Intra- and intermolecular vibrational energy transfer in tungsten carbonyl complexes W(CO)5(X) (X = CO, CS, CH3CN, and CD3CN)
Intra- and intermolecular vibrational energy transfer in tungsten carbonyl complexes W(CO)5(X) (X = CO, CS, CH3CN, and CD3CN)
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DOI：
10.1063/1.2737449
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发表时间：
2007-05-28
影响因子：
4.4
通讯作者：
Hamaguchi, Hiro-o
中科院分区：
文献类型：
--
作者：
Banno, Motohiro;Iwata, Koichi;Hamaguchi, Hiro-o
通过亚皮秒时间分辨红外 (IR) 泵浦探针光谱，在九种烷烃溶液中观察到四种羰基钨配合物 W(CO)(6)、W(CO)(5)(CS)、W(CO)(5)(CH3CN) 和 W(CO)(5)(CD3CN) 简并 CO 段的振动能量弛豫。振动激发后 0 到 10 ps 之间，基态红外吸收带的漂白信号表现出各向异性。各向异性成分的衰变对应于分子的旋转扩散或简并CO拉伸模式之间的分子内振动能量转移。各向异性衰减的时间常数 tau(aniso) 显示出明显的溶剂依赖性。通过比较W(CO)(6)的T-1u CO伸缩和W(CO)(5)(CS)的A(1) CO伸缩的结果，旋转扩散的时间常数tau(r)和三种简并振动模式之间的分子内能量转移的时间常数tau(e)分别确定为12和8 ps。 tau(茴香)值随着烷烃溶剂中碳原子数的增加而增加。 10 ps 后，漂白恢复变得各向同性。各向同性衰变代表振动布居弛豫，从 v=1 到 v=0。在庚烷中，W(CO)(5)(CS) 和 W(CO)(6) 各向同性衰变的时间常数 tau(1) 为 140 ps。然而，两种乙腈取代的配合物的 tau(1) 显示出较小的值，为 80 ps。 W(CO)(5)(CH3CN)和W(CO)(5)(CD3CN)的振动能量弛豫通过分子内能量从CO配体到乙腈配体的重新分配而加速。在九种烷烃溶液中，W(CO)(6)的tau(1)值在124和158 ps之间，表现出明显的V形溶剂依赖性，其中癸烷最小，而W(CO)(5)(CH3CN)和W(CO)(5)(CD3CN)的tau(1)值显示出很小的溶剂依赖性。 (C) 2007 年美国物理研究所。
Vibrational energy relaxation of degenerate CO stretches of four tungsten carbonyl complexes, W(CO)(6), W(CO)(5)(CS), W(CO)(5)(CH3CN), and W(CO)(5)(CD3CN), is observed in nine alkane solutions by subpicosecond time-resolved infrared (IR) pump-probe spectroscopy. Between 0 and 10 ps after the vibrational excitation, the bleaching signal of the ground-state IR absorption band shows anisotropy. Decay of the anisotropic component corresponds either to the rotational diffusion of the molecule or to the intramolecular vibrational energy transfer among the degenerate CO stretch modes. The time constant of the anisotropy decay, tau(aniso), shows distinct solvent dependence. By comparing the results for the T-1u CO stretch of W(CO)(6) and the A(1) CO stretch of W(CO)(5)(CS), the time constant of the rotational diffusion, tau(r), and the time constant of the intramolecular energy transfer among the three degenerate vibrational modes, tau(e), are determined as 12 and 8 ps, respectively. The tau(aniso) value increases as the number of carbon atoms in the alkane solvent increases. After 10 ps, the recovery of the bleaching becomes isotropic. The isotropic decay represents the vibrational population relaxation, from v=1 to v=0. In heptane, the time constant for the isotropic decay, tau(1), for W(CO)(5)(CS) and W(CO)(6) was 140 ps. The tau(1) for the two acetonitrile-substituted complexes, however, shows a smaller value of 80 ps. The vibrational energy relaxation of W(CO)(5)(CH3CN) and W(CO)(5)(CD3CN) is accelerated by the intramolecular energy redistribution from the CO ligand to the acetonitrile ligand. In the nine alkane solutions, the tau(1) value of W(CO)(6) ranges between 124 and 158 ps, showing the apparent V-shaped solvent dependence with its minimum in decane, while the tau(1) value shows little solvent dependence for W(CO)(5)(CH3CN) and W(CO)(5)(CD3CN). (C) 2007 American Institute of Physics.