Variation in molecular and crystalline architectures of di- and poly-nuclear cadmium(II) complexes on changing the denticity of the blocking ligands

Article abstract of DOI:10.1016/j.poly.2014.02.019

Three cadmium(II) complexes, [Cd(dmpn)(μ-1,1-N₃) ₂]_n (1), [Cd(L¹)₂Cd(N ₃)₂] (2) and [Cd₂(L²) ₂(Cl)₂] (3) {where dmpn is a bidentate ch

Full text of DOI:10.1016/j.poly.2014.02.019

Polyhedron 75 (2014) 57–63
Contents lists available at ScienceDirect
Polyhedron
journal homepage: www.elsevier.com/locate/poly
Variation in molecular and crystalline architectures
of di- and poly-nuclear cadmium(II) complexes on changing
the denticity of the blocking ligands
a
a
b
a,
⇑
Sumit Roy , Prasanta Kumar Bhaumik , Klaus Harms , Shouvik Chattopadhyay
a
Department of Chemistry, Inorganic Section, Jadavpur University, Kolkata 700 032, India
FachbereichChemie, Philipps-Universität Marburg, Hans-Meerwein-Straße, 35032 Marburg, Germany
b
a r t i c l e i n f o
a b s t r a c t
1
2
Article history:
3 2 n 2 3 2 2 2 2
Three cadmium(II) complexes, [Cd(dmpn)(l-1,1-N ) ] (1), [Cd(L ) Cd(N ) ] (2) and [Cd (L ) (Cl) ] (3)
Received 20 November 2013
Accepted 5 February 2014
Available online 21 February 2014
1
{
where dmpn is a bidentate chelating ligand N,N-dimethyl-1,3-diaminopropane, HL is a tetradentate
2
Schiff base 2-((3-(dimethylamino)propylimino)methyl)-6-methoxyphenol and HL is a tridentate Schiff
base 2-((2-(diethylamino)ethylimino)methyl)phenol}, were prepared and characterised by elemental
analysis, IR, UV–Vis 1H NMR and fluorescence spectroscopy, and single crystal X-ray diffraction studies.
Complex 1 is polynuclear with double end-on azide bridges. The hydrogen bonding in complex 1 pro-
duces a three-dimensional supramolecular network. Complex 2 is dinuclear and contains octahedral cad-
mium(II) centres. Complex 3 is also dinuclear, but contains square pyramidal cadmium(II) centres.
Keywords:
Crystal structure
Cadmium(II)
Schiff base
End-on azide
Intramolecular C–HÁ Á Á
p interactions are present in complex 2. There is no supramolecular interaction
Supramolecular interaction
in complex 3. The variation in the denticity of the ligands causes changes in the molecular and crystalline
architectures of the complexes. All the three complexes show fluorescence.
Ó 2014 Elsevier Ltd. All rights reserved.
1
. Introduction
cadmium(II) is known to exhibit a flexible geometry as a result
1
0
of its d configuration with no CFSE in any geometry. Thus the
geometries and coordination numbers of cadmium(II) are mainly
controlled by the steric requirements of the ligands [28–31]. Schiff
bases are very popular chelating ligands and have been used by
The design and synthesis of coordination polymers of Group 12
metal ion complexes [1–10] are of continuing interest because of
their functional behaviours, especially as electronic and opto-
electronic devices [11–14]. Exploiting the varieties of coordination
geometries around these metal ions, diverse molecular and crystal-
line architectures may be produced through strong metal–ligand
covalent bonds and multiple weak non-covalent forces [15–21].
Varieties of bridging groups have been employed for the synthesis
of such systems; pseudohalides have long been known for their
versatile coordination modes [15]. Numerous applications of
coordination polymers in the field of gas adsorption and separation
several groups to synthesise cadmium(II) complexes [32–36]. A
1
dinuclear complex, [Cd(L )
2
2
CdCl ], was prepared on adding cad-
mium(II) chloride into a methanol solution of the Schiff base ligand
1
HL , obtained by the condensation of N,N-dimethyl-1,3-diamino-
propane (dmpn) with 3-methoxysalicylaldehyde [32]. Another
1
dinuclear complex, [Cd(L )
2
Cd(NCS)
2
], could be produced on
1
2 2
refluxing [Cd(L ) CdCl ] with potassium thiocyanate [33]. A similar
tetradentate Schiff base, produced by the 1:1 condensation of
3-ethoxysalicylaldehyde with dmpn in methanol, was made to re-
act with cadmium(II) acetate and ammonium thiocyanate to pro-
[
22], luminescence [23] and ion exchange [24] have been achieved
mostly because of their stability in the solid state.
Cadmium is an extremely toxic element and it is currently a
very challenging task to develop several chelating ligands for the
treatment of cadmium intoxication [25]. The synthesis of cad-
mium(II) phenoxo complexes deserves further exploration follow-
ing the recent discovery of naturally occurring cadmium(II)
containing carbonic anhydrase [26,27]. On the other hand,
2 2
duce another dinuclear complex, [Cd(ligand) Cd(NCS) ] [34]. In
all these dinuclear complexes, the two cadmium(II) centres reside
in different environments. On the other hand, the reaction of dmpn
with salicylaldehyde produced a tridentate NNO donor Schiff base
which could also be used to form complex with cadmium(II)
2 2 2
acetate to form [Cd (ligand) (OAc) ], where both the cadmium(II)
centres reside in identical environments [35]. Addition of a meth-
anol solution of sodium thiocyanate to this complex produced
⇑
Corresponding author. Tel.: +91 33 24572941.
E-mail address: shouvik.chem@gmail.com (S. Chattopadhyay).
[
2 2 2 n
Cd (ligand) (NCS) ] , with two cadmium(II) centres in similar
http://dx.doi.org/10.1016/j.poly.2014.02.019
277-5387/Ó 2014 Elsevier Ltd. All rights reserved.
0

5
8
S. Roy et al. / Polyhedron 75 (2014) 57–63
environments [36]. Thus the change in denticity of the Schiff bases
dictates the geometry and composition of the cadmium(II) com-
plexes. The syntheses of all the complexes are shown in Scheme 1.
In the present work, we have used N,N-dimethyl-1,3-diamino-
propane as a bidentate blocking ligand and its condensation prod-
uct with 3-methoxysalicylaldehyde as a tetradentate blocking
ligands and also to report the syntheses, structures and lumines-
cence behaviour of the complexes.
2
. Experimental
2.1. Materials
1
ligand (HL ) in forming cadmium(II) azide complexes. We have
2
also used another tridentate Schiff base (HL ), produced by the
All chemicals were of reagent grade and used as purchased from
condensation of N,N-diethyl-1,2-diaminoethane and salicyalalde-
hyde, to prepare a cadmium(II) chloride complex. Our intention
was to examine the changes, if any, in the molecular and crystal-
line architectures of the complexes on changing the denticity of
the ligands. Use of N,N-dimethyl-1,3-diaminopropane as a block-
ing ligand forms a neutral one-dimensional polymeric chain with
cadmium(II) and azide; and hydrogen bonding interactions lead
to a three-dimensional polymeric architecture. On the other hand,
the tetradentate Schiff base forms a dinuclear complex with cad-
Sigma–Aldrich without further purification.
CAUTION! The azide complexes are potentially explosive.
Although no problem was encountered in the present study, only
small amounts of the materials should be prepared and they must
be handled with care.
2.2. Synthesis
3 2 n
2.2.1. Synthesis of [Cd(dmpn)(l-1,1-N ) ] (1)
mium(II) and azide; and there is only intramolecular C–HÁ Á Á
p
A
methanol solution of N,N-dimethyl-1,3-diaminopropane
interactions. However, in both the complexes, the cadmium(II)
centres assume octahedral geometries. Meanwhile, the reaction
of a tridentate Schiff base, produced by the condensation of N,N-
diethyl-1,2-diaminoethane and salicylaldehyde, with cadmium(II)
chloride produced a dinuclear complex in which each cadmium(II)
centre assumes a square pyramidal geometry. We would like to
compare the changes in the molecular and crystalline architectures
of cadmium(II) complexes with the change in the denticity of the
(
dmpn) (1 mmol, 0.125 ml) was added to a methanol solution of
cadmium (II) acetate (1 mmol, 0.266 g) dropwise with constant
stirring. An aqueous methanol solution of sodium azide (1 mmol,
0
.065 g) was then added to this mixture dropwise to get a white
precipitate. X-ray quality single crystals were obtained from DMSO
solution on slow evaporation.
Yield: 0.41 g (69%). Anal. Calc. for C10
H28Cd
2
N
16: C, 20.11; H,
À1
4
.73; N, 37.52. Found: C, 20.35; H, 4.53; N, 36.55%. IR (KBr, cm ):
Scheme 1. Schematic representation of the synthesis of a few reported cadmium(II) complexes with Schiff bases.

S. Roy et al. / Polyhedron 75 (2014) 57–63
59
3
2
2
357, 3313, 3263 (
.89 (s, 2H); 2.19 (s, 6H); 2.73 (t, 2H, J = 5.4 Hz); 1.58 (m, 2H);
.42 (t, 2H, J = 5.38 Hz). UV–Vis, kmax (nm), (emax (dm mol cm ))
m
NH2), 2042 (
m
N3). 1H NMR (DMSO-d
6
) d ppm:
monochromated MoK
a
radiation, and were corrected for absorp-
tion effects using multi-scanned reflections. Non hydrogen atoms
were refined anisotropically. All the hydrogen atoms were placed
in their geometrically idealised positions and constrained to ride
on their parent atoms. The programs used were SHELXL-97 [37,38],
PLATON [39], BRUKER APEX II [40], SAINT V8.32B [41], SHELXL-2013
[37], DIAMOND [42], ORTEP [43] and MERCURY [44]. The crystallo-
graphic and refinement data are summarised in Table 1.
3
À1
À1
1
2
(
DMSO): 370 (1.2 Â 10 ), 260 (6.9 Â 10 ).
1
2.2.2. Synthesis of [Cd(L )
2 3 2
Cd(N ) ] (2)
A methanol solution of 3-methoxysalicylaldehyde (1 mmol,
.152 g) and N,N-dimethyl-1,3-diaminopropane (1 mmol,
.125 ml) was refluxed for 1 h to prepare the tetradentate Schiff
0
0
base, 2-((3-(dimethylamino)propylimino)methyl)-6-methoxyphe-
nol (HL ). The Schiff base was not isolated and was used directly
3
. Result and discussion
1
for the preparation of complex 2. A methanol solution of cad-
mium(II) chloride monohydrate (1 mmol, 0.201 g) was added
dropwise to a methanol solution of the Schiff base, followed by
addition of an aqueous methanol solution of sodium azide
3
.1. Synthesis
3 2 n
The azide bridged polymeric complex [Cd(dmpn)(l-1,1-N ) ]
(1) was synthesised by stirring N,N-dimethyl-1,3-diaminopropane
(
1 mmol, 0.065 g) with constant stirring. The stirring was contin-
(
dmpn) with cadmium (II) acetate and sodium azide in methanol.
ued for an additional 20 min. Diffraction quality single crystals
were obtained after a few days on slow evaporation of the reaction
mixture in the open atmosphere.
1
On the other hand, the Schiff base HL was prepared by the 1:1
condensation of 3-methoxysalicylaldehyde with dmpn in metha-
nol following the literature method [45]. Similarly, another Schiff
base, HL , was produced on refluxing N,N-diethyl-1,2-diaminoe-
thane with salicylaldehyde. The Schiff base ligands were not iso-
lated. A methanol solution of HL was then made to react with
cadmium(II) chloride monohydrate to prepare [Cd(L )
which on refluxing with sodium azide produced a dinuclear com-
plex, [Cd(L ) Cd(N ) ] (2). [Cd (L ) (Cl) ] (3) was produced on
2 3 2 2 2 2
Yield: 0.53 g (68%). Anal. Calc. C26
H
38Cd
2
N
10
O
4
: C, 40.06; H, 4.91;
2
À1
N, 17.97. Found: C, 40.08; H, 4.73; N, 17.89%. IR (KBr, cm ): 1645
1
(m
C
@
N
), 2040, 2061 (N
3
). H NMR (DMSO-d
6
) d ppm: 8.19 (s, 1H);
1
2
.15 (s, 6H); 3.7 (s, 3H); 3.64 (m, 2H); 1.8 (m, 2H); 2.55 (m, 2H);
1
2 2
CdCl ],
6
.3 (d, 1H, J = 8.55 Hz); 6.73 (dd, 1H, J = 7.4, 7.3 Hz); 6.8 (d, 1H,
3
À1
À1
J = 8.4 Hz). UV–Vis, kmax (nm), (
4
e
max (dm mol cm )) (DMSO):
1
2
3
3
3
01 (3.2 Â 10 ), 353 (3.1 Â 10 ), 284 (3.1 Â 10 ).
2
refluxing HL with cadmium(II) chloride monohydrate. The forma-
tion of all the three complexes is shown in Scheme 2.
2
2
.2.3. Synthesis of [Cd
2
(L )(Cl)
2
] (3)
A methanol solution of salicylaldehyde (1 mmol, 0.104 ml) and
N,N-diethyl-1,2-diaminoethane (1 mmol, 0.14 ml) was refluxed for
h to prepare the tridentate Schiff base 2-((2-(diethylamino)eth-
ylimino)methyl)phenol (HL ). The Schiff base was not isolated
and was used directly for the preparation of complex 3. A methanol
solution of cadmium(II) chloride monohydrate (1 mmol, 0.201 g)
was added dropwise to a methanol solution of the Schiff base with
constant stirring. The stirring was continued for an additional
3
.2. Description of the structures
1
2
3.2.1. [Cd(dmpn)(
3 2 n
l -1,1-N ) ] (1)
Complex 1 crystallises in the monoclinic space group P2
1
/n. The
asymmetric unit consists of one cadmium(II) centre coordinated by
nitrogen atoms, N(1) and N(5) of the chelating bidentate ligand
N,N-dimethyl-1,3-diaminopropane (dmpn) and N(8) and N(11) of
⁄
#
two different azides. N(8) and N(11) from two different symme-
3
0 min. Single crystals, suitable for X-ray diffraction were obtained
⁄
#
try related (symmetry transformations = 1 À x, Ày, 1 À z; = Àx,
Ày, 1 À z) azides coordinate the cadmium(II) centre to complete
its octahedral geometry. Each cadmium(II) centre is connected to
two neighbouring cadmium(II) centres with the help of end-on
azides, to form a one-dimensional chain, as shown in Fig. 1. Se-
lected bond distances and angles are presented in Table 2. The
bridge angles, Cd(1)–N(8)–Cd(1) and Cd(1)–N(11)–Cd(1)# are
after a few days on slow evaporation of the reaction mixture in the
open atmosphere.
Yield: 0.46 g (63%). Anal. Calc. for C26
.22; N, 7.63 Found: C, 41.75; H, 4.96; N, 7.60%. IR (KBr, cm ): 1645
H
38Cd
2
Cl
2
N
4
O
2
: C, 42.53; H,
À1
5
1
(m
C
@
N
). H NMR (DMSO-d
J = 7.3 Hz); 7.05 (dd, 1H, J = 6.30, 6.23 Hz); 6.46 (d, 1H, J = 8.6 Hz);
.28 (dd, 1H, J = 6.8, 7.8 Hz); 3.55 (t, 2H, J = 5.1 Hz); 2.76 (q, 4H,
J = 3.1 Hz); 2.69 (t, 2H, J = 4.8 Hz); 0.97 (t, 6H, J = 6.9 Hz). UV–Vis,
6
) d ppm: 8.23 (s, 1H); 7.02 (d, 1H,
⁄
6
1
06.74(5)° and 106.58(5)° respectively. The minimum intra-chain
3
À1
À1
3
CdÁÁÁCd distance is 3.839 Å. The conformation of the saturated six
membered chelate ring Cd(1)–N(1)–C(2)–C(3)–C(4)–N(5) is very
close to chair, with puckering parameters Q = 0.6655(13) Å,
k
(
max (nm), ( max (dm mol cm )) (DMSO): 394 (3.1 Â 10 ), 348
e
3 3
3.6 Â 10 ), 272 (3.2 Â 10 ).
h = 174.59(12)° and
u = 241.9(12)° [44].
2.3. Physical measurements
An interesting feature of this complex is the joining of neigh-
bouring chains via hydrogen bonds (Table 3). The hydrogen atom,
H(1) attached to the nitrogen atom, N(1) is hydrogen bonded with
Elemental analyses (C, H and N) were performed on a Perkin-El-
mer 240C elemental analyzer. Infrared spectra in KBr discs (4500–
u
À1
the symmetry-related azide nitrogen, N(10) (symmetry transfor-
5
00 cm ) were recorded using a Perkin Elmer FT-IR spectrum two
mation u = À1/2 + x, 1/2 À y, À1/2 + z). The hydrogen atom, H(2)
spectrometer. Electronic spectra in DMSO (800–200 nm) were re-
corded on a Jasco V-630 UV–Vis spectrophotometer. Fluorescence
attached to N(1) is involved in hydrogen bonding with the symme-
⁄
⁄
try related N(13) (symmetry transformation = 1 À x, Ày, 1 À z)
spectra in DMSO were obtained on a Hitachi F-7000 Fluorescence
spectrophotometer at room temperature. The 1H NMR spectra at
(Fig. 2). Association of the azide bridged one-dimensional chains,
[
3 2 n
Cd(dmpn)(l-1,1-N ) ] , via hydrogen bonding produces a three-
3
6
00 MHz were recorded in DMSO-d on a Bruker DRX 300
dimensional supramolecular network (Fig. 3). There are no other
supramolecular interactions in complex 1.
spectrometer.
2.4. X-ray crystallography
1
3
.2.2. Complex [Cd(L )
2 3 2
Cd(N ) ] (2)
Single crystals of the three complexes of suitable dimensions
Complex 2 crystallises in the orthorhombic space group Pbca.
The asymmetric unit consists of [Cd(L ) Cd(N ) ]. A perspective
2 3 2
view of complex 2 is shown in Fig. 4. The selected bond distances
and angles are gathered in Table 4. Within the dinuclear unit, two
1
were mounted in inert oil and transferred to the cold gas stream
of the cooling device. Data were collected at 100 K on a Bruker
D8 QUEST area detector diffractometer using graphite

6
0
S. Roy et al. / Polyhedron 75 (2014) 57–63
Table 1
Crystal data and refinement details of complexes 1, 2 and 3.
1
2
3
Formula
C
5
H
14CdN
8
C
26
H
38Cd
2
N
10
O
4
C
26 2 2 4 2
H38Cd Cl N O
Formula weight
Crystal size (mm)
T (K)
597.28
0.09 Â 0.13 Â 0.43
100(2)
779.46
734.30
0.18 Â 0.20 Â 0.35
0.42 Â 0.24 Â 0.24
100(2)
100(2)
Crystal system
Space group
a (Å)
b (Å)
c (Å)
monoclinic
P2 /n
1
orthorhombic
Pbca
17.4752(14)
17.5696(13)
19.7414(15)
90
orthorhombic
Pbca
7.9163(3)
20.1604(8)
36.1767(13)
90
6.6544(3)
10.7590(4)
14.6959(6)
92.914(1)
2
a (°)
Z
d
l
8
8
À3
calc (g cm
)
1.888
2.057
1.708
1.453
1.690
1.688
À1
(mm
)
F(000)
592
3136
2944
Total reflections
11028
112860
53,337
Unique reflections
Observed data [I > 2
No. of parameters
2414
2287
137
7004
5074
385
6602
6101
329
r
(I)]
R
R
R
int
0.018
0.064
0.0290
1
, wR
, wR
2
2
(all data)
[I > 2 (I)]
0.0157, 0.0325
0.0142, 0.0321
À0.33 and 0.45
0.0425, 0.0493
0.0221, 0.0422
À0.34 and 0.61
0.0251, 0.0462
0.0214, 0.0453
À0.54 and 0.63
1
r
À3
Largest difference in peak and hole (e Å
)
Scheme 2. Preparation of complexes 1–3.

S. Roy et al. / Polyhedron 75 (2014) 57–63
61
Fig. 1. One-dimensional polymeric structure of complex 1. Only the relevant atoms
are labelled. Hydrogen atoms are not shown for clarity. Symmetry transformations
#
Àx, Ày, 1 À z; ⁄ = 1 À x, Ày, 1 À z.
=
Table 2
Selected bond lengths (Å) and bond angles (°) of 1.
Cd(1)–N(1)
Cd(1)–N(5)
Cd(1)–N(8)
Cd(1)–N(11)
Cd(1)–N(11)
2.3092(12)
2.3927(12)
2.4070(12)
2.3343(12)
2.4005(12)
2.3760(12)
84.84(4)
98.33(4)
167.13(4)
94.43(4)
N(5)–Cd(1)–N(11)
N(5)–Cd(1)–N(11)
N(5)–Cd(1)–N(8)
92.63(4)
98.35(4)
161.86(4)
94.30(4)
165.00(4)
73.26(4)
73.42(4)
96.81(4)
99.18(4)
106.74(5)
106.58(5)
Fig. 2. Hydrogen bonding interaction in complex 1, shown along the ab plane.
#
#
u
Relevant atoms are shown. Symmetry transformations = À1/2 + x, 1/2 À y, À1/
⁄
⁄
2 + z; = 1 À x, Ày, 1 À z.
N(8)–Cd(1)–N(11)
N(8)–Cd(1)–N(11)
#
⁄
⁄
Cd(1)–N(8)
N(8)–Cd(1)–N(8)
#
N(1)–Cd(1)N–(5)
N(1)–Cd(1)–N(8)
N(1)–Cd(1)–N(11)
N(1)–Cd(1)–N(11)
N(11)–Cd(1)–N(11)
⁄
⁄
N(8) –Cd(1)–N(11)
#
N(8) –Cd(1)–N(11)
#
⁄
Cd(1)–N(8)–Cd(1)
⁄
Cd(1)–N(11)–Cd(1)#
N(1)–Cd(1)–N(8)
89.18(4)
N(5)–Cd(1)–N(8)
90.66(4)
Symmetry transformations # = Àx, Ày, 1 À z; ⁄ = 1 À x, Ày, 1 À z.
octahedral cadmium(II) centres are bridged by phenoxo oxygen
atoms. The Cd(1) centre is octahedrally surrounded by two phen-
oxo oxygen atoms, O(8) and O(23), two imine nitrogen atoms,
N(5) and N(20), and two amine nitrogen atoms, N(1) and N(16),
1
-
from two deprotonated Schiff base ligands, (L ) , in fac orienta-
tions. The Cd(2) centre is coordinated by two phenoxo oxygen
atoms, O(8) and O(23), and two methoxy oxygen atoms, O(9) and
O(24), from two deprotonated Schiff base ligands, and two
nitrogen atoms, N(100) and N(103), from two terminal azides.
The dinuclear bridging unit Cd
The rhombohedral angles are O(8)–Cd(1)–O(23), 74.80(5)°;
Cd(1)O(23)Cd(2), 105.09(6)°; O(8)Cd(2)O(23) 75.03(5)°;
2 2
O describes a rhombohedral plane.
Fig. 3. Diagram showing the three-dimensional hydrogen bonding network in
complex 1.
Cd(2)O(8)Cd(1), 105.05(6)°. The CdÁ Á ÁCd distance within the dinu-
clear unit is 3.5885(6) Å. The conformations of the saturated six
membered chelate rings Cd(1)–N(1)–C(2)–C(3)–C(4)–N(5) and
Cd(1)–N(16)–C(17)–C(18)–C(19)–N(20) are intermediate between
chair and half-chair, with puckering parameters Q = 0.7824(19) Å,
the other hand, H(13A), H(28B) and H(28C) are involved in C–HÁÁÁ
p
interactions with the chelate ring, Cd(1)–O(8)–C(8)–C(7)–C(6)–
N(5) (Fig. 5). Geometric features of the C–HÁ Á Á
p interactions are gi-
h = 17.85(15)°,
u
= 348.5(5)° and Q = 0.7765(19) Å, h = 17.09(15)°,
ven in Table S1.
u
= 350.4(6)°, respectively [46]. There are no significant hydrogen
bonding interactions in the structure.
2
3.2.3. Complex [Cd
2 2
(L ) (Cl)
2
] (3)
The complex shows significant intramolecular C–HÁ Á Á
p interac-
Complex 3 crystallises in the orthorhombic space group Pbca. A
tions [47–49]. The three methyl hydrogen atoms, H(14A), H(14B)
perspective view of complex 3 with the selected atom numbering
scheme is shown in Fig. 6. This features a double phenoxo bridged
dinuclear cadmium(II) complex, in which each penta-coordinated
and H(29B), of the Schiff base are involved in C–HÁ Á Á
p interactions
with the chelate ring, Cd(1)–O(23)–C(23)–C(22)–C(21)–N(20). On
Table 3
Hydrogen bond distances (Å) and angles (°) of 1.
Donor–hydrogenÁ Á Áacceptor
Donor–
hydrogen
HydrogenÁ Á Áacceptor
DonorÁ Á Áacceptor
\Donor–hydrogenÁ Á Áacceptor
ö
ö
N(1)–H(1)Á Á ÁN(10) Symmetry transformations = -1/2 + x,1/2-y,-1/2 + z
N(1)–H(2)Á Á ÁN(13)⁄ Symmetry transformations = 1Àx, Ày, 1 À z
0.904(19)
0.857(19)
2.274(19)
2.42(2)
3.0826(18)
3.1649(19)
148.7(17)
145.6(17)
⁄

6
2
S. Roy et al. / Polyhedron 75 (2014) 57–63
Fig. 4. Perspective view of complex 2. Only the relevant atoms are labelled.
Hydrogen atoms are not shown for clarity.
Fig. 6. Perspective view of complex 3. Only the relevant atoms are labelled.
Hydrogen atoms are not shown for clarity.
Table 4
Selected bond lengths (Å) and bond angles (°) of 2.
cadmium(II) centre is bonded to one imine nitrogen atom, one
amine nitrogen atom and one phenoxo oxygen atom {N(4), N(1)
and O(1) for Cd(1) and N(19), N(16) and O(2) for Cd(2)} of a triden-
Cd(1)–O(8)
Cd(1)–O(23)
Cd(1)–N(1)
Cd(1)–N(5)
Cd(1)–N(16)
Cd(1)–N(20)
Cd(2)–O(8)
Cd(2)–O(9)
2.2615(16)
2.2655(15)
2.427(2)
2.2736(18)
2.419(2)
2.2935(19)
2.2600(15)
2.5215(15)
2.2550(16)
2.5164(16)
2.187(2)
O(23)–Cd(1)–N(20)
N(1)–Cd(1)–N(5)
81.09(6)
78.75(6)
161.52(7)
93.31(7)
91.99(6)
124.66(6)
78.74(7)
65.89(5)
75.03(5)
138.83(5)
107.27(8)
118.70(7)
139.24(5)
154.54(5)
80.79(7)
86.08(7)
66.13(5)
123.18(7)
103.53(7)
84.10(7)
N(1) –Cd(1) –N(16)
N(1)–Cd(1)–N(20)
N(5)–Cd(1)–N(16)
N(5)–Cd(1)–N(20)
N(16)–Cd(1)–N(20)
O(8)–Cd(2)–O(9)
O(8)–Cd(2)–O(23)
O(8)–Cd(2)–O(24)
O(8)–Cd(2)–N(100)
O(8)–Cd(2)–N(103)
O(9)–Cd(2)–O(23)
O(9)–Cd(2)–O(24)
O(9)–Cd(2)–N(100)
O(9)–Cd(2)–N(103)
O(23)–Cd(2)–O(24)
O(23)–Cd(2)–N(100)
O(23)–Cd(2)–N(103)
O(24)–Cd(2)–N(100)
2 À
tate deprotonated Schiff base, (L ) , one terminal chloride {Cl(1)
for Cd(1) and Cl(2) for Cd(2)} and a phenoxo oxygen atom {O(2)
2
À
for Cd(1) and O(1) for Cd(2)} from a second (L ) ligand. Thus,
the two phenoxo oxygen atoms, O(1) and O(2) bridge two cad-
mium(II) centres and link the two halves of the dinuclear complex
about a pseudo-2-fold symmetry axis which lies normal to the al-
Cd(2)–O(23)
Cd(2)–O(24)
2 2
most planar Cd O ring. The bridging oxygen atoms form asym-
Cd(2)–N(100)
Cd(2)–N(103)
O(8)–Cd(1)–O(23)
O(8)–Cd(1)–N(1)
O(8)–Cd(1)–N(5)
O(8)–Cd(1)–N(16)
O(8)–Cd(1)–N(20)
O(23)–Cd(1)–N(1)
O(23)–Cd(1)–N(5)
O(23)–Cd(1)–N(16)
2.199(2)
74.80(5)
102.03(6)
81.76(6)
92.29(6)
metric linkages to the cadmium(II) centres with a range of Cd–O
distances, 2.199(2)–2.273(3) Å, and Cd(1)–O–Cd(2) bridging angles
of 105.59(9)° and 104.88(9)°. The geometry of a penta-coordinated
metal complex may conveniently be measured by the Addison
parameter (s) that is ideally zero for a square-pyramidal complex
and is one for a trigonal bipyramidal complex. In the present com-
151.94(6)
93.16(6)
153.05(6)
101.92(6)
plex, both cadmium(II) centres show distorted square-pyramidal
geometries with trigonality indices
for Cd(1)} and 0.007 {for Cd(2)} [
s
(Addison parameter) = 0.22
{
s
= ( and b
a
À b)/60 , where
a
are the two largest Ligand–Metal-Ligand angles of the coordination
sphere] [50]. The chlorides occupy the apical sites. The deviation of
Cd(1) from the mean square basal plane passing through the coor-
dinating atoms, O(1), O(2), N(1) and N(2) towards the apical donor
chloride is 0.7827(7) Å. Similarly, the deviation of Cd(2) from the
mean square basal plane passing through the coordinating atoms,
O(1), O(2), N(3) and N(4) is 0.7920(7) Å. The distance between the
two cadmium(II) centres is 3.5656(9) Å. Selected bond distances
and angles are gathered in Table 5. There are no significant supra-
molecular interactions in the structure.
3.3. Infrared, electronic and fluorescence spectra
À1
Three bands at 3357, 3313 and 3263 cm in the IR spectrum of
complex 1 may be assigned to the stretching vibrations of the NH
2
À1
and NMe
2
groups. A very strong band at 2042 cm is assigned to
the vibration of the bridging azide ligand [51]. In the IR spectra of
complexes 2 and 3, bands corresponding to the azomethine (C@N)
À1
stretching vibrations appear in the range 1627–1645 cm [52].
À1
The bifurcated bands at 2040 and 2061 cm in the IR spectrum
of complex 2 indicate the presence of terminal azides in slightly
Fig. 5. Intramolecular C–HÁ Á Á
p
interactions in complex 2.
different environments.

S. Roy et al. / Polyhedron 75 (2014) 57–63
63
Table 5
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O(1)–Cd(1)–N(4)
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