Adam J. FleisherJustin W. YoungDavid W. Pratt

Department of ChemistryUniversity of Pittsburgh

Internal dynamics of water attached to a photoacidic substrate: High resolution electronic spectroscopy ofβ-naphthol-water in the gas phase.

TA-03

Solvent in Motion• Rotationally resolved

electronic spectroscopy– A tunneling splitting

provides a measure of the barrier to internal rotation.

– This splitting is a function of both the S0 and S1 barriers.

S0 S1

torsional coordinate

cm-1 cm-1

torsional coordinate

Charge in Motion – MG042-naphthol-ammonia 2-naphthol-water

M.J. Frisch et. al. Gaussian 03 (Gaussian, Inc., Wallingford, CT, 2004).

Dynamic charge distribution

Start

Transition State

CW Tunable UV Laser

Argon Ion Laser (7 W)

Ring Dye Laser (85 mW)

Frequency Doubler

Reference Station

I2 tube

Tunable UV laser beam (300 µW)

Monochromator

Interferometer

Molecular Beam Machine

W. A. Majewski, J. F. Pfanstiel, D. F. Plusquellic, and D. W. Pratt, in Laser Techniques in Chemistry, edited by A. B. Myers and T. Rizzo (Wiley, New York, 1995), 101.

Rotationally Resolved Data

30531.3 30533.4Wavenumbers

Full Resolution

B

A

Sim

Exp

2150 MHz

aa

eff PFWAA 2

Inertial ParametersA (σ = 0) B (σ = 1)

S0

Aeff (MHz) 1725.9(1) 1724.9(1)

Beff (MHz) 548.1(1) 548.1(1)

Ceff (MHz) 416.6(1) 416.8(1)

ΔIeff (amu Å2) -1.781 -2.609

S1

Aeff (MHz) 1687.4(1) 1686.3(1)

Beff (MHz) 553.4(1) 553.3(1)

Ceff (MHz) 417.3(1) 417.5(1)

ΔIeff (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 M.J. Frisch et. al. Gaussian 03 (Gaussian, Inc., Wallingford, CT, 2004).

a

b

Origin of Splitting

Energy

S0

S1

A (1)

B (3)

Qualitative Experimental Conclusions:• V2 in S0 is greater than V2 in S1

• The two hydrogen atoms of water must exchange with a 180° movement along the torsional coordinate

Quantitative Measures:• V2 in each state is determined assuming a

rotation about the b-axis of water• Higher order terms (V4, V8) can be

estimated with the aid of ab initio internal rotation pathways

• A-B energy level splitting in both S0 and S1 can be determined

Barrier Heights (I)

F

VsW

WWPF

PFWAPFWAAA

v

aa

aaaa

22

200

201

200

2010001

Calculation of W(2) from available data tables determines V2 in each electronic state.a

S0 S1

ΔAvσ = A01 – A00 (MHz) 1.0 1.1

ΔBvσ (MHz) 0.1 0.1

ΔCvσ (MHz) -0.2 -0.2

tunneling splitting 5673 MHz (0.189 cm-1)

a D.R. Herschbach. J. Chem. Phys. 31, 91 (1959).

Barrier Heights (II)

IF

2

2

g g

g

I

I

2

1

4

2

2

FsNV

a

b

Tunneling Splitting as a Function of α'

Barrier Heights (III)

2-naphthol-water phenol-water a

S0 S1 S0 S1

θRa (°) 14.5 b 29.2 9 9

F (GHz) 437.0 436.8 435 435V2 (cm-1) 206 182 180 130

ΔE(GHz) c 14 19 20 43

a G. Berden, W.L. Meerts, M. Schmitt, K. Kleinermanns, J. Chem. Phys. 104, 972, (1996).b from M05-2X/6-31+G* optimizationc W.H. Flygare, Molecular Structure and Dynamics. (Prentice-Hall, Inc., Englewood Cliffs, NJ, 1978).

Summary• Rotationally resolved electronic spectra of the

2-naphthol-water complex revealed internal motion.

• The results presented are a prerequisite for studying the cluster dipole moment, and therefore the solvent induced charge motion in each electronic state (MG-04).

• The complicated internal motion of water makes the decomposition of solvation interactions theoretically challenging (MG-04).

• Philip Morgan• Diane Miller

Marquette University

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

• Dr. David W. PrattUniversity of Pittsburgh

• Dr. David PlusquellicJB95 development

Acknowledgments (I)

Hamiltonian and Optics

etrrt HHHHH~~~~~

222~cbar CJBJAJH

cbag

Zggze EEH,,

~

2cos12

~ 22 V

FpH t

2)2(

)1(~

ccbbaav

ccbbaavtr

PPPFW

PPPFWH

Inertial ParametersA (σ = 0) B (σ = 1)

S0

Aeff (MHz) 1725.9(1) 1724.9(1)

Beff (MHz) 548.1(1) 548.1(1)

Ceff (MHz) 416.6(1) 416.8(1)

ΔIeff (amu Å2) -1.781 -2.609

S1

Aeff (MHz) 1687.4(1) 1686.3(1)

Beff (MHz) 553.4(1) 553.3(1)

Ceff (MHz) 417.3(1) 417.5(1)

ΔIeff (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

Average Structural Constants

Theoretical Constants a

(6-31+G*)S0 M05-2X

A (MHz) 1725.4 1738.5

B (MHz) 548.1 554.1

C (MHz) 416.7 421.0

ΔI (amu Å2) -2.19 -2.34

S1 CIS

A (MHz) 1686.9 1692.5

B (MHz) 553.4 551.8

C (MHz) 417.4 416.9

ΔI (amu Å2) -2.18 -2.24

aa

eff PFWAA 2

a M.J. Frisch et. al. Gaussian 03 (Gaussian, Inc., Wallingford, CT, 2004).

Barrier Heights (III)

2-naphthol-water phenol-water a

S0 S1 S0 S1

θRa (°) 14.5 b 29.2 9 9

F (GHz) 437.0 436.8 435 435V2 (cm-1) 206 182 180 130

ΔE(GHz) c 14 19 20 43

a G. Berden, W.L. Meerts, M. Schmitt, K. Kleinermanns, J. Chem. Phys. 104, 972, (1996).b from M05-2X/6-31+G* optimizationc W.H. Flygare, Molecular Structure and Dynamics. (Prentice-Hall, Inc., Englewood Cliffs, NJ, 1978).

S0 HF / 6-31+G* Percent of V2 Modified Exp.

V2 (cm-1) 238 --- 206

V4 (cm-1) -28 -12 -24

V8 (cm-1) 6 2.5 5

ΔE(GHz) c 11 --- 16