Rofe Karen, Douglas Peter, Morley Christopher P, Webster Christopher A, Pichereau Jeremie G
Chemistry Group, School of Engineering, Swansea University, Singleton Park, Swansea SA2 8PP, UK.
Inorg Chem. 2009 May 18;48(10):4549-56. doi: 10.1021/ic801694r.
We describe the photochemical characteristics of two phosphorescent palladium diselenolenes [Pd(2)(Se(2)C(8)H(12))(2)(PBu(3))(2)] (1) and [Pd(2)(Se(2)C(8)H(12))(2)(PPh(3))(2)] (2) which, to the best of our knowledge, are the first reported examples of luminescent Pd-Se compounds. Both compounds exhibit broadband near-infrared phosphorescence in the solid state, with lambda(max) of 717 nm for 1 and 792 nm for 2 at 298 K, and 752 nm for 1 and 785 nm for 2 at 77 K. No phosphorescence was detected for either compound when they were dissolved in nitrogen-purged acetonitrile or toluene solution at 298 K but they do phosphoresce at 77 K in organic glasses with emission quantum yields of 0.12 (+/-0.01) for 1 and 0.13 (+/-0.01) for 2 in an ethanol/diethylether/toluene (1:2:1) (EDT) glass. Emission lifetimes at 77 K are the same whether in the solid state or in an organic glass with first order fit lifetimes of tau = 18.8 (+/-0.7) micros and 11.5 (+/-0.3) micros for 1 and 2, respectively. Combination of these lifetimes with quantum yields gives radiative lifetimes of 151 (+/-13) micros and 86 (+/-7) micros for compounds 1 and 2, respectively, at 77 K in EDT glass. At 77 K solid state quantum yields are estimated to be of the same order of magnitude as those in glasses, and these decrease by a factor of about 3-5 in going from 77 to 298 K. In the solid state at 298 K emission lifetimes are 1.83 (+/-0.02) micros and 7.0 (+/-0.3) micros for 1 and 2, respectively. We could detect no transients by nanosecond flash photolysis which could be assigned to the triplet state in room temperature solution, and no emission assignable to singlet oxygen across the wavelength range 1200-1350 nm upon 550 nm excitation of either 1 or 2 in acetonitrile solution. We estimate the quantum yield of singlet oxygen formation to be less than about 5 x 10(-4), which is also an upper limit for the yield of triplet states of any significant lifetime in fluid solution. Density functional theory (DFT) calculations of the S(0) to S(1) and T(1) transitions show a shift in molecular orbital character from one with significant -ene pi involvement but very little P involvement in the ground-state to one with less -ene pi but greater P involvement in the excited states; there is also a significant shift in the distribution of involvement of atomic orbitals on the four Se atoms.
我们描述了两种磷光二硒代茂钯化合物[Pd₂(Se₂C₈H₁₂)₂(PBu₃)₂] (1)和[Pd₂(Se₂C₈H₁₂)₂(PPh₃)₂] (2)的光化学特性，据我们所知，它们是首次报道的发光钯 - 硒化合物实例。两种化合物在固态下均表现出宽带近红外磷光，在298 K时，化合物1的λmax为717 nm，化合物2的λmax为792 nm；在77 K时，化合物1的λmax为752 nm，化合物2的λmax为785 nm。当它们溶解在经氮气吹扫的乙腈或甲苯溶液中于298 K时，未检测到任何一种化合物有磷光，但在乙醇/乙醚/甲苯(1:2:1) (EDT)玻璃制成的有机玻璃中于77 K时它们确实会发生磷光，化合物1的发射量子产率为0.12(±0.01)，化合物2的发射量子产率为0.13(±0.01)。在77 K时，无论是固态还是在有机玻璃中，发射寿命相同，化合物1和2的一级拟合寿命分别为τ = 18.8(±0.7) μs和11.5(±0.3) μs。这些寿命与量子产率相结合，在EDT玻璃中于77 K时，化合物1和2的辐射寿命分别为151(±13) μs和86(±7) μs。在77 K时，固态量子产率估计与玻璃中的处于同一数量级，并且从77 K升至298 K时，这些量子产率降低约3至五倍。在298 K的固态下，化合物1和2的发射寿命分别为1.83(±0.02) μs和7.0(±0.3) μs。通过纳秒闪光光解我们在室温溶液中未检测到可归因于三重态的瞬态，并且在乙腈溶液中用550 nm激发化合物1或2时，在1200 - 1350 nm波长范围内未检测到可归因于单线态氧的发射。我们估计单线态氧形成的量子产率小于约5×10⁻⁴，这也是流体溶液中任何具有显著寿命的三重态产率的上限。密度泛函理论(DFT)对S(0)到S(1)和T(1)跃迁的计算表明，分子轨道特征从基态中烯π显著参与但磷参与很少的状态转变为激发态中烯π参与较少但磷参与较多的状态；四个硒原子上原子轨道参与的分布也有显著变化。
