Guest editors’ tribute to Fritz Pragst on the occasion of his 70th birthday

Abstract

This issue is dedicated to Fritz Pragst on the occasion of his 70th birthday on September 9th, 2011. Fritz Pragst is an outstanding scientist who has succeeded to make two scientific carriers in rather different fields of chemistry, first in organic electrochemistry and then in forensic analysis. From 1961 to 1966, Pragst studied chemistry at Humboldt University, Berlin. He finished with a diploma work on the electrochemical reduction of porphyrines and porphyrine metal complexes. His Ph.D. thesis, defended in 1969, concerned the electrochemical oxidation of diazo compounds. In 1976, he has defended his doctor of science thesis which was entitled “Correlations between structure, electrochemical properties and electrochemical luminescence of organic compounds”. The electrochemically generated luminescence (ECL) is the topic to which he has substantially contributed to a number of original papers published in the 1970s and 1980s and for which he is best known in the community of electrochemists. In the last two decades, several reviews as well as monographs dealing with ECL were published; however, two important facets of ECL deserve a much higher attention than had been given so far. To both these facets, Fritz Pragst has considerably contributed: First, it is the use of electron transfer reactions (indirect oxidation or reduction) and/or energy transfer reactions (both in homogeneous phase) to generate selectively and exclusively triplet states as ECL intermediates. The interpretation of emission can be used not only for correction or confirmation of the theoretical energetic considerations but also for estimation of the triplet energies of the studied compounds in an alternative way and, based on known energetic criteria, for the determination of—otherwise unavailable—redox potentials of short-living radical species. Second, it is the mechanistic significance of ECL studies, based on the ECL principle, that the luminescence is a consequence of a strongly exoenergetic electron transfer reaction fulfilling fundamental energetic criteria; the observed emission serves also as an unambiguous proof of formation and existence of highly reactive radical intermediates. They often represent the missing link in investigated reaction mechanisms. This type of ECL is generated at one single potential at one single electrode (originally called “direct-current”) utilizing the follow-up splitting of the primary radical ion. It is a very sensitive alternative method for the interception of even highly unstable intermediates and for the proof of the twoelectron ECE (electrochemical–chemical–electrochemical step) reaction mechanism in electrochemistry. Today, this type of ECL is called ECL with coreactants. J. Ludvik (*) Adademy of Science of the Czech Rep., J. Heyrovský Institute of Physical Chemistry, Dolejskova 3, 182 23 Prague 8, Czech Republic e-mail: jiri.ludvik@jh-inst.cas.cz