10 Electronic Structure and Stability of Transition Metal Ions in Zeolites KAMIL KLIER and PAUL J. HUTTA Downloaded by UNIV OF CALIFORNIA SAN DIEGO on June 5, 2015 | http://pubs.acs.org Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0040.ch010
Lehigh University, Bethlehem, Penn. 18015 RICHARD KELLERMAN Xerox Corp., Webster, N.Y. 14580
ABSTRACT A theory of the e l e c t r o n i c s t r u c t u r e of t r a n s i t i o n metal ions in z e o l i t e s which takes i n t o account the s i t e symmetry and v i b r a t i o n a l - e l e c t r o n i c i n t e r a c t i o n s is presented. The r e l a t i v e s t a bilities in trigonal sites (Cu =Ni >Co >Fe >Mn , Cr = V >Ti ), redox p o t e n t i a l s , axial and o f f - a x i a l d i s t o r t i o n s , and o p t i c a l t r a n s i t i o n s are c a l c u l a t e d and compared w i t h published data. II
II
II
II
II
II
II
II
II
Introduction I t i s w e l l e s t a b l i s h e d that t r a n s i t i o n metal ions i n z e o l i t e s act as s p e c i f i c chemisorption centers (1-4), form i n t r a z e o l i t i c complexes (5,6), undergo redox r e a c t i o n s (7-10), and are c a t a l y t i c a l l y a c t i v e i n o x i d a t i o n r e a c t i o n s (11). These p r o p e r t i e s stem from the e l e c t r o n i c s t r u c t u r e of the ions i n c o o r d i n a t i v e l y unsaturated s i t e s of the z e o l i t e i n t e r n a l s u r f a c e s , and are accompanied by w e l l defined p h y s i c a l p r o p e r t i e s such as o p t i c a l absorption, photoluminescence, magnetic moments, and magnetic resonances, chara c t e r i s t i c of both the metal i o n and i t s enviroment. A theory that accounts f o r these phenomena must take i n t o cons i d e r a t i o n the s i t e symmetry, i n t e r e l e c t r o n i c r e p u l s i o n , v i b r a t i o n a l - e l e c t r o n i c i n t e r a c t i o n s , s p i n - o r b i t c o u p l i n g , and i n t e r a c t i o n s w i t h electromagnetic f i e l d s where present, and to compare the chemi c a l p r o p e r t i e s and s t a b i l i t i e s of the i n d i v i d u a l i o n s , such a theory should encompass the whole t r a n s i t i o n s e r i e s . The i n t e r e l e c t r o n i c r e p u l s i o n and s i t e p o t e n t i a l energies f o r 3h * C symmetries were f i r s t analyzed f o r the Ni^+ i o n and compared with the o p t i c a l s p e c t r a of the NiA z e o l i t e (12,13). In t h i s paper an a n a l y s i s i s presented f o r a l l the d configurations. Further d i s c u s s i o n i s devoted to the e f f e c t s of v i b r o n i c coupling on the s t a b i l i t y of ions i n t r i g o n a l and t e t r a h e d r a l s i t e s , and to the consequences of combined c r y s t a l - f i e l d , J a h n - T e l l e r e f f e c t , and spin-orbit coupling. D
a n
}of an E s t a t e are D
t
e
1
V
f
x
1
x
x
T
1
H
+
JT -
V
m
y
( 4 )
and H
|Ε·Ι>
JT
ι
0
[ - |
