Chiral dendrimers on a Pt(100) surface investigated by scanning tunnelling microscopy

✍ Scribed by Hermann, B. A.; Hubler, U.; Jess, P.; Lang, H. P.; Güntherodt, H.-J.; Greiveldinger, G.; Rheiner, P. B.; Murer, P.; Sifferlen, T.; Seebach, D.

• Publisher: John Wiley and Sons
• Year: 1999
• Tongue: English
• Weight: 408 KB
• Volume: 27
• Category: Article
• ISSN: 0142-2421
• DOI: 10.1002/(sici)1096-9918(199905/06)27:5/6<507::aid-sia521>3.0.co;2-x

✦ Synopsis

Dendrimers are highly symmetrical macromolecules of nanometre scale consisting of branching units attached to a central polyfunctional core. The chiral core or the branching units inÑuence the conformation of the dendrimer. Because dendrimers cannot easily be crystallized for di †raction studies, scanning probe methods are used to investigate the conformation of chiral dendrimers on a metal surface. Dendrimers of di †erent size and symmetry were dissolved in Ðlm cast onto a Pt(100) surface and investigated by scanning tunnelling microscopy (STM). CH 2 Cl 2 , Measurements performed under ambient conditions reveal a quasi-periodic structure that is dependent on the shape of the investigated dendrimers : there is a distinct di †erence between dendrimers of the same generation with two or three branches. Furthermore, dendrimers with two branches di †ering only in chirality seem to pack themselves onto the metal substrate di †erently. Reference measurements of benzene on the Pt(100) surface suggest that the electronic structure probed by the STM tip is probably due to the phenyl rings inside the dendrimer structure. This assumption is supported by low-temperature (77 K) STM measurements, providing higher resolution.