Department of Chemistry and Center for Photochemical Sciences, Bowling Green State University, Bowling Green, Ohio 43403, USA.
J Phys Chem A. 2012 Mar 22;116(11):2791-9. doi: 10.1021/jp208532u. Epub 2011 Nov 28.
Ultrafast transient absorption spectra in the deep to near UV range (212-384 nm) were measured for the Cu(II)(MeOH)(5)Cl complexes in methanol following 255-nm excitation of the complex into the ligand-to-metal charge-transfer excited state. The electronically excited complex undergoes sub-200 fs radiationless decay, predominantly via back electron transfer, to the hot electronic ground state followed by fast vibrational relaxation on a 0.4-4 ps time scale. A minor photochemical channel is Cu-Cl bond dissociation, leading to the reduction of copper(II) to copper(I) and the formation of MeOH·Cl charge-transfer complexes. The depletion of ground-state Cu(II)(MeOH)(5)Cl perturbs the equilibrium between several forms of copper(II) complexes present in solution. Complete re-equilibration between Cu(II)(MeOH)(5)Cl and [Cu(II)(MeOH)(4)Cl(2)] is established on a 10-500 ps time scale, slower than methanol diffusion, suggesting that the involved ligand exchange mechanism is dissociative.
在甲醇中，对Cu(II)(MeOH)(5)Cl配合物进行 255nm 的激发，进入配体到金属电荷转移激发态后，测量了深至近紫外范围（212-384nm）的超快瞬态吸收光谱。电子激发的配合物通过无辐射衰减，主要通过反向电子转移，在 0.4-4ps 的时间尺度上快速进行到热电子基态，随后进行快速振动弛豫。一个次要的光化学通道是 Cu-Cl 键的解离，导致铜(II)还原为铜(I)，并形成 MeOH·Cl 电荷转移配合物。基态Cu(II)(MeOH)(5)Cl的消耗扰乱了溶液中存在的几种铜(II)配合物之间的平衡。Cu(II)(MeOH)(5)Cl和[Cu(II)(MeOH)(4)Cl(2)]之间的完全再平衡在 10-500ps 的时间尺度上建立，比甲醇扩散慢，表明涉及的配体交换机制是离解的。
