Exploring the Detection of Metal Ions by Tailoring the Coordination

Feb 22, 2017 - Their application in detecting metal ions was explored, and the ... (10) From a topological perspective, the SBUs act as a six-connecte...
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Exploring the Detection of Metal Ions by Tailoring the Coordination Mode of V‑Shaped Thienylpyridyl Ligand in Three MOFs Li-Juan Han,†,‡ Wei Yan,† Shu-Guang Chen,† Zhen-Zhen Shi,† and He-Gen Zheng*,† †

State Key Laboratory of Coordination Chemistry, School of Chemistry and Chemical Engineering, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210023, P. R. China ‡ Key Laboratory of Inorganic Chemistry in Universities of Shandong, Department of Chemistry and Chemical Engineering, Jining University, Qufu 273155, P. R. China S Supporting Information *

ABSTRACT: By employing a rational design approach, we synthesized three luminescent metal−organic frameworks (MOFs) 1−3 affording different coordination modes of V-shaped thienylpyridyl ligand. Their application in detecting metal ions was explored, and the mechanism was inferred. And the result exhibits that MOF 3 is a dual-responsive luminescent probe for Fe3+ and Al3+ ions.

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INTRODUCTION The detection and quantification of metal ions played an especially important role in biological and living systems,1 nuclear industry, and environment-protecting field.2 Thus, various types of detection method have been developed.3−5 Among the methods, the fluorescent chemosensor for metal ions provided a sensitive and efficient analytical way. Luminescent metal−organic frameworks (MOFs) as a promising fluorescent chemosensor have been extensively investigated to detect metal cations due to their high porosity, tunability, and mild synthetic conditions.6 In recent years, the research on MOF fluorescent chemosensor highlighted the significance of such Lewis basic sites within porous MOFs, such as unsaturated (open) pyridyl group, to enhance unique recognition toward different metal ions, but most of them shared one characteristic: organic ligand has only one Lewis basic pyridyl group or striazine;7,8 however, only a few MOFs having several Lewis basic pyridyl groups from an organic ligand were reported.9 To study the fluorescent sensing of MOFs owning more than one Lewis basic pyridyl groups, we designed and synthesized a new V-shaped N-donor thienylpyridyl ligand (BPTP; Scheme 1 and Supporting Information) possessing three alternate pyridyl groups and two thienyl groups. Fortunately, three MOFs having different BPTP coordination modes were rationally fabricated from BPTP, 4,4′-oxidibenzoic acid (OBA; Scheme S1), and metal salts. Here, we investigated their metal ion sensing ability and the influence of different coordination environments on detecting metal ions and further presumed the sensing mechanism. © XXXX American Chemical Society

RESULTS AND DISCUSSION Crystal Structure of [Zn2(OBA)2(BPTP)] (1). X-ray crystallographic analysis reveals that 1 crystallizes in monoclinic system, P21/c space group. Four carboxylate groups from four OBA ligands coordinate to Zn(1) and Zn(2) centers with average Zn−O bond length of 2.047 Å, forming a paddlewheel [Zn2(CO2)4] secondary building unit (SBU; Figure 1a). Then SBU connected to each other by the bidentate OBA ligands, resulting in a two-dimensional (2D) network with rhomb-like windows (Figure 1b). In the minimum rhomb-like unit, it holds a micropore with an aperture of 14.29 Å × 14.29 Å. BPTP ligand further bridged the apical position of the paddlewheel SBU to build the three-dimensional (3D) porous framework structure, and the uncoordinated nitrogen atoms of middle pyridine are exposed in pores of 1 (Figure 1c). All the topological analyses and some diagrams were provided by TOPOS 4.0 program.10 From a topological perspective, the SBUs act as a six-connected node, so the whole framework of 1 can be topologically described as a six-connected mab network with the point symbol of {44·610·8}. Because of the large void volume in the single net of 1, two independent equivalent frameworks interpenetrate each other to form a twofold interpenetrating net (Figure 1d). PLATON analysis gives the free void volume ratio of 43.3% in 1. Crystal Structure of [Ni(OBA)2(BPTP)2(H2O)2] (2). MOF 2 crystallizes in triclinic P1̅ space group with the molecule Received: December 16, 2016

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DOI: 10.1021/acs.inorgchem.6b03075 Inorg. Chem. XXXX, XXX, XXX−XXX

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Inorganic Chemistry Scheme 1. Synthesis of Ligand BPTP

Figure 2. Molecular structure of 2. Symmetry code: No. 1 = x, y, z, No. 2 = −x, −y + 1, −z + 1.

coordinated to each Cd(II) ion, forming a slightly distorted octahedron. In addition, a one-dimensional (1D) chain was built by Cd−N (from terminal pyridine) coordination bonds with the average length of 2.320 Å (Figure 3b). Further, around the octatomic ring [Cd(CO2)2Cd], bidentate OBA ligands linked the adjacent Cd(II) cations to establish a layered network. The above structures crossed each other, then a twofold interpenetrating 3D framework was formed (Figure 3c). Topologically, the whole structure was represented as a 3,8-connected sqc495 network with the point symbol of {4· 62}4{44·68·812·104}. The Coordination Modes of Ligand BPTP. The coordination modes of ligand BPTP in 1, 2, and 3 were shown in Figure 4. The nitrogen atoms of middle pyridine, unsaturated (open) Lewis acidic metal sites, were exposed in pores of 1 (Figure 1c and Figure 4a). In 2, the nitrogen atoms of terminal pyridine located on the outside (Figure 2 and Figure 4b), while all the nitrogen atoms were coordinated with Cd cations in 3 (Figure 4c). Here, we employed 1−3 as fluorescent sensors, to detect metal ions selectively, and investigated the influence of different coordination environments on detecting metal ions. Fluorescent Sensing of Metal Ions. Fluorescent sensing of metal cations was performed for 1−3. Different metalline solutions (nitrate dispersed in dimethylformamide (DMF), 5 × 10−3 M) were added into the suspensions of 1−3, respectively. Fe3+ exhibits a drastic quenching effect on the luminescence of 1, 2, and 3, with 3 having most extreme quenching result (Figure 5), so 3 is most sensitive toward Fe3+ with a detection limit of 0.36 μM (Figures S11−S13). In addition, adding Al3+ ions to the DMF suspension of 1, 2, and 3, successively, the fluorescence emission intensity of 3 shows a remarkable

Figure 1. (a) Coordination mode of Zn(II) cations for 1. Symmetry code: No. 1 = −x + 1, −y + 1, −z + 1, No. 2 = x − 1, −y + 1/2, z − 1/ 2, No. 3 = −x + 2, −y + 2, −z + 1, No. 4 = x − 1, −y + 1/2, z − 1/2. (b) The 2D network with rhomb-like windows constructed by OBA ligands and Zn(II) cations in 1. (c) The 3D porous framework of 1 decorated by uncoordinated pyridyl nitrogen atoms. (d) Schematic representation of a simplified twofold interpenetrating porous 3D framework for 1 with a mab topology.

residing on a specific position. The relevant asymmetric unit consists of half crystallographically independent Ni(II) center, two OBA anions, two BPTP ligands, and two lattice water molecules. The six-coordinated Ni(II) cation has an approximately octahedral coordination environment, in which the equatorial plane is composed of four oxygen atoms from two OBA ligands and two independent lattice water molecules, while two nitrogen atoms from two different BPTP ligands occupy the apical position (Figure 2). Crystal Structure of [Cd2(OBA)2(BPTP)(H2O)](3). MOF 3 crystallizes in the triclinic crystal system with space group P1̅. Three nitrogen atoms in BPTP are all coordinated to cadmium (Figure 3a). Four oxygen atoms from two OBA ligands bidentately coordinated to one Cd(II) ion, and one oxygen atom from coordination water and one nitrogen atom from middle pyridine coordinated to the same Cd(II) ion, constructing a strongly distorted octahedron. While for another Cd(II) coordination environment, two OBA ligands bidentately bridged two Cd(II) centers to form an octatomic ring [Cd(CO2)2Cd], and other two OBA ligands outside of the ring bidentately coordinated to two Cd(II) centers, respectively; moreover, two nitrogen atoms from terminal pyridines B

DOI: 10.1021/acs.inorgchem.6b03075 Inorg. Chem. XXXX, XXX, XXX−XXX

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Inorganic Chemistry

Figure 3. (a) Coordination environments surrounding Cd(II) cations in compound 3. Symmetry code: No. 1 = x + 1, y, z + 1, No. 2 = x, y, z, No. 3 = −x + 1, −y + 1, −z + 1, No. 4 = −x + 1, −y, z − 1, No. 5 = x, y + 1, z − 1, No. 6 = x + 1, y + 1, z, No. 7 = −x, −y + 1, −z + 1, No. 8 = x + 1, y + 1, z. (b) A single 3D framework constructed from Cd(II) ions, BPTP, and OBA ligands in the bc plane. (c) Schematic representation of a simplified twofold interpenetrating porous 3D framework for 3 with a sqc495 topology.

and S22), caused by Fe3+ or Cu2+ ions coordinated to the open nitrogen atoms, then the aromatic system of the pyridine ring was perturbed. The perturbation of the aromatic system led to deformation of the distribution of π-electron density in the ring.11 Therefore, obtained results suggested that Fe3+ or Cu2+ ions perturbed the electron density of remaining uncoordinated pyridyl, so 1 exhibited weak bonding to Fe3+ or Cu2+ ions. This behavior was consistent with the N 1s XPS spectra. In addition, the above-mentioned IR band wavenumbers of 1 did not change position or were shifted toward lower wavenumbers, so we speculate that the coordination interactions between Fe3+ (or Cu2+) and pyridyl nitrogen atom were weak and not enough to change the position. Just as three electronwithdrawing pyridyl groups coexist in a BPTP ligand, open Lewis acidic metal sites exposed in the pores of 1 did not play a primary role in quenching Fe3+, so our result would further perfect previous reports.7 Additionally, the liquid UV−vis absorption spectra were recorded (Figure 8). Obviously, Fe3+ ions in DMF have a wide absorption band from 250 to 400 nm, which covered the whole range of 3 and a majority absorption band of 2, while only partial absorption band of 1 was mantled by Fe3+ ions’ band. Upon light excitation, there is a competition of absorbing light source energy,12 and in consequence the Fe3+ ions almost filtered all the light adsorption of 3; then, 3 presented the best quenching effect for Fe3+ ions. However, absorption peak of 1 was partially overlapped by peaks of Fe3+ ions, so 1 exhibits weaker quenching effect for Fe3+ ions than 2 and 3. In addition, Al3+ ions’ absorption band only covered the absorption band of 3 in the range from 260 to 300 nm, but Al3+ ions’ another absorption band was covered by 3 from 310 to 400 nm. As a result, after adding Al3+ ions, the fluorescence emission intensity of 3 showed a remarkable enhancement.

Figure 4. Coordination mode and conformation of ligand BPTP in 1− 3 (numbers representing the distances of N3−N1 and N3−N2, and the angles of N1−N3−N2). (a) 1; (b) 2; (c) 3.

enhancement (Figure 5c,d and Figures S8−S10). The different fluorescence intensity changes between Fe3+, Al3+, and other cations are clearly observed, indicating the fact that 3 was a dual-responsive luminescent probe for Fe3+ and Al3+ ions. Mechanism of Luminescence Quenching Response. To elucidate the possible mechanism of luminescence quenching by metal cations, powder X-ray diffraction (PXRD), Fourier-transform infrared (FT-IR) spectra, and Xray photoelectron spectroscopy (XPS) measurements were performed. The PXRD patterns suggested the retention of both the crystallinity and the integrity of the frameworks after immersed in different solutions 80 h (Figures S17−S19). Moreover, XPS and FT-IR spectra of 2 and 3 before and after immersed in different metal cations solution remained unchanged (Figures S23−S30 and Figures S34−S41), revealing no coordination interactions of the Fe3+ (or other ions) with 2 and 3. However, N 1s XPS and FT-IR spectra of 1 after immersed in Fe3+ or Cu2+ solution changed (Figures 6, 7, S20− S22, and S31−S33). For example, the N 1s peak from free pyridyl nitrogen atoms of 1 at 399.10 eV is shifted to 399.35 eV after 1 immersed in Fe3+, indicating the weak affinity of pyridyl nitrogen atoms to Fe3+. The bands between 711 and 696 cm−1 are assigned to the C−H (from middle pyridine ring) deformation vibrations, and the CN and C−N stretching bands appeared in the regions of 1611−1593 cm−1 and 1029−1011 cm−1 in FT-IR spectrum of 1 (Figure 7 and Figure S20). After 1 immersed in Fe3+ or Cu2+, the above three bands deformed slightly (Figures 7, S21

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CONCLUSION In summary, because of three electron-withdrawing pyridyl groups coexisting in a BPTP ligand, free Lewis basic pyridyl sites in the pores of 1 did not play a primary role in quenching Fe3+, but 3 exhibited drastic luminescent quenching effect for Fe3+ with detection limit of 0.36 μM. We hypothesized that the luminescent quenching effect for Fe3+ by 1−3 mainly depended on the UV−vis competitive adsorption. MOF 3 had most C

DOI: 10.1021/acs.inorgchem.6b03075 Inorg. Chem. XXXX, XXX, XXX−XXX

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Figure 5. Fluorescence spectra of 1−3 (DMF suspension, 2.5 mL) added different metal ions (5 × 10−3 M, 100 μL except Al3+ of 50 μL (c, d)). (a) 1 (excited at 370 nm). (b) 2 (excited at 365 nm). (c) 3 (excited at 310 nm). (d) Bar graph representing the change of the relative emission intensity in the presence of various metal ions (F and F0 represented the fluorescence intensity of MOFs with and without metal ions, respectively).

Figure 6. N 1s XPS spectra of 1 before and after immersed in Fe3+/ Cu2+.

Figure 8. Liquid UV−vis spectra of Fe3+, Al3+, and 1−3 in DMF.

extreme quenching ability resulting from wide absorption band of Fe3+ ions covering the whole absorption peak of 3. In addition, 3 showed a significant fluorescence enhancement in the presence of Al3+ ions within seconds. Accordingly, it can be believed that 3 can be a promising dual-responsive luminescent sensor for Fe3+ and Al3+ ions.

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ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.inorgchem.6b03075.

Figure 7. FT-IR spectra of 1 before and after immersed in Fe3+/Cu2+. D

DOI: 10.1021/acs.inorgchem.6b03075 Inorg. Chem. XXXX, XXX, XXX−XXX

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S. J.; Chen, F.; Hall, G.; Chabal, Y. J.; Li, J. Highly Efficient Luminescent Metal−Organic Framework for the Simultaneous Detection and Removal of Heavy Metals from Water. ACS Appl. Mater. Interfaces 2016, 8, 30294−30303. (d) Du, P.-Y.; Gu, W.; Liu, X. Inorg. Chem. 2016, 55, 7826−7828. (e) Yang, C.-X.; Ren, H.-B.; Yan, X.-P. Fluorescent Metal-Organic Framework MIL-53(Al) for Highly Selective and Sensitive Detection of Fe3+ in Aqueous Solution. Anal. Chem. 2013, 85, 7441−7446. (f) Zhao, B.; Chen, X.-Y.; Chen, Z.; Shi, W.; Cheng, P.; Yan, S.-P.; Liao, D.-Z. A porous 3D heterometalorganic framework containing both lanthanide and high-spin Fe(II) ions. Chem. Commun. 2009, 3113−3115. (g) Xiao, Y.; Cui, Y.; Zheng, Q.; Xiang, S.; Qian, G.; Chen, B. A microporous luminescent metal− organic framework for highly selective and sensitive sensing of Cu2+ in aqueous solution. Chem. Commun. 2010, 46, 5503−5505. (h) Wu, Y.; Yang, G.-P.; Zhao, Y.; Wu, W.-P.; Liu, B.; Wang, Y.-Y. Three new solvent-directed Cd(II)-based MOFs with unique luminescent properties and highly selective sensors for Cu2+ cations and nitrobenzene. Dalton Trans. 2015, 44, 3271−3277. (i) Wu, Y.; Yang, G.-P.; Zhang, Y.; Shi, N.; Han, J.; Wang, Y.-Y. A new luminescent Cd(II)-MOF as a highly selective chemical probe for Fe3+ in aqueous solution with mixed metal ions. RSC Adv. 2015, 5, 90772−90777. (7) (a) Chen, B.; Wang, L.; Xiao, Y.; Fronczek, F. R.; Xue, M.; Cui, Y.; Qian, G. A Luminescent Metal−Organic Framework with Lewis Basic Pyridyl Sites for the Sensing of Metal Ions. Angew. Chem., Int. Ed. 2009, 48, 500−503. (b) Zhao, J.; Wang, Y.-N.; Dong, W.-W.; Wu, Y.P.; Li, D.-S.; Zhang, Q.-C. A Robust Luminescent Tb(III)-MOF with Lewis Basic Pyridyl Sites for the Highly Sensitive Detection of Metal Ions and Small Molecules. Inorg. Chem. 2016, 55, 3265−3271. (c) Xia, T.; Song, T.; Zhang, G.; Cui, Y.; Yang, Y.; Wang, Z.; Qian, G. A Terbium Metal−Organic Framework for Highly Selective and Sensitive Luminescence Sensing of Hg2+ Ions in Aqueous Solution. Chem. - Eur. J. 2016, 22, 18429−18434. (8) Tang, Q.; Liu, S.; Liu, Y.; Miao, J.; Li, S.; Zhang, L.; Shi, Z.; Zheng, Z. Cation Sensing by a Luminescent Metal-Organic Framework with Multiple Lewis Basic Sites. Inorg. Chem. 2013, 52, 2799− 2801. (9) Zheng, M.; Tan, H.; Xie, Z.; Zhang, L.; Jing, X.; Sun, Z. Fast Response and High Sensitivity Europium Metal Organic Framework Fluorescent Probe with Chelating Terpyridine Sites for Fe3+. ACS Appl. Mater. Interfaces 2013, 5, 1078−1083. (10) (a) Blatov, V. A.; Shevchenko, A. P. TOPOS, Version 4.0 Professional (Beta Evaluation); Samara State University: Samara, Russia, 2006. (b) Blatov, V. A.; Shevchenko, A. P.; Proserpio, D. M. Applied Topological Analysis of Crystal Structures with the Program Package ToposPro. Cryst. Growth Des. 2014, 14, 3576−3586. (11) (a) Lewandowski, W.; Kalinowska, M.; Lewandowska, H. The influence of metals on the electronic system of biologically important ligands. Spectroscopic study of benzoates, salicylates, nicotinates and isoorotates. Review. J. Inorg. Biochem. 2005, 99, 1407−1423. (b) Cogal, S.; Kiristi, M.; Ocakoglu, K.; Oksuz, L.; Oksuz, A. U. Electrochromic properties of electrochemically synthesized porphyrin/ 3-substituted polythiophene copolymers. Mater. Sci. Semicond. Process. 2015, 31, 551−560. (12) (a) 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. (b) Chen, J.; Yi, F.-Y.; Yu, H.; Jiao, S.; Pang, G.; Sun, Z.-M. Fast response and highly selective sensing of amine vapors using a luminescent coordination. Polymer. Chem. Commun. 2014, 50, 10506−10509. (c) Xu, H.; Gao, J.; Qian, X.; Wang, J.; He, H.; Cui, Y.; Yang, Y.; Wang, Z.; Qian, G. Metal−organic framework nanosheets for fast response and highly sensitive luminescent sensing of Fe3+. J. Mater. Chem. A 2016, 4, 10900−10905.

Synthesis and characterization of BPTP ligand and crystals 1−3, experimental methods and supporting figures (PDF) CCDC 1519026 crystal data for 1; CCDC 1518929 crystal data for 2; CCDC 1519030 crystal data for 3 (CIF)

AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. ORCID

He-Gen Zheng: 0000-0001-8763-9170 Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS This work was financial supported by the National Natural Science Foundation of China (No. 21371092), the Natural Science Foundation of Shandong Province (No. ZR2013BL004), and the Talent Culturing Plan for Leading Disciplines of Univ. in Shandong Province.

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REFERENCES

(1) (a) Gu, B.; Zhou, Y.; Zhang, X.; Liu, X.; Zhang, Y.; Marks, R.; Zhang, H.; Liu, X.; Zhang, Q. Thiazole Derivative-Modified Upconversion Nanoparticles for Hg2+ Detection in Living Cells. Nanoscale 2016, 8, 276−282. (b) Zhou, W.; Liang, W.; Li, D.; Yuan, R.; Xiang, Y. Dual-color encoded DNAzyme nanostructures for multiplexed detection of intracellular metal ions in living cells. Biosens. Bioelectron. 2016, 85, 573−579. (c) Zhang, X.; Xiao, Y.; Qian, X. A Ratiometric Fluorescent Probe Based on FRET for Imaging Hg2+ Ions in Living Cells. Angew. Chem., Int. Ed. 2008, 47, 8025−8029. (2) Kim, H. N.; Ren, W. X.; Kim, J. S.; Yoon, J. Fluorescent and colorimetric sensors for detection of lead, cadmium, and mercury ions. Chem. Soc. Rev. 2012, 41, 3210−3244. (3) (a) Darbha, G. K.; Singh, A. K.; Rai, U. S.; Yu, E.; Yu, H.; Chandra Ray, P. Selective detection of mercury(II) ion using nonlinear optical properties of gold nanoparticles. J. Am. Chem. Soc. 2008, 130, 8038−8043. (b) Chatterjee, A.; Santra, M.; Won, N.; Kim, S.; Kim, J. K.; Kim, S. B.; Ahn, K. H. Selective fluorogenic and chromogenic probe for detection of silver ions and silver nanoparticles in aqueous media. J. Am. Chem. Soc. 2009, 131, 2040−2041. (4) (a) Chang, K.-K.; Cai, Y.-H.; Chen, C.-H.; Wang, Y.-S. A neutralization charge detection method for detecting ions under ambient and liquid-phase conditions. Chem. Commun. 2016, 52, 5187−5189. (b) Ding, S.-Y.; Dong, M.; Wang, Y.-W.; Chen, Y.-T.; Wang, H.-Z.; Su, C.-Y.; Wang, W. Thioether-Based Fluorescent Covalent Organic Framework for Selective Detection and Facile Removal of Mercury(II). J. Am. Chem. Soc. 2016, 138, 3031−3037. (5) (a) Moirangthem, M.; Arts, R.; Merkx, M.; Schenning, A. P. H. J. An Optical Sensor Based on a Photonic Polymer Film to Detect Calcium in Serum. Adv. Funct. Mater. 2016, 26, 1154−1160. (b) Kim, S. H.; Kim, K.-S.; Char, K.; Yoo, S.; Sohn, B.-H. Short-range ordered photonic structures of lamellae-forming diblock copolymers for excitation-regulated fluorescence enhancement. Nanoscale 2016, 8, 10823−10831. (c) Murakami, H.; Shinkai, S. Metal-controlled aggregation-deaggregation in calix[4] arene-based self-assemibies. J. Chem. Soc., Chem. Commun. 1993, 1533−1535. (6) (a) Wu, L.-L.; Wang, Z.; Zhao, S.-N.; Meng, X.; Song, X.-Z.; Feng, J.; Song, S.-Y.; Zhang, H.-J. A Metal−Organic Framework/DNA Hybrid System as a Novel Fluorescent Biosensor for Mercury(II) Ion Detection. Chem. - Eur. J. 2016, 22, 477−480. (b) Wu, P.; Liu, Y.; Liu, Y.; Wang, J.; Li, Y.; Liu, W.; Wang, J. Cadmium-Based Metal−Organic Framework as a Highly Selective and Sensitive Ratiometric Luminescent Sensor for Mercury(II). Inorg. Chem. 2015, 54, 11046− 11048. (c) Rudd, N. D.; Wang, H.; Fuentes-Fernandez, E. M. A.; Teat, E

DOI: 10.1021/acs.inorgchem.6b03075 Inorg. Chem. XXXX, XXX, XXX−XXX