Two new hetero-dinuclear nickel(II)/zinc(II) complexes with compartmental Schiff bases: Synthesis, characterization and self assembly

Article abstract of DOI:10.1016/j.poly.2016.03.026

Two compartmental Schiff bases, H₂L¹ [N,N′-bis(3-methoxysalicylidene)propane-1,3-diamine] and H₂L² [N,N′-bis(3-methoxysalicylidene)-2,2-dimethylpropane-1,3-diamine], have been utilized to prepare two hetero-dinu

Full text of DOI:10.1016/j.poly.2016.03.026

Polyhedron 112 (2016) 109–117
Contents lists available at ScienceDirect
Polyhedron
journal homepage: www.elsevier.com/locate/poly
Two new hetero-dinuclear nickel(II)/zinc(II) complexes with
compartmental Schiff bases: Synthesis, characterization and self
assembly
⇑
Anik Bhattacharyya, Sourav Roy, Jhonti Chakraborty, Shouvik Chattopadhyay
Department of Chemistry, Inorganic Section, Jadavpur University, Kolkata 700032, India
a r t i c l e i n f o
a b s t r a c t
1
0
2
Article history:
2 2
Two compartmental Schiff bases, H L [N,N -bis(3-methoxysalicylidene)propane-1,3-diamine] and H L
Received 12 February 2016
Accepted 15 March 2016
Available online 26 April 2016
0
[
N,N -bis(3-methoxysalicylidene)-2,2-dimethylpropane-1,3-diamine], have been utilized to prepare
two hetero-dinuclear nickel(II)/zinc(II) complexes, [(DMSO) NiL Zn(NCS) ] (1) and [(DMSO) NiL Zn
2 2 2
NCS) ] (2). Both complexes have been characterized by elemental and spectral analysis. Single crystal
2
1
2
(
X-ray diffraction analysis has confirmed their structures. The key step in the synthesis of these complexes
is to use nickel(II) thiocyanate tetrahydrate and zinc(II) acetate dihydrate in a single pot. In each complex,
Keywords:
Zinc(II)
Nickel(II)
Hetero-dinuclear
Compartmental Schiff base
Photoluminescence
octahedral nickel(II) is placed in the inner N
in the axial sites) and tetrahedral zinc(II) is placed in the outer O
2
O
2
compartment (with DMSO molecules being coordinated
compartment of the Schiff bases.
4
Supramolecular interactions in both complexes were explored. Both complexes show photoluminescence
in DMSO solution at room temperature upon the irradiation of ultraviolet light. The life times of the
excited states are in the range of 4–5 ns.
Ó 2016 Elsevier Ltd. All rights reserved.
1
. Introduction
Synthesis and characterization of di and polynuclear 3d metal
[17–20]. Several homo and hetero-di and polynuclear transition
and non-transition metal complexes have been prepared with
these ligands [21–24]. Many 3d/4f complexes with these compart-
mental ligands have been found to show ferromagnetic properties
[25,26]. However, phenoxo bridged hetero-dinuclear zinc(II)/nickel
(II) complexes did not receive such high attention probably
because of the lack of magnetic exchange interaction in them. In
this context, it is noteworthy that the importance of the d10 metal
complexes lies in their strong luminescence properties and poten-
tial applications in electronic and optoelectronic devices [27,28].
In the present work, we have used two compartmental Schiff
bases to prepare two hetero-dinuclear nickel(II)/zinc(II) complexes
complexes have attracted the attentions of material scientist since
long for their potential uses in non-linear optics, biological model-
ing application, magnetism, catalysis, opto-electronic devices,
molecular architectures etc [1–6]. Nickel(II) have been extensively
used in preparing such complexes probably because its flexibility
in attending varieties of geometries viz. square planar, square
pyramidal, trigonal bipyramidal, octahedral etc with coordination
numbers ranging from 4 to 6 [7–10]. On the other hand, zinc is
the second most abundant 3d metal in the human body and is an
essential cofactor in many biological processes [11,12]. Zinc(II)
with d electronic configuration may also adopt varieties of
geometries with no CFSE in any geometry [13,14].
Synthetic inorganic chemists have prepared varieties of di and
polynuclear transition metal complexes with well-known salen
type Schiff base ligands utilizing the bridging ability of their
phenoxy oxygen atoms [15,16]. Salen type ligands prepared using
2
with NiO Zn cores. These are the first examples of any hetero-din-
1
0
uclear nickel(II)/zinc(II) complexes with salen type Schiff bases.
Both complexes exhibit photoluminescence in DMSO medium with
lifetime 4–5 ns. Herein, we would like to report the synthesis, char-
acterization, X-ray crystal structure and supramolecular architec-
ture of two new hetero-dinuclear nickel(II)/zinc(II) complexes.
3
-methoxysalicyalaldehyde instead of salicylaldehyde itself is
more advantageous because they have inner N and outer O
cores and may be considered as compartmental Schiff bases
2. Experimental
2
O
2
4
Nickel(II) thiocyanate tetrahydrate was prepared in laboratory
following the literature method [29]. All other materials were
commercially available, reagent grade and used as purchased from
Sigma-Aldrich without further purification.
⇑
Corresponding author. Tel.: +91 33 2457 2941.
E-mail address: shouvik.chem@gmail.com (S. Chattopadhyay).
http://dx.doi.org/10.1016/j.poly.2016.03.026
277-5387/Ó 2016 Elsevier Ltd. All rights reserved.
0

1
10
A. Bhattacharyya et al. / Polyhedron 112 (2016) 109–117
2.1. Synthesis
Table 1
Crystal data and refinement details of complexes 1 and 2.
2
2
1
.1.1. Synthesis of ligands
Complex
1
2
1
0
.1.1.1. Synthesis of H
2
L [N,N -bis(3-methoxysalicylidene)propane-
Formula
Formula weight
T (K)
Crystal system
Space group
a (Å)
C
25
H
32
4
N NiO
6 4
S Zn
C
27 36 4 6 4
H N NiO S Zn
,3-diamine]. A methanol solution (10 ml) of 3-methoxysalicy-
736.91
100
triclinic
764.96
100
triclinic
laldehyde (304 mg, 2 mmol) and 1,3-diaminopropane (0.13 ml,
mmol) was refluxed for ca. 1 h. The ligand was not isolated and
used directly for the synthesis of the complex 1.
1
P1ꢀ
P1ꢀ
12.6431(4)
15.8433(5)
16.0431(5)
85.146(2)
89.705(2)
87.339(2)
4
1.530
1.643
1520
10.1450(3)
11.1743(3)
16.8051(4)
74.984(1)
74.933(1)
74.006(1)
2
1.467
1.520
792
b (Å)
c (Å)
2
0
2.1.1.2. Synthesis of
H
2
L
[N,N -bis(3-methoxysalicylidene)-2,2-
a
(°)
dimethylpropane-1,3-diamine]. It was prepared in a similar method
as that of H
1
b (°)
2
L
except that 2,2-dimethyl-1,3-diaminopropane
c
(°)
(
0.12 ml, 1 mmol) was used instead of 1,3-diaminopropane. The
Z
Dcalc(g cmꢁ3)
ligand was not isolated and used directly for the synthesis of the
complex 2.
ꢁ
1
l
(mm
)
F(000)
Total reflections
48633
12564
9195
739
0.052
26483
6634
4692
398
0.032
2
2
.1.2. Synthesis of complexes
.1.2.1. Synthesis of [(DMSO)
Unique reflections
Observed data [I > 2
No. of parameters
1
2
NiL Zn(NCS)
2
] (1). A methanol (10 ml)
r(I)]
solution of zinc(II) acetate dihydrate (219 mg, 1 mmol) was added
to the methanol solution (20 ml) of H L and the resulting solution
2
1
R
R
R
int
1
, wR
, wR
2
2
(all data)
[I > 2 (I)]
0.0634, 0.1100
0.0418, 0.0998
0.0781, 0.1538
0.0544, 0.1399
was stirred for 15 min. A methanol (10 ml) solution of nickel(II)
thiocyanate tetrahydrate (250 mg, 1 mmol) was then added to it.
The stirring was continued for about 2 h. Few drops of DMSO
was added and the resulting solution was kept for crystallization.
Single crystals, suitable for X-ray diffraction, were obtained after
1
r
Table 2
Selected bond lengths (Å) for complexes 1 (subunit A) and 2.
3
–4 days on slow evaporation of the solution in open atmosphere.
Yield: 552 mg, 75%. Anal. Calc. for NiO Zn
FW = 736.87): C, 40.75; H, 4.38; N, 7.60. Found: C, 40.8; H, 4.2;
C
25
H
32
N
4
6
S
4
Complex
1
2
(
Zn(1)–O(1)
Zn(1)–O(2)
Zn(1)–N(3)
Zn(1)–N(4)
Ni(1)–O(1)
Ni(1)–O(2)
Ni(1)–O(5)
Ni(1)–O(6)
Ni(1)–N(1)
Ni(1)–N(2)
2.027(2)
2.020(2)
1.947(3)
1.955(3)
2.029(2)
2.014(2)
2.123(2)
2.159(2)
2.030(3)
2.027(3)
2.056(3)
2.015(3)
1.957(5)
1.936(5)
2.020(3)
1.992(3)
2.106(4)
2.134(3)
2.010(4)
2.011(3)
-1
N, 7.7%. FT-IR (KBr, cm ): 1626 (C@N); 2074 (NCS). UV–Vis
-
1
-1
4
[k
max (nm)] [ max(L mol cm )] (DMSO): 280 (2.96 ꢀ10 ); 352
e
4
(
2.71 ꢀ10 ); 580 (8.75); 993 (6.79). Magnetic moment = 3.13 BM.
2
2.1.2.2. Synthesis of [(DMSO)
2
NiL Zn(NCS)
2
] (2). It was prepared in a
2
similar method as that of complex 1 except that H
instead of H
obtained after 3–4 days on slow evaporation of the solution in
open atmosphere.
2
L
was used
1
2
L . Single crystals, suitable for X-ray diffraction, were
Yield: 596 mg, 78%. Anal. Calc. for
27 36 4 6 4
C H N NiO S Zn
(
FW = 764.92): C, 42.39; H, 4.74; N, 7.32. Found: C, 42.4; H, 4.6;
Table 3
Selected bond angles (°) for complexes 1 (subunit A) and 2.
-1
N, 7.4%. FT-IR (KBr, cm ): 1626 (C@N); 2088 (NCS). UV–Vis
-
1
-1
4
[k
max (nm)] [
e
max(L mol cm )] (DMSO): 290 (3.16 ꢀ10 ); 363
Complex
1
2
4
(
3.43 ꢀ10 ); 577 (9.87); 987 (5.75). Magnetic moment = 3.11 BM.
O(1)–Zn(1)–O(2)
O(1)–Zn(1)–N(3)
O(1)–Zn(1)–N(4)
O(2)–Zn(1)–N(3)
O(2)–Zn(1)–N(4)
N(3)–Zn(1)–N(4)
O(1)–Ni(1)–O(2)
O(1)–Ni(1)–O(5)
O(1)–Ni(1)–O(6)
O(1)–Ni(1)–N(1)
O(1)–Ni(1)–N(2)
O(2)–Ni(1)–O(5)
O(2)–Ni(1)–O(6)
O(2)–Ni(1)–N(1)
O(2)–Ni(1)–N(2)
O(5)–Ni(1)–O(6)
O(5)–Ni(1)–N(1)
O(5)–Ni(1)–N(2)
O(6)–Ni(1)–N(1)
O(6)–Ni(1)–N(2)
N(1)–Ni(1)–N(2)
79.13(9)
77.01(12)
106.86(16)
118.68(16)
118.03(18)
108.89(17)
120.05(19)
78.36(12)
87.99(13)
94.84(12)
91.62(14)
171.11(12)
92.21(13)
89.73(12)
169.83(14)
92.96(13)
176.85(13)
89.12(14)
90.49(14)
89.42(13)
86.93(13)
97.12(14)
115.39(12)
112.79(12)
111.69(12)
117.81(12)
115.18(13)
79.21(9)
2
.2. Physical measurements
Elemental analyses (carbon, hydrogen and nitrogen) were per-
formed using a Perkin Elmer 240C elemental analyzer. IR spectra
-
1
in KBr (4500–500 cm ) were recorded with a Perkin Elmer Spec-
trum Two spectrophotometer. Electronic spectra in DMSO were
recorded on a Perkin Elmer Lambda 35 UV–Vis spectrophotometer.
Steady state photoluminescence spectra in DMSO were obtained in
Shimadzu RF-5301PC spectrofluorometer at room temperature.
Time dependent photoluminescence spectra were recorded using
Hamamatsu MCP photomultiplier (R3809) and were analyzed by
using IBHDAS6 software. The emissions of complexes are tenta-
tively attributed to the intra-ligand transitions modified by metal
coordination. Intensity decay profiles were fitted to the sum of
88.65(9)
90.46(9)
91.14(10)
168.98(10)
90.18(10)
87.04(9)
168.81(11)
91.36(9)
177.19(9)
95.29(11)
85.66(10)
87.39(11)
94.77(10)
98.77(11)
ꢀ
ꢁ
P
ꢁ
t
i
exponentials series IðtÞ¼
ia
i
exp
, where
a
i
was a factor rep-
s
resenting the fractional contribution to the time resolved decay of
the component with a lifetime of
i
s . Bi-exponential function was
used to fit the decay profile for both complexes, with obtaining
luminescence decay time associated with the i-th component,
respectively. The magnetic susceptibility measurements were per-
formed with an EG and PAR vibrating sample magnetometer,
model 155 at room temperature (300 K) in a 5000 G magnetic field,
and diamagnetic corrections were performed using Pascal’s
2
v
close to 1. The intensity-averaged life time (
from the result of the exponential model using
and
s
av) was determined
P
2
ia
i
s
P
i
s
a
m
¼
, where
i i
ia s
a
i
s
i
are the pre-exponential factors and excited state

A. Bhattacharyya et al. / Polyhedron 112 (2016) 109–117
111
Table 4
Geometric features (distances in Å and angles in °) of the C–Hꢂꢂꢂ
p interactions
obtained for complexes 1 and 2.
Complex C–HꢂꢂꢂCg(Ring)
HꢂꢂꢂCg (Å) C–HꢂꢂꢂCg (°) CꢂꢂꢂCg (Å)
a
1
C(23)–H(23A)ꢂꢂꢂCg(7)
2.68
2.92
2.84
2.95
2.97
2.71
136
146
135
150
133
143
3.433(4)
3.749(4)
3.583(4)
3.787(4)
3.690(5)
3.523(7)
b
c
C(24)–H(24A)ꢂꢂꢂCg(15)
b
C(25)–H(25A)ꢂꢂꢂCg(8)
b
C(29)–H(29)ꢂꢂꢂCg(7)
C(47)–H(47A)ꢂꢂꢂCg(15)
d
2
C(22)–H(22A)ꢂꢂꢂCg(8)
a
b
c
Symmetry transformations: = 2 ꢁx, ꢁy, 1 ꢁz; = 2 ꢁx, 1 ꢁy, 1 ꢁz; = 3 ꢁx,
d
1
ꢁy, 2 ꢁz; = 1 ꢁx, 1 ꢁy, ꢁz.
Cg(7) = Centre of gravity of the ring [C(2)–C(3)–C(4)–C(5)–C(6)–C(7)]; Cg(8)
=
=
1
Centre of gravity of the ring [C(13)–C(14)–C(15)–C(16)–C(17)–C(18)]; Cg(15)
Centre of gravity of the ring [C(27)–C(28)–C(29)–C(30)–C(31)–C(32)] for complex
and Cg(8) = Centre of gravity of the ring [C(15)–C(16)–C(17)–C(18)–C(19)–C(20)];
for complex 2.
constants. Effective magnetic moments were calculated using the
1/2
M M
formula leff = 2.828(v T) , where v is the corrected molar sus-
ceptibility. The instrument was calibrated using metallic nickel.
Powder X-ray diffraction were performed on a Bruker D8 instru-
ment with Cu K
a radiation. In this process, the complexes were
ground with a mortar and pestle to prepare fine powders. The pow-
ders were then dispersed with alcohol onto a zero background
holder (ZBH). The alcohol was allowed to evaporate to provide a
nice, even coating of powder adhered to the sample holder.
Fig. 1. Perspective view of complex 1 (subunit A) with selective atom numbering
scheme. Methyl groups have been omitted for clarity.
applied to the data using the program SADABS [32]. Details of
crystallographic data and refinement details are given in Table 1.
Important bond lengths and angles are listed in Tables 2–5
respectively.
2
.3. X-ray crystallography
Suitable single crystals of complexes 1 and 2 were used for data
collection using a ‘Bruker SMART APEX II’ diffractometer equipped
with graphite-monochromated Mo K radiation (k = 0.71073 Å) at
00 K. The molecular structures were solved by direct method and
a
1
2.4. Hirshfeld surfaces
2
refined by full-matrix least squares on F using the SHELX-2014
package [30,31]. Non-hydrogen atoms were refined with anisotro-
pic thermal parameters. The hydrogen atoms were placed in their
geometrically idealized positions and constrained to ride on their
parent atoms. Multi-scan empirical absorption corrections were
Hirshfeld surfaces [33–35] and the associated 2D-fingerprint
[36–38] plots were calculated using Crystal Explorer [39] which
accepted a structure input file in CIF format. Bond lengths to
hydrogen atoms were set to standard values. For each point on
Scheme 1. Synthetic route to ligands and complexes.

1
12
A. Bhattacharyya et al. / Polyhedron 112 (2016) 109–117
the Hirshfeld isosurface, two distances d
e
, the distance from the
point to the nearest nucleus external to the surface and d
i
, the dis-
tance to the nearest nucleus internal to the surface, were defined.
The normalized contact distance (dnorm) based on d and d was
e i
given by
vdw
vdw
ðd
i
ꢁri
Þ
ðd
e
ꢁre
Þ
d
norm
¼
þ
vdw
i
vdw
e
r
r
vdw
vdw
where r
i
and r
e
were the van der Waals radii of the atoms.
The value of dnorm was negative or positive depending on inter-
molecular contacts, being shorter or longer than the van der Waals
separations. The parameter dnorm displayed a surface with a red-
white-blue color scheme, where bright red spots highlighted
shorter contacts, white areas represented contacts around the van
der Waals separation, and blue regions were devoid of close con-
tacts. For a given crystal structure and set of spherical atomic elec-
tron densities, the Hirshfeld surface was unique [40] and it was this
property that suggested the possibility of gaining additional insight
into the intermolecular interaction of molecular crystals.
3
. Results and discussion
3
.1. Synthesis
Fig. 3. Perspective view of a supra-molecular dimer formed by inter-molecular
interactions of complex 1 with selective atom numbering scheme. Only
relevant atoms are shown in the figure.
C–Hꢂꢂꢂ
p
3
-Methoxysalicylaldehyde has been refluxed with 1,3-diamino-
propane and 2,2-dimethyl-1,3-diaminopropane respectively to
1
2
form two compartmental Schiff base ligands, H
2
L
2
and H L ,
respectively following the literature method [17,19,21,22]. These
Schiff bases on reaction with zinc(II) acetate dihydrate and nickel
(
II) thiocyanate tetrahydrate give two hetero-dinuclear complexes.
Formation of both complexes is shown in Scheme 1. Addition of
only nickel(II) thiocyanate tetrahydrate (1 mmol) produced
1
2
mononuclear complexes [(H
O)
2 2
NiL ] and [NiL ]ꢂ1.75H
2
O, struc-
tures of which were already reported by other groups [41–43].
The effort to convert these complexes into complexes 1 and 2 by
dissolving them in DMSO followed by adding with zinc(II) acetate
dihydrate and sodium thiocyanate was not successful. The key step
in the synthesis of these complexes is to use nickel(II) thiocyanate
tetrahydrate and zinc(II) acetate dihydrate in a single pot.
Fig. 4. Perspective view of a supra-molecular dimer formed by inter-molecular
C–Hꢂꢂꢂ
p interactions of complex 1 with selective atom numbering scheme. Only
relevant atoms are shown in the figure.
3
3
.2. Structure description
1
2
.2.1. [(DMSO)
2
NiL Zn(NCS)
2
] (1) and [(DMSO)
2
NiL Zn(NCS)
2
] (2)
Complex 1 and 2 both crystallize in the triclinic space group P 1ꢀ .
The X-ray crystal structure determination reveals that in complex
1 there are two independent dinuclear subunits (A and B) with
Fig. 2. Perspective view of complex 2 with selective atom numbering scheme.
Methyl groups attached to oxygen and sulfur atoms have been omitted for clarity.

A. Bhattacharyya et al. / Polyhedron 112 (2016) 109–117
113
with inner N
2
O
2
and outer O
4
compartments with nickel(II) occu-
pying the inner N
2 2 4
O cavity and zinc(II) occupying the outer O
cavity. The nickel(II) centre, [Ni(1) for complex 1 and Ni(2) for
complex 2], has a pseudo-octahedral geometry, where two imine
nitrogen atoms, N(1) and N(2), and two phenoxo oxygen atoms,
O(1) and O(2), of the deprotonated di-Schiff base constitute the
equatorial plane. The deviation of all the coordinating atoms, O
(
1), O(2), N(1) and N(2), in the basal plane from the mean plane
passing through them are 0.100(2), ꢁ0.100(2), ꢁ0.083(3) and
.084(3) Å for complex 1 and ꢁ0.031(3), 0.031(3), 0.026(3) and
0.026(3) Å for complex 2 respectively. The deviation of Ni(1) from
0
ꢁ
the same plane is ꢁ0.0006(5) Å for complex 1 and 0.0020(5) Å for
complex 2 respectively. In the axial positions, the nickel(II) center
is coordinated by two oxygen atoms from two DMSO molecules
furnishing the distorted octahedral coordination sphere around
nickel(II). The phenoxo oxygen atoms of the Schiff base are also
coordinated to the zinc(II) centre, Zn(1). The bridging angles, Ni
(
(
1)–O(2)–Zn(1) and Ni(1)–O(1)–Zn(1), are 101.11(10)° and 100.36
9)° in complex 1 and 103.2(1)° and 100.8(1)° in complex 2 respec-
tively. The dihedral angle between the Ni(1)O(1)O(2) and Zn(1)O
(
1)O(2) planes are 4.12° in complex 1 and 7.47° in complex 2, indi-
cating the Ni(1)O(1)O(2)Zn(1) core almost planar. The potential
donor methoxy oxygen atoms, O(1) and O(2), of the compartmen-
tal Schiff bases remain essentially pendant and therefore the
potential hexadentate Schiff bases behave as tetradentate ones in
both complexes. Two nitrogen atoms, N(3) and N(4), from two
thiocyanates coordinate zinc(II) to complete its distorted tetrahe-
dral geometry in each complex. The intra-dimer nickel(II)ꢂꢂꢂzinc
(II) distance is 3.1154(5) Å in complex 1 and 3.1410(6) Å in
complex 2.
Fig. 5. Perspective view of the supra-molecular dimer formed by inter-molecular
interactions of complex 1 with selective atom numbering scheme. Only
relevant atoms are shown in the figure.
C–Hꢂꢂꢂ
p
equivalent geometry. Perspective views of complex 1 (subunit A)
and complex 2 are given in Figs. 1 and 2 respectively. Selected
bond lengths and bond angles are listed in Tables 2 and 3. The
structures of subunit A of complex 1 along with that of complex
Complex 1 shows significant C–Hꢂꢂꢂ
gen atom, H(23A), attached to carbon atom, C(23), is involved in
interaction with a symmetry related
p interactions. The hydro-
2
are described in the following paragraphs. The perspective view
an inter-molecular C–Hꢂꢂꢂ
p
and description of the structure of subunit B with selective atom
numbering scheme of complex 1 is given in the Supplementary
information (SI).
(2 ꢁx, ꢁy, 1 ꢁz) phenyl ring [C(2)–C(3)–C(4)–C(5)–C(6)–C(7)] to
form a supra-molecular dimer as shown in Fig. 3. Similarly, the
hydrogen atom, H(25A), attached to carbon atom, C(25), is
The molecular structure of complexes 1 and 2 are built from
involved in inter-molecular C–Hꢂꢂꢂ
p interaction with the symme-
try related (2 ꢁx, 1 ꢁy, 1 ꢁz) phenyl ring [C(13)–C(14)–C(15)–C
isolated hetero-dinuclear molecules of [(DMSO)
For complex 1, L = L and for complex 2, L = L ), where nickel(II)
2
NiLZn(NCS)
2
]
1
2
(
(16)–C(17)–C(18)] to form another supra-molecular dimer as
1
is hexa-coordinated and zinc(II) is tetra-coordinated. H
2
L
and
shown in Fig. 4. Again, inter-molecular C–Hꢂꢂꢂ
p interaction is also
2
H L are two potential hexadentate compartmental Schiff bases
2
observed between the hydrogen atom, H(47A) and the symmetry
Fig. 6. Inter-molecular C–Hꢂꢂꢂp interactions in complex 1 with selective atom numbering scheme. Only relevant atoms are shown in the figure.

1
14
A. Bhattacharyya et al. / Polyhedron 112 (2016) 109–117
related (3 – x, 1 ꢁy, 2 ꢁz) phenyl ring [C(27)–C(28)–C(29)–C(30)–
C(31)–C(32)] (Fig. 5). Complex 1 also shows two intra-molecular
C–Hꢂꢂꢂ
p interactions which are confined between two different
subunits of the complex having different symmetries. The
hydrogen atom, H(24A), attached to carbon atom, C(24) and the
hydrogen atom, H(29), attached to carbon atom C(29), is involved
in intra-molecular C–Hꢂꢂꢂ
p interactions with symmetry related
3 ꢁx, 1 ꢁy, 2 ꢁz) phenyl ring [C(27)–C(28)–C(29)–C(30)–C(31)–
(
C(32)] and (2 ꢁx, 1 ꢁy, 1 ꢁz) phenyl ring [C(2)–C(3)–C(4)–C(5)–
C(6)–C(7)] respectively. All these interactions are shown in Fig. 6.
The details of the geometric features of the C–Hꢂꢂꢂ
p
interactions
are given in Table 4.
Complex 2 shows only one inter-molecular C–Hꢂꢂꢂ
p interaction.
The hydrogen atom, H(22A), attached to carbon atom C(22), is
involved in C–Hꢂꢂꢂ interaction with a symmetry related (1 ꢁx,
ꢁy, ꢁz) phenyl ring [C(15)–C(16)–C(17)–C(18)–C(19)–C(20)] to
form a supra-molecular dimer (Fig. 7). The details of the geometric
features of the C–Hꢂꢂꢂ interactions are given in Table 4.
p
1
p
3.3. Spectral and magnetic properties
Fig. 8. Time dependent photoluminescence decay profile of complexes 1 and 2.
Strong and sharp bands around 1626 cm-1 due to azomethine
(
C@N) groups have been routinely noticed in the IR spectra for
both complexes [44]. Sharp bands in the IR spectra of complexes
-
1
-1
1
and 2 at 2074 cm and 2088 cm respectively indicate the
presence of thiocyanate [45].
Electronic spectra of both complexes in DMSO display absorp-
tion bands around 580 nm and 990 nm. These bands may be
3
3
2g(F) and 3
3
assigned as
46,47]. The higher energy d-d band,
observed as it is obscured by a strong charge transfer transition
ꢃ350 nm) in each case [46,47].
T
1g(F)
A
T
2g(F)
A2g(F) respectively
A2g(F), cannot be
3
3
[
T1g(P)
(
Fig. 9. Experimental and simulated PXRD patterns of complex 1 confirming purity
of the bulk material.
Both complexes exhibit fluorescence in DMSO medium. The flu-
orescence data are listed in Table 5 (without solvent correction).
⁄
These are assigned as intra-ligand (
mean lifetimes (
for 2) at room temperature. The lifetime decay profile of
p
–
p
) fluorescence [48]. The
C
avg) of the exited states are 4 ns (for 1) and 5 ns
(
complexes is shown in Fig. 8.
The effective magnetic moments (ꢃ3.1 BM) of both complexes
clearly confirmed the presence of two unpaired electrons (S = 1)
in a pseudo-octahedral environment, in agreement with high-spin
6
2
configuration t2g
e
g
, as was also observed in similar systems
Fig. 7. Perspective view of the supra-molecular dimer formed by inter-molecular
interactions in complex 2 with selective atom numbering scheme. Only
relevant atoms are shown in the figure.
[46,47].
C–Hꢂꢂꢂ
p
3.4. PXRD
Table 5
Photophysical data for complexes 1 and 2.
The experimental PXRD patterns of the bulk products are in
good agreement with the simulated XRD patterns from single
crystal X-ray diffraction results, indicating consistency of the bulk
sample. The simulated patterns of the complexes were calculated
from the single crystal structural data using the CCDC Mercury
Complex
Absorption (nm)
Emission (nm)
1
2
280
280
329
329

A. Bhattacharyya et al. / Polyhedron 112 (2016) 109–117
115
software. As a representative example the experimental and simu-
lated PXRD patterns of complex 1 is shown in Fig. 9.
plots can be decomposed to highlight particular atoms pair close
contacts. This decomposition enables separation of contributions
from different interaction types, which overlap in the full finger-
print. The proportions of OꢂꢂꢂH/HꢂꢂꢂO interactions comprise 5.1%
and 2.9% of the Hirshfeld surfaces for complexes 1 and 2, respec-
tively. This OꢂꢂꢂH/HꢂꢂꢂO interaction also appears as two distinct
spikes in the 2D fingerprint plots (Fig. 11). The lower spike corre-
sponding to the donor spike represents the OꢂꢂꢂH interactions
3.5. Hirshfeld surfaces
The Hirshfeld surfaces of the two complexes, mapped over dnorm
(
range of ꢁ0.1 to 1.5 Å), shape index and curvedness, are illustrated
in Fig. 10. The surfaces are shown as transparent to allow visualiza-
tion of the molecular moiety around which they are calculated. The
dominant interaction between OꢂꢂꢂH/HꢂꢂꢂO atoms can be seen in
the Hirshfeld surfaces as red spots on the dnorm surface in Fig. 10.
Other visible spots in the Hirshfeld surfaces correspond to CꢂꢂꢂH
and HꢂꢂꢂH contacts. The small extent of area and light color on
the surface indicates weaker and longer contact other than hydro-
gen bonds. The intermolecular interactions appear as distinct
spikes in the 2D fingerprint plot (Fig. 11). Complementary regions
are visible in the fingerprint plots where one molecule acts as
(d
and the upper spike being an acceptor spike represents the HꢂꢂꢂO
interactions (d = 1.0, d = 1.36 Å in 1 and d = 1.18, d = 1.5 Å in 2,
i e i e
= 1.36, d = 1.0 Å in 1 and d = 1.5, d = 1.18 Å in 2, respectively)
i
e
i
e
respectively) in the fingerprint plot (Fig. 11). Similarly the propor-
tion of CꢂꢂꢂH/HꢂꢂꢂC interactions comprises 20.5% and 17.8% of the
Hirshfeld surfaces for complexes 1 and 2, respectively. This
CꢂꢂꢂH/HꢂꢂꢂC interaction also appears as two distinct spikes in the
2D fingerprint plots (Fig. 11). The lower spike corresponding to
the donor spike represents the CꢂꢂꢂH interactions (d
i
= 1.59,
donor (d
e
< d
i
) and the other as an acceptor (d
e
> d
i
). The fingerprint
d
e
= 1.1 Å in 1 and d = 1.56, d = 1.0 Å in 2, respectively) and the
i
e
Fig. 10. Hirshfeld surfaces mapped with dnorm (top), shape index (middle) and curvedness (bottom) of complexes 1 and 2.

1
16
A. Bhattacharyya et al. / Polyhedron 112 (2016) 109–117
Fig. 11. Fingerprint plot: Full (top), resolved into HꢂꢂꢂO/OꢂꢂꢂH (middle) and HꢂꢂꢂC/CꢂꢂꢂH (bottom) contacts contributed to the total Hirshfeld Surface area of complexes 1 and
2.
upper spike being an acceptor spike represents the HꢂꢂꢂC
interactions (d = 1.1, d = 1.59 Å in 1 and d = 1.0, d = 1.56 Å in 2,
respectively) in the fingerprint plot (Fig. 11).
nickel(II) complexes could not be converted into the hetero-dinu-
clear nickel(II)/zinc(II) complexes on reacting with zinc(II) and thio-
cyanate. The beauty of the present work, therefore, lies in the
discovery of one pot synthesis of theses hetero-dinuclear com-
plexes. Given the novel role of zinc(II) in the field of electronic and
opto-electronic research, the present findings may provide insight
and serve as a prototype for preparing other such complexes. Work
is in progress to get better yield of the reaction and to synthesize
other photo-luminescent hetero-dinuclear complexes.
i
e
i
e
4
. Concluding remarks
The tandem synthesis and characterization of two iso-structural
1
2
2 2 2 2
complexes [(DMSO) NiL Zn(NCS) ] (1) and [(DMSO) NiL Zn(NCS) ]
(
2) have been described in the present paper. It has been presented
that the reaction of nickel(II) thiocyanate tetrahydrate and zinc(II)
with potential hexadentate N donor compartmental Schiff bases
can afford hetero-dinuclear complexes with nickel(II) sitting in the
inner N compartment and zinc(II) sitting in the outer O
compartment. Use of only nickel(II) produces mononuclear species
containing nickel(II) in the inner N cavity. These mononuclear
Acknowledgments
2 4
O
A.B. thanks the UGC, India, for awarding a Senior Research Fel-
lowship. Crystallographic data were collected at the DST-FIST,
India, funded by Single Crystal Diffractometer Facility at the
Department of Chemistry, Jadavpur University.
2
O
2
4
2 2
O

A. Bhattacharyya et al. / Polyhedron 112 (2016) 109–117
117
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3
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