Noncovalent Dimerization after Enediyne Cyclization on Au(111)

Journal Of The American Chemical Society 138, 10963 - 10967 (2016)

Noncovalent Dimerization after Enediyne Cyclization on Au(111)

D. G. de Oteyza, A. Pérez Paz, Y.-C. Chen, Pedramrazi, A. Riss, S. Wickenburg, H.-Z. Tsai, F. R. Fischer, M. F. Crommie, A. Rubio

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.

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D. G. de Oteyza and A. Pérez Paz contributed equally. ACKNOWLEDGMENT Research supported by the U.S. Department of Energy Office of Basic Energy Sciences Nanomachine Program under contract no. DE-AC02-05CH11231 (STM imaging), by the Office of Naval Research BRC Program (molecular synthesis), by the European Research Council grants ERC-2010-AdG-267374-DYNamo and ERC-2014-STG-635919-SURFINK (computational resources and surface analysis, respectively), by Spanish Grant no. FIS2013- 46159-C3-1-P (simulated reaction landscape), and by Grupos Consolidados UPV/EHU del Gobierno Vasco no. IT-578-13 (simulated dimer binding energy). A.P.P. acknowledges postdoctoral fellowship support from “Ayuda para la Especialización de Personal Investigador del Vicerrectorado de Investigación de la UPV/EHU-2013” and from the Spanish "Juan de la Cierva-incorporación" program (IJCI-2014-20147). E. Goiri is acknowledged for help and discussion on the statistical analysis of interparticle distances.