Journal
JOURNAL OF PHYSICAL CHEMISTRY C
Volume 122, Issue 8, Pages 4349-4358Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acs.jpcc.7b12079
Keywords
-
Funding
- Catalysis Science Initiative of the U.S. Department of Energy, Basic Energy Sciences [DE-FG02-03ER15467]
- Direct For Mathematical & Physical Scien
- Division Of Chemistry [1531629] Funding Source: National Science Foundation
Ask authors/readers for more resources
The electronic structure of isolated Cr(VI) sites supported on silica was reinvestigated using multiple, complementary electronic spectroscopies applied to transparent xerogel monoliths. The absorption spectrum exhibits three previously reported peaks, at 22 800, 29 100, and 41 500 cm(-1), as well as a previously unresolved band at ca. 36 900 cm(-1). The emission is a longlived red luminescence with lambda(max) = 13 600 cm(-1), emanating from the lowest excited state. Assignment of the excited states was facilitated using time dependent density functional theory (TD-DFT) calculations performed on cluster models. All of the observed electronic transitions and their energies are accounted for by dioxoCr(VI) sites. The lowest energy observed excitation at 22 800 cm(-1) populates a singlet excited state, while the emitting state is the corresponding triplet state, accessed by intersystem crossing from the singlet state. Spectroscopic bands observed at 29 100, 36 900, and 41 500 cm(-1) were assigned, based on the TD-DFT calculation, to spin-allowed transitions that are consistent with emission polarization anisotropy measurements. Small variations in site symmetry at Cr result principally in inhomogeneous broadening of the spectral bands, as well as a red-edge effect in the photoemission spectrum. There is no evidence for a significant contribution from five-coordinate mono-oxoCr(VI) sites.
Authors
I am an author on this paper
Click your name to claim this paper and add it to your profile.
Reviews
Recommended
No Data Available