Gao Xing, Shi Shuo, Yao Jun-Liang, Zhao Juan, Yao Tian-Ming
Shanghai Key Lab of Chemical Assessment and Sustainability, Department of Chemistry, Tongji University, 1239 Siping Road, 200092, Shanghai, PR China.
Dalton Trans. 2015 Nov 28;44(44):19264-74. doi: 10.1039/c5dt03373j. Epub 2015 Oct 22.
Ru(phen)2dppz and other closely related ruthenium(II) complexes containing π-extended ligands were found to be non or weakly emissive in water, while exhibiting significant luminescence intensity growth when bound to DNA, however, a satisfactory interpretation has not been provided on this "light switch" mechanism. In the present study, we investigated the vertical transitions and triplet excited states of Ru(phen)2dppz (1), Ru(phen)2dppzi (2) and Ru(phen)2dppz-idzo (3) in the gas phase and aqueous solution, through time dependent-density functional theory (TDDFT). Based on the optimized (3)MLCT and (3)LLCT structures and energies, we found that the (3)MLCT state might be responsible for the emissions of the complexes. Interesting connections between the singlet vertical transitions and the luminescence properties were noticed. Through ZORA-TDDFT calculation with perturbative SOC, we evaluated the intersystem crossing between the lowest singlet excited state, and both (3)MLCT state and (3)LLCT state, which gave a reasonable explanation for the luminescence properties of these complexes.
Ru(phen)2dppz以及其他含有π-扩展配体的密切相关的钌(II)配合物在水中被发现无发射或发射较弱，而与DNA结合时则表现出显著的发光强度增长，然而，对于这种“光开关”机制尚未给出令人满意的解释。在本研究中，我们通过含时密度泛函理论(TDDFT)研究了Ru(phen)2dppz(1)、Ru(phen)2dppzi(2)和Ru(phen)2dppz-idzo(3)在气相和水溶液中的垂直跃迁和三重激发态。基于优化后的(3)MLCT和(3)LLCT结构及能量，我们发现(3)MLCT态可能是这些配合物发射的原因。注意到单重态垂直跃迁与发光性质之间存在有趣的联系。通过带有微扰自旋轨道耦合的ZORA-TDDFT计算，我们评估了最低单重激发态与(3)MLCT态和(3)LLCT态之间的系间窜越，这为这些配合物的发光性质给出了合理的解释。
