Two Pt−H vibrational bands at 1679 cm⁻¹ and 1392 cm⁻¹ observed with 13-atom Pt clusters supported in LTL zeolite by Fourier Transform Infrared (FTIR) spectroscopy confirms that H atoms bridge two Pt atoms across the edges of the metal cluster. An additional broad absorption band centred near 2200 cm⁻¹ which exhibits some substructure is assigned to low energy electronic excitations across the HOMO–LUMO gap of the developing band structure of the nanocluster.