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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
VH
21
221
3
22, 4
1
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
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
0
0OH
OH
OH00OH1
OH
OHOH
,0
2,
q
vv dq
qdq
q
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