Synthesis and characterization of three new photo-luminescent cadmium(II) complexes with azide: Variation in molecular structures with changes in the denticity of blocking ligands

Article abstract of DOI:10.1016/j.ica.2014.11.026

Three new cadmium(II) complexes, [Cd(dede)(μ-1,3-N₃)(μ-1,1-N₃)]_n (1), [{Cd₃(L¹)₂(μ-1,1-N₃)₄(CH₃OH)₂}·2CH₃OH·2H₂O]_n

Full text of DOI:10.1016/j.ica.2014.11.026

Accepted Manuscript
Synthesis and characterization of three new photo-luminescent cadmium(II)
complexes with azide: Variation in molecular structures with changes in the
denticity of blocking ligands
Sumit Roy, Prasanta Kumar Bhaumik, Klaus Harms, Shouvik Chattopadhyay
PII:
S0020-1693(14)00722-1
http://dx.doi.org/10.1016/j.ica.2014.11.026
ICA 16310
DOI:
Reference:
Inorganica Chimica Acta
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Received Date:
Revised Date:
Accepted Date:
2 September 2014
23 October 2014
12 November 2014
Please cite this article as: S. Roy, P.K. Bhaumik, K. Harms, S. Chattopadhyay, Synthesis and characterization of
three new photo-luminescent cadmium(II) complexes with azide: Variation in molecular structures with changes in
the denticity of blocking ligands, Inorganica Chimica Acta (2014), doi: http://dx.doi.org/10.1016/j.ica.2014.11.026
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1 Synthesis and characterization of three new photo-
2 luminescent cadmium(II) complexes with azide: Variation in
3 molecular structures with changes in the denticity of
4 blocking ligands
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Sumit Roya, Prasanta Kumar Bhaumika, Klaus Harmsb, Shouvik
Chattopadhyaya,*
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aDepartment of Chemistry, Inorganic Section, Jadavpur University, Kolkata 700 032, India
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e mail: Shouvik.chem@gmail.com
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bFachbereichChemie, Philipps-Universität Marburg, Hans-Meerwein-Straße, 35032 Marburg,
Germany
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Abstract
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Three new cadmium(II) coordination complexes, [Cd(dede)(-1,3-N3)(-1,1-N3)]n (1),
[{Cd3(L1)2(-1,1-N3)4(CH3OH)2}2CH3OH2H2O]n (2) and [(CdL2)3(μ-1,1,1-OH)][(CdL2)3(μ-
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1,1,1-N3)](ClO4)4H2O (3) {dede
=
N,N-diethyl-1,2-diaminoethane, HL1
=
2-(2-
(diethylamino)ethylimino)methyl)phenol and HL2 = 2-(2-(diethylamino)ethylimino)methyl)-6-
methoxyphenol}, have been prepared and characterized by elemental and spectral analysis. The
structures of the complexes have been confirmed by single crystal X-ray diffraction studies.
Complex 1 contains alternating double µ-1,1- and µ-1,3-azide bridges and creates two-
dimensional sheet with 63-hcb topology. Complex 2 consists of µ-1,1- azide bridged chain and
forms three-dimensional architecture via hydrogen bonding interactions. Complex 3 has a partial
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cubane [Cd3O4] core consisting of trinulear cadmium(II) moieties. 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.
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Keywords: Cadmium(II); crystal structure; azide, octahedral; 63-hcb.
1. Introduction
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The potential applications of the coordination polymers in catalysis, optics, magnetism,
molecular architectures, materials chemistry etc have attracted the attention of the synthetic
inorganic chemists for their rational design and synthesis [1-6]. These materials consist of
metallic centers assembled by multifunctional organic or inorganic linkers, such as
pseudohalides, dicyanamide, carboxylates etc [7-9]. Among them, azide is widely used to build
various polynuclear transition metal complexes with fascinating structural diversities and
promising potential applications in functional materials [10-12]. It is to be noted here, azide
serves as a very good ligand in propagating magnetic interaction among the paramagnetic centers
and as a result, huge numbers of azide bridged transition complexes have been prepared in order
to examine the magnetic exchange interaction in these species [13-15]. Focusing to cadmium(II)
with d10 configuration, the azide bridged polynuclear complexes did not receive considerable
attention till date, possibly because of the lack of magnetic exchange interaction in it. In this
context, it is noteworthy that the importance of the cadmium(II) complexes lies in their strong
luminescence properties.
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In the present work, we have used N,N-diethyl-1,2-diaminoethane as a bidentate blocking
ligand and its condensation products with salicylaldehyde and 3-methoxysalicylaldehyde
respectively to form tridentate (HL1) and tetradentate (HL2) Schiff base blocking ligands. The
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ligands are then made to react with cadmium(II) in presence of azide. Our intension was to
examine the changes, if any, in the crystalline and supra-molecular architecture of the complexes
with the change in the denticity of the ligands. N,N-diethyl-1,2-diaminoethane forms alternating
double µ-1,1- and µ-1,3-azide bridged neutral two-dimensional sheet with 63-hcb topology. On
the other hand, the use of the tridentate Schiff base (HL1) as the blocking ligand, an one-
dimensional chain of azide bridged cadmium(II) complex is formed. The complex forms three-
dimensional architecture via hydrogen bonding interactions. The use of tetratendate Schiff base
(HL2) leads to produce a trinuclear cadmium(II) complex having a partial cubane [Cd3O4] core.
The variation in the blocking ligands changes the molecular and crystalline architectures of
cadmium(II) azide complexes. Herein, we like to report the synthesis, characterization, crystal
structures, supramolecular architectures and fluorescence properties of three new cadmium(II)
azide complexes.
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2. Experimental
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All starting materials and solvents were commercially available, reagent grade, and used
as purchased from Sigma-Aldrich without further purification.
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Caution!!!
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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.
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2.1. Preparations
2.1.1. Synthesis of [Cd(dede)(-1,3-N3)(-1,1-N3)]n (1)
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A methanol solution of N,N-diethyl-1,2-diaminoethane (dede) (1 mmol, 0.140 ml) was
added to a methanol solution of cadmium(II) acetate dihydrate (1 mmol, 0.266 g) drop wise with
constant stirring, followed by the addition of an aqueous methanol solution of sodium azide (1
mmol, 0.065 g). The stirring was continued for 1 h. Diffraction quality single crystals were
obtained after few days on slow evaporation of the solution in open atmosphere.
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Yield: 0.21 g (69 %). Anal. Calc. for C6H16CdN8 (312.67): C, 23.05; H, 5.16; N, 35.84 %.
Found: C, 23.01; H, 5.07; N, 35.91 %. IR (KBr, cm-1): 3444 (υNH2), 2051 (υN3); UV–Vis, max
(nm), (εmax (dm3 mol-1 cm-1)) (DMSO), 260 (6.9 × 102).
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2.1.2. Synthesis of [{Cd3(L1)2(-1,1-N3)4(CH3OH)2}2CH3OH2H2O]n (2)
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A methanol solution of salicylaldehyde (1 mmol, 0.104 ml) and N,N-diethyl-1,2-
diaminoethane (1 mmol, 0.140 ml) was refluxed for 1 h to prepare the tridentate Schiff base, 2-
(2-(diethylamino)ethylimino)methyl)phenol (HL1). A methanol solution cadmium(II) acetate
dihydrate (1 mmol, 0.266 g) was added drop wise to the methanol solution of the Schiff base
followed by addition of aqueous methanol solution of sodium azide (1 mmol, 0.065 g) with
constant stirring. The stirring was continued for an additional 20 min. Diffraction quality single
crystals were obtained after few days on slow evaporation of the solution in open atmosphere.
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Yield: 1.55 g (74%). Anal. Calc. C58H102Cd6N32O11 (2098.11): C, 40.18; H, 5.93; N, 4.85
%. Found: C, 40.13; H, 5.87; N, 4.92 %. IR (KBr, cm-1):1634 (υC=N), 2071 (υN3), 3382 (υOH);
UV–Vis, max (nm), (εmax (dm3 mol-1 cm-1)) (DMSO), 377 (3.1 × 104).
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2.1.3. Synthesis of [(CdL2)3(μ-1,1,1-OH)][(CdL2)3(μ-1,1,1-N3)](ClO4)4H2O (3)
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A methanol solution of 3-methoxysalicylaldehyde (1 mmol, 0.152 g) and N,N-diethyl-
1,2-diaminoethane (1 mmol, 0.140 ml) was refluxed for 1 h to prepare a tetradentate Schiff base,
2-(2-(diethylamino)ethylimino)methyl)-6-methoxyphenol (HL2). A methanol solution of
cadmium(II) perchlorate hexahydrate (1 mmol, 0.419 g) was added drop wise to the methanol
solution of the Schiff base followed by addition of aqueous methanol solution of sodium azide (1
mmol, 0.065 g) with constant stirring. The stirring was continued for additional 30 min. Single
crystals, suitable for X-ray diffraction, were obtained after few days on slow evaporation of the
solution in open atmosphere.
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Yield: 1.66 g (63%). Anal. Calc. for C84H129Cd6N15O30Cl4 (2645.21) : C, 38.14; H, 4.92;
N, 7.94 Found: C, 38.05; H, 4.86; N, 8.01. IR (KBr, cm-1): 1088 (υClO4), 1633 (υC=N), 2058 (υN3),
3468 (υOH), 2975 (υCH); UV–Vis, max (nm), (εmax (dm3 mol-1 cm-1)) (DMSO), 394 (3.1 × 103),
348 (3.6 × 103), 272 (3.2 × 103).
2.2. Physical measurements
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Elemental analyses (carbon, hydrogen and nitrogen) were performed on a Perkin–Elmer
240C elemental analyzer. Infrared spectra in KBr (4500–500 cm-1) were recorded using a
PerkinElmer FT-IR spectrum two spectrometer. Electronic spectra in DMSO (800–200 nm)
were recorded on a Jasco V-630 UV–Vis spectrophotometer. Fluorescence spectra in DMSO
were obtained on a Hitachi F-7000 Fluorescence spectrophotometer at room temperature.
Lifetime measurements were recorded using Hamamatsu MCP photomultiplier (R3809) and
were analyzed by using IBHDAS6 software. The powder XRD spectra were recorded in a 2θ
range of 2–50° using a 1D Lynxeye detector under ambient conditions.
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2.3. X-ray crystallography
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Single crystals of the complexes were used for data collection using a Bruker D8 QUEST
area detector diffractometer equipped with graphite-monochromated Mo-Kα radiation (=
0.71073 Å) at 100 K. The X-ray intensity data were measured. The frames were integrated with
the Bruker SAINT Software package using a wide-frame algorithm. The molecular structure was
solved by direct method and refined by full-matrix least squares on F2 using SHELXS-97 and
SHELXL-2013 [16]. Non-hydrogen atoms were refined with anisotropic thermal parameters.
The hydrogen atoms attached to oxygen were located by difference Fourier maps and were kept
at fixed positions. All other hydrogen atoms were placed in their geometrically idealized
positions and constrained to ride on their parent atoms. Data were corrected for absorption
effects using the multi-scan method (SADABS) [17]. Data collection software = BRUKER
APEX II [18]; Cell refinement software = SAINT V8.34A (Bruker AXS Inc., 2013); Data
reduction software = SAINT V8.34A (Bruker AXS Inc., 2013). The crystallographic and
refinement data of the complexes are summarized in Table 1. Selected bond lengths are gathered
in Table 2. Selected bond angles are summarized in Tables S1, S2 and S3.
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122 3. Results and discussions
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3.1. Synthesis
A bidentate chelating ligand (dede), a tridentate Schiff base (HL1) and a tetradentate
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Schiff base (HL2) were used in the present work to prepare cadmium(II) azide complexes. The
Schiff base ligands, HL1 and HL2, had been prepared by 1:1 condensation of N,N-diethyl-1,2-
diaminoethane with salicylaldehyde and 3-methoxysalicylaldehyde, respectively, in methanol,
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following the literature method [19]. The ligands were not isolated and their methanol solutions
were used directly to prepare the complexes.
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Complex 1 was synthesized by stirring N,N-diethyl-1,3-diaminoethane (dede) with
cadmium(II) acetate dihydrate and sodium azide in methanol. The bidentate ligand blocked two
sites of the octahedral cadmium(II). The remaining sites were occupied by azides. Exploiting
the µ-1,1- and µ-1,3-bridging capacity of azides, a two-dimensional coordination polymer,
[Cd(dede)(-1,3-N3)(-1,1-N3)]n (1) was formed. Complex 2 was prepared on adding
cadmium(II) acetate dihydrate and sodium azide into the methanol solution of HL1. The
tridentate Schiff base occupied three coordinating sites of octahedral cadmium(II). Exploiting
bridging capacity of phenoxo oxygen atoms and azides, a one-dimensional coordination
polymer, [{Cd3(L1)2(-1,1-N3)4(CH3OH)2}2CH3OH2H2O]n (2), was formed. On the other
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hand, [(CdL2)3(μ-1,1,1-OH)][(CdL2)3(μ-1,1,1-N3)](ClO4)4H2O (3), was produced on stirring the
tetradentate Schiff base, HL2 with cadmium(II) perchlorate hexahydrate and sodium azide. X-
,
ray quality single crystals of all the three complexes were obtained from methanol solution by
slow evaporation at room temperature. The formation of the complexes is shown in Scheme 1.
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Scheme 1: Preparation of complexes 1, 2 and 3.
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3.2. Description of structures
3.2.1. [Cd(dede)(-1,3-N3)(-1,1-N3)]n (1)
The complex crystallizes in the monoclinic space group P21/c. The structure
determination reveals that the cadmium(II) is coordinated by two amine nitrogen atoms, N(1)
and N(4), of the chelating ligand, dede and two nitrogen atoms, N(1Z) and N(4Z), from two
azides. A symmetry related nitrogen atom, N(1Z)b, from a µ-1,1-azide coordinate cadmium(II) to
form a centrosymmetric dimer. Another nitrogen atom, N(6Z)a from a symmetry related µ-1,3-
azide (a = 1-x,-1/2+y,1/2-z) coordinate Cd(1) to complete its octahedral geometry {Figure 1(a)}
and thereby connects the above mentioned dimers to form a two-dimensional sheet along
crystallographic ab plane {Figure 1(b)}. Cadmuim(II)–nitrogen bond lengths are ranging from
2.3172(13) to 2.4054(13) Å, as was also observed in similar systems [20-22]. The closest
conformation of the saturated five member ring, Cd(1)–N(1)–C(2)–C(3)–N(4) is half chair with
puckering parameters Q(2) = 0.4716(16) Å and υ = 275.48(14)º [23]. The Cd···Cd separation
(3.5146(4) Å)across double -1,1-azide bridge is much shorter than that (5.6774(3) Å) for single
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-1,3-azide bridge, as expected. End-on (-1,1) azide bridges are asymmetric with N−N
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distances in the range 1.207(2)-1.154(2) Å, whereas end-to-end (-1,3) bridges are practically
symmetric with N−N distances of 1.180(2) Å, as were also observed in similar systems [24]
Topology analysis reveals a 63-hcb topology (Figure 2) with cadmium(II) occupying the nodes,
where end-to-end and end-on azide connectors take part in the formation of edges.
The hydrogen atom, H(3A), attached to the nitrogen atom, N(4), is participated in weak
hydrogen bonding with an azide nitrogen atom, N(12)c, related by an inversion centre. Another
hydrogen atom, H(3B), attached to N(4), is also involved in hydrogen bonding (Table 3) with the
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symmetry related (x,-1+y,z) nitrogen atom, N(6Z)d (Figure S1) to form a 2D sheet along
crystallographic ab plane. There is no other supra-molecular interaction present in the complex.
The neighbouring layers are packed along the crystallographic c axis and no hydrogen bonding
interactions are observed between the layers. The nearest interlayer Cd(II)···Cd(II) distance is
9.0503(4) Å.
3.2.2. [{Cd3(L1)2(-1,1-N3)4(CH3OH)2}2CH3OH2H2O]n (2)
The molecular structure of 2 with selected atom numbering scheme is shown in Figure 3.
The complex crystallizes in the orthorhombic space group Fdd2. The complex assumes chain
structure having trinuclear cadmium(II) moieties as the building blocks, in which all the
cadmium(II) {Cd(1), Cd(2) and Cd(3)} possess distorted octahedral geometries. Two nitrogen
atoms, N(4Z) and N(10Z), from two µ-1,1-bridged azides and two oxygen atoms, O(7) and
O(7A), from two deprotonated Schiff base molecules and two more oxygen atoms, O(100) and
O(200), from two methanol molecules coordinate Cd(2) to complete its distorted octahedral
geometry. The environment around Cd(3) centre is very similar to that of the Cd(1) centre. Cd(1)
is coordinated by two nitrogen atoms, N(1) and N(4), and an oxygen atom, O(7), of a tridentate
deprotonated Schiff base and two µ-1,1-bridging azide nitrogen atoms, N(1Z) and N(4Z). On the
other hand, Cd(3) is coordinated by two nitrogen atoms, N(1A) and N(4A), and an oxygen atom,
O(7A), of a second molecule of the tridentate deprotonated Schiff base, and two µ-1,1-bridged
azide nitrogen atoms, N(7Z) and N(10Z). Symmetry related nitrogen atoms, N(7Z)e, and N(1Z)f,
from two different µ-1,1-bridged azide coordinate Cd(1) and Cd(3) respectively to grow the
polymer along the crystallographic screw axis.
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The angles between Cd(1)N(4Z)O(7)Cd(2) and Cd(2)N(10Z)O(7A)Cd(3) rhombohedral
planes are 83.870 and that between Cd(2)N(4Z)O(7)Cd(1) and Cd(1)N(7Z)N(1Z)Cd(3)
rhombohedral planes are 64.290. The saturated five membered chelate rings, Cd(1)-N(1)-C(2)-
C(3)-N(4) and Cd(3)-N(1A)-C(2A)-C(3A)-N(4A) assume envelope conformation with puckeing
parameters q = 0.508(3) Å, υ =56.7(3)° and q = 0.487(3) Å, υ= 57.1(3)° respectively. The N(1)–
Cd(1)–N(4) and N(1A)–Cd(3)–N(4A) angles are 76.17(8)º and 76.12(8)º respectively and are
typical of five-membered chelates [25,26]. Cd–Nimine distances [2.298(2)–2.307(2) Å] are shorter
than the Cd–Namine [2.375(2)–2.378(2) Å] distances, as was also observed in similar systems [24,
27-30]. The Cd(2)···Cd(1), Cd(2)···Cd(3) and Cd(1)···Cd(3) distances are 3.525(1), 3.625(1) and
6.165(1) Å respectively. The bridging azides are quasi-linear; the N–N–N angles are 178.0(3)º,
179.7(3)º, 178.6(3)º and 178.3(3)º, as was observed in similar systems [25].
The hydrogen atom, H(400), attached with the oxygen atom, O(400), of the non-
coordinating lattice water molecule participates in hydrogen bond formation with the azide
nitrogen atom, N(12Z). The oxygen atom, O(400), of the same water molecule forms another
hydrogen bond with the hydrogen atom, H(300), attached with the oxygen atom, O(300), of the
non-coordinated methanol molecule. Again, the hydrogen atoms, H(100) and H(200), attached
respectively with the oxygen atoms, O(100) and O(200), of the coordinated methanol molecules
involve in hydrogen bonding interactions with the symmetry related nitrogen atom, N(9Z)g {g =
1-x,1-y,z} of a neighbouring molecule. These hydrogen bonding interactions lead to the
formation of three-dimensional supramolecular network (Figure S2). The details of hydrogen
bonding interactions are given in Table 3. The complex shows intra-chain C–H∙∙∙π interactions
with C...centroid distances being in the range 3.6-3.8 A.
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3.2.3. [(CdL2)3(μ-1,1,1-OH)][(CdL2)3(μ-1,1,1-N3)](ClO4)4H2O (3)
Complex 3 contains two independent cations, [(CdL2)3(μ-1,1,1-OH)]2+ (A) and
[(CdL2)3(μ-1,1,1-N3)]2+ (B), and four non-coordinated perchlorate anions together with a lattice
water molecule. The structures of both independent cations (A and B) have crystallographic 3-
fold symmetry. A perspective view of [(CdL2)3(μ-1,1,1-OH)]2+ (A) with selected atom
numbering scheme is shown in Figure 4. [(CdL2)3(μ-1,1,1-N3)]2+ (B) has a very similar structure,
as shown in Figure 5.
The trinuclear cationic parts are comprised of three CdL2 subunits in which each
cadmium(II) is coordinated to a deprotonated tetradentate monoanionic ligand (L2)-. The subunits
are held together by two distinct bridging systems: (i) an oxygen atom (O500) of a triply
bridging hydroxo group (in A) or a nitrogen atom (N1AZ) of a triply bridging azide group (in B),
which is coordinated to each of three cadmium(II) centers, and (ii) three hydroxo oxygen atoms,
each of them from three different ligand molecules. The three cadmium(II) and the bridging
hydroxo group (in A) {or the bridging azide group (in B)} form a flattened trigonal pyramid,
with the cadmium(II) falling at the corners of equilateral sides (3.536(1) Å in A and 3.628(1) Å
in B) and angles (60.00(2)0). The face-capping oxygen atom O(500) is located at 1.020 Å above
the plane defined by the Cd3 triangle in A. On the other hand, the face-capping nitrogen atom
(N1AZ) is located at 1.301 Å above the plane defined by the Cd3 triangle in B.
The presence of Cd3OH in A is confirmed by (a) the location of the hydrogen atom at the
expected position in the final difference Fourier map, (b) the electroneutrality of the crystal, and
(c) the refined Cd–O(H) distances and Cd–O(H)–Cd angles, which agree well with a roughly
tetrahedral or pseudo-tetrahedral sphere of Cd, Cd, Cd, H species around the oxygen atom. The
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average bond lengths in the square-pyramidal coordination sphere both in A and B are close to
those in other related Cd(II) complexes [20].
3.3. IR, electronic and fluorescence spectra and powder X-ray diffraction study
In the IR spectrum of complex 1, the sharp band due to the amino NH2 group appears at
3444 cm-1 [31]. In the IR spectra of complexes 2 and 3, band corresponding to the azomethine
(C=N) stretching vibration appear at around 1634 and 1633 cm-1 respectively. Very strong bands
around 2050 cm-1 are assigned to the vibration of the bridging azide ligands [32-33]. In the IR
spectra of complexes 2 and 3, broad bands at ~ 3382 and 3468 cm-1 may be assigned as OH
stretching vibrations.
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The electronic spectra for all the complexes were recorded in DMSO solution in the
range 200–800 nm. In case of complexes 1 and 2, the intense absorption bands are observed
around 260 and 377 nm respectively. For complex 3, three bands around 272, 348 and 394 nm
are noticed. All the bands are assigned as intra ligand charge transfer transitions [34]. The
complexes exhibit luminescence in DMSO medium. On exciting at 260, 377 and 348 nm,
emissions are observed at 418, 422, and 421 nm for complexes 1, 2, and 3 respectively. The
fluorescence lifetimes of the complexes are investigated in DMSO solution at room temperature.
The lifetimes of 1, 2 and 3 are about 12.21, 11.17 and 12.25 ns respectively (Table 4), which are
similar to other cadmium(II) complexes [35]. Decay profiles (Figure S3, Supplementary
Information) were fitted following the literature method [34]. The relative fluorescence quantum
yields for the complexes were measured in DMSO using quinine sulfate (in 0.5 (M) H2SO4,
=
0.54) as the quantum yield standard [36]. The fluorescence quantum yields of complexes 1, 2 and
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3 are 0.0047, 0.178 and 0.1624 respectively. Quantum yields were calculated following the
literature method [37]
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The experimental powder XRD patterns of the bulk product of all the complexes
are in good agreement with the simulated XRD patterns from single crystal X-ray diffraction,
confirming purity of the bulk samples (Figure S4).
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270 4. Summary
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The synthesis and characterization of three cadmium(II) azide complexes with N,N-
diethyl-1,2-diaminoethane have been described in the present paper. Cadmium(II) centres
assume octahedral geometries in all three complexes. Complex 1 features alternating double µ-
1,1- and µ-1,3- azide bridges and forms two-dimensional sheet with 63-hcb topology. Hydrogen
bonding interaction in complex 2 leads to three-dimensional supramolecular network. Complex 3
contains two independent trinuclear cations with partial cubane [Cd3O3X] cores, in which
cadmium(II) centres are bridged by μ-1,1,1-OH or μ-1,1,1-N3. The use of three different
blocking ligands can effectively change the molecular and crystalline architectures of the
complexes. All the complexes show fluorescence with fluorescence lifetime ~ 12 ns.
Acknowledgement
This work was supported by the DST, India, under FAST Track Scheme (Order No.
SR/FT/CS-118/2010, dated 15/02/2012).
14

286
287
288
289
290
291
292
Appendix A. Supplementary data
CCDC 996855, 1000620 and 1005615 contain the supplementary crystallographic data
for the complexes 1, 2 and 3 respectively. These data can be obtained free of charge via
http://www.ccdc.cam.ac.uk/conts/retrieving.html or from the Cambridge Crystallographic Data
Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: (+44) 1223-336-033; or e-mail:
deposit@ccdc.cam.ac.uk.
293
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294
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296
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354
355
356
357
358
359
360
361
362
363
364
365
18

366
Table 1: Crystal data and refinement details of complexes 1, 2 and 3.
1
C6H16CdN8
312.67
2
3
Formula
Formula Weight
Temperature (K)
Crystal system
Space group
a(Å)
C58H102Cd6N32O11 C84H129Cd6Cl4N15O30
2098.11
100
2645.21
100
100
Monoclinic
P21/c
Orthorhombic
Fdd2
Trigonal
P31c
10.4729(3)
8.2775(2)
13.7414(4)
100.1363(12)
4
35.4193(15)
35.9490(13)
12.7424(5)
90
13.0841(10)
13.0841(10)
34.980(3)
90
b(Å)
c(Å)
β
Z
8
2
dcalc (g cm-3)
μ (mm-1)
1.771
1.718
1.694
1.847
1.617
1.392
F(000)
624
8400
2668
Total Reflections
Unique Reflections
Observed data[I >2 σ (I)]
No. of parameters
R(int)
18604
59966
40479
2179
10871
7921
2044
10255
6904
146
499
424
0.023
0.025
0.050
R1, wR2 ( all data)
R1, wR2 [I > 2 σ (I)]
0.0144, 0.0324
0.0127, 0.0307
0.0235, 0.0379
0.0197, 0.0371
0.0456, 0.0760
0.0343, 0.0727
367
19

368
Table 2: Selected bond lengths (Å) of complexes 1, 2 and 3.
Cd(1)–N(1)
Cd(1)–N(4)
2.4054(13)
2.3172(13)
2.3363(13)
2.272(2)
2.268(2)
2.310(3)
2.249(2)
2.392(3)
2.280(3)
2.2774(19)
2.379(2)
2.327(2)
2.601(5)
2.282(3)
2.205(5)
2.211(5)
2.466(6)
2.183(8)
Cd(1)–N(1Z)
Cd(1)–N(6Z)a
Cd(1)–N(1Z)b
Cd(1)–N(1)
2.3528(12)
2.3688(13)
2.3618(12)
2.375(2)
2.307(2)
2.515(3)
2.2799(19)
2.340(2)
2.283(2)
2.333(3)
2.298(2)
2.400(2)
2.362(9)
2.234(7)
2.272(7)
2.364(7)
2.252(9)
2.504(5)
1
Cd(1)–N(4Z)
Cd(1)–O(7)
Cd(1)–N(1Z)
Cd(1)–N(4Z)
Cd(2)–O(7)
Cd(1)–N(4)
Cd(1)–N(7Z)e
Cd(2)–O(7A)
Cd(2)–O(200)
Cd(2)–N(10Z)
Cd(3)–N(7Z)
Cd(3)–N(4A)
Cd(3)–N(1Z)f
Cd(1)–N(1)h
Cd(1)–O(7)h
Cd(1)–N(4)h
Cd(2)–N(1A)
Cd(2)–N(4A)
Cd(2)–O(8A)i
Cd(2)–O(100)
Cd(2)–N(4Z)
Cd(3)–O(7A)
Cd(3)–N(1A)
Cd(3)–N(10Z)
Cd(1)–O(8)
2
Cd(1)–O(500)
Cd(1)–O(7)
3
Cd(2)–O(7A)
Cd(2)–N(1AZ)
Cd(2)–O(7A)i
369
a
b
e
f
370
371
Symmetry transformations = 1-x,-1/2+y,1/2-z; = 1-x,1-y,-z, = 3/4-x,-1/4+y,1/4+z, = 3/4-
x,1/4+y,-1/4+z, h = -x+y,1-x,z; i = 1-x+y,1-x,z.
20

372
Table 3: Hydrogen bond distances (Å) and bond angles (º) in complexes 1 and 2.
Complex
D–H∙∙∙A
D–H
H∙∙∙A
D∙∙∙A
D–H∙∙∙A
152
N(4)–H(3A)∙∙∙N(12)c
N(4)–H(3B)∙∙∙N(6Z)d
0.91
0.91
2.47
3.3023(18)
3.1183(18)
2.838(3)
2.785(3)
2.873(5)
2.809(6)
1
2.23
166
O(100)–H(100)∙∙∙N(9Z)g
O(200)–H(200)∙∙∙N(9Z)g
O(400)–H(400)∙∙∙N(12Z)
O(300)–H(300)∙∙∙O(400)
0.77(4)
0.93(4)
0.8700
0.8400
2.10(4)
1.86(4)
2.1100
1.9800
163(4)
176(2)
146.00
168.00
2
373
374
375
376
377
Symmetry transformations c = 1-x,1-y,-z, d = x,-1+y,z, g = 1-x,1-y,z.
Table 4: Photo-physical data for the complexes 1-3.
Samples
λex(nm) λem(nm)
τav(ns)
χ2
260
377
348
418
422
421
12.21
11.17
12.25
1.020891
1.1531
1
2
3
1.063163
378
379
21

380
381
(a)
(b)
382
383
384
385
Figure 1: (a) Perspective view of the complex 1 with selective atom-numbering scheme.
a
b
Hydrogen atoms are not shown for clarity. Symmetry transformations, = 1-x,-1/2+y,1/2-z; =
1-x,1/2+y,1/2-z. (b) Two-dimensional sheet of the complex 1. Only the relevant atoms are
shown.
386
387
Figure 2: A perspective view of 63-hcb topology of complex 1 viewing along b axis.
22

388
389
390
391
Figure 3: Perspective view of complex 2 with selective atom numbering scheme. Hydrogen
atoms, alkyl groups, non-coordinated methanol and water molecules are omitted for clarity.
Symmetry transformations e = 3/4-x, -1/4+y, 1/4+z; f = 3/4-x, 1/4+y, -1/4+z.
392
23

393
394
395
396
Figure 4: Perspective view of the trinuclear cation [(CdL2)3(μ-1,1,1-OH)]2+ (A) of complex 3
with selective atom-numbering scheme. The hydrogen atoms (except OH) are not shown for
clarity. Symmetry transformation, h = -x+y,1-x,z.
24

397
398
399
400
Figure 5: Perspective view of the trinuclear cation [(CdL2)3(μ-1,1,1-N3)]2+ (B) of complex 3
with selective atom-numbering scheme. Hydrogen atoms are not shown for clarity. Symmetry
transformation i = 1-x+y,1-x,z.
25

Highlights
Synthesis and characterization of three new photo-
luminescent cadmium(II) complexes with azide: Variation in
molecular structures with changes in the denticity of
blocking ligands
Sumit Roy, Prasanta Kumar Bhaumik, Klaus Harms, Shouvik
Chattopadhyay
• Synthesis and characterization of three cadmium(II) azide complexes
•Presence of alternating double µ-1,1- and µ-1,3-azide bridges
• Formation of two-dimensional sheet with 63-hcb topology
• Formation of partial cubane [Cd3O4] core consisting of trinulear cadmium(II) moieties

Graphical Abstract (Pictogram)
Synthesis and characterization of three new photo-
luminescent cadmium(II) complexes with azide: Variation in
molecular structures with changes in the denticity of
blocking ligands
Sumit Roy, Prasanta Kumar Bhaumik, Klaus Harms, Shouvik
Chattopadhyay

Graphical Abstract (Synopsis)
Synthesis and characterization of three new photo-
luminescent cadmium(II) complexes with azide: Variation in
molecular structures with changes in the denticity of
blocking ligands
Sumit Roy, Prasanta Kumar Bhaumik, Klaus Harms, Shouvik
Chattopadhyay
Three new photo-luminescent cadmium(II) azide complexes have been synthesized and
the structures have been confirmed by X-ray crystal structure analysis. Bidentate, tridentate and
tetradentate ligands have been used as the blocking ligands in preparing the complexes. The
structures of the complexes were drastically varied with the variation in the denticity of the
blocking ligands.