Understanding Complex Spectral Signatures of Embedded Excess Protons in Molecular

Scaffolds

Andrew F. DeBlase Advisor: Mark A. Johnson

68th Internatinal Symposium on Molecular Spectroscopy

The Ohio State University: June 17, 2013

Previously …

Charged hydrogen bonds show distinct spectral features.

Roscioli et. al. Science 2007

Ar-predissociation

1000 1500 2000 2500 3000 3500

Photon Energy (cm-1)

O H+

OCH2CH3

CH2CH3

CH3CH2

CH3CH2

Stoyanov and Reed J. Phys. Chem. A 2006Room temperature FTIR

Not Always Simple!

Chris Leavitt

Leavitt et. al. J. Am. Soc. Mass Spectrom. 2011

N+

NH

O

OH

OH

H

H

Cyclic ionic hydrogen bond

x8

νOH

νsp

𝐼 𝑐𝑎𝑙𝑐 (𝜈𝑠𝑝 )𝐼𝑐𝑎𝑙𝑐 (𝜈𝑂𝐻 )

=3.9

𝐼 𝑒𝑥𝑝 (𝜈𝑠𝑝 )𝐼𝑒𝑥𝑝 (𝜈𝑂𝐻 )

=4.5

B3LYP/6-311++G**scaled by 0.967 above 2000 cm-1

1200 1600 2000 2400 2800 3200 3600Photon Energy (cm-1)

Isolate the Cyclic Intramolecular Proton Bond

N OH3C

H3CH

O

N OH3C

H3CH H

N FH3CH3C

H

ΔPA (kJ∙mol-1)

≈ 150

≈ 190

≈ 340

Prof. Tom Lectka: JHU

R (Å)

Cb

Nc A

H3C

H3CHd

Ca

R

2.763

2.763

2.634

Dramatic Change in Complexity as ΔPA is Decreased

2700 2800 2900 3000 3100 3200 3300 3400Photon Energy (cm-1)

× 10

N FH3CH3C

H• One sharp NH fundamental• Weak CH stretches

νNH

νNH

× 10

N OH3C

H3CH H

νNH

νCH

νCH

Dramatic Change in Complexity as ΔPA is Decreased

2700 2800 2900 3000 3100 3200 3300 3400Photon Energy (cm-1)

× 10

N FH3CH3C

H• One sharp NH fundamental• Weak CH stretches

νNH

νNH

× 10

N OH3C

H3CH H

νNH

νCH

νCH

All these features disappearwhen NH is replaced by ND

DeBlase, et. al. J. Chem. Phys. In Press

2×Bend+stretchinteractions?

1500 2000 2500 3000 3500

Photon Energy (cm-1)

Where’s NH the Bending Fundamental?

00.20.40.60.81.0

PH

+

Multiple possibilities for Fermi resonances

2 × 1500 = 3000 cm-1

Middle of the action

Pre

dis

s. Y

ield

, C

alc.

In

t.

N OH3C

H3CH H

N

mmmzmnmmymnmmxmnn zmLymLxmLQ

1,;,;,;

2

,H;

2

,H;

2

,H;H; znynxnnLLLP

Theory Take 1: Bright State – Doorway State Model

• Couples bright states (i.e. fundamentals) to doorway states (i.e. 2×vi or vi + vj)

- Use 3rd derivatives in potential to compute off-diagonal elements

0

000

0

00

00

,

22,

11,

,2,1,

jdarkNdNNH

jdarkdNH

jdarkdNH

dNNHdNHdNHjNH

H

H

H

HHH

0ˆˆ20ˆˆ1222

10201

2

1 2

12221

32212

21

3

aaaaQQ

VQQ

QQ

VH

21

221

3

22, 4

1

QQ

VH diNH

63

1

63

1

63

1

3

!3

1N

p

N

q

N

r

rqprqp

QQQQQQ

VH

e.g. Overtone with ψNH = ψ1 and ψovertone = ψ2

N OH3C

H3CH H

N OH3C

H3CD H

N FH3CH3C

H

1800 2000 2200 2400 2600 2800 3000 3200 3400Photon Energy (cm-1)

Pre

dis

soci

atio

n Y

ield

, Cal

cula

ted

Inte

nsi

ty

2×νNDip

2×νNDoop

2×νNHoop

νNH

νNH

νND

Seems to recover the complexity!

Energy of NH(D) fundamentalin initial matrix calculated using 2nd order perturbation theory

How well does this method work with GlyGlyH+?

2200 2400 2600 2800 3000

Blob:

Fewer discretestates:

Photon Energy (cm-1)

Can we sharpen the blob by reducing the DOS?

1200 1600 2000 2400 2800

0

200000

400000

600000

800000

1000000

1200000

D

ensi

ty o

f S

tate

s (s

tate

s/cm

-1)

Photon Energy (cm-1)

26,000

1,125,000

N OH3C

H3CH H

N+

NH

O

OH

OH

H

H

15

O

O

O

OH

Introducing deprotonated oxalic acid…

Cal

cula

ted

Inte

nsity

/Pre

diss

ocia

tion

Yie

ld

O

O

O

OH

1200 1600 2000 2400 2800 3200 3600Photon Energy (cm-1)

Harmonic

𝜈𝐶𝑂 2−

𝑠𝑦𝑚

𝜈𝐶𝑂 2−

𝑎𝑠𝑦𝑚𝑚

𝜈𝐶=𝑂

𝜈𝑖𝑝❑

Where is ?

Cal

cula

ted

Inte

nsity

/Pre

diss

ocia

tion

Yie

ld

x4O

O

O

OH

Harmonic

1200 1600 2000 2400 2800 3200 3600Photon Energy (cm-1)

𝜈𝐶𝑂 2−

𝑠𝑦𝑚

𝜈𝐶𝑂 2−

𝑎𝑠𝑦𝑚𝑚

𝜈𝐶=𝑂

𝜈𝑖𝑝❑

Cal

cula

ted

Inte

nsity

/Pre

diss

ocia

tion

Yie

ld

x4O

O

O

OH

Harmonic

x4Anharmonic

1200 1600 2000 2400 2800 3200 3600Photon Energy (cm-1)

𝜈𝐶𝑂 2−

𝑠𝑦𝑚

𝜈𝐶𝑂 2−

𝑎𝑠𝑦𝑚𝑚

𝜈𝐶=𝑂

𝜈𝑖𝑝❑

~

Where else have we seen broadening associated with H-

bonding?

JPC (2003)

Asymmetric doubly ionic H-bonds

STILL BROAD BANDS BELOW 50 K

νOH,v=0(ZPE)

θ

νOH,v=1

νOH,v’=1

E, c

m-1

UBO(θ)

Potential energy surface for heavy atom motion changes with excitation of OH

stretch

Robertson, et. al. J. Phys. Chem. A 2003

Myshakin, et. al. J. Phys. Chem. A 2003

x

x

x

x

x

x

x x

νOH = νOH’ ν Ro

ck, v

=01

34

2

θ

θ θ

θ = 0

θ < 0

θ > 0

neutral

anionlaserenergy

Kinetic energy of ejected e¯

Bindingenergy

0.0 0.5 1.0 1.5 2.0 2.5EKE (eV)

Shifted curves yield image of ground state vibrational wavefunction in Franck-Condon amplitudes for

vibrational excitation (reflection principle)

Proton Adiabatic Curves

Direction of reaction coordinate:

L. D. Jacobson(Tully Postdoc)

Theory: Take 2

0

500

1000

1500

2000

2500

3000

3500

4000

-0.1 -0.05 0.0 0.05 0.1

Reaction Coordinate (Å)

En

erg

y (c

m-1)

Shared proton vibration is responsive to the reaction

coordinate

Acknowledgements• Funding: NSF and DOE• Mark: Keeping us well fed!• Lectka group (JHU): synthesis• Theory: Anne McCoy and Ken Jordan

Extra Slides

Theory: Take 2

Prof. Anne McCoyThe Ohio State University

Adiabatic separation of OH stretch (qOH) and the other 3N-7 vibration degrees of freedom, leading to:

OH

2

0OH101 OHOH, vv qS q

00OH

0OH

OH100OH1

OH

OHOH

,0,

q

dq

qdq

q

vv

qq

0

0OH

OH

OH00OH1

OH

OHOH

,0

2,

q

vv dq

qdq

q

qq

Transition strength of the OH stretch:

Using the linear approximation of the dipole moment:

And normal mode basis:

Ψ(qOH ,q) ≈ ψ(qOH:q)χ(q)

Randomly displace alongeach of the 3N-7 coordinates(within zero-point motion)and calculate the νOH

1600 2000 2400 2800 3200 3600

Photon Energy (cm-1)

Pre

diss

ocia

tion

Yie

ld/C

alcu

late

d In

tens

ity

O

O-O

O

H

O

O-O

O

D

Captures qualitative breadth quite well!