Hans Kuhn (physical chemist)

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Hans Kuhn (1975)

Hans Kuhn (born December 5, 1919 in Bern ; † November 25, 2012 in Troistorrents / Switzerland ) was a Swiss professor of physical chemistry and director at the Max Planck Institute for Biophysical Chemistry (Karl Friedrich Bonhoeffer Institute) in Göttingen .

Life

Hans Kuhn studied chemistry at the ETH Zurich from 1938 to 1942 and graduated as an engineer-chemist. He then worked as an assistant at the University of Basel, where he in 1944 when Werner Kuhn Dr. phil. doctorate and habilitation in 1946 . From 1946 to 1947 he worked as a post-doctoral student with Linus Pauling at the California Institute of Technology in Pasadena and in 1950 for a few months with Niels Bohr in Copenhagen. From 1951 to 1953 Hans Kuhn was Professor at the University of Basel, from 1953 to 1970 Professor and Director of the Institute for Physical Chemistry at the Philipps University of Marburg . From 1970 until his retirement in 1985 he was head of the “Molecular System Design” department at the Max Planck Institute for Biophysical Chemistry (Karl Friedrich Bonhoeffer Institute) in Göttingen.

Fritz Peter Schäfer , Peter Fromherz , Horst-Dieter Försterling , Viola Vogel and Dietmar Möbius were students of Hans Kuhn; Erwin Neher was an assistant in his department. She married Elsi Hättenschwiler in 1948 and gave birth to the children Elisabeth, Andreas, Eva and Christoph. Elsi died in 2004.

Scientific work

Hans Kuhn began his doctoral thesis with the investigation of the untangling of thread molecules in flowing solution. Werner Kuhn suggested replacing the thread molecule with a dumbbell model to simplify the theoretical treatment. Hans Kuhn was enthusiastic about the simplicity and the success of the model in the quantitative analysis of a large number of experiments. This experience, supported by the work with Linus Pauling and Niels Bohr, was decisive for Hans Kuhn's life work in research. Polymers were first described by Werner Kuhn in 1934 as chains of statistical thread elements. In 1943 the statistical preference element was defined. Today it is referred to as the Kuhn length . In the textbook “Principles of Physical Chemistry” it is called “statistical chain element”. In order to describe the behavior of coiled thread molecules more precisely than with the dumbbell model, Hans Kuhn made macroscopic models of molecule coils and examined their hydrodynamic behavior.

Polyenes: potential energy (depressions due to atomic cores neglected) and π electron density. a) Instability with the same bond lengths. b) Stabilization through bond length alternation through bond lengths consistent with π electron density (BCD) approximation.

With Pauling he tried to explain the absorption of polyenes using the electron gas model, which did not succeed. Two years later he saw that the model, applied to cyanine dyes, resulted in a quantitative agreement of the expected spectra with the experiment. He saw the reason for his failure with the polyenes in the fact that assuming the same bond lengths an instability occurs, which leads to an alternation between single and double bonds, caused by the condition of self-consistency between the assumed bond lengths and the calculated π-electron density distribution. Only in this way could he understand the absorption spectra of the polyenes. The assumption was later justified theoretically. This effect is often referred to as Peierls instability : starting from a linear chain of equidistant atoms, Peierls applied a first-order perturbation calculation with Bloch wave functions, but he did not show the self-consistency that leads to the alternation of single and double bonds. The special properties of conductive polymers are based on the theoretical relationship between bond alternation and bond length compensation. The electron gas model and its refinements evolved into a theory of the light absorption of organic dyes. In Marburg, Hans Kuhn and Fritz Peter Schäfer (shortly before the age of the digital computer) developed an analog computer to solve the two-dimensional Schrödinger equation . This space-filling computer was used by Hans Kuhn's group to calculate the bond lengths of interesting π-electron systems.

(a) Model for the formation of a first, replicating oligomer R. (b) Very special place on the prebiotic earth. Arrow: very special cyclical change of temperature and many other special conditions that happen to prevail here. (c) Evolution of increasingly complex self-reproducing forms by occupying areas with properties that are increasingly difficult to overcome.

At the beginning of the 1960s, Hans Kuhn thought of a new paradigm in chemistry, the synthesis of different molecules that structurally fit into one another in such a way that they represent functional components, which as a whole form a pre-planned functional unit, a supramolecular machine. His group constructed prototypes of such machines by developing new techniques for the production and manipulation of Langmuir-Blodgett films . Today they are known as Langmuir-Blodgett-Kuhn layers (LBK layers) or as LBK films. The many new processes were developed in close collaboration with Dietmar Möbius and should therefore be referred to as Langmuir-Blodgett-Möbius-Kuhn layers (LMBK layers).

Closely related to the problem of manufacturing supramolecular machines was the question of the origin of life . Hans Kuhn understood his contribution to be the search for a theoretically consistent and chemically plausible path made up of many successive physical-chemical steps that leads to a genetic apparatus. The process itself is in accordance with thermodynamics. The origin of life is not a special problem of thermodynamics. Certain steps are particularly significant in understanding their mechanism, such as moving from a replica-translation apparatus to a replica-transcription-translation apparatus. In this picture, in an attempt to understand the origins of life, the experimenter's imagination and skill in making supramolecular machines must be replaced by a very special random environment in a very special place on prebiotic earth and elsewhere in the universe that contains the Process drives. The unifying paradigm has led to the construction of simple supramolecular machines and to the finding of a theoretically consistent path to an apparatus which is fundamentally the same as the genetic apparatus of biology. This required simple model concepts to describe complex situations. In the further development in various laboratories, important new experimental methods were invented and further developed, which led to a divergence: supramolecular chemistry , molecular electronics , systems chemistry and important contributions to nanotechnology . It is stimulating and beneficial to keep an eye on the interconnection of these forward-looking areas. They should be included in a modern physical chemistry textbook.

After his retirement , Hans Kuhn, his son Christoph and Horst-Dieter Försterling developed his early work on electron density and bond lengths, a predecessor of "Density functional theory" (DFT), to a bond length consistent with the π-electron density BCD method. He contributed to the understanding of the photosynthesis of the purple bacteria, the proton pump of the halobacteria and the ATP synthase motor.

Awards

Fonts

  • The Electron Gas Theory of the Color of Natural and Artificial Dyes. In: Laszlo Zechmeister (Ed.): Progress in the Chemistry of Organic Natural Products. 16, 169, 1958, p. 404.
  • with Horst-Dieter Försterling: Physical chemistry in experiments. An internship. Verlag Chemie, Weinheim 1971, ISBN 3-527-25343-2 .
  • with Horst-Dieter Försterling: Practice of physical chemistry. Basics, methods, experiments. 3rd edition Wiley-VCH, Weinheim 1991, ISBN 3-527-28293-9 .
  • with Dietmar Möbius: Monolayer assemblies. In Investigations of Surfaces and Interfaces. In: Bryant William Rossiter, Roger C. Baetzold (Eds.): Physical Methods of Chemistry Series. Part B, Chapter 6, Vol. 9B. 2nd Edition. Wiley, New York 1993.
  • with Horst-Dieter Försterling, David H. Waldeck: Principles of Physical Chemistry. 2nd Edition. Wiley, Hoboken 2009, ISBN 978-0-470-08964-4 .

Web links

Individual evidence

  1. ^ Obituary by the Max Planck Institute. Retrieved December 6, 2012
  2. ↑ a b c d e f g h i j k l m n Brief overview of the development of chemistry at the University of Marburg from 1609 to the present. (PDF; 4.4 MB) Ninth, improved and expanded edition. Chemistry Department at Philipps University, February 2020, p. 77 , accessed on March 28, 2020 .
  3. ↑ History of the Max Planck Institute for Biophysical Chemistry in Goettingen ( Memento from February 11, 2007 in the Internet Archive )
  4. ↑ dumbbell model
  5. ↑ H. Kuhn: Fascination in Modeling Motifs , Chapter 6 in R. Jaenicke and G. Semanza (Eds.) Selected Topics in History of Biochemistry: Personal Recollections VI (Comprehensive Biochemistry Vol 41) Elsevier Science 2000.
  6. ↑ W. Kuhn: About the shape of thread-like molecules in solutions Kolloid Zeitschrift 68: 2 (1934).
  7. ↑ W. Kuhn and H. Kuhn: The question of the rolling up of thread molecules in flowing solutions Helv. Chim. Acta 26: 1394 (1943).
  8. ↑ a b Principles of Physical Chemistry by Hans Kuhn, Horst-Dieter Försterling and David H. Waldeck, 2nd Edition, Wiley, Hoboken (2009)
  9. ↑ H. Kuhn: Viscosity, sedimentation, and diffusion of long-chain molecules in solution as determined by experiments on large scale models. J. Colloid Sci. 5: 331 (1950).
  10. ↑ H. Kuhn: Electron gas model for the quantitative interpretation of the light absorption of organic dyes In: J. Helv. Chim. Acta , Volume 31, 1948, p. 1441.
  11. ↑ H. Kuhn: A quantum mechanical theory of light absorption of organic dyes and similar compound In: J. Chem. Phys. , Volume 17, 1949, p. 1198.
  12. ^ A b F. Bär, W. Huber, G. Handschig, H. Martin and H. Kuhn: Nature of the free electron gas model. The case of the polyenes and polyacetylenes. In: J. Chem. Phys. , Volume 32, 1960, p. 470.
  13. ↑ RE Peierls : On the theory of the electrical and thermal conductivity of metals Ann. Phys. 4, 1930, pp. 121-148.
  14. ^ RE Peierls: Quantum theory of solids Clarendon, Oxford 1955.
  15. ^ RE Peierls: Surprises in Theoretical Physics Princeton University Press, Princeton 1979, p. 73.
  16. ^ RE Peierls: More Surprises in Theoretical Physics Princeton University Press, Princeton 1991, p. 29.
  17. ^ A b H. Kuhn: The Electron Gas Theory of the Color of Natural and Artificial Dyes . Progress in the Chemistry of Organic Natural Products (L. Zechmeister ed.) 16: 169 (1958) and ibid. 17: 404 (1959).
  18. ↑ H. Kuhn: Newer studies on the electron gas model of organic dyes. Dedicated to Werner Kuhn, Basel, on the occasion of his 60th birthday. In: Angew. Chem. , Vol. 71, 1958, pp. 93-101.
  19. ↑ FP Schäfer: Analog computer and automatic recorder for determining the stationary wave functions and energy levels of a particle in a two-dimensional potential field , dissertation Marburg 1960.
  20. ^ H. Kuhn, W. Huber, G. Handschig, H. Martin, F. Schäfer, F. Bär: Nature of the Free Electron Model. The Simple Case of the Symmetric Polymethines. In: J. Chem. Phys. , Volume 32, 1960, p. 467.
  21. ↑ H. Kuhn: Analogy considerations and analog computers for the quantum mechanical treatment of the light absorption of the dyes. ( Memento of July 4, 2008 in the Internet Archive ) In: Chimia , Volume 15, 1961, pp. 53-62.
  22. ↑ FF Seelig, W. Huber, H. Kuhn: Analogy considerations and analog computers for the treatment of the correlation of π electrons. In: Journal of Nature Research A . 17, 1962, pp. 114–121 ( PDF , free full text).
  23. ^ HD Försterling, W. Huber, H. Kuhn: Projected electron density method of π-electron systems I. Electron distribution in the ground state. In: Int. J. Quant. Chem. , Vol. 1, 1967, p. 225.
  24. ^ HD Försterling, H. Kuhn: Projected electron density method of π-electron systems II. Excited states. In: Int. J. Quant. Chem. , Vol. 2, 1968, p. 413.
  25. ↑ H. Kuhn: "Attempts to produce simple organized systems of molecules" Negotiations of the Swiss Natural Research Society, 245–66 (1965)
  26. ↑ H. Bücher, KH Drexhage, M. Fleck, H. Kuhn, D. Möbius, FP Schäfer, J. Sondermann, W. Sperling, P. Tillmann, J. Wiegand: Controlled transfer of excitation energy through thin layers. In: Molecular Crystals , Volume 2, 1997, p. 199.
  27. ^ H. Kuhn, D. Möbius: Systems of monomolecular layers-assembling and physico-chemical properties. In: Angew. Chem. Int. Ed. Engl. , Vol. 10, 1971, pp. 620-637.
  28. ^ H. Kuhn: Self-organization of molecular systems and evolution of the genetic apparatus. In: Angew. Chem. Int. Ed. Engl. , Vol. 11, 1972, pp. 798-820.
  29. ^ H. Kuhn: Model consideration for the origin of life. Environmental structure as stimulus for the evolution of chemical systems. In: Naturwissenschaften , Volume 63, 1976, pp. 68-80.
  30. ^ H. Kuhn, J. Waser: Molecular self-organization and the origin of life. In: Angew. Chem. Int. Ed. Engl. , Vol. 20, 1981, pp. 500-520.
  31. ^ H. Kuhn, J. Waser: A model of the origin of life and perspectives in supramolecular engineering. In: J.-P. Behr (editor): Lock-and-Key Principle , Wiley Chichester, 1994, pp. 247-306.
  32. ^ H. Kuhn, C. Kuhn: Diversified world: drive of life's origin ?! In: Angew. Chem. Int Ed. Engl. , Vol. 42, 2003, pp. 262-266.
  33. ^ H. Kuhn: Origin of life - Symmetry breaking in the universe: Emergence of homochirality. In: Current Opinion in Colloid & Interface Science , Volume 13, 2008, pp. 3-11.
  34. ^ H. Kuhn: Is the transition from chemistry to biology a mystery? In: Systems Chemistry , Volume 1, 2010, p. 3.
  35. ↑ J.-M. Lehn: Supramolecular Chemistry: Concepts and Perspectives. Wiley-VCH Weinheim, 1996.
  36. ^ M Elbing, R. Ochs, M. Koentopp, M. Fischer, C. von Hänisch, F. Weigand, F. Evers, HB Weber, M. Mayor: A single-molecule diode. In: PNAS , Volume 102, 2005, pp. 8815-8820.
  37. ^ M. Kindermann, I. Stahl, M. Reimold, WM Pankau, G. von Kiedrowski: Systems chemistry: kinetic and computational analysis of a nearly exponential organic replicator. In: Angew. Chem. Int. Ed. Engl. , Vol. 44, 2005, pp. 6750-6755.
  38. ^ H. Hess, GD Bachand, V. Vogel: Powering nanodevices with biomolecular motors. In: Chem. Eur. J. , Volume 10, 2004, pp. 2110-2116.
  39. ^ Werner Prize. In: scg.ch. September 30, 2020, accessed on March 29, 2020 .
  40. ^ The list of winners. In: chem.uzh.ch. April 1, 2019, accessed March 29, 2020 .
  41. ^ Braunschweigische Wissenschaftliche Gesellschaft - List of the award winners. In: bwg-nds.de. March 26, 2020, accessed March 29, 2020 .
  42. ^ Honorary doctorate at the Philipps University of Marburg. In: uni-marburg.de. Retrieved March 29, 2020 .
  43. ^ SCS Honorary Members. In: scg.ch. March 30, 2020, accessed on March 29, 2020 .
personal data
SURNAME Kuhn, Hans
BRIEF DESCRIPTION Swiss physical chemist
DATE OF BIRTH December 5, 1919
PLACE OF BIRTH Bern , Switzerland
DATE OF DEATH November 25, 2012
Place of death Troistorrents , Switzerland