Contributions to the coordination chemistry of technetium

The radionuclide^99mTc is widely used in nuclear medical diagnostics. Radiopharmaceuticals containing coordination compounds labeled with^99mTc⁴⁺ or^99mTc⁵⁺ can be rapidly prepared from pertechnetate eluted from a⁹⁹Mo/^99mTc generator. For the optimization of the imaging agent it is essential to determine the exact chemical structure of the Tc complex. This can be achieved by synthesizing macroscopic amounts of the analogous long-lived^99gTc compound and by its analysis by appropriate spectroscopy methods. We have successfully synthesized and characterized new technetium complexes with amino acids and also with ligands containing nitrogen, oxygen and sulfur atoms.     

Contribution to the coordination chemistry of technetium

The universal use of radiophamaceuticals labeled with^99mTc has led to the development of many Tc complexes containing^99mTc⁴⁺ or⁹⁹Tc⁵⁺. In order to assess the correlation between the physiological properties and the chemcial structure of a^99mTc complex, milligramm amounts of the corresponding long-lived^99gTc compound have to be synthesized and analyses. This report describes the synthesis and characterization of several new technetium complexes with ligands containing N, O and S as donor atoms.     

Recent developments in the coordination chemistry of technetium

TMC Literature Highlights-23;Transition Met. Chem.,15, 330 (1990).     

A personal account of some dinitrogen and organometallic chemistry research at the University of Sussex

This article reviews the development of dinitrogen chemistry and some associated organometallic chemistry at the University of Sussex with which the author was directly involved. The establishment of the basic heavy-element halide phosphine chemistry laid the ground for the discovery of dinitrogen complexes of rhenium, osmium, molybdenum and tungsten. From there, some of the first well-defined reactions of coordinated dinitrogen (especially protonation and alkylation) were discovered and the essential mechanisms of such reactions were established. This allowed the development of models for the action of nitrogenases that are still probably the best available. Later work has produced similar models in iron chemistry and a range of organometallic chemistry has been uncovered in the effort to discover parallels between the basic organometallic chemistry of substances such as metal carbonyls, dinitrogen complexes and hydrides in their interactions with acetylenes and cyclpropene.     

EPR spectroscopy in the analytical chemistry of technetium complexes

Electronic Paramagnetic Resonance (EPR) spectroscopy is used for studying paramagnetic Tc²⁺ and Tc⁶⁺ complexes, respectively. Results of liquid and frozen solution studies are discussed as well as those obtained from single-crystal experiments. Structure and bonding properties are derived from the spectral data.     

Computational chemistry in pharmaceutical research: at the crossroads

Computational approaches are an integral part of pharmaceutical research. However, there are many of unsolved key questions that limit the scientific progress in the still evolving computational field and its impact on drug discovery. Importantly, a number of these questions are not new but date back many years. Hence, it might be difficult to conclusively answer them in the foreseeable future. Moreover, the computational field as a whole is characterized by a high degree of heterogeneity and so is, unfortunately, the quality of its scientific output. In light of this situation, it is proposed that changes in scientific standards and culture should be seriously considered now in order to lay a foundation for future progress in computational research.     

Analytical Chemistry Department of the faculty of chemistry at Moscow State University

The history of the Analytical Chemistry Department, teaching and research activities, the structure of the Department, equipment, and some research results are reviewed in view of the 70th anniversary of the Department.     

Art and chemistry: the topochemical principle and Las Meninas of Vel��zquez

The present paper is intended to expose an example of similarity in chemistry and in painting not based on shape or common origin but rather on the concepts they involve. I partly wrote this text in the 1980s. I was then learning solid state chemistry at the Weizmann Institute in Israel. At that time, it became evident to me that there was a possible link between a reaction in the crystalline state and one of the many interpretations of Las Meninas of Velázquez. More precisely, I asked myself if a relation might be found between an organic reaction in a crystal governed by the topochemical principle and the interpretation given by the French philosopher, Michel Foucauld, in his book The Order of Things, of Las Meninas in terms of the topology the gazes of the depicted figures.     

Heavy element chemistry facilities at Texas A&M University

A new program to study the chemistry of the homologs of the transactinide elements is under development, and is centered at the Texas A&M University Cyclotron Institute. New facilities have been designed and/or implemented to enable this research. These include equipment for the production of lanthanide and other targets, a rotating target wheel, an improved recoil transfer chamber, and a customized on-line radiochemical laboratory. Additional target development is being performed at Argonne National Laboratory. The new facilities and equipment are discussed.     

Research on the chemistry of heterocycles at Rostov State University (review)

A summary of the research on the chemistry of heterocyclic compounds conducted at Rostov State University is given. The results of research on the chemistry of azoles conducted in Rostov from 1957 to 1982 are presented. The data obtained relative to the chemistry of benzimidazole and other condensed azole systems (imidazo[1,2-a]benzimidazole and indazole) and the chemistry of 2-diazo- and 2-azobenzimidazoles, unsaturated compounds in the azole series, and organometallic derivatives of azoles are examined.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1589–1604, December, 1982.     

Structural chemistry at Lomonosov Moscow State University: a special issue

Structural Chemistry -     

Electrochemical studies of technetium at a mercury electrode

The electrochemistry of technetium was studied by polarography, cyclic voltammetry and coulometry in chloride and sulfate media as a function of pH in the range 1.5–13. Compounds of Tc(III) and Tc(IV) are produced by reduction of pertechnetate, and the system Tc(III)/Tc(IV) was investigated in acidic media. The potential—acidity diagram of technetium is described for two total pertechnetate concentrations. Evidence for the dismutation of Tc(III) below pH 4 is discussed.     

Thirty years of pyrimidine chemistry in the laboratory of organic chemistry at the Wageningen Agricultural University,The Netherlands (review)

In this review attention is paid to two topics, which were of great interest to us during 30 years of studies in pyrimidine chemistry in our laboratory: first, the development of our concepts of the AIYRORC processes, which occur in ring transformation reactions; second, the intra- and intermolecular inverse Diels-Alder reactions in which the pyrimidine ring acts as the electron poor diazadiene system. Their use in synthetic chemistry is illustrated and evidence is presented, based on experiments and molecular mechanics calculations, that in intermolecular Diels-Alder reactions the geometry of the side-chain plays a vital role.     

Review of the analytical chemistry of melatonin

A survey has been made of procedures, chemical and biochemical, for the separation and estimation of melatonin, the active constituent of the pineal gland. In view of the extremely small amounts of material generally present, discussion is built around chromatographic and spectroscopic techniques leading to a comparison with assays based on the skin-blanching effect of the hormone.     

Current research in gas-phase electron diffraction at the University of Antwerp

The gas-phase molecular structures of norbornane and methyl vinylether have been investigated by joint analysis of electron diffraction, infrared, Raman and microwave spectroscopic data. Constraints were taken from the completely relaxed ab-initio (4–21G) geometry. A range of models was investigated which fit to all the available data. For methyl vinylether the quadratic force field was determined by numerical differentiation of the energy gradient and used to calculate vibrational quantities. Also, features of our new electron diffraction unit are illustrated. A new scheme of densitometric data collection is used, based on a modified ELSCAN 2500 densitometer, and a Z8-microprocessor.