Thermal stability of iron-sulfur clusters

Area of Science:

• Physical Chemistry
• Materials Science
• Surface Science

Background:

• Iron-sulfur clusters are crucial in various chemical and biological processes.
• Understanding their thermal stability is key to controlling their reactivity.
• Previous studies focused on iron-oxide clusters, showing different decomposition pathways.

Purpose of the Study:

• To investigate the thermal decomposition of free cationic iron-sulfur clusters (Fe_xS_y⁺).
• To determine the temperature-dependent fragmentation patterns and identify stable cluster formations.
• To elucidate the fragmentation mechanisms and compare them with iron-oxide clusters.

Main Methods:

• Collisional post-heating of iron-sulfur clusters (Fe_xS_y⁺) in the temperature range of 300–1000 K.
• Mass spectrometry to analyze the resulting fragment distributions.
• First-principles calculations to explore potential fragmentation pathways and cluster stability.

Main Results:

• Preferential formation of stoichiometric (y=x) or near-stoichiometric (y=x±1) clusters with increasing temperature.
• Fe₄S₄⁺ is abundant up to 600 K; Fe₃S₃⁺ and Fe₃S₂⁺ dominate between 600–800 K.
• Fe₂S₂⁺ becomes the most abundant cluster above 800 K, indicating significant stability.

Conclusions:

• Thermal decomposition follows a sequential fragmentation mechanism involving loss of S, Fe, or FeS units.
• A proposed mechanism includes cluster isomerization prior to fragmentation.
• Iron-sulfur cluster fragmentation contrasts sharply with iron-oxide cluster dissociation, highlighting unique stability and reactivity.