Ultrafast Hydrogen Bonding Dynamics and Proton Transfer Prosesses in the Condensed Phase

192 Pages·2002·5.467 MB·English

by  Thomas Elsaesser, Huib J. Bakker (auth.), Thomas Elsaesser, Huib J. Bakker (eds.)

ULTRAFAST HYDROGEN BONDING DYNAMICS AND PROTON
TRANSFER PROSESSES IN THE CONDENSED PHASE
Understanding Chemical Reactivity
Volume 23
Series Editor
Paul G. Mezey, UniversityofSaskatchewan, Saskatoon, Canada
EditorialAdvisoryBoard
R.Stephen Berry, UniversityofChicago, IL, USA
John I.Brauman, Stanford University, CA, USA
A.Welford Castleman, Jr., Pennsylvania State University, PA, USA
Enrico Clementi, Universite Louis Pasteur, Strasbourg, France
Stephen R.Langhoff, NASA Ames Research Center, Moffett Field, CA, USA
K.Morokuma, Emory University, Atlanta, GA, USA
Peter J. Rossky, UniversityofTexasatAustin, TX, USA
Zdenek Slanina, Czech AcademyofSciences, Prague, Czech Republic
Donald G.Truhlar, UniversityofMinnesota, Minneapolis, MN, USA
Ivar Ugi, Technische Universitat, MOnchen, Germany
The titles publishedinthis series are listedat the endofthis volume.
Ultrafast Hydrogen Bonding
Dynamics and Proton Transfer
Processes in the Condensed
Phase
editedby
Thomas Eisaesser
Max-Born·lnstitute,Berlin,Germany
and
HuibJ.Bakker
FOMInstituteforAtomicandMolecularPhysics,
Amsterdam,TheNetherlands
Springer-Science+Business Media, B.V.
AC.I.P.Catalogue recordforthis book isavailable from the Library of Congress.
ISBN978-90-481-6206-2 ISBN978-94-017-0059-7 (eBook)
001 10.1007/978-94-017-0059-7
Printedonacid-freepaper
All Rights Reserved
©2002Springer Science+Business MediaDordrecht
Originally published byKluwerAcademic Publishers in2002.
Softcover reprintofthe hardcover 1stedition 2002
Nopart ofthis work maybe reproduced, stored inaretrievalsystem, ortransmitted
inanyform or byany means,electronic, mechanical, photocopying, microfilming,
recordingorotherwise, withoutwritten permission from the Publisher,with the exception
ofany material supplied specifically forthe purpose ofbeing entered
andexecutedon a computer system, for exclusive use bythe purchaserofthe work.
Contents
1
Ultrafast Dynamics ofHydrogenBonding andProton
Transfer intheCondensed Phase
T. ElsaesserandH.J.Bakker
1 Introduction 1
2 OutlineoftheBook 3
2
Infra-Red Spectra ofHydrogen Bonded Systems:
Theory andExperiment 5
S. Bratos,J-CI. Leicknam, G.GallotandH.Ratajczak
1 Introduction 5
2 Classical Infra-RedSpectroscopy 7
2.1 Phenomenological Description 7
2.2 StatisticalTheory ofBand Shapes.
Semi-EmipiralTheories 10
2.3 StatisticalTheory ofBand Shapes.
Molecular DynamicsSimulations 16
2.4 Power andLimitsofClassical
Infra-redSpectroscopy 18
3 Time-ResolvedInfra-redSpectroscopy 19
3.1 Basic Information 19
3.2 FemtochemistryofWater 19
3.3 Phenomenological Description 21
3.4 StatisticalTheory ofBand Shapes 24
4 Conclusions 27
References 28
3
Femtosecond Mid-InfraredSpectroscopy ofWater 31
H.J.Bakker
1 Introduction 31
2 FemtosecondMid-Infrared Spectroscopy 32
2.1 Generation ofFemtosecond Mid-Infrared Pulses 32
2.2 Nonlinear Vibrational SpectroscopyofWater 33
2.3 Aqueous Samples 36
v
vi Ultrafast Hydrogen BondingDynamicsandProton Transfer
3 Energy TransferinLiquid Water 38
3.1 VibrationalRelaxationofHDO:D 38
2O
3.2 VibrationalRelaxationofLiquidH 41
2O
3.3 VibrationalRelaxationoftheO-DStretch
VibrationofLiquidWater 44
3.4 VibrationalRelaxationofWater inAqueous
Solvent Shells 44
3.5 Resonant IntermolecularEnergyTransfer
inLiquidH 48
2O
4 Hydrogen-BondDynamics ofLiquid Water 51
4.1 Experimental Results 52
4.2 Brownian OscillatorModel 55
4.3 Hydrogen-Bondversus Deuterium-Bond
Dynamics 58
4.4 Hydrogen-BondDynamics ofWater inAqueous
Solvent Shells 60
4.5 Relation between Hydrogen-BondLengthand
Local Liquid Structure 64
5 RefmedQuantum-MechanicalModeling oftheSpectral
Response ofLiquidWater 65
6 Conclusions 69
References 70
4
Proton TransferReactions andHydrogen BondinginSolution 73
P.M.KieferandJ.T.Hynes
1 Introduction 73
2 AdiabaticProton Transfer 75
3 NonadiabaticTunneling ProtonTransfer 84
4 ConcludingRemarks 87
References 90
5
Ab-InitioReactionPaths andPotential-EnergyFunctions forExcited
State Intra- andIntermolecularHydrogen-TransferProcesses 93
A.L. SobolewskiandW.Domcke
1 Introduction 94
2 TheoreticalMethodology 96
2.1 Reaction Path Concept 96
2.2 Electronic-StructureMethods 96
3 TheoreticalResults 98
3.1 An ESIHT Model System:Malonaldehyde 98
3.1.1 Hydrogen Transfer 100
3.1.2 Hydrogen Detachment 102
3.2 'Real'ESIHT Systems 104
Vll
3.3 ESIHTinH-BondedMolecularComplexes 106
3.4 AGeneric MechanisticModeloftheESIHT
ReactionandPhotostability 108
3.5 PhotoinducedHydrogenTransfertotheSolvent 109
4 Conclusions 114
References 115
6
UltrafastExcitedState HydrogenTransferinthe CondensedPhase 119
T.Elsaesser
1 Introduction 119
2 ExperimentalTechniques 123
3 VibrationalSpectroscopyofUltrafastHydrogen
Transfer 128
3.1 ResonanceRaman Spectroscopy 128
3.2 FemtosecondInfraredSpectroscopy 132
4 ExcitedState HydrogenTransfer:Transient
ElectronicSpectra 136
5 VibrationalRelaxationandRedistributionInducedby
HydrogenTransfer 143
6 Conclusions 148
References 151
7
ProtonDissociationand Solute-SolventInteractionsFollowing
ElectronicExcitationofPhotoacids 155
E.Pines andD.Pines
1 Introduction 155
1.1 NeutralandCationic Photoacids 157
1.2 AGeneral DescriptionofPhotoacidity 160
1.2.1 NeutralPhotoacids 160
1.2.2 Cationic Photoacids 162
2 KineticProcessesInitiatedby Photoacid Proton
Dissociation 163
2.1 Diffusion-ControlledProtonTransferReactions 163
2.2 ProtonTransfertoSolvent(PITS)from Photoacids 166
2.3 ProtonTransferinBulk Water(The Grotthus
Mechanism) 171
3 HydrogenBonding InteractionofPhotoacids 174
4 SolvationDynamics andHydrogenBonding Interactions
ofPhotoacids 177
5 Summary 178
References 179
Index 185
Chapter 1
ULTRAFAST DYNAMICS OF HYDROGEN
BONDING AND PROTON TRANSFER IN
THE CONDENSED PHASE
Thomas Elsaesser
Max-Born-Institutfur Nicbtlineare Optikund Kurzzeitspektroskopie,
Max-Born-Sir. 2 A, D-12489Berlin, Germany
Huib J. Bakker
FOM Institute for Atomic and MolecularPhysics, Kruislaan 407, 1098SJAmsterdam,
The Netherlands
1. Introduction
Hydrogenbondsare offundamental importanceinnature. Theyare sub
stantially weaker than covalent bonds and cover a wide range ofbinding
energies from about 4 to 40 kJfmol, depending on the local geometry
and the type and strength of interaction between the hydrogen donor
and acceptor groups. This local interaction is strong enough to deter
mine the structure of many molecular systems, such as water, ice, and
macromolecules like the DNA or proteins. On the other hand, the lim
ited strength of hydrogen bonds allows for structural flexibility and for
a 'making and breaking' of bonds which are essential for the function of
such systems. These processes include the transfer of hydrogen atoms
along pre-existinghydrogenbondsand the release ofprotons into a liquid
or protein environment.
Over the last decades, there has been impressive progress in eluci
dating hydrogen-bonded molecular structures. Key techniques are x
ray diffraction now making use of high brilliance synchrotron sources
and highly developed growth methods for (bio)molecular crystals, neu
tron diffraction being particularly sensitive in measuring hydrogen po
sitions, and nuclear magnetic resonance providing insight into local in
teractions through chemical shifts of the resonance signals. In general,
1
T.ElsaesserandH.I.Bakker(eds.),
UltrafastHydrogenBondingDynamicsandProtonTransferProcessesintheCondensedPhase,1-4.
©2002KluwerAcademicPublishers.
2 T. Elsaesser, H.J. Bakker
the time-averaged positions of atoms and functional groups are derived
from such measurements with a precision ofa fraction of a bond length.
The structure of macromolecules like DNA, myoglobin and a number of
large proteins are rather well understood. In contrast, the knowledge
of hydrogen-bonded liquid structures which are characterized by a high
degree ofdisorder, i.e. a complex distributionof local geometries, isstill
limited, even for liquids like water.
On a microscopic level, the functioning of hydrogen-bonded systems
is much less understood than their structure. The understandingof this
functioning requires knowledge of the dynamics of hydrogen bonds and
proton-transfer processes, both extending over many orders of magni
tude in time. Among the fastest events are the nuclear motions in a
hydrogen bond, e.g., the vibrational excitations of the hydrogen donor
group andthechanges oftheoverall lengthofthehydrogen bondinduced
by low-frequency degrees of freedom. These events occur on ultrafast
time scales ranging from 10 fs up to several picoseconds. Elementary
reaction steps like the formation and breaking of hydrogen bonds, and
the transfer of protons or hydrogen atoms, can proceed as fast as these
nuclear motions, However, these processes can also take much longer in
cases where the local potential energy surface displays a barrier. The
wide range of time scales of the dynamics of hydrogen-bonded systems
together with theirstructuralcomplexity and/or disorderpresents a ma
jor challenge for both experiment and theory.
In principle, information on dynamics can be derived from the line
shapes ofstationary absorption and emission spectra related to elemen
tary excitations of a hydrogen bond, i.e, from steady-state linear spec
troscopy in the frequency domain. For most hydrogen-bonded systems,
however,complexlineshapeswitha combinedhomogeneous and inhomo
geneous broadeningare found that cannot be analyzed with steady-state
spectroscopy. As a result, combinations of frequency and time-domain
spectroscopic techniques, like multidimensional nuclear magnetic reso
nance using pulse sequences and time-resolved optical spectroscopy, are
required to investigate the dynamics of hydrogen bonds. The fastest
events that can be accessed directly by nuclear magnetic resonance,
have a characteristic time scale of a few nanoseconds. With optical
spectroscopy employing ultrashort pulses, it is even possible to study
events on a time scale of a few femtoseconds.
In recent years, ultrafast optical spectroscopy has developed into an
important tool to study the dynamics of hydrogen bonds and proton
transfer reactions. Ultrafast spectroscopy addresses the nonlinear opti
cal response of the system in the time-domain at a time scale between
a few femtoseconds and approximately 10 picoseconds. These studies
Ultrafast dynamics ofhydrogen bonding 3
provide information which cannot be obtained with linear absorption or
emission spectroscopy. For instance, ultrafast photonecho or, in general,
coherent multidimensional spectroscopy, allows for a separation of ho
mogeneous and inhomogeneous broadening of lineshapes and for a mea
surement of electronic and other couplings between functional groups.
So far, ultrafast spectroscopy of hydrogen bonds has been concentrated
mainlyon two areas, nonlinear vibrationalspectroscopy in theelectronic
ground state and studies of photoinduced proton-transfer processes in
electronically excited states.
Parallel to the experimental progress, theoretical concepts and meth
ods for describing the reactive and nonreactive dynamics of hydrogen
bonds have reached a high degree of sophistication. ab-initio molecular
dynamics simulations based on density functional theory have become
an important tool for analyzing hydrogen-bond dynamics in liquids. In
addition, different types of transition-state and quantum dynamics the
ories have been developed and applied to study hydrogen and proton
transfer processes. Moreover, a powerful theoretical framework based on
density matrix and/or Green's function formalisms has been developed
for describing the nonlinear optical response of molecules in condensed
phases. The combination of ultrafast nonlinear spectroscopy with these
new theoretical approaches has led to important new insights into the
physics and chemistry of hydrogen bonds.
2. Outline of the book
In this book, the recent progress in the research on ultrafast dynamics
of hydrogen bonds and proton transfer is reviewed. The main emphasis
is on optical studies of hydrogen bonds making use of nonlinear time
resolved spectroscopy in the ultrafast time domain. In the following 6
chapters, bothstate-of-the art theoryand recent experimentalresultsare
presented on a tutorial level. Chapters 2 to 4 deal with dynamics in the
electronicgroundstatewhereas excitedstatehydrogenand protontrans
fer are discussed in Chapters 5to 7. In Chapter 2, infrared spectroscopy
ofhydrogen bonded systems is reviewed, in particular addressing steady
state and time-resolvedstudies ofO-H stretchingbands. Chapter 3gives
an overview of ultrafast vibrational spectroscopy of water, mainly con
centrating on the coherent and incoherent dynamics of 0-H stretching
excitations. Hydrogen and proton transfer in the electronic ground state
are discussed from a theoretical point of view in Chapter 4, giving a mi
croscopic description of these processes in which the strong influence of
the solvent is accounted for. In Chapter 5, ab-initio calculations of ex
cited state intra- and intermolecular hydrogen transfer are considered,