naphthalene and Its Zinc(II) Coordination Polymers ... - ACS Publications

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1,4-Bis(2-(pyridin-4-yl)vinyl)naphthalene and its Zinc(II) Coordination Polymers: Synthesis, Structural Characterization and Selective Luminescent Sensing of Mercury(II) ion Wu-Xiang Li, Hong-Xi Li, Hai-Yan Li, Min-Min Chen, Yi-Xiang Shi, and Jian-Ping Lang Cryst. Growth Des., Just Accepted Manuscript • Publication Date (Web): 19 May 2017 Downloaded from http://pubs.acs.org on May 21, 2017

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Crystal Growth & Design

1,4-Bis(2-(pyridin-4-yl)vinyl)naphthalene and its Zinc(II) Coordination

Polymers:

Synthesis,

Structural

Characterization and Selective Luminescent Sensing of Mercury(II) ion Wu-Xiang Li,† Hong-Xi Li,*,† Hai-Yan Li,† Min-Min Chen,† Yi-Xiang Shi,† Jian-Ping Lang*,†,‡ †

State and Local Joint Engineering Laboratory for Novel Functional Polymeric Materials,

College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou 215123, Jiangsu, 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

RECEIVED DATE (to be automatically inserted after your manuscript is accepted if required according to the journal that you are submitting your paper to) __________________________

†

Soochow University

‡

Shanghai Institute of Organic Chemistry

ACS Paragon Plus Environment

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ABSTRACT:

Solvothermal

reactions

of

Zn(NO3)2·6H2O

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with

1,4-bis(2-(pyridin-4-

yl)vinyl)naphthalene (1,4-bpyvna) and 1,3,5-benzenetricarboxylic acid (1,3,5-H3BTC) (molar ratio = 1 : 1 : 1) at 120 ºC in CH3CN/H2O (v/v = 1:2) afforded one three dimensional (3D) coordination polymer [Zn2(1,4-bpyvna)(1,3,5-HBTC)2(H2O)]n (1). Similar reactions with the same three components at 140 ºC in DMF/CH3CN/H2O produced another 3D coordination polymer {[Zn2(1,4-bpyvna)(1,3,5-BTC)(OH)]·H2O}n (2) in 72% yield. When the molar ratio of Zn(NO3)2·6H2O, 1,4-bpyvna and 1,3,5-H3BTC was changed to 1 : 1 : 2, the analogous treatment at 140 ºC yielded one 1D coordination polymer {[Zn(1,3,5-HBTC)2(H2O)][1,4-bpyvnaH2]·CH3CN}n

(3,

1,4-bpyvna-H2

=

4,4'-((1,1')-naphthalene-1,4-diylbis(ethene-2,1-

diyl))bis(pyridin-1-ium)). Solvothermal reactions of Zn(NO3)2·6H2O with equimolar 1,4-bpyvna and one or two equiv. of 4,4′-oxidibenzoic acid (4,4′-H2OBA) at 120 ºC in DMF/CH3CN/hexane resulted in the formation of {[Zn2(1,4-bpyvna)(4,4’-OBA)2]·0.5DMF·2.25H2O}n (4) and {[Zn2(1,4-bpyvna)(4,4’-OBA)2]·3DMF}n (5), respectively. Compounds 1-5 were characterized by elemental analysis, IR spectroscopy, powder X-ray diffraction, single-crystal X-ray diffraction and thermogravimetric analysis. Upon addition of Hg2+ ion to the DMF solution of 1,4-bpyvna, remarkable changes in the absorbance and emissive spectra were observed, associated with color changes, which were easily identified by the naked eyes. This ligand could serve as a chemoprobe with the detection limit of Hg2+ being 0.060 ppm. When solid 2 was added in the DMF solution containing Hg(NO3)2, the emission color of 2 was also changed from blue to yellow and its detection limit of Hg2+ was as low as 0.057 ppm. This compound can be reused for several cycles without evident efficiency decay. Compound 2 would be a promising sensitive naked-eye indicator for low-concentration Hg2+ with high sensitivity and selectivity.


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INTRODCTION

Since the last century, the world industrialization not only has greatly improved the people living standards but also brought a number of inorganic and/or organic pollutants which may gradually destroy the natural environment and even the health of human beings. Mercury ion is one of such pollutants because it is highly toxic, mobile, and bio-accumulated in the ecosystem and its role in environmental pollution.1-3 How to detect very low concentrations of Hg2+ in laboratory model systems and even in nature systems has been and continues to be a big challenge. Currently, various technologies for detection of Hg2+ including atomic absorption spectroscopy,4 atomic fluorescence spectrometry,5 liquid chromatography,6 mass spectroscopy,7 gas chromatography,

capillary

electrophoresis8

spectrometry9,10 have been developed.

and

inductively

coupled

plasma-mass

Among these techniques, the luminescence-based

detection techniques11-14 for probing Hg2+ have been widely used due to their following advantages, i.e., rapid response, high sensitivity, easy operation, and visualization. A large number of organic polymers,15-17 organic dyes,18-21 metal nanoparticles,22-24 carbon nanomaterials25-28 and semiconductor quantum dots29-31 have been employed as fluorescence probes for sensing Hg2+. In recent years, luminescent coordination polymers (CPs) have attracted much attention owing to their designable architectures, robust thermal stability and various chemical and physical properties.32-34 The molar ratios of reactants, pH values, solvent systems, counter ions, templates and reaction temperatures and so on could impose effects on the final structures of the resulting CPs.35-45 Moreover, the fluorescent properties of CPs are tunable through modifying organic ligands, metal ions/cluster units and even the CPs structures.46-47 Up to now, various CPs have been synthesized as effective luminescent probes for detecting inorganic and/or organic cations, anions and neutral molecules.48-58 Many pyridine-appended π-


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conjugated derivatives have proved to be as efficient sensing fluorophores for metal ions and the π-conjugated groups may impose their selectivity and sensitivity.59-63 For example, the ligand 1,4-bis[2-(4-pyridyl)ethenyl]benzene (bpeb) with a longer π-conjugated spacer (C=C-Ph-C=C) showed higher selectivity and sensitivity for detecting Hg2+ than the liagnd di(4-pyridyl)ethylene with a shorter π-conjugated spacer (C=C).64 However, compared with organic probes,65-73 the CP-based sensors for probing Hg2+ are quite limited in numbers.74-79 Can expanding the πconjugation of the aforementioned ligand bpeb increase the selectivity and sensitivity for sensing Hg2+? With this question in mind, we delicately chose and prepared a bpeb analogue, 1,4-bis(2(pyridin-4-yl)vinyl)naphthalene (1,4-bpyvna), in which a larger π-conjugated naphthalene group replaces the central phenyl group in bpeb. Its reactions with Zn(NO3)2·6H2O in the presence of 1,3,5-benzenetricarboxylic acid (1,3,5-H3BTC) or 4,4′-oxidibenzoic acid (4,4′-H2OBA) under different solvothermal conditions gave rise to five unique CPs [Zn2(1,4-bpyvna)(1,3,5HBTC)2(H2O)]n

(1),

{[Zn2(1,4-bpyvna)(1,3,5-BTC)(OH)]·H2O}n

(2),

{[Zn(1,3,5-

HBTC)2(H2O)][1,4-bpyvna-H2]·CH3CN}n (3; 1,4-bpyvna-H2 = 4,4'-((1,1')-naphthalene-1,4diylbis(ethene-2,1-diyl))bis(pyridin-1-ium)), {[Zn2(1,4-bpyvna)(4,4’-OBA)2]·DMF·5H2O}n (4) and {[Zn2(1,4-bpyvna)(4,4’-OBA)2]·3DMF}n (5). The ligand 1,4-bpyvna and the representative sample 2 were found to work as good luminescent probes for detecting Hg2+ ion in low concentrations. Herein we describe their synthesis, structural characterization, and luminescence sensing properties.

EXPERIMENTAL SECTION


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General Procedure. All chemicals were commercially available and used as received without further purification. The instruments engaged in this paper were the same as those employed in our preceding works unless otherwise noted.56,58 Preparation of 1,4-bis(2-(pyridin-4-yl)vinyl)naphthalene (1,4-bpyvna). A mixture containing 4-vinylpyridine (0.78 g, 7.5 mmol), 1,4-dibromonaphthalene (0.86 g, 3 mmol), (PPh3)2PdCl2 (0.042 g, 0.06 mmol), K2CO3 (0.83 g, 6 mmol) and DMF (6 mL) was added into a 50 mL Schlenk tube. The tube was evacuated and flushed with nitrogen for three times. The mixture was then heated at 120 ºC for 18 hours and then cooled to ambient temperature. The residue formed was dissolved in H2O and extracted with CH2Cl2 (3 × 15 mL). The combined organic layers were washed with brine, dried over Na2SO4, and concentrated in vacuo. The resulting solid was purified by flash chromatography on silica gel to give 1,4-bpyvna. Yield: 0.93 g (93%). Mp: 239 ºC. Anal. Calcd. for C24H18N2: C, 86.23; H, 5.39; N, 8.38%. Found: C, 86.62; H, 5.67; N, 8.57%. IR (KBr disk): 3031 (w), 1589 (s), 1411 (m), 1384 (w), 1160 (m), 968 (m), 878 (w), 807 (w), 760 (m), 616 (m), 554 (m), 527 (m) cm-1. 1H NMR (400 MHz, DMSO-d6): δ 8.60 (d, J = 4.5 Hz, 4H), 8.54 (dd, J = 6.1, 3.0 Hz, 2H), 8.41 (d, J = 16.1 Hz, 2H), 8.02 (s, 2H), 7.77 (d, J = 4.8 Hz, 4H), 7.68 (dd, J = 6.1, 2.7 Hz, 2H), 7.37 (d, J = 16.1 Hz, 2H).

13

C NMR

(151 MHz, DMSO-d6): δ 150.4, 144.7, 134.4, 131.5, 129.8, 129.6, 127.0, 124.9, 124.1, 121.7, 40.4, 40.2, 40.1, 39.9, 39.8, 39.7, 39.5. Preparation of [Zn2(1,4-bpyvna)(1,3,5-HBTC)2(H2O)]n (1). To a Pyrex glass tube (25 cm in length, 7 mm in inner diameter) were added Zn(NO3)2·6H2O (29.7 mg, 0.1 mmol), 1,3,5-H3BTC (21 mg, 0.1 mmol), 1,4-bpyvna (33.4 mg, 0.1 mmol), 2 mL CH3CN and 4 mL H2O. The tube was sealed and heated in an oven at 120 ºC for 48 h and then cooled to room temperature at a rate of 5 ºC h-1 to form yellow crystals of 1, which were collected by filtration, washed with


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EtOH and dried in air. Yield: 66 mg (37% based on Zn). Anal. Calcd. for C42H28N2O13Zn2: C 56.12, N 3.12, H 3.12%. Found: C 56.43, N 4.23, H, 3.19%. IR (KBr disk): 3423 (s), 1610 (s), 1575 (m), 1435 (m), 1374 (m), 957 (w), 877 (w), 756 (m), 723 (m), 620 (W), 520 (w) cm-1. Preparation of {[Zn2(1,4-bpyvna)(1,3,5-BTC)(OH)]·H2O}n (2).

Red crystals of 2 were

prepared as above starting from Zn(NO3)2·6H2O (29.7 mg 0.1 mmol), 1,3,5-H3BTC (21 mg, 0.1 mmol), 1,4-bpyvna (33.4 mg, 0.1 mmol), 0.5mL DMF, 2 mL MeCN and 4 mL H2O at 140 ºC for 48 h. Yield: 101 mg (72% based on Zn). Anal. Calcd. for C33H18N2O8Zn2: C 56.57, N 4.00, H 2.57%. Found: C 56.82, N 4.07, H, 2.84%. IR (KBr disk): 3412 (s), 1722 (s), 1610 (s), 1504 (m),1435 (m), 1376 (m), 955 (w), 874 (w), 761 (m), 714 (m), 626(m), 514 (w) cm-1. Preparation of {[Zn(1,3,5-HBTC)2(H2O)][1,4-bpyvna-H2]·CH3CN}n (3). Yellow crystals of 3 were obtained by a similar manner to that used for the isolation of 2, using Zn(NO3)2·6H2O (29.7mg 0.1 mmol), 1,3,5-H3BTC (63 mg, 0.2 mmol) and 1,4-bpyvna (33.4 mg, 0.1 mmol) as starting materials. Yield: 70 mg (81% based on Zn). Anal. Calcd. for C44H26N3O13 Zn: C 60.76, N 4.83, H 2.99%. Found: C 60.88, N 4.91, H, 4.89%. IR (KBr disk): 1685 (s),1613 (s), 1579 (m), 1435 (m), 1367 (s), 961 (w), 882 (w), 752 (m), 729 (m), 623 (W), 508 (w) cm-1. Preparation of {[Zn2(1,4-bpyvna)(4,4’-OBA)2]·0.5DMF·2.25H2O}n (4). Yellow crystals of 4 were prepared by an analogous method to that used for the isolation of 2, using Zn(NO3)2·6H2O (29.7 mg 0.1 mmol), 4,4’-H2OBA (25.8 mg, 0.1 mmol), 1,4-bpyvna (33.4 mg, 0.1 mmol) and 4 mL DMF/CH3CN/hexane (v/v/v = 3:3:1) as starting materials at 120 ºC for 48 h. Yield: 150 mg (73% based on Zn). Anal. Calcd. for C53.50H43N2.50O12.75Zn2: C 60.91, N 3.32, H 4.08%. Found: C 61.23, N 3.40, H, 3.86%. IR (KBr disk): 3446 (m), 1671 (s), 1643 (m), 1610 (m), 1499 (m), 1394 (s), 1232 (s), 957 (w), 877 (m), 780 (m), 659 (m), 628 (w), 512 (w) cm-1.


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Preparation of {[Zn2(1,4-bpyvna)(4,4’-OBA)2]·3DMF}n (5). Yellow crystals of 5 were produced as above starting from Zn(NO3)2·6H2O (29.7 mg, 0.1 mmol), 4,4’-H2OBA (51.6 mg, 0.2 mmol), and 1,4-bpyvna (33.4 mg, 0.1 mmol) in a 4 mL DMF/CH3CN/Hexane (v/v/v= 3:3:1) at 120 ºC for 48 h. Yield: 297 mg (69% based on Zn). Anal. Calcd. for C113H70N7O23Zn4: C 62.72, N 4.53, H 3.72%. Found: C 60.97, N 4.34, H, 4.30%. IR (KBr disk): 3446 (m), 1670 (m), 1644 (s), 1609 (s), 1499 (w), 1397 (s), 1233 (s), 1160 (m), 967 (w), 879 (m), 781 (m), 661 (w), 628 (w), 526 (w) cm-1. X-ray Crystallography. Each single crystal (1,4-bpyvna and 1-5) was mounted on a glass fiber with grease and cooled in a liquid nitrogen stream at 298 K.

Crystallographic

measurements were made on an Agilent Xcalibur, diffractometer by using a graphitemonochromated Mo-Kα (λ = 0.71070 Å) radiation. The crystal structures were solved by direct methods and refined on F2 by full-matrix least-squares techniques with SHELXTL-97 program.80,81 For 1, the hydrogen atoms of one H3BTC molecule having O10 and one water molecule having O13 were located from Fourier maps and the O-H bonds were fixed to be 0.86 Å. For 2, C7-C16 atoms were split into two sites with an occupancy ratio of 0.47/0.53 for C7C16 and C7A-C16A. The hydroxyl O1w-H1w bond length was fixed to be 0.86 Å. For 3, the bond length of O4-H4 in the HBTC- molecule was fixed to be 0.86 Å. For 4, the bond lengths of N3-C53, N3-C54, N3-C55, C55-O12 in the DMF molecule were fixed to be 1.45 Å, 1.45 Å, 1.45 Å and 1.35 Å, respectively. This structure also contains a large void space, which may contain some solvent molecules. Attempts to locate them failed due to the weak diffraction of the crystal used.

For 5, the bond lengths of N3-C53/N3-C54/N3-C55/N4-C56/N4-C57/N4-C58/N5-

C59/N5-C60/N5-C16 and C55-O11/C58-O12/C61-O13 in the DMF molecules were fixed with to be 1.45 Å and 1.35 Å, respectively. The hydrogen atoms of the lattice water molecules in 1-4


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were not located. All other H atoms were placed in geometrically idealized positions and constrained to ride on their parent atoms. A summary of pertinent crystal data for 1,4-bpyvna and 1-5 were given in Table 1. Their selected bond lengths and angles were listed in Table S1. Table 1. Crystal Data and Structure Refinement Parameters for 1,4-bpyvna and 1-5 1,4-bpyvna

1

2

3

4

5

empirical formula

C24H18N2

C42H28N2O13Zn2

C33H18N2O8Zn2

C44H26N3O13 Zn

C53.50H43N2.50O12.75Zn2

C113H70N7O23Zn4

formula weight

334.40

899.44

701.27

872.08

1046.61

2155.32

crystal system

monoclinic

monoclinic

Triclinic

Triclinic

monoclinic

monoclinic

space group

P21/c

Cc

Pī

Pī

C2/c

Cc

a (Å)

9.9325(9)

18.9541(5)

9.384(2)

9.1427(5)

32.751(3)

14.9706(7)

b (Å)

15.1533(18)

9.6247(2)

10.045(6)

10.2057(8)

15.5441(10)

25.1996(10)

c (Å)

11.8285(9)

20.3878(5)

18.648(5)

22.0438(11)

24.2564(16)

16.1605(7)

α (deg)

90.00

90.00

80.18(4)

102.229(6)

90.00

90.00

β (deg)

102.152(8)

97.289(2)

83.53(2)

93.001(5)

103.953(8)

111.367(5)

γ (deg)

90.00

90.00

66.86(4)

102.352(6)

90.00

90.00

V (Å3)

1740.4(3)

3689.24(15)

1590.7(11)

1953.4(2)

11984.1(15)

5677.6(4)

ρcalc (g cm-3)

1.276

1.619

1.464

1.483

1.160

1.261

Z

4

4

2

2

8

2

µ (mm–1)

0.075

1.375

1.560

0.703

0.856

0.904

F(000)

704.0

1832

708.0

894

4276.0

2202

R 1a

0.0617

0.0301

0.0571

0.0575

0.0892

0.0489

0.1206

0.0643

0.1637

0.1412

0.2380

0.1336

0.895

0.843

1.074

0.847

1.054

0.892

wR2

b

GOF a

c

R1 = Σ||Fo|-|Fc||/Σ|Fo|. bwR2 = {Σw(Fo2-Fc2)2/Σw(Fo2)2}1/2. cGOF = {Σw((Fo2-Fc2)2)/(n-p)}1/2, where n =

number of reflections and p = total number of parameters refined.

RESULTS AND DISCUSSION


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Synthesis and Structural Characterization of 1,4-bpyvna and 1-5. Reaction of pyridine-4carbaldehyde

with

tetraethyl(naphthalene-1,4-diylbis(methylene))bis(phosphonate)

in

the

presence of tBuOK afforded 1,4-bpyvna (Figures S1 and S2).82 In our case, 1,4-bpyvna was readily prepared by the Heck cross-coupling reaction of 4-vinylpyridine with 1,4dibromonaphthalene in 93% yield. Reaction of Zn(NO3)2·6H2O with 1,4-bpyvna and 1,3,5H3BTC (molar ratio = 1 : 1 : 1) in CH3CN/H2O (v/v = 1:2) at 120 ºC afforded a threedimensional (3D) coordination polymer 1 in 37% yield. In this solvothermal reaction, two of three COOH groups of 1,3,5-H3BTC were in situ deprotonated into a carboxylate group, forming 1,3,5-HBTC2- ion.83,84 Attempts to carry out the same reactions at lower (100 ºC) or higher (140 ºC) temperatures always resulted in the formation of an unidentified precipitate that was insoluble in common solvents. Addition of 0.5 mL DMF into the reaction system at 120 ºC produced several crystals of a 3D coordination polymer 2 and a large amount of yellow precipitate. When the same reaction was raised to 140 ºC, the yield of 2 was raised up to 72%. Changing the molar ratio of Zn(NO3)2·6H2O/1,4-bpyvna/1,3,5-H3BTC to 1 : 1 : 2 generated a one-dimensional (1D) coordination polymer 3 in 70% yield. In this reaction, 1,4-bpyvna ligand was protonated into a [1,4-bpyvna-H2]2+ dication. The molar ratios of the three components, solvents and reaction temperatures seemed all exert their impacts on the coordination modes of 1,4-bpyvna, 1,3,5-HBTC and the formation of 1-3. As discussed below, each 1,4-bpyvna works as either a monodentate (1) or a bidentate (2) ligand. The in situ formed [1,4-bpyvna-H2]2+ in 3 serves as a counter cation. Each 1,3,5-HBTC adopts µ4-κ2O,O':κ1O'':κ1O''' (1 and 2), µ3κ2O,O':κ1O'' (1), µ-κ1O:κ1O' and monodentate coordination modes (3). On the other hand, solvothermal reactions of Zn(NO3)2·6H2O with equimolar 1,4-bpyvna and one equiv. of 4,4’H2OBA in DMF/CH3CN/hexane at 120 ºC gave rise to one 3D coordination polymer 4 in 73%


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yield. While analogous reaction of Zn(NO3)2·6H2O with equimolar 1,4-bpyvna and two equiv of 4,4’-H2OBA at 120 ºC formed yellow blocks of 5 in 69% yield. The molar ratios of these three components decided on the formation of 4 and 5. Each 4,4’-OBA takes either µ4-κ2O,O':κ2O'',O''' (4 and 5) or µ3-κ2O,O':κ2O'',O''' (5) coordination mode to bind at three or four Zn centers. Each 1,4-bpyvna in 4 or 5 bridges two Zn(II) centers. Compounds 1-5 are stable toward oxygen and moisture. They are insoluble in common organic solvents such as DMF, DMSO, CH2Cl2, toluene, hexane, MeOH, Et2O and H2O. Their elemental analyses are consistent with their chemical formula. In the IR spectra of 1-5, the bands at 1610 cm-1 (1), 1610 and 1722 cm-1 (2), 1613 and 1685 cm-1 (3), 1643 and 1671 cm-1 (4), 1644 and 1670 cm-1 (5) are attributed to the stretching vibrations of the carboxyl groups. Each peak at 3423 (1), 3412 (2) or 3446 cm-1 (5) is attributed to the O-H stretching vibration of H2O. Bands at 1575, 1435 and 1374 cm-1 (1), 1504, 1435 and 1376 cm-1 (2), 1579, 1435 and 1367 cm-1 (3), 1610, 1499 and 1394 cm-1 (4), 1609, 1499 and 1397 cm-1 (5) are assigned to the stretching vibrations of -C=C- and –C=N-bonds. The powder X-ray diffraction (PXRD) patterns for each compound match well with those simulated from the corresponding single crystal data, suggesting its bulk phase homogeneity (Figure S3). To examine the thermal stability of 1-5, TGA analyses were carried out under a N2 atmosphere with a heating rate of 5 °C min-1 from ambient temperature up to 800°C. As shown in the TGA curves of 2-5 (Figure S4), the weight loss of 2.6% (2), 6.1% (3) , 16.3% (4) and 10.16% (5) in the range of 30-200 °C was ascribed to the removal of all lattice solvent molecules. The overall framework of 1-5 were all stable until 315-346 °C after which they quickly got collapsed. Crystal Structure of 1. As shown in Figure 1a, Zn1 adopts a square pyramidal coordination geometry coordinated by four atoms of four 1,3,5-HBTC2- and one N atom from 1,4-bpyvna.


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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


While Zn2 is tetrahedrally coordinated with four O atoms from three 1,3,5-HBTC2- ligands and one H2O molecule. The Zn–O bond lengths (1.9211(3)–2.1029(3) Å) are compared with those observed in {[Zn4(bpta)2(4-pna)2(H2O)2]·4DMF·3H2O}n (1.93(2)-2.20(2) Å, 4-pna = N-(4pyridyl)-isonicotinamide, H4bpta = 1,1’-biphenyl-2,2’,6,6’-tetracarboxylic acid).85 The mean ZnN

distance

(2.087(4)

Å)

is

slightly

pna)2(H2O)2]·4DMF·3H2O}n (2.09(3) Å).

shorter

than

that

found

in

{[Zn4(bpta)2(4-

Each 1,3,5-HBTC ligand in 1 takes a µ4-

κ1O,κ1O':κ1O'':κ1O''' or µ3-κ1O,κ1O':κ1O'' coordination mode to bind at four or three Zn centers. In 1, two [Zn(H2O)(1,3,5-HBTC)] and [Zn(1,4-bpyvna)(1,3,5-HBTC)2] fragments are linked by a couple of 1,3,5-HBTC ligands to form a dinuclear Zn2 unit [Zn2(1,4-bpyvna)(1,3,5HBTC)2(H2O)] with a Zn1···Zn2 separation of 3.4004 Å. Such “Zn2(COO)2’’ eight membered rings are interlinked to adjacent ones by 1,3,5-HBTC ligands, forming a 2D layer structure extending along the bc plane (Figure 1b). Each layer is further connected to its equivalent ones by 1,3,5-HBTC ligands to give a 3D net (Figure 1c). If 1,3,5-HBTC and a dinuclear Zn2 unit are considered as 3- and 5-connecting nodes, respectively, 1 holds a 3D (3,5)-connected topological structure with a {3·52}{32·53·64·7} Schläfli symbol.

(a)

(b)


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(c) Figure 1. (a) View of the coordination environments of the Zn centers in 1 with a labeling scheme. (b) View of the 2D network composed of Zn2+ and 1,3,5-HBTC in 1 extending along the bc palne (c) View of the 3D structure of 1 looking along the b axis.

Crystal Structure of 2. As presented in Figure 2a, Zn1 is tetrahedrally coordinated by one N atom from 1,4-bpyvna, two O atoms from two BTC3- ligands and one µ3-OH- ion. The trigonalbipyramidal coordination sphere of Zn2 is composed of one N atom from 1,4-bpyvna and four O atoms from two BTC3- ligands and two µ3-OH groups. The Zn–O bond lengths related to the carboxylate or µ3-OH group are within the range of 1.9218(5)–2.0137(5) Å and 1.9581(5)– 2.2004(5) Å, which are close to those found in 1. For each 1,3,5-BTC in 2, one carboxylate group takes a bridging bidentate mode, while the other works as a monodentate mode. Four Zn(II) atoms in 2 are bridged by two µ3-OH to form a chair-like [Zn4(OH)2] unit. Such a unit is connected to its equivalent ones by 1,3,5-BTC3- ligands to give a 2D network extending along


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the ab plane (Figure 2b). Each 1,4-bpyvna acts as a pillar to link the adjacent 2D layers via its coordination at Zn centers, thereby forming a 3D net (Figure 2c).

(a)

(b)

(c) Figure 2. (a) View of the coordination environments of the Zn centres in 2 with a labeling scheme. (b) View of the 2D network of 2 extending along the ab plane (c) View of the 3D framework of 2 looking along the a axis. Crystal Structure of 3. Figure 3a shows that each Zn(II) in 3 is tetrahedrally coordinated by three O atoms from three 1,3,5-HBTC2- ligands and one H2O molecule. One 1,3,5-HBTC in 3


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takes a µ-κ1O,κ1O' bridging coordination mode while the other works as a monodentate mode. The Zn–O bond lengths (1.9568(3)–1.9927(4) Å) are shorter than those observed in 1 and 2. Compound 3 has a 1D anionic chain propagated along the b axis in which each [Zn(1,3,5HBTC)(H2O)] unit is bridged by µ-1,3,5-HBTC ligands (Figure 3a).

(a)

(b)

Figure 3. (a) View of a section of the 1D anionic chain in 3 with a labeling scheme. (b) View of the part of the 1D H-bonded staircase chain formed via the hydrogen bonding interaction between CO2- and COOH groups in 3.

Each chain is linked to its equivalent one by two H-bonding interactions between CO2- and COOH groups (O4–H4···O3) and (O12–H12···O9) to form a 1D H-bonded staircase chain (Figure 3b). The hydrogen bonds result in one type of windows with their dimensions being 10.2 Å × 18.7 Å. Within the network, [1,4-bpyvna-H2]2+ are accommodated by two different Hbonding interactions between [1,4-bpyvna-H2]2+ and CO2- groups (N1–H1A···O2) and (N2– H2A···O5) (Figure S5a). The 1D H-bonded staircase chains are further linked by one H-


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bonding interactions between CO2- and COOH groups (O12–H12···O9) to form a 2D H-bonded layer network (Figure S5b). Different layers can be extended into form a 3D network by two different face to face π-π interactions (3.855 Å) between 1,3,5-HBTC ligands (Figure S5c). Crystal Structure of 4. Figure 4a displays that two carboxylate groups of 4,4’-OBA in 4 bind to three Zn(II) atoms through a chelating bidentate fashion and a bridging bidentate mode or bind to four Zn(II) atoms via a bridging bidentate mode. Zn1 is coordinated with one N atom from 1,4-bpyvna, four O atoms from four 4,4’-OBA ligands, forming a tetragonal pyramid coordination geometry. Zn2 adopts a distorted trigonal-bipyramidal geometry, coordinated by one N atom from 1,4-bpyvna and four O atoms from three 4,4’-OBA ligands. The Zn-O2 bond length (2.4679(6) Å) is much longer than those of the others (1.9510(6)-2.0698(6)Å) while the Zn-N bond distance (2.029 Å) is shorter than those found in 1 and 2. In 4, Zn1 and Zn1A form a dinuclear paddle-wheel shaped unit, juxtaposed by four bridging carboxylates from four µ4-4,4’OBA ligands. Such units are interlinked by µ4-4,4’-OBA ligands to form a 2D (4,4) network extending along the bc plane (Figure 4b). Meanwhile, Zn2 and Zn2A has a dinuclear ring unit assembled by two bridging carboxylates and two chelating carboxylates from four µ3-4,4’-OBA ligands. These dinuclear units are interconnented by µ3-4,4’-OBA ligands to yield another 2D (4,4) network spreading along the bc plane (Figure 4c). Both 2D networks are alternatively bridged by 1,4-bpyvna to form a 3D framework (Figure 4d).


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(a)

Page 16 of 37

(b)

(c)

(d)

Figure 4. (a) View of the coordination environments of the Zn centers in 4 with a labeling scheme. (b) View of the 2D network of 4 assembled by Zn1 and µ4-4,4’-OBA ligands in 4. (c) View of the 2D network formed by Zn2 and µ3-4,4’-OBA ligands in 4.

(d) View of the 3D

structure of 4.

Crystal Structure of 5. Figure 5a illustrates that two carboxylate groups of each 4,4’-OBA in 5 exhibit a chelating bidentate fashion and a bridging bidentate mode, respectively. Zn1 and Zn2


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adopt a distorted trigonal-bipyramidal geometry completed by one N atom from 1,4-bpyvna and four O atoms from three 4,4’-OBA ligands. The Zn–O(cheating) bond lengths (2.0025(6) Å2.3594(6) Å) are longer than those of the Zn–O(bridging) bonds (1.9648(6) Å-2.0001(6) Å). The mean Zn-N bond length (2.053(4) Å) is comparable to that in 4. Two Zn atoms are coordinated by two 4,4’-OBA ligands to generate a binuclear [Zn2(4,4’-OBA)2] ring. Such a ring is linked to its equivalent ones by a pair of 4,4’-OBA ligands, forming a 2D network extending along the ab plane (Figure 5b). Each 1,4-bpyvna connects the adjacent 2D layers to afford a 3D net (Figure 5c). Two equivalent nets are further interpenetrated to afford a two-fold interpenetrated 3D structure (Figure 5d).

(a)

(b)

(c)

(d)


17


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Figure 5. (a) View of the coordination environment of the Zn center in 5 with a labelling scheme. (b) View of a 2D network in 5 extending along the ab plane. (c) View of the 3D framework of 5. (d) Schematic view of the two-fold interpenetrated 3D topological structure of 5.

Hg2+ Luminescent Sensing Properties of 1,4-bpyvna. The sensing of metal ions (Mn+) by 1,4-bpyvna was primarily explored by the UV-vis absorption spectra. The experiment was carried out in a DMF 1,4-bpyvna solution (1 × 10-5 mol L-1) as the probe. Without the addition of Mn+, the absorption spectrum of 1,4-bpyvna was characterized by two intense bands centered at 275 nm and 370 nm (Figure 6a), which are likely due to the intraligand π→π* or n→π* transitions.58,86 When equomolar metal ion such as Na+, Ag+, Ba2+, Mn2+, Cd2+, Co2+, Ni2+ or Cu2+ was added into the DMF solution of 1,4-bpyvna, almost no change in the absorption spectra was observed. Upon addition of Hg2+, however, the intensity of the absorption at 275 nm was greatly enhanced while the absorption at 370 nm was red-shifted to 398 nm (Figure 6b). The addition of Hg2+ into the DMF solution of 1,4-bpyvna led to the visual color change from colourless to pale yellow, which was identified easily by our eyes (Figure 6c). The distinct colour change suggests that 1,4-bpyvna could be used as a sensitive naked-eye colorimetric chemoprobe for sensing Hg2+ ions.


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(a)

(b)

(c)

Figure 6. (a) Absorbance spectra of 1,4-bpyvna (1 × 10-5 mol L-1) in DMF solution upon addition of different metal ions. (b) Absorbance spectra of the DMF solution of 1,4-bpyvna (1 × 10-5 mol L-1) upon addition of different concentrations of Hg2+. (c) The colors of the solutions containing 1,4-bpyvna with different metal ions.

Luminescence spectroscopic analysis was also carried out to examine the sensing property of 1,4-bpyvna as a chemoprobe. Upon excitation at 392 nm, the DMF solution of 1,4-bpyvna in the absence of metal ions displayed one fluorescence band at λmax = 446 nm and another emission band at λmax = 471 nm. Addition of Na+, Ag+, Ba2+, Mn2+, Cd2+, Co2+, Ni2+, Cu2+ slightly


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decreased the luminescence intensity without significant change in emission wavelength (Figure 7a). When Hg2+ ion was added into the DMF solution of 1,4-bpyvna, the original emission was quenched concurrent with a new small peak at ca. λmax = 510 nm. Correspondingly, in the presence of Hg2+ ions, the color of the 1,4-bpyvna solution changed from blue to yellow, which could be easily distinguished by eyes (Figure 7b). The drastic color change indicates that 1,4bpyvna can also be applied as a sensitive naked-eye luminescent probe for sensing Hg2+ ions. As shown in Figure 7c, the original emission of 1,4-bpyvna at λmax = 446 nm was gradually quenched with increasing addition of Hg2+ (from 0 to 0.1 ppm). The fluorescence quenching efficiency was intimately dependent on the concentration of Hg2+ and can also be analyzed using the Stern−Volmer equation: I/I0 = 1 + Ksv[Hg2+] (where I0 and I are the fluorescence intensities of different sensors in the absence and presence of Hg2+, respectively. [Hg2+] is the molar concentration of Hg2+, and KSV is the Stern–Volmer quenching constant). The calibration curve displayed a good linear relationship (R2 = 0.99601) of I/I0 versus [Hg2+] over the range from 0.004 to 0.014 ppm, accompanied by a KSV = 3.03 × 106 L mol-1 (Figure S6a) The limit of detection (LOD) of 1,4-bpyvna for Hg2+ detection, based on the definition by IUPAC criteria (3σ/slope, where σ is the standard deviation of the fluorescence intensity in the absence of metal ions), was calculated to be 0.060 ppm. This value went in-between that reported for 2,3-bis(4(3-(4-(dimethylamino)phenylallylidene)-amino)phenyl)-6,13-pentacenequinone (0.500 ppm),87 and those observed for 1,4-bis[2-(4-pyridyl)ethenyl]benzene (0.080 ppm)51 and azadipyrromethene boron difluride (0.120 ppm).88 Interference upon the addition of Na+, Ag+, Ba2+, Mn2+, Cd2+, Co2+, Ni2+, Cu2+ (with the same concentration as Hg2+) was negligible, implying that 1,4-bpyvna exhibited excellent selectivity towards Hg2+ sensing (Figure 7d).


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(a)

(b)

(c)

(d)

Figure 7. (a) Emission spectra of 1,4-bpyvna (1 × 10-5 mmol L-1 ) upon addition of different metal ions (0.06 ppm) in DMF. Excitation wavelength was 392 nm. (b) Colours of the solutions containing 1,4-bpyvna with different metal ions under UV light. (c) Emission spectra of 1,4bpyvna (1 × 10-5 mmol L-1 ) in the presence of increasing Hg2+ concentrations (0~0.1 ppm) in DMF. Excitation wavelength was 392 nm. (d) Fluorescence intensities of 1,4-bpyvna dissolved in the DMF solution of metal ion (blue color) or mixed Hg2+ and metal ions (red color) under an excitation of 392 nm.


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Figure 8. 1H NMR titration of 1,4-bpyvna with Hg(NO3)2 in DMSO-d6 solution.

Attempts to obtain more detailed information on the binding properties of 1,4-bpyvna with Hg2+ ion by 1H NMR titration were performed in DMSO-d6. Stacked spectra recorded for 1,4bpyvna in the presence of increasing Hg2+ (0-5 equiv.) concentrations were presented in Figure 8. Addition of Hg2+ caused a significant downfield shift for the signals of the protons (H1, H2) of the pyridyl ring from δ 8.59/7.76 to 8.84/8.20, suggesting that the N atoms of 1,4-bpyvna were involved in the coordination at Hg2+. The chemical shift of the protons (H3, H4, H6, and H7) on the vinyl and naphthalene groups underwent a downfield shift from δ 7.35, 8.39, 8.53, 7.66 to 7.65, 8.75, 8.65, 7.75 ppm, respectively. The changes in the 1H NMR spectra upon titration with Hg2+ demonstrated that saturation of the change in chemical shift for 1,4-bpyvna protons took place when 2 equiv. of Hg2+ ion was added, implying a 1 : 2 stoichiometry of the compound between 1,4-bpyvna and Hg2+ ion. The coordination of Hg2+ ions led to a downfield chemical shift of the protons of the pyridine rings, vinyl groups in 1,4-bpyvna. These results verified that


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Hg2+ interacted with the N atom on 1,4-bpyvna, which resulted in the intramolecular charge transfer and the emission quenching at λmax = 446 nm.58,89 Hg2+ Luminescent Sensing Properties of 2. The above-mentioned finding that 1,4-bpyvna can serve as a luminescent sensor for probing low-concentration Hg2+ activated us to further explore the sensing ability of the coordination polymers 1−5.

Firstly, we examined the

photoluminescent properties of 1−5 suspended in DMF (Figure 9). When excited at 398 nm (1, 2 and 3) or 341 nm (4), 390 nm (5), compounds 1-5 displayed similar emission bands with maxima at 444 and 472 nm (1, 3 and 4), 442 nm and 467nm (2), 441 and 477 nm (5). Their emission bands can be assigned to a ligand-centered emission. The emission maxima of 1−5 was red-shifted, which was probably due to the coordination between 1,4-bpyvna and Zn(II).

Figure 9. Emission spectra of 1-5 dispersed in DMF at ambient temperature. Next, we took 2 as a representative example to study its potential as a luminescent sensor for the detection of Hg2+ ion. Finely-ground sample of 2 (1 mg) was soaked in a DMF (2 mL) solution of 1 mmol L-1 M(NO3)n (M = Na+, Ba2+, Ag+, Mn2+, Cd2+, Co2+, Ni2+, Cu2+ and Hg2+) to give a Mn+-incorporated suspension of 2 for the luminescence measurement. Figure 10a showed the emission spectral change of the DMF solution of 2 upon addition of Mn+ ions. When


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immersed in an aqueous solution of Na+, Ba2+, Ag+, Mn2+, Cd2+, Co2+, Ni2+ or Cu2+ ion, the emission maxima of similar intensity were observed at 444 and 472 nm, upon excitation 398 nm. The resultant blue fluorescence of 2 showed no significant variation in color with these metal ions (Figure 10b). When Hg2+ was added into the DMF solution of 2, the original emission at 444 and 472 nm was quenched concurrent with the growth of a new and broad peak at 520 nm. The large emission red-shift led to a change of fluorescence color from blue to yellow (Figure 10b). These results suggested that 2 could serve as a sensitive naked-eye fluorescent sensor for detecting Hg2+ ion under UV light. To assess the sensitivity of 2 toward Hg2+ in detail, different concentrations of Hg2+ were introduced into emulsions of 2 dispersed in DMF and the emissive responses were monitored.

The fluorescence spectra of 2 displayed a gradual decrease in

fluorescence with increasing Hg2+ concentrations (Figure 10c). When the Hg2+ concentration reached 0.08 ppm, the quenching efficiency of 2 in fluorescence intensity could be raised up to 92.06%. The linear relationship of the value of (I0 - I)/I0 versus Hg2+ concentration, as shown in the inset of Figure 10c, was from 0 to 0.018 ppm (R2 = 0.990). The quenching constant Ksv of 2 is 3.23 × 106 L mol-1. For 2, its detection limit of Hg2+ was estimated to be 0.057 ppm, which is comparable to those of [(pbi)2Ir(mtpy)] (0.050 ppm; pbi = 1,2-diphenyl-1H-benzo[d]imidazole, Hmtpy = 3-methyl-5-phenyl-1H-1,2,4-triazole),90 and Eu3+/CDs@MOF-253 (0.013 ppm; CDs = carbon dots, MOF-253 = [Al(OH)(bpydc)], H2bpydc=2,2’-bipyridine-5,5’-dicarboxylic acid).91 The high selectivity of 2 for Hg2+ ion was further examined by the anti-interference sensing experiments. 2 (1 mg) was immersed in a DMF solution containing mixed Hg2+ ion (0.1 ppm) and equimolar Mn+ ion (Na+, Mn2+, Ni2+, Ba2+, Co2+ ,Cd2+, Ag+, Pb2+ or Cu2+). The addition of each ion into the DMF solution of 2 did not afford a new emission band but only resulted in a slight decrease in fluorescence intensity. The emission was quenched after further addition of


24

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Hg2+ ion, verifying that 2 possessed the highly selective Hg2+ sensing performance even in the presence of several other metal ions (Figure 10d).

(a)

(b)

(c)

(d)

Figure 10. (a) Emission spectra of 2 in DMF in the absence/presence of Mn+ ions. (b) The colors of the suspensions of 2 with different metal ions under UV light. (c) Emission spectra of 2 in the presence of increasing Hg2+ concentrations (0~0.08 ppm) in DMF. Inset: linear relation between the quenching efficiency and the concentration of Hg2+ in the range of 0~0.018 ppm. (d) Fluorescence intensities of 2 immersed in the DMF solution of metal ion (blue color) or mixed Hg2+ and metal ions (red color) under an excitation of 389 nm.


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To investigate the response rate of this fluorescent probe to the analyte, the kinetic characteristics for Hg2+ sensing was measured at different time intervals (Figure 11a). Upon the addition of Hg2+, the fluorescent intensity of 2 started to decrease immediately and reached a minimum value and stability after 100 seconds, suggesting that the reaction was almost complete. As we know, recyclability is vital to detect Hg2+ with high sensitivity and selectivity. The PXRD patterns of 2 after immersing into the DMF solution containing Hg2+ ion for several hours confirmed that the original framework structure was retained (Figure S7). Complex 2 can be regenerated by centrifugation of the solution after use and washing several times with DMF and H2O. The initial fluorescence intensity did not decrease significantly even after six cycles (Figure 11b), which demonstrated that 2 was an excellent luminescent probe for sensing lowconcentration Hg2+.

(a)

(b)

Figure 11. (a) Effects of response time on the fluorescent intensities upon the addition of Hg2+ into the suspension of 2. The concentrations of Hg2+ were fixed to be 0 ppm (a), 0.03 ppm (b) and 0.1 ppm (c). (b) Recycling tests of 2 for quenching efficiencies using Hg2+ under UV light.


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CONCLUSIONS

In the work reported here, we have demonstrated the synthesis of one 1D coordination polymer (3) and four 3D coordination polymers (1, 2, 4, 5) from reactions of Zn(NO3)2 with 1,4-bpyvna and 1,3,5-H3BTC or 4,4’-H2OBA under different solvothermal conditions. The coordination modes of 1,3,5-H3BTC, 4,4’-H2OBA or 1,4-bpyvna ligands, the coordination geometries of Zn(II) centers, and the structures of the resulting coordination polymers were affected by the molar ratios of the reactants, reaction temperatures and solvent systems. In the structures of 1-5, 1,4bpyvna presents two coordination modes: monodentate (1) and µ-κ1N:κ2N’ bridging (2, 4 and 5) modes. In 3, 1,4-bpyvna was in situ protonated as a [1,4-bpyvna-H2]2+ counter dication. Ligand 1,3,5-HBTC adopts three bridging modes (µ4-κ2O,O':κ1O'':κ1O''' (1 and 2), µ3-κ2O,O':κ1O'' (1), µκ1O:κ1O') and one monodentate mode (3). Ligand 4,4’-OBA takes either a µ4-κ2O,O':κ2O'',O''' (4 and 5) or a µ3-κ2O,O':κ2O'',O''' (5) coordination mode. Zinc centers hold a tetrahedral (1, 2, 3), a square pyramidal (1), a trigonal-bipyramidal (2, 4, 5) or a tetragonal pyramid (4) coordination geometry. Ligand 1,4-bpyvna and the representative complex 2 can be used for the “nakedeye” detection of low-concentration Hg2+ with high selectivity and sensitivity. For 1,4-bpyvna, both the color and changes of luminescent emission show quite specific for Hg2+. The color of the 1,4-bpyvna solution in DMF goes from colorless to yellow upon incremental addition of Hg2+ ion and its detection limit of Hg2+ reaches 0.060 ppm. The emission maximum of 1,4-bpyvna is red-shifted with addition of Hg2+, which drives a color change from blue to yellow under UV light. The addition of Hg2+ into the solution of 2 dispersed in DMF provokes a fluorescent color change from blue to yellow. The perceptible change in the fluorescence color can be discerned by naked eyes under UV light. The detection limit of Hg2+ using 2 remains as low as 0.057 ppm even after six cycles. Thus compound 2 can be employed as an excellent recyclable luminescent


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probe for the real-time sensing of Hg2+. We anticipate that the luminescent coordination polymers of multi-pyridine derivatives with larger π-conjugated spacers could be rationally designed and prepared and worked as practical highly-responsive sensors for the detection of low-concentration toxic metal ions and nitroaromatic compounds in water systems. ASSOCIATED CONTENT Supporting Information The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.cgd.xxxxxxx. The 1H and 13C NMR spectra of 1,4-bpyvna, the PXRD patterns and TGA curves of 1-5, and their selected bond distances and angles (PDF). Accession Codes CCDC 1544024, 1544025, 1544026, 1544027, 1544028, and 1544029 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, or by emailing [email protected], or by contacting The Cambridge Crystallographic Data Centre, 12, Union Road, Cambridge CB2 1EZ, UK; fax: +44 1223 336033. AUTHOR INFORMATION Corresponding Authors * (H.-X. Li) E-mail: [email protected]. Tel: 86-512-65883569 * (J.-P.L.) E-mail: [email protected]. Fax: +86-512-65880328. Tel: 86-512-65882865


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Notes The authors declare no competing financial interest. ACKNOWLEDGMENTS This work is financially supported by the National Natural Science Foundation of China (Grant Nos. 21373142, 21471108 and 21531006), the State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences (2015kf-07), and the State and Local Joint Engineering Laboratory for Novel Functional Polymeric Materials. J.-P. L. is grateful to the funds from the Priority Academic Program Development of Jiangsu Higher Education Institutions and the “SooChow Scholar” Program of Soochow University. M.M. C. thanks the Innovative Research Program for Postgraduates in Universities of Jiangsu Province (KYZZ16_0083). The authors are grateful to the useful comments of the editor and the reviewers. REFERENCES (1) Salinas, Y.; Martinez-Manez, R.; Marcos, M. D.; Sancenon, F.; Castero, A. M.; Parra, M.; Gil, S. Chem. Soc. Rev. 2012, 41, 1261–1296. (2) Wolfe, M. F.; Schwarzbach, S.; Sulaiman, R. A. Environ. Toxicol. Chem. 1998, 17, 146– 160. (3) Onyido, I.; Norris, A. R.; Buncel, E. Chem. Rev. 2004, 104, 5911–5930. (4) Laxmeshwar, L. S.; Jadhav, M. S.; Akki, J. F.; Raikar, P.; Kumar, J.; Prakash, O.; Raikar, U. S. Opt. Laser Technol. 2017, 91, 27–31. (5) Rahman, L.; Corns, W. T.; Bryce, D. W.; Stockwell, P. B. Talanta 2000, 52, 833–843. (6) Wang, C. C.; Li, H. G.; Wang, N.; Li, H. D.; Fang, L. P.; Dong, Z.; Du, H. X.; Guan, S.; Zhu, Q.; Chen, Z. L.; Yang, G. S. Anal. Methods 2017, 9, 634–642.


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For Table of Contents Use Only

1,4-Bis(2-(pyridin-4-yl)vinyl)naphthalene

and

its

Zinc(II)

Coordination

Polymers: Synthesis, Structural Characterization and Luminescent Selective Sensing of Mercury(II) ion

Wu-Xiang Li,† Hong-Xi Li,*,† Hai-Yan Li,† Min-Min Chen,† Yi-Xiang Shi,† Jian-Ping Lang*,†,‡

Solvothermal reactions of Zn(NO3)2·6H2O with 1,4-bis(2-(pyridin-4-yl)vinyl)naphthalene (1,4bpyvna) and two different carboxylic acids produces five Zn(II) coordination polymers with different structures. The ligand 1,4-bpyvna and one representative coordination polymer {[Zn2(1,4-bpyvna)(1,3,5-BTC)(OH)]·H2O}n can work as unique luminescent sensors for probing Hg(II) ions with high selectivity and sensitivity.


37

naphthalene and Its Zinc(II) Coordination Polymers ... - ACS Publications

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