Electronic Structure and Excited-State Dynamics of the Molecular Triads: trans-M2(TiPB)2[O2CC6H5-畏6-Cr(CO)
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- 作者：Samantha E. Brown-Xu ; Malcolm H. Chisholm ; Christopher B. Durr ; Terry L. Gustafson ; Vesal Naseri ; Thomas F. Spilker
- 刊名：The Journal of the American Chemical Society
- 出版年：2012
- 出版时间：December 26, 2012
- 年：2012
- 卷：134
- 期：51
- 页码：20820-20826
- 全文大小：386K
- 年卷期：v.134,no.51(December 26, 2012)
- ISSN：1520-5126
文摘
From the reactions between M2(TiPB)4 and HO2CC6H5-畏6-Cr(CO)3 (2 equiv), the title compounds trans-M2(TiPB)2[O2CC6H5-畏6-Cr(CO)3]2, where M = Mo or W, and TiPB = 2,4,6-triisopropylbenzoate have been prepared and characterized. Compound I (M = Mo) was characterized by a single crystal X-ray structural determination which revealed a centrosymmetric MoMo quadruply bonded molecule. Compound I is red and the tungsten complex II is blue as a result of intense metal-to-ligand charge transfer (MLCT), which is principally M2未 to benzoate 蟺* with some chromium t2g participation, according to calculations employing density functional theory. Compound I shows dual emission from S1 and T1 states that are assigned 1MLCT and 3 MoMo未未*, respectively. Both complexes have been studied by time-resolved infrared spectroscopy (TRIR) in the region of the carbonyl stretching frequency. Compound II displays a shift of 谓(CO) to lower energy in both the 1MLCT and 3MLCT states in THF, while I in CH2Cl2 shows 谓(CO) bands shifted to both higher and lower energy. We attribute the shift to higher energy seen for I to a Cr t2g to benzoate 蟺* transition which mixes with the Mo2未 to benzoate charge transfer upon excitation at 514 nm. In THF compound I undergoes a reversible photodissociation, potentially due to CO loss. Based on the TRIR of the carbonyl vibrations, it is proposed that the MLCT states are delocalized over both benzoate Cr(CO)3 groups, as supported by calculations.