| Autor: |
Fransted KA; Chemical Sciences and Engineering Division, Argonne National Laboratory , 9700 South Cass Avenue, Argonne, Illinois 60439-3113, United States., Jackson NE, Zong R, Mara MW, Huang J, Harpham MR, Shelby ML, Thummel RP, Chen LX |
| Jazyk: |
angličtina |
| Zdroj: |
The journal of physical chemistry. A [J Phys Chem A] 2014 Nov 13; Vol. 118 (45), pp. 10497-506. Date of Electronic Publication: 2014 Jul 25. |
| DOI: |
10.1021/jp504294j |
| Abstrakt: |
In this study, ultrafast optical transient absorption and X-ray transient absorption (XTA) spectroscopy are used to probe the excited-state dynamics and structural evolution of copper(I) bicinchoninic acid ([Cu(I)(BCA)2](+)), which has similar but less frequently studied biquinoline-based ligands compared to phenanthroline-based complexes. The optical transient absorption measurements performed on the complex in a series of polar protic solvents demonstrate a strong solvent dependency for the excited lifetime, which ranges from approximately 40 ps in water to over 300 ps in 2-methoxyethanol. The XTA experiments showed a reduction of the prominent 1s → 4pz edge peak in the excited-state X-ray absorption near-edge structure (XANES) spectrum, which is indicative of an interaction with a fifth ligand, most likely the solvent. Analysis of the extended X-ray absorption fine structure (EXAFS) spectrum shows a shortening of the metal-ligand bond in the excited state and an increase in the coordination number for the Cu(II) metal center. A flattened structure is supported by DFT calculations that show that the system relaxes into a flattened geometry with a lowest-energy triplet state that has a dipole-forbidden transition to the ground state. While the short excited-state lifetime relative to previously studied Cu(I) diimine complexes could be attributed to this dark triplet state, the strong solvent dependency and the reduction of the 1s → 4pz peak in the XTA data suggest that solvent interaction could also play a role. This detailed study of the dynamics in different solvents provides guidance for modulating excited-state pathways and lifetimes through structural factors such as solvent accessibility to fulfill the excited-state property requirements for efficient light harvesting and electron injection. |
| Databáze: |
MEDLINE |
| Externí odkaz: |
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