. Mao, Polyhedron 30
(2011) 1953.
[6] (a) R. Vijayalakshmi, M. Kanthimathi, V. Subramanian, B.U. Nair, Biochim.
Biophys. Acta 1475 (2000) 157;
(b) S. Dey, S. Sarkar, H. Paul, E. Zangrando, P. Chattopadhyay, Polyhedron 29
(2010) 1583.
[7] B. Biswas, A. Pal, G. Ramakrishna, C.M. Reddy, F. Tuna, R. Ghosh, Polyhedron 30
(2011) 2032.
[8] H. Chowdhury, R. Ghosh, S.H. Rahaman, B.K. Ghosh, Polyhedron 26 (2007)
5023.
[9] SHELXTL 5.10, Bruker Analytical X-ray Instruments Inc., Karlsruche, Germany,
1997.
10
15
20
25
30
35
40
6
[complex] x10
Fig. 10. Plot of I0/I vs. [complex] for the titration of CT-DNA–EB system with 2 using
[10] L.J. Farrugia, J. Appl. Crystallogr. 30 (1997) 565.
[11] (a) K. Nakamoto, Infrared and Raman Spectra of Inorganic and Coordination
Compounds, Part B: Applications in Coordination, Organometallic, and
Bioinorganic Chemistry, John Wiley and Sons Inc., New York, 1997. p. 116;
(b) S. Barbara, Infrared Spectroscopy: Fundamentals and Applications, Wiley,
New York, 2004.
[12] S. Das, C.-H. Hung, S. Goswami, Inorg. Chem. 42 (2003) 5153.
[13] (a) Q.S. Li, P. Yang, H.F. Wang, M.L. Guo, J. Inorg. Biochem. 64 (1996) 181;
(b) C.Y. Zhou, J. Zhao, Y.B. Wu, C.X. Yin, P. Yang, J. Inorg. Biochem. 101 (2007)
10.
a
spectrofluorimeter; linear Stern–Volmer quenching constant (Ksv
)
for
2 = 1.49 ꢂ 104 (R = 0.995 for four points).
Stern–Volmer quenching constant and [complex] the concentration
of the quencher. From the slope of the regression line in the derived
plot of I0/I versus [complex] (Figs. 9 and 10), the Ksv values for 1 and
2 were found to be 1.92 ꢂ 104 (R = 0.996 for four points) and
1.49 ꢂ 104 (R = 0.995 for four points), respectively, indicating a
strong affinity of the complexes to CT-DNA.
[14] (a) A.M. Pyle, J.P. Rehmann, R. Meshoyrer, C.V. Kumar, N.J. Turro, J.K. Barton, J.
Am. Chem. Soc. 111 (1989) 3051;
(b) L. Fin, P.J. Yang, J. Inorg. Biochem. 68 (1997) 79.
[15] (a) R.F. Pasternack, E.J. Gibbs, J.J. Villafranca, Biochemistry 22 (1983) 2406;
(b) S. Mahadevan, M. Palaniyandavar, Inorg. Chem. 37 (1998) 693.
[16] (a) H.C. Hodges, M.A. Araujo, Inorg. Chem. 21 (1982) 3236;
(b) C.W. Lee, F.C. Anson, Inorg. Chem. 23 (1984) 837.
[17] R. Tamilarasan, D.R. McMillin, Inorg. Chem. 29 (1990) 2798.
[18] R. Indumathy, S. Radhika, M. Kanthimathi, T. Weyhermuller, B.U. Nair, J. Inorg.
Biochem. 101 (2007) 434.
4. Conclusion
Here in this work we have reported the synthesis and single
crystal X-ray structural characterisation of a new Cu(II) complex,
1, with a neutral Schiff base ligand. 1 and another complex 2,
which was reported very recently by our group [7], are found to
[19] D.L. Boger, B.E. Fink, S.R. Brunette, W.C. Tse, M.P. Hedrick, J. Am. Chem. Soc. 123
(2001) 5878.