Recently, several reports have revealed the covalency of Ln/An-ligand interactions involving the f-orbitals of metal complexes by using X-ray absorption. The XANES spectra at the Pt L3-edge are shown in Figure . A white line shift from 11562.5 eV (peak top of the edge of the standard sample of Pt foil) to 11563.5 eV (for 1), and 11563.4 eV (for 2) was observed. The spectra were simulated by FDMNES package (Figure ). and the results are similar to the XANES spectral features of tetrakis-m-pyrophosphitodiplatinate(II) ([Pt2(P2O5H2)4] 4-) which has Pt-Pt bond. In addition, we measured single-crystal polarized Xray absorption spectra of 2 (Figure , beam size (< 100 m) is small enough to bc plane of the crystal (200-300 m per one side).) at different crystal axes with orientational information which allowed us to estimate the electronic state to estimate the electronic state of the metal centre. At the Pt LIII-edge, 2 showed that a weak white line (WL) absorption in the Pt-Ln-Pt direction (c direction: the direction perpendicular to Pt dx2-y2), but a strong WL absorption in the vertical direction (The results of density of states (DOS) calculation also supported the fact (Figure )). On the other hand, at the Ln LIII-edge, contrast results were obtained. In 2, the WL absorption is the strongest in the Pt-Ln-Pt (parallel) direction, but weak at the perpendicular direction as well as at 45 degrees from c axis. The 2p→5d transition is originally non-oriented (The results of DOS calculation also supported the fact (Figure ).), but the introduction of electrons into the 4f band shields the nuclear potential from the 5d band. In other words, if the covalency between Ln and the ligand is high (or less ionic), the absorption intensity will increase.