Synthesis, spectroscopic, crystal structures and photoluminescence studies of cadmium(II) complexes derived from di-2-pyridyl ketone benzoylhydrazone: Crystal structure of a rare eight coordinate cadmium(II) complex

Article abstract of DOI:10.1016/j.poly.2017.01.041

Four cadmium(II) complexes, [CdL₂] (1), [Cd(HL)Cl₂] (2), [Cd(HL)Br₂] (3) and [Cd(HL)(NO₃)₂(H₂O)] (4) of di-2-pyridyl ketone benzoylhydrazone (HL) have been synthesized and characterized by

Full text of DOI:10.1016/j.poly.2017.01.041

Accepted Manuscript
Synthesis, spectroscopic, crystal structures and photoluminescence studies of
cadmium(II) complexes derived from di-2-pyridyl ketone benzoylhydrazone:
Crystal structure of a rare eight coordinate cadmium(II) complex
Daly Kuriakose, A. Ambili Aravindakshan, M.R. Prathapachandra Kurup
PII:
S0277-5387(17)30078-5
DOI:
http://dx.doi.org/10.1016/j.poly.2017.01.041
POLY 12445
Reference:
To appear in:
Polyhedron
Received Date:
Revised Date:
Accepted Date:
23 November 2016
22 January 2017
25 January 2017
Please cite this article as: D. Kuriakose, A.A. Aravindakshan, M.R.P. Kurup, Synthesis, spectroscopic, crystal
structures and photoluminescence studies of cadmium(II) complexes derived from di-2-pyridyl ketone
benzoylhydrazone: Crystal structure of a rare eight coordinate cadmium(II) complex, Polyhedron (2017), doi: http://
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1
Synthesis, spectroscopic, crystal structures and photoluminescence
studies of cadmium(II) complexes derived from di-2-pyridyl ketone
benzoylhydrazone: Crystal structure of a rare eight coordinate
cadmium(II) complex
*
Daly Kuriakose, A. Ambili Aravindakshan, M.R. Prathapachandra Kurup
Department of Applied Chemistry, Cochin University of Science and Technology, Kochi
6
82 022, Kerala, India
Abstract
Four cadmium(II) complexes, [CdL
2
] (1), [Cd(HL)Cl
2
] (2), [Cd(HL)Br
2
] (3) and
[
Cd(HL)(NO (H O)] (4) of di-2-pyridyl ketone benzoylhydrazone (HL) have been
3
)
2
2
synthesized and characterized by different physico-chemical methods. The tetradentate
aroylhydrazone acts as a tridentate ligand in all the complexes, bonding through iminol or
amido oxygen, azomethine and pyridyl nitrogens. The molecular structures of all
monomeric complexes were determined by single crystal X-ray diffraction studies. The
complexes, [CdL
whereas the other two complexes [Cd(HL)Br
triclinic crystal system. The complex [CdL ] (1) has a distorted octahedral geometry with
two deprotonated monoanionic hydrazone moieties satisfying the coordination whereas in
Cd(HL)Cl ] (2) and [Cd(HL)Br ] (3), the pentacoordination around Cd(II) is satisfied by
neutral N, N, O - chelated hydrazone and two anions chloride and bromide respectively.
In [Cd(HL)(NO (H O)] (4), cadmium shows octacoordination and nitrate ion binds both
2
] (1) and [Cd(HL)Cl
2
] (2) got crystallized in a monoclinic space group
2
] (3) and [Cd(HL)(NO (H O)] (4) in a
3
)
2
2
2
[
2
2
3
)
2
2
in anisobidentate and bidentate fashion. The thermal stability and the nature of water
*
Corresponding author
E mail address: mrpcusat@gmail.com, mrp_k@yahoo.com (M.R. Prathapachandra Kurup)
Phone: +91-484-2862423
Fax: +91-484-2575804

2
molecule in complex [Cd(HL)(NO
3
)
2
(H
2
O)] (4) was studied. The nature of emission was
found to be quenched in all complexes.
Keywords: Aroylhydrazone; Chelation; Cadmium(II) complexes; Bifurcated; Crystal
structures
1. Introduction
Hydrazones and their metal complexes have been widely investigated by
researchers in the recent years due to their applications in diverse fields [1-6]. The
interest remains unwavering and was further fueled by the inherent ability of hydrazones
to exhibit tautomerism which in turn displays versatile coordination modes during
complexation. The reaction parameters such as nature and denticity of the hydrazone,
metal ion and its concentration and the pH of the medium [7,8] contributes to the
coordinating ability of hydrazone and resulting in diverse geometries and nuclearities [9-
1
0
1
1]. Among d metals, the heavy metal cadmium forms a plethora of complexes with
wide variety of coordination numbers ranging from four to eight [12]. Recently
cadmium(II) ion is also found to serve as the catalytic center in carbonic anhydrase [13].
1
0
Moreover the d metal ions also find potential applications as photoluminescence
materials and the nature of fluorescence can be of Chelation Enhanced Fluorescence
effect (CHEF) or Chelation Enhanced Quenching effect (CHEQ) or both effects coupled
with red or blue shift in emission band.
Extensive studies have been done on the transition metal complexes of di-2-pyridyl
ketone, a versatile polydentate ligand with three potential donor sites and the study began
since 1967, when the first Cu(II) complex of di-2-pyridyl ketone was reported by
Osborne and McWhinnie [14]. Transition metal complexes of di-2-pyridyl ketone
derived ligand systems have also gained considerable interest [9,15]. In this paper, we
report the syntheses as well as structural characterization of four cadmium(II) complexes
of di-2-pyridyl ketone benzoylhydrazone. The quenching nature in the emission spectra
of aroylhydrazone as well as complexes were also studied.

3
2. Experimental section
2
.1. Materials
All chemicals used were of analar quality and purchased from commercial
source. Di-2-pyridyl ketone (Aldrich), benzhydrazide (Aldrich), cadmium(II) acetate
dihydrate (E-Merck), cadmium(II) chloride (Aldrich), cadmium(II) bromide tetrahydrate
(
Aldrich) and cadmium(II) nitrate tetrahydrate (Qualigens) were used as supplied.
Solvents, methanol and DMF were purchased from Spectrochem and used without further
purification. The aroylhydrazone (HL), di-2-pyridyl ketone benzoylhydrazone was
synthesized according to the reported procedure [15].
2
2
.2. Synthesis of aroylhydrazone (HL) and its cadmium(II) complexes
.2.1. Synthesis of di-2-pyridyl ketone benzoylhydrazone (HL)
The aroylhydrazone, HL was prepared by refluxing equimolar methanolic
solutions of benzhydrazide (0.136 g, 1 mmol) and di-2-pyridyl ketone (0.184 g, 1 mmol)
for 4 hours along with two drops of conc. HCl. The resulting solution was kept aside for
slow evaporation at room temperature. Colorless crystals were obtained within a period
of 2-3 days. The product obtained was filtered and dried. Yield: 0.222 g (55%).
2
2
.2.2. Syntheses of cadmium(II) complexes
.2.2.1. Synthesis of [CdL ] (1)
Methanolic solutions of aroylhydrazone, HL (0.302 g, 1 mmol) and cadmium(II)
2
acetate dihydrate (0.267 g, 1 mmol) were mixed and refluxed for three hours. The
resulting yellow colored solution is allowed to stand for slow evaporation under room
temperature. Yellow crystals are obtained within a period of a week. The crystals were
then filtered off, washed with methanol and dried over P
4
O10 in vacuo (Scheme I).
For [CdL ] (1): Yield: 57% (0.407 g). Color: Yellow. Anal. Calc. for C36
2
H26CdN
8
O
2
-1
(
M.W.: 715.05 g mol ) C, 60.47; H, 3.66; N, 15.67. Found: C, 60.63; H, 3.6; N, 15.49%.
2
-1
λ
M
(DMF): 3.5 mho cm mol .

4
2
.2.2.2. Syntheses of [Cd(HL)Cl
2
] (2) and [Cd(HL)Br ] (3)
2
To the methanolic solution of aroylhydrazone, HL (0.302 g, 1 mmol), methanolic
solution of appropriate cadmium(II) salt (1 mmol) was mixed and the resulting yellow
colored solutions were refluxed for three hours. On cooling, yellow microcrystalline
product of the respective compounds formed were filtered off and washed with methanol
and dried. Single crystals suitable for X-ray analysis were obtained on recrystallization
from DMF solution of the crude yellow microcrystals of 2 and 3. The crystals were
filtered off, washed with methanol dried in vacuo over P O10 (Scheme 1).
4
For [Cd(HL)Cl
OCdCl
H, 2.83; N, 11.31%. λ
2
] (2): Yield: 71% (0.344 g). Color: Yellow. Anal. Calc. for
-1
C
18
H
14
N
4
2
(M.W.: 485.64 g mol ) C, 44.52; H, 2.91; N, 11.54. Found: C, 44.58;
2
-1
M
(DMF): 22 mho cm mol .
For [Cd(HL)Br
2
2
] (3): Yield: 77% (0.442 g). Color: Yellow. Anal. Calc. for
-1
C
18
H
14
N
4
OCdBr
(M.W.: 574.54 g mol ) C, 37.63; H, 2.46; N, 9.75. Found: C, 38.03; H,
2
-1
2
2
.73; N, 10.09%. λ
.2.2.3. Synthesis of [Cd(HL)(NO
To the ethanolic solution of aroylhydrazone, HL (0.302 g, 1 mmol), ethanolic
M
(DMF): 26 mho cm mol .
3
)
2
(H O)] (4)
2
solution of cadmium(II) nitrate tetrahydrate (1 mmol, 0.308 g) was added, mixed and
refluxed for three hours. On cooling, yellow block shaped single crystals suitable for X-
ray analysis were formed within a period of five days. The crystals were separated and
dried in vacuo over P
4
O10 (Scheme 1).
For [Cd(HL)(NO (H
3
)
2
2
O)] (4): Yield: 63% (0.351 g). Color: Yellow. Anal. Calc. for
-1
C
18
H16CdN
6
O (M.W.: 556.78 g mol ) C, 38.83; H, 2.90; N, 15.09. Found: C, 38.92; H,
8
2
-1
2
.93; N, 14.01%. λ
M
(DMF): 136 mho cm mol .
Scheme 1
2
.3. Physical measurements
The elemental analyses of the aroylhydrazone and its cadmium(II) complexes
were carried out using a Vario EL III CHNS analyzer. FT-IR spectra of the compounds
-
1
were recorded on a JASCO - 4100 FT-IR Spectrophotometer in the range 4000-400 cm
using KBr pellets. Electronic spectra in DMF solutions were recorded on a Thermo

5
scientific evolution 201 UV-Vis double beam spectrometer in the 200-800 nm range.
The emission properties were studied using Shimadzu RF-5301PC spectrometer
(
solution). The TG-DTG analysis of the complex 4 was carried out in a Perkin Elmer
-1
Pyris Diamond TG/DTA analyzer under nitrogen at a heating rate of 10 °C min in the
-3
5
0-700 °C range. The molar conductivities of the complexes in DMF (10 M) solutions
at room temperature were measured using a Systronic model 303 direct reading
conductivity bridge.
2
.4. Crystallographic data collection and refinement
1
1
Single crystals of the compounds [CdL
2
] (1), [Cd(HL )Cl
2
] (2), [Cd(HL )Br
2
]
(
3) and [Cd(HL)(NO (H O)] (4) with suitable dimensions were selected for X-ray
3
)
2
2
diffraction measurements and mounted on a Bruker SMART APEXII CCD
diffractometer, equipped with a graphite crystal, incident-beam monochromator and a
fine focus sealed tube with Mo Kα (λ = 0.71073 Å) radiation as the X-ray source. The
unit cell dimensions were measured and the data collection was performed. The
programs SAINT and XPREP were used for data reduction and APEX2 and SAINT were
used for cell refinement [17]. Absorption corrections were carried out using SADABS
based on Laue symmetry using equivalent reflections [18]. The structure was solved by
using SHELXS-97 direct methods and refined by full-matrix least-squares refinement on
2
F using SHELXL-2014/7 [19] as well as WinGX software package [20]. The molecular
and crystal structures were plotted using ORTEP-3 [20] and DIAMOND version 3.2g
[
21].
In complex 1, one of the four pyridyl rings was disordered over five closely
positioned sets of sites (N2/C8/C9/C10/C11) with a site-occupation factor of 0.684(19)
for the major-occupied and 0.316(19) for the minor-occupied sites. The hydrogens in
pyridine ring and its disordered counterpart were fixed using HFIX instruction. The
distances were restrained to be equal using SADI instruction. The connectivity array and
planarity were restrained using DELU and FLAT instructions. In all cadmium(II)
complexes, anisotropic refinement were performed for all non-hydrogen atoms and all H
atoms on C were placed in calculated positions, guided by difference maps, with C–H

6
bond distances 0.93–0.96 Å. H atoms were assigned as Uiso=1.2Ueq (1.5 for Me). In
1
1
[
Cd(HL )Cl
H4′ attached to N4 was located from Fourier map and restrained to a distance of
.88±0.01. The hydrogen atoms, H8A and H8B attached to the oxygen atom O8 of the
2
] (2), [Cd(HL )Br
2
] (3) and [Cd(HL)(NO
3
)
2
(H O)] (4) the hydrogen atom
2
0
coordinated water molecule in 4 were located from difference map and their distances
and angles were restrained using DFIX and DANG instructions with distance restraint of
O–H = 0.86±0.01 Å and H···H = 1.36±0.02 Å followed by refinement of their
displacement parameters. Some reflections were omitted for all complexes owing to bad
disagreement. The extinction coefficient have value of 0.02389 in complexes 2. The
crystallographic data and structure refinement parameters for compounds 1-4 are given in
Table 1.
Table 1
3
.
Results and discussion
Four cadmium(II) complexes of tetradentate di-2-pyridyl ketone
benzoylhydrazone (HL) were synthesized and characterized by elemental analysis and
1
molar conductivity measurements, IR, electronic and H-NMR spectral studies. The
reaction of cadmium(II) salts with aroylhydrazone in appropriate solvent yielded
monomeric complexes 1-4. In all the complexes, the HL acts as a tridentate NNO donor
ligand bonding through iminol and amido oxygen, azomethine nitrogen and one of the
pyridyl nitrogen thereby leaving a free potential donor site available for the coordination.
The molecular structures of complexes 1-4 were determined by single crystal X-ray
diffraction studies and the coordination geometries of the cadmium(II) center in
complexes were found to possess varying topologies like square pyramidal (2 and 3),
octahedral (1) and triangulated dodecahedral (4) accomplished by the reaction of
aroylhydrazone with different metal salts. The thermal stability as well as presence of
coordinated water molecule in complex 4 was confirmed by TG analysis. The
photoluminescent behavior of all complexes was also investigated.

7
All the cadmium(II) complexes prepared are stable towards air and moisture at
room temperature. They are insoluble in water, methanol and ethanol but soluble in
dipolar aprotic solvents like DMF and DMSO. The partial elemental analyses for the
complexes are in good agreement with the given molecular formulae, which was further
authenticated by single crystal X-ray diffraction studies. The molar conductivity
-3
measurements of ligand as well as complexes were measured in DMF (10 M) at room
temperature. The values suggest that the ligand as well as complexes except 4 are non-
electrolytic nature and remain un-dissociated in DMF [22]. The high molar conductivity
2
-1
value of 136 mho cm mol corresponds to the 1:2 electrolytic nature of complex 4 and
be attributed to a partial dissociation and/or partial replacement of the anion in the solvent
molecules [22,23].
3
.1. Description of crystal structures
.1.1a. Molecular structure of [CdL ] (1)
The molecular structure of [CdL ] (1) is depicted in Fig. 1 along with the atom
numbering scheme and selected bond lengths (Å) and bond angles (°) are shown in Table
. The monomeric bis-ligated complex crystallized in P2 /c space group with four
crystallographic identical molecules occupying the monoclinic unit cell. The
chromophore
3
2
2
2
1
hexacoordination around Cd(II) ion can be best described with a CdN
4
O
2
comprising of two equivalent mono-anionic ligands (Fig. 1).
Fig. 1
The Cd atom is coordinated by azomethine nitrogens (N3 and N7), iminolate
oxygens (O1 and O2) and one of the two pyridyl nitrogens (N1 and N5) from each aroyl
hydrazone molecule. The oxygen atom of the aroylhydrazone ligand coordinates the
metal atom in iminolate form through iminolization followed by deprotonation confirmed
by the double bond nature of Nimine=C (1.328(4) in C12–N4 and 1.342(4) Å in C30–N8
bonds) and single bond nature of C–Oiminolate (1.269(3) in C12–O1 and 1.265(3) Å in
C30–O2 bonds) bond lengths (Table 2) [24,25]. The torsion angles [C5–C6–N3–N4, -
1
80.0(2)°; C23–C24–N7–N8, -179.5(2)°; N3–N4–C12–O1, 3.3(4)°; and N7–N8–C30–
O2, -0.5(4)°] observed support the formation of E, Z isomer (trans, cis isomer) of the

8
iminolic form of the ligand along C6=N3 and C24=N7 respectively facilitating the
coordination of deprotonated aroylhydrazone to the cadmium(II) center.
The two monodeprotonated aroyl hydrazone coordinates to the cadmium center
forming four fused five membered chelate rings with intraligand bite angles more acute in
the range 68-70° (N1–Cd1–N3, 69.86(9)°, N3–Cd1–O1, 69.88(8)°, N7–Cd1–N5,
6
8.73(8)° and N7–Cd1–O2, 69.46(8)°) and the bicyclic chelate system (Cd1, N1, C6, N3,
N4, C12, O1) possess a dihedral angle of 85.473(43)° with its counterpart (Cd1, N5, C23,
C24, N7, N8, C30, O2) suggesting non-coplanarity. Each pair of five membered chelate
rings formed by the coordination of aroylhydrazone with the metal center possess a
dihedral angles of 2.01(11) and 5.92(11)° between each other which shows the rigidity of
the bonds as well as non-coplanar nature of metallocycles during complexation. The
distortion from the ideal octahedral geometry can be viewed from the large deviation of
trans and cis angles (155.76(9)° and 69.46(8)° respectively) formed around metal center.
The bond distances to cadmium are in the order Cd–N(azo) < Cd–O(iminolate) < Cd–N(py).
The shortest coordinate bonds are to central imine N donors [N(3)–Cd(1), 2.282(2);
N(7)–Cd(1), 2.295(2)] and iminolate oxygens O(1)–Cd(1), 2.239(2); O(2)–Cd(1),
2
2
.254(2)] and while those to pyridyl nitrogens [N(1)–Cd(1), 2.364(3); N(5)–Cd(1),
.410(3)] are significantly weaker.
Ring puckering analyses and least square plane calculations show that the two pairs
of fused five-membered chelate rings surrounding the cadmium(II) center are puckered.
The five membered metallocycle Cg(1) (comprises of Cd1, O1, C12, N4 and N3), Cg(2)
(
comprises of Cd1, O2, C30, N8 and N7), Cg(3) (comprises of Cd1, N1, C5, C6 and N3)
and Cg(4) (comprises of Cd1, N5, C23, C24 and N7) are puckered [26] with puckering
parameters, Q(2) = 0.085(2) Å, φ(2) = 342.8(19)° for Cg(1), Q(2) = 0.085(2) Å, φ(2) =
3
59(2)° for Cg(2), Q(2) = 0.088(3) Å, φ(2) = 139(19)° for Cg(3) and Q(2) = 0.093(2) Å,
φ(2) = 198.8(19)° for Cg(4). The six membered pyridine ring Cg(6) (comprises of N2,
C7, C11, C10, C9 and C8) and the disordered counterpart Cg(9) (comprises of N2A, C7,
C11A, C10A, C9A and C8A) are also puckered with puckering parameters, Q(2) =
0
.070(12) Å, φ(2) = 304(14)° for Cg(6), Q(2) = 0.20(3) Å, φ(2) = 305(8)° for Cg(9). The
puckering of five membered metallocycles were also calculated in terms of
pseudorotation parameter P and τ [27] and it was found that the metallocycles Cg(1) and
m

9
Cg(4) adopt twisted conformation on N3–Cd1 and N5–Cd1 bonds respectively with
pseudorotation parameter P = 136.5(16)º and τ = 7.2(2)º for Cd1–O1 bond in Cg(1) and P
=
9.2(16)º and τ = 8.0(2)º for Cd1–N5 bond in Cg(4). The metallocycles Cg(2) and Cg(3)
adopt as an envelope on Cd1 for Cg(2) with P = 165.0(17)º and τ = 7.0(2)º for reference
bond Cd1–O2 and N3 for Cg(3) with P = 287.8(11)º and τ = 9.9(3)º for reference bond
Cd1–N1. Conformational analyses [28] shows the five membered metallocycles Cg(1)
and Cg(4) adopts T-form (half chair) conformation whereas Cg(2) adopts E-form
(
envelope) conformation.
Table 2
3
.1.1b. Molecular structures of [Cd(HL)Cl
2
] (2) and [Cd(HL)Br ] (3)
2
The molecular structures of the complexes [Cd(HL)Cl
2
] (2) and [Cd(HL)Br ] (3)
2
along with the atom numbering scheme are shown in Figs. 2 and 3 and significant bond
distances and bond angles are shown in Table 2. X-ray diffraction studies reveal that
both compounds are isostructural species whose structural geometry is defined as
distorted square pyramidal around Cd(II) centre coordinated by pyridyl nitrogen N1,
azomethine nitrogen N3, amido oxygen atom O1 of the aroylhydrazone moiety and two
anions (Cl(1) and Cl(2) for 2 and Br(1) and Br(2) for 3).
Figs. 2 and 3
The complex [Cd(HL)Cl
2
] (2) crystallizes with four crystallographic identical
/n space group whereas
] (3) crystallizes in triclinic space group P1 with two molecules in the unit
cell. The structural studies of the halide complex reveals that the distances of Cd–N
average 2.3675(3) Å) and Cd–O (2.444(3) Å) in complex 3 are slightly longer than that
of complex 2 (2.3589(10) Å and 2.3896(17) Å. It may be attributed to the ligand field
molecules occupying the monoclinic unit cell with P2
1
ꢀ
[
Cd(HL)Br
2
(

1
0
strength of halide ligand (Br < Cl) [29]. The C(12)–O(1) bond length is found to be
.231(3) Å in 2 and 1.228(4) Å in 3 which is very close to formal C=O length of 1.23 Å
confirms the coordination of aroyl hydrazone, HL to the central metal via amido form
Table 2) [30]. The slight variation in C6=N3 and N3–N4 bond lengths in complexes as
1
(
compared to the aroylhydrazone attributed to the extensive delocalization over
aroylhydrazone moiety during complexation. The bond distances to cadmium are in the
order Cd–N(azo) < Cd–N(py) < Cd–O(ketoxy) for both complexes 2 and 3. The
difference between the Cd–Xanion bond distances are 0.0205 and 0.0366 Å for complexes
2
and 3 respectively. The torsion angle values of -179.0(2)° in 2 and 175.9(3)° in 3
observed for C5–C6–N2–N3 moiety supports the E isomer of the amido form of the
principle ligand on coordination. The distortion in the five coordinated systems is
expressed with trigonality index (Addison’s parameter) τ = (β-α)/60 [31] (for perfect
square pyramidal and trigonal bipyramidal geometries the values of τ are zero and unity
respectively). The τ values of 0.0735 and 0.0507 in [Cd(HL)Cl
2
] (2) and [Cd(HL)Br
2
]
(
3) respectively indicates that the irregular coordination geometry of the complexes 2 and
3
in the solid state is 7.35% and 5.07% along the pathway of distortion from square
In both complexes 2 and 3, the neutral
pyramidal to trigonal bipyramidal.
aroylhydrazone coordinates to the cadmium center forming two sets of five membered
metallocycles with more acute intraligand bite angle values of 67.57(7) (N1–Cd1–N3)
and 66.68(6)° (N3–Cd1–O1) for 2 and 67.38(9) (N1–Cd1–N3) and 66.01(9)° (N3–Cd1–
O1) for 3 displaying distortion in the coordination geometry. The dihedral angle values
of 3.36(9) and 8.66(16)° in 2 and 3 respectively formed between two five-membered
chelate rings fused along the Cd1–N3 junction during complexation shows the non-
coplanar nature of metallocycles.
Cremer and Pople ring puckering analysis [26] shows that in complex 2, the five
membered metallocycle Cg(2) (comprises of Cd1, N1, C5, C6 and N3) is puckered with
Q(2) = 0.1221(19) Å and φ(2) = 207.1(10)° for Cg(2) whereas in complex 3, both the
metallocycles Cg(1) and Cg(2) (comprises of Cd1, N1, C5, C6 and N3) are puckered with
Q(2) = 0.237(6) Å and φ(2) = 172.325(7)° for Cg(1) and Q(2) = 0.244(6) Å and φ(2) =
3
12.6(10)° for Cg(2). The pseudorotation parameter P and τ , parameters [27] were also
m

1
1
calculated for both complexes and it was found that the metallocycle Cg(2) adopts an
envelope on N1 with P = 20.9(9)º and τ = 11.6(1)º for reference bond Cd1–N1 in 2
whereas in 3, metallocycle Cg(1) adopts an envelope conformation on Cd1 with P =
3
31.8º and τ = 19.1º for reference bond Cd1–O1 and Cg(2) adopts a twisted form on N3–
C6 bond with P = 102.1º and τ = 27.7º for reference bond Cd1–N1.
3
.1.1c. Molecular structure of [Cd(HL)(NO
3
)
2
(H
2
O)] (4)
(H
The molecular structure of [Cd(HL)(NO
3
)
2
2
O)] (4) is depicted in Fig. 4 along
with the atom numbering scheme and selected bond lengths (Å) and bond angles (°) are
ꢀ
shown in Table 2. The monomeric eight coordinated complex crystallizes in P1 space
group with two molecules in the unit cell. The coordination geometry around the Cd(II)
centre is distorted triangulated dodecahedra [32] defined by neutral tridentate HL ligand
through pyridyl nitrogen, azomethine nitrogen and amido oxygen atoms, one water
molecule and two nitrate ions in which one nitrate is anisobidentately coordinated
through oxygen atoms and other is bidentately coordinated [33,34].
Fig. 4
The hydrazone ligand in an N,N,O-fashion and O2 donor set of bidentately
coordinated nitrate occupies the equatorial coordination plane whereas the oxygen atoms
of solvent water as well as anisobidentate nitrate ion occupy the apical positions and
completes the coordination geometry. All the distances around the cadmium atom are in
the expected ranges for octacoordinated cadmium in distorted triangulated dodecahedral
arrangement, although the inter-axial and equatorial angles around the metal differ from
the ideal values of 180° and 72° respectively (Table 2). In the complex 4, three of the
five equatorial angles are smaller than the ideal value and the other two angles are greater
showing the degree of distortion from the ideal polyhedron. The sum of the equatorial
angles is very close to the ideal value (360°), which ensures the planarity of the equatorial
plane. The axial O6–Cd1–O8 and O5–Cd1–O8 bond angles of 157.45(10)°and
1
54.40(10)° indicates deviation from a linear configuration. Based on criteria for

1
2
assigning nitrate binding modes proposed by Kleywegt et al. nitrate ion can bind to the
central metal atom via monodentate, where only one oxygen atom bound to the metal,
bidentate mode where nitrate coordinate through two oxygen atom with nearly same M–
O distances or in aniso bidentate fashion, in which among two oxygen atoms bind to
central metal atom one is significantly longer [34,35] (Fig. 5 and Table 3).
Fig. 5 and Table 3
The bidentate and anisobidentate coordination modes of nitrate ion in complex 4
were authenticated by differences in M–O, M–N bond distances and M–N–O bond
angles. The Cd–Nimine and Cd–NPy bond lengths are found to be 2.384(2) and 2.344(2) Å
respectively and are comparable to the same in the literature.
The C(12)–O(1) bond length (1.229(3) Å) is very close to formal C=O length of
1
.23 Å confirms the coordination of principal ligand, HL to the central metal via amido
form (Table 2) [30]. The extensive delocalization over aroylhydrazone moiety during
complexation as compared to the aroylhydrazone was supported by the slight variation in
C6=N3 and N3–N4 bond lengths in complex. The torsion angle value of 177.6(2)° in 4
observed for C5–C6–N3–N4 moiety supports the E isomer of the amido form of HL on
coordination. The more acute intraligand bite angle values of 67.71(7) (N1–Cd1–N3)
and 66.79(7)° (N3–Cd1–O1) was observed for 4. The neutral aroyl hydrazone
coordinates to the cadmium center forming a pair of five membered metallocycles fused
along the Cd1–N3 junction with dihedral angle of 1.88(5)°.
3
.1.2. Supramolecular aspects in the complexes 1-4
Although there are no classical hydrogen bonds found in the complex [Cd(L) ] (1),
2
the crystal packing is supported by non-classical intra and intermolecular hydrogen
bonding interactions (Table S1, Fig 6). The intramolecular hydrogen bonds C22–
H22···N6 and C4–H4···N4C22, adds to the rigidity of the molecular structure. The
iminolate oxygen atoms, O1 and O2 acts a hydrogen bond acceptors in C15–H15···O2
and C27–H27···O1 hydrogen bonding interactions for associating adjacent complex

1
3
motifs to form a layer type structure arranged in particular direction when viewed along
ꢂ
crystallographic ‘b’ axis. The C15–H15···O2 interaction generates a ꢁ (16) motif. This
ꢂ
layered structures is linked each other through C20–H20···N4 with H···A distance of
ꢂ
2
.48 Å to form supramolecular ꢁ (14) network.
ꢂ
Fig 6
The interaction parameters are listed in Table S2. In the unit cell, the molecules are
packed in the lattice in a zig-zag manner along the ‘a’ axis (Fig. S1) and the packing is
stabilized by non-covalent interactions viz, π···π and intermolecular C–H···π interactions
(
Table S2, Figs. 7 and 8). The five membered metallocycle, Cg(1) (comprises of Cd(1),
O(1), C(12), N(4), N(3)) is engaged in π···π interaction with six membered aromatic ring
Cg(9) (comprises of C(13), C(14), C(15), C(16), C(17), C(18)) with a distance of
3
.868(2) Å. The five membered metal chelate ring Cg(3) (comprises of Cd(1), O(1),
C(12), N(4), N(3)) and one of the pyridine ring Cg(5) (comprises of N(1), C(1), C(2),
C(3), C(4), C(5)) also participates in π···π interactions with Cg(4) (comprises of C(13),
C(14), C(15), C(16), C(17), C(18)) and Cg(5) of the neighboring units at distances of
3
.3049(15) and 3.704(2) Å respectively. The Cg(1) is involved in C–H···π interaction
with the hydrogen atom H19 attached to C19 of one of the pyridine ring of the
aroylhydrazone moiety. The hydrogen atoms, H1 and H3 attached to the carbon atoms
C1 and C3 of the pyridine part of the aroylhydrazone moiety interacts with metallocycle
Cg(2) (comprises of Cd(1), O(2), C(30), N(8), N(7)) and pyridine ring Cg(7) (comprises
of N(5), C(19), C(20), C(21), C(22), C(23)) adjacent molecules through C1–H1···Cg(2)
and C3–H3···Cg(7) interactions.
Figs. 7 and 8
In complex [Cd(HL)Cl ] (2), the packing diagram shows an ordered arrangement
2
of molecules connected via a network of bifurcated hydrogen bonds in which N4 acts as
hydrogen bond donor for N2 (N4–H4′···N2) and Cl1 (N4–H4′···Cl1) acceptors (Table S1
Fig. 9). The N(4)–H(4')···N(2) hydrogen bond results in S(6) motif. In addition to the

1
4
aforementioned S(6) motif, an intermolecular N(4)–H(4')···Cl(1) (Symmetry code: -x+1,-
y,-z+2) interaction is observed which generates a hydrogen bonded inversion dimer with
ꢂ
an ꢁ (10) motif [36]. The crystal packing is also augmented by non-classical
ꢂ
intermolecular hydrogen bonding interactions like C3–H3···O1 and C10–H10···Cl2
(
Table S1). These classical and non-classical intra and inter molecular hydrogen bonding
interactions contributes to the three dimensional supramolecular architecture of the
complex.
Fig. 9
Similarly in [Cd(HL)Br ] (3), the amide proton N4 is in close proximity to the
2
nitrogen atom N2 of the uncoordinated pyridine ring and participates in a classical
intramolecular hydrogen bond of the type N–H···N resulting in an S(6) motif. The non-
classical (C18–H18···O1) hydrogen bonding interactions generated S(5) motif also
supports the packing of molecules (Table S1 Fig. 10).
Fig. 10
The non-covalent π···π as well as Cd(1)–Cl(1)···Cg(4) (symmetry coordinates 1-
x,1-y,1-z) interactions in complex 2 reinforce the packing of complex whereas in 3, only
π···π interactions contributes to the packing of molecules (Table S2). The five membered
metallocycle, Cg(1) (comprises of Cd(1), O(1), C(12), N(4), N(3)) is engaged in π···π
interaction with Cg(1) of another complex motif with a distance of 3.6814(11) Å (Fig.
S2). The six membered Cg(3) (comprises of N(1), C(1), C(2), C(3), C(4), C(5)) pyridine
ring participates in π···π interaction with Cg(5) (comprises of C(13), C(14), C(15), C(16),
C(17), C(18)), (centroid separation 3.8498(16)) aromatic part of aroylhydrazone moiety
of complex motif (Fig. S2). One of the chloride ion, Cl1 attached to the cadmium center
interacts with uncoordinated pyridine ring Cg(4) (comprises of N(2), C(7), C(8), C(9),
C(10), C(11)), through Cd–Cl···π interaction of the neighboring unit thereby stabilize
packing of the molecule (Fig. 11 and Table S2).
Fig. 11

1
5
In [Cd(HL)Br ] (3), the six membered ring Cg(3) (comprising of atoms N(1), C(1),
2
C(2), C(3), C(4), C(5)) is involved in π···π interaction with Cg(3) as well as aromatic six
membered ring Cg(5) (comprising of atoms C(13), C(14), C(15), C(16), C(17), C(18)) of
the neighboring units.
The packing of molecules in [Cd(HL)(NO
3
)
2
(H O)] (4) is enriched by classical
2
and non-classical intra and inter molecular hydrogen bonding interactions. The classical
N4–H4'···N2 and non-classical C1–H1···O4 interactions enhance the rigidity of the
complex motif. The intramolecular hydrogen bond is observed between amide proton
and nitrogen atom of the uncoordinated pyridyl ring. The hydrogen atoms, H8A and
H8B of the coordinated water molecule are involved in the hydrogen bonding
interactions. The hydrogen atom, H8A attached to the O8 of the coordinated water
participates in the trifurcated hydrogen bonding interaction with three acceptors, O7, O6
and N6. The strong intermolecular hydrogen bonds lead to 1D supramolecular
architecture propagating along ‘a’ axis (Table S1 & Fig 12). This 1D supramolecular
architecture develops in to 3D via non classical hydrogen bonds. In addition to this,
hydrogen bonding interations and N(5)–O(3)···Cg(1) interactions are also found in the
complex (Table S2 & Fig. S5).
Fig 12
3
.2. Thermogravimetric studies
Thermogravimetric analyses of the complexes gave information concerning the
thermal stability and the nature of water molecules in the complex [37,38].
The thermal decomposition pattern of complex 4 is shown in Fig. S5. The thermal
stability of complex 4 was investigated by TG/DTA measurements and the curves were
-1
obtained at a heating rate of 10 °C min in air atmosphere over the temperature range of
-800 °C. The complex 4 is stable upto 114 °C since there is no weight loss observed.
0
The thermal decomposition pattern can be ascribed to three weight losses. The first
weight loss of 3.26% (Calcd. 3.23%) observed between 114-172 °C indicating the
endothermic removal of one coordinated water molecule from the compound. The

1
6
second stage decomposition starts from 173 °C and ends at 312 °C with DTA
endothermic peak at 188 °C. It corresponds to the loss of organic moiety of the complex
and two molecules of nitrogen dioxide (weight loss of 68.25 (Calcd. 73.19%)) from the
complex. The third weight loss observed between 386 °C and 685 °C corresponding to
removal of one molecule of oxygen (weight loss of 10.55 (Calcd. 11.08%)) leaving CdO
as metallic residue.
3
.3
IR spectra
The tentative assignments of the significant IR spectral bands of aroylhydrazone,
HL and its cadmium(II) complexes are displayed in the Table S3. A comparison of the
IR spectra of hydrazone and metal complexes shows that significant variations have
occurred in the characteristic frequencies upon complexation. The spectrum of
-1
aroylhydrazone exhibits bands at 3448 (broad and medium) and 1691 cm which can be
assigned to ν(N–H) and ν(C=O) stretching vibrations respectively. The absence of ν(N–
H) stretching mode in the spectrum of complex 1 suggests that the ligand loses this
proton on complexation, thus act as a monoanionic deprotonated ligand [30,39].
-1
Interestingly in complexes 2-4, the presence of broad bands in the range 3450-3300 cm
-1
along with sharp bands in the region 1600-1650 cm corresponding to the persistence of
ν(N–H) and ν(C=O) stretching vibrations indicates that the aroylhydrazone, HL is
coordinated in the neutral amido form in these complexes [40,41]. In complex 1, the
absence of ν(C=O) stretching vibration confirms the coordination through iminolate
-1
oxygen [42]. The presence of a band at 1509 cm for the complex 1 is assigned to newly
formed ν(C═N) after iminolization [39,43]. The shift in ν(C═N) stretching frequency
-1
-1
observed at 1580 cm in the ligand to 1551, 1520, 1590 and 1509 cm for complexes 1,
, 3 and 4 respectively [44] supports coordination via azomethine nitrogen. It is also
2
-1
evident from shift in ν(N–N) bands in the region 1152-1133 cm . Variations in ring
-1
breathing vibrations of pyridine ring bands in the range 1470-1420 cm confirms
involvement of the pyridine nitrogen in coordination as indicated by the variations
observed in the ring breathing vibrations of pyridine ring and the in-plane ring
-1
deformation band of pyridine in the range 807-690 cm .

1
7
In the IR spectrum of the complex 4, the nitrato group stretching vibrations were
-1
observed at 1463, 1292 and 1032 cm [45]. These three stretching modes suggest that
nitrate ions coordinate to the metal as a bidentate ligand. This was further substantiated
by X-ray structure analysis which shows that one nitrate ions bind to Cd(II) as bidentate
chelating ligands and the other nitrate ion as an anisobidentate ligand.
3
.4
NMR spectra
1
The H NMR assignment for the hydrazone ligand HL and its Cd(II) complexes
were recorded in DMSO. In aroyl hydrazone HL, the signal at 15.15 ppm is ascribed to
the proton attached to the nitrogen (N4). In complexes 2-4, the upfield shift of this signal
was observed at 15.13-14.98 ppm corresponding to proton attached to N4 which in turn
supports the coordination of aroylhydrazone to the metal ion in amido form. The
intensity of these signals is also found to be decreased considerably on D O exchange
2
confirmed the above assignment [8]. Aromatic protons are observed as multiplets in the
4
range 8.96-7.25 ppm. Complex 1 do not show any signal corresponding to N–H
revealing that the ligand adopts iminol form, followed by deprotonation prior to
coordination with metal ion.
3
.5 Electronic spectra and photolumniscence properties
The electronic spectral assignments of hydrazone and the its cadmium(II)
complexes in DMF solution are summarized in Table S4. The electronic spectrum of the
aroylhydrazone shows two absorption band maxima at 324 and 277 nm arising due to
π→π transitions. The spectra of complexes 1-4 show bands at 269, 271, 269 and 268 nm
respectively [46,47] and these bands are ligand centered arising due to intraligand
transitions and suffered considerable shift in intensity and wavelength on coordination.
The band at 391, 393, 392 and 391 nm for complexes 1-4 corresponds to charge transfer
transitions [48].
The photolumniscence properties of the aroylhydrazone as well as cadmium(II)
-5
complexes were studied in DMF (10 M). On excitation at 310 nm, the aroylhydrazone

1
8
shows emission at 412 nm. Upon complexation, the photoluminescence intensities of
metal complexes are changed with respect to that of ligand. The observed excitation
maxima for ligand at 412 nm was shifted to 425, 430, 426 and 427 nm for complexes 1,
2
, 3 and 4 respectively upon binding to the transition metal ion (λex 360 nm) (Fig. 13).
Fig. 13
1
0
Due to the difficulty in oxidizing or reducing d configuration, no emission
arising from metal centered excited states of LMCT or MLCT are expected. High
similarity in the locations and profiles of emission peaks of the metal free ligands and
complexes allows to attributes the emission of these complexes to intraligand (n→π* and
π→π*) transitions within the hydrazone derivative. Cadmium(II) complexes in general
can enhance or quench the fluorescence emission of organic ligand. The poor overlap of
the metal orbitals with the orbitals of the ligand N-donors of the chelate ring causes the
ligand electron pairs which are located in higher energy orbitals more available for
quenching the fluorescence. The decrease in the emission intensities and enhancement of
luminescence emission maxima may be due to energy transfer possible from the excited
state of the ligand to metal ions thus increasing the non-radiative transitions of the ligand
excited state and decreasing the fluorescence intensity [49,50].
Conclusion
In the present paper we have discussed the synthesis, spectral and structural
characterization of four new cadmium complexes of di-2-pyridyl ketone
benzoylhydrazone. The reaction of aroylhydrazone comprising of flexible coordinating
NNO framework (amido/iminol forms) with different metal salts generated mononuclear
complexes with diverse distorted coordination geometries like square pyramidal (2 and
3
), octahedral (1) and triangulated dodecahedral (4). The amido-iminol tautomerism
enables the proligand coordinating via deprotonated iminol form in [CdL ] (1) and
neutral amido form in [Cd(HL)Cl ] (2), [Cd(HL)Br ] (3) and [Cd(HL)(NO (H O)] (4).
By changing the counter ion the coordination type of the aroyl hydrazone and geometry
2
2
2
3
)
2
2

1
9
around the Cd(II) center can be varied. In [Cd(HL)(NO
appears in anisobidentate as well as bidentate fashion. The thermal behaviour studies of
complex [Cd(HL)(NO (H O)] (4) shows that the complex was stable upto 110 °C. The
3
)
2
(H
2
O)] (4), the nitrate ion
3
)
2
2
photolumniscence properties of the aroylhydrazone as well as cadmium(II) complexes
were studied. The influence of hydrogen bonding and weak non covalent forces
augmenting the crystal packing were also investigated. The crystal packing was
stabilized by intra and intermolecular hydrogen bonds. The photoluminsence studies of
the aroylhydrazone HL and its cadmium complexes show quenching.
Supporting Information
The tables and figures including hydrogen bonding and non-bonding interactions,
IR and UV-Vis were included.
Acknowledgments
DK acknowledges UGC, New Delhi, India for the award of a Junior Research
Fellowship. AAA acknowledges CSIR for the award of a Senior Research Fellowship.
The authors are thankful to the Sophisticated Analytical Instrumentation Facility, Cochin
1
University of Science and Technology, Kochi, India for elemental analyses, H-NMR and
TG-DTG analyses and single crystal X-ray diffraction measurements. We also thank the
School of Environmental studies, Cochin University of Science and Technology, Kochi,
India for the photoluminescence studies.
Appendix A. Supplementary data
Crystallographic data for the structural analysis has been deposited with the Cambridge
Crystallographic Data Center as CCDC 1509951, 1509994, 1509993 and 1509995 for the
complexes [CdL
2
] (1), [Cd(HL)Cl
2
] (2), [Cd(HL)Br
2
] (3) and [Cd(HL)(NO
3
)
2
(H O)] (4)
2
respectively. Copies of this information may be obtained free of charge via
www.ccdc.cam.ac.uk/conts/retrieving.html or from the Director, CCDC, 12 Union Road,
Cambridge, CB2, 1EZ, UK (fax: +44-1223-336-033; e-mail: deposit@ccdc.cam.ac.uk.).

2
0
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2
3
O
N
N
N
Cd
N
N
N
N
O
N
Cd(OAc) 2H O
2
2
CH OH
3
3
h.
N
O
HN
Cd(NO ) 4H O
3
2
2
CdX2
C H OH
N
2
5
CH OH
3 h.
3
3
h.
O
N
HL
O
N
O
O
X
N
X
O
O
O
N
Cd
Cd
OH2
O
N
N
NH
N
N
N
4
2
and 3
X=Cl or Br
Scheme 1. Synthesis of cadmium(II) complexes 1, 2, 3 and 4.

2
4
Table 1. Crystallographic data and structure refinement for 1, 2, 3 and 4
[
Cd(L)
2
] (1)
[Cd(HL)Cl
2
] (2)
[Cd(HL)Br
2
3 2 2
] (3) [Cd(HL)(NO ) (H O)] (4)
Parameters
Empirical formula
Formula weight
Temperature (T K)
Crystal system
Space group
C
36
H
26CdN
8
O
2
C
18
H
14CdCl
2
N
4
O
C
18
H
14CdBr
2
N
4
O
C
18
H
16CdN
6
O
8
715.06
293(2) K
Monoclinic
P2 /c
485.64
293(2) K
Monoclinic
P2 /n
574.54
556.78
293(2) K
Triclinic
296(2) K
Triclinic
ꢀ
P1
1
1
P1
Cell parameters
a
b
c
α
β
γ
11.0769(4) Å
11.1238(3) Å
26.7736(9) Å
90°
9.3428(4) Å
8.7232(4) Å
9.9885(6) Å
8.2232(5) Å
13.4557(8) Å
14.7105(7) Å
90°
10.1525(7) Å
13.7080(11) Å
70.886(3)°
12.1936(11) Å
104.589(3)°
98.629(2)°
108.261(2)°
945.62(11)
2
98.6850(10)°
90°
93.8480(10)°
90°
77.467(3)°
83.342(3)°
3
Volume V (Å )
3261.14(18)
4
1845.15(16)
4
1054.32(13)
Z
2
Calculated density (ρ)
1.456
1.748
2.018
1.754
-3
(
Mg m )
Absorption
0.715
1448
1.488
960
5.395
552
1.095
556
-
1
coefficient, µ (mm )
F(000)
3
Crystal size (mm )
0.35 x 0.30 x 0.25 0.3 x 0.25 x 0.20 0.30 x 0.25 x 0.20
0.5 × 0.45 × 0.40
θ range for data
collection
1.986 to 28.27°
2.93 to 28.18°
2.265 to 28.243°
2.54 to 24.99°
Limiting indices
-14 ≤ h ≤ 14
-11 ≤ h ≤ 12
-17 ≤ k ≤ 16
-19 ≤ l ≤ 19
13632 / 4545
-6 ≤ h ≤ 11
-13 ≤ k ≤ 13
-16 ≤ l ≤ 15
8565 / 4688
-9≤ h ≤ 8,
-12 ≤ k ≤ 11,
-16 ≤ l ≤ 16
6599 / 3636
-14 ≤ k ≤ 13
-35 ≤ l ≤ 35
Reflections collected /
Unique Reflections
24516 / 8083
[R(int) = 0.0258]
[R(int) = 0.0258] [R(int) = 0.0224]
[R(int) = 0.0249]
(R )
int
Completeness to θ
25.242 (99.9%)
Semi-empirical
from equivalents
28.18 (99.3%)
Semi-empirical
25.242 (99.2%)
Semi-empirical
24.99 (98.0%)
Semi-empirical from
equivalents
Absorption correction
from equivalents from equivalents

2
5
Maximum and
minimum
0.836 and 0.779
0.743 and 0.646
0.349 and 0.226
0.645 and 0.584
transmission
Data / restraints /
parameters
8019 / 114 / 440
0.921
4518 / 1 / 240
1.030
4688 / 1 / 239
0.961
3707 / 4 / 310
0.968
2
Goodness-of-fit on F
Final R indices
R
1
= 0.0398,
= 0.1047
= 0.0671,
= 0.1226
1.403 and -0.469
R
1
= 0.0263,
R
1
= 0.0321,
wR2 = 0.0680
= 0.0566,
= 0.0774
0.429 and -0.569 0.867 and -0.574
R = 0.0253,
1
[I > 2σ (I)]
wR
2
wR
2
= 0.0716
= 0.0338,
wR
2
= 0.0705
R indices (all data)
R
1
R
1
R
1
R
1
= 0.0294,
wR
2
= 0.0759
wR
2
wR
2
= 0.0789
wR
2
Largest difference
0.412 and -0.355
-3
peak and hole (e Ǻ )
= Σ||F
2
2 2
2 2 1/2
R
1
o
| - |F
c
|| / Σ|F
o
|
2 o c o
wR = [Σw(F -F ) / Σw(F ) ]
Table 2. Selected bond lengths (Å) and bond angles (°) of compounds 1-4
Bond lengths (Å)
[
Cd(L)
2
] (1)
[Cd(HL)Cl
2
] (2)
[Cd(HL)Br
Br(1)–Cd(1)
2
] (3)
[Cd(HL)(NO
O(5)–Cd(1)
O(6)–Cd(1)
O(8)–Cd(1)
N(1)–Cd(1)
O(5)–Cd(1)
N(3)–Cd(1)
O(1)–Cd(1)
O(2)–Cd(1)
O(4)–Cd(1)
C(6)–N(3)
3
)
2
(H O)] (4)
2
N(1)–Cd(1)
N(3)–Cd(1)
N(5)–Cd(1)
N(7)–Cd(1)
O(1)–Cd(1)
O(2)–Cd(1)
C(6)–N(3)
C(24)–N(7)
N(3)–N(4)
N(7)–N(8)
C(12)–N(4)
C(30)–N(8)
C(12)–O(1)
C(30)–O(2)
2.364(3)
2.282(2)
2.409(3)
2.295(2)
2.240(2)
2.255(3)
1.281(4)
1.286(4)
1.379(3)
1.364(3)
1.328(4)
1.342(4)
1.268(4)
1.265(3)
Cl(1)–Cd(1)
2.4040(7)
2.4245(7)
2.363(2)
2.3548(18)
2.3896(17)
1.288(3)
1.364(3)
1.356(3)
1.231(3)
2.5503(5)
2.5137(5)
2.340(3)
2.395(3)
2.444(3)
1.295(4)
1.359(4)
1.362(4)
1.228(5)
2.301(3)
2.812(3)
2.294(2)
2.344(2)
2.301(3)
2.384(2)
2.385(2)
2.443(2)
2.424(2)
1.288(3)
1.356(3)
1.361(3)
1.229(3)
1.261(4)
1.210(4)
1.254(3)
1.230(4)
1.201(4)
Cl(2)–Cd(1)
N(1)–Cd(1)
N(3)–Cd(1)
O(1)–Cd(1)
C(6)–N(3)
N(3)–N(4)
C(12)–N(4)
C(12)–O(1)
Br(2)–Cd(1)
N(1)–Cd(1)
N(3)–Cd(1)
O(1)–Cd(1)
C(6)–N(3)
N(3)–N(4)
C(12)–N(4)
C(12)–O(1)
N(3)–N(4)
C(12)–N(4)
C(12)–O(1)
O(2)–N(5)
O(3)–N(5)
O(4)–N(5)
O(5)–N(6)
O(6)–N(6)

2
6
O(7)–N(6)
1.231(4)
Bond angles (°)
[
Cd(L)
2
] (1)
[Cd(HL)Cl
N(1)–Cd(1)–O(1)
N(3)–Cd(1)–Cl(1)
2
] (2)
133.90(6)
[Cd(HL)Br
2
] (3)
[Cd(HL)(NO
3
)
2
(H
2
O)] (4)
159.43(9)
132.04(10) O(6)–Cd(1)–O(8) 157.45(10)
N(3)–Cd(1)–N(7) 155.76(8)
O(1)–Cd(1)–N(1) 139.61(8)
Br(1)–Cd(1)–Br(2) 135.08(18) N(3)–Cd(1)–O(2)
129.49(6)
115.41(2)
114.91(5)
105.95(6)
102.18(5)
101.58(6)
98.55(5)
67.57(7)
66.68(6)
N(1)–Cd(1)–O(1)
N(3)–Cd(1)–Br(2)
N(1)–Cd(1)–Br(1)
N(1)–Cd(1)–Br(2)
N(3)–Cd(1)–Br(1)
O(1)–Cd(1)–Br(1)
O(1)–Cd(1)–Br(2)
N(3)–Cd(1)–N(1)
N(3)–Cd(1)–O(1)
O(2)–Cd(1)–N(5) 137.32(9) Cl(1)–Cd(1)–Cl(2)
122.99(7)
105.58(7)
103.85(7)
99.52(7)
92.58(8)
92.17(7)
67.38(9)
66.01(9)
O(5)–Cd(1)–O(8)
N(3)–Cd(1)–O(4)
O(1)–Cd(1)–O(4)
N(1)–Cd(1)–O(1)
N(1)–Cd(1)–O(2)
O(6)–Cd(1)–O(1)
154.43(9)
141.20(7)
140.67(7)
134.48(7)
131.13(8)
121.99(8)
O(2)–Cd(1)–N(3) 129.20(8)
O(1)–Cd(1)–N(7) 125.66(8)
O(1)–Cd(1)–O(2) 102.85(9)
O(2)–Cd(1)–N(1) 99.79(10)
N(3)–Cd(1)–Cl(2)
N(1)–Cd(1)–Cl(1)
O(1)–Cd(1)–Cl(2)
N(1)–Cd(1)–Cl(2)
O(1)–Cd(1)–Cl(1)
N(3)–Cd(1)–N(1)
N(3)–Cd(1)–O(1)
O(1)–Cd(1)–N(5)
N(3)–Cd(1)–N(5)
N(7)–Cd(1)–N(1)
94.46(8)
93.32(8)
93.49(9)
O(5)–Cd(1)–O(4) 119.67(10)
O(6)–Cd(1)–N(3) 110.87(9)
O(5)–Cd(1)–N(1) 103.01(10)
N(1)–Cd(1)–N(5) 90.99(10)
O(1)–Cd(1)–N(3)
N(3)–Cd(1)–N(1)
O(2)–Cd(1)–N(7)
N(7)–Cd(1)–N(5)
69.88(8)
69.86(8)
69.47(8)
68.73(8)
O(8)–Cd(1)–N(1)
O(1)–Cd(1)–O(2)
O(5)–Cd(1)–O(2)
O(5)–Cd(1)–N(3)
O(6)–Cd(1)–O(2)
O(8)–Cd(1)–O(2)
O(8)–Cd(1)–N(3)
N(1)–Cd(1)–O(4)
O(6)–Cd(1)–O(4)
O(8)–Cd(1)–O(1)
O(8)–Cd(1)–O(4)
O(5)–Cd(1)–O(1)
O(6)–Cd(1)–N(1)
N(1)–Cd(1)–N(3)
N(3)–Cd(1)–O(1)
O(4)–Cd(1)–O(2)
O(6)–Cd(1)–O(5)
97.35(10)
94.08(8)
92.90(13)
89.59(12)
85.20(10)
85.09(11)
83.91(10)
80.40(7)
79.26(8)
79.02(9)
78.71(10)
75.68(8)
74.19(9)
67.71(7)
66.79(7)
52.07(7)
46.56(9)
Table 3
3 2 2
Geometric parameters for the nitrate ligand coordination in [Cd(HL)(NO ) (H O)] (4).
Mode NO
3
(1)
Mode NO
3
(2)
l
2 1
-l
0.019
0.511

2
7
A
1
-A
2
1.13
25.3
l
3
-l
2
0.3977
172
0.1545
165.7
A
3
Bidentate
Monodentate

2
8
Fig. 1. ORTEP plot of [Cd(L)
2
] (1) along with atom numbering scheme of the non-
hydrogen atom. Displacement ellipsoids are drawn at 30% probability.
Fig. 2. ORTEP plot of [Cd(HL)Cl
2
] (2) along with atom numbering scheme of the non-
hydrogen atom. Displacement ellipsoids are drawn at 30% probability.

2
9
Fig. 3. ORTEP plot of [Cd(HL)Br
2
] (3) along with atom numbering scheme of the non-
hydrogen atom. Displacement ellipsoids are drawn at 30% probability.
Fig. 4. ORTEP plot of [Cd(HL)(NO
3
)
2
(H O)] (4) along with atom numbering scheme of
2
the non-hydrogen atom. Displacement ellipsoids are drawn at 30% probability.