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Nyiranshuti L, Andrews ER, Povolotskiy LI, Gomez FM, Bartlett NR, Royappa AT, Rheingold AL, Seitz WR, Planalp RP. Development of a Ratiometric Fluorescent Cu(II) Indicator Based on Poly( N-isopropylacrylamide) Thermal Phase Transition and an Aminopyridyl Cu(II) Ligand. Molecules 2023; 28:7097. [PMID: 37894575 PMCID: PMC10609634 DOI: 10.3390/molecules28207097] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2022] [Revised: 09/30/2023] [Accepted: 10/09/2023] [Indexed: 10/29/2023] Open
Abstract
An aqueous Cu2+ and Zn2+ indicator is reported based on copolymerizing aminopyridine ligands and the environment-sensitive dansyl fluorophore into the responsive polymer poly(N-isopropylacrylamide) (PNIPAm). The metal ion binding creates charge and solvation that triggers PNIPAm's thermal phase transition from hydrophobic globule to hydrophilic open coil. As a basis for sensing the metal-binding, the dansyl fluorescence emission spectra provide a signal at ca. 530 nm and a signal at 500 nm for the hydrophobic and hydrophilic environment, respectively, that are ratiometrically interpreted. The synthesis of the title pyridylethyl-pyridylmethyl-amine ligand (acronym PEPMA) with a 3-carbon linker to the copolymerizable group, aminopropylacrylamide (PEPMA-C3-acrylamide), is reported, along with a nonpolymerizable model ligand derivative. The response of the polymer is validated by increasing temperature from 25 °C to 49 °C, which causes a shift in maximum emission wavelength from 536 nm to 505 nm, along with an increase in the ratio of emission intensity of 505 nm/536 nm from 0.77 to 1.22 (λex = 330 nm) as the polymer releases water. The addition of divalent Cu or Zn to the indicator resulted in a dansyl emission shift of 10 nm to a longer wavelength, accompanied by fluorescence quenching in the case of Cu2+. The addition of EDTA to the Cu2+-loaded indicator reversed the fluorescence shift at 25 °C to 35 °C. The affinities of Cu2+ and Zn2+ for the PEPMA derivatives are log Kf = 11.85 and log Kf = 5.67, respectively, as determined by potentiometric titration. The single-crystal X-ray structure of the Cu2+-PEPMA derivative is five-coordinate, of-geometry intermediate between square-pyramidal and trigonal-bipyramidal, and is comparable to that of Cu2+ complexes with similar formation constants.
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Affiliation(s)
- Lea Nyiranshuti
- Department of Chemistry, University of New Hampshire, Durham, NH 03824, USA; (L.N.); (E.R.A.); (L.I.P.); (F.M.G.); (N.R.B.)
| | - Emily R. Andrews
- Department of Chemistry, University of New Hampshire, Durham, NH 03824, USA; (L.N.); (E.R.A.); (L.I.P.); (F.M.G.); (N.R.B.)
| | - Leonid I. Povolotskiy
- Department of Chemistry, University of New Hampshire, Durham, NH 03824, USA; (L.N.); (E.R.A.); (L.I.P.); (F.M.G.); (N.R.B.)
| | - Frances M. Gomez
- Department of Chemistry, University of New Hampshire, Durham, NH 03824, USA; (L.N.); (E.R.A.); (L.I.P.); (F.M.G.); (N.R.B.)
| | - Nathan R. Bartlett
- Department of Chemistry, University of New Hampshire, Durham, NH 03824, USA; (L.N.); (E.R.A.); (L.I.P.); (F.M.G.); (N.R.B.)
| | | | - Arnold L. Rheingold
- Department of Chemistry, University of California San Diego, La Jolla, CA 92093, USA;
| | - William Rudolf Seitz
- Department of Chemistry, University of New Hampshire, Durham, NH 03824, USA; (L.N.); (E.R.A.); (L.I.P.); (F.M.G.); (N.R.B.)
| | - Roy P. Planalp
- Department of Chemistry, University of New Hampshire, Durham, NH 03824, USA; (L.N.); (E.R.A.); (L.I.P.); (F.M.G.); (N.R.B.)
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Fulton LA, Seitz WR, Planalp RP. Aggregation of poly(N-isopropylacrylamide) homopolymer by Cu2+ and Zn2+: Significance for ratiometric metal ion indicators. Polyhedron 2020. [DOI: 10.1016/j.poly.2020.114797] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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Abdalrahman MA, Abebe F, Briggs J, Kassel WS, Burdette SC, Seitz WR, Planalp RP. A bifunctional 2,2′:6′,2″-terpyridine-based ligand for ratiometric Cu(II) sensing. J COORD CHEM 2017. [DOI: 10.1080/00958972.2017.1300660] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Affiliation(s)
| | - F. Abebe
- Department of Chemistry and Biochemistry, Worcester Polytechnic Institute, Worcester, MA, USA
- Department of Chemistry, Morgan State University, Baltimore, MD, USA
| | - J. Briggs
- Chemistry Department, University of New Hampshire, Durham, NH, USA
| | - W. S. Kassel
- Department of Chemistry, Villanova University, Villanova, PA, USA
| | - S. C. Burdette
- Department of Chemistry and Biochemistry, Worcester Polytechnic Institute, Worcester, MA, USA
| | - W. R. Seitz
- Chemistry Department, University of New Hampshire, Durham, NH, USA
| | - R. P. Planalp
- Chemistry Department, University of New Hampshire, Durham, NH, USA
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