Nanosecond CO Photodissociation and Excited-State Character of [Ru(X)(X′)(CO)2(N,N′-diisopropyl-1,4-diazabutadiene)] (X = X′ = Cl or I; X = Me, X′
详细信息 查看全文
- 作者：Anders Gabrielsson ; Mike Towrie ; Stanislav Zá ; liš ; Antoní ; n Vlč ; ek Jr.
- 刊名：Inorganic Chemistry
- 出版年：2008
- 出版时间：May 19, 2008
- 年：2008
- 卷：47
- 期：10
- 页码：4236 - 4242
- 全文大小：1217K
- 年卷期：v.47,no.10(May 19, 2008)
- ISSN：1520-510X
文摘
The character and dynamics of the low-lying excited states of [Ru(X)(X′)(CO)2(iPr-dab)] (X = X′ = Cl or I; X = Me, X′ = I; X = SnPh3, X′ = Cl; iPr-dab = N,N′-diisopropyl-1,4-diazabutadiene) were studied experimentally by pico- and nanosecond time-resolved IR spectroscopy (TRIR) and (for X = X′ = Cl or I) computationally using density functional theory (DFT) and time-dependent DFT (TD-DFT) techniques. The lowest allowed electronic transition occurs between 390 and 460 nm and involves charge transfer from the Ru(halide)(CO)2 unit to iPr-dab, denoted 1MLCT/XLCT (metal-to-ligand/halide-to-ligand charge transfer). The lowest triplet state is well modeled by UKS-DFT-CPCM calculations, which quite accurately reproduce the excited-state IR spectrum in the ν(CO) region. It has a 3MLCT/XLCT character with an intraligand (iPr-dab) 3ππ* admixture. TRIR spectra of the lowest triplet excited state show two ν(CO) bands that are shifted to higher energies from their corresponding ground-state positions. The magnitude of this upward shift increases as a function of the ligands X and X′ [(I)2 < (Sn)(Cl) < (Me)(I) < (Cl)2] and reveals increasing contribution of the Ru(CO)2 → dab MLCT character to the excited state. The lowest triplet state of [Ru(Cl)2(CO)2(iPr-dab)] undergoes a ~10 ps relaxation that is followed by CO dissociation, producing cis(CO,CH3CN),trans(Cl,Cl)-[Ru(Cl)2(CH3CN)(CO)(iPr-dab)] with a unity quantum yield and 7.2 ns lifetime and without any observable intermediate. To our knowledge, this is the first example of a “slow” CO dissociation from a thermally equilibrated triplet charge-transfer excited state.