Notizen 675
Electrical Properties of Some Divalent Transition Cupferrone Complexes H. F. Aly *, F. M. Abdel-Kerim and H. H. Afifi
A t o m i c E n e r g y E s t a b l i s h m e n t * a n d N a t i o n a l R e s e a r c h C e n t r e , Cairo, E g y p t .
( Z . N a t u r f o r s c h . 3 1 a , 6 7 5 - 6 7 6 [ 1 9 7 6 ] ; r e c e i v e d A u g u s t 2 , 1 9 7 5 )
F r o m the t e m p e r a t u r e d e p e n d e n c e of t h e e l e c t r i c a l re- sistivity of the divalent M n , C o , N i , C u a n d Z n c u p f e r r o n e c o m p l e x e s it is c o n c l u d e d that these c o m p o u n d s b e h a v e a s s e m i c o n d u c t o r s . It is also f o u n d that t h e charge t r a n s f e r e ( C T ) e n e r g y as c a l c u l a t e d f r o m t h e U V a b s o r p t i o n C T b a n d s is a l w a y s l a r g e r t h a n that drived f r o m the e l e c t r i c a l resistivity.
tained from "Renal" Finomvegyszergyar. The dif- ferent metal cupferrone complexes were prepared and analysed as previously reported The UV ab- sorption spectra of the different compounds were measured in dioxan using a Unicam Sp 800 record- ing spectrophotometer. The D.C. resistivities of the samples were measured on discs of 13 mm diameter and 3 — 5 mm thickness, prepared under a pressure of 12,000 kg/cm2. The measuring cell is shown in Figure 1. The cell was enclosed in an evacuated pyrex tube containing silica gel to keep the cell dry.
A temperature controlled electric furnace was placed around the device. The current was measured with a VA-J-52 electrometer.
Cupferrone (nitrosophenyl hydroxylamine) is a well known chelating agent with many applications in quantitative and qualitative analysis. From the IR, UV and visible spectra of selected divalent cup- ferrone complexes 2 it was evident that these com- plexes are of the charge transfer type. Therefore we decided to measure the electrical conductivities of these compounds and to compare the obtained in- formation with the charge transfer bands obtained in the UV absorption spectra.
Experimental
All chemicals used were A. R. grade, B. D. H.
Label. The ammonium salt of cupferrone was ob-
Results and Discussion
At room temperature, the electrical resistivities (o) of the investigated compounds were found to be of the order 1013 — 1015 Q cm. Linear relation- ships were obtained between logg» and 1/T. The thickness of the samples had no effect on the mea- sured resistivities, as is examplified in Figure 2.
1 0 -
1 0 -
Silica gel 2.3
xx X
O «O* o »o" o x
C u ( C u p )2
x 5.0 mm thickness o 4.1 „ „ . 3.5 •> a
E = 1.57 e.v
2.7 2.9 11 1 0 0 0 / T CK"1)
3.5
Insulated thermocouple
Teflon Copper rod S t a i n l e s s steel
s p r i n g
.Copper electrodes S a m p l e
Teflon
F i g . 1. T h e E l e c t r i c a l C o n d u c t i v i t y C e l l . F i g . 2 . R e s i s t i v i t y of C u ( c u p )2 .
6 7 6 Notizen
This proves that these compounds are intrinsic semiconductors obeying the relation (3) :
0 = Q0 exp {E/k T}
where E is the activation energy of electrical con- duction.
The experimental values of Q0 and E are given in Table 1.
In a previous work 1 it was found that the studied compounds are charge transfere (CT) complexes.
The electronic absorption bands corresponding to
Table 1. Activation and charge transfere energies for the different cupferrone compounds.
Complex ^ C T EQT E
Qcm nm e . V . e.V.
M n ( c u p ) , 1.2 x l O9 3 0 7 4 . 3 0 1 . 1 5 Co (cup) 2 8.1 x l O9 2 7 5 4 . 3 5 1 . 7 5 Ni ( c u p ) , 7 . 0 x l O9 2 5 7 4 . 7 0 1 . 3 0 C u ( c u p )2 6.1 x l O9 2 5 5 4 . 6 2 1.57 Z n (cup) 2 0 . 2 5 x 1 09 3 0 5 4 . 3 2 2 . 0 1
1 A. H . Abou-El Ela, F. M . Abdel-Kerim, H. H . Afifi, and H . F. A l y , Z. Naturforsch. 2 8 b , 6 1 0 [ 1 9 7 3 ] .
2 A . H. A b o u - E l Ela and H. H . Afifi, Z . Naturforsch. 2 9 a, 7 1 9 [ 1 9 7 4 ] .
3 Y . Ocamato and W . Brenner, Organic Semiconductor, Reinhold, New York 1964.
the CT transitions in dioxan solution at room tem- perature are given in Table 1, together with their CT energies. If the band model for intrinsic semi- conductors is extended to charge transfer complexes, one may expect coincidence of the energy gap
(E = 2 E ) with the charge transfer energy (£ct)>
However, this may not be valid if the charge carrier is not produced directly through such an excitation process. Kuroda et al.4' 5 put
e = Eqt - d
where, d was found to be in the order of 1 eV for trinitrobenzene complexes. In the present investiga- tion, the d values encountered were between 0.3 and 2.1 eV. Since Ec t was taken in dioxan, the ^-values observed may be mainly due to the medium effect.
Acknowledgement
The authors would like to thank Dr. A. Abou-El Ela for some technical assistance.
4 H . Kuroda, M . Kabayashi, M . Kinoshita, and S. Taka- mato, J. Chem. Phys. 3 6 , 4 5 7 [ 1 9 6 2 ] .
5 H. Kuroda, K . Yoshihara, and H. Akamatu, Bull. Chem.
Soc. Japan 3 5 , 1 6 0 4 [ 1 9 6 2 ] ,
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