Showing papers in "Accounts of Chemical Research in 1984"

From organic metals to superconductors: managing conduction electrons in organic solids

Abstract: The conduction of electricity in organic solids, especially the parameters required for metallic electron flow and the phenomena responsible for its permanent interruption or perpetual flow are discussed in detail. Specifically, the permanent interruption, termed metal-to-insulator transition, or perpetual flow, termed metal-to-superconductor, are discussed as exhibited by tetrathiofulvalene (TTF), tetracyanoquinodimethane (TCNQ), tetraselenafulvalene (TTMTSF), and salts of each of these compounds. A rather extensive literature survey is included with 60 references being cited.

Thermodynamics for Processes in Finite Time

Abstract: Thermodynamics serves several functions for chemistry and ita sister sciences and technologies. The first of these historically, and still one of the most important, is the provision of limits on the performance of proceases and devices. The very origins of thermodynamics developed from the creative ways people addressed the problem of how beat to pump water out of mines.’ The provision of limits of performance is the main concern of the work we describe here. Research during the past 9 years has led to new ways of finding natural bounds on performance under the constraint that the system operate at a nonzero rate, thereby giving more realistic bounds than those derived from reversible processes. Some approaches tell us only the limits; others tell us also the process that would yield those limits. Frequently, we can infer how the lower bound on the energy we pay for operating at a nonzero rate depends on that rate of operation. There even exist processes for which no zero-rate reversible counterpart exists.2

On the efficiency and stability of photoelectrochemical devices

Abstract: The author feels it necessary to review critically the state-of-the-art in laboratory prototype cells, the measurement and reporting of efficiencies, and the stability of such devices. He hopes that this review will clear up some confusion among chemists who read about advances in photoelectrochemistry in the various journals, and that it will provide a basis for uniform reporting of efficiencies among photoelectrochemists. 84 references, 4 tables.

Polymerized surfactant aggregates: characterization and utilization

Abstract: The review summarizes the current research and future directions for the use of polymerized vesicles. Methods of synthesis and characterization are described. Their potential uses in catalytic photosensitized water splitting for solar energy conversion and as drug carriers are discussed. 66 references, 6 figures.

Model catalytic studies over metal single crystals

Abstract: The custom-built catalytic reactor, contiguous to the surface analysis system, uses a retraction bellows to support the metal crystal, so that samples may be transferred in situ from the reactor to the surface analysis chamber. The single crystals are normally spotwelded to short, high purity leads and heated by resistors. High purity gases are used to measure kinetics below 2 atm; gas chromatography is used for product analysis. Auger spectroscopy is used to document surface composition. The apparatus has been used to study reactions over single crystals of Ni, Ru, and Rh. These reactions include methanation and hydrogenation which are not sensitive to catalyst structure changes. Hydrogenolysis is a type of reaction which is structure sensitive. These types of reactions are reviewed. These techniques should contribute to the fundamental understanding of heterogeneous catalysis. 43 references, 7 figures.

Molecular Mechanisms of Phototherapy of Neonatal Jaundice

Abstract: The success of phototherapy depends on photochemical transformations of bilirubin within light-exposed tissues. These reactions alter the structure of bilirubin in such a way that the intact molecule or fragments of it can be excreted via the kidney or liver without having to undergo further metabolic modification. So far three photochemical reactions of bilirubin have been shown to occur in vivo, and it is likely that these three together account for most of the effect of light on bilirubin metabolism in jaundiced newborns. The three reactions are photooxidation, configurational isomerization, and structural isomerization. In this presentation I shall discuss briefly some of our evidence for the occurrence of these reactions in vivo and speculate on their relative contributions to the net effect of phototherapy. Since the interpretation of the in vivo studies is very much dependent on knowledge gleaned from in vitro photochemical studies, I shall begin with a discussion of the latter.