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Description
The cyclonatetraenyl (Cnt) anion is nine-membered ring that was first synthesize in 1963 by Katz and Garrat.1 This compounds features two isomers: the cis,cis,cis,cis- Cnt and the cis,cis,cis,trans-Cnt as depicted in Figure 1. At that time, scientist observed spontaneous isomerization from the trans form to the cis one. Given the aromatic character of the fully cis form, it was considered the stable form of the two and quite logically the system was evolving toward stability. Unfortunately, the high sensitivity of the Cnt– ligand, toward protonation and reorganization into 8,9-dihydroindene precluded further analysis.
Despites all these challenges, the Cnt ligand has regained interest in organometallic chemistry to form sandwich complexes.2,3 Our group have expanded this result to a series of lanthanides-containing complexes, where it was shown that a mixture of the cis and trans isomer complexes were observed.4 After careful evaluation of the different stimuli that could cause such species to be isolated, we come to the conclusion that in certain cases the isomerization is photo-induced. Thus, this works focuses on how to control the isomerization of the Cnt- ligand and its complexes using light.
