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I-APS Awards:  Samir Farid

Samir Farid of the Eastman Kodak Company is the winner of the 1995 I-APS award. Samir was born in Fayoum, Egypt in 1936. He received B.S. and M.S. degrees from Ain-Shams University, Cairo and a Ph.D. in 1967, working with G. O. Schenck at the Max-Planck-Instit�t f�r Strahlenchemie. After 2 more years at the Max-Planck-Instit�t as a research assistant, he joined the Eastman Kodak Company Research Laboratories in Rochester, NY, 1969, where he is now a Senior Research Associate.

Samir is probably best known for his work in photoinduced electron transfer reactions. Electron transfer has been one of the dominant themes in photochemistry in the last decade, and Samir has been a pioneer in the development of the field. Samir's early work was concerned with establishing the scope of the electron transfer process in photochemical reactions. In the course of this work he was able to show that electron transfer was involved in a wide variety of reaction types including fragmentation, rearrangement, addition, isomerization and oxygenation. Each of Samir's studies was characterized by unusually careful kinetic and mechanistic studies. As the kinetic data for the different reactions accumulated over time, Samir discovered that electron transfer reactions could occur with quite different quantum efficiencies. Samir correctly concluded that the dominant energy wasting step was return electron transfer in the geminate radical-ion pairs. Subsequently, he was able to show that variations in the rate of the return electron transfer reactions were responsible for the differing reaction efficiencies, and that these rates were controlled by the Marcus inverted region effect. The only reason that Samir did not publish these results was that Rudy Marcus convinced him that the reorganization energy he had obtained, ca. 1.7 eV, was unexpectedly high, and therefore his interpretation might not be correct. We now know that 1.7 eV is an entirely reasonable reorganization energy for the solvent separated radical-ion pairs that Samir was studying at the time, and that the lower values expected by Marcus, i.e. ca. 0.5 eV, are characteristic of contact radical-ion pairs. Samir's original work on the inverted region was performed before the famous paper of Miller and Closs was published, but the data derived from the product analysis studies has not been published to this day!

One important result from the steady-state work was the observation of different chemical reactions from the geminate radical-ion pairs and the separated radical ions. Thus, by combining his steady-state product analysis results with those from the photophysical studies from research groups such as those of Albert Weller, Samir was able to demonstrate the important role of the transient exciplex and geminate radical-ion pairs in electron transfer reactions, and to establish a general mechanism. Samir's more recent work has been directed toward photophysical studies of the exciplex and radical-ion pair intermediates. The goals of this work have been to characterize their properties, and to use their reactions as model systems to better understand the fundamental factors which control the rates of electron transfer processes. Among the important contributions from the photophysical work are more quantitative demonstrations of the role of the inverted region in controlling the reaction efficiencies, differentiation of the dynamics of the solvent-separated and contact radical-ion pairs, and demonstrations of the relationships between radiative and non-radiative electron transfer processes.

In addition to electron transfer, Samir's research interests also extend to microenvironmental effects in photochemistry, inclusion complexes, photophysical processes and photochemistry in polymeric matrices, and recently to methods for photocleavage of DNA. Samir has also made many significant contributions in the area of imaging technology where he has several patents relating to photoresist and other imaging applications. Samir invented a new class of visible absorbing sensitizers, the ketocoumarins. He was also one of the first to develop a practical method of photopolymerization for imaging purposes, which could use light of all visible wavelengths. This work represents a wonderful example of the application of excellent basic photochemical research to a problem of great technological importance.

All of Samir's work is characterized by a superb attention to detail and an unwillingness to let even the smallest observation go unexplained. These qualities have allowed Samir to make discoveries that others working in the same fields have missed. Samir's accomplishments have also been achieved with a minimal number of co-workers, and to a significant extent with his own hands. I am pleased to be able to report that Samir still works in the laboratory. He recrystallizes, distills, prepares his own solutions and is truly an expert with a Spex Fluorolog. He has also finally been persuaded to enter the computer age by the friendly user interface of the Macintosh. At one time Samir was the only professional research staff person at Kodak without an internal E-mail account, and an IBM-PC sat in a box in a corner of his office for several years gathering dust. However, Samir's long term isolation from computers has resulted in another unique talent. From personal experience I have discovered that he is an ideal beta tester for computer programs. His unusual approach means that he will inevitably try to use a program in a way that a more experienced user would never dream of, and as a result he finds "bugs" that others would not. A program that Samir can use is truly bomb-proof!

Evidently a fascination with electron transfer processes can be inherited. At the time when the work on the inverted region was underway at Kodak, Samir's son Ramy was working for his Ph.D. with Harry Gray at the California Institute of Technology. Ramy's research topic was electron transfer in binuclear transition metal complexes. One of the goals was to find an example of the inverted region. As Richard Eisenberg of the University of Rochester has said, Samir's house is probably the only one in the world where the inverted region can be discussed at the dinner table!

Photoinduced electron transfer is recognized to be of great importance in Rochester, as it plays a fundamental role in many technologically and economically important processes, including silver halide photography, electrophotography and essentially all imaging mechanisms using visible light. Samir is an associate director of the NSF Science and Technology Center for Photoinduced Charge Transfer at the University of Rochester, which provides an environment for scientists from the Eastman Kodak Company, the Xerox Corporation and the University of Rochester to work together in this important field. He is also an adjunct professor at the University. Everyone in Rochester is delighted that the work of one of the warmest and friendliest personalities in the photochemistry community has been justly recognized. I join all of his friends and colleagues in extending heartiest congratulations to Samir for winning this years award.

Ian R. Gould
Research Laboratories
Eastman Kodak Company
Rochester, NY 14650-2109



 

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