21516-65-4Relevant articles and documents
Stereospecific nucleophilic trapping of encounter complexes between photoexcited 1-cyanonaphthalene and norbornadiene
Weng, Hengxin,Roth, Heinz D.
, p. 101 - 108 (1998)
Photo-induced electron donor-acceptor reactions between 1-cyanonaphthalene (CNN) and norbornadiene (N) generate products of several structure types. Methanol adducts (1-3) formed in polar solvents are rationalized via the radical cation, N+., and stereospecific (exo-) nucleophilic attack by methanol. In less polar solvents, CNN and N form [2 + 2]-cycloadducts, exclusively on the exo-face of N. In non-polar solvents containing methanol, CNN, N and methanol combine to form 1:1:1 adducts, containing the sensitizer on the endo- and the methoxy groups on the exo-face. The formation of these products is rationalized via the trapping of encounter complexes of different geometries. Any rearrangement of the norbornenyl system can be eliminated, since neither tricyclyl nor 7-methoxynorbornenyl structures are formed. Apparently, the alcohol captures an endo-encounter complex of CNN and N by attack from the exo-face, similar to the attack of methanol on N+..
Rh(III)-photosensitized interconversion of norbornadiene and quadricyclane
Sluggett, Gregory W.,Turro, Nicholas J.,Roth, Heinz D.
, p. 8834 - 8838 (2007/10/03)
The utility of two Rh(III) diimine complexes, Rh(phen)33+ and Rh(phi)2(phen)3+ (phen = 1,10-phenanthroline, phi = 9,10-phenanthrenequinone diimine), as sensitizers for the interconversion of norbornadiene (N) and quadricyclane (Q) has been investigated using steady-state photochemical and laser flash photolysis (LFP) techniques. Irradiation of acetonitrile solutions of Rh(phen)33+ and N causes slow conversion to Q. The reaction is reversible; irradiation of Rh(phen)33+ in the presence of Q leads to N. Irradiation of acetonitrile solutions of Rh(phi)2(phen)3+ and Q yields N. However, this reaction is irreversible; irradiation of the Rh-(III) complex in the presence of N fails to afford Q. Irradiation of methanol solutions of either Rh(III) complex in the presence of N or Q affords minor amounts of two methanol-C7 adducts but fails to quench the N-Q interconversion reaction. The results are consistent with N-Q interconversion via an exciplex intermediate. The Rh(III)-sensitized deazatization of two cyclic azoalkane derivatives (Azo-N, Azo-Q) of N and Q was also investigated. Deazatization was achieved by Rh(phen)33+ but not Rh(phi)2(phen)3+ sensitization. The results are consistent with a mechanism involving triplet energy transfer, but the involvement of exciplex intermediates cannot be ruled out. Bimolecular rate constants for quenching of the Rh(III) excited states by N, Q, Azo-N, and Azo-Q were determined by LFP.
