bluuebunny/crossref_metadata_2025_split huggingface dataset:
Five Decades Ago: From the “Transuranics” to Nuclear Fission
Authors: Herrmann Günter 
Published: December 2003

AbstractThe discovery of nuclear fission is one of the most outstanding episodes in the history of chemistry: It starts in the spring of 1934 when Enrico Fermi and his group irradiate uranium with neutrons and seem to succeed in going beyond uranium, the then heaviest known element, reaching the first transuranic element; it continues with Otto Hahn, Lise Meitner and Fritz Strassmann who believe to have found additional transuranic elements; with Irène Curie and Paul Savitch who observe an activity which somehow does not fit into that scheme; again with Otto Hahn and Fritz Strassmann who first identify this activity as radium but then on the 17th of December 1938 after rigorous chemical tests realize that the activity is instead barium, thus discovering the fission of the uranium atom into two lighter nuclei; and with Lise Meitner and Otto Robert Frisch who explain nuclear fission on the basis of an already known nuclear model; Otto Robert Frisch finally performs a physical experiment on the 13th of January 1939 which corroborates the fission of uranium. This discovery of nuclear fission is not only an event of historic dimensions, it is also an excellent example of how science evolves, not by successive logical steps but rather through strange detours.
Gas Chromatographic Separation of Enantiomers on Cyclodextrin Derivatives
Authors: Schurig Volker , Nowotny Hans‐Peter 
Published: December 2003

AbstractIn investigations concerned with the phenomenon of molecular chirality, the use of gas chromatography for the enantiomeric analysis of stable, volatile compounds is a technique of steadily growing importance. [1] In the last three years an important breakthrough in gas‐chro‐matographic separation of enantiomers has been achieved by using alkylated cyclodextrins (α, β, and γ) as chiral stationary phases in high‐resolution capillary columns. In academic and commercial practice two different and complementary strategies have been adopted up to now. In the first, alkylated cyclodextrins are diluted with polysiloxanes and coated on glass or fused silica capillary columns. In the second, lipophilic per‐n‐pentylcyclodextrins and hydrophilic di‐n‐pentyl‐ and hydroxyalkylpermethylcyclodextrins are coated directly in the form of liquid phases onto suitably pretreated glass or fused silica surfaces. These techniques permit enantiomer separations not only for polar diols and alcohols, derivatized hydroxycarboxylic acids, amino acids, sugars, and alkyl halides, but also for nonpolar alkenes, cyclic saturated hydrocarbons, and metal π complexes. An important aspect for practical applications is that in many cases the enantiomers can be separated without previous derivatization. Whereas the resolution of racemates of unfunctionalized hydrocarbons is attributed to an enantioselective host–guest inclusion complex, some observations indicate that for polar guest molecules additional enantioselective interactions are also involved. The new chiral stationary phases can be used over a wide range of temperatures (25 to 250°C). The technique described is likely to become widely adopted as a simple, accurate and highly sensitive method for the enantiomeric analysis of chiral compounds that can be vaporized without decomposition. It will also stimulate future research aimed at finding universal cyclodextrin phases and elucidating the mechanisms of enantioselectivity.
The Directed Synthesis of Biaryl Compounds: Modern Concepts and Strategies
Authors: Bringmann Gerhard , Walter Rainer , Weirich Ralf 
Published: December 2003

AbstractThe preparation and utilization of specific biaryl systems, particularly those which suffer hindered rotation, is a demanding goal not only in the synthesis of natural products and Pharmaceuticals, but also for example in the discovery of new reagents for asymmetric synthesis. This article will attempt to provide a topical review of modern, efficient processes for the specific preparation of biaryls. This appears to be of particular urgency, since, under the pressure of continually increasing demand, a wealth of new or modified synthetic approaches to the ever more important biaryl systems has been realized in recent years. The high standard which has been reached in this field is impressively demonstrated by regio‐ and stereoselective syntheses of important biaryl natural products such as steganone, ancistrocladine, ancistrocladisine, and dioncophylline A. Besides the utilization of asymmetric induction in the actual coupling step, the thermodynamically or kinetically controlled torsion of biaryl axes belongs to the most important concepts discussed.
Computer Simulation of Molecular Dynamics: Methodology, Applications, and Perspectives in Chemistry
Authors: van Gunsteren Wilfred F. , Berendsen Herman J. C. 
Published: December 2003

AbstractDuring recent decades it has become feasible to simulate the dynamics of molecular systems on a computer. The method of molecular dynamics (MD) solves Newton's equations of motion for a molecular system, which results in trajectories for all atoms in the system. From these atomic trajectories a variety of properties can be calculated. The aim of computer simulations of molecular systems is to compute macroscopic behavior from microscopic interactions. The main contributions a microscopic consideration can offer are (1) the understanding and (2) interpretation of experimental results, (3) semiquantitative estimates of experimental results, and (4) the capability to interpolate or extrapolate experimental data into regions that are only difficultly accessible in the laboratory. One of the two basic problems in the field of molecular modeling and simulation is how to efficiently search the vast configuration space which is spanned by all possible molecular conformations for the global low (free) energy regions which will be populated by a molecular system in thermal equilibrium. The other basic problem is the derivation of a sufficiently accurate interaction energy function or force field for the molecular system of interest. An important part of the art of computer simulation is to choose the unavoidable assumptions, approximations and simplifications of the molecular model and computational procedure such that their contributions to the overall inaccuracy are of comparable size, without affecting significantly the property of interest. Methodology and some practical applications of computer simulation in the field of (bio)chemistry will be reviewed.
Complexes with Substituent‐free Acyclic and Cyclic Phosphorus, Arsenic, Antimony, and Bismuth Ligands
Authors: Scherer Otto J. 
Published: December 2003

AbstractUntil recently, phosphorus, arsenic, antimony and bismuth ligands were nearly always understood to be molecules such as R3E, R2E(CH2)nER2, and RC[(CH2)nER2]3(E = P, As, Sb, Bi) in which the lone pair of the atom E functions as a 2e donor. Current research interests, however, increasingly involve substituent‐free En ligands (n = 1–6), the various types of which are mainly accessible via EX3 (X = F,Cl,Br,Ph), E (SiMe3)3, (RAs)n, P4S3, As4S4, gray arsenic, and especially P4 and As4; these ligands can be stabilized in the coordination spheres of certain transition metal fragments. P1, As1 and Sb1 units with multiple M‐E bonds are found in bi‐ and trinuclear complexes; E1 units can also be encapsulated (partially or completely) in cavities of a variety of metal cluster frameworks. Metallatetrahedranes with up to three E atoms are especially common. Besides E1 units, the greatest variety of coordination modes is exhibited by E4 ligands, which are found as intact tetrahedra and also as parts of chains, polycycles, cubes and a trigonal prism. The phosphorus and arsenic species cyclo‐En, isoelectronic to the carbocyclic (CH)n species, are suitable ligands for forming sandwich complexes (n =3, 4, 5) and triple‐decker sandwich complexes (n = 3, 5, 6). In addition to the wide variety of chemical reactions, remarkable parallels are found in organic chemistry as well as in solid‐state chemistry for many of these substance classes. Some of the molecules have received lively interest from theoretical chemists.
An N‐Phosphino C‐ThiophosphinoyI Nitrilimine as a Formal 1,4 Dipole: Synthesis of 1,2,3λ5‐Diaza‐ and 1,2,4,3λ5‐Triazaphosphinines
Authors: Granier Michel , Baceiredo Antoine , Nieger Martin , Bertrand Guy 
Published: December 2003

AbstractNo Absract.
Novel Bonding Mode for a Cyanometalate Ligand: Synthesis and Crystal Structure of the Mn4Pd4 Cluster [(OC)Pd(μ‐NC)Mn(η‐C5H4Me)(CO)2]4 Containing an Orthogonal Arrangement of Helical Units
Authors: Braunstein Pierre , Oswald Benoît , Tiripicchio Antonio , Camellini Marisa Tiripicchio 
Published: December 2003

AbstractNo Absract.
Facile Hydrogenation of the Central Cyclohexatriene of Tris(benzocyclobutadieno)benzene: Synthesis, Structure, and Thermal and Photochemical Isomerization of all‐cis‐Tris(benzocyclobuta)cyclohexane
Authors: Mohler Debra L. , Vollhardt K. Peter C. , Wolff Stefan 
Published: December 2003

AbstractNo Absract.
Fluorescence “Off–On” Signalling upon Linear Recognition and Binding of α,ω‐Alkanediyldiammonium Ions by 9,10‐Bis{(1‐aza‐4,7,10,13,16‐pentaoxacyclooctadecyl)methyl}anthracene
Authors: de Silva A. Prasanna , Sandanayake K. R. A. Samankumara 
Published: December 2003

AbstractNo Absract.
Chemistry for the Future—State of the Art and Perspectives
Authors: Quadbeck‐Seeger Hans‐Jürgen 
Published: December 2003

AbstractA particularly close relationship exists between chemistry, the science of the transformation of matter, and developments in human living conditions. Though little more than 150 years old, chemical technology has had a greater influence on our civilization than any other technological discipline. Its roots lie not in the crafts, but in scientific research. Relationships derived from the laws of nature were taken as a basis for the systematic solution of practical problems. It is to this strategy that chemistry owes its success. New opportunities arise from new discoveries. These result from basic research at universities, research institutes, and industrial laboratories. Applied research in turn transforms the discoveries into innovative solutions to problems on an industrial scale. The objectives of applied research are oriented toward the marketplace and to the needs of mankind. Our knowledge of scientific interrelationships has been growing with unabated vigor for decades, but so too has our insight into the enormous complexity of the material world. Many of the problems that civilization faces result from the fact that our knowledge is still inadequate. Intensive research and development offer the only hope for progress. Scientists must of course act responsibly with the knowledge they acquire, and they must provide the information necessary to establish public confidence in their methods and products. This is the prerequisite for broad acceptance of technological progress, and given the extent of the world's population no alternative to progress exists. The shape of that progress is also subject to influences outside the realm of science, however, including social norms and political activities. A country that is not rich in raw materials, like the Federal Republic of Germany, must pay particular attention to these factors as well if it is to maintain its innovative strength.
The Integrating Effect of the Research Policy of the European Communities
Authors: Narjes Karl‐Heinz 
Published: December 2003

AbstractThe research and development policy of the European Community (EC) was raised to a more solid legal basis by means of an extension of the treaties—the Single European Act—30 years after the enactment of the treaties of Rome. Today, the EC has succeeded in creating an independent, successful continent‐wide research und development community despite rather limited budgetary means. The reasearch activities of the EC were originally restricted to EURATOM, which takes care of problems concerning civil nuclear research. EURATOM brought many experiences in the course of time, and also yielded many successes. We have learned above all how community research and national research are to be coordinated in the most efficient way. After the energy crisis of the seventies, and after many national R & D failures in various fields, high priority was given to the improvement and safeguarding of the technological competitivity of the community and the effective strengthening of its innovation potential. It was more and more generally accepted that all R & D resources had to be concentrated throughout the community in order to enable it to compete successfully, especially with the U. S. and Japan. In order to fulfill this objective a research policy with a strong integrating effect was requested in addition to the national R & D research policies. Cohesion and know‐how transfer inside the EC belong therefore to the central issues of the R & D policy of the community, as do special efforts to include small and medium‐sized institutes and enterprises (SMEs). Framework programs were introduced in the eighties in order to ensure a medium‐term disposability of the budgetary means for R & D and to secure a certain continuity. The third framework program has been agreed upon, and it provides research funding until 1994. In 1987 approximately 1 Bill. Ecu/year were spent for R & D. Today, 1, 5 Bill. Ecu/year are available, and this amount will further grow to provide approximately 2 Bill. Ecu/year in 1992/93. Issues like the difference between basic and applied research under inclusion of industry‐political viewpoints are also included in this report. Furthermore, cooperation with and delimitation to other countries or communities such as the U. S. and Japan or the EFTA and the Comecon member states will be discussed. Finally, perspectives for R & D policies of the European Community in the nineties will be presented.
Elementary Steps in Heterogeneous Catalysis
Authors: Ertl Gerhard 
Published: December 2003

AbstractDespite the great importance of heterogeneous catalysis, research in this field has long been characterized by its empiricism. Now, however, thanks to the rapid development of methods in surface physics, the elementary steps can be identified at the atomic level and the underlying principles understood. Defined single crystal surfaces are employed as models, based on the analysis of the surfaces of ‘real’ catalysts. Direct images, with atomic resolution, can be obtained using scanning tunneling microscopy, while electron spectroscopic methods yield detailed information on the bonding state of adsorbed species and the influence of catalyst additives (promotors) upon them. The successful application of this approach is illustrated with reference to the elucidation of the mechanism of ammonia synthesis. The catalyst surface is usually transformed under reaction conditions, and, as the processes involved are far‐removed from equilibrium, such transformations can lead to intrinsic spatial and temporal self‐organization phenomena. In this case, the reaction rate may not remain constant under otherwise invariant conditions but will change periodically or exhibit chaotic behavior, with the formation of spatial patterns on the catalyst surface.
Mathematical Modeling of Chemical Reactors—Development and Implementation of Novel Technologies
Authors: Matros Yuri Shaevich 
Published: December 2003

AbstractMathematical modeling is an important tool for rapid and reliable reactor development and design. The models are built up from basic studies of the reaction mechanism and kinetics, the transfer processes, and the interactions within the system. A detailed understanding of the elementary processes enables the construction of powerful and complex models for dynamic and steady‐state simulation. With the aid of experimentally determined parameter values one can develop new processes or improve existing ones. Excellent results obtained in experimental work under idealized laboratory conditions can seldom be fully realized in practice. This is due to factors such as transfer resistances, local gradients, fluctuating conditions, and constructional and other limitations which lead to unsatisfactory parameter values and higher costs to compensate for these shortcomings. Some recommendations are made for circumventing these deficiencies.
Perspectives in Supramolecular Chemistry—From Molecular Recognition towards Molecular Information Processing and Self‐Organization
Authors: Lehn Jean‐Marie 
Published: December 2003

AbstractThe selective binding of a substrate by a molecular receptor to form a supramolecular species involves molecular recognition which rests on the molecular information stored in the interacting species. The functions of supermolecules cover recognition, as well as catalysis and transport. In combination with polymolecular organization, they open ways towards molecular and supramolecular devices for information processing and signal generation. The development of such devices requires the design of molecular components performing a given function (e.g., photoactive, electroactive, ionoactive, thermoactive, or chemoactive) and suitable for assembly into an organized array. Light‐conversion devices and charge‐separation centers have been realized with photoactive cryptates formed by receptors containing photosensitive groups. Eleclroactive and ionoactive devices are required for carrying information via electronic and ionic signals. Redox‐active polyolefinic chains, like the “caroviologens”, represent molecular wires for electron transfer through membranes. Push‐pull polyolefins possess marked nonlinear optical properties. Tubular mesophases, formed by organized stacking of suitable macro‐cyclic components, as well as “chundle”‐type structures, based on bundles of chains grafted onto a macrocyclic support, represent approaches to ion channels. Lipophilic macrocyclic units form Langmuir‐Blodgett films that may display molecular recognition at the air‐water interface. Supramolecular chemistry has relied on more or less preorganized molecular receptors for effecting molecular recognition, catalysis, and transport processes. A step beyond preorganization consists in the design of systems undergoing self‐organization, that is, systems capable of spontaneously generating a well‐defined supramolecular architecture by self‐assembling from their components under a given set of conditions. Several approaches to self‐assembling systems have been pursued: the formation of helical metal complexes, the double‐stranded helicates, which result from the spontaneous organization of two linear polybipyridine ligands into a double helix by binding of specific metal ions; the generation of mesophases and liquid crystalline polymers of supramolecular nature from complementary components, amounting to macroscopic expression of molecular recognition; the molecular‐recognition‐directed formation of ordered solid‐state structures. Endowing photo‐, electro‐, and ionoactive components with recognition elements opens perspectives towards the design of programmed molecular and supramolecular systems capable of self‐assembly into organized and functional supramolecular devices. Such systems may be able to perform highly selective operations of recognition, reaction, transfer, and structure generation for signal and information processing at the molecular and supramolecular levels.
Towards the Chemical Synthesis of Proteins
Authors: Bayer Ernst 
Published: December 2003

AbstractThe chemical total synthesis of proteins using solid supports has made great progress. It is therefore becoming a reality whatE. Fischeralready predicted in 1902: “I foresee the time when physiological chemistry… is able to prepare synthetic enzymes.” The synthesis of peptides of up to 20 amino acids by the well‐established solid‐phase procedure on polymeric supports (SPPS) has made great progress through the development of newer supports. At the same time, methods have emerged which facilitate the separation and characterization of peptides, thus allowing optimization of the synthesis of pure materials. The new supports which enable one to synthesize peptides by a rapid continuous flow procedure are characterized by hydrophilicity, beads of approximately equal size, similar swelling properties in the solvents used for peptide synthesis, and stability at high pressure. With graft copolymers of weakly cross‐linked polystyrene and linear polyethylene glycol (PEG), the synthetic cycle for coupling of one amino acid can routinely be reduced to 10–20 min with a concomitant higher yield. With beads of monodispersed graft copolymer of 10 μm diameter, a synthetic cycle can, in principle, be shortened to 1–5 min. By utilizing this high‐speed solid‐phase procedure, larger peptides up to the size of proteins could also be prepared in a few hours. With newer mass spectroscopic methods such as ion‐spray mass spectrometry, peptides of up to a molecular mass of 100 kDa can be characterized, and with the advent of capillary electrophoresis, another very efficient separation tool, besides HPLC, is at our disposal.
The Bioinorganic Chemistry of Vanadium
Authors: Rehder Dieter 
Published: December 2003

AbstractVanadium is a trace element that plays an important, perhaps essential and general role in the regulation of enzymatic phosphorylations. Several forms of life, including the fly agaric toadstool (Amanita muscaria) and certain sea squirts (ascidians), are able to concentrate vanadium. In other organisms vanadium is part of the active site of some enzymes. Well‐studied examples are the nitrogen‐fixing bacterium Azotobacter and various seaweeds that use vanadate‐dependent peroxidases to synthesize halogenated organic compounds. Despite its importance as a “biometal” both in primitive, prokaryotic organisms (Azotobacter) and in the highly organized ascidians, which represent an early stage in the evolution of vertebrates, the bioinorganic chemistry of vanadium is still in its infancy. Just as young, but undergoing explosive development, is the chemistry of model compounds for vanadium‐containing biomolecules, a domain of the bioinorganic coordination chemist, who almost daily discovers compounds with new and surprising structural features. This article reviews this fascinating area of bioinorganic chemistry.