Structure of the organic semiconducting radical cation salt [2,3;7,8-bis (ethylenedioxy) thianthrene] hexafluoroarsenate

Synthetic Metals, 41-43 (1991) 1691-1694

STRUCTURE

OF THE O R G A N I C

1691

SEMICONDUCTING

RADICAL

[2,3;7,~-BI$(ETHYLENEDIOXY}THIANTHRENE]

J. NORELAND, Institute

G° O L O V S S O N

of Chemistry,

CATION

SALT

HEXAFLUOROARSENATE

and I. O L O V S S O N University

of Uppsala,

Uppsala

(Sweden)

ABSTRACT C16HI204S/AsF6-,

Mr=521.30,

c=9.373(i)

A, ~=94.22(2)',

A, ~=22.0

c m ~, F(000)=I036,

reflections. stacks

Dimers

monoclinic, V=1784.9(3) T=295

consisting

C2/m, ~,

K. Final

of

stacking

axis.

have a d i h e d r a l The p r o n o u n c e d

to s e m i c o n d u c t i n g molecules,

as well

disordered.

electronic

angle

b=i0.612(I),

g c m -3, l(Mo K e ) = 0 . 7 1 0 7 3

R(F)=0.052

for 2252

properties.

as all the fluorine

unique

(CI6HI~O4S2=bEDOT)

by the AsF 6

ions.

of ii ° and are t i l t e d

dimerization

The i n t e r m o l e c u l a r

D~=1.94

[(bEDOT)2] 2~ m o l e c u l e s

a l o n g the c axis a n d are s u r r o u n d e d

bEDOT m o l e c u l e s

a=17.992(2),

Z=4,

The n o n p l a n a r 48"

relative

and the I:i s t o i c h i o m e t r y

The e t h y l e n e

atoms

S.--S d i s t a n c e

groups

in the AsF 6

to the

give

rise

of the bEDOT

ions,

in the dimer

form

are found to be

is u n u s u a l l y

short:

3.06 A.

INTRODUCTION This w o r k properties substituted electronic However,

is part of a series

of e l e c t r o c h e m i c a l l y aromatic

hydrocarbons

and magnetic

the c r y s t a l s

properties,

stacks.

0379-6779/91/$3.50

A solvent-free

of the s t r u c t u r e

radical

as donors.

cation

structure

is r e p o r t e d

with chalcogen-

often exhibit

simple

of p o o r quality.

along with the anions

a n d physical

salts

Such c o m p o u n d s

and are r e l a t i v e l y

are in m a n y cases

often f o u n d to be i n c o r p o r a t e d cation

of studies prepared

unique

to prepare.

Solvent

molecules

in the channels

are

between

the

here.

© Elsevier Sequoia/Printed in The Netherlands

1692 RESULTS A disordered carbons

model

C1 and C8

was u s e d with two a l t e r n a t i v e

(CIA, CIB and C8A,

found to be d i s o r d e r e d were

refined

a difference and thermal

and was t r e a t e d

at two e q u a l l y F o u r i e r map. ellipsoids

C8B,

in a similar

occupied positions

The crystal

positions

respectively).

packing

for the bEDOT m o l e c u l e

way,

each,

for the e t h y l e n e

The AsF 6 ion was also i. e. the fluorines

as was c l e a r l y

is shown in Fig.

in Fig.

indicated

2.

5 Fig. I. A stereoscopic o m i t t e d for clarity.

view of the m o l e c u l a r

H3

packing.

Hydrogens

have b e e n

HH

s

H3

in

I; b o n d d i s t a n c e s

H~

Fig, 2. B o n d d i s t a n c e s (A) and atomic n o t a t i o n s for the b E D O T molecule. All thermal e l l i p s o i d s p l o t t e d at 50% probability. S t a n d a r d d e v i a t i o n s for C-C (non-disordered) and C-O d i s t a n c e s are 0 . 0 0 5 - 0 . 0 0 6 ~ and for c o r r e s p o n d i n g angles 0.2-0.3".

1693

The a s y m m e t r i c The m i r r o r molecular twofold

3.6 ~ of +i.

plane

consists

is p a r a l l e l

plane

axis.

distance

unit

(Fig. 2).

of half a bEDOT m o l e c u l e to the long m o l e c u l a r

The bEDOT m o l e c u l e s

The As a t o m lies

within

in the m i r r o r

the bEDOT dimer

[I]). F r o m the s t o i c h i o m e t r y The bEDOT m o l e c u l e

dihedral

angle b e t w e e n

molecule

is Ii'.

C

follows

is somewhat

the planes

plane.

a dimer

The i n t e r m o l e c u l a r

(van der Waals

S

C5 C6

~

C

1

C? 02

~

C8. 02 ~

C

a

c~

I

a

O

S...S distance

has a charge

(cf. Fig.

3); the

of the t h i a n t h r e n e

CSR

8

E,, FiI uI

C1A OI

contact

that e a c h bEDOT m o l e c u l e

d e f i n e d by each half

to the

are r e l a t e d by the

bent a r o u n d the S-S axis

C2 C3 C~l

8

axis a n d p e r p e n d i c u l a r

within

is only 3.06 A

and half an AsF 6- ion.

C

~W

C3 C2

CIR Fig. 3. S t a c k i n g along the c axis. The shortest i n t e r m o l e c u l a r d i s t a n c e s in the stack are m a r k e d as d o t t e d lines (S...S=3.061(2), A=3.372(4), B=3.594(5), C=3.790(4), D=3.990(4), E=3.635(5), F=3.675(4), G=3.818(7) A). The AsF~- ions s u r r o u n d i n g the lower dimer have been o m i t t e d for clarity. Intrastack

arranQement

The n o n p l a n a r AsF 6" ions

bEDOT molecules

surrounding

f o r m dimers.

These

displaced.

(Figs.

3, 4 and 5).

Because

This gives

of the strong

perfect

perpendicular

Interstack

overlap

are p a c k e d

(Figs.

are t i l t e d

dimers

almost

them

48"

in stacks

1 a n d 3). Within relative

to the s t a c k i n g

rise to two different

S...S i n t e r a c t i o n between

modes

and the s y m m e t r y

the m o l e c u l e s

to the m e a n m o l e c u l a r

along the c-axis,

a stack,

plane

within

(cf. Figs.

with the

the bEDOT m o l e c u l e s axis,

making

of m o l e c u l a r

properties,

the dimer

adjacent

overlap

there

is an

when v i e w e d

3 and 4).

arranaement

The i n t e r s t a c k straightforward

arrangement

to analyze

by six AsF 6- ions on four

is shown

in Fig.

due to the disorder.

sides

(Figs.

3 and 4).

4. The d e t a i l e d

contacts

The bEDOT dimers

are not

are s u r r o u n d e d

1694 As-.As

5.246(i) A A

•

IOIO]

11O21

Fig. 4. A r r a n g e m e n t s a r o u n d the b E D O T dimers v i e w e d a p p r o x i m a t e l y p e r p e n d i c u l a r to the m e a n m o l e c u l a r plane. Both p o s i t i o n s of the d i s o r d e r e d fluorine atoms and e t h y l e n e groups are shown (filled and u n f i l l e d ellipsoids, respectively). The bEDOT m o l e c u l e s in the dimer have an almost p e r f e c t overlap, and are t h e r e f o r e p r a c t i c a l l y i n d i s t i n g u i s h a b l e f r o m a single molecule.

S

Ol

Fig.

5. O v e r l a p

Physical The

between

two b E D O T m o l e c u l e s

in a d j a c e n t

dimers.

properties [bEDOT]+AsF6 - salt

is s e m i c o n d u c t i n g

of 2 x i0 ' (~ cm) -z. Basic with

O1

5

I:i s t o i c h i o m e t r y

donor has a charge

with a r o o m - t e m p e r a t u r e

low-dimensional

cannot

physics

be m o r e than s e m i c o n d u c t i n g .

of +i, a n d in order to m o v e

repulsive

energy between

overcome.

The electronic,

[2] shows

two e l e c t r o n s optical

an e l e c t r o n

that

In this

properties

case e v e r y

along the stack the

on the same b E D O T m o l e c u l e

and m a g n e t i c

conductivity a compound

has to be

are r e p o r t e d

in

[3].

ACKNOWLEDGEMENTS This work has been s u p p o r t e d Technical

Development,

wish to thank Dr Jonas S~derholm

which

by a grant

f r o m the N a t i o n a l

is h e r e b y g r a t e f u l l y

Hellberg

for p r o v i d i n g

for d o i n g the c o n d u c t i v i t y

Swedish

acknowledged.

the c r y s t a l s

Board

The a u t h o r s

for also

and Dr Svante

measurements.

~FE~NCES 1

A. Bondi,

2

S. S6derholm,

Technology, 3

J. Phvs.

S-I00

S. S6derholm,

En~an,

Mol.

Chem..

Ph.D. 44

Stockholm,

J. Noreland,

Crvst.

68

Thesis.

LiQ.

(1964)

441-451.

Trita-Fvs Sweden,

0280-316X

G. Olovsson,

Crvst..

167

3009,

The Royal

Institute

1987.

(1989)

I. Olovsson, 259-268.

J. H e l l b e r g

a n d L.

of