Understanding the Scarcity of Thorium Peroxide Clusters.

Area of Science:

• Inorganic Chemistry
• Radiochemistry
• Coordination Chemistry

Background:

• Thorium nitrate pentahydrate reacts with 2,2',6',2″-terpyridine (terpy) to form novel clusters.
• Peroxide formation in thorium chemistry is often linked to radiolysis.

Purpose of the Study:

• To synthesize and characterize a trinuclear thorium peroxide cluster.
• To investigate the origin and stability of thorium peroxide complexes.

Main Methods:

• Reaction of thorium nitrate pentahydrate with terpyridine in acetonitrile/methanol.
• Characterization of the resulting trinuclear cluster [Th(O2)(terpy)(NO3)2]3.
• Analysis of peroxide formation via radiolysis of water from 232Th decay.

Main Results:

• Formation of a trinuclear thorium peroxide cluster assembled by bridging peroxide anions.
• The cluster decomposes upon isolation, yielding thorium-terpyridine complexes.
• Peroxide formation is radiolytic, requiring an aged thorium source.

Conclusions:

• Thorium(IV) peroxide complexation is weak and ionic, unlike uranium(VI).
• The stability of thorium peroxide clusters is comparable to zirconium(IV) analogs.
• Radiolysis of water is the likely source of peroxide in aged thorium samples.