Luminescent 2D + 2D â 2D Interpenetrated Zn(II)-Coordination

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Luminescent 2D+2D#2D interpenetrated Zn(II)-coordination polymer based on reduced Schiff base tricarboxylic acid and bis(imidazole) ligand for detection of picric acid and Fe3+ ions Mürsel Arici Cryst. Growth Des., Just Accepted Manuscript • DOI: 10.1021/acs.cgd.7b01024 • Publication Date (Web): 19 Sep 2017 Downloaded from http://pubs.acs.org on September 20, 2017

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Crystal Growth & Design

Luminescent 2D+2D→2D interpenetrated Zn(II)-coordination polymer based on reduced Schiff base tricarboxylic acid and bis(imidazole) ligand for detection of picric acid and Fe3+ ions Mürsel Arici Department of Chemistry, Faculty of Arts and Sciences, Eskişehir Osmangazi University, 26480 Eskişehir, Turkey

ABSTRACT: New bifunctional luminescent coordination polymer, formulated as {[Zn(µHCIP)(µ-pbix)]·2H2O}n (1) (H3CIP= 5-(4-carboxybenzylamino)isophthalic acid, pbix: 1,4bis(imidazol-1ylmethyl)benzene) was synthesized under solvothermal conditions by using reduced Schiff base and neutral pbix ligands and characterized by IR spectroscopy, elemental analysis, single-crystal and powder X-ray diffractions and thermal analysis. X-ray result indicated that HCIP ligand acted as a bidentate bridging ligand and was partly deprotonated in 1. Complex 1 exhibited 2D+2D→2D interpenetrated structure with sql topology. Complex 1 displayed high emission at the solid state. Luminescence titration experiments showed that complex 1 dispersed in DMF detected the picric acid in the presence of other interfering nitroaromatic compounds with a detection limit of 56.46 ppb. In addition, complex 1 displayed highly sensitive and selective detection towards Fe3+ ion in the presence of other interfering metal ions. The detection limit of 1 for Fe3+ ion sensing in DMF suspension was 0.208 ppm. The result showed that complex 1 could be used as a fluorescent sensor for the detection of picric acid and Fe3+ ion. Keywords: Coordination polymer; reduced Schiff base; fluorescent sensor; picric acid, Fe3+ ion detection.

1 ACS Paragon Plus Environment


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1. INTRODUCTION The design and synthesis of coordination polymers have been attracted interest due to their

fascinating

architectures

and

potential

application

areas

including

gas

adsorption/separation, catalysis, magnetism, luminescence, sensor, etc1-6. Especially, luminescent coordination polymers have attracted increasing attention as chemosensors for the sensitive and selective detection of some organic small molecules, metal ions and explosives etc., through the quenching or enhancing of their emission7-11. In recent years, a lot of luminescent coordination polymers have been synthesized to detect the nitroaromatic compounds because of their explosive natures and toxic pollutants10,

12, 13

. Nitroaromatic

compounds such as nitrobenzene, 1,3-dinitrobenzene, 2,4-dinitrotolune, 2,6-dinitrotoluene, 2,4,6-trinitrotoluene and picric acid (2,4,6-trinitrophenol) are the secondary explosives and environmentally toxic14,

15

. Among the nitroaromatic compounds, picric acid is highly

explosive and also gives rise to health problems to human due to its toxic effect16-19. Hence, sensitive and selective detection of picric acid is curicial for human health and security. Moreover, rapid selective and sensitive detection of Fe3+ ion draw great interest due to fact that Fe3+ ion plays vital role in biological systems and its high and low concentrations cause serious health problems to human13, 16, 20. In the construction of coordination polymers for the above applications, polycarboxylic acid and N-donor ligands have been widely chosen as building blocks. In this study, flexible 5-(4-carboxybenzylamino)isophthalic acid (H3CIP), reduced Schiff base ligand, was utilized as an anionic ligand. It displays diverse coordination modes with three carboxylate groups and partial or complete deprotonation of these groups have been observed

in reaction1,

12

.

Moreover, flexible 1,4-bis(imidazol-1ylmethyl)benzene (pbix) was used as a N-donor secondary ligand. Its imidazole rings could freely rotate around the -CH2- groups to meet the requirements of the coordination geometries of the metal ions21. Then, a bifunctional highly


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luminescent

Zn(II)-coordination

polymer,

{[Zn(µ-HCIP)(µ-pbix)]·2H2O}n

(1)

was

synthesized with H3CIP and neutral pbix for the selective and sensitive detections of picric acid (PA) and Fe3+ ion. The complex was characterized by elemental analysis, IR spectroscopy, single crystal and powder X-ray diffractions. Thermal and photoluminescence properties of the complex were studied. Moreover, selective and sensing properties of complex 1 were investigated in DMF for PA and Fe3+ ion in detail.

2. MATERIALS AND PHYSICAL MEASUREMENTS All commercially available chemicals were of analytical grade and used without further purification. H3CIP and pbix ligands were synthesized according to previous studies1,

15

.

Elemental analyses (CHN) were performed on a Perkin-Elmer 2400C Elemental Analyzer. Bruker Tensor 27 spectrometer device was used to record IR spectra using KBr pellet in the range of 4000−400 cm−1. Simultaneous thermal analyis curves (TG-DTA) were taken with a Perkin Elmer Diamond TG/DTA Thermal Analyzer in the temperature range 30–700 °C under static air atmosphere. Perkin-Elmer LS-55 spectrophotometer was utilized to record the photoluminescence spectra of the complex at solid state and in solution. UV-Vis spectra were recorded on a Shimadzu UV-2600 spectrophotometer in the wavelength range 200–800 nm. Energy-dispersive X-ray spectrum (EDX) analysis was carried out with Jeol JEM-1220 Electron Microscope. Powder X-ray diffraction patterns were obtained with a Panalytical Emperian X-ray diffractometer with Cu-Kα radiation (λ= 1.5406 Å). Single-crystal X-ray data of complex 1 was collected on a Bruker Smart Apex II CCD with a D8-QUEST diffractometer equipped with a graphite-monochromatic Mo-Kα radiation (λ = 0.71073 Å) at 296 K. The structure was solved by direct methods using SHELXT and refined by full-matrix least-squares on all F2 data using SHELXL in conjunction with the OLEX2 graphical user interface18,

22, 23

. All non-hydrogen atoms were refined with anisotropic parameters and

hydrogen atoms were calculated and refined with a riding model for complex 1. Mercury 3 ACS Paragon Plus Environment


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program was used for molecular graphics24. ToposPro software was utilized for topological calculations25.

2.1 Photoluminescence Experiments For the photoluminescence measurements, 3.0 mg of finely ground complex 1 was immersed in different solvents (dimethylformamide (DMF), dimethylacetamide (DMA), acetonitrile (CH3CN), water (H2O), chloroform (CHCl3), dichloromethane (CH2Cl2), ethanol (EtOH), methanol (MetOH), tetrahydrofuran (THF), nitrobenzene (NB)), ultrasonicated for 30 min and aged for three days to obtain stable suspensions. All emission spectra of the obtained suspensions were recorded at room temperature from 350 to 620 nm upon excitation at 336 nm. The fluorescence quenching efficiency was evaluated by using Stern–Volmer equation, Io/I = 1 + KSV[M], where Io is the initial luminescence intensity, I is the luminescence intensity after addition of nitroaromatic compounds or metal ions, KSV is the quenching constant and [M] is the concentration of nitroaromatic compounds or metal ions.

2.2

Synthesis of {[Zn(µ-HCIP)(µ-pbix)]·2H2O}n (1) A mixture of H3CIP (0.095 g, 0.30 mmol), pbix (0.072 g, 0.30 mmol) and

Zn(NO3)2·6H2O (0.178 g, 0.60 mmol) was stirred at 70 oC for 30 min in the mixture of H2O: DMF (8:2, mL). The mixture was placed in a 25 mL glass bottle and heated at 120 oC for 4 days, and then cooled to room temperature at a rate of 10 °C/h. The colorless crystals of 1 were obtained (yield: 0.089 g, 47.34 % based on H3CIP). Anal. Calcd. for C30H29N5O8Zn: C, 55.18; H, 4.48; N, 10.73 %. Found: C, 55.44; H, 3.98; N, 10.12 %. IR (KBr, cm–1): 3529 m, 3383 m, 3134 m, 3016 w, 2910 w, 1678 m, 1618 m, 1578 vs, 1522 m, 1416 m, 1352 s, 1275 s, 1097 m, 785 m, 731 m cm–1.


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3. RESULTS AND DISCUSSION 3.1

Synthesis and Characterization Complex 1 was synthesized by the solvothermal reaction of Zn(NO3)2·6H2O, H3CIP and

pbix ligands. It was characterized by elemental analysis, IR spectroscopy, single crystal and powder X-ray diffractions. Elemental analysis result is in good agreement with the assigned formulation. In the IR spectrum of 1, the band appearing at 3529 cm-1 is attributed to ν(O-H) stretching vibration of water molecules. The peak observed at 3383 cm-1 is due to ν(N-H) stretching vibration of reduced Schiff base ligand. Aromatic and aliphatic ν(C-H) stretching vibrations are observed in the range 3134-2910 cm-1. The band observed at 1686 cm-1 is due to asymmetric stretching vibration of H3CIP ligand with respect to carboxylate groups. The asymmetric carboxylate stretching vibration of H3CIP ligand is also observed with a little shift after conversion to 1, indicating partly deprotonation of carboxylate groups of H3CIP. In IR spectrum of 1, the asymmetric and symmetric stretching vibrations of carboxylate groups of H3CIP are observed at 1578 cm-1 and 1352 cm-1, respectively (Fig. S1).

3.1.1 Description of crystal structure Details of data collection and crystal structure determination are given in Table 1. Selected bond lengths and angles together with the hydrogen bonding geometries are collected in Tables S1. {[Zn(µ-HCIP)(µ-pbix)]·2H2O}n (1). The molecular structure of 1 with the atom numbering scheme is shown in Fig. 1. Single crystal X-ray structural analysis reveals that 1 crystallizes in the triclinic system with the space group P-1. There are one Zn(II) ion, one HCIP, two half pbix ligands and two crystal water molecules in the asymmetric unit of 1. Each Zn(II) ion adopts a distorted [ZnO2N2] tetrahedral geometry by coordinating to two carboxylate oxygen atoms from two different HCIP ligands and two nitrogen atoms from two



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different pbix ligands. The HCIP ligand which acts as a bidentate bridging ligand is partly deprotonated and bridges Zn(II) ions to generate 1D chain with a Zn···Zn distance of 9.97 Å (Fig. S2). 1D chains are linked by pbix ligands to form 1D double chains with 44–membered rings (Fig. 2). 1D double chains are further connected with other pbix ligands to generate a 2D undulated layer (Fig. S3). There are two different windows in 2D layer with dimensions of 13.672 x 9.97 Å2 and 13.237 x 9.97 Å2 based on the Zn···Zn distances. The 2D layers are interpenetrated with each other to give 2D+2D→2D interpenetrated structures (Fig. 3). Topologically, the complex is 2-fold interpenetrated 4-c uninodal net with sql topology. 2D layer are extend to 3D supramolecular framework with hydrogen bondings between carboxylate oxygen atoms of the HCIP and uncoordinated water molecules [O6-H6···O8 and O7-H7B···O5] and between N-H groups and uncoordinated carboxylate oxygen atoms of HCIP ligands [N5-H5···O5] (Fig. 4).

3.2

Powder X-ray Diffraction and Thermal Analysis Results Powder X-ray diffraction (PXRD) pattern of complex 1 was recorded to check the phase

purity of the bulk material (Fig. S4). PXRD pattern of the complex is in good agreement with the simulated pattern obtained from its single-crystal structure, indicating the phase purity of the complex. Thermal behavior of complex 1 was determined by TG/DTA analysis in temperature range of 30-700 oC under a static air atmosphere (Fig. S5). The first weight loss of 5.5 % in the temperature range of 94.30-147.4 oC is due to removal of uncoordinated water molecules (calcd.: 5.75 %). Complex 1 is stable up to 297 oC. On further heating, the framework is decomposed with exothermic picks. The final residual product is possibly ZnO (found: 13.81 %; calcd.: 12.40 %).


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3.3

Luminescence behavior and sensing properties Coordination polymers with the d10 metal centers have displayed high luminescence

behaviors and have been intensively used in sensor, photochemistry studies and optical devices. Solid state luminescence spectra of free ligand H3CIP and complex 1 were recorded under the same condition at room temperature (Fig.S6). Free ligand H3CIP showed emission at 458 upon excitation at 336 nm. This emission may be attributed to π*→π transitions1. Complex 1 displayed intense emission peak at 411 nm upon excitation at 336 nm. When compared with the photoluminescence emission of free ligand H3CIP, the emission maximum of complex 1 is blue-shifted which may be due to ligand-to-metal charge transfer (LMCT). Moreover, when compared to H3CIP, complex 1 showed high emission intensity which could be due to coordination of ligand to metal centers. Detection of Picric acid Luminescence based sensor studies of coordination polymers have been attracted interest for the detection of the small organic molecules, metal ions and nitro explosives, etc2, 8, 9, 26, 27

. Encouraged by the strong emission intensity of complex 1, luminescence behavior of

complex 1 (3.0 mg) was also investigated in different organic solvents including dimethylformamide (DMF), acetonitrile (CH3CN), dimethylacetamide (DMA), water (H2O), chloroform (CHCl3), dichloromethane (CH2Cl2), ethanol (EtOH), methanol (MetOH), tetrahydrofuran (THF), nitrobenzene (NB). As seen in Fig. 5, the luminescence intensity of complex 1 dispersed into various organic solvents highly depends on the solvent molecules, especially, in the case of NB which displays the most quenching behavior. Fluorescence quenching behavior of NB encouraged us to study detection ability of complex 1 towards the other nitroaromatic compounds. Nitrobenzene (NB), 1,3-dinitrobenzene (DNB), 2,6dinitrotoluene (DNT), 4-nitrophenol (NP), 2,4-dinitrophenol (DNP) and picric acid (PA) were



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selected for luminescence sensor studies and DMF solutions of nitroaromatic compounds (25 µL, 1.0 mM) with the incremental addition were added to complex 1 dispersed in DMF (3.0 mg / 2.70 mL) and the emission spectra of the complex were recorded to determine their quenching efficiencies (Fig. S7-12). As seen in Fig. S7-12, there are almost no quenching effects for NB, DNB and DNT while hydroxyl-substituted nitroaromatic compounds (nitrophenol derivatives) exhibit different degrees of quenching effect for complex 1 dispersed in DMF. The visual color changes of complex 1 dispersed in DMF before and after the addition of nitroaromatic derivatives under UV-light are also given in Fig. S13. Quenching efficiencies upon incremental addition of all nitroaromatic compounds (25 µL of 1.0 mM) were calculated by using the equation (I0 − I)/I0 x 100 %, where I0 and I are fluorescence intensities of complex 1 without and with the addition of the nitroaromatic derivatives16. The order of quenching efficiency is PA > DNP > NP > DNB > DNT > NB with the respective quenching efficiency values of 94.80 %, 86.88 %, 41.73 %, 5.45 %, 4.055 and 0.97 % (Fig. 6). These results indicate that complex 1 exhibits higher selective detection for hydroxyl-substituted nitroaromatic compounds. This situation can be due to hydrogen bond interactions between O-H group of nitrophenol compounds and uncoordinated carboxylic acid group of complex 115, 28-30. Among the nitrophenol derivatives, PA displays the highest quenching effect which can be assigned to three nitro group in PA14, 31, 32. Because of the highest quenching effect, to further investigate the sensing ability of complex 1 towards PA, quenching efficiency of PA was also evaluated by the Stern-Volmer (S-V) equation: I0 / I = 1 + Ksv x [M], where, I0 and I are fluorescence intensities of 1 without and with the addition of the nitroaromatic compounds; Ksv is the quenching constant; M is the molar concentration of nitroaromatic compounds17. As seen in Fig. 7, S-V plot of PA is almost linear at low concentration and becomes bent upwards at high concentration. The nonlinear SV plot for PA indicates the existence of the resonance energy transfer process2,


10, 14

. The possibility of

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energy transfer depends on spectral overlap between emission spectrum of coordination polymer and absorption spectra of nitroaromatic compounds. As seen Fig. S14, spectral overlap between absorption spectrum of PA and emission spectrum of 1 is higher in comparison with other nitrophenol derivatives, resulting in luminescence quenching and overlap is also negligible for other nitroaromatic compounds. The quenching constant (KSV) for PA is 4.37 × 104 M-1 which is comparable to reported value for some coordination polymers18, 22, 31, 33. Limit of detection (LOD) for PA is calculated at low concentrations by using the equation: LOD = 3σ / K, where σ is the standard deviation of initial intensity of complex 1; K is the slope of the above-mentioned linear curve. The detection limit of complex 1 dispersed in DMF for PA is 2.465 × 10-7 M (56.46 ppb), which is comparable with reported literatures2, 7, 12, 15, 19, 21, 32, 34-36 (Table S2). Moreover, the selective detection of PA in the presence of other interfering nitroaromatic compounds was investigated. For this purpose, nitroaromatic compound (DNP or NP or DNB or DNT or NB, 1.0 mM, 100 µL) was added to suspension of complex 1 in DMF and then the florescence spectrum was recorded. After that, PA (1.0 mM, 100 µL) solution was added to previous suspension of 1 containing interfering nitroaromatic compound and florescence spectrum was recorded again. Florescence intensity decreased after the addition of PA to the suspension of complex 1 including other nitroaromatic compounds (Fig. 8). This result showed high selectivity for PA in the presence of other interfering agents. Furthermore, the recyclability of sensor material is important factor for long-term application. In order to check the recyclability of 1 after PA detection, suspension was recovered by centrifugation and washed with DMF. The recyclability of detection performance of complex 1 towards PA was carried out up to five cycles of repetition. As seen in Fig. 9, the initial fluorescence intensity of complex 1 did not change significantly after five cycles of repetition, indicating high reusability and stability for the detection of PA. PXRD pattern of recovered complex after five cycles of repetition is in good



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agreement with as-synthesized complex, indicating the robustness of the structure (Fig. S15). Hence, complex 1 can be promising candidate for the long-term application. Detection of Fe3+ ions Luminescence coordination polymers may be also used as chemosensors for the sensitively detection of metal ions37. For the luminescence detection experiments of metal ions, DMF solutions (0.3 mL) containing diverse metal ions (0.01 M) (nitrate salts of Na+, Al3+, Cr3+, Fe3+, Co2+, Ni2+, Cu2+, Zn2+, Hg2+ and Pb2+ and chloride salt for Fe2+) were added into complex 1 (3.0 mg) dispersed in DMF (2.7 mL), respectively and the luminescence spectra of the suspensions were recorded. Luminescence spectra of the suspensions showed that luminescence intensity of 1 was changed depending on metal ions. Luminescence intensity of 1 was completely quenched in the presence of Fe3+ ions while the other metal ions had negligible effect on the emission of complex 1 (Fig. 10). These results showed that complex 1 could detect the Fe3+ ions through luminescence quenching. In order to further investigate the sensing ability of complex 1 towards Fe3+ ion, emission titration experiments were carried out with Fe3+ ions. The emission intensity of 1 dispersed in DMF decreased gradually with incremental addition of Fe3+ ions (Fig. S16). The quenching efficiency of Fe3+ was also evaluated by the Stern-Volmer (S-V) equation: I0 / I = 1 + Ksv × [M], where, I0 and I are fluorescence intensities of 1 without and with the addition of DMF solution of Fe3+ ions; Ksv is the quenching constant; M is the molar concentration of Fe3+ ions. As seen in Fig. 11, S-V plot is almost linear at low concentration and the quenching constant (KSV) is 6.87 x 103 (M-1). Moreover, the limit of detection (LOD) is calculated to be a 0.208 ppm (3.72 µM) which is comparable to some previously reported fluorescence sensors for Fe3+ ions38-42. Moreover, selective luminescence detection of Fe3+ ion was investigated in the presence of other interfering metal ions (Fig. 12). The results showed that the quenching effect of Fe3+ was not significantly affected by other interfering metal ions. The selectivity of Fe3+ ion of


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complex 1 can be assigned to electron transfer from the HCIP ligand in 1 to Fe3+ ion. As seen in crystal section, there is an uncoordinated carboxylic acid group in 1 which acts as an electron donor group. When Fe3+ ions are combined with 1, electron transfer will occur from uncoordinated carboxylate oxygen atoms (donor) to Fe3+ ions (acceptor), resulting in a decrease in the luminescence intensity43. Moreover, EDX analysis of recovered complex after Fe3+ ion sensing showed the presence of a small amount of the Fe3+ ions (Fig. S17). This result also showed that Zn(II) ions was partially replaced by Fe3+ ions or uncoordinated carboxylate group coordinated to Fe3+ ions which diminished the resonance energy transfer from HCIP to Fe3+ ions44. Moreover, PXRD pattern of recovered complex after the detection of Fe3+ ion was recorded (Fig. S17). In the PXRD pattern, some peaks were broadened and a little shifted. This result showed the interaction of complex 1 with Fe3+ ion. 4. CONCLUSIONS Zn(II)-coordination polymer with H3CIP and pbix linkers was successfully obtained by solvothermal method and characterized by various techniques. Complex 1 had 2D layers and 2D layers were interpenetrated with each other to give 2D+2D→2D interpenetrated structures with sql topology. 3D supramolecular network is generated through hydrogen bondings between carboxylate oxygen atoms of HCIP and uncoordinated water molecules and between N-H groups and uncoordinated carboxylate oxygen atoms of HCIP ligands. Complex 1 exhibited highly fluorescence emission and solvent-dependent photoluminescent emissions. Complex 1 exhibited highly sensitive and selective detection of picric acid with the detection limit of 56.46 ppb in the other nitroaromatic compounds. This can be due to electron or energy transfer processes and also hydrogen bond interactions between O-H group of PA and uncoordinated carboxylic acid group of complex 1. Recyclability experiments showed that complex 1 was highly reusable and stabile for the detection of PA. Moreover, complex 1 can sensitively and selectively detect the Fe3+ ions through luminescence quenching even in the



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presence of other competing metal ions. This can be assigned to electron transfer process from the HCIP ligand in 1 to Fe3+ ions. Supporting Information PXRD patterns, UV-Vis spectra, PL spectra, IR spectra, TG/DTA, SEM image, crystal structure and table for bond distances and angles of complex 1. Crystallographic data for the structural analysis have been deposited with the Cambridge Crystallographic Data Centre, CCDC No 1554965 for 1. Copies of this information may be obtained free of charge from the Director, CCDC, 12 Union Road, Cambridge CB2 1EZ, UK (fax:

+44-1223-336033;

e-mail:

[email protected]

http://www.ccdc.cam.ac.uk) This material is available free of charge via the Internet at http://pubs.acs.org. *Corresponding Author: E–mail: [email protected] Tel: +902222393750, Fax: +902222393578


or

www:

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Figure and Table Captions Table 1. Crystal data and structural refinement parameters for 1 Fig. 1. The molecular structure of 1 showing the atom numbering scheme Fig. 2. 1D double chains with 44–membered rings in 1 Fig. 3. 2D+2D→2D interpenetrated structure of 1 Fig. 4. 3D supramolecular structure of 1 Fig. 5. A comparison of luminescence intensity of 1 dispersed in different organic solvents (3mL). Fig. 6. Change of quenching efficiencies upon incremental addition of 1.0 mM (25 µL) solution of different nitroaromatic compounds to complex 1 dispersed in DMF (2.7 mL) Fig. 7. At low concentration of PA, emission quenching linearity relationship. S-V plot of complex 1 upon incremental addition of PA in DMF (inset) Fig. 8. Change of luminescence intensity histograms of DMF suspension of complex 1 before and after addition of PA(1.0 mM, 100 µL) into different nitroaromatic compounds (1.0 mM, 100 µL), respectively. Fig. 9. Recyclability of quenching efficiency of complex 1 dispersed in DMF towards PA solution (1.0 mM) Fig. 10. Luminescence intensity histograms of DMF suspension of complex 1 (2.7 mL) in the presence of different metal ions (0.01 M, 300 µL). Fig. 11. At low concentration of Fe3+ ion, emission quenching linearity relationship. S-V plot of complex 1 for Fe3+ ions in DMF (inset) Fig. 12. Luminescence intensity histograms of 1 in the presence of different metal ions (0.01 M, 300 µL) in DMF solution without and with Fe3+ ions (0.01 M, 300 µL).



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Table 1. Crystal data and structural refinement parameters for 1 1 Empirical formula

C30H29N5O8Zn

Formula weight

652.95

Crystal system

Triclinic

Space group

P-1

a (Å)

9.2936 (1)

b (Å)

9.9702 (2)

c (Å)

16.2822 (3)

α(º)

103.172 (1)

β (º)

91.941 (1)

γ(º)

101.420 (1)

V (Å3)

1434.98 (4)

Z

2

Dc (g cm-3)

1.511

µ (mm-1)

0.92

Measured refls.

29526

Independent refls.

5873

Rint

0.020

S

1.08

R1/wR2

0.028/0.078

∆ρmax/∆ ∆ρmin (eÅ-3)

0.39/−0.30


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Fig. 1. The molecular structure of 1 showing the atom numbering scheme



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Fig. 2. 1D double chains with 44–membered rings in 1


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Fig. 3. 2D+2D→2D interpenetrated structure of 1



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Fig. 4. 3D supramolecular structure of 1


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Fig. 5. A comparison of luminescence intensity of 1 dispersed in different organic solvents (3mL).



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Fig. 6. Change of quenching efficiencies upon incremental addition of 1.0 mM (25 µL) solution of different nitroaromatic compounds to complex 1 dispersed in DMF (2.7 mL)


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Fig. 7. At low concentration of PA, emission quenching linearity relationship. S-V plot of complex 1 upon incremental addition of PA in DMF (inset)



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Fig. 8. Change of luminescence intensity histograms of DMF suspension of complex 1 before and after addition of PA (1.0 mM, 100 µL) into different nitroaromatic compounds (1.0 mM, 100 µL), respectively


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Fig. 9. Recyclability of quenching efficiency of complex 1 dispersed in DMF towards PA solution (1.0 mM)



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Fig. 10. Luminescence intensity histograms of DMF suspension of complex 1 (2.7 mL) in the presence of different metal ions (0.01 M, 300 µL).


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Fig. 11. At low concentration of Fe3+ ion, emission quenching linearity relationship. S-V plot of complex 1 for Fe3+ ions in DMF (inset)



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Fig. 12. Luminescence intensity histograms of 1 in the presence of different metal ions (0.01 M, 300 µL) in DMF solution without and with Fe3+ ions (0.01 M, 300 µL).


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For Table of Contents Use Only

In this study, {[Zn(µ-HCIP)(µ-pbix)]·2H2O}n (1) was synthesized under solvothermal conditions with reduced Schiff base and neutral pbix ligands and characterized. Complex 1 exhibited 2D+2D→2D interpenetrated structures with sql topology. Luminescence titration experiments showed that complex 1 dispersed in DMF detected the picric acid in the presence of other interfering nitroaromatic compounds with a detection limit of 56.46 ppb. Moreover, complex 1 exhibited highly sensitive and selective detection towards Fe3+ ion in the presence of other interfering metal ions with a detection limit of 0.208 ppm.

Luminescent 2D+2D→2D interpenetrated Zn(II)-coordination polymer based on reduced Schiff base tricarboxylic acid and bis(imidazole) ligand for detection of picric acid and Fe3+ ions Mürsel Arici


Luminescent 2D + 2D â 2D Interpenetrated Zn(II)-Coordination

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