title: On the energetics of conformational switching of molecules at and close to room temperature.
abstract: We observe and induce conformational switching of individual molecules via scanning tunneling microscopy (STM) at and close to room temperature. 2H-5,10,15,20-Tetrakis-(3,5-di-tert-butyl)-phenylporphyrin adsorbed on Cu(111) forms a peculiar supramolecular ordered phase in which the molecules arrange in alternating rows, with two distinct appearances in STM which are assigned to concave and convex intramolecular conformations. Around room temperature, frequent bidirectional conformational switching of individual molecules from concave to convex and vice versa is observed. From the temperature dependence, detailed insights into the energy barriers and entropic contributions of the switching processes are deduced. At 200 K, controlled STM tip-induced unidirectional switching is possible, yielding an information storage density of 4.9 × 10(13) bit/inch(2). With this contribution we demonstrate that controlled switching of individual molecules at comparably high temperatures is possible and that entropic effects can be a decisive factor in potential molecular devices at these temperatures.
authors.affiliation: Lehrstuhl für Physikalische Chemie II and ‡Lehrstuhl für Theoretische Chemie, Universität Erlangen-Nürnberg , Egerlandstr. 3, 91058 Erlangen, Germany.
authors.forename: Stefanie
authors.initials: S
authors.lastname: Ditze
authors.forename: Michael
authors.initials: M
authors.lastname: Stark
authors.forename: Florian
authors.initials: F
authors.lastname: Buchner
authors.forename: André
authors.initials: A
authors.lastname: Aichert
authors.forename: Norbert
authors.initials: N
authors.lastname: Jux
authors.forename: Nicola
authors.initials: N
authors.lastname: Luckas
authors.forename: Andreas
authors.initials: A
authors.lastname: Görling
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Hieringer
authors.forename: Joachim
authors.initials: J
authors.lastname: Hornegger
authors.forename: Hans-Peter
authors.initials: HP
authors.lastname: Steinrück
authors.forename: Hubertus
authors.initials: H
authors.lastname: Marbach