Escudero Daniel, Assmann Mariana, Pospiech Anne, Weigand Wolfgang, González Leticia
Institut für Physikalische Chemie, Friedrich-Schiller-Universität, 07743 Jena, Germany.
Phys Chem Chem Phys. 2009 Jun 14;11(22):4593-600. doi: 10.1039/b903603b. Epub 2009 May 5.
A theoretical study of the steric and electronic effects of different substituents on the electronic ground and excited states of (bisphosphine)(eta2-tolane)Pt0 complexes is presented. A natural-bond-order (NBO) analysis has been performed to describe the bonding nature of the "hapto-like" coordination of the Pt atom to the alkyne bond of the tolane group. The results show an important contribution of the pi-back donation in all complexes, amounting to half of the energy associated to the sigma-bonding interaction. A TD-DFT study of the absorption spectra helps rationalizing the photochemistry of the complexes. Metal-ligand charge transfer (MLCT) transitions from the Pt atom to the alkyne are assigned as the photochemical "active" states responsible for C-C bond cleavage. Electronic excitations to the sigma* orbital of the C-Br bond are involved in C-Br bond activation. It is shown that both steric and electronic effects play an important role in determining the presence of these electronic excitations.
本文对不同取代基对（双膦）（η2-二苯乙炔）Pt0配合物基态和激发态的空间效应和电子效应进行了理论研究。进行了自然键序（NBO）分析，以描述Pt原子与二苯乙炔基团炔键的“类配位”键合性质。结果表明，π-反馈给体在所有配合物中都有重要贡献，占与σ键相互作用相关能量的一半。对吸收光谱的TD-DFT研究有助于解释配合物的光化学性质。从Pt原子到炔烃的金属-配体电荷转移（MLCT）跃迁被指定为负责C-C键断裂的光化学“活性”态。对C-Br键的σ*轨道的电子激发参与了C-Br键的活化。结果表明，空间效应和电子效应在决定这些电子激发的存在方面都起着重要作用。
