Luminescent Zn(II) Coordination Polymers for Highly Selective Sensing of Cr(III) and Cr(VI) in Water

Article abstract of DOI:10.1021/acs.inorgchem.7b00311

Three photoluminescent zinc coordination polymers (CPs), {[Zn₂(tpeb)₂(2,5-tdc)(2,5-Htdc)₂]·2H₂O}_n (1), {[Zn₂(tpeb)₂(1,4-ndc)(1,4-Hndc)₂]·2.6H₂O}_n (2), and {[Zn₂(tpeb)₂(2,3-ndc)₂]·H₂O}_n (3) (tpeb = 1,3,5-tri-4-pyridyl-1,2-ethenylbenzene, 2,5-tdc = 2,5-thiophenedicarboxylic acid, 1,4-ndc = 1,4-naphthalenedicarboxylic acid, and 2,3-ndc = 2,3-naphthalenedicarboxylic acid) were prepared from reactions of Zn(NO₃)₂·6H₂O with tpeb and 2,5-H₂tdc, 1,4-H₂ndc, or 2,3-H₂ndc under solvothermal conditions. Compound 1 has a two-dimensional (2D) grid-like network formed from bridging 1D [Zn(tpeb)]_n chains via 2,5-tdc dianions. 2 and 3 possess similar one-dimensional (1D) double-chain structures derived from bridging the [Zn(tpeb)]_n chains via pairs of 1,4-ndc or 2,3-ndc ligands. The solid-state, visible emission by 1-3 was quenched by Cr³⁺, CrO₄^2-, and Cr₂O₇^2- ions in water with detection limits by the most responsive complex 3 of 0.88 ppb for Cr³⁺ and 2.623 ppb for Cr₂O₇^2- (pH = 3) or 1.734 ppb for CrO₄^2- (pH = 12). These values are well below the permissible limits set by the USEPA and European Union and the lowest so far reported for any bi/trifunctional CPs sensors. The mechanism of Cr³⁺ luminescence quenching involves irreversible coordination to free pyridyl sites in the CP framework, while the Cr⁶⁺ quenching involves reversible overlap of the absorption bands of the analytes with those of the excitation and/or emission bands for 3.

Full text of DOI:10.1021/acs.inorgchem.7b00311

Article
pubs.acs.org/IC
Luminescent Zn(II) Coordination Polymers for Highly Selective
Sensing of Cr(III) and Cr(VI) in Water
Tian-Yi Gu,†,‡ Ming Dai,†,∥ David James Young,§ Zhi-Gang Ren,*,† and Jian-Ping Lang*,†,‡
†College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou 215123, People’s Republic of
China
‡State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences,
Shanghai 200032, People’s Republic of China
∥Suzhou Clean Environment Institute, Jiangsu Sujing Group Company, Limited, Suzhou 215122, People’s Republic of China
§Faculty of Science, Health, Education and Engineering, University of the Sunshine Coast, Maroochydore DC, Queensland 4558,
Australia
S
* Supporting Information
ABSTRACT: Three photoluminescent zinc coordination polymers
(CPs), {[Zn2 (tpeb)2 (2,5-tdc)(2,5-Htdc)2 ]·2H2 O}n (1),
{[Zn2 (tpeb)2 (1,4-ndc)(1,4-Hndc)2 ]·2.6H2 O}n (2), and
{[Zn2(tpeb)2(2,3-ndc)2]·H2O}n (3) (tpeb = 1,3,5-tri-4-pyridyl-1,2-
ethenylbenzene, 2,5-tdc = 2,5-thiophenedicarboxylic acid, 1,4-ndc =
1,4-naphthalenedicarboxylic acid, and 2,3-ndc = 2,3-naphthalenedicar-
boxylic acid) were prepared from reactions of Zn(NO3)2·6H2O with
tpeb and 2,5-H2tdc, 1,4-H2ndc, or 2,3-H2ndc under solvothermal
conditions. Compound 1 has a two-dimensional (2D) grid-like network
formed from bridging 1D [Zn(tpeb)]n chains via 2,5-tdc dianions. 2 and
3 possess similar one-dimensional (1D) double-chain structures derived
from bridging the [Zn(tpeb)]n chains via pairs of 1,4-ndc or 2,3-ndc
ligands. The solid-state, visible emission by 1−3 was quenched by Cr3+,
CrO42−, and Cr2O7 ions in water with detection limits by the most
2−
2−
2−
responsive complex 3 of 0.88 ppb for Cr3+ and 2.623 ppb for Cr2O7 (pH = 3) or 1.734 ppb for CrO4 (pH = 12). These
values are well below the permissible limits set by the USEPA and European Union and the lowest so far reported for any bi/
trifunctional CPs sensors. The mechanism of Cr3+ luminescence quenching involves irreversible coordination to free pyridyl sites
in the CP framework, while the Cr6+ quenching involves reversible overlap of the absorption bands of the analytes with those of
the excitation and/or emission bands for 3.
applications, and low cost.10 Many luminescent materials,
INTRODUCTION
■
including glutathione-capped CdTe quantum dots,11 nano-
particles,12 carbon dots,13 and some organic molecules,14 have
been developed for the detection of Cr(III) and Cr(VI). Much,
however, remains to be done, particularly with respect to
sensitivity.15
Chromium is widely used in industry1 but is a potentially
persistent, bioaccumulating, and highly toxic pollutant.
Carcinogenic Cr(VI) can induce DNA damage at trace or
even ultratrace levels,2−4 while Cr(III) is an essential trace
element for human health but is detrimental at high
concentrations.5 Chromium waste is generated from burning
coal, the operation of cooling towers, electroplating, oxidative
dyeing, tanning, and sanitary landfills6 and from the use of
corrosion inhibitors in water pipes.7 Many methods have been
developed for the detection of Cr(III and VI) ions, including
atomic absorption spectrometry (AAS), inductively coupled
plasma optical emission spectroscopy (ICP-OES), ion
chromatography (IC), and electrochemical detection. Mobile,
low-cost detection methods, however, would be valuable for
fieldwork and particularly in developing countries8 but
necessarily requires high sensitivity in a variety of matrices.9
Chemiluminescent detection is attractive in this respect due to
its potential for simplicity of operation, a broad range of
Coordination polymers (CPs) have been developed for the
chemical sensing of metal ions and other pollutants.16 A few
luminescent CPs have been reported for the detection of
Cr(III) or Cr(VI).17−21 The mechanism of the detection for
Cr(VI) is related to relatively slow ion exchange17 or
intermolecular energy transfer.21c,f−h In the case of Cr(III),
responsiveness depends on weak interactions between the Cr3+
cation and the free coordination sites of the CP ligands.22 To
our knowledge, there are only two reports of CPs,
{[Eu0.3Tb0.7(HL)(H2O)3]·H2O}n (L = 5,5′-(1H-2,3,5-triazole-
Received: February 3, 2017
© XXXX American Chemical Society
A
DOI: 10.1021/acs.inorgchem.7b00311
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
Scheme 1. Schematic Illustration of the Synthetic Process of Compounds 1−3
1,4-diyl)diisophthalic acid)18 and {[Zn2(TPOM)(NH2-
BDC)2]·4H2O}n (TPOM = tetrakis(4-pyridyloxymethylene)-
methane, NH2-BDC = 2-aminoterephthalic acid)20 with
potential as bifunctional sensors for detecting Cr3+ and
ing in response to both Cr(III) and Cr(VI) ions at ppb levels
for the latter in water. Described below are the syntheses of 1−
3, their structural characterization, and their excellent
luminescent sensing performance of Cr3+, CrO42−, and
2−
CrO42−/Cr2O7 simultaneously. Again, low sensitivity18/
2−
Cr2O7 ions in water.
selectivity19 and the necessity for organic solvents20 could
limit the development of this technology.
We have a long-standing interest in the use of CPs for
EXPERIMENTAL SECTION
■
General Procedures. All reagents and chemicals were obtained
directly from commercial sources and used without further
purification. The ligand tpeb was prepared according to a literature
detecting or degrading environmental pollutants such as
+
Hg(II), NH4 /NH3, organic dyes, and nitroaromatics in
method.23 The H NMR spectrum of tpeb was recorded at ambient
1
water.16c−g Zinc(II) coordination polymer [Zn(ppvppa)(1,4-
ndc)]n (ppvppa = dipyridin-2-yl-[4-(2-pyridin-4-yl-vinyl)-
phenyl]amine) was developed by some of us for the fluorescent
sensing of Hg2+ or CH3HgI with high selectivity and sensitivity.
In this example, the dipyridinylamine groups of the ppvppa
ligand acted as an ionophoric receptor for Hg2+ or MeHg+
ions.16c The related [Cd(ppvppa)(1,4-ndc)]n can detect
nitroaromatic compounds by making use of energy transfer
between the analytes and the complex, resulting in fluorescence
quenching.16d These results encouraged us to prepare some
new fluorescent CP materials designed to probe Cr3+ and/or
temperature in DMSO-d6 on a Varian UNITY plus-400 spectrometer
with chemical shifts referenced to the solvent signal. Elemental
analyses for C, H, and N were performed on a Carlo-Erba CHNO-S
microanalyzer. Inductively coupled plasma spectra (ICP) were
obtained on a Varian 710-ESICP optical emission spectrometer.
Infrared spectra (400−4000 cm−1) were obtained on a Nicolet iS-10
spectrometer with KBr disks. Thermogravimetric analyses (TGA)
were obtained on a TA SDT-600 analyzer (heating rate of 5 °C/min).
Powder X-ray diffraction (PXRD) measurements were carried out on a
PANalytical X’PertPRO MPD system (PW3040/60). UV−vis
absorption spectra were obtained on a Varian Cary-50 spectropho-
tometer. Photoluminescence spectra and quantum yields were
obtained on a HORIBA PTI QuantaMaster40 Spectrofluorometer.
X-ray photoelectron spectroscopy (XPS) measurements were recorded
on a Thermo-Fisher Scientific ESCALAB 250Xi X-ray photoelectron
spectrometer (with Al Kα X-ray radiation as the X-ray source for
excitation, whose binding energies were referenced to C 1s at 284.7 eV
from hydrocarbon to compensate charging effects).
2−
CrO42−/Cr2O7 ions in water. Tridentate π-conjugated ligand
1,3,5-tri-4-pyridyl-1,2-ethenylbenzene (tpeb) (Scheme 1) was
reacted with Zn(NO3)2 together with a group of dicarboxylic
acids under solvothermal conditions, generating three new CPs
{[Zn2 (tpeb)2 (2,5-tdc)(2,5-Htdc)2 ]·2H2 O}n (1),
{[Zn2(tpeb)2(1,4-ndc)(1,4-Hndc)2]·2.6H2O}n (2), and
{[Zn2(tpeb)2(2,3-ndc)2]·H2O}n (3) (2,5-H2tdc = 2,5-thiophe-
nedicarboxylic acid, 1,4-H2ndc = 1,4-naphthalenedicarboxylic
acid, and 2,3-H2ndc = 2,3-naphthalenedicarboxylic acid). These
metal complexes exhibited highly selective fluorescent quench-
Syntheses of 1−3. A mixture of Zn(NO3)2·6H2O (29.7 mg, 0.1
mmol), tpeb (19.4 mg, 0.05 mmol), dicarboxylic acids (0.05 mmol,
2,5-H2tdc, 8.6 mg for 1, 1,4-H2ndc, 10.8 mg for 2, and 2,3-H2ndc, 10.8
mg for 3), 2.4 mL of H2O, and 0.6 mL of MeCN was sealed in a 10
mL glass tube and allowed to react at 150 °C for 24 h. After cooling to
B
DOI: 10.1021/acs.inorgchem.7b00311
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
Table 1. Crystal Data and Structure Refinement Parameters for 1−3
1
2
3
empirical formula
fw
C72H54N6O14S3Zn2
1454.18
C45H35.2N3O8.6Zn
820.91
C78H56N6O9Zn2
1352.07
cryst syst
space group
a/Å
triclinic
monoclinic
C2/c
triclinic
P1
P1
̅
̅
9.4510(5)
20.0108(7)
20.4706(6)
118.027(4)
91.181(4)
103.093(4)
3292.0(2)
1.4617
29.287(3)
16.6983(14)
16.7466(15)
11.780(6)
11.799(5)
24.110(11)
102.896(11)
99.104(12)
102.543(12)
3113(3)
1.442
b/Å
c/Å
α/deg
β/deg
101.511(10)
γ/deg
V/Å3
ρcalc/g/cm3
8025.1(13)
1.281
Z
2
8
2
μ/mm−1
F(000)
0.896
0.663
0.839
1496.0
3192.0
0.0976
0.3172
1.041
1396.0
a
R1
0.0728
0.1141
b
wR2
0.2099
0.3261
c
GOF
1.057
1.180
a
b
c
2
R1= Σ∥F0| − |Fc∥/Σ|F0|. wR2= {Σw(F02 − Fc2)2/Σw(F0 )2}1/2. GOF = {Σw((F02 − Fc2)2)/(n − p)}1/2, where n = number of reflections and p =
total number of parameters refined.
ambient temperature at a rate of 7 °C h−1, crystals of each compound
were obtained (1, dark yellow prisms; 2, yellow blocks; 3, yellow
cubes). These crystals were then washed sequentially with water,
EtOH, and Et2O and dried in air. Yield for 1: 32.7 mg (45% based on
Zn). Anal. Calcd for C72H54N6O14S3Zn2: C, 59.47; H, 3.74; N, 5.78.
Found: C, 60.67; H, 3.61; N, 5.75. IR (KBr disk): 3052 (m), 1782
(m), 1634 (s), 1607 (s), 1529 (s), 1419 (s), 1330 (m), 1202 (s), 1025
(m), 969 (s), 857 (m), 819 (m), 769 (s), 688 (s), 537 (m) cm−1. Yield
for 2: 30.28 mg (39% based on Zn). Anal. Calcd for C45H35.2N3O8.6Zn:
C, 65.83; H, 4.32; N, 5.12. Found: C, 66.32; H, 4.91; N, 5.86. IR (KBr
disk): 3009 (m), 1756 (m), 1610 (s), 1509 (s), 1421 (s), 1384 (s),
1281 (m), 1181 (m), 1064 (s), 1002 (m), 868 (m), 822 (s), 532 (s).
Yield for 3: 43 mg (64% based on Zn). Anal. Calcd for
C78H56N6O9Zn2: C, 69.29; H, 4.17; N, 6.22. Found: C, 69.30; H,
4.23; N, 6.32. IR (KBr disk): 3050 (m), 1750 (m), 1611 (s), 1502 (s),
1443 (m), 1367 (s), 1204 (s), 1138 (s), 1068 (s), 1026 (s), 966 (m),
905 (s), 846 (s), 798 (m), 739 (s), 668 (m), 536 (s).
X-ray Structure Determination. Single crystals of 1−3 suitable
for X-ray analysis were obtained directly from the above procedures.
Data were collected on an Agilent Technologies Gemini A Ultra CCD
(1 and 2) or a Bruker APEX-II CCD diffractometer (3) using
graphite-monochromated Mo Kα (λ = 0.71073 Å). The single crystals
were mounted on glass fibers at 223 (1) and 298 K (2 and 3).
Reflection data were integrated, and unit cell parameters were
determined using all observed reflections with the program
CrysAlisPro, Agilent Technologies (Version 1.171.36.32, 2013), for 1
and 2 and APEX2 v2012.4-3 (Bruker, AXS) for 3. Empirical
absorption correction was applied using the program SADABS.24−26
The reflection data were also corrected for Lorentz and polarization
effects.
The crystal structures of 1−3 were solved by direct methods and
refined on F2 by full-matrix least-squares methods with the SHELXL-
2013 program.27a For 2, the solvent-accessible void occupied a volume
of 245 Å3 per unit cell (3% of the total cell volume calculted by the
PLATON program27b). As the disorder model did not give satisfactory
results, it was further treated with PLATON/SQUEEZE to find 26
electrons, which corresponded to approximately 2.6 water molecules
per chemical formula. One 4-pyridyl-1,2-ethenyl group of tpeb is
disordered over two sites with an occupancy factor of 0.6/0.4 for N1−
C1−C7 and N1A−C1A−C7A, while a 1,4-ndc molecule (C40−C47−
O5−O6) is disordered over two positions by rotating about the center
of C41−C41A with an equal occupancy factor. All non-H atoms were
refined anisotropically except for those of the disordered 4-pyridyl-1,2-
ethenyl group in 2. The H atoms of the water solvent molecules in 1
and 3 were first located from the Fourier maps, and their O−H bond
lengths were fixed to 0.83 Å. Two H atoms at the symmetric C42A
and C47A were not located. All other H atoms were placed in the
geometrically idealized positions and constrained to ride on their
parent atoms. Some very weak reflections or those blocked by the
beam stop were not included in refinements. Important crystal data
and refinement parameters for 1−3 are given in Tables 1 and S1.
2−
Photoluminescence Sensing of Cr3+, CrO42−, and Cr2O7
Ions. Uniform suspensions of compounds 1−3 were prepared by
grinding the crystalline solid (3 mg) and suspending the powder in
deionized water (3 mL) with ultrasound mixing for 1 h. Aqueous
−
solutions (3 mol/L, 1 μL) of NanX (X = F−, Cl−, Br−, I−, NO3 ,
−
−
ClO4 , IO3 , CO32−, SO42−, P2O74−, CrO42−, Cr2O72−, n = 1, 2, 4) or
M(NO3)n (Mn+ = Na+, K+, Ag+, Mg2+, Cd2+, Cu2+, Mn2+, Pb2+, and
Cr3+, n = 1, 2, 3) were injected into the suspensions by microsyringe
and uniformly mixed at room temperature. The luminescence
intensities of these suspensions were then measured on a
spectrofluorometer.
RESULTS AND DISCUSSION
■
Synthetic, Spectral, and Thermal Aspects. Solvothermal
reactions of Zn(NO3)2·6H2O, tpeb, and dicarboxylic acids (2,5-
H2tdc for 1, 1,4-H2ndc for 2, and 2,3-H2ndc for 3) with a molar
ratio of 2:1:1 in H2O/MeCN (v/v = 4/1) at 150 °C for 24 h
followed by a standard workup produced crystals of 1−3 in
reasonable yields (45% for 1, 39% for 2, and 64% for 3).
Compounds 1−3 were the only products regardless of the
molar ratios of the three components. The products remained
the same when the pH of the reaction systems was adjusted
within a wide range of 3−12. Likewise, different temperatures
(180 and 100 °C) in a variety of solvent systems (H2O/MeOH,
H2O/EtOH, and H2O/DMF) did not produce other
identifiable products.
Compounds 1−3 are stable in air and moisture and insoluble
in common organic solvents such as DMF, EtOH, MeOH,
DMA, DMSO, and CHCl3. Their elemental analyses were
consistent with their chemical formulas. PXRD patterns of the
bulk samples correlated well with simulated patterns generated
from the single-crystal X-ray diffraction data (Figure S1). A
strong band at 1607−1623 cm−1 was observed in the IR spectra
C
DOI: 10.1021/acs.inorgchem.7b00311
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
of all three compounds corresponding to the coordinated
carboxyl groups.
Thermogravimetric analyses of 1−3 revealed that they were
stable up to 301 (1), 368 (2), and 336 °C (3), respectively
(Figure S2). The two weight losses of 2.27% (33−100 °C) and
89.60% (323−530 °C) for 1 correspond to the loss of two
solvated water molecules (calcd 2.48%) and all organic species
(calcd 89.23%), respectively. The weight loss of 89.57% (345−
495 °C) for 2 is attributed to the loss of all tpeb and 1,4-ndc
ligands (calcd 90.95%),while the three stepwise weight losses of
1.97% (34−89 °C), 33.76% (358−409 °C), and 57.29% (409−
511 °C) for 3 represent the elimination of the solvated water
molecule (calcd 1.35%), 2,3-ndc (calcd 32.08%), and tpeb
(calcd 58.17%), respectively. The residue species were assumed
to be Zn (8.13% for 1, calcd 8.98%) and ZnO (11.02% for 2,
calcd 10.51%; 12.18% for 3, calcd 12.14%).
Crystal Structure of 1. Compound 1 crystallizes in the
triclinic space group P1, and its asymmetric unit contains one
̅
independent [Zn2(tpeb)2(2,5-tdc)(2,5-Htdc)2] unit and two
water solvent molecules. Each Zn1 is tetrahedrally coordinated
by two O atoms from two 2,5-tdc ligands and two N atoms
from two separate tpeb ligands, while each Zn2 adopts a
distorted tetragonal pyramid geometry which is associated with
one O atom from a 2,5-tdc ligand, two O atoms from another
2,5-tdc ligand, and two N atoms from two tpeb ligands (Figure
1a). The average Zn1−N and Zn1−O bond lengths of
2.059(50) and 1.978(47) Å (Table S1) are comparable to
those found in {[Zn2(H2O)(1,4-ndc)2(tpcb)]}n (2.046(5) and
1.952(4) Å, respectively, tpcb = tetrakis(4-pyridyl)-
cyclobutane).16g The mean Zn2−N and Zn2−O bond lengths
(2.080(38) and 2.157(50) Å) (Table S1) resemble those found
in {[Zn(1,4-ndc)(tpcb)0.5]}n (2.118(3) and 2.186(3) Å).16g In
each tpeb ligand, one pyridyl group (N3−C23−C27 and N5−
C43−C47) is left uncoordinated. The other two pyridyl groups
bridge one four-connected zinc (Zn1) and one five-connected
zinc (Zn2), thus producing a 1D [Zn(tpeb)]n chain extending
along the a axis (Figure 1b). Such 1D chains are interconnected
by the bridging 2,5-tdc dianions to give a 2D grid-like network
along the ac plane (Figure 1c), whereas one −COOH group of
each terminal coordinated 2,5-Htdc anions stretches above and
below the planes.
Figure 1. (a) View of the coordination environments of Zn1 and Zn2
in 1 with a labeling scheme. Symmetry codes: (A) x − 1, y, z − 1; (B)
x + 1, y, z − 1. (b) View of a portion of the 1D [Zn(tpeb)]n chain
extending along the a axis. (c) View of the 2D network extending
along the ac plane. Each cyan tetrahedron represents one Zn atom. All
H atoms and water solvent molecules have been omitted for clarity.
Crystal Structures of 2 and 3. Compound 2 crystallizes in
monoclinic space group C2/c, while 3 crystallizes in triclinic
space group P1. The asymmetric unit of 2 consists of 0.5
̅
[Zn2(tpeb)2(1,4-ndc)(1,4-Hndc)2] unit and 1.3 water mole-
cules, while for 3, its asymmetric unit contains one
[Zn2(tpeb)2(2,3-ndc)2] unit and one lattice water molecule.
All central Zn atoms in 2 and 3 show a tetrahedral coordination
mode (Figures 2a and 3a). Each Zn center is associated with
two N atoms from two tpeb ligands and two O atoms from two
carboxylate ligands (either 1,4-ndc or 2,3-ndc). The mean Zn−
N bond lengths (2.020(56) (2) and 2.064(30) Å (3)) (Table
S1) are similar to those of the corresponding ones in 1, while
the mean Zn−O bond lengths (1.955(52) (2) and 1.946(8) Å
(3)) are shorter than those found in 1. In each tpeb ligand, one
pyridyl group (N3−C23−C27 in 2; N2−C16−C20 and N6−
C50−C54 in 3) remains uncoordinated. The other two pyridyl
groups bridge the neighboring Zn atoms to produce a 1D
[Zn(tpeb)]n chain extending along the b axis (Figures 2b and
3b). In 2, the [Zn(tpeb)]n chains are interconnected by the
bridging 1,4-ndc dianions to give a 1D double-chain structure,
while the terminal coordinated 1,4-Hndc ligands stretch above
and below these chains, leaving a pair of free −COOH groups
(Figure 2b), while in 3 the [Zn(tpeb)]n chains are bridged by
pairs of 2,3-ndc ligands, thereby forming a 1D double chain
extending along the b axis (Figure 3b).
Photoluminescent Properties. Upon excitation at 380
(tpeb), 400 (1), 370 (2), and 378 (3) nm at room temperature,
these compounds exhibited solid-state photoluminescence with
emission maxima at 416 (tpeb), 468 (1), 452 (2), and 474 (3)
nm (Figure 4). The highly π-delocalized planar28 tpeb is
emissive with a quantum yield (QY) of 4.70%. The emissions of
1−3 are all red shifted relative to free ligand (Figure 4) with
higher quantum yields (QY = 6.87% (1), 7.83% (2), and
12.04% (3)). We assign this red shift to ligand-to-ligand charge
transfer (LLCT)29 between the dicarboxylate and the tpeb
ligand that are constrained by coordination to Zn2+ with a
relatively short distance between adjacent tpeb ligands,
improving the weak interactions between them and thus
enhancing the emission.30
D
DOI: 10.1021/acs.inorgchem.7b00311
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
Figure 4. Solid-state emission spectra of tpeb (black), 1 (red), 2
(green), and 3 (blue).
Photoluminescence Sensing of Cr3+, CrO42−, and
2−
Cr2O7 Ions. The PXRD patterns of 1−3 after treating
them in acidic and basic aqueous solutions (Figure S3)
demonstrated that these three compounds possessed high
water stability in a wide pH range from 3 to 12. This
phenomenon suggested the possibility of directly sensing Cr3+,
Figure 2. (a) View of the coordination environment of Zn1 in 2 with a
labeling scheme. Symmetry codes: (A) x, y − 1, z; (B) −x + 1, y, −z +
1.5. (b) View of a section of the 1D double chain in 2 extending along
the b axis. Each cyan tetrahedron represents one Zn atom. All
disordered motifs and H atoms have been omitted for clarity.
2−
Cr2O72−, and CrO4 in water. Zn−CPs 1−3 were suspended
in water, and changes to their emission spectra were observed
on exposure to different cations (1 × 10−3 mol/L, Na+, K+, Ag+,
Mg2+, Cd2+, Cu2+, Mn2+, Pb2+, and Cr3+) or anions (1 × 10−3
mol/L, F−, Cl−, Br−, I−, NO3 , ClO4 , IO3 , CO32−, SO4
,
−
−
−
2−
P2O74−, CrO42−, Cr2O72−). The luminescence curves of these
mixtures all showed the characteristic emission peaks of 1−3
(Figure S4). The sensing effects were explored by monitoring
their intensities at emission λmax. Among the various cations
tested (Figure 5a), only Cr3+ caused a significant emission
decrease (1 and 2) and nearly total quenching (3). Similarly, in
anion solutions, 1−3 showed decreases in photoluminescence
2−
2−
in the presence of Cr2O7 and CrO4 to varying degrees
(Figure 5b). The fluorescent quenching of 1−3 is similar to
that reported for other fluorescent CPs.20 Since compounds 1−
3 can respond to chromium ions of different valence (III and
VI) at the same time, there is a potential for these compounds
to be used as trifunctional chemical sensors for the detection of
the common chromium pollutants Cr3+, Cr2O72−, and CrO4
2−
in industrial wastewater.
Compound 3 displayed the most significant quenching in the
presence of both Cr(III) and Cr(VI) (Figure 5) and thus was
chosen as a representative sample for further investigation of
selectivity and sensitivity. The selectivity of 3 was examined by
measuring the luminescent intensities of its suspensions in the
mixture of the above-mentioned cations with and without Cr3+
or anions with and without Cr2O7 and CrO4 (1 × 10−3
mol/L for each ion). As observed in Figure 6, the intensities
were less influenced by other cations or anions but evidently
weakened with addition of Cr3+, Cr2O72−, and CrO42−, which
demonstrated the good selectivity of 3 for all three states of
chromium relative to other common cations and anions found
in industrial wastewater.
2−
2−
2−
The detection limits of 3 toward Cr3+, CrO42−, and Cr2O7
were calculated by the fluorescence titration. A suspension of 3
was titrated with Cr(NO3)3 solution and demonstrated
outstanding sensing behavior toward Cr3+ with 86.7%
quenching of the initial fluorescence at 52 ppm (1 × 10−3
mol/L) Cr3+. The dose−response graph fitted the relationship
Figure 3. (a) View of the coordination environments of Zn1 and Zn2
in 3 with a labeling scheme. Symmetry code: (A) x − 1, y + 1, z. (b)
View of a segment of the 1D double chain in 3 extending along the b
axis. Each cyan tetrahedron represents one Zn atom. All H atoms and
the water solvent molecule have been omitted for clarity.
E
DOI: 10.1021/acs.inorgchem.7b00311
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
Figure 5. Luminescence intensities of compounds 1 (at 468 nm), 2 (at 452 nm), and 3 (at 474 nm) treated with different (a) cations (1 × 10−3 mol/
L) and (b) anions in aqueous phase at ambient temperature.
Figure 6. Emission spectra of 3 in the (a) mixture of cations (Na+, K+, Ag+, Mg2+, Cd2+, Cu2+, Mn2+, Pb2+, 1 × 10−3 mol/L for each) with/without
−
−
−
Cr3+ and (b, c) mixture of anions (F−, Cl−, Br−, I−, NO3 , ClO4 , IO3 , CO32−, SO42−, P2O74−, 1 × 10−3 mol/L for each) with/without Cr2O72− and
2−
CrO4
.
I0/I = 1.64 × exp(1057 × [Cr3+]) + 0.124 in the range from 1
× 10−6 to 1 × 10−3 mol/L (Figure 7a) (I0 and I are the
luminescent intensities of 3 in the absence and presence of
Cr3+, respectively), and so the concentration of Cr3+ ion can be
F
DOI: 10.1021/acs.inorgchem.7b00311
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
Figure 7. Dose−response graphs during detection of (a) Cr3+ in the range from 1 × 10−6 to 1 × 10−3 mol/L and (c) Cr2O72− and (e) CrO42− in the
2−
range from 1 × 10−6 to 2 × 10−3 mol/L (I0 and I are the luminescent intensities of 3 in the absence and presence of Cr3+, Cr2O72−, and CrO4
,
respectively), and linear relationships at low concentrations of (b) Cr3+, (d) Cr2O72−, and (f) CrO42− in the range from 1 × 10−7 to 1 × 10−6 mol/L.
2−
accurately quantified by the quenching of luminescence
intensity.31 A good linear correlation was observed for the
plot of (I0 − I)/I0 vs [Cr3+] in the range from 1 × 10−7 to 1 ×
10−6 mol/L ((I0 − I)/I0 = 50972 × [Cr3+] + 0.003, R2 = 0.990)
(Figure 7b). The slope of this graph indicates a very low
detection limit of 0.88 ppb for Cr3+ (3δ/slope, where δ is the
standard deviation (2.87 × 10−7) calculated by measuring the
luminescent intensity of a blank solution 10 times).21f This
value is much lower than that reported for MOFs used for
fluorescence-based sensing of Cr3+ (21.3 ppb for {[Eu(HL)-
The aqueous suspension of 3 could also detect Cr2O7 at
2−
pH = 3 and CrO4 at pH = 12. These dose−response graphs
fitted the relationship I0/I = 2.582 × exp(1630 × [Cr2O72−]) −
1.078) (for Cr2O72−, Figure 7c) and I0/I = 1.962 × exp(1767 ×
[CrO42−]) − 0.007) (for CrO42−, Figure 7e) in the range from
1 × 10−6 to 2 × 10−3 mol/L, while linear correlations were also
observed for (I0 − I)/I0 = 70913 × [Cr2O72−] + 0.054 (R2 =
0.990, Figure 7d) and (I0 − I)/I0 = 73481 × [CrO42−] + 0.053
(R2 = 0.991, Figure 7f) within the range from 1 × 10−7 to 1 ×
10−6 mol/L. Detection limits were calculated to be 2.623 (for
Cr2O72−) and 1.734 ppb (for CrO42−). The intact framework of
3 after sensing was confirmed by PXRD (Figure S6). The
18
(H2O)3]·H2O}n and 94.2 ppb for [Zn2(TPOM)(NH2-
BDC)2]·4H2O20).
G
DOI: 10.1021/acs.inorgchem.7b00311
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
Figure 8. (a) Schematic of the luminescent quenching mechanism experiment. Comparison of the emission spectra of 3 (excited at 378 nm) with
(b) Cr2O72−, (c) CrO42−, and (d) Cr3+. Black curves, 3 solely in position A; blue curves, mixture of 3 and chromium ions (1 × 10−3 mol/L) in
position A; red curves, 3 in position A and chromium ions in position B; green curves, 3 in position A and chromium ion in position C.
maximum contaminant level (MCL) of drinking water for
chromium set is 100 ppb by the United States Environmental
Protection Agency (USEPA) and 50 ppb by the European
Union (Council directive 9/83/EC).32 The detection limits of
3 toward both Cr(III) and Cr (VI) are well below these levels
and much lower than some other reported CPs-based single-
function sensors of either Cr(III) or Cr (VI).21
solutions were placed in the excitation path, the luminescence
of 3 was greatly weakened. When put in the emission path,
2−
Cr2O7 also absorbed much of the emission light whereas the
2−
effect of CrO4 was somewhat minor. These results indicated
that the luminescent quenching of 3 by CrO42− is mainly due to
2−
the energy transfer from the excitation light to the CrO4
2−
anion, while that by Cr2O7 is probably due to the energy
Proposed Mechanism. Quenching of luminescence for a
detecting material usually involves the so-called energy transfer
or the interaction of substrates with the luminescent group.
Researchers have found that overlap of the absorption by the
substrate with the excitation and/or emission of the detector
transfers from both excitation and emission processes to the
dissolved Cr2O7 anion.
34
2−
In contrast to the Cr(VI) anions, the results for Cr3+
luminescence quenching were quite different. When the Cr3+
solution was put in the excitation or emission path, the
photoluminescence of 3 did not get decreased obviously
because the absorption of Cr3+ has only a minor overlap with
the excitation or emission bands of 3 (Figure S7). Moreover, as
mentioned before, the luminescence of 3 was evidently
quenched when a suspension of 3 was mixed with Cr3+
solution. Therefore, quenching by Cr3+ should not be due to
energy transfer. Considering that one pyridyl group of the tpeb
ligand in 3 remains uncoordinated (as in 1 and 2), we propose
that the mechanism behind the sensing selectivity of Cr3+ is the
weak coordination between Cr3+ and the uncoordinated pyridyl
groups. An EDS test indicated that the ratio of Cr:Zn on the
surface of solid 3 after sensing Cr3+ (1 × 10−3 mol/L) was 1:15,
showing the existence of coordinated Cr3+. However, ICP
analysis showed the ratio of Cr:Zn was 1:50 (1.829 × 10−5 and
8.996 × 10−3 mol/L, respectively) for the bulk phase,
illustrating that Cr3+ only interacted with the surface of solid
2−
might cause the intermolecular energy transfer. Both Cr2O7
and CrO42− have wide absorption bands in the UV−vis region,
2−
from 275 to 476 nm for Cr2O7 and 230 to 450 nm for
CrO42−, which overlap with the excitation and/or emission
bands of 3 (Figure S7). Hence, we performed an experiment to
investigate whether the energy transfer caused the observed
quenching effect. As shown in Figure 8a, a suspension of
compound 3 in water was placed in a quartz cell (position A),
2−
while another one containing the solution of Cr2O72−, CrO4
,
and Cr3+ ions (2 × 10−3 mol/L) was placed in the excitation
path (position B) or emission path (position C). Under
excitation at 378 nm, the luminescent intensities of 3 (black
curves) and 3 with the chromium ions inserted into the
excitation path (red curves) or the emission path (green
curves) were compared to that of the mixture of 3 with the
2−
2−
chromium ions (blue curves). When Cr2O7 and CrO4
H
DOI: 10.1021/acs.inorgchem.7b00311
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
3. To further verify the interaction between the backbone and
Cr3+, XPS spectra of 3 before and after exposure to Cr3+
solution were compared (Figure S8). A characteristic peak for
Cr3+ was found in its XPS spectrum of the post-treated sample
of 3.
AUTHOR INFORMATION
■
Corresponding Authors
*E-mail: renzhigang@suda.edu.cn. Phone: 86-512-65880328.
*E-mail: jplang@suda.edu.cn. Fax: 86-512-65880328. Phone:
86-512-65882865.
The energy transfer (for Cr2O72− and CrO42−) and the weak
coordination (for Cr3+) mechanisms for each analyte were
confirmed by check experiments. When compound 3 was
separated from a solution of Cr(VI) anion by centrifugation, its
original luminescent intensity might get recovered (Figure S9).
Very little efficiency decay was observed when 3 was reused in
detecting Cr(VI) anions after three cycles (Figure S10).
However, the photoluminescence of 3 cannot be recovered
by washing after exposure to Cr3+ (Figure S9), which supports
our hypothesis of relatively tight binding. The blue shift (∼50
nm) of the highest emission peak at 474 nm (Figure S5) is also
an evidence of a weak coordination interaction.20,33 The
reusability of 3 by removal of Cr3+ was investigated by flushing
with a Na2Y (Y = ethylene diamine tetraacetate) solution (0.1
mol/L). The photoluminescence of 3 could only be recovered
to 60% after the first run and decreased steadily during 3 cycles
(Figure S11) but could still be fully quenched by using Cr3+
solution afterward.
ORCID
Jian-Ping Lang: 0000-0003-2942-7385
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
The authors thank the National Natural Science Foundation of
China (21271134, 21373142, 21531006, and 21671144) and
State Key Laboratory of Organometallic Chemistry, Shanghai
Institute of Organic Chemistry, Chinese Academy of Sciences
(2015kf-07) for financial support. J.P.L. also highly appreciates
financial support from the “Qing-Lan” Project, the “Priority
Academic Program Development” of Jiangsu Higher Education
Institutions, and the “SooChow Scholar” Program of Soochow
University. We are very grateful to the useful comments of the
editor and the reviewers.
REFERENCES
■
CONCLUSIONS
■
(1) Vaidyanathan, V. G.; Weyhermuller, T.; Nair, B. U.;
Subramanian, J. DNA Damage Induced by a Chromium (III) Schiff
Base Complex is Reversible under Physiological Condition. J. Inorg.
Biochem. 2005, 99, 2248−2255.
(2) Manning, F. C. R.; Blankenship, L. J.; Wise, J. P.; Xu, J.;
Bridgewater, L. C.; Patierno, S. R. Induction of Internucleosomal DNA
Fragmentation by Carcinogenic Chromate: Relationship to DNA
Damage, Genotoxicity, and Inhibition of Macromolecular Synthesis.
Environ. Health Persp. 1994, 102, 159−167.
(3) Sugden, D.; Geer, R. D.; Rogers, S. J. Oxygen Radical-Mediated
DNA Damage by Redox-Active Chromium (III) Complexes.
Biochemistry 1992, 31, 11626−11631.
(4) (a) Sugden, K. D.; Stearns, D. M. The Role of Chromium (V) in
the Mechanism of Chromate-Induced Oxidative DNA Damage and
Cancer. J. Environ. Pathol. Toxicol. Oncol. 2000, 19, 215−230.
(b) Zhitkovich, A.; Song, Y.; Quievryn, G.; Voitkun, V. Non-Oxidative
Mechanisms are Responsible for the Induction of Mutagenesis by
Reduction of Cr(VI) with Cysteine: Role of Ternary DNA Adducts in
Cr(III)-dependent Mutagenesis. Biochemistry 2001, 40, 549−560.
(c) Manygoats, K. R.; Yazzie, M.; Stearns, D. M. Ultrastructural
Damage in Chromium Picolinate-Treated Cells: A TEM Study. JBIC, J.
Biol. Inorg. Chem. 2002, 7, 791−798. (d) Ksheminska, H.; Fedorovych,
D.; Babyak, L.; Yanovych, D.; Kaszycki, P.; Koloczek, H.; Ksheminska,
H.; Fedorovych, D.; Babyak, L.; Yanovych, D.; Kaszycki, P.; Koloczek,
H. Chromium (III) and (VI) Tolerance and Bioaccumulation in Yeast:
A Survey of Cellular Chromium Content in Selected Strains of
Representative Genera. Process Biochem. 2005, 40, 1565−1572.
(5) (a) Warren, G.; Schultz, P.; Bancroft, D.; Bennett, K.; Abbott, E.
H.; Rogers, S. Mutagenicity of a Series of Hexacoordinate Chromium
(III) Compounds. Mutat. Res., Genet. Toxicol. Test. 1981, 90, 111−118.
(b) Elias, Z.; Poirot, O.; Schneider, O.; Daniere, M. C.; Terzetti, F.;
Guedenet, J. C.; Cavelier, C. Cellular Uptake, Cytotoxic and
Mutagenic Effects of Insoluble Chromic Oxide in V79 Chinese
Hamster Cells. Mutat. Res., Genet. Toxicol. Test. 1986, 169, 159−170.
(c) Arakawa, H.; Ahmad, R.; Naoui, M.; Tajmir-Riahi, H. A. A
Comparative Study of Calf Thymus DNA Binding to Cr(III) and
Cr(VI) Ions. J. Biol. Chem. 2000, 275, 10150−10153.
A family of strongly luminescent Zn−CPs 1−3 was successfully
constructed using the π-conjugated ligand tpeb. These
compounds have a 2D grid-like network (1) or 1D double-
chain structures (2 and 3). Highly emissive photoluminescence
coupled with exposed, uncoordinated pyridyl group active sites
and good water stability over a wide pH range proved to be an
ideal combination of features for the efficient and selective
sensing of Cr3+, Cr2O72−, and CrO42− ions. The detection limit
for the most responsive 3 was 0.88 ppb for Cr3+ and 2.623 ppb
2−
2−
for Cr2O7 (pH = 3) or 1.734 ppb for CrO4 (pH = 12),
which are well below the permissible limits set by the USEPA
and European Union and the lowest so far reported for any bi/
trifunctional CPs sensor materials. Our present work
demonstrates the potential of fluorescent CP-based materials
to be practical probes for the detection of hazardous metal ions
in different states.
ASSOCIATED CONTENT
■
S
* Supporting Information
The Supporting Information is available free of charge on the
ACS Publications website at DOI: 10.1021/acs.inorg-
chem.7b00311.
Additional information regarding the synthetic procedure
of tpeb ligand, TGA, selected bond distances, emission
spectra in the solid state, PXRD patterns, XPS spectra of
1−3, emission spectra during the sensing procedures,
and the proposed mechanisms (PDF)
X-ray crystallographic data in CIF format (CIF)
Accession Codes
CCDC 1529426, 1529427, and 1529428 contain the
supplementary crystallographic data for this paper. These data
can be obtained free of charge via www.ccdc.cam.ac.uk/data_
request/cif, by emailing data_request@ccdc.cam.ac.uk, or by
contacting The Cambridge Crystallographic Data Centre, 12
Union Road, Cambridge CB2 1EZ, UK; fax: +44 1223 336033.
(6) Sperling, M.; Xu, S.; Welz, B. Determination of Chromium (III)
and Chromium (VI) in Water Using Flow Injection On-Line
Preconcentration with Selective Adsorption on Activated Alumina
and Flame Atomic Absorption Spectrometric Detection. Anal. Chem.
1992, 64, 3101−3108.
I
DOI: 10.1021/acs.inorgchem.7b00311
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
(7) (a) Subramanian, K. S. Determination of Chromium (III) and
Chromium (VI) by Ammonium Pyrrolidinecarbodithioate-Methyl
Isobutyl Ketone-Furnace Atomic Absorption Spectrometry. Anal.
Chem. 1988, 60, 11−15. (b) Orvini, E.; Zerlia, T.; Gallorini, M. S.
M. Determination of Chromium (VI) and Chromium (III) Traces in
Natural Waters by Neutron Activation Analysis. Radiochem. Radioanal.
Lett. 1980, 43, 173−184. (c) Brown, D. A.; Glass, W. K.; Jan, M. R.;
Mulders, R. M. W. Investigation of Hydroxamic Acids for the
Extraction of Chromium (III) from Leather Waste and the Possible
Re-Use of the Extracted Chromium in the Tanning Industry. Environ.
Technol. Lett. 1986, 7, 283−288.
(8) (a) Kiran, K.; Kumar, K. S.; Prasad, B.; Suvardhan, K.; Lekkala, L.
B.; Janardhanam, K. Speciation Determination of Chromium (III) and
(VI) Using Preconcentration Cloud Point Extraction with Flame
Atomic Absorption Spectrometry (FAAS). J. Hazard. Mater. 2008,
150, 582−586. (b) Posta, J.; Berndt, H.; Luo, S. K.; Schaldach, G.
High-Performance Flow Flame Atomic Absorption Spectrometry for
Automated On-Line Separation and Determination of Chromium
(III)/Chromium (VI) and Preconcentration of Chromium (VI). Anal.
Chem. 1993, 65, 2590−2595. (c) Metters, J. P.; Kadara, R. O.; Banks,
C. E. Electroanalytical Sensing of Chromium (III) and (VI) Utilizing
Gold Screen Printed Macro Electrodes. Analyst 2012, 137, 896−902.
(d) Miyazaki, A.; Barnes, R. M. Differential Determination of
Chromium (VI)- Chromium (III) with Poly(dithiocarbamate)
Chelating Resin and Inductively Coupled Plasma-Atomic Emission
Selective Detection of Nitroaromatic Explosive Vapours Using
Fluorescent Polymer Thin Fi. Chem. Commun. 2013, 49, 6140−
6142. (g) Lashgaria, N.; Badieia, A.; Ziarani, G. M. Modification of
Mesoporous Silica SBA-15 with Different Organic Molecules to Gain
Chemical Sensors: A Review. Nano. Chem. Res. 2016, 1, 127−141.
(11) Zhang, L.; Xu, C.; Li, B. Simple and Sensitive Detection Method
for Chromium (VI) in Water Using Glutathione-Capped CdTe
Quantum Dots as Fluorescent Probes. Microchim. Acta 2009, 166, 61−
68.
(12) (a) Toal, S. J.; Jones, K. A.; Magde, D.; Trogler, W. C.
Luminescent Silole Nanoparticles as Chemoselective Sensors for
Cr(VI). J. Am. Chem. Soc. 2005, 127, 11661−11665. (b) Li, F. M.; Liu,
J. M.; Wang, X. X.; Lin, L. P.; Cai, W. L.; Lin, X.; Zeng, Y. N.; Li, Z.
M.; Lin, S. Q. Non-Aggregation Based Label Free Colorimetric Sensor
for the Detection of Cr(VI) Based on Selective Etching of Gold
Nanorods. Sens. Actuators, B 2011, 155, 817−822.
(13) Zheng, M.; Xie, Z.; Qu, D.; Li, D.; Du, P.; Jing, X.; Sun, Z. On-
Off-On Fluorescent Carbon Dot Nanosensor for Recognition of
Chromium (VI) and Ascorbic Acid Based on the Inner Filter Effect.
ACS Appl. Mater. Interfaces 2013, 5, 13242−13247.
(14) Zamani, H. A.; Rajabzadeh, G.; Masrornia, M.; Dejbord, A.;
Ganjali, M. R.; Seifi, N. Determination of Cr3+ Ions in Biological and
Environmental Samples by a Chromium (III) Membrane Sensor
Based on 5-Amino-1-Phenyl-1H-Pyrazole-4-Carboxamide. Desalination
2009, 249, 560−565.
Spectrometry. Anal. Chem. 1981, 53, 364−366. (e) Gurleyuk, H.;
̈
̈
(15) (a) Saluja, P.; Sharma, H.; Kaur, N.; Singh, N.; Jang, D. O.
Benzimidazole-Based Imine-Linked Chemosensor: Chromogenic
Sensor for Mg2+ and Fluorescent Sensor for Cr3+. Tetrahedron 2012,
68, 2289−2293. (b) Li, Z. X.; Zhao, W. Y.; Zhang, Y. N.; Zhang, L. F.;
Yu, M. M.; Liu, J. X.; Zhang, H. Y. An “Off-On” Fluorescent
Chemosensor of Selectivity to Cr3+ and Its Application to MCF-7
Cells. Tetrahedron 2011, 67, 7096−7100. (c) Kim, H.; Kim, Y.; Chang,
J. Y. Polymers for Luminescent Sensing Applications. Macromol. Chem.
Phys. 2014, 215, 1274−1285.
Wallschlager, D. Determination of Chromium (III) and Chromium
̈
(VI) Using Suppressed Ion Chromatography Inductively Coupled
Plasma Mass Spectrometry. J. Anal. At. Spectrom. 2001, 16, 926−930.
(f) Narin, I.; Kars, A.; Soylak, M. A Novel Solid Phase Extraction
Procedure on Amberlite XAD-1180 for Speciation of Cr(III), Cr(VI)
and Total Chromium in Environmental and Pharmaceutical Samples.
J. Hazard. Mater. 2008, 150, 453−458. (g) Sikovec, M.; Franko, M.;
Novic, M.; Veber, M. Effect of Organic Solvents in the On-Line
Thermal Lens Spectrometric Detection of Chromium (III) and
Chromium (VI) after Ion Chromatographic Separation. J. Chromatogr.
A 2001, 920, 119−125.
(16) (a) Cui, Y.; Yue, Y.; Qian, G.; Chen, B. L. Luminescent
Functional Metal-Organic Frameworks. Chem. Rev. 2012, 112, 1126−
1162. (b) Hu, Z.; Deibert, B. J.; Li, J. Luminescent Metal-Organic
Frameworks for Chemical Sensing and Explosive Detection. Chem. Soc.
Rev. 2014, 43, 5815−5840. (c) Chen, M. M.; Chen, L.; Li, H. X.;
Brammer, L.; Lang, J. P. Highly Selective Detection of Hg2+ and
MeHgI by Di-Pyridin-2-yl-[4-(2-Pyridin-4-yl-Vinyl)-Phenyl]-Amine
and Its Zinc Coordination Polymer. Inorg. Chem. Front. 2016, 3,
1297−1305. (d) Chen, M. M.; Zhou, X.; Li, H. X.; Yang, X. X.; Lang, J.
P. Luminescent Two-Dimensional Coordination Polymer for Selective
and Recyclable Sensing of Nitroaromatic Compounds with High
Sensitivity in Water. Cryst. Growth Des. 2015, 15, 2753−2760. (e) Hu,
F. L.; Shi, Y. X.; Chen, H. H.; Lang, J. P. A Zn(II) Coordination
Polymer and Its Photocycloaddition Product: Syntheses, Structures,
Selective Luminescence Sensing of Iron (III) Ions and Selective
Absorption of Dyes. Dalton Trans. 2015, 44, 18795−18803. (f) Dai,
M.; Gu, T. Y.; Zhao, X.; Li, H. X.; Lang, J. P. Formation of Zn(II) and
Pb(II) Coordination Polymers of Tetrakis(4-pyridyl)Cyclobutane
Controlled by Benzene and Toluene. CrystEngComm 2015, 17,
8345−8352. (g) Dai, M.; Su, X. R.; Wang, X.; Wu, B.; Ren, Z. G.;
Zhou, X.; Lang, J. P. Three Zinc (II) Coordination Polymers Based on
Tetrakis(4-pyridyl)Cyclobutane and Naphthalenedicarboxylate Link-
ers: Solvothermal Syntheses, Structures, and Photocatalytic Properties.
Cryst. Growth Des. 2014, 14, 240−248. (h) Wang, B.; Lv, X. L.; Feng,
D. W.; Xie, L. H.; Zhang, J.; Li, M.; Xie, Y. B.; Li, J. R.; Zhou, H. C.
Highly Stable Zr(IV)-Based Metal-Organic Frameworks for the
Detection and Removal of Antibiotics and Organic Explosives in
Water. J. Am. Chem. Soc. 2016, 138, 6204−6216.
́ ̌ ́ ̌ ́ ̌
(9) (a) Kuban, P.; Kuban, P.; Kuban, V. Speciation of Chromium
(III) and Chromium (VI) by Capillary Electrophoresis with
Contactless Conductometric Detection and Dual Opposite End
Injection. Electrophoresis 2003, 24, 1397−1403. (b) Bond, A. M.;
Wallace, G. G. Simultaneous Determination of Copper, Nickel, Cobalt,
Chromium (VI), and Chromium (III) by Liquid Chromatography
with Electrochemical Detection. Anal. Chem. 1982, 54, 1706−1712.
(c) Zhao, T.; Hou, X.; Xie, Y.; Wu, L.; Wu, P. Phosphorescent Sensing
of Cr3+ with Protein-Functionalized Mn-Doped ZnS Quantum Dots.
Analyst 2013, 138, 6589−6594. (d) Jena, B. K.; Raj, C. R. Highly
Sensitive and Selective Electrochemical Detection of Sub-ppb Level
Chromium (VI) Using Nano-Sized Gold Particle. Talanta 2008, 76,
161−165. (e) Nagarkar, S. S.; Joarder, B.; Chaudhari, A. K.;
Mukherjee, S.; Ghosh, S. K. Highly Selective Detection of Nitro
Explosives by a Luminescent Metal-Organic Framework. Angew. Chem.
2013, 125, 2953−2957.
(10) (a) Mao, J.; Wang, L.; Dou, W.; Tang, X.; Yan, Y.; Liu, W.
Tuning the Selectivity of Two Chemosensors to Fe(III) and Cr(III).
Org. Lett. 2007, 9, 4567−4570. (b) Resendiz, M. J. E.; Noveron, J. C.;
Fischer, H.; Disteldorf, S.; Stang, P. J. A Self-Assembled Supra-
molecular Optical Sensor for Ni(II), Cd(II), and Cr(III). Org. Lett.
2004, 6, 651−653. (c) Xia, W. S.; Schmehl, R. H.; Li, C. J.; Mague, J.
T.; Luo, C. P.; Guldi, D. M. Chemosensors for Lead (II) and Alkali
Metal Ions Based on Self-Assembling Fluorescence Enhancement
(SAFE). J. Phys. Chem. B 2002, 106, 833−843. (d) Xue, H.; Tang, X.
J.; Wu, L. Z.; Zhang, L. P.; Tung, C. H. Highly Selective Colorimetric
and Electrochemical Pb2+ Detection Based on TTF-π-Pyridine
Derivative. J. Org. Chem. 2005, 70, 9727−9734. (e) Gole, B.; Bar, A.
K.; Mukherjee, P. S. Modification of Extended Open Frameworks with
Fluorescent Tags for Sensing Explosives: Competition between Size
Selectivity and Electron Deficien. Chem. - Eur. J. 2014, 20, 2276−2291.
(f) Demirel, G. B.; Daglar, B.; Bayindir, M. Extremely Fast and Highly
(17) (a) Shi, P. F.; Zhao, B.; Xiong, Ga.; Hou, Y. L.; Cheng, P. Fast
Capture and Separation of, and Luminescent Probe for, Pollutant
Chromate Using a Multi-Functional Cationic Heterometal-Organic
Framework. Chem. Commun. 2012, 48, 8231−8233. (b) Li, X. X.; Xu,
H. Y.; Kong, F. Z.; Wang, R. H. A Cationic Metal-Organic Framework
Consisting of Nanoscale Cages: Capture, Separation, and Luminescent
J
DOI: 10.1021/acs.inorgchem.7b00311
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
Probing of Cr2O72− through a Single-Crystal to Single-Crystal Process.
Angew. Chem., Int. Ed. 2013, 52, 13769−13773.
(27) (a) Sheldrick, G. M. Crystal Structure Refinement with
SHELXL. Acta Crystallogr., Sect. C: Struct. Chem. 2015, 71, 3−8.
(b) Spek, A. L. Single-crystal structure validation with the program
PLATON. J. Appl. Crystallogr. 2003, 36, 7−13.
(28) Park, I. H.; Medishetty, R.; Kim, J. Y.; Lee, S. S.; Vittal, J. J.
Distortional Supramolecular Isomers of Polyrotaxane Coordination
Polymers: Photoreactivity and Sensing of Nitro Compounds. Angew.
Chem., Int. Ed. 2014, 53, 5591−5595.
(29) (a) Allendorf, M. D.; Bauer, C. A.; Bhakta, R. K.; Houk, R. J. T.
Luminescent Metal-Organic Frameworks. Chem. Soc. Rev. 2009, 38,
1330−1352. (b) Li, S.; Lan, Y.; Ma, J.; Yang, J.; Wei, G.; Zhang, L.; Su,
Z. Structures and Luminescent Properties of Seven Coordination
Polymers of Zinc (II) and Cadmium (II) with 3,3′,4,4′-Benzophenone
Tetracarboxylate Anion and Bis(imidazole). Cryst. Growth Des. 2008,
8, 675−684. (c) Zhang, J.; Li, Z.; Kang, Y.; Cheng, J.; Yao, Y.
Hydrothermal Syntheses, Crystal Structures, and Properties of a Novel
Class of 3,3′,4,4′-Benzophenone-Tetracarboxylate (BPTC) Polymers.
Inorg. Chem. 2004, 43, 8085−8091.
(18) Wang, H. R.; Qin, J. H.; Huang, C.; Han, Y. B.; Xu, W. J.; Hou,
H. W. Mono/Bimetallic Water-Stable Lanthanide Coordination
Polymers as Luminescent Probes for Detecting Cations, Anions and
Organic Solvent Molecules. Dalton Trans. 2016, 45, 12710−12716.
(19) Yi, F. Y.; Li, J. P.; Wu, D.; Sun, Z. M. A Series of Multifunctional
Metal-Organic Frameworks Showing Excellent Luminescent Sensing,
Sensitization, and Adsorbent Abilities. Chem. - Eur. J. 2015, 21,
11475−11482.
(20) (a) Lv, R.; Wang, J. Y.; Zhang, Y. P.; Li, H.; Yang, L. Y.; Liao, S.
Y.; Gu, W.; Liu, X. An Amino-Decorated Dual-Functional Metal-
Organic Framework for Highly Selective Sensing of Cr(III) and
Cr(VI) Ions and Detection of Nitroaromatic Explosives. J. Mater.
Chem. A 2016, 4, 15494−15500. (b) Xiang, Z. H.; Fang, C. Q.; Leng,
S. H.; Cao, D. P. An Amino Group Functionalized Metal-Organic
Framework as a Luminescent Probe for Highly Selective Sensing of
Fe3+ Ions. J. Mater. Chem. A 2014, 2, 7662−7665.
(30) Liu, Z.; He, W.; Guo, Z. Metal Coordination in Photo-
luminescent Sensing. Chem. Soc. Rev. 2013, 42, 1568−1600.
(31) (a) Chang, H. H.; Tang, L. H.; Wang, Y.; Jiang, J. H.; Li, J. H.
Graphene Fluorescence Resonance Energy Transfer Aptasensor for
the Thrombin Detection. Anal. Chem. 2010, 82, 2341−2346.
(b) Zhou, L.; Lin, Y. H.; Huang, Z. Z.; Ren, J. S.; Qu, X. G. Carbon
Nanodots as Fluorescence Probes for Rapid, Sensitive, and Label-Free
Detection of Hg2+ and Biothiols in Complex Matrices. Chem. Commun.
2012, 48, 1147−1149. (c) Salinas, Y.; Martinez-Manez, R. M.; Marcos,
M. D.; Sancenon, F.; Costero, A. M.; Parra, M.; Gil, S. Optical
Chemosensors and Reagents to Detect Explosives. Chem. Soc. Rev.
2012, 41, 1261−1296.
(32) Linos, A.; Petralias, A.; Christophi, C. A.; Christoforidou, E.;
Kouroutou, P.; Stoltidis, M.; Veloudaki, A.; Tzala, E.; Makris, K. C.;
Karagas, M. R. Oral Ingestion of Hexavalent Chromium through
Drinking Water and Cancer Mortality in an Industrial Area of Greece-
an Ecological Study. Environ. Health 2011, 10, 50−57.
(21) (a) Jia, C.; Piao, D.; Oyamada, J.; Lu, W.; Kitamura, T.;
Fujiwara, Y. Efficient Activation of Aromatic C-H Bonds For Addition
to C-C Multiple Bonds. Science 2000, 287, 1992−1995. (b) Duan, L.;
Xu, Y.; Qian, X. Highly Sensitive and Selective Pd2+ Sensor of
Naphthalimide Derivative Based on Complexation with Alkynes and
Thio-Heterocycle. Chem. Commun. 2008, 6339−6341. (c) Gao, R. C.;
Guo, F. S.; Bai, N. N.; Wu, Y. L.; Yang, F.; Liang, J. Y.; Li, Z. J.; Wang,
Y. Y. Two 3D Isostructural Ln(III)-MOFs: Displaying the Slow
Magnetic Relaxation and Luminescence Properties in Detection of
Nitrobenzene and Cr2O72−. Inorg. Chem. 2016, 55, 11323−11330.
(d) Li, G. P.; Liu, G.; Li, Y. Z.; Hou, L.; Wang, Y. Y.; Zhu, Z. H.
Uncommon Pyrazoyl-Carboxyl Bifunctional Ligand-Based Micro-
porous Lanthanide Systems: Sorption and Luminescent Sensing
Properties. Inorg. Chem. 2016, 55, 3952−3959. (e) Cao, C. S.; Hu,
H. C.; Xu, H.; Qiao, W. Z.; Zhao, B. Two Solvent-Stable MOFs as a
Recyclable Luminescent Probe for Detecting Dichromate or Chromate
Anions. CrystEngComm 2016, 18, 4445−4451. (f) Xu, X. Y.; Yan, B.
Eu(III)-Functionalized MIL-124 as Fluorescent Probe for Highly
Selectively Sensing Ions and Organic Small Molecules Especially for
Fe(III) and Fe(II). ACS Appl. Mater. Interfaces 2015, 7, 721−729.
(g) Ning, Y.; Wang, L.; Yang, G. P.; Wu, Y. L.; Bai, N. N.; Zhang, W.
Y.; Wang, Y. Y. Four New Lanthanide-Organic Frameworks: Selective
Luminescent Sensing and Magnetic Properties. Dalton Trans. 2016,
45, 12800−12806. (h) Wen, L. L.; Zheng, X. F.; Lv, K. L.; Wang, C.
G.; Xu, X. Y. Two Amino-Decorated Metal-Organic Frameworks for
Highly Selective and Quantitatively Sensing of HgII and CrVI in
Aqueous Solution. Inorg. Chem. 2015, 54, 7133−7135.
(33) Huang, H.; Wang, K.; Tan, W.; Yang, D.; Huang, X.; Zhai, S.;
Zhou, Q.; Jin, L. Y. Design of a Modular-Based Fluorescent
Conjugated Polymer for Selective Sensing. Angew. Chem., Int. Ed.
2004, 43, 5635−5638.
(34) Muller-Buschbaum, K.; Beuerle, F.; Feldmann, C. MOF Based
̈
Luminescence Tuning and Chemical/Physical Sensing. Microporous
Mesoporous Mater. 2015, 216, 171−199.
(22) (a) Du, P. Y.; Gu, W.; Liu, X. Three Types of Lanthanide
Coordination Polymers from 1D to 3D Based on a Tetracarboxylate
Ligand: Synthesis, Structural Diversities and Properties. CrystEng-
Comm 2016, 18, 5140−5148. (b) Hu, D. C.; Fan, Y.; Si, C. D.; Wu, Y.
J.; Dong, X. Y.; Yang, Y. X.; Yao, X. Q.; Liu, J. C. A Series of Zn/Cd
Coordination Polymers Constructed from 1,4-Naphthalenedicarbox-
ylate and N-Donor Ligands: Syntheses, Structures and Luminescence
Sensing of Cr3+ in Aqueous Solutions. J. Solid State Chem. 2016, 241,
198−204.
(23) Amoroso, A. J.; Thompson, A. M. W.; Maher, C. J. P.;
McCleverty, J. A.; Ward, M. D. Di-, Tri-, and Tetranucleating Pyridyl
Ligands Which Facilitate Multicenter Magnetic Exchange between
Paramagnetic Molybdenum Centers. Inorg. Chem. 1995, 34, 4828−
4835.
(24) Sheldrick, G. M. SADABS Empirical Absorption Correction
Program, University of Gottingen, based on the method of Blessing.
̈
(25) Krause, L.; Herbst-Irmer, R.; Sheldrick, G. M.; Stalke, D.
Comparison of Silver and Molybdenum Microfocus X-ray Sources for
Single-Crystal Structure Determination. J. Appl. Crystallogr. 2015, 48,
3−10.
(26) Blessing, R. H. An Empirical Correction for Absorption
Anisotropy. Acta Crystallogr., Sect. A: Found. Crystallogr. 1995, 51,
33−38.
K
DOI: 10.1021/acs.inorgchem.7b00311
Inorg. Chem. XXXX, XXX, XXX−XXX