Metal endohedral fullerenes are large clusters mainly composed by carbon atoms characterized by unique properties. Fullerenes, the third form of solid carbon exhibit peculiar properties whose understanding is relevant for both fundamental studies and technological applications. A systematic investigation of both vibrational and structural properties of M@C82* (M=Y, La and Gd) compounds was performed by means of temperature dependent Fourier Transorf InfraRed (FTIR) and X-ray Absorption Near Edge Structure (XANES) spectroscopy. Among the nine possible isomers of the C82 series: C2v and Cs isomers were synthesized and characterized. Looking at both synchronous and asynchronous correlations of two dimensional (2D)-correlation plots of combined x-ray and InfraRed (IR) data we may support the identification of C2v and Cs isomers. Different energy regions in x-ray and IR spectra have been selected and analyzed in order to distinguish isomers and understand the unique properties of metal-doped fullerene clusters.