Department of Chemistry and Laboratory of Organic Optoelectronics and Molecular Engineering of the Ministry of Education, Tsinghua University, Beijing 100084, China.
Inorg Chem. 2011 Mar 21;50(6):2082-93. doi: 10.1021/ic200204p. Epub 2011 Feb 22.
Comprehensive computational modeling of coordination structures, thermodynamic stabilities, and luminescence spectra of uranyl-glycine-water complexes UO(2)(Gly)(n)aq(m) (Gly = glycine, aq = H(2)O, n = 0-2, m = 0-5) in aqueous solution has been carried out using relativistic density functional approaches. The solvent is approximated by a dielectric continuum model and additional explicit water molecules. Detailed pictures are obtained by synergic combination of experimental and theoretical data. The optimal equatorial coordination numbers of uranyl are determined to be five. The energies of several complex conformations are competitively close to each other. In non-basic solution the most probable complex forms are those with two water ligands replaced by the bidentate carboxyl groups of zwitterionic glycine. The N,O-chelation in non-basic solution is neither entropically nor enthalpically favored. The symmetric and antisymmetric stretch vibrations of the nearly linear O-U-O unit determine the luminescence features. The shapes of the vibrationally resolved experimental solution spectra are reproduced theoretically with an empirically fitted overall line-width parameter. The calculated luminescence origins correspond to thermally populated, near-degenerate groups of the lowest electronically excited states of (3)Δ(g) and (3)Φ(g) character, originating from (U-O)σ(u) → (U-5f)δ(u),ϕ(u) configurations of the linear OUO unit. The intensity distributions of the vibrational progressions are consistent with U-O bond-length changes around 5 1/2 pm. The unusually high intensity of the short wavelength foot is explained by near-degeneracy of vibrationally and electronically excited states, and by intensity enhancement through the asymmetric O-U-O stretch mode. The combination of contemporary computational chemistry and experimental techniques leads to a detailed understanding of structures, thermodynamics, and luminescence of actinide compounds, including those with bioligands.
在水溶液中，通过相对论密度泛函方法对铀酰-甘氨酸-水配合物UO(2)(Gly)(n)aq(m)（Gly = 甘氨酸，aq = H(2)O，n = 0-2，m = 0-5）的配位结构、热力学稳定性和发光光谱进行了全面的计算建模。溶剂用介电连续体模型和额外的显式水分子来近似。通过实验和理论数据的协同组合，获得了详细的图像。铀酰的最佳赤道配位数确定为五个。几种配合物构象的能量非常接近。在非碱性溶液中，最可能的配合物形式是两个水分子被两性离子甘氨酸的双齿羧基取代。非碱性溶液中，N,O-螯合既不受熵也不受焓的影响。几乎线性的 O-U-O 单元的对称和反对称伸缩振动决定了发光特征。实验溶液光谱的振动分辨形状在理论上用经验拟合的整体线宽参数进行了重现。计算出的发光起源对应于（3）Δ(g)和（3）Φ(g)特征的最低电子激发态的热平衡占据的近简并群，源自线性OUO单元的（U-O）σ(u)→（U-5f）δ(u)，ϕ(u)构型。振动级数的强度分布与 U-O 键长在 5 1/2 pm 左右的变化一致。短波长足的异常高强度解释为振动和电子激发态的近简并，以及通过不对称 O-U-O 伸缩模式增强强度。当代计算化学和实验技术的结合导致对包括生物配体在内的锕系化合物的结构、热力学和发光的详细理解。
