Tridentate Schiff base coordinated trigonal bipyramidal / square pyramidal copper(II) complexes: Synthesis, crystal structure, DFT / TD-DFT calculation, catecholase activity and DNA binding

Article abstract of DOI:10.1016/j.molstruc.2019.03.098

Using tridentate O,N,O/N,N,O donor Schiff bases and 1,10-phenanthroline, five coordinated copper(II) complexes, {[Cu(L¹)(phen)][Cu(L¹)(phen)]?5H₂O}(1) and {[Cu(L²)(phen)](ClO₄)}(2) [H₂L

Full text of DOI:10.1016/j.molstruc.2019.03.098

Accepted Manuscript
Tridentate Schiff base coordinated trigonal bipyramidal / square pyramidal copper(II)
complexes: Synthesis, crystal structure, DFT / TD-DFT calculation, catecholase
activity and DNA binding
Apurba Bhunia, Pavel Vojtíšek, Valerio Bertolasi, Subal Chandra Manna
PII:
S0022-2860(19)30385-0
DOI:
https://doi.org/10.1016/j.molstruc.2019.03.098
MOLSTR 26367
Reference:
To appear in: Journal of Molecular Structure
Received Date: 11 October 2018
Revised Date: 1 March 2019
Accepted Date: 29 March 2019
Please cite this article as: A. Bhunia, P. Vojtíšek, V. Bertolasi, S. Chandra Manna, Tridentate Schiff base
coordinated trigonal bipyramidal / square pyramidal copper(II) complexes: Synthesis, crystal structure,
DFT / TD-DFT calculation, catecholase activity and DNA binding, Journal of Molecular Structure (2019),
doi: https://doi.org/10.1016/j.molstruc.2019.03.098.
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Graphical abstract
Tridentate Schiff base coordinated trigonal bipyramidal / square pyramidal copper(II)
complexes: Synthesis, crystal structure, DFT / TD-DFT calculation, catecholase activity
and DNA binding
Apurba Bhunia, Pavel Vojtíšek, Valerio Bertolasi, Subal Chandra Manna*
Using
tridentate
Schiff
bases
and
1,10-phenanthroline,
complexes
1
1
2
1
{
[Cu(L )(phen)][Cu(L )(phen)]·5H
2
4 2
O} (1) and {[Cu(L )(phen)](ClO )} (2) (H L = 3-[(2-
2
hydroxy-benzylidene)-amino]-propionic
acid,
HL
=
2-methoxy-6-[(3-methylamino-
propylimino)-methyl]-phenol, phen = 1,10-phenanthroline) have been synthesized and
structurally characterized. Complex 1 is a cocrystal with mononuclear trigonal bipyramidal and
square pyramidal geometries. Spectroscopic study reveals that both the complexes show
catecholase activity, and the complexes interact with the CT-DNA. Results of DFT and TD-
DFT calculations are used to explain the structures and electronic spectral properties of the
complexes.

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Tridentate Schiff base coordinated trigonal bipyramidal / square pyramidal copper(II)
complexes: Synthesis, crystal structure, DFT / TD-DFT calculation, catecholase activity
and DNA binding
a
b
c
,a
Apurba Bhunia, Pavel Vojtíšek, Valerio Bertolasi, Subal Chandra Manna*
a
Department of Chemistry and Chemical Technology, Vidyasagar University, Midnapore
7
21102, West Bengal, India, E-mail: scmanna@mail.vidyasagar.ac.in, Fax: (91) (03222)
75329.
2
b
Department of Inorganic Chemistry, Charles University in Prague, Hlavova 2030/8, 128 43
Prague 2, Czech Republic.
c
Dipartimento di Scienze Chimiche e Farmaceutiche, Centro di Strutturistica
Diffrattometrica, Università di Ferrara, Via L. Borsari, 46, 44100 Ferrara, Italy.
Abstract
Using tridentate O,N,O / N,N,O donor Schiff bases and 1,10-phenanthroline, five coordinated
1
1
copper(II)
complexes,
{[Cu(L )(phen)][Cu(L )(phen)]ꢀ5H O}(1)
and
2
2
1
2
{
[Cu(L )(phen)](ClO )}(2) [H L = 3-[(2-hydroxy-benzylidene)-amino]-propionic acid, HL
4
2
=
2-methoxy-6-[(3-methylamino-propylimino)-methyl]-phenol, phen = 1,10-phenanthroline]
have been synthesized and structurally characterized. Complex 1 is a co-crystal, where two
geometrically different (trigonal bipyramidal (TBP) and square pyramidal (SP)) complexes of
1
same compositions [Cu(L )(phen)] are within a unit cell. Complex 2 exhibits a trigonal
bipyramidal geometry and counter balanced by perchlorate anion. In solid state, complex 1
contains both SP and TBP geometries, but theoretical calculation reveals that in solution it
exists only in one form with SP geometry. DFT/TD-DFT calculations for the complexes were

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performed to explain the structures and electronic spectral properties of the complexes. Both
the complexes are active for catalytic oxidation of 3,5-di-tert-butylcatechol (3,5-DTBC) to
3
,5-di-tert-butylquinone (3,5-DTBQ) in presence of molecular oxygen and the calculated
-1
values of turnover numbers are 62±3 and 52±3 h for 1 and 2, respectively. Interactions of
complexes with calf thymus-DNA have been studied using fluorescence spectroscopic
4
techniques and the calculated values of binding constants are (2.20±0.06) × 10 and
4
-1
(
2.27±0.07) × 10 L mol for complexes 1 and 2, respectively.
_
__________________________________________________________________________
Keywords: Copper(II) complexes; Cocrystal; Crystal structure; DFT/TD-DFT calculation;
DNA binding.
_
__________________________________________________________________________
1
. Introduction
Chelating ligand based copper complexes are important for their potential applications in
catalysis and biological activities [1]. Due to versatile coordination number copper can easily
coordinate with the donor sites of organic ligands and form coordination complexes of
various geometries [2-3]. Use of flexidentate chelating ligand and chelating pyridinyl ligand
is an important strategy for designing mononuclear copper complexes. 1,10-phenanthroline is
an important chelating ligand and behaves as a potential σ-donor and π-acceptor ligand [4],
and due to extensive π character, it can form supramolecular connections with bio-molecules
with πꢀꢀꢀπ and CHꢀꢀꢀπ interactions.
Cocrystals are single phase crystalline materials composed of two or more different
molecules or ions in a stoichiometric ratio [5], and the cocrystals are important for their
interesting physical and chemical properties and potential applications as pharmaceuticals,
nonlinear optical materials and charge-transfer solids [6-7].

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Catechol oxidase is an enzyme in plant system which catalyzes the oxidation process of o-
diphenols to o-benzoquinones in presence of molecular oxygen. Active site of this
metaloprotein contains two copper(II) centers [8]. It is interesting to note that in aerobic
condition many copper(II)-Schiff base complexes mimic the catecholase activity [9].
The interaction of DNA with copper(II) complexes have been studied broadly in the field of
biology and medicinal chemistry [10]. The complexes can interact with DNA and hence
change the replication of DNA. Literature study show that copper complexes interact strongly
with DNA molecules [11]. Metal complexes can interact with DNA molecules through
covalently or non-covalently. Generally DNA bonded metal complexes are stabilized through
the weak interactions with the base pairs of DNA which is known as intercalation. In addition
to the interaction, the complexes may also bind with the DNA through groove binding mode
and with electrostatic interactions [12]. Literature survey reveals that the magnitude and the
mode of interaction of complexes with CT-DNA depend on the nuclearity and the geometry
of the complexes, and on the choice of chelating ligands. Studies of the interaction of CT-
DNA with new copper (II) complexes are important to get better understanding about the
kinetics of interaction of complexes with CT-DNA. In the present study we have used O,N,O
and N,N,O donor chelating ligands, 3-[(2-hydroxy-benzylidene)-amino]-propionic acid
1
2
(
H L ) and 2-methoxy-6-[(3-methylamino-propylimino)-methyl]-phenol (HL ), respectively,
2
1
1
and synthesized two mononuclear Cu(II) complexes {[Cu(L )(phen)][Cu(L )(phen)]ꢀ5H O}
2
2
(
1) and {[Cu(L )(phen)](ClO )}(2). DFT/TD-DFT calculations have been performed to
4
explain structure and electronic spectral properties of the complexes. Catecholase activity and
CT-DNA interactions studies have also been performed using spectroscopic techniques.

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2
. Experimental
2
.1. Materials
N-methyl-1,3-diaminopropane, 1,10-phenanthroline, calf thymus DNA, ethidium bromide,
and 3,5-di-tertbutylcatechol were purchased from Aldrich chemical company. All other
chemicals are of AR grade.
2
.2. Physical measurements
Elemental analyses were performed using a Perkin-Elmer 240C elemental analyzer. IR
spectra were recorded as KBr pellets on a Bruker Vector 22 FT IR spectrophotometer
–
1
operating from 400 to 4000 cm . Electronic absorption spectra were obtained with Shimadzu
UV-1601 UV-vis spectrophotometer at room temperature. Emission spectra were recorded on
Hitachi F-7000 spectrofluorimeter at room temperature. The fluorescence quantum yield [13]
was determined using phenol as a reference in water [refractive index (η), 1.333)] and
complexes inmethanol (η, 1.329). ESI mass spectra of complexes were determined using their
methanolic and aqueous solutions (Acq. method: Direct Infusion_HPLC.m, Stream name:
LC1, Acquisition SW Version: 6200 series TOF/6500 series Q-TOF B.08.00 (B8058.0),
QTOF Driver Version: 8.00.00, QTOF Firmware Version: 20.698, Tune Mass Range Max.:
3
200).
1
1
2
.3. Synthesis of {[Cu(L )(phen)][Cu(L )(phen)]·5H O} (1)
2
1
The tridentate Schiff base (H L ) was prepared by refluxing 2-hydroxybenzaldehyde (1
2
mmol, 0.122 g) and beta-alanine (1 mmol, 0.089 g) in methanol (15 mL) according to
literature method [14]. An aqueous solution (10 mL) of copper perchlorate hexahydrate (1
mmol, 0.370 g) was added to the methanolic solution of mixture of triethylamine (2 mmol,
1
0
.202 g) and H L (1 mmol, 0.193 g) under stirring condition. To this reaction mixture a
2

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methanolic solution (5 mL) of 1,10-phenanthroline (1 mmol, 0.180 g) was added drop wish
and resulting green color reaction mixture was stirred for 2 h and filtered. The filtrate was
kept in refrigerator for slow evaporation. After a few days green single crystals suitable for
X-ray diffraction were obtained from the filtrate. Yield 0.408 g (85%). Anal. Calcd for
C H Cu N O (959.93): C, 55.05; H, 4.62; N, 8.75 %. Found: C, 55.03; H, 4.61; N, 8.77
44
44
2
6
11
-1
(
%). IR (cm ): 3100-3600(br, vs), 2943(s), 2887(s), 1656(vs), 1637(vs), 1553(vs), 1468(w),
1
414(s), 1375(s), 1300(s), 1077(s), 880(s), 812(s), 634(s).
2
2
.4. Synthesis of {[Cu(L )(1,10-phen)](ClO )} (2)
4
2
The Schiff base HL was prepared by refluxing 2-hydroxy-3-methoxybenzaldehyde (1 mmol,
0
.152 g) and N-methyl-1,3-diaminopropane (1 mmol, 0.088 g) in methanol (15 mL)
according to literature method [14]. Complex 2 was synthesized adopting the same reaction
2
1
procedure as for 1 using HL (1 mmol, 0.222 g) instead of H L and here 1 mmol (0.101 g)
2
triethylamine used. Yield 0.4g (71 %). Anal. Calcd for C H CuN O Cl (564.47): C, 51.06;
2
4
25
4
6
-1
H, 4.46; N, 9.92 %. Found: C, 51.08; H, 4.49; N, 9.90 (%). IR (cm ): 2985(s), 2945(s),
2
8
886(s), 1638(vs), 1551(vs), 1542(vs), 1467(w), 1415(s), 1376(s), 1300(s), 1080(s), 881(s),
14(s), 637(s).
2
.5. Crystallographic data collection and refinement
Data collection of complex 1 was carried out by using a Nonius Kappa CCD diffractometer
with graphite monochromated Mo-Kα radiation, at room temperature. The data sets were
integrated with the Denzo-SMN package [15] and corrected for Lorentz, polarization and
absorption effects (SORTAV) [16]. The crystal data of complex 2 was collected on a Bruker
APEX CCD diffractometer using graphite monochromated Mo-Kα radiation (λ = 0.7107 Å)

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at 150 K [17]. The structure of the complexes were solved by direct methods SIR97 [18] and
refined by full-matrix least squares methods with SHEL-XTL [19] with all non-hydrogen
atoms anisotropically and both C-H and N-H hydrogens included on calculated positions,
riding on their carrier atoms. In the final Difference Fourier mapsof complex 1, ill-defined
regions of residual eletron density were found not localized close to the water Oxygens.
Accordingly, it was not possible to identify any hydrogen atom bonded to these Oxygens.
The final geometrical calculations and graphical manipulations were carried out with the
SHEL-XTL package [19]. All calculations were performed using SHELXL-97 [20] and
PARST [21] implemented in WINGX [22] system of programs. Crystal data and details of
refinements are given in Table 1. ORTEP views are shown in Figs. 1 and 2.
2
.6. Theory and computational methods
Theoretical calculations were performed using the Gaussian 09 software package [23]. For
the calculation 6-31G (d-p) basis set was used for the optimization of all elements, except
copper atoms, for which the Los Alamos effective core potentials plus the Double Zeta
(
LanL2DZ) [24] basis set was employed. The geometric structures of the complexes in the
ground state (doublet) were fully optimized by using the Becke’s three-parameter hybrid
exchange functional and the Lee-Yang-Parr non-local correlation functional (B3LYP) [25].
Electronic excitations based on B3LYP functional were obtained with the time-dependent
density functional theory (TD-DFT) [26] in methanol using the conductor-like polarizable
continuum model (CPCM) [27]. GaussSum [28] was used to calculate the fractional
contributions of various groups to each molecular orbital.
2
.7. DNA binding studies

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Stock solutions of complexes and CT-DNA were prepared in HEPES buffer solution (pH
7
.2). The competitive binding nature of ethidium bromide (EtBr) and complexes with CT-
DNA were investigated adopting fluorometric method, using aqueous solution of CT-DNA
bounded EtBr in HEPES buffer at room temperature. In presence of CT-DNA, ethidium
bromide (EtBr) exhibits fluorescence enhancement due to its intercalative binding to CT-
DNA. Competitive binding of complexes with CT-DNA results fluorescence quenching due
to displacement of EtBr from CT-DNA molecules. The fluorescence intensities at 600 nm
(λex, 500 nm) of CT-DNA bounded EtBr with increasing concentration of complexes were
recorded. The quenching constants (Stern-Volmer constant, K ) were calculated using Stern-
sv
Volmer equation [29]. Concentration of CT-DNA was determined [30] by measuring the
absorbance (A) of CT-DNA solution at 260 nm and applying Lambert-Beer law [A = єcl,
where A is the absorbance at 260 nm (characteristic band of CT-DNA), є is the molar
-1
-1
extinction coefficient 6600 L mol cm per nucleotide, l is the path length of the beam of
light through the sample (aqueous solution of CT-DNA), c is the molar concentration of CT-
DNA.
3
. Results and discussion
3
.1. Crystal structure description
Solid state structure analysis of 1 and 2 show that both the compounds are five coordinated,
mononuclear Cu(II) complexes. Complex 1 contains two geometrically different molecules
and five lattice water molecules in the asymmetric unit. Molecular structure of complex 1 is
shown in Fig.1. In complex 1 there are two five coordinated complex units (unit-a and unit-
b). Complex 2 is a cationic complex and counter balanced by perchlorate anion (Fig. 2). The
trigonality τ parameter [31] calculation indicate that in 1, the unit-a possesses distorted
5
square pyramidal geometry (τ , 0.440), whereas unit-b possesses trigonal bipyramidal
5

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geometry (τ ,0.683) (Table 2). Calculated value of τ for 2 is 0.732 indicating that the Cu(II)
5
5
centre possesses distorted trigonal bipyramidal geometry (Table 3).
In unit-a of 1, the N(2A) atom occupy the apical position with Cu(1A)-N(2A) bond
distance 2.251Å, and O(1A), O(2A), N(1A), N(3A) atoms form basal plane. Whereas in unit-
b O(1B), O(2B), N(3B) atoms form trigonal plane, and N(1B) and N(2B) atoms occupy
apical position with N(1B)-Cu(1B)-N(2B) bond angle as 175.04(15)° (Table 2 and Fig. 3).
Packing diagram of 1 shows that the alternate arrangement of unit-a and unit-b, and form 1D
supramolecular chain through three different types of πꢀꢀꢀπ interactions [Cg(7)ꢀꢀꢀCg(7)=
3
.506Å, Cg(14)ꢀꢀꢀCg(15)= 3.672Å, Cg(14)ꢀꢀꢀCg(5)= 3.606Å] (Fig. 4). The 1D supramolecular
chains are again linked through C-Hꢀꢀꢀπ interactions [H(20B)ꢀꢀꢀCg(6)= 2.707Å] and form 2D
supramolecular sheet like structure (Fig. 1S and Table 1S).
Complex 2 exhibits trigonal bipyramidal geometry, where phenolic oxygen (O1), one
Schiff base nitrogen (N2) and one nitrogen from phen (N4) form trigonal plane. The Schiff
base nitrogen (N1) and nitrogen from phen (N3) placed at the opposite sides of the plane. In
the trigonal plane the coordination bond distances fall in the ranges 1.929(13)Å-2.196(15)Å
and N(1)-Cu(1)-N(3) is 176.24(7)° (Table 3). Packing diagram of 2 shows 2D
supramolecular structure formed by πꢀꢀꢀπ [Cg(4)ꢀꢀꢀCg(5)= 3.703 Å] and C-Hꢀꢀꢀπ
[
H(9B)ꢀꢀꢀCg(5)= 3.643Å] interactions (Fig. 5 and Table 2S).
3
.2. ESI mass spectrometry
The ESI mass spectra of complexes were recorded in methanolic and aqueous solutions. For
complex 1 the methanolic solution shows peak at m/z = 434.9404, whereas aqueous solution
shows peak at m/z = 434.9347. These peaks corresponds to the presence of species
1
ꢀ+
[
Cu(L )(1,10-phen)] (calc. m/z = 434.93) (Figs. 2S and 3S). For complex 2, peaks are at
4
64.95 and 465.0014 in methanolic and aqueous medium, respectively, corresponding to the

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2
+
complex cation [Cu(L )(1,10-phen)] (calc. m/z = 465.02). These observations clearly
indicate that the complexes are stable in both methanol and water medium.
3
.3. DFT / TD-DFT computations
Structure of the complexes were fully optimized at the B3LYP level in the ground state using
LanL2DZ basic set and the optimized structures are depicted in Figs. 6S and 7S for 1 and 2,
respectively. A comparison of calculated bond lengths and angles with X-ray crystal
structures shows sufficient agreement (Table 2 and 3). The orbital diagrams along with their
energies and contributions from the ligands and metal of 1 and 2 are given in Figs 8S and 9S.
HOMO and LUMO of complexes are mostly contributed from copper and phenanthroline
respectively (Fig. 6a). HOMO-LUMO energy differences are 1.15 eV and 1.10 eV for 1 and
2
, respectively indicating that 1 is kinetically more stable in comparison to 2. A comparative
MOs energy level diagrams are depicted in Fig. 6b.
In the solid state structure 1 possesses two units with square pyramidal (unit-a) and trigonal
bipyramidal (unit-b) geometries. Calculated energies of unit-a and unit-b are -
3
9027.958191983 eV and -39027.867335077 eV, respectively. It is interesting to note that
when both unit-a and unit-b are optimized in methanol adopting CPCM model, both the
units finally maintain square pyramidal geometry, which corroborates the higher stability of
square pyramidal geometry.
TD-DFT calculations of complexes in methanol using conductor-like polarizable continuum
model (CPCM) were performed. Theoretically possible spin-allowed electronic transitions
with their assignment are listed in Tables 3S and 4S, for 1 and 2, respectively. The TD-DFT
results show that [HOMO-7(α) →LUMO+1(α) (20%), HOMO-7(β) →LUMO+2(β) (22%)]
and [HOMO-6(β) →LUMO(β) (10%), HOMO-2(β) →LUMO(β) (12%), HOMO(β)
→
LUMO(β) (44%)] are the possible highest energy electronic transitions and lowest energy
electronic transitions for 1. For 2, [HOMO-5(α) →LUMO+2(α) (31%)] and [HOMO-4(β)

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→
LUMO(β)(16%), HOMO(β) → LUMO(β)(62%)] are possible highest and lowest energy
electronic transitions, respectively. For 1, the experimental electronic transition at 267 nm is
assigned as combination of intraligand charge transition in phen [HOMO-8(α)
§
1
→
LUMO+1(α) (30%), ILCT ] and interligand charge transfer transition from L to phen
Γ
[
HOMO-6(α) →LUMO+1(α) (16%), IELCT ] (Table 4, Fig. 10S). For 2, electronic transition
2
at 260 nm is assigned as ligand to metal charge transfer transition from L to copper [HOMO-
δ
6
(β) → LUMO (β) (17%), LMCT ] (Table 4, Fig. 11S).
3
.4. Catechol oxidase studies of complexes
3
,5-di-tertbutylcatechol (3,5-DTBC) was used as model substrate to examine the catecholase
activity of the complexes at room temperature [32]. Catalytic amount of methanolic solution
−
4
-2
of (1 × 10 M) complexes were added to methanolic solution of 3,5-DTBC (1 × 10 M) and
the progress of the reaction was determined by recording the absorbance at 400 nm
(
characteristic absorption band of 3,5-di-tertbutyl quinone). The absorbance of complex-
substrate mixture gradually increases upon addition of complexes to the substrate (Figs. 7 and
2S). The rate constants for the formation of 3,5-di-tertbutyl quinone were obtained using the
equation ln[A /(A −A )] = kt where A and A are the absorbance of 3,5-di-tertbutyl quinone
1
∞
∞
t
∞
t
at time t = ∞ and t = t, respectively [33]. Calculated values of rate constants are 1.2±0.02 ×
-2
-1
-2
-1
1
0 min and 1.1±0.01 × 10 min for 1 and 2, respectively (Fig. 13S).
To determine the dependence of rate of reaction on substrate concentration same experiment
-3
-3
were carried out varying the substrate concentration from 1 × 10 M to 10 × 10 M. The
reaction shows first order dependence at low concentration of substrate, but at higher
concentration the saturation kinetics was observed (Fig. 8). As the catalytic reactions follow
saturation kinetics, Michaelis–Menten kinetic approach has been used to evaluate kinetic
-1
parameters [34]. Calculated values of turnover number (K ) are 62±3 and 52±3 h ,
cat

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respectively (Table 5). Complexes 1 and 2 show comparable catecholase activity with the
reported Cu(II) complexes (Table 5).
3
.5. DNA binding studies
Interactions of CT-DNA with metal complexes have been studied by monitoring the emission
intensity of CT-DNA bounded ethidium bromide (EtBr). Emission intensity of ethidium
bromide (EtBr) enhanced significantly in presence of CT-DNA due to the strong intercalation
of EtBr with DNA [35]. On excitation at 500 nm, EtBr and CT-DNA mixture shows emission
at 600 nm. Addition of a compound which is capable to interact with CT-DNA, results the
quenching of fluorescence intensity. Upon gradual addition of 5µL 1 mM solution of
complexes to the 2 mL CT-DNA bounded EtBr solution (mixture of 8.7 µM CT-DNA
solution and 12 µM EtBr solution) results the reduction of fluorescence intensity of 600 nm
band (Figs. 9 and 14S). Reduction of emission intensity clearly indicates that complexes 1
and 2 displaced the EtBr molecules from the DNA binding sites [36]. The calculated values
4
4
-1
of binding constants (K ) are (2.20±0.06) × 10 and (2.27±0.07) × 10 L mol for complexes
sv
1
and 2, respectively (Table 6). A comparison of binding constants for reported Cu(II)
complexes and shown in Table 6 and from this table it is clear that the complexes 1 and 2
have comparable interaction abilities with those of reported Cu(II) complexes.
4
. Conclusion
In the present contribution we report synthesis, crystal structure, DFT calculation, catecholase
activity and DNA binding studies of two five coordinated SP /TBP copper(II) complexes.
1
Use of chelating H L and phen ligands results complex 1, where mononuclear copper(II)
2
complexes of SP and TBP geometries are within the same unit cell. On the other hand use of
2
HL and phen results complex 2 of TBP geometry. Theoretical calculation reveals that in
between SP (unit-a) and TBP (unit-b) units in 1, the SP unit is energetically more stable. The

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optimization of geometries of unit-a and unit-b adopting CPCM model (in methanol) results
SP geometries for both the units, which corroborates with less energetic conformation of five
coordinate SP geometry in 1. On the other hand DFT calculation reveals that 2 maintains its
TBP geometry in its methanolic solution also. The results of TD-DFT calculation have been
used to explain the structure and electronic spectral properties of the complexes. UV-vis
spectral study indicates that both the complexes are active for catalytic oxidation of 3,5-
DTBC to 3,5-DTBQ. Fluorescence spectroscopic studies evidence that both complexes
interact with CT-DNA.
Acknowledgements
The authors gratefully acknowledge the financial assistance given by the CSIR, Government
of India, to Dr. Subal Chandra Manna (project no. 01 (2743)/13/EMR‐II). Authors thank
UGC‐SAP, DST‐FIST New Delhi, USIC (VU) and Vidyasagar University for
infrastructural facilities.
Supplementary information
Crystallographic data have been deposited at the Cambridge Crystallographic Data Centre
and allocated the deposition numbers are CCDC 1847953 and 1847954. These data can be
obtained free of charge via www.ccdc.cam.ac.uk/conts/retrieving.html or on application to
CCDC, Union Road, Cambridge, CB2 1EZ, UK [fax: (+44)1223-336033, e-mail:
deposit@ccdc.cam.ac.uk].
X-ray crystallographic data, electronic absorption spectra, emission spectra, IR spectra, ESI
mass spectra and results of DFT calculation are provided as supplementary material.

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Table 1. Crystal data and details of structures refinement for complexes 1 and 2.
Complex
1
2
Empirical formula
C H Cu N O
C H CuN O Cl
4
4
44
2
6
11
24 25
4
6
–
1
Formula mass, g mol
Crystal system
959.93
Triclinic
P-1
564.47
Monoclinic
Space group
a, Å
P21/n
12.6179(6)
12.6487(5)
14.6636(5)
79.457(3)
86.278(2)
68.199(2)
2
9.9833(3)
18.2146(6)
13.7179(5)
90
b, Å
c, Å
α, deg
β, deg
γ, deg
Z
108.590(1)
90
4
3
V, Å
2136.24(16)
1.477
2364.34(14)
1.586
–
3
D(calcd), g cm
–
1
µ(Mo-Ka), mm
F(000)
1.064
1.087
972
1164
Theta range, deg
No. of collected data
No. of unique data
Rint
2.2, 27.0
27412
1.9, 27.5
20194
9265
5424
0.091
0.025
h,k,lmax
16, 16, 18
6493
12, 22, 17
4518
Observed reflections
[
I> 2σ(I)]
2
Goodness of fit (F )
1.065
568
1.047
327
Parameters refined
[
a]
R1, wR2 (all data)
Residuals, e Å
0.0632, 0.1805
-0.79, 0.76
0.0312, 0.0828
-0.36, 0.41
–
3
[a]
2
2
2
2
2 2 ½
R1(Fo) = Σ  Fo – Fc  / Σ Fo , wR2(Fo ) = [Σw (Fo – Fc ) / Σw (Fo ) ]

ACCEPTED MANUSCRIPT
α
Table 2. Experimental and calculated coordination bond lengths (Å) and angles (°) for 1.
Unit-a
Cu(1A)-O(1A)
Cu(1A)-O(2A)
Cu(1A)-N(1A)
Cu(1A)-N(2A)
Cu(1A)-N(3A)
Exp
Unit-b
Cu(1B)-O(1B)
Cu(1B)-O(2B)
Cu(1B)-N(1B)
Cu(1B)-N(2B)
Cu(1B)-N(3B)
Exp
Calcd
1.974
2.017
1.978
2.313
2.052
1.933(2)
1.981(4)
1.938(3)
2.251(4)
2.020(3)
1.936(3)
2.145(3)
1.947(4)
2.000(3)
2.118(3)
O(1A)-Cu(1A)-O(2A) 149.26(13) O(1B)-Cu(1B)-O(2B) 112.34(12) 153.77
O(1A)-Cu(1A)-N(1A) 93.76(13) O(1B)-Cu(1B)-N(1B) 93.21(14) 92.37
O(1A)-Cu(1A)-N(2A) 106.41(13) O(1B)-Cu(1B)-N(2B) 91.03(14) 104.56
O(1A)-Cu(1A)-N(3A) 90.54(13) O(1B)-Cu(1B)-N(3B) 134.01(14) 88.28
O(2A)-Cu(1A)-N(1A) 91.23(14) O(2B)-Cu(1B)-N(1B) 88.76(13) 92.41
O(2A)-Cu(1A)-N(2A) 102.53(15) O(2B)-Cu(1B)-N(2B) 92.00(13) 99.75
O(2A)-Cu(1A)-N(3A) 85.30(14) O(2B)-Cu(1B)-N(3B) 113.05(13) 87.34
N(1A)-Cu(1A)-N(2A) 100.01(14) N(1B)-Cu(1B)-N(2B) 175.04(15) 101.18
N(1A)-Cu(1A)-N(3A) 175.69(15) N(1B)-Cu(1B)-N(3B) 94.78(14) 178.95
N(2A)-Cu(1A)-N(3A) 78.31(13) N(2B)-Cu(1B)-N(3B) 80.41(14) 77.85
τ5 parameter
Using conductor-like polarizable continuum model (CPCM) in methanol; basis set,
LanL2DZ; B3LYP functional.
0.440
0.683
0.419
α

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α
Table 3. Experimental and calculated coordination bond lengths (Å) and angles (°) for 2.
Exp
Calcd
Cu(1)-O(1)
Cu(1)-N(1)
Cu(1)-N(2)
Cu(1)-N(3)
Cu(1)-N(4)
1.929(13) 1.985
1.952(17) 1.995
2.127(17) 2.125
2.029(16) 2.072
2.196(15) 2.286
O(1)-Cu(1)-N(1) 92.73(6)
O(1)-Cu(1)-N(2) 129.66(6) 141.88
O(1)-Cu(1)-N(3) 88.13(6) 87.54
O(1)-Cu(1)-N(4) 132.28(6) 108.4
N(1)-Cu(1)-N(2) 93.81(7) 92.60
N(1)-Cu(1)-N(3) 176.24(7) 177.03
92.27
N(1)-Cu(1)-N(4) 98.01(6)
N(2)-Cu(1)-N(3) 88.45(6)
N(2)-Cu(1)-N(4) 95.95(6)
N(3)-Cu(1)-N(4) 78.75(6)
99.32
89.35
107.98
77.93
τ5 parameter
0.732
0.585
α
Using conductor-like polarizable continuum model (CPCM) in methanol; basis set,
LanL2DZ; B3LYP functional.
α
Table 4. Selected UV-Vis energy transition at the TD-DFT /B3LYP level for 1 and 2 in
methanol.
Complex λexp (nm),
b
λ (nm),
ε
Oscillator
cal (M cm ) strength
267.08, 29615 0.1039
Key transition
Character
cal
-1
-1
-1
-1
εexp (M cm )
266, 8.57×10
4
§
1
HOMO-8(α) →LUMO+1(α) (30%), ILCT
Γ
HOMO-6(α) →LUMO+1(α) (16%) IELCT
§
2
67.45, 29667 0.1663
263, 6.97 × 10 260.51, 58054 0.0289
65.34, 53712 0.0804
HOMO-8(α) →LUMO+1(α) (17%) ILCT
4
δ
2
HOMO-6(β) →LUMO (β) (17%)
LMCT
§
2
HOMO-4(α) →LUMO+1(α) (29%), ILCT
§
HOMO-5(β) →LUMO+2(β) (27%) ILCT
α
Using conductor-like polarizable continuum model (CPCM) in methanol; basis set,
LanL2DZ.

ACCEPTED MANUSCRIPT
b
§
Γ
1
ILCT = Intra ligand charge transfer of phen, IELCT = Inter ligand charge transfer from L
δ
2
to phen, LMCT = Charge transfer transition from L to copper.
Table 5. Kinetic parameters for the oxidation of 3,5-DTBC catalyzed by Cu(II) complexes.
Complex
Vmax
Fitting
error
K (M)
Fitting error
Kcat
Fitting
error
± 3
ref
m
–
1
-1
(
M min )
(h )
-
5
-5
-5
-3
-3
1
2
3.4 × 10
± 0.4 × 10
2.4 × 10
± 0.002 × 10
± 0.002 × 10
62
This
work
This
-
5
-3
-3
2.8 × 10
± 0.5 × 10
2.3 × 10
52
± 3
work
[9(a)]
[9(a)]
[9(b)]
[9(c)]
-
6
5
−3
[
Cu(sal-ppzH)Cl2]
9.85 × 10
2.38 × 10
-
5.3 × 10
11.82
28.80
58.68
28.44
-
−3
[Cu(hyap-ppzH)Cl2]
4.2 × 10
−
3
Cu(H LDA)(ClO )](ClO )
3.5 × 10
7.9 × 10
2
4
4
-5
-5
-6
-4
-4
-4
[
(
[
Cu (H -bbppnol)-
1.14 × 10
2
2
µ-OAc)(H O) ]Cl ‚2H O
2
2
2
2
Cu (Hbtppnol)(µ-
1.14 × 10
9.5 × 10
8.6 × 10
28.08
[9(c)]
2
OAc)](ClO4)
[
[
(
[
(
[
[
[
Cu (P1-O-)(OAc-)](ClO ) 4.02 × 10
10.08
90
[9(c)]
[9(d)]
2
4 2
1
-5
-3
Cu (L )(ꢁ-OAc)]-
3.70 × 10
3.47 × 10
9.44 × 10
2
ClO ) ·(CH ) CHOH
4
2
3 2
2
-5
-3
Cu (L )-(ꢁ-OAc)]-
7.44 × 10
183.6
[9(d)]
2
ClO )·H2O·(CH ) CHOH
4
3 2
3
2+
-5
-4
-4
-4
-3
-3
Cu (L )(ꢁ−OAc)]
1.14 × 10
1.56 × 10
3.89 × 10
9.50 × 10
3.32 × 10
4.60 × 10
28.08
93.6
[9(d)]
[9(e)]
[9(e)]
2
4
Cu L (ClO4) ]
2
2
4
Cu L (OH)]ClO
233.4
2
4
Hsal-ppz and Hyap-ppz are derived by reacting 1-(2-aminoethyl) piperazine with
salicylaldehyde and 2-hydroxyacetophenone, respectively. H LDA = N,N′-[bis-(2-hydroxy-3-
2
formyl-5-methylbenzyl)(dimethyl)]-ethylenediamine,
H bbppnol=
3
N,N′-bis(2-
hydroxybenzyl)-N,N′-bis- (pyridylmethyl)]-2-hydroxy-1,3-propanediamine, H2btppnol= N-
(2-hydroxybenzyl)-N,N′,N′-tris(2-pyridylmethyl)-1,3-diaminopropan2-ol,
P1-OH=
1,3-
1
bis[bis(2-pyridylmethyl)amino]propanolate, L =
N′,N′, N-tris(2-pyridylmethyl)-N-(2-
2
hydroxy-3,5-di-tert-butylbenzyl)- 1,3-propanediamin-2-ol, L = N′,N′-bis(2-pyridylmethyl)-
3
N,N-(2-hydroxybenzyl)(2-hydroxy-3,5-di-tert-butylbenzyl)- 1,3-propanediamin-2-ol, L = N-
4
(2-hydroxybenzyl)-N′,N′,N-tris(2-pyridylmethyl)-1,3-propanediamin-2-ol,
HL =
2-[[2-
(diethylamino)-ethylamino]methyl]phenol.

ACCEPTED MANUSCRIPT
Table 6. Kinetic parameter for the interactions of Cu(II) complexes with CT-DNA.
-1
Complex
K (L mol )
Fitting error
ref
sv
4
4
1
2
2.20 × 10
± 0.06 × 10
This work
This work
[11(a)]
[11(a)]
[11(b)]
[11(c)]
[11(d)]
[11(d)]
[11(d)]
[11(e)]
[11(e)]
[11(e)]
[11(e)]
4
4
2.27 × 10
± 0.07 × 10
1
5
[
Cu(L )(pa)]
1.40 × 10
1
5
[
Cu(L )(mb)]
1.99 × 10
2
5
{
[Cu (L ) (fum)](H O)(MeOH)}
1.71 × 10
2
2
2
n
3
4
[
[
[
[
[
[
[
[
Cu (ꢁ-L ) (ꢁ
-O CH)](OH) H O 4.73 × 10
1,1,3,3 2 6 2
4
2
4
4
4
4
Cu(L )(phen)(NO )]
6.12 ×10
3.80 ×10
4.68 ×10
3
4
Cu(L )(bpy)(NO )]
3
4
Cu(L )(DACH)(NO )]
3
2
+
5
Cu(bba)(bpy))]
1.7 × 10
3.6 × 10
2
+
5
Cu(bba)(phen)]
Cu(bba)(5,6-dmp)]
2
+
6
1.08 × 10
2
+
5
Cu(bba)(dpq)]
5.1 × 10
1
HL = o-{(3-morpholinopropylimino)methyl}phenol, pa= 3-phenylacrylate, mb= p-
2
methylbenzoate, fum= fumarate, Schiff base (HL ) derived from the condensation reaction of
3
2
-amino-1-butanol and salicylaldehyde. H L = 1,3-bis [3-aza-3-(1-methyl-3-oxobut-1-
3
4
enyl)prop-3-en-1-yl]-2-(2-hydroxyphenyl)-1,3-imidazolidine, L = 3-formylchromone, phen=
1
,10-phenanthroline, bpy= 2,2′-bipyridine, DACH= 1R,2R-DACH, bba= N,N-
bis(benzimidazol-2-ylmethyl)-amine, 5,6-dmp= 5,6-dimethyl-1,10-phenanthroline, dpq=
dipyrido[3,2-d:2,3-f ] quinoxaline.

ACCEPTED MANUSCRIPT
Figure captions
Fig. 1. ORTEP view of complex 1 showing the thermal ellipsoids at 30% probability level.
Fig. 2. ORTEP view of complex 2 showing the thermal ellipsoids at 30% probability level.
Fig. 3. Square pyramidal and trigonal bipyramidal coordination arrangement Cu(II) centers in
complex 1.
Fig. 4. 1D Supramolecular structure of complex 1.
Fig. 5. 2D Supramolecular structure of complex 2.
Fig. 6. (a) Surface plots of HOMO and LUMO for complexes 1 and 2 (with energies and
compositions). (b) Molecular orbital energy level diagrams for 1 and 2.
Fig. 7. Absorbance vs time plot for the oxidation of 3,5-di-tert-butylquinone (3,5-DTBQ)
catalyzed by complex 1.
The spectra were recorded at an interval of 5 min.
Fig. 8. (a) Plots of rate vs substrate concentration, and (b) Lineweaver–Burk plots for
complexes 1 and 2.
Fig. 9. Fluorescence quenching curves of EtBr bounded CT-DNA upon gradual addition of 5
µL 1 mM solution of 1 to 2 mL aqueous solution of EtBr-CT-DNA (mixture of 8.7 µM CT-
DNA solution and 12 µM EtBr solution) (inset: Stern-Volmer plot for fluorescence titration).

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Fig.1
Fig.2

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Fig.3
Fig.4

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Fig. 5
Fig. 6

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Fig. 7
Fig. 8

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Fig. 9

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Highlights
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
Two five coordinated copper(II) complexes have been synthesized and characterized.
Complexes form supramolecular structures with CH…π interactions.
DFT/TD-DFT calculations have been performed.
Complexes show catecholase activity.
Spectroscopic studies reveal interaction of complexes with DNA.