Lewis Jared D, Clark Ian P, Moore John N
Department of Chemistry, The University of York, Heslington, York YO10 5DD, U.K.
J Phys Chem A. 2007 Jan 11;111(1):50-8. doi: 10.1021/jp065563x.
A [(bpy)Re(CO)3L+] complex (bpy = 2,2'-bipyridine) in which L contains a phenyl-azacrown ether that is attached to Re via an amidopyridyl linking group has been studied by steady state and nanosecond time-resolved resonance Raman spectroscopy. Vibrational band assignments have been aided by studies of model complexes in which a similar electron-donating dimethylamino group replaces the azacrown or in which an electron-donor group is absent, and by density functional theory calculations. The ground state resonance Raman spectra show nu(bpy) and nu(CO) bands of the (bpy)Re(CO)3 group when excitation is exclusively in resonance with the Re --> bpy metal-to-ligand charge-transfer (MLCT) transition, whereas L ligand bands are dominant when it is in resonance with the strong intra-ligand charge-transfer (ILCT) transition present for L ligands with electron-donor groups. Transient resonance Raman (RR) spectra obtained on single color (385 nm) pulsed excitation of the complexes in which an electron-donor group is absent show bpy*- bands of the MLCT excited state, whereas those of the complexes with electron-donor groups show both bpy*- bands and a down-shifted nu(CO) band that together are characteristic of an L-to-bpy ligand-to-ligand charge-transfer (LLCT) excited state. Samples in which a metal cation (Li+, Na+, Ca2+, Ba2+) is bound to the azacrown in the ground state show bands from both excited states, consistent with a mechanism in which the LLCT state forms after metal cation release from the MLCT state. Nanosecond time-resolved RR spectra from two-color (355 nm pump, 500 nm probe) experiments on the electron-donor systems show L-ligand bands characteristic of the LLCT state; the same bands are observed from samples in which a metal cation is bound to the azacrown in the ground state, and their time dependence is consistent with the proposed mechanism in which the rate constant for ion release in the MLCT state depends on the identity of the metal cation.
通过稳态和纳秒时间分辨共振拉曼光谱研究了一种[(bpy)Re(CO)₃L⁺]配合物（bpy = 2,2'-联吡啶），其中L含有一个通过酰胺吡啶连接基团与Re相连的苯基氮杂冠醚。通过对模型配合物的研究辅助进行了振动带归属，在模型配合物中，一个类似的供电子二甲基氨基取代了氮杂冠醚，或者不存在供电子基团，并且通过密度泛函理论计算。当激发仅与Re→bpy金属到配体电荷转移（MLCT）跃迁共振时，基态共振拉曼光谱显示(bpy)Re(CO)₃基团的ν(bpy)和ν(CO)带，而当与具有供电子基团的L配体存在的强配体内电荷转移（ILCT）跃迁共振时，L配体带占主导。在对不存在供电子基团的配合物进行单色（385 nm）脉冲激发时获得的瞬态共振拉曼（RR）光谱显示了MLCT激发态的bpy*⁻带，而具有供电子基团
