Far infra red circular dichroism and molecular dynamics

Journal ofMolevular

L/qu/ds,

47

109

109-119

(1990)

Elsevier Science Publishers B.V., Amgterdam

II~II:R~~:~ P E D

FRR

CIRCULAR

DICIIP-OISI~

I-I .

I.l.

f~or tie I |

E

At,tO

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LII11 v e t

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] thac~l

D fI.IAI'ITCS.

.

si

t ~ ,

Center

iq',~

HOLECULAP.

,

.

I ~853. LI.S.¢..

(Received

15

December

1989)

ABSTRAC [ [ t

power

far

inf}-a

from l ~_

of

rotation ar

a~d

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right

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statistical

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aEhil-a|

.

field.

| 014

Cil'c|J[ar

differential

dichrolL'J~in

ab~orpt]on

~lectromagnetic

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blrefrinqent

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left

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sI;i-uctur~l

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determlned

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provides

respond

radiat]o~ data;

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example,

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rotational

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dichroism,

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C9--I~] and

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molecular

dynamics

on

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in

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the

power

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depend time

are

rotator~-

ensembles. computer

on

In

(I~.

circular

the

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functions

sample, section

suggested,

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~imulation

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(e)

some

based

on

in

in~ra

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discus~e~ the

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po~er

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section

absorption

molecules.

details

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active

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the

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role

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[.

FUNDAIIENTAL An

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ensemble

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blrefringent

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plane

radiation

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the

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electromagnetic

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the

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the

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the

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the

dynamics

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the

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the

the

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m

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ruination

molecular

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.

total

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as

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with

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the

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dependent

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structurally

the

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of

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equations

rotation

described

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chiral

of

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birefringent

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dependence

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antisymmetric of

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reveal

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of

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vector

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classlcal

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21

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b~,

the

propagation

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frequency

thls

sho~,n

magneto

electromagnetic In

through

the

weaker

fundamental

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measured

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the

I i teratt=r~

Infra'red

co-llnear ~ork

greatest

visible.

~mith

the

govern

Far

the

electromagnetic

field.

(1)

have

the

can

dielectric

established

to

field

molecules,

magnetic

in

the

Recent

a c c o m p a 1 ~ i e d by

achiral

#:notch

mtl-elngth

polarised

~ith

sample

.

effec~ [here

electric

ore

113 2.

I.

F.

R.

DICHROISM AND MOLECULAR D , I I A I - I L C S

Eqns. circular the

molecular

frequency the

(2)

5 ~ BhoL-~ t h a t angle

of

dynamics

of

red

the

e~planation red

~!e ¢ 0 n s i d m r

.p~r~'a~zis~;(J' ~'~|~

rotation,

and

of

dichroisa~

of

firsElv

fli~

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to

the

~,r . ~ h , i / ~ : f . & ~ / j ~ "

ensemble,

lhe

e~ampl~,

is

in

sect ion

we

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91 .'e1~ b ,

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polarts~d

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fa,-

measurLn~

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t-ight

ensembie

an

fo.-

far,

circular-Iv

of

~P.)

con;ple,: permitti-,itv

r~l~t~,#

{

22

correlation

molecular

¢~i_d ~.~#01" ~ , # ~ o r P { i ° n

on

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t.he c a ~ e o f

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o~ ¢ , ~ l ~

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(

and

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refraction

]

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the

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f,Jnctlo=~

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coefficient

ts

._Eo 4~he r o t a t i o , ~ a l

Similart,.,

related

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through

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4unct,o,, (7)

Con~ider

ne~:t

p o l a r isd;d r a d i a t i o n

the

vJith

Interactlo,1

the

absorp.tion,

~omewhere in mol'ecules. dichroigm

the

4In and

absorption

no

optical

infra

iB is red

the of

simulatlon~

for

activit'/,

molecules and

the

a~l,l r i g h t

far

this

e fa,-

i=if,-a

be

fovn, l

,nust

of

rhira]

there

Is

infra

no

red

power

polarlme,!

) betvteen the

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and

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{23 -

arid

circularl~

difference

is

We o b s e r v e

ensemble dynamics

achi~-al

l~t

cil-cularl-v

pm=-mlttivit'/

e.-:pianation

the

identical.

The a n s w e r computer

of

measured with

14hat f~r

nature

complex

the

enBembl~s of

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the

anti

left

sam~ e n s e m b l e .

DIFFERENT ~ t @ q u e n c v d e p e n d e n t r~d' p0wer

of

26

)

,-ecent

which

ensemble

dynamics

molecules? molecular

show

that

th~

dynamics statistical

i,l

114 correlation

between

velocity This

(-TL-~.)

occurs,

principal

changes

however,

molecular

laboratory by

centre

frame

symmetry

30},

~;heoretical

~tatistical

symmetry

C1

correlation

eKist

for

the

(S)

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in

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radiation

in is

th~

,llrectly

the

allo~Jed

computer

{

}1 } .

shows

that

nine

in

are by

zero

~il

~nd

Group in

elements

's,

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confined

dependent

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the of

th~

~ig~

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mixture.

exclusively

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the

net

indirectly,

itB

left),

the

time

in

dynamical

to

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,lerivatives forcl~

and

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and

net

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the

torque

on

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,

to

power

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angle

of

an

measure

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po,-ler anll

circularly

when

c.c.f,

the

abBo,-ptio,~

an

ensemble

of

polarized

identical

sEJitching u n , le,-

red

enantiomer~

in

molecular

that

general,

provide

i,lfra

measured

reveals

right

its

~ith

presence

observatlonal

"antennae",

the

permanent

dipole

derivative.

manifestation

infra

(R)

but

The

We c o n c l u d ~ components

of

therefore,

momemt a n d

far

different

radiation.

through

the

is

responsible

of

structural

,tIchroism.

experimental its

~(~_~o)>,

c.c.f.

effect

coefflci~nt;

for

this

Conversely of

i~

;-I i i ' l e

the

re~ulting the

the

,luantitatively the

an, l

chlrality°

measure

2)

th

in

dielectric

latter

~ffect

in may

of

the

t~rm~

of

I )

lobs;

3)

the

{ 3 ),

which

be

the

rotation. This

that

group

en~ntiomers

ensemble

or

conditions

to

z )

appear

(right

unpolarized

far

(R)

c.c.f.

y,

not

the

(c.c.f.)

beha--'iour

frequency

coefficients

used

30 )

point

by

molecule. The

only

( 27 -

angular enantiomer~.

defined

observed

mechanic~ chiral

( ~: ,

been

or

"s~itching"

frame

thesame

not

and

correlations

5mal I

vanishin,.t

such

anll

luch

)

chiral

z)

very

Function

enantiomer,

related

b~

y.

inertia,

have

to

ensemble

Furthermore,

(S)

appear

(x,

where

( ~/

diffusing

frame

Z).

but

velocity

between

the

Y,

and

lowest

mass

momwnt~ of

simulation,

Cro~

sign in

(X,

t27 -

of

far

infra

J

conclusion red

i9

dlchroism

reinforced It,

the

from poE,e r

eqn.

absorption

sho~s

coefficient

1i5 is

directly

scalar

p,-oportio~al

component of

mechanical electric the

the

origins

same s y m m e t r y

as

molecular

rotation

dipole

classically

is

momentum, so type the

q ~i

provide~

in

the

~

l

~

~

laboratory

~

>

to

which it

is

dipole to

~

in

a fundamental

again

opposite

and

be built

result

of

the to

switching

by

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~.|irectly

through the

angular

re, l ,lichroi~m

computer

a

in

{32,

~3~

the

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expectation

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general

of

correlaterl

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magnetic

one enantiomer

infra

up

ham

between

correlation

type

velocltv

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the

from

Far

this

is

This

molecular

s~itch

know,~ f r o m

leading

to-~

can

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linear

a

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of

molecular

function

cro~s

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the

Furthermore

sae a

information

frame

correlated is

the

Finally

o

correlation

to

of

elements.

p,-oportional

average

who~e q u a n t u m

a product

whose element~

electric

laboratory

it

matrix

cross

ensemble

tensor~

translation.

function,

simulation.

appropriate

make

we e x p e c t

specific

correlation

that

the

~--~(~)~

opposite

)

dipole

and

that

an

Rosenfel,l

( 1, 2

magnetic

and

to

opposite

that

~

is

enantlomers.

for

al[

~tructu|~a|ly

red

dichroism,

This

chiral

ensembles.

3.

EXPEPIMENTAL D E T A I L S . We h a v e

e×p~rlmental of

ly

isolating

solely

argued

the

of

Use o f

effect

Of

for

th~

laser

Tunable

Tunable frequencie~

lasers

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the

switchin

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is

near

and

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no~

of

a

strength

available the

far .

an, l

The o u t p u t

ll,lui,l of

if

observable

an e l e g a n t

c.c.f.'s

metho, l

~hich

section

conditions

are

we s , J g L l e s t using

spectroscop', o

Lasers.

8~) cm - I

through

is

this

e>-perimental

accurately

thickneGs

In

9

Interferometric

throughout

initially

rotation

inf~-a

Submilllmetre

lines

optical

the and

strongest

possible

far

optlmised

optlmislng

submillimetre a)

under

responsible

methods

that

machined

which Infra this from

red

~houlfl the

li,lul,.l

tho,Jsands of

many ~ p o t

r~nge. be

laser-

vertical

a sample cell or

pro,lure

~ire

degrees

the

chosen is

plane

grid

containing crystal

One o f

with p~r

the a

ma~imt, m

Visible

metre.

The

116 rotation

of

second the

th~

wire

grld

detector

polar(set

the

b)

of

the

the

of

provide

rotation

thickness

above

as

in

angle

the

the the

a

dependence

of

angle

baseline should

signal

be

a

,Iri,t

sampL~ is

to

repeated

eliminate

linear

an, l s h o u l , l

function vanzsh

laser

optical

at

.

oF

and

different the

~ith

seconq! ~ire

procedure

enantiomer, at

the

function

The

a

until

of

gives a)

Measurements

red

must

utilise

separate

the

and

the

circularly

hel Ical

has

(high

broad

by

far

a

infra

at

no~

red,

designed

infra

thus

A further

in

frequencies

activit$

.

{

interferometer,

refractiv~ modulator

index as

has

by

a

kH~- [ 6 -

}

modulator

optimisln,! and

Naris up

et an

al.

can

area

t-lch

of

information

35

}.

~here

the

an{|

which

¶li.,~s

directly,

describ~,!

is

using

already

(helium

is

a for

the

structure~. transparent

mate0-iai

is

reach

far

h~ld

fre, luency

germanium ,lichroi~m.

infra in

,

j,-~

source

Rollin)

infer-mat(on

,!ispersive

sample

to

left

cooled

probably in

using

complexes.

molecular which

cm -1

circular

chlral

beam ,li\-i,!er

d~t~ctor

to

~2ibrational

chlral

of

of

mo,lu]ator

right

on

wor~

300

piazza-optic

information

must

components

to

far

method

i .e.

~le, lant

data

from

spot

ban, l

this

,lirectiy,

Th~

83.

~t

breast

However,

provided

an,_! s l m p l ~

,

}.

polarized

radiation

(34

information ~ith

radiation

i-Jith

be

opening

source

interferometrv

and

Z2

rail(at(on.

provided

mercury)

Instrum~nt red,

8 )

band

germanium

pressure

{

circularlv reel

interferometer

macromolecules~

utilising

the

{ 6-

polar(sad

dlchrolsm

left

infra

co--wo,-kers

probe

provides

supplemented

polar(sad

and

far

7199

laser be

interferometrv

right

l'lafle

a

~houlM

circularly

polar(sad

Nicolet

using

and

Mlchelson

plane

switch

method

only,

infra

the

first

measured

Interferometry The

By

The

rotation

provitle

is

rotated

frequency.

to

frequency

frequencies

a

th~

radiation

is

repeats,!

mixture

mixture.

the

The

to is

output

which

measuring

effects. ~ample

,-acemic

b}

respect

racemic

spurious

the

maximisedo

e~:periment

thlck~ess; for

of

polar(mar

is

~;Ith

The

plane

one

th~

far

{ 22 } . re, i arm

{lepton,l e n t

piazza--optic

,

of

tt,e

117 DISCUSSION Far

Infra

laboratory

red

dichrolsm

and

moving

correl~tlon red

power

are

the

functions absorption

molecular

correlation th~

frame

switching Fou~-ler

anti

source

of 8n

circularly

polaris~d

~nantiomer

accompanied

peak

by

frequency

molecular

Y,

molecular between cross an

which

,lipol~

(X.

Z).

spectrum.

again

of

clrcula~-

race,nit also

functions

of and

for

a

greater

particular the

infr~

.

The~e

dipole c.c.f.

'5

red

are

power

an, l

ri,iht

,-ed

and

mode~

chlral

~lichroilm.

time

case

is

cross

chir~I

I iquid.

obser

can

The

be

any

of

table

usetl

higher

6 -

;

there

~h~

i~

vibrat

"hidden

b~

12

cancel,

information

general

{

~i I I

,Jepen~lent.

that o,~

these

there

correlation

t-le c o n c l u d ~

In

~n

of

correlatlon

fre~luency

lltlui~I,

~-~d

functlon r~ult

If

information

state

infra

~nant iomers

is

are

.-ibratlonal

li,iuiH

the

the

cross

already

~,hich

animated.

the

Raman state

the

correlation

bett;een the

[ i,lui,l

i~

t~-a~slation.

these

which

the

around about

thls

dn~-:t,,r E .

a

in

spectrum

provides

simulated

infra

statistical

of

~he,-e

correlation

proper

Its

s1~n

b~

vibrational

"antenna'" far

infra

left

the

which

in

the

c|ichroism

dichroism

computer

far

shoulders

and

~houlders

"ba~ellne"

the

an, l

gene~al

s~Itch

circular

I :

antenna

rotation

vibrational

that

the

information

involving

correlations the

and

~witchin,!

with

in

into

contain

moment In

vibration,

on

,letai

fu~ed

The

dynamics

effect

between

the the

permittivit~

27 }

The

,n~asure,l

absorptions

and

dynamics.

transition frame

.

on are

of

radiation.

rotational

broad,ned

{

influence

"s

comple×

re~pecti-'~1>

Lllbratlonal

b~comes

c.c.f.

velocity

difference

of

the

transforms

,lielectrlc

rotational

absorption

isolates

whose

functions

only

el~ga1~tly

:ona I

°° c r o s l ~hich are

for

thls

type

the

frequency.

c~rL

m~nw of

~tu,I.

~.he

118 AC I: n e v l i e d g e m e n t This Center

for

research

]heory

¢Co,-nel 1

Theory

National

Science

add|

tiona[

elnd

L.

and

A.

which

Foundat*on from

~esearch I'lafie

material

conducted

~imulation~

Centerl.

support

Cerpormt~

~as

New

in

recelve~ l.B.~l.

York

State

fo,-

resou,

an, l

major

L.

D.

cos

of

the

Entllneerln.

fundin~l

l

from

Corporatzon. and

I'~ o f s .

thanked

the

Science

~n,l

[n=_titut~. are

using

the

~ith

Membe~-s

of

the

Ba~ ron.

G.

x l-;a,l n l e r ~ .

cor,-e~pond~nce

al~d

,-epr

int~

of

.

~ E F EREI-ICES *.I}

S.

F.

lla~on,

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f]ptical

[)iscriminations."

(Cambrzdge

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L.

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Barren,

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and

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[5)

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Am.

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Stephens

and

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Evans.

Salvetti.

and

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Chem.

k.

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rand

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Chem

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Chem.

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1991

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Phys.,

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Evelns.

Canadian

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