UROP Project

Interaction of fluorenone excited states with the stilbenes

Energy transfer, electron transfer

Research Mentor: Dr. Jack Saltiel, he, him
Department, College, Affiliation: Chemistry & Biochemistry, Arts and Sciences
Contact Email: jsaltiel@fsu.edu
Research Assistant Supervisor (if different from mentor): Ms. Sulthana Fehroza Parambilpeediyakkal Research Assistant
Research Assistant Supervisor Email: sp22be@fsu.edu
Faculty Collaborators: Dr. Edwin F. Hilinski He
Faculty Collaborators Email: hilinski@chem.fsu.edu

Looking for Research Assistants: Yes
Number of Research Assistants: 1
Relevant Majors: Chemistry
Project Location: On FSU Main Campus
Research Assistant Transportation Required:
Remote or In-person: In-person
Approximate Weekly Hours: at least 10, Flexible schedule (Combination of business and outside of business. TBD between student and research mentor.)
Roundtable Times and Zoom Link:
Not participating in the roundtable

Project Description

The inefficiency of fluorenone triplet energy transfer to the stilbenes
Although rediscovered recently,1 the fluorenone triplet (3FL*) sensitized photoisomerization of the stilbenes (1St) has long been known.2,3 A puzzling aspect of the triplet energy transfer process is that careful quantum yield measurements revealed that it is only about ~85% efficient for trans-stilbene and less so for cis-stilbene.4,5 Caldwell has suggested quenching via unproductive decay from a 3FL*St exciplex,4 and a similar explanation was proposed by Valentine and Hammond,5 but definitive evidence for this or other explanations is still lacking.
We propose to reinvestigate the fluorenone/stilbene interaction in order to determine the cause of energy wastage in triplet energy transfer. The possibility of electron transfer from excited fluorenone singlets to the stilbenes was considered,4,5 but rejected because there was little fluorenone fluorescence quenching by the stilbenes. However, there was ambiguity in this finding (see footnote 12 in ref 4). In view of the very high stilbene concentrations that were used in the photoisomerization studies, we propose to reinvestigate fluorenone fluorescence quenching. Electron transfer can also occur from the triplet excited state. We propose to investigate the interaction of fluorenone excited states with the stilbenes using fs and ps pulse excitation to monitor the transient absorption spectra of all excited states and radical ion intermediates.

References
(1) Kozlowski, P. M.; Saha, S.; Maity, B.; Cavallo, L.; Thompson, L. M. Mechanistic Explanation of Enhanced E → Z Photocatalyzed Isomerization Kinetics. J. Phys. Chem. Lett. 2026, 17, 1147−1154.
(2) Saltiel, J.; Hammond, G. S. Mechanisms of photochemical reactions in solution. XVII. cis-trans isomerization of the stilbenes by excitation transfer from low energy sensitizers. J. Am. Chem. Soc. 1963, 85, 2515-2516.
(3) Hammond, G. S.; Saltiel, J.; Lamola, A. A.; Turro, N. J.; Bradshaw, J. S.; Cowan, D. O.; Counsell, R. C.; Vogt, V.; Dalton, C. Mechanisms of photochemical reactions in solution. XXII. Photochemical cis-trans isomerization. J. Am. Chem. Soc. 1964. 86, 3197-3217.
(4) Caldwell, R. A.; Gajewski, R. P. Fluorenone-photosensitized isomerization of trans-stilbene. Inefficiencies both in intersystem crossing and in triplet excitation transfer. J. Am. Chem. Soc. 1971, 93, 532-534.
(5) Valentine Jr, D.; Hammond, G. S.; Mechanisms of photochemical reactions in solution. LXVII. Energy wastage in photosensitized isomerization of the stilbenes. J. Am. Chem. Soc. 1972. 94, 3449-3454.


Research Tasks: Literature Review
Data Collection
Data Analysis

Skills that research assistant(s) may need: Best if student has already taken CHM 2211L