109720-04-9Relevant articles and documents
Kinetics and Spectroscopic Study of a Ketyl-Phenoxy Biradical Produced by Remote Hydrogen Abstraction
Scaiano, J. C.,McGimpsey, W. G.,Leigh, W. J.,Jakobs, S.
, p. 4540 - 4544 (1987)
Laser flash photolysis of 1 in solution leads to the formation of a short-lived triplet (τT = 13.3 ns in acetonitrile) which decays via hydrogen abstraction from the remote hydroxy group.The resulting 1,13-biradical has a lifetime of 118 ns in acetonitrile and decays almost exclusively by back-hydrogen-transfer in a process that appears to be controlled by intersystem crossing.The valeryl analogue 2 is nonreactive with respect to Norrish II fragmentation in fluid solution (ΦII 0.001), presumably as a result of a shortened triplet lifetime due to efficient intramolecular phenolic quenching.
Organic reactions in liquid crystalline solvents. 5. Intramolecular phenolic quenching of aromatic ketone triplets as a probe of solute conformational mobility in liquid crystals.
Leigh, William J.,Jakobs, Stephanus
, p. 1393 - 1408 (1987)
The effects of liquid crystalline order on the confomational motions involved in end-to-end, intramolecular triplet quenching of aromatic ketones by a suitably situated phenolic moiety have been investigated. Triplet state quenching has been monitored using two independent probes: Norrish II fragmentation quantum yields of valeryl-substituted derivatives and direct lifetime measurements in methyl-substituted ketones, using the corresponding anisyl-substituted ketones as models for triplet state behaviour In the absence of phenolic quenching.Quantum yields for Norrish II fragmentation in the liquid crystalline solvents have been estimated using 4-methoxyvalerophenone (MVP) as the actinometer. The ability of liquid crystalline solvents to inhibit intramolecular phenolic quenching is dependent on both phase type and solute length. In one case, Intramolecular quenching Is completely suppressed In smectic phases, indicating that the conformational motions involved in achieving the quenching geometry are slowed by a factor of at least 103 relative to their rates in non-viscous, isotropic solvents. The Norrish II product ratios from photolysis of MVP in the liquid crystalline solvents are also affected dramatically by liquid crystalline order.
