Theoretical study on mechanism of the photochemical
23rd IUPAC Conference on Physical Organic Chemistry (ICPOC23) 3rd – 8th July 2016 • Sydney • Australia
Theoretical study on mechanism of the photochemical ligand substitution of fac-[ReI(bpy)(CO)3(PR3)]+ complex K. Saita,a,* Y. Harabuchi,a T. Taketsugua and S. Maedaa,* a
Department of Chemistry, Faculty of Science, Hokkaido University, Sapporo, Japan *[email protected] (KS), [email protected] (SM)
The mechanism of the CO ligand dissociation of fac-[ReI(bpy)(CO)3P(OMe)3]+ has theoretically been investigated,1 as the dominant process of the photochemical ligand substitution (PLS) reactions2 of fac-[ReI(bpy)(CO)3PR3]+, by using the (TD-)DFT method. The PLS reactivity can be determined by the topology of the T1 potential energy surface, since the photoexcited complex is able to decay into the T1 state by internal conversions (through conical intersections) and intersystem crossings (via crossing seams) with sufficiently low energy barriers. The T1 state has a character of the metal-to-ligand charge-transfer (3MLCT) around the Franck-Condon region, and it changes to the metal-centered (3MC) state as the Re-CO bond is elongated and bent. The equatorial CO ligand has a much higher energy barrier to leave than that of the axial CO, so that the axial CO ligand selectively dissociates in the PLS reaction. The single-component artificial force induced reaction (SC-AFIR) search3 reveals the CO dissociation pathway in photostable fac-[ReI(bpy)(CO)3Cl] as well, however, the dissociation barrier on the T1 state is substantially higher than that in fac-[ReI(bpy)(CO)3PR3]+ and the minimum-energy seams of crossings (MESXs) are located before and below the barrier. The MESXs have also been searched in fac-[ReI(bpy)(CO)3PR3]+ and no MESXs were found before and below the barrier.
Figure. Photochemical ligand substitution (PLS) reaction and proposed mechanisms for PLS reaction from our results.
References 1. Saita, K.; Harabuchi, Y.; Taketsugu, T.; Ishitani, O.; Maeda, S. Submitted. 2. Koike, K.; Okoshi, N.; Hori, H.; Takeuchi, K.; Ishitani, O.; Tsubaki, H.; Clark, I. P.; George, M. W.; Johnson, F. P. A.; Turner, J. J. J. Am. Chem. Soc. 2002, 124, 11448-11455. 3. Maeda, S.; Taketsugu, T.; Morokuma, K. J. Comput. Chem. 2014, 35, 166-173.
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Theoretical study on mechanism of the photochemical ligand substitution of fac-[ReI(bpy)(CO)3(PR3)]+ complex K. Saita,a,* Y. Harabuchi,a T. Taketsugua and S. Maedaa,* a
Department of Chemistry, Faculty of Science, Hokkaido University, Sapporo, Japan *[email protected] (KS), [email protected] (SM)
The mechanism of the CO ligand dissociation of fac-[ReI(bpy)(CO)3P(OMe)3]+ has theoretically been investigated,1 as the dominant process of the photochemical ligand substitution (PLS) reactions2 of fac-[ReI(bpy)(CO)3PR3]+, by using the (TD-)DFT method. The PLS reactivity can be determined by the topology of the T1 potential energy surface, since the photoexcited complex is able to decay into the T1 state by internal conversions (through conical intersections) and intersystem crossings (via crossing seams) with sufficiently low energy barriers. The T1 state has a character of the metal-to-ligand charge-transfer (3MLCT) around the Franck-Condon region, and it changes to the metal-centered (3MC) state as the Re-CO bond is elongated and bent. The equatorial CO ligand has a much higher energy barrier to leave than that of the axial CO, so that the axial CO ligand selectively dissociates in the PLS reaction. The single-component artificial force induced reaction (SC-AFIR) search3 reveals the CO dissociation pathway in photostable fac-[ReI(bpy)(CO)3Cl] as well, however, the dissociation barrier on the T1 state is substantially higher than that in fac-[ReI(bpy)(CO)3PR3]+ and the minimum-energy seams of crossings (MESXs) are located before and below the barrier. The MESXs have also been searched in fac-[ReI(bpy)(CO)3PR3]+ and no MESXs were found before and below the barrier.
Figure. Photochemical ligand substitution (PLS) reaction and proposed mechanisms for PLS reaction from our results.
References 1. Saita, K.; Harabuchi, Y.; Taketsugu, T.; Ishitani, O.; Maeda, S. Submitted. 2. Koike, K.; Okoshi, N.; Hori, H.; Takeuchi, K.; Ishitani, O.; Tsubaki, H.; Clark, I. P.; George, M. W.; Johnson, F. P. A.; Turner, J. J. J. Am. Chem. Soc. 2002, 124, 11448-11455. 3. Maeda, S.; Taketsugu, T.; Morokuma, K. J. Comput. Chem. 2014, 35, 166-173.
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