exploring solvent shape and function using mass- and isomer-selective vibrational spectroscopy...

EXPLORING SOLVENT SHAPE AND FUNCTION USING MASS-

AND ISOMER-SELECTIVE VIBRATIONAL SPECTROSCOPY

Special thanks to Tom, Anne and Terry

Outline

Ar-cluster mediated trapping of reaction intermediates as size-selected cluster ions

Reaction motifs in water splitting Characterization by vibrational predissociation spectroscopy Network-dependent activation of water in covalent bond

formation: NO+ ·(H2O)n

Instrument modifications to access electrosprayed ions Ring closure mechanics of dodecanoic acid conjugate anions

Yale

Rachael Relph

Mike Kamrath

Chris Leavitt

Tim Guasco

Arron Wolk

Krissy Breen

Helen Gerardi

Prof. Gary Weddle (Fairfield)

AFRL Cambridge

Dr. A.A. Viggiano

Univ. of Pittsburgh

Prof. Ken Jordan

Dr. Daniel Schofield

Ohio State

Prof. Anne McCoy

Yale

Prof. John Tully

Dr. Ryan Steele

Experiment Theory

Eldon Ferguson

RachaelMike

Ben, PhD 2010, Now with

Schwartz, UCLA

Gary Tim

Krissy HelenThursday talks

Yale Solar Group-small biomimetic catalysts

O H

CO2-

N

N

N

MnO

OMn

N

N

N

L

L-O2C

-O2C

-O2CCO2-

CO2-

Oxidn.LMnV=O H2O

O2 + 2H+

3-

IV IVor

LMnIV-O•

MnO2Mn OH2III -e-,-H+

Mn OHIV -e-,-H+

Mn O• Mn OH2O,-H+

IV III

(1)

(2)Mn(OH)2Mn

O2

H2O, -e-

MnO

OMn

N

N

IV IVOL

N

N N

NO

SO3-

-SO42-

thermalMn

O

OMn

N

N

IV ? OL

N

N N

N

Our known compound

oxo or oxyl?

H2O,-H+

MnO

OMn

N

N

IV IV OOHL

N

N N

N

observable?

(3)

(4)Mn

O

OMn

N

N

IV IVOL

N

N N

N MnO

OMn

N

N

IV IV LN

N N

N

Ar+

-Mn2O2(terpy)2LIV

IV

H+

III II

“Harnessing the power of photosynthesis to make green fuel”

Making the O-O bond

• Very high oxidation states put water in unusual chemical environment

• Cooperative, complex reaction coordinate!

• Proton removed and O-O bond forms

OVIr

OHIVIr

-H+/-eˉ

+

OHH

- +

OHH

Large shifts in excess proton-

based vibrations:“Frozen

snapshots” of diffuse ir signature

of free proton in dilute acids

H+(H2O)n∙Ar spectra

Spectral signatures of mobile protons

Headrick, M. A. Duncan,MAJ,

Science, 308, 1765 (2005),

N=O+

O

H

H

N=O

O

H

H

solvated nitric oxide solvated nitrosonium

clusters provide a controlled environment to titrate the extent of proton transfer

-e-

N=O

OH

pKa drop

solvation in liquid water leads to formation of

acid

low dielectric allows onlypartial release of proton

oxidation

N=O

O

H

HB: +

Getting started…2009

Proton-coupled covalent bond formation

proton transfer

H

+O H

H

NO+(H2O)n ∙ Arp + H2O → NO+

(H2O)n+1 ∙ Arq + (p-q) Ar

Cryogenic Ion Chemistry

Rational preparation of reaction intermediates using Ar cluster-mediated condensation

NO+(H2O)n

H2OHONO + H+(H2O)n

NO+(H2O)n + H2O → HONO + H+(H2O)n

Atmo reaction, Ferguson ‘71Okumura, ‘93

Reaction coordinate is solvent shape

Application to the nitrosonium hydrates

1 keVelectron

beam

NO+ ∙ Arm + H2O → NO+(H2O) ∙ Arp + (m-p) Ar

NO+(H2O) ∙ Arp + H2O → NO+(H2O)2 ∙ Arq + (p-q) Ar

H2O

kV

NO/Ar

time of flight

NO+ (H2O)2Ar

NO+ (H2O)4Ar

NO+ (H2O)3Ar

Ar12+

NO+ Ar9

1 keVelectron

beam

T.O.F.

Nd:YAG pumped OPO/OPA

600 – 4500 cm-1

reflectron

MCP detector

H2O

kV

NO/Ar

NO+(H2O)n ∙ Arp + h → NO+(H2O)n ∙ Arq + (p-q) Ar

Structural characterization by Ar tagged ir spectra

increasing charge on solute

1400 1800 2200 2600 3000 3400 3800

Photon Energy, cm-1

NO+HONO

Distinct spectral regions for solute and solvent response

Solute response

ReactantProduct

H9O4+ Free OH

increasing charge on

solvent

Reactant

Solvent response

Product

NO+(H2O)n + H2O → HONO + H+(H2O)n

increasing charge on

solute

1400 1800 2200 2600 3000 3400 3800

Photon Energy, cm-1

H9O4+NO+

Pre

dis

soci

ati

on

Yie

ldbend

Free OHHONO

increasing charge on

solventNO+ · (H2O)1

NO+ · (H2O)2

ba

gNO+ · (H2O)3

HONONO+ · (H2O)4

Reaction complete

Isomers?

Argon-solvated Isomer IArgon-solvated Isomer IIIsomer I or II fragment induced by pump laserIsomer II fragment induced by probe laser

Sig

nal

Time of Flight, ms

ion beam

pulsedvalve

1 keV electron gun

reflectron

hnpump hnprobe

coaxial TOF

drifttube

MCP iondetector MCP ion

detector

reflectron

Nd:YAG pumped OPO/OPA

600 – 4500 cm-1

±1.5 keV

Nd:YAG pumped OPO/OPA

600 – 4500 cm-1

Isomer-selective Spectroscopy: Development of MS3 IR2 technique in 2008

1900 2100

b

a

g

2300

Disentangle high energy bands in DR scanning mode

2600 3000 3400 3800 4200

Pre

dis

socia

tion

Yie

ld

Photon Energy, cm-1

Probe

Probe

3640 3680 3720 3760

Ion

Dip

Sig

nal

Photon Energy, cm-1

2600 3000 3400 3800

3600 3800P

redi

ssoc

iatio

n Y

ield

2400 2800 3200 3600 4000

probe *

probe ‡ *

‡

A few bands still hopelessly overlapped!

Deconvolute using covariance behavior

1900 2100

b

a

g

2300

Three embedded patterns

2600 3000 3400 3800 4200

Pre

dis

socia

tion

Yie

ld

Photon Energy, cm-1

Probe

Calculated isomers of NO+·(H2O)3

DE=2.4 (1.9)DE=0.0 (0.0)

DE=4.3 (4.0)DE=2.6 (2.2)

DE=3.4 (1.2)

MP2/aug‑cc‑pVTZ

kcal/mol(ZPE corrected)

Three observed by hole burning

increasing charge on

solute

1400 1800 2200 2600 3000 3400 3800

Photon Energy, cm-1

H9O4+NO+

b

Pre

dis

soci

ati

on

Yie

ld

bend

Free OH

a

HONO

g

increasing charge on solvent

3-a3-b3-g

Strong correlation between solvent and solute response to changing solvent coordinate

Arrangement stabilizes charge on shared protons

γ motif with two waters in second solvation shell most reactive

+

Hydrated NO+

Electron flow

OH

N

H

O

3-a 3-g3-b

Intra-cluster charge-transfer (neutralization of NO+) strongly dependent on shape of attached

water network

Electron density difference contours upon ion hydration

(fixed water network at product geometry)

Explicit, molecular level solvent coordinate for reaction

Relph et al., Science, January 2010

parent ion

800700600500400300Mass (amu)

mass = 483

“Cryogenic ion chemistry” with water splitting catalysts?

Cryogenic Ion Chemistry

Rational preparation of reaction intermediates using Ar cluster-mediated condensation

• Standard approach: Ar tagging in supersonic expansion

– Argon Heat of Evaporation: 500 cm-1 – Only works on small systems where vibrational degrees of

freedom can be quenched by Ar during the expansion

Challenge: Vibrational cooling of large systems

X·Arn X·Arm + Arn-m

NO+ · (H2O)3 · 7 Ar NO+ · (H2O)3 · Ar + 6 Ar

3N – 6 = 27 ~ 9 Ar atoms

3N – 6 = 135~ 50 Ar atoms

Tagging with H2

Xuebin Wang at PNNL

{ONLY the dianions tag with H2 }

Thank You Lai-Sheng Wang and Xuebin

Wang!

-O2C(CH2)12CO2- n H2

RF only quadrupoles

Heated copper block

1st skimmer

2nd skimmer

aperture

Octopole ion guide

90° quadrupoleion bender

H2/He filled 3-D quadrupole ion trap with temerature control to 8 K

Octopole ion guidewith Einzel stack

Electrospray needle

Instrument construction2009-2010

Thanks: Tom RizzoScott AndersonDieter GerlichXuebin and Lai-Sheng

He/H2 buffer gas

72 74 76 78

Time of Flight (ms)

30 ms

50 ms

40 ms

20 ms

0 ms

doubly-chargedparent

RF

RF

Pulsedvalve

Ions in Ions out

Paul Trap

H2 adduct formation in a 3-D Paul trap:Pulse cooling gas and delay extraction after pump out

10 ms gas pulse

Delay to extraction

10 K

Starting with a known standard

–O2C(CH2)6CO2– · Kr

1200 1600 2000 2800 3200 3600 4000

CO2 sym. stretch

H2 predissociation spectroscopyOkumura & Lee 1990

Photon Energy, cm-1

H2 stretch

B3LYP/6-311++g(d,p)Calc

ula

ted Inte

nsi

tyH

2 P

redis

s. Y

ield

–O2C(CH2)10CO2– · (H2)10 + hν → –O2C(CH2)10CO2

–· (H2)5 + 5 H2

CH stretches

Dodecanedioic acidO

OH

O

HO

C-O stretches

H2 attachment site

1200 1600 2000 2800 3200 3600 4000

Photon Energy, cm-1

H2 P

redis

s. Y

ield

Calc

ula

ted Inte

nsi

ty

B3LYP/6-311++g(d,p)

CH stretches

H2 stretchCO2 sym. stretch

Free H2 CO2 asym. stretch

Packing of H2 molecules

n = 10

Relatively sharp, red-shifted band (by 250 cm-1)Many molecules in first solvent shell?

B3LYP/6-311++G(d,p)

Can fit 8 H2 around each CO2 group

Where the H2 sticks in the di-anion

1200 1600 2000 2800 3200 3600 4000

Photon Energy, cm-1

H2 P

redis

s. Y

ield

Calc

ula

ted Inte

nsi

ty

B3LYP/6-311++g(d,p)

H2 stretchCO2 asym. stretch

CO2 sym. stretch

CH stretches

Where the H2 sticks in the di-anion

1200 1600 2000 2800 3200 3600 4000

Photon Energy, cm-1

H2 P

redis

s. Y

ield

Calc

ula

ted Inte

nsi

ty

B3LYP/6-311++g(d,p)

H2 stretchCO2 asym. stretch

CO2 sym. stretch

CH stretches

Extending H2 tagging to the singly-charged species

[CO2(CH2)10CO2H]-·nH2

T=11 K

224 226 228 230 232 234 236 238 240m/z

n =0 1 2 3 4

72 74 76 78Time of Flight (ms)

n = 14many peaks but only doubly-

charged species tags

1000 1400 1800 2200 2600 3000 3400 3800 4200Pre

dis

soci

ati

on

Yie

ld

Photon Energy, cm-1

Calc

ula

ted Inte

nsi

ty

a)

b)

c) free H2

stretch

free OH

sharedproton

CH stretches

C=O stretches

CH backbone

Missing free OH signals ring formation

C-O bands reveal asymmetrical internal H-bond

C=OBlue shift

C-Ored shiftCO2ˉ bond order

1.5

800 1200 1600 2000 2800 3200 3600 4000

Photon Energy, cm-1

C-O bands reveal asymmetrical internal H-bond

Carboxylate is intact

800 1200 1600 2000 2800 3200 3600 4000

Photon Energy, cm-1

C-O bands reveal asymmetrical internal H-bond

Carbonyl emerges

800 1200 1600 2000 2800 3200 3600 4000

Photon Energy, cm-1

C-O bands reveal asymmetrical internal H-bond

C-OH lost in CH2 background

Going to need a better mass spec

• Current mass spec only has unit mass resolution at 500 AMU

• Photocatalysts have metal centers with multiple isotopes

ex: 191Ir (37%) and 193Ir (63%)

• With doubly charged species loss of a single H2 may be difficult to detect

The next generation: ICR

Delivery date: June 7

Etienne Garand, PhD NeumarkDelivery date: July 1.

Resolution 450,00016 cm bore (77 K cell, Williams, Berkeley)

• Observed explicit solvent coordinates facilitating covalent N-O bond formation

• Implemented cryogenic ion source into triple-focusing tof mass spec to study photoactive catalysts from the Yale Solar Group

• Next phase of construction: ICR

Conclusions

Thank you