Electroanalytical Chemistry

A Series of Advances: Volume 16

Allen J. Bard, Allen J. Bard

• Publisher: CRC Press
• Year: 2021
• ISBN:
  9781000447286
• Edition: 1
• Topic: Scienze fisiche
• Subtopic: Chimica

This volume provides authoritative reviews in the field of modern electroanalytical chemistry defined in its broadest sense. It is valuable to practicing analytical chemists interested in learning about and applying electroanalytical techniques.

Electrochemical Aspects of Low-Dimensional Molecular Solids

Michael D. Ward

Central Research and Development DepartmentE. I. du Pont de Nemours & Company, Inc. Experimental Station 328, Wilmington, Delaware

I. Introduction

II. Description of Low-Dimensional Solids

III. Redox Properties of Molecular Solids

A. Electrochemical Properties of Molecular Solid Components

B. Role of Redox Behavior in Solid-State Properties

IV. Electrochemical Preparation of Low-Dimensional Solids

A. Basic Principles

B. Examples

C. Mechanistic Aspects

D. Role of Electrochemical Parameters in Crystallization

E. Electrochemical Doping of Low-Dimensional Phthalocyanines

V. Low-Dimensional Solids as Electrode Materials

A. Characteristics of Solid Electrodes

B. Potential Applications of “Synthetic Metal” Electrodes

C. Other Electrode Materials

VI. Summary

Appendix: Definitions of Acronyms

References

I. INTRODUCTION

The trend toward electronic devices with very small dimensions and desirable electronic characteristics has led to extensive investigations of molecular materials, that is, those materials designed on the basis of molecular principles. The intense interest in these materials has been aroused mainly by the promise of facile modification of their physical and electronic properties through rational approaches, which would facilitate investigation of structure-function relationships and possibly the design of molecular-scale electronic devices [1,2]. Interest in molecular materials was heightened with the discovery of the organic conductor TTF-TCNQ (TTF = tetrathiafulvalene, TCNQ = tetracyanoquinodimethane) [3,4], followed by the discovery of superconductivity in (TMTSF)₂X (TMTSF = tetramethyltetraselenafulvalene; X = PF₆^-, CIO₄^-, AsF₆^-, ReO₄^-) [5]. Since that time, the area has grown substantially, including the discovery of numerous organic conductors and superconductors [6 8], electrically conductive organometallic solids [9], and a vast number of conducting polymers [10]. Electronic conductivities at room temperature ranging from semiconducting and insulating values (ca 10^-9 −10^-1 Ω^-1 cm^-1) to actual metallic conductivity (ca 1–10⁵ Ω^-1 cm^-1) have been observed, in addition to the superconducting materials that exhibit zero resistivity at very low temperatures. Optoelectronic properties, such as nonlinear optical phenomena arising from unique lattice structures and intermolecular interactions in these materials [11,12], and cooperative magnetic behavior [13 15], such as ferromagnetism [16], have recently expanded the scope of possibilities for molecular materials.

This review will concern the class of molecular materials designated as molecular solids, which are defined as containing discrete molecular components that have been condensed into an organized framework, generally as a result of intermolecular interactions, crystal forces, or Van der Waals forces. As a corollary, molecular solids can generally be redissolved to their molecular components. They are therefore distinguished from other molecularly designed systems that possess extended covalent networks, such as conducting [10] or redox polymers [17] (e.g., polypyrrole, poly acetylene, or polyvinylferrocene), inorganic chain compounds [e.g., Zintl ions (18)], or two-dimensional layered materials (e.g., metal chalcogenides and molybdates).

Because molecular solids are composed of discrete molecular components, the ability to manipulate and understand the properties of the isolated constituents on the molecular level allows rational modification of the properties of the condensed solid. The properties of the individual molecules play an important role in the unique intermolecular interactions in the crystalline solid state, which ultimately result in the cooperative electronic behavior commonly observed in these materials. To the extent that the electrochemical properties are generally indicative of the electr...