Dresden 2006 – wissenschaftliches Programm
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O: Oberflächenphysik
O 33: Scanning probe techniques III
O 33.5: Vortrag
Donnerstag, 30. März 2006, 12:15–12:30, PHY C213
Little Changes - big Effects! Molecular Self-Organization probed by STM. — •B. A. Hermann1, L. J. Scherer2, C. E. Housecroft2, and E. C. Constable2 — 1Dept. of Physics / CeNS, LMU Munich and WMI, Walther-Meissner-Str. 8, 85748 Garching, Germany — 2Dept. of Chemistry, Uni. of Basel, Spitalstrasse 51, 4056 Basel, Switzerland
Aromatic-rich Fréchet-type dendrons are ideally suited to visualisation by scanning tunnelling microscopy (STM) and guarantee excellent self-organization on graphite. Here, asymmetric dendritic wedge-functionalised terpyridine ligands, are studied in a careful comparison of highly resolved 2-D self-organized monolayers on graphite using scanning tunnelling microscopy (STM) and x-ray analysis of crystals of the same molecules. The (sometimes) near atomic resolution in conjunction with x-ray analysis of 3-D crystals allowed us to assign the observed molecular arrangements. The observed molecular pattern appears like being knitted row by row. As the octyl chains of the Fréchet-type dendrons, play a major role in the process of molecular organisation, we also synthesised compounds without the octyl chains but otherwise similar molecular structure. Omitting the octyl chains led to no longer opposing Fréchet wedges. Replacing additionally the inner oxygen atom by a sulphur atom and thus changing an inner bond angle caused completely different symmetric properties in the observed self-organized monolayers. Deposition of dendritic wedge-functionalised terpyridine ligands on HOPG resulted in the formation of well-defined monolayers exhibiting different arrangements depending on small changes in the studied molecules.