Fluorescent metal-organic frameworks for selective sensing of toxic cations (Tl3+, Hg2+) and highly oxidizing anions ((CrO4)2?, (Cr2O7)2?, (MnO4)?)

Article abstract of DOI:10.1002/cplu.201700277

The ligand 4,4′‐(benzothiadiazole‐4,7‐diyl)dibenzoic acid was synthesized and employed for the synthesis of two metal-organic framework (MOF) compounds, [Mn₄(C₂₀H₁₀N₂O₄S)₂(HCOO)₄(DEF)₂] (I; DEF=N, N′‐diethylformamide) and [Pb(C₂₀H₁₀N₂O₄S)(DMF)] (II; DMF=N,N′‐dimethylformamide). Single‐crystal structure studies revealed that compound I has a three‐dimensional structure and compound II has a two‐dimensional structure. The luminescent nature of the MOFs was gainfully employed as a probe for the detection of highly toxic metal ions such as Tl³⁺ and Hg²⁺. The detection limits were found to be in the parts per billion (ppb) level. The presence of an unsubstituted thiadiazole ring in the ligand appears to help in the detection of these highly toxic metal ions in solution as the metal ions interact with S, which was revealed by Raman spectroscopic studies. The compounds were also found to be good candidates for the detection of highly oxidizing anions such as chromate, dichromate, and permanganate, again in ppb levels of concentration in solution. Magnetic studies on compound I indicate antiferromagnetic behavior. The variable‐temperature electrical conductivity studies indicate a semiconducting nature with comparable behavior to well‐known semiconductors such as CdSe, ZnTe, and GaP.

Full text of DOI:10.1002/cplu.201700277

Accepted Article
Title: Fluorescent MOFs for selective sensing of toxic cations (Tl3+,
Hg2+), ánd highly oxidizing anions [(CrO4)2−, (Cr2O7)2−,
(MnO4)−]
Authors: Srinivasan Natarajan and Mr. Ajay Kumar Jana
This manuscript has been accepted after peer review and appears as an
Accepted Article online prior to editing, proofing, and formal publication
of the final Version of Record (VoR). This work is currently citable by
using the Digital Object Identifier (DOI) given below. The VoR will be
published online in Early View as soon as possible and may be different
to this Accepted Article as a result of editing. Readers should obtain
the VoR from the journal website shown below when it is published
to ensure accuracy of information. The authors are responsible for the
content of this Accepted Article.
To be cited as: ChemPlusChem 10.1002/cplu.201700277
Link to VoR: http://dx.doi.org/10.1002/cplu.201700277
A Journal of
www.chempluschem.org

ChemPlusChem
10.1002/cplu.201700277
FULL PAPER
3
+
Fluorescent MOFs for selective sensing of toxic cations (Tl ,
2
+
2−
2−
−
Hg ), highly oxidizing anions [(CrO
4
) , (Cr
2
O
7
) , (MnO ) ]
4
[a]
*[a]
Ajay Kumar Jana, and Srinivasan Natarajan
*
Corresponding Author, E-mail: snatarajan@sscu.iisc.ernet.in
This article is protected by copyright. All rights reserved.

ChemPlusChem
10.1002/cplu.201700277
FULL PAPER
Abstract: The ligand 4,4′-(benzothiadiazole-4,7-diyl) dibenzoic acid
intensity when the analyte molecules or ions interact.[17,18] The
selectivity as well as sensitivity depends on the available
electron density at the MOFs. Normally, electron rich π-
conjugated fluorescent ligands make an excellent candidate for
fluorescence based sensing.[19, 20]
was synthesized and employed for the synthesis of two metal
organic
Mn
framework
S) (HCOO)
(MOF)
compounds,
[
4
(C20
H N O
10 2 4
2
4
(DEF)
2
], I and [Pb(C20H N O S)(DMF)],
10 2 4
II. Single crystal structural studies reveal that compound I has a
three dimensional structure and compound II has a two dimensional
structure. The luminescent nature of the MOF was gainfully
employed as a probe for the detection of highly toxic metal ions such
Another approach to detect heavy metal ions such as
mercury, cadmium, thallium etc. could be to utilize the affinity of
the metal ions to specific functionality in the organic ligand. In
3+
2+
[21]
as Tl and Hg ions. The detection limits were found to be in the
ppb level. The presence of free S of the ligand appears to help in the
detection of these highly toxic metal ions in solution as the metal
ions interacts with S, which was revealed employing Raman
spectroscopic studies. The compounds were also found to be good
candidates for the detection of highly oxidizing anions such as
chromate, dichromate and permanganate again in ppb levels of
concentration in solution. Magnetic studies on compound I indicate
antiferromagnetic behavior. The variable temperature electrical
conductivity studies indicate semiconducting nature with comparable
behavior to the well known semiconductors such as CdSe, ZnTe,
GaP etc.
this direction, one can attempt to utilize the HSAB theory,
which would form a good basis for the detection of such metal
ions. It may be noted that the majority of the toxic heavy metal
ions are classified as soft acids. It may be possible to design
suitable ligands containing soft bases such as sulfur, nitrogen
etc., which would facilitate favorable interactions between the
toxic metal ions and the soft bases leading to changes in the
fluorescence intensity of the compounds.
Using these strategies, we have developed the ligand, 4,4′-
(benzothiadiazole-4,7-diyl) dibenzoic acid (Scheme -1), as
possible linker for the preparation of MOFs. Our efforts were
successful and we have prepared two new MOF compound,
[
[
Mn
4
(C20
Pb(C20
H
10
N
2
O
4
S)
2
(HCOO)
4
(DEF)
2
]
(I),
H
10
N
2
O
4
S)(DMF)] (II) and explored them for possible use
as functional sensors for metal ions, anions and adsorbents for
harmful dye molecules. In this paper, we present the synthesis,
structure, selective detection of toxic metal ions such as thallium
Introduction
The detection of toxic metals in solution is emerging to be an
important area of study. Currently, much effort is being devoted
to the rapid detection of many hazardous chemicals that include
dangerous explosives and toxic metal ions.[1-6] It becomes
important that the detection of hazardous chemicals needs to be
both rapid as well at lower concentrations (trace). A number of
different techniques have been employed in this direction and
the electrochemical method appears to be the dominate one.[7-9]
The electrochemistry based approaches, however, require
considerable care in the preparation of suitable electrodes and
the method, in general, are cumbersome and expensive.
Fluorescence based methods offer excellent alternate
approaches towards the detection of heavy toxic metals such as
mercury.[
3+
2+
(
Tl ) and mercury (Hg ) as well as the detection of chromate,
dichromate and permanganate ions from water at room
temperature.
Results and Discussion
Structure of [Mn
compound crystallizes in P2
unit consists of four crytallographically independent Mn2+ ions
Mn1, Mn2, Mn3 Mn4), two N, N’- diethyl formamide molecules,
4
(C20
H
10
N
2
O
4
S)
2 4 2
(HCOO) (DEF) ], (I) . The
1
/c space group and the asymmetric
(
four formate and two 4,4′-(benzothiadiazole-4,7-diyl) dibenzoate
ions. Each ligand is bonded to four Mn2 ions (Mn1, Mn2, Mn3,
Mn4) (Figure S1a in the Supporting Information). All the
manganese centers are octahedrally coordinated with oxygens
from the carboxylate, formate and N, N’- diethyl formamide
+
10-12]
Metal-organic framework (MOF) compounds have been
explored extensively for many promising applications such as
catalysis, sorption, chemical sensors etc.[13,14] In this connection,
the possibility of incorporating new fluorescent ligands, that can
selectively bind heavy metals, as part of the MOF framework
can open up many interesting new avenues. Thus, many
luminescent MOFs have been developed over the years as
potential candidates for chemical sensors.[15,16] The luminescent
MOFs exhibits considerable changes in their luminescent
(
Figure S1b in the Supporting Information). The formate ion in I
resulted by the hydrolysis of N, N’- diethyl formamide employed
as the solvent during the synthetic conditions. Similar hydrolysis
of N, N’- dimethyl formamide molecules forming formic acid have
been reported earlier.[ The Mn–O bond lengths are in the
range of 2.075(3) - 2.306(3) Å, (Average = 2.188 Å) and O-Mn-O
bond angles are in the range 71.90(10)° and 175.56(11)° Table
S1 in the Supporting Information). The manganese atoms, Mn1
and Mn2 are bridged by the formate ions forming –Mn–O–Mn–
dimers (Figure S2a in the Supporting Information), which are
22]
[
a]
A. K. Jana, Prof. Dr. S. Natarajan
Framework Solids laboratory
Solid State and Structural Chemistry Unit
Indian Institute of Science, Bangalore–560012 (India)
Fax: (+91) 80-2361-1310
connected together forming a right handed helical one
dimensional manganese formate chain (Figure 1a). The right
handed helical one dimensional manganese formate chains are
bridged by another formate, which connected to a left - handed
helical –Mn–O–Mn– formate chains forming a –Mn–O–Mn– two
dimensional layer (Figure 1b). Identical two dimensional –Mn–
E-mail: snatarajan@sscu.iisc.ernet.in
Supporting information for this article is given via a link at the end of
the document.
This article is protected by copyright. All rights reserved.

ChemPlusChem
10.1002/cplu.201700277
FULL PAPER
O–Mn– layers are also formed involving Mn3 and Mn4 atoms
fashion. The bound DMF molecules hang from the metal centers
in the inter-lamellar region (Figure 2c). The presence of free N
and S atoms and in close proximity (N∙∙∙S distance = 3.216 Å)
suggests some non-covalent N∙∙∙S interactions between the
layers.
(
Figure S2b, S2c, S2d and S2e in the Supporting Information).
The two –Mn–O–Mn– layers (Mn1-Mn2 and Mn3-Mn4) are
connected together by the 4,4′-(benzothiadiazole-4,7-diyl)
dibenzoate giving rise to the three dimensional structure (Figure
1c). The overall arrangement of the structure gives rise to C-H∙∙∙
π
interactions (Figure S3, Table S2 in the Supporting
Information).
Scheme 1. The reaction scheme employed in the synthesis of 4,4′-
(benzothiadiazole-4,7-diyl) dibenzoic acid ligand.
SOCl2
Br
Br
NH2 Et N
N
N
Br2
N
N
3
S
S
NH2 CH Cl2
HBr
2
O
O
HO
O
KOH
THF
MeOH
Pd(PPh3)4
Br
Br
B(OH)2
K CO3
2
N
N
N
H O
N
N
2
S
S +
S
1
9
,4-Dioxane
0°C
N
90°C
1
2h
COOCH3
HCl
N atm
2
3
days
O
O
HO
O
(
a)
(b)
Structure of [Pb(C20
crystallizes in P2 /n space group and the asymmetric unit
consists of one crytallographically independent Pb2+ ion, one N,
N’- dimethyl formamide molecule and one 4,4′-
benzothiadiazole-4,7-diyl) dibenzoate ion. The Pb center is
10 2 4
H N O S)(DMF)], (II). The compound
1
(
coordinated with eight oxygen atoms from the carboxylate and
DMF forming a bicapped distorted octahedral geometry (Figure
S4 in the Supporting Information). The Pb–O bond lengths are in
the range of 2.471(3)-2.912(4) Å, (Average = 2.682 Å). Of the
eight Pb–O bonds, we observed three bonds are much longer in
the range of 2.863(3)–2.912(4) Å. The longer bonds may be
considered as secondary interactions and similar bond distances
have been observed earlier.[23, 24] A detailed bond valence sum
calculations[25] (Table S3 in the Supporting Information) for the
Pb-O bonds gave a value of 1.564 when only five shorter Pb-O
bonds were considered. On considering the longer Pb-O bonds,
we obtained a valence sum of 1.925, which suggested that the
Pb is indeed 8-coordinated. The ligand, 4,4′-(benzothiadiazole-
(
c)
Figure 1. (a) The -Mn-O-Mn- connectivity through the formate units forming
the right handed one dimensional helical manganese formate chain, (b) The
connectivity between the right handed helical -Mn-O-Mn- chain and the left
handed helical -Mn-O-Mn- chains forming the two dimensional layer, (c) The
three dimensional structure of compound I.
4,7-diyl) dibenzoic acid bonds with the five metal centers
through the carboxylate oxygen (Figure S4 in the Supporting
Information). The lead centers are connected by the carboxylate
oxygens forming a 4-membered ring, which resembles the
secondary building unit, SBU-4, proposed to understand the
metal phosphate structure.[26] The SBU-4 units are connected
through their edges forming a one-dimensional -Pb-O-Pb- chain
Optical studies. Solid state UV-Vis spectroscopic studies
(
Figure 2a). Similar SUB-4 units connecting to form a one-
indicated that the ligand exhibits absorption bands at ~ 215 nm,
~
251 nm, ~ 289 nm, which can be assigned to the π-π*
dimensional chains have been observed in an iron arsenate
structure.[27] The one-dimensional -Pb-O-Pb- chains are
connected through the ligand, 4,4′-(benzothiadiazole-4,7-diyl)
transitions. The absorption band at ~ 435 nm could be due to the
n-π* transition. Both the compounds (I and II) also exhibited
similar absorption bands at ~ 214 nm, ~ 255 nm, ~ 315 nm,
which could be due to the π-π* transition and the absorption
dibenzoic acid forming a two-dimensional layer structure (Figure
2b). The two-dimensional layers are arranged in a AAA…..
This article is protected by copyright. All rights reserved.

ChemPlusChem
10.1002/cplu.201700277
FULL PAPER
band at ~ 430 nm may be due to the n-π* transitions (Figure S5
in the Supporting Information). Solid state luminescence for both
the compounds (I and II) as well as the ligand were excited
employing a wavelength of 420nm. In all the cases, we observed
a single emission peak centered around ~500nm for the
compounds (I) and (II). This band may be due to the π*-π
transition of the ligand (Figure S6 in the Supporting Information).
Similar bands have been observed and reported in the
literature.[28]
Thermogravimetric Analysis. Thermogravimetric analysis
(TGA) were carried out in oxygen atmosphere (flow rate = 40
mL/min) in the temperature range 30−800 °C (heating rate =
10 °C/min). For compound I we observed a three-step weight
loss. The first step weight loss in the temperature range (245-
350°C) was 29% (Figure S8 in the Supporting Information),
which corresponds to the loss of two DEF molecules and four
formate ions (calculated weight loss 28.3%). The second more
sharper loss in the temperature range 350-375°C is followed by
a broader tail that extends upto 550°C. The total observed
weight loss in this temperature range was ~ 59.4%, which
corresponds to the loss of two ligands (calculated weight loss
55.5%). The final calcined product was found to be Mn
2 3
O
(
JCPDS No: 89-2809) (Figure S29a in the Supporting
Information). For compound II a small initial weight loss was
observed around 200°C followed by a sharp weight loss at
4
10°C. The total observed weight loss was found to be ~ 65 %,
which corresponds to the loss of DMF and the carboxylate unit
cal. 68.8 %). The final calcined product was found to be a
mixture of Pb (JCPDS No: 89-1947) and PbS (JCPDS No:
7-0244) (Figure S29b in the Supporting Information).
(
(
a)
3 4
O
7
Magnetic Studies. Compound I contains Mn and we carried out
the study of the magnetic behavior in the temperature range
3
00-2K (Figure 3a). The magnetic susceptibility increases slowly
from 300K up to 10K and then exhibits a sharp increase (Figure
S10 in the Supporting Information). The room temperature χ
m
T
−
1
value (1000 Oe) was found to be 17.34 emu mol K, which is
close to the expected spin only χ
T values for four Mn2+ ions
17.48 emu mol−1 K). The high temperature magnetic data was
fitted to a Curie-Weiss behavior in the temperature range 50-300
K, which gave a θ value of −36.41 K (inset Figure 3a). The
negative value for the θ suggests that the magnetic centers are
m
(
p
(
b)
p
anti-ferromagnetically coupled. The magmetic behavior was
initially modeled using the Fischer’s expression for the dimer
interactions (Figure 3b).
B B
χHT = A exp(-∆/k T)/k T
The fitting was latter modified incorporating the term, τ, which
accounts for the anti-ferromagnetic interactions at lower
temperature.
B B
HT = A exp(-∆/k T)/(k
T)τ
χ
A value for τ = 0.859, gave a good agreement with the
experimental data (Figure 3b). This exponent, τ, provides an
idea regarding the optimum length scale of the exchange
process in the system in the temperature range 300-10K. Below
10 K, the susceptibility value increases sharply, indicating
possible ferromagnetic interactions in the low temperature
region. The magnetic behavior may be explained from a
structural perspective. As mentioned earlier, manganese centers
are bridged through the oxygen atoms (O11, O12, O14) with -
Mn-O-Mn anlges in the range 98.94(11)°-115.21(12)°, which
would suppport the antiferromagnetic interactions.[ Below 10K,
the interactions between Mn-centers involving the formate
bridges would be more dominant compared to the carboxylate
bridged interactions giving rise to the possible ferromagnetic
exchanges (Figure S11 in the Supporting Information). A low
temperature and low magnetic field M-H study at 2K exhibited a
29]
(
c)
Figure 2. (a) View of the one-dimensional -Pb-O-Pb- chain in II, the SUB-4
unit is highlighted (see text) (b) The connectivity between the -Pb-O-Pb-
chains through the carboxylate forming the two-dimensional layer structure, (c)
10 2 4
The arrangement of layers of II, [Pb(C20H N O S)(DMF)].
This article is protected by copyright. All rights reserved.

ChemPlusChem
10.1002/cplu.201700277
FULL PAPER
small hysteresis loop (Figure S12a in the Supporting
Information), suggestive of ferromagnetic exchanges. At higher
applied fields, the M-H loop (Figure S12b in the Supporting
Information) was not observed suggesting that the Mn-centers
could exhibit frustration. Similar magnetic behaviour has been
observed in Mn-containing MOF compounds.[30]
Mn-compound and 10-8 S/m for Pb-compound. The conductivity
values for both the compounds increases exponentially with
decreasing temperature (Figure S13 in the Supporting
Information). The conductivity data was fitted to an Arrhenius
plot, which gave values of the activation energy (Ea) as 0.27 eV
for I and 0.24 eV for II. The activation energies indicate that the
compounds could be semi-conducting and the conductivity could
be due to the thermally generated carriers with variable-range
hopping. The optical band gap of the compounds were also
obtained from the diffuse reflectance data using the
Kubelka−Munk (KM) method [ [which is given by the following
33]
2
equation: F(R) = [(1-R) ]/2R, where R is the reflectance, F(R) is
the KM function]. From the Tauc Plot ([F(R) ×hυ]1/2 vs hυ), the
band gap values were found to be 2.41 eV for I, 2.42 eV for II
and 2.47 eV for the ligand (Figure S14 in the Supporting
Information). As can be noted, the band gap values for the
present compounds is comparable with some of the well-known
semiconductor materials, such as CdSe, CdTe, ZnTe, GaP,
etc.[34-36]
Metal ion sensing. The present compounds possess free S and
N functionality, which may be exploited. Both S and N can be
considered as soft bases, according to the HSAB theory [21] and
may facilitate binding of heavier and toxic chemicals. To this end,
we have attempted metal sensing studies using both the
compounds by simple fluorimetric analysis. In a typical study, 1
(
a)
2
+
2+
2+
2+
mM solution of the respective metal ions (Mg , Mn , Fe Co ,
2
+
2+
2+
+
2+
2+
+
3+
2+
Ni , Cu , Zn , Ag , Cd , Hg , Tl , Tl , Pb ) and 3mg of the
compound I and II dispersed in 15 mL of water was taken. For
the fluorescence measurements 2.5mL of the MOF solution was
taken and an excitation wavelength of 420nm was employed.
The metal ion detection studies were carried out by the
incremental addition of the metal ions solution to the MOF
dispersed solution. The variations in the fluorescence intensity
was monitored and measured as a function of the quantity of
addition of the metal ion solution. We observed a gradual
decrease in the fluorescence intensity on addition of Tl3+ and
Hg2+ solutions (Figure 4). The fluorescence intensity, however,
did not change significantly in case of other common metal ions
(
Figure 5). The effect of fluorescence quenching was analyzed
(
b)
by the Stern-Volmer equation, I /I = 1+KSV[M], where I and I are
0
0
the emission intensities in the absence and presence of the
metal ions, respectively, [M] is the concentration of the metal
ions, Ksv is the Stern–Volmer constant. The value of Ksv was
Figure 3. (a) The thermal variation of χ
m
T for compound I. Inset shows the
1
/χ vs. T plot (b) Temperature variation of the magnetic susceptibility (solid
m
black line) with the high temperature data fitted to the Fisher’s formula (blue
line; τ = 1.0, red line; τ = 0.859) (see text).
determined from the slope of I
0
/I vs. [M] plot (Figure S15 in the
Supporting Information). The Ksv values were found to be
1
95270 M-1 and 21000 M for Tl and Hg2+ for I and 21900 M-1
-1
3+
-1
3+
2+
and 3300 M for Tl and Hg for II. The larger Ksv value
suggests better sensitivity of the present compounds towards
the detection of Tl3+ and Hg2+ ions in solution. The possible
recycling of these compounds for the detection of Tl3+ and Hg2+
ions was attempted and the quenching efficiency of the
fluorescence intensity was followed employing the relationship,
Electrical property. There has been considerable interest in the
study of organic semiconductors based on benzothiadiazole due
to their applications in the area of organic field effect transistors
OFETs).[31,32] Since the present compounds posses some of
(
these aspects, we desired to explore the DC electrical
conductivity of those compounds in the range 200-300K. For this
study, the single crystals were powdered and pressed into
pellets of 0.4 cm in diameter (thicknesses of 0.034−0.045 cm)
and silver paint was coated on both sides. The conductivity
values at 300K were found to be in the range of 10-10 S/m for the
0 0 0
[(I − I)/I ] × 100 (%), where I is the initial emission intensity and
I is the intensity after the addition of the metal solution. The
quenching efficiency for the repetitive measurements appears to
be similar to the fresh sample for the detection of Tl3+ ions,
This article is protected by copyright. All rights reserved.

ChemPlusChem
10.1002/cplu.201700277
FULL PAPER
whereas the quenching efficiency reduces for the detection of
Hg2+ (Figure S16 in the Supporting Information). The detection
limits for both the ions were estimated and we find that the
identification of these toxic metal ions more precisely. To this
end, we have employed a number of metal ions in solution such
2
+
2+
2+
2+
2+
2+
2+
+
2+
2+
+
as Mg , Mn , Fe , Co , Ni , Cu , Zn , Ag , Cd , Pb , Tl
3
+
2+
3+
2+
detection limit was 146 ppb for Tl , 432 ppb for Hg (I) whereas
along with Tl and Hg ions (Figure 6). From the plot, it is clear
that the compound I and II is not only sensitive but also selective
to Tl3+ and Hg . From the Ksv values it is clear that the Mn-
3
+
2+
it was 629 ppb for Tl , 1.82 ppm for Hg (II)(Table S5 and
2+
Figure S17 in the Supporting Information). The detection limits
2
+
observed for the Hg ions in solution is comparable to those
compound exhibits better detection sensitivity compared to the
reported before.[
37, 38]
The limits of detection for the Tl ions are
3+
Pb-compound. In both the compounds, the Tl
3+
ions are
high and the sensitivity remaining more or less constant on
repetitive use of the MOF suggests that the present compounds,
especially I, could be an excellent sensor for Tl3+ ions.
We have also attempted to investigate the selectivity of the
present compounds towards both Tl3+ and Hg2+ ions in the
presence of other metal ions in solution. This would facilate
detected more readily compared to the Hg2+ ions. The relative
acidities of Tl3+ vs. Hg2+ ions in solution (both are soft acids
according to the HSAB principle)[39] and their interaction with the
free S atom present in the ligand would have played an active
role in the detection of these ions. We believe that the detection
of these ions proceeds via the soft-acid soft-base idea of
Pearson.[21]
1
000
1000
3
+
0 µL
0 µL
50 µL
2
+
I + Tl
I + Hg
5
1
2
3
5
µL
5 µL
5 µL
5 µL
0 µL
100 µL
150 µL
200 µL
250 µL
300 µL
400 µL
500 µL
600 µL
8
6
4
2
00
00
00
00
0
800
75 µL
6
4
2
00
00
00
0
1
1
1
00 µL
25 µL
50 µL
4
00
450
500
550
600
650
700
4
00
450
500
550
600
650
700
Wavelength (nm)
Wavelength (nm)
(
a)
(
b)
0
µL
2+
6
5
4
3
2
1
00
00
00
00
00
00
3+
600 II + Hg
0 µL
II + Tl
10 µL
1
2
00 µL
00 µL
5
1
1
2
0 µL
00 µL
50 µL
00 µL
5
4
3
2
1
00
00
00
00
00
0
300 µL
4
5
6
00 µL
00 µL
00 µL
250 µL
3
4
5
00 µL
00 µL
00 µL
0
4
00
450
500
550
600
650
700
400
450
500
550
600
650
700
Wavelength (nm)
Wavelength (nm)
(c)
(d)
Figure 4. Luminescence titrations between the Mn-compound (I): (a) Tl3+ and (b) Hg2+; For the Pb-compound (II): (c) Tl3+ and (d) Hg2+
.
This article is protected by copyright. All rights reserved.

ChemPlusChem
10.1002/cplu.201700277
FULL PAPER
To confirm and validate this idea, we sought to employ Raman
spectroscopy studies. For the 2,1,3-benzothiadiazole molecule,
the Raman scattering peak of the N-S bond appears in the
region of 840-860 cm- on excitation using 514 nm
wavelength. We have employed the same excitation in the
Raman spectroscopy analysis of I and II as well as Tl3+ and Hg2+
adsorbed compounds (for this study the compounds I and II
3 3 2
were allowed to be in contact with 10 mM Tl(NO ) and HgCl
solution overnight and the solution was decanted and dried
under vacuum). The N-S scattering peak in the Raman spectra
1
-1
3+
2+
appears at 840 cm for I and for the Tl and Hg adsorbed I
[
40]
give peaks at 826 cm-1 and 824 cm , respectively. For
compound II the N-S scattering peak appears at 844 cm and
the Tl3+ and Hg2+ adsorbed II exhibit peaks, at 829 cm-1 and 835
-1
-1
(
a)
(b)
Figure 5. The comparison of the fluorescence quenching intensity among the metal ion solutions investigated in the present study: (a) Mn-compound (I), (b) Pb-
compound (II).
Figure 6. Figure shows the selectivity of the MOF compounds (I and II) towards Tl3+ and Hg2+ ions in the presence of other metal ions in solution.
This article is protected by copyright. All rights reserved.

ChemPlusChem
10.1002/cplu.201700277
FULL PAPER
cm-1 respectively (Figure 7). This clearly indicates that the N-S
Anion sensing. Once the toxic metal ion sensing based on the
interactions between S and the metal ions was established, we
wanted to explore whether the present compounds are also
useful for the sensing of anions as well. Anion sensing studies
using MOFs have been reported earlier.[41] Of the many common
anions, we were particularly interested to learn whether the
present compounds would be useful for sensing highly oxidizing
3
+
bond of the ligand is affected during the adsorption of Tl and
2
+
Hg ions. It is likely that there are interactions between the
sulfur of the N-S bond and Tl3+ / Hg , which would be
responsible for this. This study indicates the presence of free N
and S functionality in the ligand aid in the detection of Tl3+ and
Hg2+ ions in the solution. Further the stability of the MOF
compounds were examined by PXRD (Figure S18 in the
Supporting Information).
2+
2−
2−
anions such as chromate (CrO
4
) , dichromate (Cr
2
O
7
)
and
−
permanganate (MnO
4
) . It is known that the permanganate ions
act as pesticide [42] and other related uses. Overexpose to Mn
ion can affect the central nervous system (neurotoxicity) through
accumulation of the metal ion in brain tissue leading to
Parkinson disease.[43] Hexavalent chromium has been well
established as a genotoxic carcinogen. Human exposes to Cr6+
ions are at increased risk of developing lung cancer, asthma or
damage to nasal epithelia and skin.[ Their concentrations in
the environment needs to be monitored and controlled. Thus,
the upper limit for the presence of Cr6+ and Mn7+ ions in solution
needs to 50 ppb and 100 ppb, respectively.[45] In this connection,
it may also be noted that the chromate anions are routinely
employed by leather industries for tanning and related
purpose.[ Their presence in the effluents needs to be checked
for the prevention of complete environmental damage.
4+
As part of this study, we desired to explore whether the present
+
compounds can also be employed to detect Tl ions in solution.
To this end, we carried out an experiment similar to the study
employed for the detection of Tl3+ and Hg2+ ions. The studies
indicated a small sensitivity for Tl+ ions with compound I,
whereas compound II exhibited even poorer sensitivity (Figure
S19 in the Supporting Information). This suggests that the
present compounds are selective towards the detection of Tl3
and Hg2+ ions in solution by fluorescence spectroscopic
technique.
44]
+
-1
8
24 cm
46]
I+Hg
I+Tl
To use the current compounds as possible sensor for
chromate, dichromate and permanganate anions, we took 1 mM
solution of these ions. In a typical experiment, 3 mg of the MOF
compounds was dispersed in 15 mL of water. 2.5 mL MOF
solution was taken in a in a cuvette and the anion solutions was
added in an incremental fashion. Similar to the metal ion
detection, the intensity of the luminescence at 500 nm (λex = 420
nm) was monitored (Figure 8). The fluorescence intensity
appeared to be affected only in the case of the addition of
chromate, dichromate and permanganate anions (Figure 8) and
we did not observed any significant changes in the fluorescent
-1
8
26 cm
-1
8
40 cm
I
5
00
600
700
800
900
1000
-1
Raman shift (cm )
−
−
intensity in the case of other common anions such as Cl , Br ,
−
−
−
2−
3−
2−
−
NO
3
, OAc , SCN , CO
3
, PO
4
, SO
4
, ClO
4
(Figure 9).
(
a)
The sensitivity of detection of the three ions was detected
employing the Stern-Volmer equation, which was similar to what
was employed during the detection of the metal ions (Figure S20
in the Supporting Information). From the Ksv values, we
determined the sensitivity of detection similar to the detection of
Tl3+ and Hg . The present compounds exhibited a good
detection of 69 ppb, 71 ppb, 303 ppb (for I) and 398 ppb, 153
-
1
8
35 cm
II + Hg
2+
-1
8
29 cm
II +Tl
II
−
2−
2−
ppb and 441 ppb (for II) for the (MnO
4
) , (Cr
2
O
7
)
4
and (CrO )
ions, respectively (Figure S21 and Table S6 in the Supporting
Information). Thus, the compounds are not only selective but
also sensitive for the detection of these ions in solution. The
-1
8
44 cm
quenching efficiency was calculated employing [(I
0 0
− I)/I ] × 100
(
%) equation, where I is the initial emission intensity and I is the
0
intensity after the addition of the anion solutions. The quenching
efficiency after 3rd cycle of measurement were 95.47 % (for
500
600
700
800
900
1000
-1
Raman shift (cm )
-), 96.75 % (for Cr
2-
2-
MnO
4
2
O
7
), 55.93 % (for CrO
-), 93.51 % (for Cr
-) (Pb-compound) (Figure S22 in the
4
4
) (Mn-
compound) and 73.79 % (for MnO
6.89
(for CrO 2
4
2 7
O
2-),
4
%
(
b)
Supporting Information). We also wanted to explore the
detection of these ions in the presence of the common ions
listed above. Our studies clearly indicated that the present
Figure 7. Figure shows the Raman spectra for the MOF compounds along
with Tl / Hg ions loaded MOF compounds: (a) Mn-compound (b) Pb-
compound. Please note the shift in the Raman peak (see text).
3+
2+
This article is protected by copyright. All rights reserved.

ChemPlusChem
10.1002/cplu.201700277
FULL PAPER
1
000
2-
1000
800
600
400
200
0
2
-
I + CrO
I + Cr O
4
2
7
0 µL
5 µL
0
5
µL
0 µL
(a)
(b)
1
1
2
3
4
5
6
7
8
9
1
1
1
0 µL
5 µL
0 µL
0 µL
0 µL
0 µL
0 µL
0 µL
0 µL
0 µL
00 µL
25 µL
50 µL
8
6
4
2
00
00
00
00
0
100 µL
1
2
2
3
3
4
50 µL
00 µL
50 µL
00 µL
50 µL
00 µL
450 µL
5
00 µL
400
450
500
550
600
650
700
400
450
500
550
600
650
700
Wavelength (nm)
Wavelength (nm)
1
000
-
700
I + MnO4
2-
II + CrO4
0
1
2
3
4
5
6
7
8
9
1
µL
0 µL
50 µL
(c)
(d)
0 µL
0 µL
0 µL
0 µL
0 µL
0 µL
0 µL
0 µL
0 µL
00 µL
6
00
500
00
300
100 µL
150 µL
200 µL
250 µL
300 µL
350 µL
400 µL
450 µL
500 µL
8
6
4
2
00
00
00
00
0
4
550 µL
2
1
00
00
0
4
00
450
500
550
600
650
700
400
00
600
450
500
550
600
650
700
Wavelength (nm)
Wavelength (nm)
7
6
5
4
3
2
1
00
7
2
-
-
0 µL
2
II + Cr O7
II + MnO4
0 µL
(
e)
1
2
3
0 µL
0 µL
0 µL
(f)
1
2
4
0 µL
0 µL
0 µL
00
00
00
00
00
00
0
40 µL
5
4
3
2
1
00
00
00
00
00
0
60 µL
00 µL
150 µL
5
7
1
1
0 µL
5 µL
1
00 µL
50 µL
2
2
3
3
00 µL
50 µL
00 µL
50 µL
200 µL
50 µL
2
4
00
450
500
550
600
650
700
400
450
500
550
600
650
700
Wavelength (nm)
Wavelength (nm)
4 2 7 4 4
Figure 8. Luminescence titrations plots between the MOF compounds: For Mn-compound (a) CrO O ; For Pb-compound (d) CrO
2−, (b) Cr 2−, (c) MnO − 2−, (e)
2− −
Cr O , (f) MnO .
2 7 4
This article is protected by copyright. All rights reserved.

ChemPlusChem
10.1002/cplu.201700277
FULL PAPER
(
a)
(b)
Figure 9. Comparison of the fluorescence quenching intensity among the different anion solutions (a) Mn-compound (I), (b) Pb-compound (II).
compounds exhibited good selectivity for the detection of these
highly oxidizing ions only and we did not observe any significant
interference from other ions (Figure S23 in the Supporting
Information). In addition, we also examined the possible
recyclability of these compounds for the detection of these ions
in solution. Thus, the present compounds can be employed for
the detection of these ions for upto three times (Figure S23 in
the Supporting Information). A PXRD study of these compounds
after this study did not reveal any significant changes in the
PXRD patterns, which suggests that the compounds are stable
other common anions examined as part of the study. From our
luminescence studies, we observed that the present compounds
exhibited a strong emission (π*-π transition) at 500 nm (λex
=
420 nm) (Figure S6 in the Supporting Information). This
emission falls in the blue-green region of the visible spectrum.
4 2 7 4
The anions, (CrO ) , (Cr O
)2− and (MnO )− are intensely
2
−
colored due to the LMCT effect. The absorbance spectra
exhibits maxima at 370 nm and 268 nm for the chromate, 354
nm and 260 nm for dichromate and 546 nm, 350 nm, 308 nm
and 230 nm for the permanganate ions in solution.[47] The
transition would generally, correspond to the transition from the
(
Figure S24 in the Supporting Information).
p
filled oxygen π orbitals to the empty manganese 3d orbitals.
There could be four ligand to metal transitions possible in a
tetrahedral coordination. Thus, in the present case, the observed
1
0
0
0
0
0
.0
.8
.6
.4
.2
.0
Mn-compound
Pb-compound
transitions correspond to
chromate, t -e (354nm), t -t
nm), t -t * (350 nm), t -e (308 nm), t
2 2
t
1
-e (370nm),
* (260 nm) for dichromate, t
-t * (230 nm) for the
t
1
-t
2
*
(268nm) for
2-
CrO4
-e (546
1
1
2
1
2
-
Cr O
2
7
1
2
2
-
MnO4
permanganate ions (Figure S25 in the Supporting Information). It
is likely that there could be significant overlap between the π*-π
emission band of the compounds with the absorption band of
these anions. This favorable interaction would be responsible for
the selectivity as well as the sensitivity towards these ions
(
Figure 10).
Conclusions
The synthesis, structure, and characterization of two new
luminescent MOFs based on 4,4′-(benzothiadiazole-4,7-diyl)
2
00
300
400
500
600
700
Wavelength (nm)
4 10 2 4 2 4 2
dibenzoic acid ligand [Mn (C20H N O S) (HCOO) (DEF) ] (I),
[
10 2 4
Pb(C20H N O
S)(DMF)] (II) has been accomplished. The
Figure 10. UV-vis spectra of the MOF compounds dispersed in water and the
chromate, dichromate and permanganate ion solutions.
luminescences of these MOFs were exploited as a probe for the
detection of highly toxic metal ions like thallium, mercury in ppb
level. The present compounds exhibit
a good degree of
selectivity towards Tl and Hg2+ ions, especially in the presence
of many other similar ions. The free S of the ligand would have
acted as a soft base and help in the detection of these soft acid
3+
We sought to investigate the possible reason for the
selectivity/sensitivity of the present compounds towards the
chromate, dichromate and permanganate ions compared to the
This article is protected by copyright. All rights reserved.

ChemPlusChem
10.1002/cplu.201700277
FULL PAPER
metal ions, which was also confirmed by Raman spectral studies.
In addition, highly oxidizing anions such as chromate,
dichromate and permanganate were also detected in ppb level
employing fluorimetry. The compounds retain their sensitivity
and selectivity for the detection of both the cations and anions at
least three cycles. Magnetic studies on the Mn-compound
suggest antiferromagnetic behavior. The temperature dependent
electrical conductivity studies indicate a semiconducting nature,
comparable to some well known compounds such as CdSe,
ZnTe, GaP etc.
2 2 2 2
hydroxide, hydrochloric acid, PbCl , MnCl .4H O, HgCl were acquired
from SDfine (India). All the chemicals were used without further
purification.
Synthesis. The ligand 4,4′-(benzothiadiazole-4,7-diyl) dibenzoic acid
was synthesized employing the reported procedure Scheme -1 (in the
Supporting Information).[48, 49]
4 10 2 4
Synthesis of [Mn (C20H N O S)
2
(HCOO)
4 2
(DEF) ].
A mixture of
MnCl .4H (79 mg, 0.398 mmol), 4,4′-(benzothiadiazole-4,7-diyl)
2
2
O
dibenzoic acid (50 mg, 0.133 mmol) and N,N’-diethylformamide (7 mL)
were taken in a 14 mL Teflon-lined autoclave and heated at 150ºC for 3
days. The resulting product contained yellow colored plate like crystals,
which were filtered, washed with N, N-diethylformamide and methanol
and dried in vacuum. Yield: 79.6 mg (44.3 %). Elemental analysis (%) for
Table 1. Crystal data and structure refinement parameters for I and II.
Structural
parameter
I
II
[Mn
4 10 2 4 2 4 2
(C20H N O S) (HCOO) (DEF) ] found (calculated): C 47.60 (48.01),
H 3.35 (3.43), N 6.34 (6.22), S 4.68 (4.75).
Empirical
formula
[Mn
4
(C20
H
10
N
2
O
4
S)
2
(HCO
10 2 4
[Pb(C20H N O S)(DMF)]
O)
1350.86
Monoclinic
P2 /c
4
(DEF)
2
]
Synthesis of Structure of [Pb(C20
74 mg, 0.266 mmol), 4,4′-(benzothiadiazole-4,7-diyl) dibenzoic acid (50
mg, 0.133 mmol), N, N-dimethylformamide (7 mL) and HClO (20 μL)
were taken in a 14 mL Teflon-lined autoclave and heated at 150ºC for 3
days. The resulting product contained yellow colored needle like crystals,
which were filtered, washed with N, N’-dimethylformamide and methanol
and dried in vacuum. Yield: 34.26 mg (39.35 %). Elemental analysis (%)
10 2 4
H N O S)(DMF)]. A mixture of PbCl
2
(
Formula weight
654.66
Monoclinic
P2 /n
4
Crystal system
Space group
a (Å)
1
1
38.150(5)
8.960(5)
16.245(5)
90
13.848(9)
4.377(3)
35.016(2)
90
10 2 4
for [Pb(C20H N O S)(DMF)] found (calculated): C 41.89 (42.19), H 2.28
(2.62), N 6.12 (6.42), S 4.71 (4.89).
b (Å)
c (Å)
Initial Characterizations: The ligand was characterized employing 1H-
NMR spectroscopy, UV-Vis spectroscopy and infrared spectroscopy. 1H-
α (°)
NMR data were collected using Bruker 400 MHz spectrometer. Chemical
shifts are reported in ppm using TMS as the internal reference (Figure
S34-S36 in the Supporting Information). UVVis spectra were recorded
at room temperature using Perkin Elmer Lambda 35 spectrophotometer
β (°)
96.465(5)
90
93.821(2)
90
γ (°)
V (Å3)
Z
5518(4)
4
2117.5(2)
4
(Figure S5 in the Supporting Information). Solid state photoluminescence
studies were carried out at room temperature using Perkin Elmer LS 55
luminescence spectrophotometer (Figure S6 in the Supporting
Information). IR spectra were recorded as KBr pellets using a FTIR
spectrometer (Perkin Elmer, model no: L125000P) (Figure S7, Table S4
in the Supporting Information). Powder Xray diffraction (XRD) patterns
were recorded in the 2θ range 550° using Cu Kα radiation (Philips
X’pert) (Figure S9 in the Supporting Information). The observed PXRD
patterns were found to be consistent with the PXRD patterns simulated
from the single crystal structure study, indicating the purity of the phase.
Elemental analyses (carbon, hydrogen, and nitrogen) were performed in
a Thermo Finnigan EA Flash 1112 Series. Thermogravimetric analysis
(TGA) (MetlerToledo) were carried out in oxygen atmosphere (flow rate
T/K
120
120
-
3
ρ (calc/gcm )
1.626
2.053
-
1
μ (mm )
1.051
8.109

(Mo Kα/Å)
0.71073
2.51 - 25.00
0.71073
θ range ( °)
2.95- 25.00
R indexes [ I >
R1 = 0.0577 wR2 =
0.1148
R1 = 0.0232 wR2 = 0.0445
2
 (I)]
=
40 mL/min) in the temperature range 30−800C (heating rate = 10C /
R indexes (all
data)
R1 = 0.0897 wR2 =
0.1320
R1 = 0.0341 wR2 =0.0469
min) (Figure S8 in the Supporting Information). Magnetic studies were
carried out in the temperature range of 2–300 K using a SQUID
magnetometer (Quantum Design, USA).
aR
aP)2 + bP]. P = [max (F
= Σ||F
| − |F
||/Σ|F
|; wR
= {Σ|w(F
2
− F
2)]/Σ [w(F
2
) ]} . w = 1/[ρ (F
2
1/2
2
)2
+
1
o
c
o
2
o
c
o
o
(
o
,O) + 2(F
c
)2]/3, where a = 0.0355 and b = 8.2024 for I
SingleCrystal Structure Determination. Suitable single crystals were
carefully selected under a polarizing microscope and mounted to a thin
fiber loop with the help of paratone oil. Single crystal data were collected
at 120 K on an Oxford Xcalibur (Mova) diffractometer equipped with an
EOS CCD detector. The Xray generator was operated at 50 kV and 0.8
and a = 0.0201 and b = 2.8968 for II.
Experimental Section
mA using Mo K
α
(λ= 0.71073 Å) radiation. The cell refinement and data
reduction were accomplished using CrysAlis RED.[ The structure was
50]
Materials. The chemicals, 4-(methoxycarbonyl) benzeneboronic acid,
Tetrakis(triphenylphosphine) palladium(0), Tl(NO .3H were
purchased from SigmaAldrich. 1,2-phenylenediamine, thionyl chlorid,
bromine, THF, CHCl CH Cl N,N-dimethylformamide, N,N’-
diethylformamide, 1,4-dioxane, potassium carbonate, potassium
solved by direct methods and refined using SHELX-2016/6 present in the
WinGX suit of programs (version 1.63.04a).[51] The hydrogen positions
were fixed in a geometrically ideal position and refined employing a riding
model. The final refinements included the atomic positions for all the
atoms, anisotropic thermal parameters for all the nonhydrogen atoms,
3
)
3
2
O
3
,
2
2
,
This article is protected by copyright. All rights reserved.

ChemPlusChem
10.1002/cplu.201700277
FULL PAPER
and isotropic thermal parameters for all the hydrogen atoms. The details
of the structure solution and final refinement parameters are given in
Table 1. The CCDC numbers for the compounds 1539918 (I) and
[27] S. Chakrabarti, S. Natarajan, Angew. Chem. Int. Ed. 2002, 41, 1224–
1226.
[28] M. SK, S. Biswas, Cryst. Eng. Comm. 2016, 18, 3104–3113.
[29] J. B. Goodenough, Magnetism and the Chemical Bond, Interscience
Publishers: Olney, Bucks, U.K., 1963, pp. 75–119.
1539919 (II). These data can be obtained free of charge from The
Cambridge Crystallographic Data Center (CCDC) via
www.ccdc.cam.ac.uk/data_request/cif.
[30] P. Mahata, D. Sen, S. Natarajan, Chem. Comm. 2008, 1278–1280.
[
[
[
31] T. C. Parker, D. G. Patel, K. Moudgil, S. Barlow, C. Risko, J. L. Bredas,
J. R. Reynoldsac, S. R. Marder, Mater. Horiz. 2015, 2, 22–36.
32] S. Paek, N. Cho, K. Song, M. J. Jun, J. K. Lee, J. Ko, J. Phys. Chem. C
Acknowledgements
2012, 116, 23205–23213.
33] P. Kubelka, F. Z. Munk, Tech. Phys. 1931, 12. 593–601.
The authors thank the Science and Engineering Research Board
SERB), Government of India, for the award of a J. C. Bose
National Fellowship. The Council of Scientific and Industrial
Research (CSIR), Government of India, is thanked for the award
of a research grant (S.N.) and a research fellowship (A.K.J.).
[34] C. Lincheneau, M. Amelia, M. Oszajca, A. Boccia, F. D'Orazi, M.
Madrigale, R. Zanoni, R. Mazzaro, L. Ortolani, V. Morandi, S. Silvi, K.
Szaciłowski, A. Credi, J. Mater. Chem. C 2014, 2, 2877–2886.
(
[
[
35] A. M. Smith, S. Nie, Acc. Chem. Res. 2010, 43, 190–200.
36] S. Assali, I. Zardo, S. Plissard, D. Kriegner, M. A. Verheijen, G. Bauer,
A. Meijerink, A. Belabbes, F. Bechstedt, J. E. M. Haverkort, E. P. A. M.
Bakkers, Nano Lett. 2013, 13, 1559–1563.
Keywords: Luminescent MOF • highly toxic metal ions • highly
oxidizing anions • sensing • dye adsorption/desorption
[37] S. Halder, J. Mondal, J. O. Castro, A. Frontera, P. Roy, Dalton Trans.
017, 46, 1943-1950.
38] Y. Rachuri, B. Parmar, K. K. Bisht, E. Suresh, Cryst. Growth Des. 2017,
7, 1363–1372.
2
[
1
[
[
1]
2]
X. Sun, Y. Wang, Y. Lei, Chem. Soc. Rev. 2015, 44, 8019−8061.
S. Giannoukos, B. Brkic, S. Taylor, A. Alan Marshall, G. F. Verbeck,
Chem. Rev. 2016, 116, 8146−8172.
[
[
39] T. L. Ho, Chem. Rev. 1975, 75, 1−20.
40] S. Wood, J. H. Kim, J. Wade, J. B. Park, D. H. Hwang, J. S. Kim, J.
Mater. Chem. C 2016, 4, 7966–7978.
[
3]
4]
Z. Liu, W. He, Z. Guo, Chem. Soc. Rev. 2013, 42, 1568−1600.
H. N. Kim, W. X. Ren, J. S. Kim, J. Yoon, Chem. Soc. Rev. 2012, 41,
[
[
41] C. S. Cao, H. C. Hu, H. Xu, W. Z. Qiao, B. Zhao, Cryst. Eng. Comm.
[
2016, 00, 1–3.
3210–3244.
42] B. Ding, S. X. Liu, Y. Cheng, C. Guo, X. X, J. H. Guo,Y. Y. Liu, Y. Li,
Inorg. Chem. 2016, 55, 4391−4402.
[
[
[
5]
6]
7]
G. Aragay, J. Pons, A. Merkoci, Chem. Rev. 2011, 111, 3433–3458.
J. B. DeCoste, G. W. Peterson, Chem. Rev. 2014, 114, 5695−5727.
W. Yantasee, Y. Lin, K. Hongsirikarn, G. E. Fryxell, R. Addleman, C.
Timchalk, Environmental Health Perspectives 2007, 115, 1683–1690.
W. Diewald, K. Kalcher, C. Neuhold, I. Svancara, X. Cai, Analyst 1994,
[
[
43] J. Crossgrove, W. Zheng, NMR Biomed. 2004. 17. 544–553.
44] Y. Xie, S. Holmgren, D. M. K. Andrews, M. S. Wolfe, Environmental
Health Perspectives. 2017, 125, 181–188.
[
[
[
8]
[
[
[
45] World Health Organization, Guidelines for Drinking Water Quality,
World Health Organization, Geneva, Switzerland, 2011, pp. 1–564.
46] Y. S. Hedberg, C. Liden, I. O. Wallinder, Contact Dermatitis 2014, 72,
1
19, 299–304.
C. S. Pedrefio, J. A. Ortufio, M. C. Torrecillas, Analyst 1986, 111,
359–1361.
9]
1
206–215.
10] F. S. Shan, J. P. Lai, H. Sun, P. Zhang, C. Luo, Y. H. He, H. R. Feng,
RSC Adv. 2016, 6, 66215–66223.
47] J. E. Huheey, E. A. Keiter, R. L. Keiter, Inorganic Chemistry Principles
of Structure and Reactivity, Harper Collins College Publishers, Fourth
Edition, 1993, pp. 456–458.
[
11] X. Y. Xu, B. Yan, J. Mater. Chem. C 2016, 4, 1543–1549.
12] L. Yang, X. Li, C. Qin, K. Z. Shao, Z. M. Su, Cryst. Eng. Comm. 2016,
[
[
[
[
[
48] F. S. Mancilha, B. A. D. Neto, A. S. Lopes, P. F. M. Jr, F. H. Quina, R.
S. Gonçalves, J. Dupont, Eur. J. Org. Chem. 2006, 4924–4933.
49] N. Wei, Y. R. Zhang, Z. B. Han, Cryst. Eng. Comm. 2013, 15, 8883–
1
8, 4765–4771.
13] A. Corma, H. Garcıa, F. X. L. Xamena, Chem. Rev. 2010, 110, 4606–
655.
14] R. B. Getman, Y. S. Bae, C. E. Wilmer, R. Q. Snurr, Chem. Rev. 2012,
12, 703–723.
[
[
[
4
8886.
50] CrysAlis CCD, CrysAlis PRO RED, version 1.171.33.34d, Oxford
Diffraction Ltd., Abingdon, Boxfordshire, England, 2009.
1
15] L. E. Kreno, K. Leong, O. K. Farha, M. Allendorf, R. P. V. Duyne, J. T.
Hupp, Chem. Rev. 2012, 112, 1105–1125.
51] Sheldrick, G. M. SHELXS-97, Program for Crystal Structure Solution
and Refinement, University of Gꢀttingen, Gꢀttingen, Germany, 1997.
[
16] P. Kumar, A. Deep, K. H. Kim, Analytical Chemistry 2015, 73, 39–53.
17] S. Madhu, D. K. Sharma, S. K. Basu,S. Jadhav, S. Chowdhury,M.
Ravikanth, Inorg. Chem. 2013, 52, 11136−11145.
[
[
18] D. Banerjee, Z. Hu, J. Li, Dalton Trans. 2014, 43, 10668–10685.
19] D. T. McQuade, A. E. Pullen, T. M. Swager, Chem. Rev. 2000, 100,
[
2537–2574.
[
20] Y. Yang, K. Shen, J. Z. Lin, Y. Zhou, Q. Y. Liu, C. Hang, H. N.
Abdelhamid, Z. G. Zhang, H. Chen, RSC Adv. 2016, 6, 45475–45481.
21] R. G. Pearson, J. Am. Chem. Soc. 1963, 85, 3533–3539.
[
[
22] P. M. Angus, D. P. Fairlie, W. G. Jackson, Inorg. Chem. 1993, 32, 450–
459.
[
[
23] M. R. S. J. Foreman, T. Gelbrich, M. B. Hursthouse, M. J. Plater,
Inorganic Chemistry Communications 2000, 3, 234–238.
24] L. Zhang, Z. J. Li, Q. P. Lin, Y. Y. Qin, J. Zhang, P. X. Yin, J. K.
Cheng,Y. G. Yao, Inorg. Chem. 2009, 48, 6517–6525.
[
[
25] I. D. Brown, D. Altermatt, Acta Crystallogr. 1985, B41, 244–247.
26] S. Natarajan, S. Mandal, Angew. Chem. Int. Ed. 2008, 47, 4798–4828.
This article is protected by copyright. All rights reserved.

ChemPlusChem
10.1002/cplu.201700277
FULL PAPER
FULL PAPER
New luminescent MOFs were shown
to exhibit considerable selectivity
Ajay Kumar Jana, and Srinivasan
Natarajan*
3+
2+
towards toxic metal ions (Tl , Hg ),
anions such as chromate, dichromate
and permanganate ions. Figure shows
the fluorescence quenching response
Page No. – Page No.
towards Tl3+ and (Cr
solution.
O
7
)2- ions in
2
Fluorescent MOFs for selective
3+
2+
sensing of toxic cations (Tl , Hg ),
2
−
4
highly oxidizing anions [(CrO ) ,
2
−
−
(
2 7 4
Cr O ) , (MnO ) ]
This article is protected by copyright. All rights reserved.