Synthesis, structural analysis, and self-assembly of phenylene ethynylene oligomers and their {F}, {CF} {\textless}sub{\textgreater}3{\textless}/sub{\textgreater} , and {CH} {\textless}sub{\textgreater}3{\textless}/sub{\textgreater} substituted derivat

Percec, S, Getty R, Marshall W, Skidd G, French R.  2004.  


Oligomers consisting of aromatic building blocks separated by alkynyl units were synthesized by Sonogashira cross-coupling of aryl halides with terminal acetylenes. Strong electron acceptors such as {[BOND]F} and {[BOND]CF3} and weak electron donors like {[BOND]CH3} were placed as substituents on one of the benzene rings. Acetyl-protected sulfhydryl groups were attached to one end of these molecules to promote their self-organization on gold surfaces. The electron-transport properties of such self-assembled monolayers {(SAMs)} are highly sensitive to the local order of the molecules in the solid state. Single crystals were analyzed by X-ray diffraction experiments that revealed structural details that could lead to a better understanding of the electron-transport properties. The unsymmetrical substitution of the aromatic rings by electron-active groups in the ortho-, meta-, or para positions resulted in changes of such molecular parameters as bonding and torsion angles and planarity. These parameters, in turn, can affect the angle of the molecular attachment to a gold substrate and the density of the resulting {SAMs.} Patterned {SAMs} of some of these molecules and comparison alkane thiols were obtained on gold by microcontact printing or flooding. The {SAM} thickness was determined by spectroscopic ellipsometry. Surface potential differences between adjacent {SAMs} or between {SAMs} and the gold substrate were measured by scanning surface potential microscopy under ambient conditions. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 541–550, 2004


Journal of Polymer Science Part A: Polymer Chemistry





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