18322-83-3Relevant articles and documents
Steric Effects in Photochemical Cycloadditions of 9-Phenanthrenecarboxylates
Itoh, Hiroki,Shibata, Hirofumi,Wagatsuma, Marie,Nanjoh, Mari,Senda, Yasuhisa,et al.
, p. 340 - 343 (1993)
Efficiency of photochemical intramolecular and intermolecular cycloadditoin of 9-phenanthrenecarboxylate-anethole systems is dependent on the structure of anethole moiety.Reduction in reactivity of the anethole moiety by steric effects is explained in terms of decrease in coefficients of frontier orbitals on the double bond due to twisting of the anisyl moiety.
Structural Effects on Twisted Olefin Triplet Lifetimes. Styrene Derivatives
Caldwell, R. A.,Cao, C. V.
, p. 6174 - 6180 (2007/10/02)
The triplet lifetimes in methanol of a series of anisylalkenes and anisylcycloalkenes, including several phenyl analogues, have been determined by nanosecond flash kinetic absorption spectrophotometry with nitrogen laser excitation.Electron-transfer scavenging by paraquat dication, PQ2+, (methyl viologen) afforded the readily detectable reduced species PQ+*.Both triplet lifetimes and rate constants for electron transfer from triplet to PQ2+ were determined.The results indicate that acyclic styrene triplets prefer the twisted, "1,2-biradical" structure.Lifetimes are increased by vinyl deuteration, by increasing alkylation, and by constraint within a small ring; in the absence of geometric constraints, the dominant influence on the triplet lifetimes is the extent of substitution at the double bond.Mechanisms for intersystem crossing are discussed, and the tentative conclusion is reached that nuclear motions are important.