Endohedral isomerism in model achiral and chiral La@C58N2 systems

Endohedral structures with La0 or La3+ encapsulated in chiral (1,16)C58N2 or achiral (1,4)C58N2 diazafullerenes were studied at the B3LYP/G-31G*/SDD level. Two stable locations of La0 and La3+ are possible in each cage but only with La0@(1,16)C58N2 can the two isomers coexist. We found that an AIM determined hapticity of the endohedral species selectively differentiates the systems. We predict that there will always exist IR and Raman bands which allow for them to be identified in the presence of the parent cage. For the La0@(1,16) C58N2 molecules and the parent diazafullerene, the Raman spectra are likely to reveal a pre-resonance effect even at 785 nm and it seems possible to selectively excite only one isomer. The calculated electronic spectra suggested a chance to determine the less populated diazafullerene in the presence of the more populated one, be it chiral or achiral. For the chiral endohedral isomers, the calculated VCD spectra are quite dissimilar and the two endohedral isomers and the parent heterofullerene seem to be easily detected. Eventually, we defined the endohedral isomerism as follows: The endohedral isomerism is the phenomenon whereby an internal individuum captured in a cage can occupy more than one stable position without changing the cage connectivity. [Display omitted] •Calculations indicate that only for La0@(1,16) C58N2 system can the two endohedral isomers coexist.•The AIM estimated hapticity of the endohedral species selectively differentiates the isomers.•IR, Raman, UV–Vis, ECD, and VCD spectra were simulated for all molecules.•(1,16)C58N2 and La0@(1,16)C58N2 molecules are likely to reveal a resonance Raman effect at 532 nm.•The La0@(1,16)C58N2 endohedral isomers VCD spectra are substantially dissimilar.