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Photoelectron Spectroscopy of Multiply-Charged Anions

Photoelectron Spectroscopy of Multiply-Charged Anions. Lai-Sheng Wang Department of Physics, Washington State University & Chemical & Materials Sciences Division, Pacific Northwest National Laboratory. Ken: Congrat to your (60 ± 1)th B-Day!. Anion 2007 6/29 – 7/3, 2007 Park City, Utah .

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Photoelectron Spectroscopy of Multiply-Charged Anions

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  1. Photoelectron Spectroscopyof Multiply-Charged Anions Lai-Sheng Wang Department of Physics, Washington State University & Chemical & Materials Sciences Division, Pacific Northwest National Laboratory Ken: Congrat to your (60±1)th B-Day! Anion 2007 6/29 – 7/3, 2007 Park City, Utah

  2. Multiply-charged anions were rarely observed in the gas phase

  3. The earliest observed doubly charged anion J. Chem. Phys. 50, 1896 (1969)

  4. Doubly-charged carbon clusters and fullerenes Phys. Rev. Lett. 65, 625 (1990) Cn2– (n = 7-28) by Cs+ sputtering of graphite J. Am. Chem. Soc. 113 , 6795 (1991) Phys. Rev. Lett. 67, 1242 (1991)

  5. Prior research on multiply-charged anions Experimental: Mass spectrometry observations (70’) Compton et al.: first observation of Cn2- (n = 7-28) (1990) C602-: Coe et al. and Compton et al. (91’) Kebarle, Lau, etc: electrospray (mid-90’s) Theoretical: (1990’s) Boldyrev/Gutsev (J. Phys. Chem. 94, 2256, 1990) high EA species; MkXk+1- or (MX)kX-, stable dianions MkXk+22- Cederbaum (Scheller, Compton & Cederbaum, Science270, 1160, 1995) Simons/Boldyrev/Gutowski (Acc. Chem. Res. 29, 497, 1996) Ortiz Landman …

  6. Multiply-charged anionsare common in the condensed phase • Simple oxo-anions SO42-, CO32-, PO43-, C2O42-, S2O82-, Si2O52-, CrO42-, Cr2O72-, VO43-, RuO43-… • Inorganic and organometallic multiply- charged anions MX42-, MX62-, (X = Metal, X = halides)… • Organic multiply-charged anions • Biomolecules

  7. n- M -HV Evaporation Breakup John B. Fenn et al. J. Phys. Chem. 88, 4451 & 4671 (1984): Nobel Prize 2002 Electrospray IonizationInterface between solution and gas phase n- M beam Heated Electrospray Desolvation Skimmer Capillary Capillary Charged droplets Kebarle, Lau, etc: ESI MS of MCA (mid-90’s)

  8. Solution-phase chemistry in the gas phase Unique properties of multiply-charged anions Nature400, 245 (1999); Phys. Rev. Lett.81, 2667 (1998); 81, 3351 (1998); J. Chem. Phys.110, 3635 (1999); Phys. Rev. Lett. 83, 3402 (1999); J. Phys. Chem. A 104, 1978 (2000); Chem. Phys. Lett. 307, 391 (1999);… Electronic structure of solution anions and complexes in the gas phase Re2Cl82-, S2O82-, Cr2O72-, H2P2O72-, Ru6(CO)182-, ZrF62-, ML62- (M = Re, Os, Ir, Pt), … J. Chem. Phys. 111, 4497 (1999); 112, 6959 (2000); J. Am. Chem. Soc. 112, 2096 (2000); 112, 2339 (2000); J. Phys. Chem. A 104, 4429 (2000); 105, 10468 (2001); J. Am. Chem. Soc. 122, 8305 (2000)… Solvation and solvent stabilization of complex and multiply-charged anions SO42-(H2O)n, C2O42-(H2O)n, NO3-(H2O)n, F-(H2O)n, -O2C-(CH2)x-CO2-(H2O)n, … Science294, 1322 (2001); J. Chem. Phys. 113, 10837 (2001); 115, 2889 (2001); 116, 561 (2002); J. Phys. Chem. A 106, 7607 (2002); J. Am. Chem. Soc. 124, 10182 (2002); JACS 126, xxx (2004)… Probing the electronic structure of Fe-S clusters, complexes and Fe-S proteins Phys. Rev. Lett.89, 163401 (2002); J. Phys. Chem. A 107, 1703 (2003); 107, 2821 (2003); 107, 2898 (2003); J. Phys. Chem. A 107, 4612 (2003); J. Am. Chem. Soc. 125, 14072 (2003)…

  9. Current experimental effort on multiply charged anions Compton: Coulomb barrier, electron attachment (ESI) Kappes: PES, laser detachment, lifetime in a Penning trap ESI/Laser ablation Denmark group (Nielsen, Andersen, Hvelplund): electron scattering, charge transfer in storage ring (ESI) Mainz group (Herlert, Schweikhard): Multiply charged anion formation in a Penning trap Neumark/Woste/Meijer: IR of SO42-(H2O)n- Wiliams: MS and IR of SO42-(H2O)n- Dessent …… ESI is gaining popularity as a powerful ion source not just for analytical mass spectrometry, but also for physical chemistry and spectroscopy

  10. Photoelectron spectroscopy of singly and multiply-charged anions

  11. Difference between photodetachment of singly and multiply-charged anions

  12. Repulsive coulomb barrier (RCB) and negative electron binding energies

  13. The first PES of a doubly charged anion: Direct observation of the RCB Citrate 266 nm 355 nm Wang, Ding & Wang, Phys. Rev. Lett. 81, 3351 (1998)

  14. Intramolecular coulomb repulsion and RCB 266 nm 355 nm Wang, Ding, Wang & Nicholas, Phys. Rev. Lett. 81, 2667 (1998)

  15. Intramolecular coulomb repulsion and RCB rn O O C—–(CH2)n—–C Θ Θ O O r RCB = e2/r = 14.4/r (eV.Å) Wang, Ding, Wang & Nicholas Phys. Rev. Lett. 81, 2667 (1998) EB + RCB = constant = 3.2 eV ! = electron binding energy of R-CO2–

  16. Observation of negative electron binding energies: photoelectron spectra of [CuPc(SO3)4]4- and [CuPc(SO3)4H]3- X. B. Wang & L. S. Wang, Nature400, 245 (1999) Kappes et al., isomer-dependent life times: J. Phys. Chen. A107, 794 (2003)

  17. Solvation and solvent stabilization of multiply-charged anions •Isolated SO42- and PO43- Anions Do Not Exist • Boldyrev & Simons, J. Phys. Chem. 98, 2298 (1994) • SO42- ----> SO4- + e-, -1.6 eV • Blades & Kebarle, J. Am. Chem. Soc. 116, 10761 (1994) • ESI of Na2SO4 solution • Observed SO42-(H2O)n, n = 4-16 • Questions: • Minimum number of H2O needed to stabilize SO42- • How is SO42- solvated? • Inside or outside? • Solvation shell?

  18. ESI Mass Spectra of SO42-(H2O)n Blades & Kebarle J. Am. Chem. Soc. 116, 10761 (1994)

  19. PES of SO42–(H2O)n and solvent stabilization of SO42– VDE ADE

  20. Calculated structures of SO42-(H2O)n, n = 1-6

  21. PES of SO42-(H2O)n, n = 4-40 Large hydrated clusters: a single sulfate dianion in the center of a water droplet Wang, Yang, Nicholas & Wang Science294, 1322 (2001)

  22. Recent IR studies on SO42-(H2O)n J. Am. Chem. Soc. 129, 2220 (2007) Bush, Saykally & Williams IR for n = 6 at OH stretching at 130 K J. Chem. Phys. 125, 111102 (2006) Zhou, Santambrogio, Brummer, Moore, Woste, Meijer, Neumark & Asmis IR for n = 3-24 using FELIX at 17 K

  23. Isomers of SO42–(H2O)n Gao & Liu, J. Chem. Phys. 123, 224302 (2005) J. Am. Chem. Soc. 129, 2220 (2007) Bush, Saykally & Williams

  24. Dissociation of SO42–(H2O)n for n = 3-17 (BIRD) Wong & Williams J. Phys. Chem. A107, 10976 (2003) Two dissociation Channels:SO42–(H2O)n→ SO42–(H2O)n-k + kH2O (1)→ HSO4–(H2O)k + (H2O)mOH– (2)For n = 3, 4: (2) exclusivelyn = 5, 6: both (1) and (2), but for n = 5, (2) dominates, and for n = 6, (1) dominatesn≥ 7: (1) exclusively

  25. Size-dependent charge separation reactions of SO42–(H2O)n for n = 3-7 Gao & Liu, J. Chem. Phys. 123, 224302 (2005)

  26. Second generation ESI-PES apparatus at low-temperatures 5 m

  27. The low-temperature ion trap Cold Head 10 K Rotatable Ion entrance Ion exit

  28. Vibrationally-cold photoelectron spectrum of C60– Hot bands Wang, Woo & Wang, J. Chem. Phys. 123, 051106 (2005)

  29. Vibrationally resolved PES of cold C70- EA(C60) = 2.683 ± 0.008 eV EA(C70) = 2.765 ± 0.010 eV Chem. Phys. Lett. 233, 52 (1995) EA(C60) = 2.666 ± 0.001 eV EA(C70) = 2.676 ± 0.001 eV Too low!!!

  30. Photoelectron spectroscopy of cold C702- C702- C702- C70- EA2(C70) = ADE(C702-) = 0.02 eV Wang, Woo, Huang, Kappes & Wang, Phys. Rev. Lett. 96, 143002 (2006)

  31. Electron-electron repulsion in C702- e2/r = 1.8 to 2.0 eV EA1(C70) – EA2(C70) = 2.765 – 0. 02 = 2.745 eV Wang, Woo, Huang, Kappes & Wang, Phys. Rev. Lett. 96, 143002 (2006)

  32. Acknowledgments Dr. Xue-Bin Wang Dr. Jie Yang Dr. Chuan-Fan Ding (Fudan U.) Dr. Xin Yang (Fudan U.) Dr. You-Jun Fu (U. Kentucky) Dr. Hin-Koon Woo (Scripps) Dr. Tom Waters (U. Melbourne) Supported by: DOE, NSF & Guggenheim Foundation Collaboration: J. B. Nicholas (theo) M. M. Kappes (fullerenes)

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