Different structures have been proposed so far for the C-92 isomer that encapsulates M3N (M = La, Ce, Pr). We show here that the electrochemical properties of the predicted most abundant (thermodynamic) isomer for La3N@C-92 does not agree with experiment. After a systematic search within the huge number of possible C-92 isomers, we propose other candidates with larger electrochemical gaps for La3N@C-92 before its structure could be finally determined by X-ray crystallography. We do not discard that the thermodynamic isomer could be detected in future experiments though.