On the Energetics of Conformational Switching of Molecules at and Close to Room Temperature

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• 作者：Stefanie Ditze ; Michael Stark ; Florian Buchner ; André Aichert ; Norbert Jux ; Nicola Luckas ; Andreas G?rling ; Wolfgang Hieringer ; Joachim Hornegger ; Hans-Peter Steinrück ; Hubertus Marbach
• 刊名：Journal of the American Chemical Society
• 出版年：2014
• 出版时间：January 29, 2014
• 年：2014
• 卷：136
• 期：4
• 页码：1609-1616
• 全文大小：644K
• ISSN：1520-5126

文摘

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 脳 10¹³ bit/inch². 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.