Radiolysis  of Cobalt (II) and Nickel (II) – Complexes Containing 
Mixed Ligands by Gamma Rays

Z. F. DAWOOD*  &  M. W.  IBRAHIM
* Chemistry Department/ Education College/ Mosul University

(NJC)

(Received on    11 / 1 /2005)		(Accepted for publication on   27/10 /2005)

Abstract
The effect of gamma-radiation has been studied directly on some solid complexes cobalt (II) and nickel (II) complexes having the formula [M2(LH2)2(AH2)2(NO3)2](NO3)2 , [M2(LH2)2(AH2)2Xn] and [M2(SCH)2(AH)2] (where M = Co+2 or Ni+2, AH2 = any of the following carboxylic acid “ salicylic acid–SH2 , anthranilic acid–AnH2 or phthalic acid–PH2”, LH2=salicylaldehyde semicarbazone–SCH2 or salicylaldehyde thiosemicarbazone-STH2 , X= CO3-2 or CH3CO2- ; n = 0, 2 or 4). Ionization  and excitation of these complexes have been achieved . The melting or decomposition points, conductivities and electronic spectral data have been indeed related to the final stable products . The results showed that some of the complexes have been decomposed by gamma ray, others complexes have not been affected . Very interesting results have been obtained in the case of, [Co2(SH2)2(SCH2)2(NO3)2](NO3)2 , [Ni2(SH2)2(STH2)2(NO3)2](NO3)2 , [Co2(SH)2(SCH)2] , [Ni2(AnH2)2(STH2)2(NO3)2](NO3)2 ,  [Ni2(PH2)2(STH2)2(NO3)2](NO3)2 , [Co2(PH)2(SCH)2]  in which a sort of polymerization have been exhibited after their radiolysis . 

الخلاصة
يتضمن دراسة تأثير أشعة كاما على بعض المعقدات الصلبة مباشرة للكوبلت (II) والنيكل  (II) الحاوية على مزيج من الليكاندات سالسالديهايدسميكاربازون- SCH2 أو سالسالديهايدثايوسميكاربازون - STH2 والأحماض الكاربوكسيلية (حامض السالساليك - SH2 أو الانثرانيليك- AnH2 أو الفثاليك - PH2 ) ذات الصيغ [M2(LH2)2(AH2)2Xn] و[M2(LH2)2(AH2)2(NO3)2](NO3)2  و [M2(SCH)2(AH)2](حيث M=Co+2 أو Ni+2 و AH2 = أحدالأحماض الكاربوكسيلية أعلاه و LH2 = سالسالديهايد سميكاربازون أو سالسالديهايدثايو سميكاربازون و X = CO3 –2  أو CH3CO2 –  و n = صفر أو 2 أو 4) ، حيث ينتج تأين واثارة لهذه المعقدات .  تعود درجات الانصهار أو التفكك والتوصيلية وطيف الأشعة فوق البنفسجية الى المركبات المستقرة النهائية  . أوضحت النتائج أن بعض المعقدات تتفكك بفعل أشعة كاما وبعضها الاخر يحدث لها بلمرة كالمعقدات ذات الصيغ  :[Co2(SH2)2(SCH2)2(NO3)2](NO3)2  و  [Ni2(SH2)2(STH2)2(NO3)2](NO3)2  و[Co2(SH)2(SCH)2]   و[Ni2(AnH2)2(STH2)2(NO3)2](NO3)2   و [Ni2(PH2)2(STH2)2(NO3)2](NO3)2  و [Co2(PH)2(SCH)2] وهي نقطة مهمة لما للبوليمرات من اهمية حاليا . 

Introduction 
The effect of any ionizing radiation  started  with an interaction between radiation and the molecules . There have been two different types of interactions either direct effect which observed in the same molecule where the primery absorption occurred or indirect effect in which the radiation energy has been absorbed in another molecule (solvent) resulting in the formation of reactive products that subsequently reacted with other molecules in the system . In a dry system (without solvent) , only the direct effect occurred(1) .
A good deal of work has been reported on the radiolysis of complexes in solutions , this is due to the capability of the active species ( .OH, H.,e-aq, …….. …..etc) of affecting on              metal-complexes(2) . A large body of radiolysis of metal-complexes in solutions have been reported(2-5) .  
The direct gamma irradiation effects (without solvent)have been studied widely  on some organic, biological and amorphous compounds(6-10), whereas on the solid metal-complexes a few articles were reported(11-21)     
It was well-known that the reaction of the ligand molecule in coordination compounds have been affected by the central metal ions .The direct excitation of the complexes by an ionizing radiation can be expected in the radiolysis of crystalline complexes(11) .The study on the radiolysis of crystalline metal complexes was also considered to be very helpful for the elucidation of the mechanism of the reaction affected by metal ions(12) . The anion (eg. C2O4-2) in metal salt ( eg. Na2C2O4) was very  stable to gamma ray irradiation , compared with those in metal-ligand (as metal oxalato) complexes . The fairly large reactivity of the complexes toward gamma irradiation may be attributed to the covalent character of ligand-metal bond . The ligand ions with large covalent character decomposed more easily by gamma                  irradiation(11,13) . The oxalato complexes were irradiated with gamma rays at room temperature(11,14,15) . The much larger G values of  Fe2+ and Co2+ complexes than that of Al3+ complex can not be explained only by the covalent character of the ligand-metal bond , but they seemed to be related with the reduction of metal ions . On gamma irradiation of Fe3+ and Co3+ complex , the reduction of the metal ions also occurred , and ferrous and cobaltous oxalate participitated when the irradiated complexes were dissolved in water . Therefore, the electron transfer from the ligand (oxalate) to metal ion might increase the radiation-induced decomposition of the ligand (oxalate) . While in the case of gamma irradiation of chromium complex , the electron transfer from ligand (oxalate) to metal ion might be difficult and this might cause the lower G value of Cr3+ complex than those of Fe3+ and Co3+ complexes . But on the reaction of Cr3+ complex the oxidation of Cr3+ to Cr6+ might occur, and a fairly large amount of CO was formed inplace of  CO2 which was main product in the gamma irradiation of the oxalate complexes other than those with Cr3+  (15) .   
A protective effect of certain metal ions on the enzymatic activity of gamma irradiated dry trypsin was first discovered(16) . Subsequently, several studies on the effects of metal ions in decreasing the initial radical yields in various proteins, nucleic acid and related substances(16-20) were carried out . Complexes were consistent with the hypothesis that cupric ions were acting as electron scavengers(19) . The effect of copper (II), iron (II), nickel (II) and cadmium (II) ions on the gamma radiolysis of collagen and polyadenylic acid in the solid state were also investigated in the absence of air(21) . The effect of metal ions were found in reducing the radiation-induced , decreasing of the average molecular weight and the formation of stable carbon radicals at room temperature(21) . There was a considerable degree of similarity between the effects of ions in preventing the radiation induced formation of carbon radicals and the decrease of average molecular weight in collagen and polyadenylic acid . For the DNA-metal complexes, we have observed that metal ions decreased the initial radical yield at 77 0K and at 298 0K to approximately the same extent(18) . The effect of gamma radiation has been studied directly on the solid Schiff base-complexes of copper (II), cobalt (II) and nickel (II) resulting in ionization and excitation of these complexes . Gamma-irradiation caused the decomposition of some complexes and polymerization in the other complexes(12,22)         
The one-electron reduction of several metal bis-dithiolenes at the surface of TiO2 particles have been studied using variable temperature EPR measurements following band-gap excitation of the particles showed the disappearance of signals due to paramagnetic Ni (III) and Cu (II) complexes of 4,5-dimercuptophthalic acid, 3,4-dimercuptotoluene and malconitrile dithiolate with the surface electron signals vanishing concomitantly . Similarly , the diamagnetic Cu (II) complex of 3,4- dimercaptotoluene was reduced to paramagnetic Cu (II) complexes(23) . The triplet state has been studied for solid complexes(24) .
To the best of available knowledge , the effect of gamma irradiation  on some mixed ligand (semicarbazone and substituted carboxylic acid) complexes of cobalt (II) and nickel (II), have not yet been reported . It is a matter of interest to determine  the extent to which gamma irradiation for these complexes would be affected .  

Experimental
1.	Preparation of the compounds :
The ligands salicylaldehyde semicarbazone(25-27) and salicylaldehyde thiosemicarba- zone(26,28-31) have been prepared according to the literature methods . The complexes in neutral and basic medium have been synthesised according to the previous methods (26-31) .
2.	Radiolysis of the complexes :
All gamma irradiation have been carried out using gamma cell-220 purchased from the Canadian Atomic Energy . The solid complexes were put in a fine cylindrical tubes and the tubes were sealed . Irradiation of the complexes have been carried out in different interval times ( 5, 10, 15, 20, 30, 40, 50 and 60 minutes) under 4.52x1016 ev. ml-1. Min-1 dose rate . The complexes before and after irradiation were dissolved in dimethyl- formamide (for comparison) in order to measure their absorbance and  conductivities . 
3.	Conductivity and spectral  measurements :
Molar conductivities of the complexes (before and after irradiation) have been measured in an electrolytic conductivity measuring set LF-42 and Multiline F/SET-2 WTW using 10-3 M dimethylformamide at room temperature .   
The electronic spectra of the complexes (before and after gamma-irradiation) in 10-4  M dimethylformamide solutions, have been recorded on Shimadzu UV-Visible Recording Spectrophotometer -160  and Shimadzu Double-beam Spectrophotometer UV-210A . 

Results & Discussion 
The radiolysis of solid matter caused  ionization , ejection of electrons from some 
atoms and exitation accompained by chemical reactions and decomposition . 
[MLn]    ~~~→      [MLn]*     ,     [MLn-y]+  +  YL-    ,        e
 (complex)      (exited molecule)          (ions)              (ejected electron)                    

The effect of the coordinated ligands in the complexes was more reactive under  ioniz- 
ation radiation , i.e. the covalency between the ligand and metal was important  for the reactivity of the ligands against ionizing radiation than the free ligand . In addition to the effect of covalency , the oxidation  and reduction of the central metal ions affected the reaction mechanism of the ligand . Gamma-irradiation  brought about the decomposition of the ligand, breakage of hydrogen bonding and a change in the oxidation state of metal ions , the decomposition could be completely giving gaseous liquid and solid products(11-14, 22, 27)  .  
The effect of ionizing  radiation on some complexes containing mixed ligand in solid 
state have been carried out by exposing these complexes to gamma radiation in different time intervals ranging between 5-60 minutes . The changes which happened in these complexes have been noticed by following the changes in melting or decomposition points , the changes in electronic spectra and the changes of molar conductivity  before and after the exposure to ionizing radiation . Different effects for these complexes have been happened (Tables 1-10), some complexes have been resistant to radiation and others showed partial changes, while the other complexes showed noticed  changes.  The melting points of the complexes  were measured directly after gamma irradiation, the changes observed were as follows :                                                                                                                  
complexes 1, 2, 7, 13, 17, 18, 20 and 24 showed changes in the melting or decomp-
osition points and a decrease in the molar conductivities values in addition to the appearance of another band in the electronic spectra of theinvestigated  irradiated complexes, these changes may indicate the formation of oligomerersor polymers which considered indeed as a very interesting result . The reaction mechanism proposed for these complexes may be represented by the following reaction :                                                                             
[M2(L)2(S)2Xn] ~→  [M2(L)2(S)2Xn]. 
[M2(L)2(S)2Xn]. +  [M2(L)2(S)2Xn] ~→ {[M2(L)2(S)2Xn]2}. 
{[M2(L)2(S)2Xn]2}. + [M2(L)2(S)2Xn] ~→   {[M2(L)2(S)2Xn]3}.
    	The polymerization process continued and the final product resulted is having the formula [M2(L)2(S)2Xn]m (where M= the metal ion Co+2 or Ni+2 , L= the carboxylic acid ligands , S= semicarbazone or thiosemicarbazone ligand , X= the counter ion in the investi- gated complexes , n= number of the counter ion , m= number of the complex molecules )
Complexes 3, 14, 15, 16, 23 and 25 showed changes in the melting or decomposition 
points and a decrease in molar conductivities values but no addition bands in the electronic spectra appeared . These changes may be due to attachment of the counter ion by radiolysis which lead to the formation of oligomer or polymer . The proposed reaction mechanism may be represented by the following reactions :                                                       
[M2(L)2(S)2(NO3)2](NO3)2   ~→ { [M2(L)2(S)2(NO3)2](NO3)2}*
{[M2(L)2(S)2(NO3)2](NO3)2}*   ~→ { [M2(L)2(S)2(NO3)2]NO3}1+*  +  NO3.-
{ [M2(L)2(S)2(NO3)2]NO3}1+*  ~→[M2(L)2(S)2(NO3)2]2+*+NO3.-
{[M2(L)2(S)2(NO3)2]}2+* +[M2(L)2(S)2(NO3)2](NO3)2~→[M2(L)2(S)2(NO3)2]2++[M2(L)2(S)2(NO3)2]. +NO3.-.
[M2(L)2(S)2(NO3)2], + [M2(L)2(S)2(NO3)2].   ~→ [M2(L)2(S)2(NO3)2]m 
[M2(L)2(S)2(NO3)2](NO3)2 +  [M2(L)2(S)2(NO3)2]2+   ~→ {[M2(L)2(S)2(NO3)2]2+ }m + 2NO3>-
6NO3.-  → 6NO2  + 3O2
 	Complexes 4, 6, 9, 11 and 22 showed a decrease in the melting or decomposition points and an increase in the molar conductivities values in addition to the appearance of new band in the electronic spectra of the irradiated complexes . The proposed reaction mechanism may be represented as follows:
[M2(L)2(S)2Xn] ~→  [M2(L)2(S)2Xn-1].+* + X.-                                                                                                    
[M2(L)2(S)2Xn-1].+* ~→ {[M2(L)2(S)2Xn-2]2+*+ X.- 
[M2(L)2(S)2Xn-2]2+* + 2X.-  →   {[M2(L)2(S)2Xn-2].X2
 Complexes 10, 12, 19, 27, 28 and 29 showed an increase in the melting or decomposition points and an increase in the molar conductivities values in addition to the appearance of new band in the electronic spectra of the irradiated complexes, this may be due to the decomposition of the dimeric complexes and either changed to monomer or completely decomposed . The proposed reaction mechanism may be represented as follows:
[M2(L)2(S)2Xn] ~→  [M2(L)2(S)2]n+* + nX.-
[M2(L)2(S)2Xn] + [M2(L)2(S)2]n+* ~→ [M2(L)2(S)2]n+ +  [M2(L)2(S)2]. 
[M2(L)2(S)2]. ~→  2[M(L)(S)]                                                                                                                                
2[M(L)(S)]n+* + nX.-  -→   2[M(L)(S)]X
Complexes 26 showed change in the melting or decomposition points and an increase in the molar conductivities values and changes in the absorbance but no band appeared in the electronic spectra of the irradiated complex, this may be due to the breakage of the hydrogen bonding and changes in the structure of the complexes.
Complexes 5 and 21 did not show any changes in the melting or decomposition points but showed an increase in the molar conductivities values in addition to the appearance of new band in the electronic spectra of the irradiated complexes, this may be due to the breakage of the hydrogen bonding . The proposed reaction mechanism may be represented as follows:
[M2(L)2(S)2Xn] ~→  [M2(L)2(S)2Xn-1].1+* + X.-
[M2(L)2(S)2Xn] +  [M2(L)2(S)2Xn-1]1+* ~→ {[M2(L)2(S)2Xn-2]2+*. + X.-
[M2(L)2(S)2Xn-2]+2 + 2X .-→   {[M2(L)2(S)2Xz].X2

Table – 1 : Results of radiolysis for cobalt complexes
prepared in neutral medium

T*	1(26,30)
[Co2(SH2)2(SCH2)2(NO3)2](NO3)2
	2(26,30)
[Co2(AnH2)2(SCH2)2(NO3)2](NO3)2	3(26,30)
[Co2(PH2)2(SCH2)2(NO3)2](NO3)2	
	M.P.  0C	^M **	   λ  ***	A   ****	M.P.  0C	^M  **	λ  ***	A        ****	M.P.  0C	^M **	λ  ***	A   ****	
0	117	103	395	1.686	180 	73	385	1.610	150	136	380	1.483	
5	114	32	395	1.616	196	35	385  391	1.086  1.548	149	21	380	0.864	
10	114	36	395	1.614	192	38	385  391	1.065  1.564	135	15	380	1.495	
15	119	40	395  377	0.958  1.246	180	40	385  395	1.174  1.570	125	5	380	0.848	
20	129	35	395 374	0.942  1.253	174	50	385  391	1.182  1.547	120	6	380	0.649	
30	126	38	395  380	1.333  1.497	178	45	385 392	1.035  1.276	118	5	380	1.136	
40	124	45	395  383	1.470  1.553	185	52	385  391	1.103  1.586	114	2	380	0.959	
50	130	52	395  390	1.520  1.594	182	32	385  391	1.147  1.590	112	15	380	1.215	
60	140	56	395  388	1.556  1.582	176	30	385  391	1.032  1.583	112	20	380	1.649	

M.P. : Melting points or decomposition points
*      T : Time of irradiation 
**   ^M : Molar conductivities in Ω-1 cm2 mol-1  
***  λ :  Wave lengh in nanometer
**** A : Absorbance 

Table – 2 : Results of radiolysis for cobalt complexes                                             prepared  in neutral medium
T*	4(26,30)
[Co2(SH2)2(SCH2)2(Ac)4
	5(26,30)
[Co2(AnH2)2(SCH2)2(Ac)4]	6(26,30)
[Co2(PH2)2(SCH2)2(Ac)4]	
	M.P.  0C	^M **	   λ  ***	A   ****	M.P.  0C	^M  **	λ  ***	A        ****	M.P.  0C	^M **	λ  ***	A   ****	
0	284 	11	409	1.661	286 	16	416	1.640	270	0	408	1.643	
5	n.m	32	409  395	1.346  1.590	286	30	416  402	1.113  1.614	180	2	408  390	1.096  1.583	
10	n.m 	38	409  395 	1.385  1.604	286	28	416  402	1.143  1.605	160	12	408  393	1.191  1.595	
15	260	54	409  395	1.385  1.595	286	24	416  398	0.908   1.565 	180	3	408  387	0.840  1.547	
20	260	51	409  395	1.418  1.593	286	32	416  398	0.793  1.546	120	0	408  393	1.184  1.594	
30	260	44	409  395	1.171  1.352	286	29	416  398	0.785  1.549	120	10	408  390	1.050  1.579	
40	260	90	409  395	1.285  1.572	286	22	416  400	0.990  1.568  	120	14	408  398	1.102  1.588	
50	260	41	409  395	1.447  1.603	286	20	416  397	0.843  1.556	140	14	408  390	1.022  1.578	
60	260	63	409  395	1.630  1.622	286	25	416  397	0.703  1.523	144	15	408  390	1.007  1.580	
 n.m. = not melt or decomposed at 265 0C

Table – 3 : Results of radiolysis for cobalt complexes                                                prepared  in neutral medium
T*	7(26,30)
[Co2(SH2)2(SCH2)2(CO3)2]
	8(26,30)
[Co2(AnH2)2(SCH2)2(CO3)2]	9(26,30)
[Co2(PH2)2(SCH2)2(CO3)2]	
	M.P  0C	^M **	   λ  ***	A   ****	M.P.  0C	^M  **	λ  ***	A        ****	M.P.  0C	^M **	λ  ***	A   ****	
0	275	26	408	1.656	270	28	410	1.638	210	0	407	1.646	
5	n.m	7	408  380	0.779  1.299	n.m	35	410	1.638	210	40	407  373	0.573  1.374	
10	n.m	8	408  380	1.779  1.299	265	36	410	1.638	200	55	407  366	0.346  1.063	
15	260	11	408 393	1.205  1.555	262	38	410	1.638	195	65	407  363	0.458  1.315	
20	260	13	408  390	1.039  1.499	260	32	410	1.638	195	70	407  364	0.463  1.193	
30	260	13	408  380	0.644  1.184	295	35	410	1.638	190	68	407  371	0.361  1.111	
40	258	15	408  387	1.543  1.543	264	25	410	1.638	185	70	407  363	0.490  1.241	
50	258	15	408  390	1.219  1.574	268	30	410	1.638	178	61	407  371	0.533  1.320	
60	258	20	408  383	0.963  1.510	254	38	410	1.638	170	68	407  372	0.439 1.248	

Table – 4 : Results of radiolysis for cobalt complexes                                                 prepared  in basic medium
T*	10(26,30)
[Co2(SH)2(SCH)2]
	11(26,30)
[Co2(AnH)2(SCH)2]	12(26,30)
[Co2(PH)2(SCH)2]	
	M.P  0C	^M **	   λ  ***	A   ****	M.P.  0C	^M  **	λ  ***	A        ****	M.P.  0C	^M **	λ  ***	A   ****	
0	238	12	407	1.630	280	0	407	1.641	245	0	415	1.642	
5	235	22	407  385	1.132  1.575	n.m	0	407  392	1.370  1.610	260	10	415  391	1.271  1.612	
10	230	22	407  385	1.206  1.079 	n.m	0	407  394	1.394  1.691	260	5	415  394	1.394  1.621	
15	230	15	407  385	1.419  1.600 	265	5	407  392	1.453  1.623	240	5	415  388	1.108  1.592	
20	250	12	407  385 	1.439  1.604	265	12	407   394	1.423  1.612	235	8	415  395	1.502  1.628	
30	260	28	407  385	1.543  1.626	265	15	407  394	1.502  1.628	230	8	415  394	1.451  1.622	
40	262	14	407  385  	1.557  1.624	265	10	407  392	1.529  1.637	228	0	415  393	1.291  1.612	
50	260	10	407  385	1.179  1.540  	265	6	407  394	1.451  1.620	250	14	415  397	1.423  1.621	
60	260	10	407  385	1.392  1.603	245	10	407  394	1.390  1.621	260	5	415  403	1.620  1.637	

Table – 5 : Results of radiolysis for cobalt complexes                                               prepared  in neutral medium
T*	13(26,31)
[Co2(SH2)2(STH2)2(NO3)2](NO3)2
	14(26,31)
[Co2(AnH2)2(STH2)2(NO3)2](NO3)2	15(26,31)
[Co2(PH2)2(STH2)2(NO3)2](NO3)2	
	M.P.  0C	^M **	   λ  ***	A   ****	M.P.  0C	^M  **	λ  ***	A        ****	M.P.  0C	^M **	λ  ***	A   ****	
0	176	122	422	1.670	175	132	425	1.665	200	122	426	1.639	
5	200	44	422  424	0.921  1.220	180	50	425	1.598	200	52	426	1.633	
10	210	55	422  428	1.446  1.624	190	50	425	1.615	215	55	426	1.639	
15	225	65	422  428	1.386  1.626 	190	50	425	1.611	220	50	426	1.639	
20	230	70	422  428 	1.467  1.631	200	61	425	1.626	220	56	426	1.644	
30	230	68	422  428	1.397  1.634	180	65	425	1.614	220	53	426	1.639	
40	230	74	422  428	1.455  1.636	170	55	425	1.612	220	58	426	1.641	
50	230	61	422  428	1.215  1.634	170	50	425	1.614	220	46	426	1.639	
60	230	68	422  428	1.414  1.639	170	65	425	1.614	220	64	426	1.644	

Table – 6A : Results of radiolysis for nickel complexes                                      prepared  in neutral medium

T*	16(26)
[Ni2(SH2)2(SCH2)2(NO3)2](NO3)2
	17(26)
[Ni2(AnH2)2(SCH2)2(NO3)2](NO3)2	
	M.P.  0C	^M **	λ    ***	A   ****	M.P.  0C	^M  **	λ  ***	A        ****	
0	150	161	395	1.617	180	129	398	1.627	
5	80	50	395	1.609	160	31	398  380	1.302  1.502	
10	160	35	395	1.394	145	50	398  380	1.573  1.597	
15	110	45	395	1.240	140	35	398	1.641	
20	146	35	395	1.444	138	35	398	1.623	
30	130	40	395	1.325	130	45	398	1.617	
 40 	120	45	395	1.526	128	61	398	1.647	
50	120	54	395	1.607	142	52	398	1.621	
60	110	45	395	1.626	132	65	398	1.607	

Table – 6B : Results of radiolysis for nickel complexes                                         prepared  in neutral medium

T*	18(26)
[Ni2(SH2)2(SCH2)2(Ac)4]
	19(26)
[Ni2(AnH2)2(SCH2)2(Ac)4]	
	M.P.  0C	^M **	   λ  ***	A   ****	M.P.  0C	^M  **	λ  ***	A        ****	
0	245	30	391	1.622	290	5	400	1.630	
5	260	6	391  398	0.913  1.033	n.m	20	400  384	1.412  1.622	
10	260	2	322	1.592	n.m	21	400	1.916	
15	260	3	391  382	1.516  1.592	n.m	29	400	1.594	
20	260	0	391  382	1.542  1.592	n.m	23	400  381	1.418  1.572	
30	260	5	391  382	2.472  1.582	n.m	12	400  379	1.065  1.413	
    40 	260	5	391  382	1.502  1.582	n.m	17	400  374	0.970  1.371	
50	260	0	391  382	1.580  1.580	n.m	18	400  383	1.465  1.577	
60	260	0	391  382	1.541  1.592	n.m	24	400  366	0.948  1.321	

Table – 7 : Results of radiolysis for nickel complexes                                                          prepared  in neutral medium
T*	20(26)
[Ni2(SH2)2(SCH2)2(CO3)2]
	21(26)
[Ni2(AnH2)2(SCH2)2(CO3)2]	22(26)
[Ni2(PH2)2(SCH2)2(CO3)2]	
	M.P  0C	^M **	   λ  ***	A   ****	M.P.  0C	^M  **	λ  ***	A        ****	M.P.  0C	^M **	λ  ***	A   ****	
0	270	27	390	1.616	n.m	5	407	1.646	290 	16	402	1.634	
5	260	17	390	1.025	n.m	25	407  390	0.863  1.302	260	20	402	1.586	
10	256	17	390	0.877	n.m	18	407  390	0.282  0.495	260	28	402  400	1.527  1.603	
15	254	16	390	0.927	n.m	30	407  395	1.203  1.501	255	52	402  400	1.578  1.589	
20	252	17	390	1.074	n.m	28	407  395	1.124  1.460	250	40	402  400	1.590  1.615	
30	244	17	390	1.075	n.m	26	407  395	1.201  1.503	246	42	402  400	1.592  1.615	
40	240	15	390  354	0.185  1.023	n.m	31	407  395	1.266  1.515	240	30	402  408	1.581  1.680	
50	240	25	390	1.185	n.m	30	407  395	1.353  1.553	238	32	402  408	1.586  1.603	
60	240	16	390  354	0.134  0.958	n.m	30	407  390	0.614  1.007	235	34	402  400	1.580  1.601	

Table – 8 : Results of radiolysis for nickel complexes                                                     prepared  in neutral medium
T*	23(26,27)
[Ni2(SH2)2(STH2)2(NO3)2](NO3)2
	24(26,27)
[Ni2(AnH2)2(STH2)2(NO3)2](NO3)2	25(26,27)
[Ni2(PH2)2(STH2)2(NO3)2](NO3)2	
	M.P.  0C	^M **	   λ  ***	A   ****	M.P.  0C	^M  **	λ  ***	A        ****	M.P.  0C	^M **	λ  ***	A   ****	
0	165	120	409	1.648	143	130	425	1.661	185	160	413	1.644	
5	165	38	409	1.644	140	63	425  379	1.392  1.584	184	48	413	1.206	
10	165	38	409	1.643	150	63	425  374	0.980  1.505	184	50	413	1.284	
15	162	30	409	1.641	150	65	425  375	1.024  1.540	190	35	413	0.943	
20	170	32	409	1.643	170	60	425  374	1.002  1.531	190	47	413	1.642	
30	168	40	409	1.639	150	63	425  377	1.112  1.555	190	48	413	1.540	
40	160	39	409	1.636	150	68	425  374	1.980  1.520	190	50	413	1.232	
50	156	34	409	1.631	150	67	425  375	1.1441.565	190	54	413	1.408	
60	156	31	409	1.630	150	69	425  374	1.196  1.552	190	58	413	1.204	

Table – 9 : Results of radiolysis for nickel complexes                                                    prepared  in neutral medium
T*	26(26,27)
[Ni2(SH2)2(STH2)2(CO3)2]
	27(26,27)
[Ni2(AnH2)2(STH2)2(CO3)2]	28(26,27)
[Ni2(PH2)2(STH2)2(CO3)2]	
	M.P  0C	^M **	   λ  ***	A   ****	M.P.  0C	^M  **	λ  ***	A        ****	M.P.  0C	^M **	λ  ***	A   ****	
0	260	11	425	1.648	264	24	425	1.629	n.m	24	425	1.621	
5	260	36	425	1.644	n.m	51	425  367	0.953  1.538	n.m	48	425  370	0.873  1.374	
10	245	30	425	1.643	260	34	425  367  	0.861  1.430	265	55	425  370	0.921  1.446	
15	258	10	425	1.641	256	14	425  367	0.792  1.400	260	44	425  370	0.975  1.371	
20	236	8	425	1.643	260	25	425  367	0.714  1.375	254	38	425  370	0.948  1.412	
30	258	20	425	1.639	262	20	425  367	0.686  1.453	256	23	425  374	1.230  1.572	
40	260	47	425	1.636	n.m	29	425  367	0.784  1.461	236	11	425  370	1.065  1.413	
50	260	54	425	1.631	n.m	30	425  367	0.813  1.483	264	50	425  370	1.371  1,521	
60	260	50	425	1.630	240	35	425  367	0.844  1.517	264	52	425  370	0.938  1.577	

Table – 10 : Results of radiolysis for nickel complexes                                                        prepared  in basic medium
T*	29(26,27)
[Ni2(SH)2(STH)2]
	30(26,27)                                               [Ni2(AnH)2(STH)2]	31(26,27)
[Ni2(PH)2(STH)2]	
	M.P  0C	^M **	   λ  ***	A   ****	M.P.  0C	^M  **	λ  ***	A        ****	M.P.  0C	^M **	λ  ***	A   ****	
0	290	10	422	1.646	n.m	17	423	1.660	n.m	10	415	1.665	
5	n.m	30	422  424	1.357  1.584	n.m	16	423	1.647	n.m	15	415	1.652	
10	n.m	30	422  424	1.357  1.584	n.m	12	423	1.648	n.m	13	415	1.652	
15	n.m	30	422  424	1.262  1.579	n.m	15	423	1.640	n.m	18	415	1.654	
20	n.m	28	422 426	1.240  1.590	n.m	12	423	1.648	n.m	15	415	1.652	
30	n.m	29	422  424	1.183  1.466	n.m	14	423	1.655	n.m	14	415	1.654	
40	n.m	20	422  424	1.185  1.523	n.m	17	423	1.654	n.m	16	415	1.653	
50	n.m	25	422  426	1.095  1.556	n.m	10	423	1.653	n.m	13	415	1.653	
60	n.m	22	422  428	1.094  1.563	n.m	14	423	1.647	n.m	17	415	1.653	

Complexes 8, 30 and 31 did not show noticable changes with increasing the time of irradiation, this is a very good point and having benefit since these complexes resist the radiation and not affected by ionizing radiation .
According to the observed results . We could propose the following(32-34) : In the complexes that resist gamma rays , we suggest the occurance of ion pair formation leadind to back reaction between emitted electrons and positive ions. In the compound containing electron with drawing groups(32) on aromatic phenyl ring , we could notice that these groups could decrease the stability of the positive ions formed by gamma ray, i.e., increasing their activities towards neutralization with the trapped electrons in  the molecules in solid state . Therefore a kind of repairing and removal of gamma-irradiation effects may have happened in the complexes containing electron with drawing groups . In the complexes containing electron donating groups , in addition to the changes in the intensity of electronic spectra , there have been also changes in molar conductivities and melting points . The increase in molar conductivities refers to the increase in decomposition of the complexes while the decrease  in molar conductivity may be attributed to recombination of ionization products giving rise to dimers, oligomers or polymers(32-34) . 

Conclusion
From the above studies we could conclude three types of effects :
1- Some complexes have been decomposed giving either monomers or may have been decomposed completely by  gamma-irradiation .
2- Other complexes were resistant to the ionizing radiation of gamma-rays due to back reaction between positive ions and emitted electrons .
3-Other complexes polymerized by gamma-irradiation .
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