Electronic Absorption and Emission Spectra of Binuclear Platinum(II) Complexes. Characterization of the Lowest Singlet and Triplet Excited States of Pt2(H2P2O5)44-

Article abstract of DOI:10.1021/ja00352a011

The low-temperature electronic absorption and emission spectra of single crystals containing a binuclear platinum anion, Pt2(H2P2O5)4^4-, have been measured and analyzed.Absorption systems in the 450- and 360-nm regoins are attributable to transitions to d?*p? excited states ³A_2u and ¹A_2u, respectively).The Pt-Pt stretching frequency in the ³A_2u state (155 cm^-1) is much larger than that (110 cm^-1) in the ground state (the ³A_2u absorption as well as the fluorescence (¹A_2u -> ¹A_1g)and phosphorescence (³A_2u -> ¹A_1g) spectra exhibit Pt-Pt stretching progressions), which accords with the d?*p? description of the excited state.The Pt-Pt bond is calculated to contrast by 0.21 Angstroem in the ³A_2u state (relative to the ground-state value of 2.92 Angstroem).Measurements of the phosphorescence spectrum of Ba2Pt2(H2P2O5)4 at low temperatures (8-4.2 K) confiirm that there are two emitting levels split by 40.9 cm^-1 (origins at 476.55 and 477.48 nm are assigned to the E_u and A_1u spin-orbit components of ³A_2u).