Journal
JOURNAL OF PHYSICAL CHEMISTRY A
Volume 118, Issue 22, Pages 3913-3925Publisher
AMER CHEMICAL SOC
DOI: 10.1021/jp501988g
Keywords
-
Funding
- American Chemical Society Petroleum Research Fund
Ask authors/readers for more resources
Elucidating the molecular dynamics that underlie photoinduced electrocyclization is a critical step toward controlling nonadiabatic photochemistry that enables bond formation. Here we present a comprehensive examination of the photochemical dynamics of o-terphenyl (OTP) in solution. Ultrafast transient absorption measurements demonstrate that OTP cyclizes upon 266 nm photoexcitation to form 4a,4b-dihydrotriphenylene (DHT) on a solvent-dependent time scale of 1.5-4 ps, considerably slower than the nonadiabatic cyclization of related diarylethenes. Correlations in these time scales versus bulk solvent properties reveal that mechanical rather than electrostatic solvent solute interactions impact the excited-state relaxation rate, impeding nuclear dynamics leading toward the conical intersection for cyclization. In contrast, solvent-dependent mechanical interactions are observed to facilitate vibrational relaxation of DHT on time scales of 10-25 ps. DHT decays via thermally activated ring-opening with a lifetime of similar to 46 ns in tetrahydrofuran, 12 orders of magnitude faster than dihydrophenanthrenes. We conclude that the differences in excited-state dynamics of OTP and diarylethenes and the relative stability of their cyclized products are determined by the relative strain induced by twisting the central carbon carbon bond that bridges the terminal phenyl rings in each to enable bond formation. We relate these structure dynamics relationships to the feasibility of photoinduced cyclodehydrogenation of o-arenes and design considerations for molecular photos-witches.
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