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Noncovalent Dimerization after Enediyne Cyclization on Au(111)

Abstract:

We investigate the thermally induced cyclization of 1,2-bis(2-phenylethynyl)benzene on Au(111) using scanning tunneling microscopy and computer simulations. Cyclization of sterically hindered enediynes is known to proceed via two competing mechanisms in solution: a classic C1-C6 (Bergman) or a C1-C5 cyclization pathway. On Au(111), we find that the C1-C5 cyclization is suppressed and that the C1-C6 cyclization yields a highly strained bicyclic olefin whose surface chemistry was hitherto unknown. The C1-C6 product self-assembles into discrete noncovalently bound dimers on the surface. The reaction mechanism and driving forces behind noncovalent association are discussed in light of density functional theory calculations.