Interfacial Supramolecular Assemblies - Hardcover

Vos, Johannes G.; Forster, Robert J.; Keyes, Tia E.

Hardcover

ISBN 10: 0471490717 ISBN 13: 9780471490715

Verlag: Wiley, 2003

Inhaltsangabe

Describes the supramolecular properties of molecular assemblies that contain a solid phase, offering an integrated approach to measurement and addressibility.

* Offers an integrated approach to measurement and addressibility.
* Features case studies describing the major devices developed using this technology.
* The prospects for the future of interfacial supramolecular assemblies are considered.

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Über die Autorin bzw. den Autor

Robert J. Forster is the author of Interfacial Supramolecular Assemblies, published by Wiley.

Tia E. Keyes is the author of Interfacial Supramolecular Assemblies, published by Wiley.

Johannes G. Vos is the author of Interfacial Supramolecular Assemblies, published by Wiley.

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The field of molecular electronics ranges from well-defined and well-understood phenomena such as non-linear optical responses, to the tantalizing and conceptually difficult areas of computing and information storage at the molecular level.

Supramolecular assemblies, constructed using single electro- or photoactive molecules as building blocks, offer a striking way to create materials whose organized architecture makes them suitable for developing molecular electronic devices. To achieve this objective, one must not only be able to direct the fabrication of the assembly and characterize it fully, it is also important to be able to address the nanoscopic structure, i.e., to connect the everyday macroscopic and nanoscopic worlds. The best approach to realizing this key objective is to use solid surfaces as platforms.

This book describes the properties of supramolecular assemblies that are constructed on solid platforms but where the properties of the support play a very significant role in the overall properties of the system, i.e., its distinct functions can no longer be assigned to the molecular components and the platform on which it is assembled.

In a novel, highly integrated manner, this book describes:

• Fabrication and characterization of interfacial supramolecular assemblies
• Properties and functions of suitable platforms
• Issues of electronic and photonic addressability
• Modes of communication and devices such as molecular wires
• Optoelectronic gates
• Chemosensors developed with this innovat ive approach

This book will be of interest to researchers, final year undergraduates and postgraduates in the areas of supramolecular chemistry, photophysics, electrochemistry and functional materials.

Supramolecular assemblies, constructed using single electro- or photoactive molecules as building blocks, offer a striking way to create materials whose organized architecture makes them suitable for developing molecular electronic devices.

Using solid surfaces as platforms offers the best approach to realizing this key objective. To achieve this objective, one must not only be able to direct the fabrication of the assembly and characterize it fully, but also important is the ability to address the nanoscopic structure, i.e. to connect the everyday macroscopic to the nanoscopic worlds.

Topics discussed include: * Fabrication and characterization of interfacial supramolecular assemblies

* Properties and functions of suitable platforms

* Issues of electronic and photonic addressability

* Modes of communication and devices such as molecular wires

* Optoelectronic gates

* Chemosensors developed with this innovative approach In a novel and highly integrated manner, this book describes the properties of supramolecular assemblies constructed on solid platforms and how the properties of the support can play a very significant role in the overall properties of the system.

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Interfacial Supramolecular Assemblies

By Johannes G. Vos Robert J. Forster Tia E. Keyes

John Wiley & Sons

Copyright © 2003 Johannes G. Vos
All right reserved.
ISBN: 978-0-471-49071-5

Chapter One

Introduction

Interfacial Supramolecular Assemblies comprise an electrochemically addressable solid surface functionalized with a film which incorporates molecular components that can be addressed electrochemically or photochemically. In these assemblies, specific bonding interactions exist between the surface and film and they are generally in contact with a solution. Typical of a supramolecular assembly, the individual building blocks retain much of their molecular character, but the overall assembly exhibits new properties, or is capable of performing a specific function beyond that possible when using the individual components.

1.1 Introductory Remarks

The development of chemistry is continuously reinvigorated by discovery and innovation. Following the discovery of atoms in the 18th century, synthetic techniques were developed and, since the beginning of the 19th century, molecular chemistry involving covalent bonding has been dominant. These synthetic capabilities were complemented by theoretical understanding and structural characterization, e.g. the correct structure of benzene was proposed by Kekule in 1865. At the beginning of the 20th century, coordination chemistry was added to the armor of the chemist when Werner defined the coordination bond and this development greatly promoted the development of inorganic chemistry. At around this time, progress was also made in the development of spectroscopic techniques and the discovery of the spectroscopic lines for the various elements led to the development of quantum chemistry.

During the 1970s, the picture of chemistry was that of a sophisticated science built on a good understanding of bonding and of the physical properties and behavior of compounds. In addition, many synthetic methods had been developed and a number of powerful techniques for their characterization were available. Without techniques such as X-ray diffraction, nuclear magnetic resonance spectroscopy, infrared spectroscopy, mass spectrometry and UV-visible spectroscopy, much of today's chemistry would be unthinkable. Other important developments have been the emergence of separation science, electrochemistry and photophysics. As will be shown below, the latter two techniques are of prime importance for the development of interfacial supramolecular chemistry. With this powerful array of techniques and knowledge, chemists started to consider more and more complicated systems, and as a result, interest in the molecular aspects of biological systems developed rapidly. This has led to a well-developed biochemistry, and has resulted in a much improved understanding of the properties of enzymes, natural photosynthesis, respiration, etc. These studies revealed that the structure of natural systems is controlled by intermolecular forces and the importance of organization and self-assembly was soon recognized.

It is against this background that the interest in intermolecular interactions has developed. The term supramolecular chemistry was introduced in 1978 by Jean-Marie Lehn in an article in the journal Pure and Applied Chemistry and was defined as chemistry beyond the molecule. This definition implies that supramolecular chemistry deals with intermolecular interactions and with molecular assemblies. The central concept of supramolecular chemistry is that of organization. In biological systems, molecular assemblies are able to carry out specific functions because they are arranged in an appropriate manner. For example, in natural photosynthesis, it is not just the spectroscopic and redox features of the components that allow for effective charge separation, but more importantly, their relative orientation and intersite separation. It is this idea of utilizing and understanding organization and interaction that has attracted so many scientists into the area of supramolecular chemistry.

One of the fascinations of scientists has long been the ability of nature to use supramolecular forces to create molecular assemblies for carrying out particular functions. As a result, one of the ultimate aims of supramolecular chemistry is to create molecular devices.

1.2 Interfacial Supramolecular Chemistry

From high-speed molecular computers to optoelectronic switching, technological advances in speed and miniaturization drive the search for novel materials with enhanced electronic properties. Supramolecular chemistry has played a major role in progressing research in this area, leading to novel classes of materials which are capable of light or electrically stimulated chemistry and long-range electronic communication.

Interfacial supramolecular assemblies use well-characterized redox centers and chromophores as building blocks to create assemblies on surfaces that are purposefully structured on the molecular level, while at the same time extending over supramolecular distances. Figure 1.1 illustrates how a surface can play an important, often decisive, role in dictating the overall structure and function of a molecular component. In terms of structure, a high degree of molecular organization can be best achieved by developing supramolecular architectures at solid interfaces. The surface impacts the supramolecular system in three important ways. First, the surface provides a platform for extended two-dimensional organization of the supramolecular adsorbate. Secondly, the packing density of the molecular species on the surface allows the extent and strength of lateral interactions to be controlled so that intermolecular communication, which may be individually weak, can collectively drive the assembly of defect-free structures. Finally, since the surface itself becomes a component of the supramolecular assembly, it participates in supramolecular function without eliminating the identity of each moiety in the structure.

A surface also provides a communicable interface, through which the adsorbate can be addressed directly. In doing so, it provides a powerful means of directing processes within the assembly. For example, if the surface is conducting it may be used to induce vectorial electron transfer.

Creating organized structures is an important goal in interfacial supramolecular chemistry. The Langmuir-Blodgett technique is important for the production of macroscopic materials that are organized on the molecular length scale. This approach allows amphillic molecules to be oriented at the air-water interface and then transferred sequentially onto a solid support. Despite the very elegant research conducted in this area, it seems unlikely that this approach will produce materials with the thermal, mechanical, and chemical stability required for practical applications. For this reason, Langmuir-Blodgett monolayers are not considered in this present book.

Synthetic flexibility is one of the most significant advantages of self-assembly allowing organic, inorganic and biological components to be used as building blocks. Organized molecular films deposited on solid surfaces are of great conceptual interest because their small thickness makes them 'quasi-ideal' two-dimensional systems. They constitute a novel 'bottom-up' approach to creating nanoscale structures. This approach contrasts with 'top-down' approaches that entail making existing devices so small that they eventually finish up as nanosized objects, with dimensions of no more than a few hundred...

Details zur Ausgabe

• Verlag: Wiley
• Erscheinungsdatum: 2003
• Sprache: Englisch
• ISBN 10: 0471490717
• ISBN 13: 9780471490715
• Einband: Gebundene Ausgabe
• Auflage: 1
• Anzahl der Seiten: 408
• Kontakt zum Hersteller: Wiley-VCH GmbH; product_safety@wiley.com; ; Boschstrasse 12; Weinheim; 69469; Deutschland