Generation of one light-induced metastable nitrosyl linkage isomer in [Pt(NH3)4Cl(NO)]Cl2 in the red spectral range.

One metastable linkage nitrosyl isomer can be generated in [Pt(NH(3))(4)Cl(NO)]Cl(2) by irradiation with light in the red spectral range. The potential energy barrier for the thermal relaxation of the metastable state to the ground state has an amount of E(A) = (0.27 +/- 0.03) eV. The decay follows the Arrhenius law and E(A) is independent of temperature. At room temperature the metastable state has a lifetime of tau = 3.8 x 10(-5) s after generation by pulsed laser illumination. Below T = 100 K about 30% linkage NO isomers can be generated in a powder sample by irradiation with lambda = 658 nm. DFT calculations demonstrate the rotation of the NO ligand from Pt-N-O to Pt-O-N as a unique linkage isomer. Consequently, only one new nu(NO) stretching vibration is detected with a shift from 1673 cm(-1) to 1793 cm(-1) by 120 cm(-1), to higher frequencies in good agreement with the DFT calculations. In the metastable state new electronic absorption bands are observed in the blue-green and near infrared spectral range. The metastable state can be optically accessed via a (5d + pi(NO)) -->pi*(NO) transition. [Pt(NH(3))(4)Cl(NO)]Cl(2) is diamagnetic with a Pt(5d(8)) configuration and thus represents the first {MNO}(8) complex with experimental evidence for a light-induced nitrosyl linkage isomer.