Three isostructural azo-functionalized 3D Cd(II)-coordination polymers for solvent dependent photoluminescence study

Article abstract of DOI:10.1016/j.poly.2018.07.005

Constructions of coordination polymers by applying mixed ligand approach have taken a huge attention to researcher which can be structurally designed by choosing particular components according to the desired applications. An unexploited azo functionalized N,N′ spacer, L = [3,3′-azobis(pyridine)], and three different dicarboxylate co-linkers such as 1,4-naphthalene dicarboxylic acid (NDC), 2-amino terephthalic acid (2-ATA), and 2-nitro terephthalic acid (2-NTA), give rise to three isostructural coordination polymers (CPs) with Cd(II) metal ions with molecular formula of {[Cd(NDC)(L)]·xS}_n, (CP-1), {[Cd(2-ATA)(L)]·xS}_n (CP-2) and {[Cd(2-NTA)(L)]·xS}_n (CP-3) (S = Guest molecules) respectively. All the CPs are constructed via room temperature slow evaporation process and characterized by single crystal X-ray analysis, TGA, FT-IR, PXRD and elemental analysis. The topological analysis reveals that all the CPs feature a 6c-uninodal rare ‘rob’ topology with the point symbol {4⁸·6⁶·8} and possess a dense 3D structure having predefined functionalities on framework backbones. The solvent dependent photoluminescence property has been investigated for all the CPs showing their emissive nature at 379 nm, 419 nm, and 415 nm while excited at 275 nm, 270 nm and 310 nm respectively. The measurements indicates that all the CPs show the quenching in emission spectra for the solvents nitromethane and nitrobenzene.

Full text of DOI:10.1016/j.poly.2018.07.005

Accepted Manuscript
Three Isostructural Azo-functionalized 3D Cd(II)-Coordination Polymers for
Solvent Dependent Photoluminescence Study
Santanu Chand, Subrata Hota, Syed Meheboob Elahi, Madhab C. Das
PII:
S0277-5387(18)30392-9
https://doi.org/10.1016/j.poly.2018.07.005
POLY 13270
DOI:
Reference:
To appear in:
Polyhedron
Received Date:
Revised Date:
Accepted Date:
22 May 2018
3 July 2018
5 July 2018
Please cite this article as: S. Chand, S. Hota, S.M. Elahi, M.C. Das, Three Isostructural Azo-functionalized 3D
Cd(II)-Coordination Polymers for Solvent Dependent Photoluminescence Study, Polyhedron (2018), doi: https://
doi.org/10.1016/j.poly.2018.07.005
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Revised manuscript
POLY-D-18-00461)
(
Three Isostructural Azo-functionalized 3D Cd(II)-Coordination Polymers
for Solvent Dependent Photoluminescence Study
Santanu Chand, Subrata Hota, Syed Meheboob Elahi and Madhab C. Das*
Department of Chemistry, Indian Institute of Technology Kharagpur, WB, 721302, India
E-mail: mcdas@chem.iitkgp.ac.in
_
_______________________________________________________________________
Abstract: Constructions of coordination polymers by applying mixed ligand approach have
taken a huge attention to researcher which can be structurally designed by choosing particular
components according to the desired applications. An unexploited azo functionalized N,N'
spacer, L = [3,3'-azobis(pyridine)], and three different dicarboxylate co-linkers such as 1,4-
naphthalene dicarboxylic acid (NDC), 2-amino terephthalic acid (2-ATA), and 2-nitro
terephthalic acid (2-NTA), give rise to three isostructural coordination polymers (CPs) with
Cd(II) metal ions with molecular formula of {[Cd(NDC)(L)]·xS} , (CP-1), {[Cd(2-
n
ATA)(L)]·xS}n (CP-2) and {[Cd(2-NTA)(L)]·xS}n (CP-3) (S = Guest molecules)
respectively. All the CPs are constructed via room temperature slow evaporation process and
characterized by single crystal X-ray analysis, TGA, FT-IR, PXRD and elemental analysis.
The topological analysis reveals that all the CPs feature a 6c-uninodal rare ‘rob’ topology
8
6
with the point symbol {4 .6 .8} and possess a dense 3D structure having predefined
functionalities on framework backbones. The solvent dependent photoluminescence property
has been investigated for all the CPs showing their emissive nature at 379 nm, 419 nm, and
4
15 nm while excited at 275 nm, 270 nm and 310 nm respectively. The measurements
indicates that all the CPs show the quenching in emission spectra for the solvents
nitromethane and nitrobenzene.

Introduction
Over the past two decades, the design and synthesis of miscellaneous porous coordination
1
-3
polymers (CPs) is escalated day by day because of not only their wide range of applications
4
-5
but also their diverse and fascinating structures and the various kind of topologies. The
judicious choice of the suitable organic linkers plays an utmost role in the fabrication of
porous coordination polymers in which one can easily manipulate the coordination modes,
6
-8
length, rigidity, and incorporation of the functional groups. The synthesis of mixed ligand
CPs by using mainly different dicarboxylate and pyridyl spacers has been constructed in
which the aromatic carboxylate ligand give the chance to assemble different coordination
modes whereas their function property, as well as length, can be modified by the N,N' pyridyl
9
-12
10
spacer.
In recent years, d metal ion based CPs have attracted immeasurable interest due
to their photoluminescence property as they usually do not quench the luminescence intensity
1
3
like the paramagnetic metal center. It is well known that recently CPs as a new kind of
detection materials in solution phase attract more attention because of their selectivity,
1
4
sensitivity, reusability, well anti-interference performance and rapid response time. The role
of Lewis basic sites such as unsaturated (open) pyridyl group, free −NH group, anionic
2
sulfonate group, and −OH group within the porous functional CPs, are mainly highlighted for
1
5-16
enhancing unique recognition towards sensing of various metal ions in various solvents.
A large number of luminescent CPs have been explored for their chemical sensing properties
towards various metal ions, organic nitroaromatic explosives, anions, gases, pH, small
1
7-19
organic molecules and so on.
For the construction of such kind of CP materials,
researchers are mostly using lanthanides salts due to their sharp and intense luminescence
intensity. But, because of the high cost and exiguousness of lanthanides, the CP sensors based
2
0
on transition metals are highly desirable. In order to harvest plausible binding sites of
selective sensing of guests, we are interested to immobilize azo functionality of an
unexploited spacer 3,3'-azobis(pyridine) with uncoordinated N-rich sites on the CP backbone.
Besides, this spacer possesses a highly conjugated -electronic system to provide powerful
luminescence property. Till date by using this spacer a few discrete complexes and hydrogen
2
1
bonding networks are reported, to the best of our knowledge our group has started exploring
2
2
to fabricate CP materials by employing this spacer. We have chosen three different
carboxylic acids having alternative functionalities and the linear spacer L [3,3'-
azobis(pyridine)] to construct three isostructural 3D CPs (scheme 1). The different

dicarboxylates are responsible for the different fluorescence emission behavior in various
solvents.
Based on the above considerations, we have designed and constructed three new 3D
Cd(II)-based CPs {[Cd(NDC)(L)]·xS} , (CP-1), {[Cd(2-ATA)(L)]·xS} (CP-2) and {[Cd(2-
n
n
NTA)(L)]·xS} (CP-3) self-assembled by three different dicarboxylate organic linkers and
n
3
,3'-azobis(pyridine) spacer with exposed azo binding sites under room temperature slow
evaporation process. Solvent-dependent luminescence study has been investigated for all the
complexes, reveling the common feature to quench the luminescence intensity in presence of
solvents like nitromethane and nitrobenzene.
Experimental
Materials and reagents.
All the chemicals were of reagent grade quality, and they were purchased from the
commercial sources and used as received. The spacer L was prepared following a method
2
2
described in the literature.
Physical Measurements. The FT-IR spectra were recorded from KBr pellets in the range of
-1
4
00-4000 cm on a Perkin-Elmer RX1 spectrophotometer. Elemental analyses (C, H, N
analysis) has been carried out using a Perkin-Elmer instrument, series II Model 2400
elemental analyser. PXRD patterns were recorded using Cu K radiation (1.5418 Å) on a
α
Bruker D8 Advance diffactometer. Thermogravimetric analysis (TGA) was performed using
o
a TG 209 F3 Tarsus (Netzsch) and the sample was heated from room temperature to 800 C
o
-1
1
13
at a rate of 5 C min under N atmosphere. H, C-NMR spectrum was recorded using a
2
Bruker Avance II 400 spectrometer. The luminescence spectra for the powdered solid
samples were measured at room temperature using a Horiba Fluorolog spectrophotometer and
the solution state fluorescence spectra were recorded using a Shimadzu-RF-6000
spectrophotometer.
Single Crystal X-ray Diffraction. The crystal and refinement data for CP-1 to CP-3 were
collected in Table 1. For all cases, a crystal of appropriate size was selected from the mother
liquor and immersed in paratone oil and then it was mounted on the tip of a glass fibre and
cemented using epoxy resin. Single crystal X-ray data were collected at 300 K on a Bruker
SMART APEX II CCD diffractometer using graphite-monochromated Mo-K radiation
α
(0.71073 Å). The linear absorption coefficients, scattering factors for the atoms and the

anomalous dispersion corrections were taken from International Tables for X-ray
2
3
Crystallography. The data integration and reduction were processed with SAINT software.
An empirical absorption correction was applied to the collected reflections with SADABS
24
25
using XPREP. The structure was solved by the direct method using SHELXTL and was
2
26
refined on F by full-matrix least-squares technique using the SHELXL-2014 program
package. For all the cases non-hydrogen atoms were refined anisotropically. Selected bond
lengths and bond angles are listed in Table S1, S3 and S5. Attempts to identify the highly
2
disordered solvent molecules in compound 1 failed. Instead, a new set of F (hkl) values with
the contribution from the solvent molecules withdrawn was obtained by using the SQUEEZE
2
7
procedure implemented in PLATON.
Scheme 1: The spacer and di-carboxylic acid linkers used to synthesize coordination
polymers in this study.
Synthesis of {[Cd(NDC)(L)]·xS} , CP-1. Cd(NO ) ·4H O (0.1 mmol, 0.031 g), H NDC (0.1
n
3 2
2
2
mmol, 0.0216 g) and L (0.05 mmol, 0.094 g) were dissolved in 2.5 mL DMF in a glass vial.
The resulting solution was stirred at room temperature for 1-2 h, filtered and the filtrate was
kept for crystallization at ambient temperature. Block shaped orange crystals were obtained
after about 7-8 days. Yield: 51%. Elemental analysis for 'C22 H13 Cd N O ', calcd: C,
4
4
5
2.83%; H, 2.57%; N, 10.99%. Found: C, 52.81%; H, 2.68%; N, 11.09%. FT-IR (KBr pellet,
−
1
cm ): 1677.2(s), 1592.7(w), 1580.7(w), 1543.3(s), 1513.0(s), 1458.9(m), 1400.5(s),
1
1
359.1(s), 1345.2(s), 1262.5(m), 1209.8(m), 1194.4(m), 1165.8(m), 1154.4(m), 1093.1(m),
043.5(m), 964.6(w), 837.2(s), 799.6(s), 698.3(s), 642.4(s), 578.1(s), 520.6(s).

Synthesis of {[Cd(2-ATA)(L)]·xS} , CP-2. It has been prepared as described for the
n
synthesis of CP-1, except that H NDC is replaced by H ATA (0.1 mmol, 0.018 g). Rhombus
2
2
shaped deep-orange crystals were obtained after about 10 days. Yield: 71%. Elemental
analysis for 'C H Cd N O ', calcd: C, 45.44%; H, 2.75%; N, 14.72%. Found: C, 45.58%;
1
8
13
5
4
−
1
H, 2.87%; N, 14.79%. FT-IR (KBr pellet, cm ): 3397.4(br), 3101.1(br), 3074.0(w),
1
8
601.3(m), 1554.1(s), 1520.1(s), 1488.4(m), 1288.3(s), 1060.2(s), 1013.8(s), 947.3(w),
70.1(s), 821.2(m), 790.4(s), 748.2(s), 731.6(s).
Synthesis of {[Cd(2-NTA)(L)]·xS} , CP-3. It is prepared as described for the synthesis of
n
CP-1, except that H NDC is replaced by H NTA (0.1 mmol, 0.022 g). block shaped orange
2
2
crystals were obtained after about 12 days. Yield: 71%. Elemental analysis for 'C H Cd N
5
1
8
11
O ', calcd: C, 42.75%; H, 2.19%; N, 13.84%. Found: C, 42.88%; H, 2.24%; N, 13.90%. FT-
6
−
1
IR (KBr pellet, cm ): 3383.9(br), 3288.3(br), 3204.1(br), 1654.5(s), 1607.2(w), 1569.7(s),
1
7
485.1(s), 1387(s), 1318.4(m), 1288.3(s), 1060.2(s), 1013.8(s), 947.3(w), 870.1(s), 821.2(m),
90.4(s), 748.2(s), 731.6(s).
Table 1. Crystal Data and structure refinements for CP 1-3
Compounds
Empirical formula
Formula weight
Temperature (K)
Radiation
Wavelength(λ)
Crystal system
Space group
a[Å]
CP1
CP2
CP3
'C H Cd N O '
'C H Cd N O '
'C H Cd N O '
2
2
13
4
4
18 13
5
4
18 11
5
6
509.76
475.73
505.72
293(2)
293(2)
293(2)
Mo-Kα
0.71073Å
Monoclinic
C2/c
Mo-Kα
Mo-Kα
0.71073Å
Monoclinic
C2/c
0.71073 Å
Monoclinic
C2/c
17.913(4)
13.312(3)
20.914(4)
90.00
17.580(4)
13.572(3)
20.782(4)
90.00
17.720(4)
13.980(3)
20.677(4)
90.00
b[Å]
c[Å]
α[°]
β[°]
117.43(3)
90.00
116.41(3)
90.00
117.99(3)
90.00
γ[°]

3
Volume[Å ]
4426(2)
8
4441(2)
8
4523(2)
8
Z
Density (calculated)
1.530
1.423
1.485
3
[
Mg/m ]
Absorption
coefficient [mm ]
1.021
1.013
1.006
-1
F(000)
2024
1888
4934
5376
2000
3824
5624
Refl. used [I > 2σ(I)] 4223
Independent
reflections
4534
Rint
0.0146
0.0201
0.0721
Refinement method
full-matrix least
squares on F
full-matrix
squares on F
least full-matrix least
2
2
2
squares on F
GOF
1.006
1.072
1.049
Final
R1 = 0.0218
R1=0.0387
R1 = 0.0639
Rindices[I>2σ(I)]
wR =0.0540
wR =0.1143
wR =0.1761
2
2
2
Results and Discussion
All the three coordination polymers were easily synthesized by acquiring the room
temperature slow evaporation process. Once the crystals were isolated it is found to be stable
at laboratory atmosphere and insoluble in common organic solvents. The formula of all the
CPs is confirmed by single-crystal X-ray diffraction, thermal gravimetric analysis (TGA) and
elemental microanalysis studies. The purity in bulk phase was confirmed by powder X-ray
diffraction (PXRD). The FT-IR study shows that each CPs exhibit multiple strong absorption
-1
bands in the region 1350–1550 cm corresponding to asymmetric and symmetric stretching
vibrations of −C=N, −N=N bonds and coordinated carboxylate groups. The absence of
-1
characteristic bands at around and above 1700 cm stipulates that there are no protonated
28
carboxylate groups in all the CPs.
The single-crystal X-ray determination on CP-1 reveals a 3D coordination framework
2
-
constituted by NDC and N,N'-donor spacer L. CP-1 crystallizes in monoclinic crystal
system with C2/c space group in which the asymmetric unit is consisted of one Cd(II) metal
ion, one deprotonated naphthalene dicarboxylic acid and one L spacer (Figure S1). Each
Cd(II) atom is seven-coordinated with two nitrogen atoms ligated from two different L spacer
2
-
in axial position and five oxygen atoms from three NDC and thus giving rise a distorted

pentagonal bipyramidal configuration {CdO N } (Figure 1a). The Cd–O bond distances
5
2
range from 2.2952(17) to 2.4852(18) Å whereas the Cd–N bond distance ranges from
.3721(18) to 2.3741(18) Å (selected bond distances and angles of CP-1 are listed in Table
S1). Two different coordination modes have been adopted by two carboxylate groups of
2
2
-
NDC ligands, one is bidentate chelating mode and the other is monodentate chelating
fashion (Scheme 2). Two
Figure 1. (a) Coordination environment around Cd(II) in CP-1. Color code: Cd, yellow; N,
2
-
blue; O, red; C, grey; H atoms are omitted for clarity. (b) Five coordinated NDC units with
Cd(II) unit to form a 2D layered network. (c) A representation of overall 3D structure along
crystallographic ‘b’ axis. (d) The topological representation of CP-1 showing overall
framework with the rare ‘rob’ topology.
2
-
Cd(II) centers are bridge by two carboxylate groups of NDC ligands to generate a dimeric
Cd (COO) core unit (Figure S2) resulting the formation of a 1D chain structure along the
2
2
crystallographic ‘c’ axis (Figure 1b). The distance between two Cd(II) in the dimeric unit is
.776 (2) Å. The pyridyl N atoms of the spacer L connect the Cd (COO) unit in both the
3
2
2
directions to establish the overall 3D network (Figure 1c). The resultant 3D framework
contains the solvent molecules capped in the 1D channel oriented along ‘b’ axis (Figure 1c).

Moreover, the framework of CP-1 can be simplified to a 3D uninodal, 6-connected a rare
8
6
‘
rob’ topology with the point symbol {4 .6 .8} as depicted in Figure 1d. Weak π····π stacking
interaction (centroid to centroid distance of 3.670(2) Å) among the adjacent pyridine moieties
of spacer L and several non-covalent intermolecular interactions among the ligands further
stabilized the framework (Table S2).
(a)
(b)
(c)
Scheme 2: Similar binding modes in different dicarboxylic acid linkers of (a) CP-1, (b) CP-2
and (c) CP-3. Color code: Cd, yellow; N, blue; O, red; C, grey; H, white.
For the other two structures, the asymmetric unit of CP-2 and CP-3 consist of one
2
-
2-
Cd(II) metal ion, one spacer L, and one deprotonated ATA or NTA forming the neutral
network with molecular formula {[Cd(2-ATA)(L)]·xS} and {[Cd(2-NTA)(L)]·xS} as
n
n
depicted in Figure S3. The coordination environment around the Cd(II) ions for CP-2 and
CP-3 is identical to that of CP-1 (Figure 2a and 2b respectively) and thus making
isostructural frameworks. Overall, the pyridyl N atoms of the spacer L connect to the
2
-
2-
deprotonated ATA or NTA in a crisscross fashion to from 3D networks in which the
metal-dicarboxylate units are oriented in spiral fashion along crystallographic ‘c’ axis where
the -NO and -NH functional groups are remains uncoordinated (Figure 2c). The Cd–O bond
2
2
distances range from 2.328(4) to 2.379(4) Å whereas the Cd–N bond distance ranges from
.289(5) to 2.304(4) Å (selected bond distances and angles of CP-2 and CP-3 are listed in
2
Table S3 and S5). Weak π····π stacking interaction (centroid to centroid distance is 3.660 (2)
for CP-2 and 3.778 (2) for CP-3) among the adjacent pyridyl moieties of spacer L and
several non-covalent intermolecular interactions among the ligands further stabilized the
framework as was observed for CP-1 (Table S4 and S6). All the di carboxylates adopts a
similar kind of binding nature to Cd(II) metal center (scheme 2).

Figure 2. Coordination environment around Cd(II) in CP-2 (a) and CP-3 (b). A
representation of overall 3D structure along crystallographic ‘c’ axis and selected portion is
2
-
the 2D layer framework constructed by Cd-2-NTA units in CP-3 (c). Color code: Cd,
yellow; N, blue; O, red; C, grey; H, white.
To investigate the purity of the crystals in bulk phase PXRD experiment was carried
out for all of the three samples. The as-synthesized and the simulated patterns of PXRD are in
good agreement with each other as depicted in Figure 3. To study the thermal behavior,
thermo gravimetric analysis (TGA) has been carried out from 30 °C to 800 °C in the nitrogen
atmosphere with a heating rate 5 °C per min as depicted in Figure S5-S7. TGA of the as-
synthesized CP-1 indicates that the material is stable until 300 °C. Beyond this, the expulsion
of the organic ligand and spacer occurs and further heating to 800 °C reveals continuous
weight losses. TGA of as-synthesized CP-2 shows that a weight loss of 15.5% occurs at 167
°
C which can be attributed to the loss of two lattice DMF molecules. The framework is stable
until 300 °C and after that, the decomposition started gradually. TGA on the as-synthesized
CP-3 indicates similar nature as that of CP-2. A weight loss of 11.7% occurs at 180 °C which
can be attributed to the loss of two lattice DMF molecules. The framework is stable until 280
°
C and after that the expulsion of the organic ligand and spacer occurs.

Figure 3: PXRD patterns of simulated and as synthesized CPs.
1
0
Coordination polymers based on d metal ions are generally appraised as a promising
alternative for luminescent or photoactive substance having several potential applications
1
5-18,
such as chemical sensor, photochemical materials, and nonlinear optical (NLO) devises.
2
9
The emission spectra of all the three CPs and the corresponding dicarboxylic acids and
spacer L, have been investigated in solid state at room temperature as depicted in Figure S11.
When CP-1 is excited in 275 nm it displays an emission peak at 379 nm that can be attributed
to π* → π and π*→ n transitions of the spacer and the linker (i.e. intra ligand charge transfer
3
0,31
transition as well as the ligand to ligand charge transfer transition (LLCT)).
On the other
hand, when CP-2 is excited at 270 nm it displays an emission peak at 419 nm that can be
attributed to π* → π and π*→ n transitions of the conjugated ligands. For CP-3 the
luminescence emission maximum at 415 nm (λ = 310 nm) could be attributed to π* → π and
ex
π*→ n transitions rather than ligand to metal and/or metal to ligand charge transfer
31
transitions.

Figure 4: emission profile of CP 1-3 in different solvents.
Considering this emission property of the spacer and the organic co-ligands, we have
investigated the fluorescence sensing property in various solvent systems for all the CPs. For
this, the standard solution of all the materials have been prepared by adding a finely grounded
sample of CP 1-3 dispersed in a range of often used common organic solvents such as
acetone, acetonitrile, chloroform, DMSO, DMF, EtOH, MeOH, THF, DCM, as well as
nitromethane, and nitrobenzene. All the solutions are ultrasonically stirred for 2h to form a
stable suspension to examine their photoluminescence properties. The solvent dependent
experiments for all the CPs are performed to a 2 mL of CP-1 or CP-2 or CP-3 in
aforementioned solvents and subsequently measuring the luminescence spectra respectively.
As depicted in figure 4 the photoluminescence intensity of CP 1-3 is greatly dependent on the
nature of the solvents. The maximum emission was observed in DMF for CP-1, in methanol
for CP-2 and in THF for CP-3. On the other hand, in nitro methane (NM) and nitrobenzene
(NB) most significant quenching effect was observed for all of the three complexes. The

quenching in luminescence intensity is almost 100 % for NM and NB. This phenomena may
3
2
be ascribed to the absorption of the light source energy and also the difference in the LUMO
3
3
energy levels of the different solvents. These observations reveal the ability of CPs for the
detection of toxic nitro compounds. Such type of solvent dependent luminescence spectra
1
1-14, 31
have also been observed for other CPs.
From the luminescence spectra of CP-1 and
CP-3 marked red and blue shifts from their highest intense emission maxima could be
1
1-14, 31
observed for different solvents compared to the small shifts observed for CP-2.
Conclusions
In this contribution, we present three new isostructural 3D CPs based on an azo
linked N, N donor spacer with different dicarboxylates which are successfully synthesized
and structurally characterized. All the coordination polymers possess 3D structures having a
8
6
rare ‘rob’ topology with the point symbol {4 .6 .8}. The luminescence investigation in
different common organic solvents on all the materials manifested the role of solvents in
luminescent intensity. Also, the luminescence intensity for all the CPs shows almost full
1
0
quenching effect in nitro solvents. Given that d transition metals are highly abundant and
rich library of conjugated as well as different functional group containing organic linkers and
spacers for construction of functional CPs, this work may contribute to extend the potential
applications of Cd(II) based luminescent CPs.
Appendix A
Supplementary Data
CCDC 1844653 to 1844655 contains the supplementary crystallographic data for CP-1
to
CP-3
.
These
data
can
be
obtained
or
free
of
the
charge
via
http://www.ccdc.cam.ac.uk/conts/retrieving.html,
from
Cambridge
Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: (+44)
223-336-033; or e-mail: deposit@ccdc.cam.ac.uk.
1
Crystallographic data, PXRD, TGA patterns, additional Figures related to sensing
experiments (PDF) associated with this article.
Keywords: azo functionalized N,N' spacer, coordination polymers, nitroaromatics,
photoluminescence, ‘rob’ topology.
iD
ORCID
Madhab C. Das: 0000-0002-6571-8705
Acknowledgments

S.C. thanks IIT KGP for SRF fellowship. M.C.D. gratefully acknowledges the financial
support received from SERB, New Delhi as Early Carrier Research Award
(ECR/2015/000041).
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Graphical Abstract-Pictogram

Graphical Abstract-Synopsis
Three isostructural 3D luminescent Cd(II) based coordination polymers (CP 1-3) with
predefined functional sites have been synthesized. Their solvent dependent
photoluminescence studies have been executed, showing quenching behavior in nitro
aromatic solvents.