Photoinduced Coupling of Acetylenes and Quinone in the Solid State as Preorganized Donor-Acceptor Pairs.
Crystalline electron donor-acceptor (EDA) complexes of various diarylacetylenes (DA) and dichlorobenzoquinone (DB) are isolated and structurally characterized by X-ray crystallography. Deliberate excitation of either the DB acceptor at lambda(DB) = 355 nm or the 1:2 [DA, 2DB] complex at lambda(CT) = 532 nm in the solid state leads to [2 + 2] cycloaddition and identical (isomeric) mixtures of the quinone methide products. Time-resolved (ps) diffuse reflectance spectroscopy identifies the ion-radical pair [DA(*+), DB(*-)] as the reactive intermediate derived by photoinduced electron transfer in both photochemical procedures. The effects of crystal-lattice control on the subsequent ion-radical pair dynamics are discussed in comparison with the same photocouplings of acetylenes and quinone previously carried out in solution.
Bosch
E.
E
Chemistry Department, University of Houston, Houston, Texas 77204-5641.
Hubig
S. M.
SM
Lindeman
S. V.
SV
Kochi
J. K.
JK