1. John Herbert Department of Chemistry The Ohio State University Anion–water vs. electron–water hydrogen bonds 61 st Molecular Spectroscopy Symposium 6/23/06

2. Related work at this meeting X – (H 2 O) theory: Anne McCoy, Samantha Horvath (RA08) X – (H 2 O) & e – (H 2 O) n expt: Mark Johnson, Rob Roscioli (FA10), Joe Bopp (FA11), Jeff Headrick (FA05)

3. Vibrational spectroscopy of e – (H 2 O) n Bend spectra AA bend redshifted by ≈50 cm –1 H-bonded bends in (H 2 O) n blueshifted w.r.t. H 2 O Expt: Hammer et al., Science 306, 675 (2004) Theory: B3LYP/aug3-cc-pVDZ (scaled harmonic) H2OH2O intensity HOH bend spectrum  / cm –1 Latest expts.: J.R. Roscioli & J.C. Bopp FA10 & FA11

4. Stretch spectra AA symm/asymm stretch redshifted by ≈300 cm –1 Very intense w.r.t. H-bonded OH stretches  / cm –1 OD stretch spectrum H2OH2O Expt: Hammer et al., Science 306, 675 (2004) Theory: B3LYP/aug3-cc-pVDZ (scaled harmonic) intensity Vibrational spectroscopy of e – (H 2 O) n Latest expts.: J.R. Roscioli & J.C. Bopp FA10 & FA11

5. Vibrational spectroscopy of X – (H 2 O) Roscioli, Diken, Johnson, Horvath, McCoy; J. Phys. Chem. A 110, 4943 (2006) Anion H + affinity (kJ/mol) Observed redshift (cm –1 ) OH stretch freqs  H-bond = 1523 cm –1  free = 3687 cm –1

6. n —›  * charge transfer B3LYP/6-31++G* NBOs F lone pair 1.88e (B3LYP) 1.91e (Hartree-Fock) OH  * 0.11e (B3LYP) 0.09e (Hartree-Fock)  E D-›A = 64 kcal/mol (B3LYP) = 80 kcal/mol (Hartree-Fock)

7. NBO analysis of e – (H 2 O) n Diffuse functions allow atoms to overlap at great distance e – cannot be tagged to one particular atom Sol’n: Use compact basis set, in conjunction with a ghost atom

8. NBO analysis of e – (H 2 O) n B3LYP/6-31++G*-f(2+) NBOs  *(OH) 0.16e  *(OH) 0.10e Ry*(Gh) 0.13e Ry*(H) 0.36e Ry*(H) 0.15e Diffuse functions allow atoms to overlap at great distance e – cannot be tagged to one particular atom Sol’n: Use compact basis set, in conjunction with a ghost atom

9. NBO analysis of e – (H 2 O) n Donor– acceptor interaction Stabilization energy (kcal/mol) n —›  *10.8 n —›  *7.1 n —›  *7.2 e — —›  *36.3 e — —›  *6.7 e — —› Ry*8.8 e — —› Ry*6.3 e — —› Ry*2.9 e — —› Ry*2.8 W–W H-bonds e — –W H-bonds B3LYP/6-31++G*-f(2+) NBOs  *(OH) 0.16e  *(OH) 0.10e Ry*(Gh) 0.13e Ry*(H) 0.36e Ry*(H) 0.15e

10. NBO analysis of e – (H 2 O) n HF/6-31++G*-f(2+) NBOs Donor– acceptor interaction Stabilization energy (kcal/mol) n —›  *11.6 n —›  *8.8 n —›  *6.4 Gh —› Ry*8.0 Gh —› Ry*5.3 Gh —›  *4.0 Gh —›  *3.3  –› Gh3.0 n (Gh) 0.91e W–W H-bonds

11. O–H  * occupancies B3LYP/6-31++G*-f(2+)  = 0.164  = 0.001  = 0.096  = 0.001  = 0.006  = 0.000  = 0.021  = 0.014  = 0.011  = 0.011

12. O–H  * occupancies B3LYP/6-31++G*-f(2+)  = 0.164  = 0.001  = 0.096  = 0.001  = 0.006  = 0.000  = 0.021  = 0.014  = 0.011  = 0.011 HF/6-31++G*-f(2+)  = 0.005  = 0.000  = 0.012  = 0.000  = 0.000  = 0.000  = 0.009  = 0.009  = 0.007  = 0.007

13. Vibrational spectra: e – (H 2 O) 4 B3LYP/aug3-cc-pVDZ Hartree-Fock/aug3-cc-pVDZ  / cm –1 intensity Scaled harmonic freqs

14. Vibrational spectra: e – (H 2 O) 4 B3LYP/aug3-cc-pVDZ Hartree-Fock/aug3-cc-pVDZ  / cm –1 intensity Scaled harmonic freqs AA symm str

15. Vibrational spectra: e – (H 2 O) 4 B3LYP/aug3-cc-pVDZ Hartree-Fock/aug3-cc-pVDZ  / cm –1 intensity Scaled harmonic freqs AA asymm str

16. Vibrational spectra: e – (H 2 O) 4 B3LYP/aug3-cc-pVDZ Hartree-Fock/aug3-cc-pVDZ  / cm –1 intensity Scaled harmonic freqs H-bonded str

17. Vibrational spectra: (H 2 O) 6 – “AA” “book”  / cm –1 intensity B3LYP/aug3-cc-pVDZ scaled harmonic

18. AA symm stretch in e – (H 2 O) 6 ∆(spin density) potential (cm –1 ) B3LYP/6-31++G*-f(2+) AA + Gh spin density 0.82–0.89e (v=0) 0.80–0.90e (v=1) ∆Q (AA symm str)

19. F – (H 2 O) revisited F ‹–› O chg. transfer 0.1e (v=0) 0.2e (v=1) r (O–H) / Å potential (cm –1 ) ∆(charge)  q (O)  q (F) B3LYP/6-31++G*

20. F – (H 2 O) revisited r (O–H) / Å  q (O)  q (F) NBO occupancy  *(OH)  *(FH) r (O–H) / Å F —... HOH FH... — OH B3LYP/6-31++G* ∆(charge) potential (cm –1 )

21. To summarize a very simple story: e – –›  * charge transfer in e – (H 2 O) n is comparable to n –›  * charge transfer in F – (H 2 O) More significant redshift in F – (H 2 O) arises from low-lying FH... – OH diabatic state