Kimdir ? Nobel ödüllü bilim adamları

 

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Roald Hoffmann

 

 

I came to a happy Jewish family in dark days in Europe. On July 18, 1937 I was born to Clara (née Rosen) and Hillel Safran in Zloczow, Poland. This town, typical of the Pale of the Settlement, was part of Austria-Hungary when my parents were born. It was Poland in my time and is part of the Soviet Union now. I was named after Roald Amundsen, my first Scandinavian connection. My father was a civil engineer, educated at the Lvov (Lemberg) Polytechnic, my mother by training a school teacher.

In 1939 the war began. Our part of Poland was under Russian occupation from 1939-1941. Then in 1941 darkness descended, and the annihilation of Polish Jewry began. We went to a ghetto, then a labor camp. My father smuggled my mother and me out of the camp in early 1943, and for the remainder of the war we were hidden by a good Ukrainian in the attic of a school house in a nearby village. My father remained behind in the camp. He organized a breakout attempt which was discovered. Hillel Safran was killed by the Nazis and their helpers in June 1943. Most of the rest of my family suffered a similar fate. My mother and I, and a handful of relatives, survived. We were freed by the Red Army in June 1944. At the end of 1944 we moved to Przemysl and then to Krakow, where I finally went to school. My mother remarried, and Paul Hoffmann was a kind and gentle father to me until his death, two months prior to the Nobel Prize announcement.

In 1946 we left Poland for Czechoslovakia. From there we moved to a displaced persons' camp, Bindermichl, near Linz, in Austria. In 1947 we went on to another camp in Wasseralfingen bei Aalen in Germany, then to München. On Washington's Birthday 1949 we came to the United States.

I learned English, my sixth language at this point, quite quickly. After P.S. 93 and P.S. 16, Brooklyn, I went on to the great Stuyvesant High School, one of New York's selective science schools. Among my classmates were not only future scientists but lawyers, historians, writers - a remarkable group of boys. In the summers I went to Camp Juvenile in the Catskills, a formative experience. Elinor, my younger sister, was born in 1954.

In 1955 I began at Columbia College as a premedical student. That summer and the next I worked at the National Bureau of Standards in Washington with E.S. Newman and R.E. Ferguson. The summer after I worked at Brookhaven National Laboratory, with J.P. Cumming. These summers were important because they introduced me to the joys of research, and kept me going through some routine courses at Columbia. I did have some good chemistry teachers, G.K. Fracnkel and R.S. Halford, and a superb teaching assistant, R. Schneider. But I must say that the world that opened up before me in my non science courses is what I remember best from my Columbia days. I almost switched to art history.

In 1958 I began graduate work at Harvard. I intended to work with W.E. Moffitt, a remarkable young theoretician, but he died in my first year there. A young instructor, M.P. Gouterman, was one of the few faculty members at Harvard who at that time was interested in doing theoretical work, and I began research with him. In the summer of 1959 I got a scholarship from P.O. Lowdin's Quantum Chemistry Group at Uppsala to attend a Summer School. The school was held on Lidingö, an island outside of Stockholm. I met Eva Börjesson who had a summer job as a receptionist at the school, and we were married the following year.

I came back to Harvard, began some abortive (and explosive) experimental work, and Eva and I took off for a year to the Soviet Union. It was the second year of the U.S.-U.S.S.R graduate student exchange. I worked for 9 months at Moscow University with A.S. Davydov on excitor theory. Eva and I lived in one of the wings, Zona E, of that great central building of Moscow University. My proficiency in Russian and interest in Russian culture date from that time.

On returning to the U.S. I switched research advisors and started to work with W.N. Lipscomb, who had just come to Harvard. Computers were just coming into use. With Lipscomb's encouragement and ebullient guidance, L.L. Lohr and I programmed what was eventually called the extended Hückel method. I applied it to boron hydrides and polyhedral molecules in general. One day I discovered that one could get the barrier to internal rotation in ethane approximately right using this method. This was the beginning of my work on organic molecules.

In 1962 I received my doctorate, as the first Harvard Ph.D. of both Lipscomb and Gouterman. Several academic jobs were available, and I was also offered a Junior Fellowship in the Society of Fellows at Harvard. I chose the Junior Fellowship. The three ensuing years in the Society (1962 - 65), gave me the time to switch my interests from theory to applied theory, specifically to organic chemistry. It was EJ. Corey who taught me, by example, what was exciting in organic chemistry. I began to look at all kinds of organic transformations, and so I was prepared when in the Spring of 1964 R.B. Woodward asked me some questions about what subsequently came to be called electrocyclic reactions. That last year at Harvard was exciting. I was learning organic chemistry at a great pace, and I had gained access to a superior mind. R.B. Woodward possessed clarity of thought, powers of concentration, encyclopedic knowledge of chemistry, and an aesthetic sense unparalleled in modern chemistry. He taught me, and I have taught others.

The 1962 - 65 period was creative in other ways as well: Our two children, Hillel Jan and Ingrid Helena, were born to Eva and me.

In 1965 I came to Cornell where I have been ever since. A collegial department, a great university and a lovely community have kept me happy. I am now the John A. Newman Professor of Physical Science. I have received many of the honors of my profession. I am especially proud that in addition to the American Chemical Society's A.C. Cope Award in Organic Chemistry, which I received jointly with R.B. Woodward in 1973, I have just been selected for the Society's Award in Inorganic Chemistry in 1982, the only person to receive these two awards in different subfields of our science.

I have been asked to summarize my contributions to science.

My research interests are in the electronic structure of stable and unstable molecules, and of transition states in reactions. I apply a variety of computational methods, semiempirical and nonempirical, as well as qualitative arguments, to problems of structure and reactivity of both organic and inorganic molecules of medium size. My first major contribution was the development of the extended Huckel method, a molecular orbital scheme which allowed the calculation of the approximate sigma- and pie- electronic structure of molecules, and which gave reasonable predictions of molecular conformations and simple potential surfaces. These calculations were instrumental in a renaissance of interest in sigma electrons and their properties. My second major contribution was a two-pronged exploration of the electronic structure of transition states and intermediates in organic reactions. In a fruitful collaboration R.B. Woodward and I applied simple but powerful arguments of symmetry and bonding to the analysis of concerted reactions. These considerations have been of remarkable predictive value and have stimulated much productive experimental work. In the second approach I have analyzed, with the aid of various semiempirical methods, the molecular orbitals of most types of reactive intermediates in organic chemistry-carbonium ions, diradicals, methylenes, benzynes, etc.

Recently I and my collaborators have been exploring the structure and reactivity of inorganic and organometallic molecules. Approximate molecular orbital calculations and symmetry-based arguments have been applied by my research group to explore the basic structural features of every kind of inorganic molecule, from complexes of small diatomics to clusters containing several transition metal atoms. A particularly useful theoretical device, the conceptual construction of complex molecules from MLn fragments, has been used by my research group to analyze cluster bonding and the equilibrium geometries and conformational preferences of olefin and polyene metal carbonyl complexes. A satisfactory understanding of the mode of binding of essentially every ligand to a metal is now available, and a beginning has been made toward understand ing organometallic reactivity with the exploration of potential energy surfaces for ethylene insertion, reductive elimination and alkyl migrative insertion reactions. Several new structural types, such as the triple-decker and porphyrin sandwiches, have been predicted, and recently synthesized by others. On the more inorganic side, we have systematically explored the geometries, polytopal rearrangement and substitution site preferences of five, six, seven and eight coordination, the factors that influence whether certain ligands will bridge or not, the constraints of metal-metal bonding, and the geometry of uranyl and other actinide complexes. I and my coworkers are beginning work on extended solid state structures and the design of novel conducting systems.

The technical description above does not communicate what I think is my major contribution. I am a teacher, and I am proud of it. At Cornell University I have taught primarily undergraduates, and indeed almost every year since 1966 have taught first-year general chemistry. I have also taught chemistry courses to non-scientists and graduate courses in bonding theory and quantum mechanics. To the chemistry community at large, to my fellow scientists, I have tried to teach "applied theoretical chemistry": a special blend of computations stimulated by experiment and coupled to the construction of general models - frameworks for understanding.

From Les Prix Nobel. The Nobel Prizes 1981, Editor Wilhelm Odelberg, [Nobel Foundation], Stockholm, 1982