MULTIPLE SCATTERING IN THE EXAFS OF IMIDAZOLE CONTAINING COMPLEXES

HAL Id: jpa-00226008

https://hal.archives-ouvertes.fr/jpa-00226008

Submitted on 1 Jan 1986

HAL is a multi-disciplinary open access archive for the deposit and dissemination of sci- entific research documents, whether they are pub- lished or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers.

L’archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d’enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

MULTIPLE SCATTERING IN THE EXAFS OF IMIDAZOLE CONTAINING COMPLEXES

R. Strange, S. Hasnain, N. Blackburn, P. Knowles

To cite this version:

R. Strange, S. Hasnain, N. Blackburn, P. Knowles. MULTIPLE SCATTERING IN THE EXAFS OF

IMIDAZOLE CONTAINING COMPLEXES. Journal de Physique Colloques, 1986, 47 (C8), pp.C8-

593-C8-596. �10.1051/jphyscol:19868111�. �jpa-00226008�

JOURNAL DE PHYSIQUE

Colloque C8, supplement au n° 12, Tome 47, decembre 1986 C8-593

MULTIPLE SC&TTERING IN THE EXAFS OF IMIDAZOLE CONTAINING COMPLEXES

R.W. STRANGE*-**, S.S. HASNAIN*, N.J. BLACKBURN** and P.F. KNOWLES***

* Synchrotron Radiation Source, Daresbury Laboratory, GB-Warrington WR4 4KD, Cheshire, Great-Britain

** Department of Chemistry, UMIST, GB-Manchester M60 1QD, Great-Britain

***Astbury Department of Biophysics, Leeds University, GB-Leeds LS3 9JT, Great-Britain

Atis t r a c t

M u l t i p l e s c a t t e r i n g t r o m the o u t e r s h e l l s of an i m i d a z o l e r i n g c o n t r i b u t e s t r o n g l y in the t'XAFS d a t a o v e r a n e x t e n d e d k - r a n g e a n d it is e s s e n t i a l to i n c o r p o r a t e t h i s for an a c c u r a t e s t r u c t u r e d e t e r m i n a t i o n . W e s h o w that the m u I t ipIe s c a t t e r i n g t or m a I ism is a b l e to p r o d u c e the c o r r e c t

d i s t a n c e s tor all the a t o m s of an i m i d a z o l e r i n g c o o r d i n a t e d to c o p p e r .

Int r o d u c t ion

For m e t a I I o e n z y m e s w h o s e X - r a y a b s o r p t i o n s p e c t r u m is d o m i n a t e d by the p r e s e n c e of h i s t i d i n e l i g a n d s s t r u c t u r a l i n f o r m a t i o n f r o m E X A F S h a s o f t e n b e e n r e s t r i c t e d to the f i r s t a n d s o m e t i m e s s e c o n d s h e l l c o o r d i n a t i o n s p h e r e s e x t e n d i n g c a . 3 . 2 A f r o m the a b s o r b i n g a t o m . A t o m s b e l o n g i n g to i m i d a z o l e r i n g s l y i n g b e y o n d t h i s d i s t a n c e h a v e b e e n f o u n d to g i v e c o r r e c t E X A F S c o n t r i b u t i o n s in the low k r e g i o n o n l y if t h e y a r e a l l o w e d to o c c u p y p o s i t i o n s c a . 0 . 2 - 0 . 3 A s h o r t e r t h a n the e x p e c t e d d i s t a n c e s [ 1 , 2 ] .

T h i s s t u d y p r o v i d e s the f i r s t q u a n t i t a t i v e e x a m i n a t i o n of t h i s p r o b l e m . S i n c e m u l t i p l e s c a t t e r i n g e f f e c t s a r e d e p e n d e n t . u p o n the g e o m e t r y of the l i g a n d s in the m e t a l s i t e , our s t u d y h a s i n i t i a l l y b e e n c o n c e r n e d w i t h an a n a l y s i s of t h e s e e f f e c t s in the E X A F S of c r y s t a I I o g r a p h i c a I Iy w e l l c h a r a c t e r i s e d c o p p e r i m i d a z o l e c o m p o u n d s . T h e s e c o m p o u n d s t h e r e f o r e s e r v e a s a m o d e l for the a c t i v e s i t e s of s e v e r a l c o p p e r c o n t a i n i n g e n z y m e s , s u c h as S u p e r o x i d e D i s m u t a s e a n d D o p a m i n e b - m o n o x y g e n a s e . H e r e w e r e p o r t the d e t a i l e d r e s u l t s o n c o p p e r t e l r a k i s ( i m i d a z o l e ) d i n i t r a t e [ 3 J .

E x p e r irnen t a I

T h e s a m p l e w a s a m e a s u r e d a s a p o w d e r . E X A F S e x p e r i m e n t s w e r e c a r r i e d o u t at l i q u i d n i t r o g e n t e m p e r a t u r e s in t r a n s m i s s i o n m o d e u s i n g b e a m - l i n e 7.1 at the S y n c h r o t r o n R a d i a t i o n S o u r c e at D a r e s b u r y L a b o r a t o r y . T h e S R S w a s o p e r a t e d ai 2 G e v w i t h a m a x i m u m b e a m c u r r e n t of 3 0 0 m A .

Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:19868111

JOURNAL DE PHYSIQUE

D a t a A n a l y s i s

EXAFS s ~ r n u l a t ~ o n s w e r e c a r r i e d o u t u s i n g t h e OXCClHVE p r o g r a m ( G u r m a n e t a l . , 1 3 8 4 C 4 3 , 798C.;C:;1),, w h i c h 1 s b a s e d u p o n t h e s r n y l e s c a t t e r i n g s p h e r ~ c a l w a v e t h e o r y d e v e l o p e d b y L e e a n d P e n d r y ( 1 Y T 5 C 6 3 ) . M u l t i p l e s c a t t e r i n g c a l c u t a t ~ o r , s w e r e c a r t l e d o u t w i t h r n EXCUHVE b y d e f i n i n g t h e g e o m e t r y o f t h e ~ r n i d a z o l e r ~ n g s f r o m t h e k n o w n c r y s t a l l o g r a p h f c d a t a a n d t h e n s u h m l t i ~ n g a b a c k g r o u n d j o b u s I r ~ g t h e p r o g r a m E X F I T ( B c n s t e d , u n p u b l i s h e d ) .

Multiple S c a t t e r i n g

M u l t i p l e s c a t t e r ~ n g e f f e c t s w e r e f l r s t o b s e r v e d ~ n t h e EXAFS o f c o p p e r f o i l ( L e e a r ~ t l P e n d r y , 1 9 7 5 C d l ) , w h e r e t h e f o t ~ r t t ~ : j h e l I s c a t t e r l n g amplitude w a s f o u n d t o b e l a r g e r t h a n t h a t c a l c u l a t e d b y s l n g l e s c a t t e r i n g t h e o r y .

I n a n . i m ~ d a z o l e r i n g m u [ t i p l e s c a t t e r i n g o c c u r s d u e t o s t r o r r q f o r w a r d s c a t t e r i n g b e t w e e n t h e M I s h e i t a n d t h e r43/C3 a n d (.:2 s h e l l s . 'he m a i n m u l t i p l e s c a t t e r ~ n g p a t h w a y s e > : p e c t e d for l m i d a z o l e a r ~s h o w n i n F i g u r e 1 . M u l t ~ p l e s c a t t e r l n g h a s a s t r o n g a n g u l a r d e p e n d e n c e . T h e s t r o n g e s t f o r w a r d s c a t t e r i n y o c c u r s w h e n t h e a t o m s i n v o l v e d a r e a r r a n g e d c o - 1 { n e a r l y ; f o r a s c a t t e r 11-19 p a t h w a y o f 9 0 ' t h e r n u l t r p l e s c a t t e r i n g I S n e g l ~ g i h l e . F o r C u ( l r n ' 4 ( N C ) 3 ) 2 t h e s c a t t e r l n l a n g l e s a r e 1 6 3 ' ( p a t h w a y C u = N 1 = N 3 / C 3 ) a n d 1 2 5 ' ( p a t h w a y Cu = N 1 = C 2 1 , a s i n d i c a t e d ~ n F ~ g u r e 1 . S l n c e t h e . s c n t t e r ~ r ~ g p a t h w a y . ; a l l l IF! f n t h ? same p l a n e t h i s a n g l e I S sufficient t o d e f l n e t h e g e o m e t r y r e q u i r e d f u r r n u i t r p l e s c a t t e r ~ n r g c a l c i i l a t i o n s . T h e m ~ t l t r p l e s c a t t e r f n : ~ p a r t c . t t h e EXAFS s p e c t r u m I S o b t a ~ n e d b y s u m i ~ n g t h e c o n t r l b u t l o n s f r o m a l l t h e s c a t t e r i n g p a t h w a y s b e t w e e n t h e a b s o r b i t \ g a t o m a n d t h e CZ a r ~ d N 3 / C 3 a t o m s . T h e t o t a l EXAFS of t h e C u a t o m t h e r e f o r e c o n s c s t s o f

t J r r e c t b a c k s c a t t e r i n y cant r i b u t I o n ? f t o m t h e C:2 a n d N 3 / C 3 a t o m s ( s ~ n g l e s c a t t e r ~ n g ) p l u s t h e b a c k s c a t t e i i n g f r o m t h e s e a t o r n s v ~ at h e f I r s t s h e l l n f t r o g a r i ( r r ~ u l t r p l c s c a t t e r ~ n g ) .

EXAFf IEXFERIIIENT) *K**3 ---

1.5 EXAFS (1 HEORY) %K-*3 ^. - -. . . - -

I

F~~~~~ 2 , EXAFS s ~ m u i a t i o n o f R e p r e s e n t a t i o n o f a n ~ m r d a z o l e r f n g C u ( I m 1 d ) 4 ~ N 0 ' 3 ) 2 .

R e s u l t s

T h e c r y s t a l s t r u c t u r e p a r a m e t e r s f o r C u ( l m ) 4 ( N 0 3 ) 2 a r e g i v e n ~ n t a b l e 1. S i n g l e s c a t t e r i n g t h e o r y s h o w s t h a t a n a c c e p t a b l e s i m u l a t i o n o f t h e EXAFS o f C u ( l m i d ) 4 ( N 0 3 ) 2 c a n b e o b t a i n e d f o r t h e f i r s t s h e l l n i t r o g e n ( N 1 ) a n d s e c o n d s h e l l c a r b o n ( C 2 ) a t o m s c l o s e t o t h e i r c r y s t a l l o g r a p h i c v a l u e s . H o w e v e r , t h e t h i r d s h e l l c a r b o n ( C 3 ) a n d n i t r o g e n ( N 3 ) a t o m s a r e r e f i n e d some 0 . 3 A s h o r t o f t h e i r k n o w n d i s t a n c e s ( F i g u r e 2 ) . T h i s s h o r t e n i n g o f t h e t h i r d s h e l l d i s t a n c e s h a s f r e q u e n t l y b e e n s e e n i n EXAFS s i m u l a t i o n s o f many s t r u c t u r e s w h e r e h i s t i d i n e l i g a n d a r e p r e s e n t [ 1 , 2 1 . The o r i g i n o f t h i s e f f e c t may b e s e e n b y f ~ l t e r i n g o u t t h e c o n t r i b u t i o n t o t h e EXAFS o f t h e t h ~ r d s h e l l a t o m s i n t h e r a n g e 3 . 5 < k < 4 . 5 A

.

t

^KIA"

F i g u r e 3 . B a c k t r a n s f o r m e d EXAFS o f F o u r ~ e r f i l t e r e d t h i r d s h e l l s h o w l n g ( a ) t h e p h a s e p r o b l e m f o r s i n g l e s c a t t e r i n g f o r t h e c r y s t a l l o g r . a p h i c a l l y d e t e r m i n e d d i s t a n c e s a n d ( b ) t h e f i t o b t a i n e d t o t h e t h i r d s h e l l c o n t r i b u t i o n when m u l t i p l e s c a t t e r i n g i s i n c l u d e d .

The m u l t i p l e s c a t t e r i n g w a s c a l c u l a t e d i n i t i a l l y u s i n g t h e c r y s t a l s t r u c t u r e p a r a m e t e r s g i v e n i n t a b l e 1. T h e r a d i i o f t h e o u t e r s h e l l a t o m s a n d EO w e r e i t e r a t e d d u r i n g t h e c a l c u l a t i o n a n d t h e s i n g l e s c a t t e r i n g EXAFS w a s a d d e d a s a c o n s t a n t a t e a c h s t e p i n t h e i t e r a t i o n . T h e r e v i s e d p a r a m e t e r s f r o m t h e m u l t i p l e s c a t t e r i n g c a l c u t a t i o n w e r e t h e n u s e d t o r e - c a l c u l a t e t h e s i n g l e s c a t t e r i n g c o n t r i b u t i o n , w h i c h w a s t h e n a d d e d t o t h e m u l t i p l e s c a t t e r i n g EXAFS.

T h i s p r o c e d u r e w a s r e p e a t e d t i l l f u r t h e r r e f i n e m e n t o f t h e p o s i t i o n s o f t h e o u t e r s h e l l a t o m s i n t h e s i n g l e o r m u l t i p l e s c a t t e r i n g t h e o r y

r e s u l t e d i n o n l y m i n o r ( < 0 . 0 2 A ) c h a n g e s i n t h e i r v a l u e s .

T h e f i n a l f i t o b t a i n e d b y t h i s p r o c e d u r e i s s h o w n i n f i g u r e 4 . T h i s s h o w s a c l e a r i m p r o v e m e n t i n t h e f i t c o m p a r e d w i t h t h a t o b t a i n e d u s i n g s i n g l e s c a t t e r i n g t h e o r y o n l y ( f i g . 2 ) , a n d t h e f i t p a r a m e t e r s ( t a b l e 1 ) a r e c l o s e t o t h o s e o f t h e c r y s t a l s t r u c t u r e . T h e o v e r a l l s h a p e o f t h e XANES i s a l s o w e l l r e p r o d u c e d b y t h e m u l t i p l e s c a t t e r i n g s u g g e s t i n g t h a t t h e d o m i n a n t m u l t i p l e s c a t t e r i n g c o n t r i b u t i o n i n t h e XANES r e g i o n i s d u e t o t h e i n t e r n a l a t o m s o f t h e i m i d a z o l e r i n g s .

C8-596 JOURNAL

DE

RIER TRANSFORM (EXP)

-

RIER TRANSFORM (THE1 ---

I

-LI

K/

F i g u r e 4. E X A F S s i m u l a t i o n o f - C u ( l m l d ) 4 ( N 0 3 ) 2 i n c l u d i n g m u l t i p l e

CRYSTAL STRUCTIJKE EXAFS

PARAMETERS SINGLE MULTIPLE SCATTERING SCATTERING

~ ( 1 ) ~ ( 1 )

R(E) ~ 1 8 ' )

2.00 2.00 0.005 2.00 0.005 P a r a m e t e r s u s e d in E X A F S s r m u l a t ~ o n s

2.98 2-92 0.010 2.92 0.007

4.18 3.87 0.010 4.22 0.010

C o n c l u s i o n s

T h e w o r k p r e s e n t e d h e r e c l e a r l y d e m o n s t r a t e s the importance of m u t t ~ p l e s c a t t e r i n g ~ n t h e E X A F S of s y s t e m s containing l m l d a z o t e

l ~ g a n d s . S l g n ~ f l c a n t m u l t i p l e s c a t t e r i n g c o n t r ~ b u t l o n s a r e p r e s e n t In the E X A F S u p to a b o u t 2 5 0 e V a b o v e t h e a b s o r b t ~ o n e d g e a n d t h e s e c o n t r l b u t ~ o n s a r e n e c e s s a r y tn o r d e r t o f i x t h e t h i r d s h e l l a t o m s of the ~ m i d a z o l e r ~ n g s at t h e ~ r c o r r e c t p o s ~ t l o n s . B y ~ n c l u d ~ n g m u l t l p l e scattering ~ n the E X A F S ~t i s p o s s l b l e to e x t e n d the l o w e n e r g y r e g l o n o f t h e s p e c t r u m to ~ n c l u d e t h e X A N E S , t h e . g e n e r a l s h a p e of t h l s part b e l n g w e l l r e p r o d u c e d .

R e f e r e n c e s

( 1 ) N . J . B l a c k b u r n , S. S . Hasnatn. G. P . D i a k u n , P . F.

K n o w l e s , N. B t n s t e d and C. D . G a r n e r , Blochem. J . , 1983, 2 1 3 , 7 6 5 .

( 2 ) N. J . B l a c k b u r n , S . S. H a s n a ~ n , N. B l n s t e d , G. P . D ~ a k u n . C. D . G a r n e r and P. F . K n o w l e s , Blochem. J., 1984.

2 1 9 , 9 8 5 .

( 3 ) D . L. M c F a d d e n , A. T. M c P h a t l , C. D . Garner. F . E . M a b b s , J. C h e m . S o c . D a l t o n T r a n s . , 1976, 4 7 .

( 4 ) S . J . G u r m a n , N. Btnsted. I . R o s s , J. P h y s . C. S o l l d S t a t e P h y s . , 1984, 17, 143.

( 5 ) S. J. G u r m a n , N. B t n s t e d , I . R o s s , J. P h y s . C. S o l ~ d S t a t e P h y s . , 1986, 19, 1945.

( 6 ) P . A. L e e and J , 6 . P e n d r y , P h y s i c a l R e v i e w B, 1975,