EPR investigations on radiation induced chemical transformations in Pd(ClO4)2/i-PrOH/HClO4 system from 77 to 300 K

Abstract The EPR studies have been carried out on gamma irradiated samples of Pd(ClO 4 ) 2 in 9 M/4 M HClO 4 in the presence and absence of isopropanol [i-PrOH (5%, v/v)], in the temperature range of 77–300 K. The EPR studies revealed the formation of Pd + complex, Pd 3+ complex and several radicals such as H , OH , ClO 3 , ClO 4 and O 3 − on radiolysis of these systems. Reduction of Pd 2+ to Pd clusters could not be observed in the absence of i-PrOH and warming of the irradiated sample finally resulted in recovery of Pd 2+ complex. However, in the presence of 5% i-PrOH, strongly oxidizing radicals like OH , ClO 3 and ClO 4 are suppressed and (CH 3 ) 2 C OH radical was produced along with reducing species like H . EPR spectra in these strongly reducing conditions showed formation of Pd + complex, which on heating above 230 K, disproportionated into Pd 0 and Pd 2+ complex and finally lead to formation of Pd metal aggregates. Simultaneously, pulse radiolysis technique has been employed as an alternative method to verify the EPR observations.