Adam J. FleisherDavid W. Pratt

University of Pittsburgh

Alessandro CembranJiali Gao

University of Minnesota

Charge redistribution in theβ-naphthol-water complex as measured by high resolution Stark spectroscopy in the gas phase.

MG-04

Condensed phase H-bonds

S0

S1

S2

RO-H RO– + H+?

LE CT

Fig. 5 in Schütz, M., Bürgi, T., Leutwyler, S., Fischer, T. J. Chem. Phys. 99, 1469, (1993).

In the gas phase, the cis-2HN-water origin is red shifted by 371 cm-1 from the 2HN origin.

cm-1

OHOROHOHR h32

Fleisher, A.J., Morgan, P.J., Pratt, D.W. J. Chem. Phys. 131, 211101, (2009).

Gas phase H-bonds

2-HN-water

Field free 2HN-water (TA-03)

B

A

Sim

Exp

2.1 cm-1

2140 MHz

Stark cell and collection optics

cbag

Zggzs EEH,,

~

30901.4 30904.7 cm-1

0.04 cm-1

0 V/cm

846 V/cm

1776 V/cm

Stark effect in 2-naphthol

Fleisher, A.J., Morgan, P.J., Pratt, D.W. J. Chem. Phys. 131, 211101, (2009).

2-HN-water Stark spectra

2 cm-1

0 V/cm

169 V/cm

846 V/cm

2HN-water Stark splitting

0 V/cm

169 V/cm

846 V/cm

0.04 cm-1

Results

State Bare Molecule H2O NH3

Ground 1.01 D 4.00 D 3.89 D

Excited 1.17 D 4.66 D 4.94 D

Qdct ctinducedsolventsolutetotal

In 2HN-H2O,Q = 0.07 e in S0, and Q* = 0.10 e in S1

Dipole decomposition

Fleisher, A.J., Morgan, P.J., Pratt, D.W. J. Chem. Phys. 131, 211101, (2009).

This results in a 323 cm-1 calculated red shift (371 cm-1 in experiment).

Static vector model

solutesolventinducedcharge transfer

BLW-ED method

Scheme 1 in Mo, Y., Gao, J., Peyerimhoff, S.D. J. Chem. Phys., 112, 5530 (2000).BLW-ED reported using B3LYP/6-31+G* (geometries were optimized using M06-2X/6-31+G*).

S0 c2HNA(cm-1)

BLW|%|

static|%|

c2HNW(cm-1)

BLW|%|

static|%|

ΔEr +420 ?

ΔEstat -730 20 15 ? ? 22

ΔEpol -980 27 5 ? ? 14

ΔEct -1900 53 80 ? ? 64

ΔEint -3200 ?

ammonia, water

β-naphthol

Dynamic charge distribution

HF/6-31+G* optimization of 11 points along a path exchanging the two hydrogen atoms of water.

Dynamic charge distribution

Start

Transition State

Induced charge motion

… produces a large change in the charge distribution of the molecule to which it is attached.

Motion of the water molecular along the torsional coordinate …

Motion of the ammonia molecular along the torsional coordinate …

… produces little change in the charge distribution of the molecule to which it is attached.

HF/6-31+G* optimization of points along a path exchanging equivalent solvent hydrogens.

Induced charge motion

Time-varying dipole field (II)

2

0

2 V

V

2

0

2

)coordinate (torsional

• A static model of energy and dipole moment decomposition based on electrostatic contributions was used to explain the experimentally observed red shift in 2HNW.

• The block-localized wavefunction energy decomposition (BLW-ED) method was used to investigate electrostatic, induced, and charge transfer interactions.

• Future work on understanding the importance of the time varying nature of the water dipole must be included.– Important to the understanding of condensed phase water systems.

Summary

• Justin Young

• Philip Morgan• Diane Miller

Marquette University

• Ryan Bird• Jessica Thomas• Casey Clements• Patrick Walsh

Acknowledgments

• Dr. David W. PrattUniversity of Pittsburgh

• Dr. David PlusquellicNIST, jb95 development

• Dr. David BorstIntel, Stark development

2

0

2b

a

Time-varying dipole field (I)

2cos12

1cos12

2

1

c

cV

• Torsional TS was optimized using HF/6-31+G*, along with 8 other points between ϕ = 0 – 180°.

• The electric potential at the COM of 2HNW as a function of the torsional coordinate ϕ was fit to 21 data points.

• The electric potential function was scaled by the probability of water being in each position along ϕ using the experimental V2 = 206 cm-1, compared to a barrierless torsion.a

aRazavy, M. and Pimpale, A. Physics Reports, 168, 305 (1988).

H-bond ‘jumps’ in bulk water

Fig. 1 in Ji, M., Odelius, M., Gaffney, K.J. Science. 328, 1003, (2010).

43 NHORNHOHR h

Fleisher, A.J., Morgan, P.J., Pratt, D.W. J. Chem. Phys. 131, 211101, (2009).

Excited State Proton Transfer

S0 S1

µ1 (D) 1.01 1.17

µ2 (D) 1.472 1.472

µind (D) 0.29 0.36

Eµµ (cm-1) -62.4 -113.6

Eαµ (cm-1) -23.6 -43.5

ECT (cm-1) -427.7 -958.0

Ecomplex,rel (cm-1) -513.7 -1115.1

Red Shift in 2HNA

S0 S1

µ1 (D) 1.01 1.17

µ2 (D) 1.855 1.855

µind (D) 0.65 0.75

Eµµ (cm-1) -61.2 -147.4

Eαµ (cm-1) -40.5 -52.3

ECT (cm-1) -183.2 -408.2

Ecomplex,rel (cm-1) -284.9 -607.9

Red Shift in 2HNW

0.04 cm-1

30315.4 30318.6 cm-1

E A

0 V/cm

1269 V/cm

423 V/cm

Stark Effect in 2-Naphthol-Ammonia

Vector Model – 2HNA

2HNW Field Free DataA (σ = 0) B (σ = 1)

S0

A (MHz) 1725.9(1) 1724.9(1)

B (MHz) 548.1(1) 548.1(1)

C (MHz) 416.6(1) 416.8(1)

ΔI (amu Å2) -1.781 -2.609

S1

A (MHz) 1687.4(1) 1686.3(1)

B (MHz) 553.4(1) 553.3(1)

C (MHz) 417.3(1) 417.5(1)

ΔI (amu Å2) -1.741 -2.648

Origin (MHz) 915333681(30) 915339355(30)

# lines 141 458

OMC (MHz) 4.1 5.0

L/G LW (MHz) 9/25 9/25

Rel. Intensity 1 3

A (σ = 0) B (σ = 1)

S0

ΔJ (KHz) 0.17(9) 0.03(3)

ΔJK (KHz) -0.8(7) -1.0(2)

ΔK (KHz) 3(2) 1.2(4)

δJ (KHz) 0.04(4) 0.005(14)

δK (KHz) 5(2) 1.5(5)

S1

ΔJ (KHz) 0.20(9) -0.04(3)

ΔJK (KHz) -1.2(6) -0.4(2)

ΔK (KHz) 3(2) 0.6(4)

δJ (KHz) 0.05(5) -0.02(1)

δK (KHz) 5(2) 1.1(5)

OMC (MHz) 3.7 4.3

Watson A-reduction distortion terms improve the fit of J ≥ 20 transitions, and do not change any other inertial parameters by more than two standard deviations.

2HNW dipole projectionsS0 S1

μa (D) -3.11 -4.09

μb (D) 2.51 2.23

μc (D) 0.0 0.0

μ (D) 4.00 4.66