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Developing and Evaluating New Ion Sensors Rapid, Efficient Screening of Waste Remediation Agents

Determination of Metal Ion Binding Properties of Crown Ethers Derivatives Using Electrospray Ionization Mass Spectrometry Sheldon M. Williams (Jennifer S. Brodbelt Group) Department of Chemistry and Biochemistry University of Texas at Austin February 12, 2002. H. O. C. H. C. H. O. C.

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Developing and Evaluating New Ion Sensors Rapid, Efficient Screening of Waste Remediation Agents

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  1. Determination of Metal Ion Binding Properties of Crown Ethers Derivatives Using Electrospray Ionization Mass Spectrometry Sheldon M. Williams (Jennifer S. Brodbelt Group) Department of Chemistry and Biochemistry University of Texas at Austin February 12, 2002

  2. H O C H C H O C H 2 2 3 S S O O S S Lariat Ethers Using Electrospray Ionization Mass Spectrometry to Investigate Molecular Recognition and Target Analyte Selectivity Applications : • Developing and Evaluating New Ion Sensors • Rapid, Efficient Screening of Waste Remediation Agents • Enhanced Detection Methods for Metal Ion Binding Analytes • Understanding Interactions of Natural Products and Biomolecules with Metal Ions Caged Thiacrown Ethers

  3. Lariat Ethers and Alkali Metal Ions • Objective • Determine alkali metal cation selectivities of six lariat ethers with ether pendant groups by ESI-MS Methods: • Customized Finnigan quadrupole ion trap mass spectrometer • ESI-MS of solutions at 3.1 kV needle voltage and 3.0 L/min • Lariat ether concentration: 5 x 10-5 M; Each metal concentration: 1 x 10-4 M • Ab initio molecular modeling with RHF 3/21G* method 3.1 kV 10V @ 525 kHz across end caps Channeltron Ion Detector Ion Optics ESI Probe 1st Vacuum Stage 2nd Vacuum Stage 0 – 10 kV Ramp on ring electrode 1.1 MHz RF 100 mL Syringe and Pump

  4. H O C H C H O C H H O C H 2 2 3 3 O O O O O O O O O O nC3H7 nC3H7 nC3H7 OCH2CH2OCH2CH2OCH3 O C H O C H C H O C H O C H C H O C H C H O C H 3 2 2 3 H 2 2 2 2 3 O O O O O O O O O O O O O O O O O O O O 2 6 5 Lariat Ether Structures 3 1 4

  5. ESI Mass Spectra of Lariat Ether 1 with LiCl, NaCl, KCl and RbCl (1:2:2:2:2) 99% Methanol / 1% Chloroform 100 (1 + Na)+ (1 + K)+ H O C H 3 Relative Intensity (1 + Rb)+ (1 + Li)+ O O O O 0 O 100 200 300 400 500 600 m/z 1 Selectivity: Na+ > K+>> Rb+ >> Li+

  6. Variations in Metal Ion Selectivity for Lariat Ethers R1 R2 O O O O O (LE + Li)+ (LE + Na)+ Relative Signal Intensity (% Total Ion Count) (LE + K)+ (LE + Rb)+ Lariat Ether R1 R2 1 HOCH3 2 nC3H7OCH3 3HOCH2CH2OCH3 4 nC3H7OCH2CH2OCH3 5 HOCH2CH2OCH2CH2OCH3 6nC3H7OCH2CH2OCH2CH2OCH3

  7. R1 R2 O O O O O Variations in Na/K Selectivity for Lariat Ethers in 99/1 Methanol/ Chloroform 3.0 Intensity Ratio (LE + Na)+/ (LE + K)+ 2.5 2.0 1.5 R1 R2 1.0 1 HOCH3 2 nC3H7OCH3 3HOCH2CH2OCH3 4 nC3H7OCH2CH2OCH3 5 HOCH2CH2OCH2CH2OCH3 6nC3H7OCH2CH2OCH2CH2OCH3 0.5 0.0 1 3 4 5 6 2 Lariat Ether

  8. R H O O O O O Sodium Complexation of Lariat Ethers 1, 3, and 5 1 3 5 oxygen carbon sodium ion potassium ion Na+ Na+ Na+ Potassium Complexation of Lariat Ethers 1, 3, and 5 1 3 5 1 R = OCH3 3 R = OCH2CH2OCH3 5 R = OCH2CH2OCH2CH2OCH3 K+ K+ K+

  9. Conclusions • Presence of a dioxapentyl group in conjunction with a propyl sidearm (i.e., in 4) creates the most Na+ selective lariat ether • Ab initio calculations show that the addition of the dioxapentyl or trioxaoctyl group pulls Na+ above the crown ether ring oxygens, increasing interaction with the former at the expense of interaction with the latter. • Addition of a longer trioxaoctyl pendant group results in a preference for complexation of K+ over Na+ • Addition of a second pendant arm, a propyl group, regenerates Na+ selectivity • Method is convenient for a variety of solvent systems

  10. Sulfur Containing Macrocycles with Heavy Metal Ions • Objective: • Evaluate relative heavy metal ion binding affinities of thiacrown ethers with S, O, and N heteroatoms. • Determine avidities for extracting heavy metals from aqueous solution. • Method: • ThermoFinnigan LCQ Duo quadrupole ion trap mass spectrometer • 50/50 methanol/ chloroform solutions • Extractions of ions from water to chloroform

  11. S S S S S S S S HO S S S S S S S N S S H S O O S S S S S H N S S S S O O O N O Ts H N O N S S S S S N S S O O O S S S O S N S O S S S S N S S O O O O O S S S S N S S O Macrocycles for Mercury Extraction OH 4 5 3 2 1 9 8 10 7 6 14 11 13 12 16 15

  12. S S S S S S S S HO S S S S S S S N S S H S O O S S S S S H N S S S S O O O N O Ts H N O N S S S S S N S S O O O S S S O S N S O S S S S N S S O O O O O S S S S N S S O Macrocycles for Mercury Extraction OH 4 5 3 2 1 9 8 10 7 6 14 11 13 12 16 15

  13. 100 (L+Zn+ClO4)+ (L+Cd+Cl)+ (L+Cd+ClO4)+ (L+H+HClO4)+ (L+Zn)2+ (L+Pb+ClO4)+ (2L+Cd)2+ Relative Abundance (2L+Zn)2+ higher order complexes (L+Cd)2+ (L+Pb)2+ (L+H)+ 0 2000 400 800 1200 1600 100 (L+Hg+ClO4)+ (L+Hg+Cl)+ Relative Abundance (L+Hg)2+ 0 2000 400 800 1200 1600 m/z O S S O O S S O ESI-MS of 16 with Metals in 50/50 Methanol/Chloroform Solution Containing Four Metals 16 withCd(ClO4)2, Pb(ClO4)2, and Zn(ClO4)2 (1:1:1:1) 16 m/z 16 with Cd(ClO4)2, Pb(ClO4)2, Hg(ClO4)2, and Zn(ClO4)2 (1:1:1:1) Enormous Hg Affinity!!!

  14. Determination of Extraction Selectivities and Avidities by ESI-MS Vigorous Shaking (30 s) Cl- Hg2+ Cl- Hg2+ Hg2+ H2O Cl- Hg2+ Cl- Cl- Hg2+ Hg2+ Hg2+ Cl- Hg2+ Cl- CHCl3 Hg2+ Cl- ESI-MS Cl- Hg2+

  15. S S S S S S S S HO S S S S S S S N S S H S O O S S S S S H N S S S S O O O N O Ts H N O N S S S S S N S S O O O S S S O S N S O S S S S N S S O O O O O S S S S N S S O Macrocycles for Mercury Extraction OH 4 5 3 2 1 9 8 10 7 6 14 11 13 12 16 15

  16. S S S S S S S S HO S S S S S S S N S S H S O O S S S S S H N S S S S O O O N O Ts H N O N S S S S S N S S O O O S S S O S N S O S S S S N S S O O O O O S S S S N S S O Macrocycles for Mercury Extraction OH 4 5 3 2 1 9 8 10 7 6 14 11 13 12 16 15

  17. 100 (15+Hg+Cl)+ Relative Abundance 0 200 400 600 800 1000 1200 S S S S S S S S S S S S S S S S S S S S S S S S S S S S S S S S S S S S S S S S S S S S O O S S ESI-MS of Macrocycle-Containing Chloroform Phase after Extraction of Aqueous Phase Containing Four Metals 15 with CdCl2, PbCl2, HgCl2, and ZnCl2 (1.0:130:130:130:130) 15 m/z Extraction of Hg Is Greatly Favored 6, 7, 13, 15, and 16 with HgCl2 (2.0:2.0:2.0:2.0:2.0:1.0) Relative Intensity (L+Hg+Cl)+ 1 6 7 13 15 16 Thiacrown Ether

  18. Conclusions • Several sulfurs in the binding cavity are required for efficient, selective mercury extraction • 2 or more sulfurs in thiacrown ether ring • 14 to 32 atom ring circumference – 18 to 22 appears to perform best • Oxygens can be present in ring, but nitrogens adversely affect mercury extraction efficiency • Thiacrown ethers have potential as agents for selectively extracting and detecting aqueous mercury ion • Analysis range of at least 5x10-6 M to 0.03 M aqueous Hg ion • Excellent selectivity for Hg observed over Pb, Cd, Zn, Cu, alkali metals, and alkaline earth metals

  19. Acknowledgments Advisor & Principle Investigator Prof. Jennifer Brodbelt Collaborators Prof. Richard Bartsch, Texas Tech University Prof. Alan Marchand, University of North Texas Brodbelt Lab Colleagues Support National Science Foundation National Institute of Health Welch Foundation Texas Advanced Technology Program

  20. R1 R2 O O O O O Variations in Na+ versus K+ Selectivity in Various Solvent Systems 3.0 Intensity Ratio (LE + Na)+/ (LE + K)+ 2.5 2.0 1.5 R1 R2 1.0 1 HOCH3 2 nC3H7OCH3 3HOCH2CH2OCH3 4 nC3H7OCH2CH2OCH3 5 HOCH2CH2OCH2CH2OCH3 6nC3H7OCH2CH2OCH2CH2OCH3 0.5 0.0 1 3 4 5 6 2 Lariat Ether 5/95 CH3OH /CH3CN 99/1 CH3OH /CHCl3 75/25 CH3OH /CHCl3 50/50 CH3OH /CHCl3

  21. O R3 OCH2CNR1R2 • Current Work • Lariat Ethers with oxalkylamide pendant arm • Vary basicity of amide nitrogen • Vary acidity/basicity of solution, solvent system • Branched versus linear pendant arm effects • Expand metal ions to include alkaline earth and transition metals

  22. S O O S O S S O O S S O ESI-MS of Macrocycle-Containing Chloroform Phase after Extraction from H2O to CHCl3 Selectivity for HgCl2 versus CuCl2 Macrocycle 16 16 Macrocycle 7 7

  23. 100 B L = 16 10 1 -6 -5 -4 1x10 1x10 1x10 ESI-MS Signal-to-Noise Ratio versus HgCl2 Concentration for Extraction from H2O to CHCl3 A L = 15 Signal-to-Noise Ratio of (L + Hg + Cl)+ [HgCl ] (M) 2 (aq)

  24. O S S O O S S O Competitive Extraction from H2O to CHCl3 of Mercury(II) Ion with Various Counterions 16 with Hg(ClO4)2, HgCl2, HgBr2, HgI2, and Hg(CH3COO )2 (1.0:1.4:1.4:1.4:1.4) (16+Hg+Br)+ 100 (16+Hg+ClO4)+ (16+Hg+I)+ (16+Hg+CH3COO)+ Relative Abundance (16+Hg+Cl)+ 0 1100 1150 1200 1250 1300 1350 1400 m/z 16 with Hg(ClO4)2 and Hg(CH3COO)2 (1.0:25:25) 16 100 (16+Hg+CH3COO)+ (16+Hg+ClO4)+ Relative Abundance 0 1100 1150 1200 1250 1300 1350 1400 m/z HgI+ > HgBr+> HgCl+ > HgCH3COO+ > HgClO4+

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