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Hamukwaya E, Naimhwaka J, Uahengo V. A multi-colorimetric probe to discriminate between heavy metal cations and anions in DMSO-H 2O with high selectivity for Cu 2+ and CN -: study of logic functions and its application in real samples. RSC Adv 2021; 11:29466-29485. [PMID: 35479545 PMCID: PMC9040645 DOI: 10.1039/d1ra04734e] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2021] [Accepted: 08/04/2021] [Indexed: 12/17/2022] Open
Abstract
A ditopic multi-colorimetric probe based on the phenylpridyl-thioic moiety (EN) was synthesized via a Schiff base reaction mechanism and characterized using 1H NMR and UV-vis spectroscopy. The colorimetric analyses carried out revealed that EN was capable of discriminating between a number of heavy metal cations via coordination induced charge transfer, as well as between anions through hydrogen bonding induced charge transfer, in DMSO–H2O (9 : 1). In particular, the ditopic probe could spectrally and colorimetrically recognize the most toxic heavy metal cations of Cd2+, Pb2+ and Hg2+, among others, in DMSO–H2O. Additionally, EN was selective and sensitive to the presence of CN−, F−, AcO− and H2PO4− in the same solvent system as cations. The reversibility and reproducibility studies showed that EN exhibited complementary IMP/INH logic functions, based on colour and spectral switching (ON/OFF), modulated by F−/Al3+. The real time application of the probe was tested on food grade products to detect the presence of F− in toothpastes and mouthwash dissolved in water, as well as cations in underground water (normally saline), which displayed substantial responses. Thus, EN displayed an excellent scope of response and can thus be developed for real time sensing kits, which could be used instantly in on-field analysis. Theoretical studies were conducted to complement the experimental work. A ditopic multi-colorimetric probe based on the phenylpridyl-thioic moiety (EN) was synthesized via a Schiff base reaction mechanism and characterized using 1H NMR and UV-vis spectroscopy.![]()
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Affiliation(s)
- Eunike Hamukwaya
- Department of Chemistry and Biochemistry, University of Namibia 340 Mandume Ndemufayo Avenue Windhoek 9000 Namibia +264 61 206 3465
| | - Johannes Naimhwaka
- Department of Chemistry and Biochemistry, University of Namibia 340 Mandume Ndemufayo Avenue Windhoek 9000 Namibia +264 61 206 3465
| | - Veikko Uahengo
- Department of Chemistry and Biochemistry, University of Namibia 340 Mandume Ndemufayo Avenue Windhoek 9000 Namibia +264 61 206 3465
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Freixa Z, Rivilla I, Monrabal F, Gómez-Cadenas JJ, Cossío FP. Bicolour fluorescent molecular sensors for cations: design and experimental validation. Phys Chem Chem Phys 2021; 23:15440-15457. [PMID: 34264251 PMCID: PMC8317197 DOI: 10.1039/d1cp01203g] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2021] [Accepted: 06/17/2021] [Indexed: 11/21/2022]
Abstract
Molecular entities whose fluorescence spectra are different when they bind metal cations are termed bicolour fluorescent molecular sensors. The basic design criteria of this kind of compound are presented and the different fluorescent responses are discussed in terms of their chemical behaviour and electronic features. These latter elements include intramolecular charge transfer (ICT), formation of intramolecular and intermolecular excimer/exciplex complexes and Förster resonance energy transfer (FRET). Changes in the electronic properties of the fluorophore based on the decoupling between its constitutive units upon metal binding are also discussed. The possibility of generating fluorescent bicolour indicators that can capture metal cations in the gas phase and at solid-gas interfaces is also discussed.
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Affiliation(s)
- Zoraida Freixa
- Ikerbasque, Basque Foundation for Science, 48009 Bilbao, Spain. and Department of Applied Chemistry, Faculty of Chemistry, University of the Basque Country (UPV/EHU), 20018 San Sebastián/Donostia, Spain
| | - Iván Rivilla
- Ikerbasque, Basque Foundation for Science, 48009 Bilbao, Spain. and Donostia International Physics Center (DIPC), 20018 San Sebastián/Donostia, Spain
| | - Francesc Monrabal
- Ikerbasque, Basque Foundation for Science, 48009 Bilbao, Spain. and Donostia International Physics Center (DIPC), 20018 San Sebastián/Donostia, Spain
| | - Juan J Gómez-Cadenas
- Ikerbasque, Basque Foundation for Science, 48009 Bilbao, Spain. and Donostia International Physics Center (DIPC), 20018 San Sebastián/Donostia, Spain
| | - Fernando P Cossío
- Donostia International Physics Center (DIPC), 20018 San Sebastián/Donostia, Spain and Department of Organic Chemistry I, Faculty of Chemistry, University of the Basque Country (UPV/EHU), 20018 San Sebastián/Donostia, Spain
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VanDenburgh KL, Liu Y, Sadhukhan T, Benson CR, Cox NM, Erbas-Cakmak S, Qiao B, Gao X, Pink M, Raghavachari K, Flood AH. Multi-state amine sensing by electron transfers in a BODIPY probe. Org Biomol Chem 2020; 18:431-440. [DOI: 10.1039/c9ob02466b] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Photoinduced electron transfer sets up the BODIPY probe for multi-state amine sensing by single-electron transfer then collisional quenching.
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Affiliation(s)
| | - Yun Liu
- Department of Chemistry
- Indiana University
- Bloomington
- USA
| | | | | | | | | | - Bo Qiao
- Department of Chemistry
- Indiana University
- Bloomington
- USA
| | - Xinfeng Gao
- Department of Chemistry
- Indiana University
- Bloomington
- USA
| | - Maren Pink
- Department of Chemistry
- Indiana University
- Bloomington
- USA
| | | | - Amar H. Flood
- Department of Chemistry
- Indiana University
- Bloomington
- USA
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Review on Recent Advances in Metal Ions Sensing Using Different Fluorescent Probes. J Fluoresc 2018; 28:999-1021. [DOI: 10.1007/s10895-018-2263-y] [Citation(s) in RCA: 79] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2018] [Accepted: 07/05/2018] [Indexed: 01/07/2023]
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Recent Advances in Macrocyclic Fluorescent Probes for Ion Sensing. Molecules 2017; 22:molecules22020200. [PMID: 28125069 DOI: 10.3390/molecules22020200] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2016] [Revised: 01/13/2017] [Accepted: 01/16/2017] [Indexed: 12/18/2022] Open
Abstract
Small-molecule fluorescent probes play a myriad of important roles in chemical sensing. Many such systems incorporating a receptor component designed to recognise and bind a specific analyte, and a reporter or transducer component which signals the binding event with a change in fluorescence output have been developed. Fluorescent probes use a variety of mechanisms to transmit the binding event to the reporter unit, including photoinduced electron transfer (PET), charge transfer (CT), Förster resonance energy transfer (FRET), excimer formation, and aggregation induced emission (AIE) or aggregation caused quenching (ACQ). These systems respond to a wide array of potential analytes including protons, metal cations, anions, carbohydrates, and other biomolecules. This review surveys important new fluorescence-based probes for these and other analytes that have been reported over the past five years, focusing on the most widely exploited macrocyclic recognition components, those based on cyclam, calixarenes, cyclodextrins and crown ethers; other macrocyclic and non-macrocyclic receptors are also discussed.
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Semeniuc RF, Reger DL, Smith MD. Silver(I) and rhenium(I) metal complexes of a 2,2′-bipyridine-functionalized third-generation tris(pyrazolyl)methane ligand. ACTA CRYSTALLOGRAPHICA SECTION C-STRUCTURAL CHEMISTRY 2016; 72:826-831. [DOI: 10.1107/s2053229616012171] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/03/2016] [Accepted: 07/27/2016] [Indexed: 11/10/2022]
Abstract
Heterotopic ligands offer the possibility of preparing polynuclear bimetallic complexes. Recent studies of heteroditopic ligands and their metal complexes have focused on novel supramolecular systems, biological activity, and the development of MRI contrast agents. The heteroditopic ligand Bipy–CH2–O–CH2–C(pz)3(Bipy-L; Bipy is 2,2′-bipyridine and pz is pyrazolyl) reacts with AgBF4to produce the coordination polymercatena-poly[[silver(I)-(μ-5-{[tris(pyrazol-1-yl)methoxy]methyl-κ2N,N′}-2,2′-bipyridine-κ2N,N′)] diethyl ether hemisolvate], {[Ag(C22H20N8O)]BF4·0.5C4H10O}n, and with Re(CO)5Br to form the discrete compound bromidotricarbonyl(5-{[tris(pyrazol-1-yl)methoxy]methyl}-2,2′-bipyridine-κ2N,N′)rhenium(I), [ReBr(C22H20N8O)(CO)3]. The silver(I) compound is a one-dimensional coordination polymer, built up by a κ2coordination mode of the bipyridine group and a κ2–κ0coordination mode of the –C(pz)3donor set. In [ReBr(Bipy-L)(CO)3], the ligand coordinates onlyviathe bipyridine end, leaving the –C(pz)3donor set free for further coordination interactions.
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Zhu L, Younes AH, Yuan Z, Clark RJ. 5-Arylvinyl-2,2'-bipyridyls: Bright "push-pull" dyes as components in fluorescent indicators for zinc ions. J Photochem Photobiol A Chem 2015; 311:1-15. [PMID: 26190906 DOI: 10.1016/j.jphotochem.2015.05.008] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
This article reviews the zinc(II)-dependent photophysical properties of arylvinylbipyridines (AVBs), a class of fluoroionophores in which 2,2'-bipyridyl and an aryl moiety are electronically conjugated. Zinc(II) binding of an AVB may lead to an emission bathochromic shift of the fluoroionophore without diminishing its fluorescence quantum yield. This observation can be explained using the excited state model of electron donor-π bridge-electron acceptor "push-pull" fluorophores, in which the bipy moiety acts as an electron acceptor, and zinc(II)-coordination strengthens its electron affinity. The spectral sensitivity of bipy-containing fluoroionophores, such as AVBs, to zinc(II) can be exploited to prepare fluorescent indicators for this ion. In several cases, AVB moieties are incorporated in fluorescent heteroditopic ligands, so that the variation of zinc(II) concentration over a relatively large range can be correlated to fluorescence changes in either intensity or color. AVB fluoroionophores are also used to introduce an intramolecular Förster resonance energy transfer (FRET) strategy for creating zinc(II) indicators with high photostability and a narrow emission band, two desired characteristics of dyes used in fluorescence microscopy.
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Affiliation(s)
- Lei Zhu
- Department of Chemistry and Biochemistry, Florida State University, 95 Chieftan Way, Tallahassee, FL 32306-4390, USA
| | - Ali H Younes
- Department of Chemistry and Biochemistry, Florida State University, 95 Chieftan Way, Tallahassee, FL 32306-4390, USA
| | - Zhao Yuan
- Department of Chemistry and Biochemistry, Florida State University, 95 Chieftan Way, Tallahassee, FL 32306-4390, USA
| | - Ronald J Clark
- Department of Chemistry and Biochemistry, Florida State University, 95 Chieftan Way, Tallahassee, FL 32306-4390, USA
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Zhu L, Yuan Z, Simmons JT, Sreenath K. Zn(II)-coordination modulated ligand photophysical processes - the development of fluorescent indicators for imaging biological Zn(II) ions. RSC Adv 2014; 4:20398-20440. [PMID: 25071933 PMCID: PMC4111279 DOI: 10.1039/c4ra00354c] [Citation(s) in RCA: 95] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Molecular photophysics and metal coordination chemistry are the two fundamental pillars that support the development of fluorescent cation indicators. In this article, we describe how Zn(II)-coordination alters various ligand-centered photophysical processes that are pertinent to developing Zn(II) indicators. The main aim is to show how small organic Zn(II) indicators work under the constraints of specific requirements, including Zn(II) detection range, photophysical requirements such as excitation energy and emission color, temporal and spatial resolutions in a heterogeneous intracellular environment, and fluorescence response selectivity between similar cations such as Zn(II) and Cd(II). In the last section, the biological questions that fluorescent Zn(II) indicators help to answer are described, which have been motivating and challenging this field of research.
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Affiliation(s)
- Lei Zhu
- Department of Chemistry and Biochemistry, Florida State University, 95 Chieftan Way, Tallahassee, FL 32306-4390, United States
| | - Zhao Yuan
- Department of Chemistry and Biochemistry, Florida State University, 95 Chieftan Way, Tallahassee, FL 32306-4390, United States
| | - J. Tyler Simmons
- Department of Chemistry and Biochemistry, Florida State University, 95 Chieftan Way, Tallahassee, FL 32306-4390, United States
| | - Kesavapillai Sreenath
- Department of Chemistry and Biochemistry, Florida State University, 95 Chieftan Way, Tallahassee, FL 32306-4390, United States
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Wu YY, Chen Y, Mu WH, Lv XJ, Fu WF. Naphthyridine–BF2 complexes with an amide-containing di-2-picolylamine receptor: Synthesis, structures and photo-induced electron transfer. J Photochem Photobiol A Chem 2013. [DOI: 10.1016/j.jphotochem.2013.08.015] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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Simmons JT, Allen JR, Morris DR, Clark RJ, Levenson CW, Davidson MW, Zhu L. Integrated and passive 1,2,3-triazolyl groups in fluorescent indicators for zinc(II) ions: thermodynamic and kinetic evaluations. Inorg Chem 2013; 52:5838-50. [PMID: 23621758 DOI: 10.1021/ic302798u] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
In addition to being a covalent linker in molecular conjugation chemistry, the function of a 1,2,3-triazolyl moiety resulting from the copper(I)-catalyzed azide-alkyne cycloaddition reaction as a ligand for metal ions is receiving considerable attention. In this work, we characterize the thermodynamic and kinetic effects of incorporating a 1,2,3-triazolyl group in a multidentate ligand scaffold on metal coordination in the context of fluorescent zinc(II) indicator development. Ligands L14, BrL14, and FL14 (1,4-isomers) contain the 1,4-disubstituted-1,2,3-triazolyl group that is capable of binding with zinc(II) in conjunction with a di(2-picolylamino) (DPA) moiety within a multidentate ligand scaffold. Therefore, the 1,2,3-triazolyl in the 1,4-isomers is "integrated" in chelation. The 1,5-isomers L15, BrL15, and FL15 contain 1,2,3-triazolyls that are excluded from participating in zinc(II) coordination. These 1,2,3-triazolyls are "passive linkers". Zinc(II) complexes of 2:1 (ligand/metal) stoichiometry are identified in solution using (1)H NMR spectroscopy and isothermal titration calorimetry (ITC) and, in one case, characterized in the solid state. The 1:1 ligand/zinc(II) affinity ratio of L14 over L15, which is attributed to the affinity enhancement of a 1,2,3-triazolyl group to zinc(II) over that of the solvent acetonitrile, is quantified at 18 (-1.7 kcal/mol at 298 K) using an ITC experiment. Fluorescent ligands FL14 and FL15 are evaluated for their potential in zinc(II) sensing applications under pH neutral aqueous conditions. The 1,4-isomer FL14 binds zinc(II) both stronger and faster than the 1,5-isomer FL15. Visualization of free zinc(II) ion distribution in live HeLa cells is achieved using both FL14 and FL15. The superiority of FL14 in staining endogenous zinc(II) ions in live rat hippocampal slices is evident. In summation, this work is a fundamental study of 1,2,3-triazole coordination chemistry, with a demonstration of its utility in developing fluorescent indicators.
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Affiliation(s)
- J Tyler Simmons
- Department of Chemistry and Biochemistry, Florida State University, 95 Chieftan Way, Tallahassee, Florida 32306-4390, United States
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Sreenath K, Clark RJ, Zhu L. Tricolor emission of a fluorescent heteroditopic ligand over a concentration gradient of zinc(II) ions. J Org Chem 2012; 77:8268-79. [PMID: 22924325 DOI: 10.1021/jo3016659] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The internal charge transfer (ICT) type fluoroionophore arylvinyl-bipy (bipy = 2,2'-bipyridyl) is covalently tethered to the spirolactam form of rhodamine to afford fluorescent heteroditopic ligand 4. Compound 4 can be excited in the visible region, the emission of which undergoes sequential bathochromic shifts over an increasing concentration gradient of Zn(ClO(4))(2) in acetonitrile. Coordination of Zn(2+) stabilizes the ICT excited state of the arylvinyl-bipy component of 4, leading to the first emission color shift from blue to green. At sufficiently high concentrations of Zn(ClO(4))(2), the nonfluorescent spirolactam component of 4 is transformed to the fluorescent rhodamine, which turns the emission color from green to orange via intramolecular fluorescence resonance energy transfer (FRET) from the Zn(2+)-bound arylvinyl-bipy fluorophore to rhodamine. While this work offers a new design of ratiometric chemosensors, in which sequential analyte-induced emission band shifts result in the sampling of multiple colors at different concentration ranges (i.e., from blue to green to orange as [Zn(2+)] increases in the current case), it also reveals the nuances of rhodamine spirolactam chemistry that have not been sufficiently addressed in the published literature. These issues include the ability of rhodamine spirolactam as a fluorescence quencher via electron transfer, and the slow kinetics of spirolactam ring-opening effected by Zn(2+) coordination under pH neutral aqueous conditions.
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Affiliation(s)
- Kesavapillai Sreenath
- Department of Chemistry and Biochemistry, Florida State University, Tallahassee, Florida 32306-4390, USA
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Younes AH, Clark RJ, Zhu L. ZnII and PbII coordination chemistry of 2,6-bis(1,2,3-triazol-4-yl)pyridine (clickate) and the metal ion-dependent emission of ‘clickate’–appended anthracene. Supramol Chem 2012. [DOI: 10.1080/10610278.2012.695790] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Affiliation(s)
- Ali H. Younes
- a Department of Chemistry and Biochemistry , Florida State University , Tallahassee , FL , 32306-4390 , USA
| | - Ronald J. Clark
- a Department of Chemistry and Biochemistry , Florida State University , Tallahassee , FL , 32306-4390 , USA
| | - Lei Zhu
- a Department of Chemistry and Biochemistry , Florida State University , Tallahassee , FL , 32306-4390 , USA
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Tian M, Ihmels H, Ye S. Fluorimetric detection of Mg2+ and DNA with 9-(alkoxyphenyl)benzo[b]quinolizinium derivatives. Org Biomol Chem 2012; 10:3010-8. [DOI: 10.1039/c2ob06948b] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
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Kuang GC, Allen JR, Baird MA, Nguyen BT, Zhang L, Morgan TJ, Levenson CW, Davidson MW, Zhu L. Balance between fluorescence enhancement and association affinity in fluorescent heteroditopic indicators for imaging zinc ion in living cells. Inorg Chem 2011; 50:10493-504. [PMID: 21905758 DOI: 10.1021/ic201728f] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
A fluorescent heteroditopic indicator for the zinc(II) ion possesses two different zinc(II) binding sites. The sequential coordination of zinc(II) at the two sites can be transmitted into distinct fluorescence changes. In the heteroditopic ligand system that our group developed, the formations of mono- and dizinc(II) complexes along an increasing gradient of zinc(II) concentration lead to fluorescence enhancement and an emission bathochromic shift, respectively. The extents of these two changes determine the sensitivity and, ultimately, the effectiveness of the heteroditopic indicator in quantifying zinc(II) ion over a large concentration range. In this work, a strategy to increase the degree of fluorescence enhancement upon the formation of the monozinc(II) complex of a heteroditopic ligand under simulated physiological conditions is demonstrated. Fluorination of the pyridyl groups in the pentadentate N,N,N'-tris(pyridylmethyl)ethyleneamino group reduces the apparent pK(a) value of the high-affinity site, which increases the degree of fluorescence enhancement as the monozinc(II) complex is forming. However, fluorination impairs the coordination strength of the high-affinity zinc(II) binding site, which in the triply fluorinated ligand reduces the binding strength to the level of the low-affinity 2,2'-bipyridyl. The potential of the reported ligands in imaging zinc(II) ion in living cells was evaluated. The subcellular localization properties of two ligands in five organelles were characterized. Both benefits and deficiencies of these ligands were revealed, which provides directions for the near future in this line of research.
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Affiliation(s)
- Gui-Chao Kuang
- Department of Chemistry and Biochemistry, Florida State University, Tallahassee, Florida 32306-4390, USA
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Aragay G, Pons J, Merkoçi A. Recent Trends in Macro-, Micro-, and Nanomaterial-Based Tools and Strategies for Heavy-Metal Detection. Chem Rev 2011; 111:3433-58. [DOI: 10.1021/cr100383r] [Citation(s) in RCA: 1023] [Impact Index Per Article: 78.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Affiliation(s)
- Gemma Aragay
- Nanobioelectronics & Biosensors Group, Institut Català de Nanotecnologia (CIN2, ICN-CSIC), 08193, Bellaterra, Barcelona, Spain
- Departament of Chemistry, Universitat Autònoma de Barcelona, 08193, Bellaterra, Barcelona, Spain
| | - Josefina Pons
- Departament of Chemistry, Universitat Autònoma de Barcelona, 08193, Bellaterra, Barcelona, Spain
| | - Arben Merkoçi
- Nanobioelectronics & Biosensors Group, Institut Català de Nanotecnologia (CIN2, ICN-CSIC), 08193, Bellaterra, Barcelona, Spain
- ICREA, Barcelona, Spain
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Gaidamauskas E, Crans DC, Parker H, Saejueng K, Kashemirov BA, McKenna CE. Quantification of foscarnet with chromogenic and fluorogenic chemosensors: indicator displacement assays based on metal ion coordination with a catechol ligand moiety. NEW J CHEM 2011. [DOI: 10.1039/c1nj20460b] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Younes AH, Zhang L, Clark RJ, Davidson MW, Zhu L. Electronic structural dependence of the photophysical properties of fluorescent heteroditopic ligands - implications in designing molecular fluorescent indicators. Org Biomol Chem 2010; 8:5431-41. [PMID: 20882250 DOI: 10.1039/c0ob00482k] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Two fluorescent heteroditopic ligands (2a and 2b) for zinc ion were synthesized and studied. The efficiencies of two photophysical processes, intramolecular charge transfer (ICT) and photoinduced electron transfer (PET), determine the magnitudes of emission bathochromic shift and enhancement, respectively, when a heteroditopic ligand forms mono- or dizinc complexes. The electron-rich 2b is characterized by a high degree of ICT in the excited state with little propensity for PET, which is manifested in a large bathochromic shift of emission upon Zn(2+) coordination without enhancement in fluorescence quantum yield. The electron-poor 2a displays the opposite photophysical consequence where Zn(2+) binding results in greatly enhanced emission without significant spectral shift. The electronic structural effects on the relative efficiencies of ICT and PET in 2a and 2b as well as the impact of Zn(2+)-coordination are probed using experimental and computational approaches. This study reveals that the delicate balance between various photophysical pathways (e.g. ICT and PET) engineered in a heteroditopic ligand is sensitively dependent on the electronic structure of the ligand, i.e. whether the fluorophore is electron-rich or poor, whether it possesses a donor-acceptor type of structure, and where the metal binding occurs.
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Affiliation(s)
- Ali H Younes
- Department of Chemistry and Biochemistry, Florida State University, Tallahassee, FL 32306-4390, USA
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Michaels HA, Murphy CS, Clark RJ, Davidson MW, Zhu L. 2-Anthryltriazolyl-containing multidentate ligands: zinc-coordination mediated photophysical processes and potential in live-cell imaging applications. Inorg Chem 2010; 49:4278-87. [PMID: 20369825 DOI: 10.1021/ic100145e] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
1,2,3-Triazol-4-yl (triazolyl)-containing tetradentate ligand 1 undergoes fluorescence enhancement upon binding to zinc ion (Zn(2+)) in both organic (acetonitrile) and aqueous solutions. A 1:1 complex of 1 with a trigonal bipyramidal Zn(2+) was characterized by X-ray crystallography. The cyclic voltammogram (CV) of 1 suggests that an intramolecular photoinduced electron transfer (PET) process is thermodynamically feasible which would quench the fluorescence of the 2-anthryltriazolyl fluorophore. On the basis of the X-ray and CV data, it was initially postulated that the 1:1 binding between Zn(2+) and ligand 1 shuts down the PET quenching pathway of the free ligand, which leads to the fluorescence enhancement of 1. However, the nuance of the interaction between 1 and Zn(2+) was revealed by isothermal titration calorimetry (ITC) and (1)H NMR titration experiments. A two-step binding process was observed which proceeds through an intermediate species of 2:1 (ligand/Zn(2+)) stoichiometry. Upon close examination of the fluorescence spectra of 1 during the Zn(2+) titration experiment, the fluorescence profile is in fact consistent with a two-step binding process in which a moderate fluorescence enhancement was observed during the early stage of the titration, followed by a bathochromic shift in conjunction with a more pronounced enhancement as Zn(2+) concentration increases. The studies on compounds 2-5 support the amended hypothesis that upon increasing Zn(2+) concentration, compound 1 first undergoes fluorescence enhancement because of the formation of a 2:1 (ligand to Zn(2+)) complex which slows down the PET quenching process. As Zn(2+) concentration increases, the 2:1 complex is converted into a 1:1 complex which facilitates an intramolecular exciplex formation between the excited 2-anthryltriazolyl fluorophore and the Zn(2+)-bound pyridyl moiety. Finally, the potential of compound 1 as an intracellular fluorescent indicator for Zn(2+) was evaluated. HeLa cells loaded with compound 1 grown in Zn(2+)-rich media show stronger fluorescence than those grown under Zn(2+)-deprived conditions, confirming the promise that the triazolyl-containing polyaza fluoroionophores can be developed into intracellular fluorescent indicators targeting biological Zn(2+).
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Affiliation(s)
- Heather A Michaels
- Department of Chemistry and Biochemistry, Florida State University, Tallahassee, Florida 32306-4390, USA
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Younes AH, Zhang L, Clark RJ, Zhu L. Fluorescence of 5-arylvinyl-5'-methyl-2,2'-bipyridyl ligands and their zinc complexes. J Org Chem 2010; 74:8761-72. [PMID: 19852467 DOI: 10.1021/jo901889y] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The photophysical properties of 5-arylvinyl-5'-methyl-2,2'-bipyridyls (AVMBs, 1-9, 11) and their zinc complexes were studied. Similar 2,2'-bipyridyl-based ligands have been applied as optical sensors for metal ions and sensitizers for solar energy conversion. The goal of this investigation is to reveal the factors that determine the emission band shift and fluorescence quantum yield change of the title ligand system upon zinc binding. The outcome of this study will not only advance the fundamental understanding of the coordination-driven photophysical processes embodied in the AVMB platform but facilitate the rational design of fluorescent probes for metal ions, particularly zinc. The AVMB ligands were synthesized using the Horner-Wadsworth-Emmons reaction. AVMBs containing electron-donating aryl groups show absorption and emission in the visible region, which can be assigned to charge-transfer transitions as supported by solvent-dependency and computational studies. The binding between AVMB ligands and zinc ion in acetonitrile was studied using isothermal titration calorimetry (ITC). A multicomponent equilibrium model is suggested that explains the multiple transitions evidenced in fluorescence titration isotherms. Coordination to zinc ion stabilizes the charge-transfer excited state of an AVMB ligand with an electron-donating aryl substituent, consequently results in bathochromic shifts in both absorption and emission. However, unlike the emission band shift, the fluorescence quantum yield change upon zinc complex formation does not have an intuitive correlation with the electronic nature of the aryl group. Lifetime measurements using the Time-Correlated Single Photon Counting method enabled the determination of nonradiative and radiative decay rate constants. Both rates of an AVMB ligand decrease upon zinc binding. The collective effect gives rise to the change in fluorescence quantum yield with the apparent lack of correlation with the electronic property of the aryl group.
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Affiliation(s)
- Ali H Younes
- Department of Chemistry and Biochemistry, Florida State University, Tallahassee, Florida 32306-4390, USA
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Wandell RJ, Younes AH, Zhu L. Metal-coordination-mediated sequential chelation-enhanced fluorescence (CHEF) and fluorescence resonance energy transfer (FRET) in a heteroditopic ligand system. NEW J CHEM 2010. [DOI: 10.1039/c0nj00241k] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
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Zhang L, Murphy CS, Kuang GC, Hazelwood KL, Constantino MH, Davidson MW, Zhu L. A fluorescent heteroditopic ligand responding to free zinc ion over six orders of magnitude concentration range. Chem Commun (Camb) 2009:7408-10. [PMID: 20024244 DOI: 10.1039/b918729d] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
A fluorescent heteroditopic ligand useful in live-cell imaging studies responds to free zinc ion concentration over a range of six orders of magnitude in a buffered aqueous solution via dual-channel fluorescence.
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Affiliation(s)
- Lu Zhang
- Department of Chemistry and Biochemistry, Florida State University, Tallahassee, FL 32306-4390, USA
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