Stepwise preparation and characterization of molecular wires made of zinc octaethylporphyrin complexes bridged by 4, 4′-bipyridine on HOPG

Abstract

Molecular-scale devices can be made using a step-by-step procedure, in a controllable and highly versatile way. In this report, we describe the growth of molecular wires (MW) from zinc (II) octaethylporphyrin (ZnOEP) assembled on highly oriented pyrolytic graphite (HOPG) by a step-by-step approach using 4,4'-bipyridine (BP) to bridge the porphyrin units, via coordination of the nitrogen atom to zinc. In order to gain an insight into the molecular self-organization of these wires, we carried out a detailed scanning tunnelling microscopy (STM) analysis of each monolayer, using a solid/liquid interface technique, up to a complete ZnOEP/BP/ZnOEP/BP/ZnOEP-assembled structure. The electrical properties of the MWs were assessed by scanning tunnelling spectroscopy (STS) and by current-sensing atomic force microscopy (CS-AFM), showing an increase of electrical resistance with the length of the MW.

Sparse‐coding denoising applied to reversible conformational switching of a porphyrin self‐assembled monolayer induced by scanning tunnelling microscopy

“…These distortions also influence the conductivity of the porphyrins which is an important property for the design of organic electronic systems (Wolfle et al ., ; Ferreira et al . , , ). Recent publications have been reporting studies about the dynamic behaviour of porphyrins, in particular, conformational manipulations using STM (Zhao et al ., ; Kumagai et al ., ; Nandi et al ., ; Lensen et al ., ) and a recent review paper highlights some of the experiments that involved porphyrin manipulation using STM (Auwarter et al ., ).…”

“…Metalloporphyrins are of great interest as they can work as building blocks reacting with other molecular systems in order to build supramolecular structures (Choi et al, 2008;Choi & Frisbie, 2010;Sedghi et al, 2011;Ferreira et al, 2014Ferreira et al, , 2011Zhang et al, 2016). The properties of porphyrins have been a subject of research due to their extraordinary stability given by the four pyrrole groups connected by methine units and a reactive metallic centre enabling charge transfer and coordination to other molecules (Zou et al, 2005;Zou & Chen, 2008).…”

“…For instance, the hemoproteins are an example of nonplanar porphryins that can adopt different molecular conformations controlling the activity of biological systems (Drain et al, 2009). These distortions also influence the conductivity of the porphyrins which is an important property for the design of organic electronic systems (Wolfle et al, 2008;Ferreira et al 2014Ferreira et al , 2011Ferreira et al , 2013. Recent publications have been reporting studies about the dynamic behaviour of porphyrins, in particular, conformational manipulations using STM (Zhao et al, 2013;Kumagai et al, 2014;Nandi et al, 2016;Lensen et al, 2012) and a recent review paper highlights some of the experiments that involved porphyrin manipulation using STM (Auwarter et al, 2015).…”

Bottom-Up Self-Assembled Supramolecular Structures Built by STM at Solid/Liquid Interface

“…Research has been focused on low-cost and versatile methods of material production combined with the necessity of making smaller and denser electronic devices. Molecular electronics is a viable solution to overcome this challenge using individual molecules or molecular assemblies as the active components of an electronic circuit [6,7]. Over the last decade, expectations for this field were driven by i) the possibility of these molecules becoming alternatives to silicon-based technology, that is still-to-this-day the core of the integrated electronic circuits; ii) several synthesis and manufacturing processes that have already been adapted and several techniques made available that allow the preparation of high quality molecular films and the characterization of these devices; iii) the ability to design and model structures at a molecular level; and iv) the application and integration of molecular devices in real-life applications.…”

“…Recently, STM has been used to build molecular systems with multicomponents, e.g. self-assembled monolayers with more than one molecular element or vertical supramolecular structures synthesized in-situ [6,7,14,15]. The experiments are called STM at solid/liquid interface when they occur at interface with a high boiling point solvent which is added to a conductive and atomically flat substrate.…”