scholarly journals Mono- and Di-Quaternized 4,4′-Bipyridine Derivatives as Key Building Blocks for Medium- and Environment-Responsive Compounds and Materials

Molecules ◽  
2019 ◽  
Vol 25 (1) ◽  
pp. 1 ◽  
Author(s):  
Raffaello Papadakis
Keyword(s):  
Heterocyclic Compounds ◽  
Building Blocks ◽  
Review Article ◽  
Redox Activity ◽  
Research Trend ◽  
Structure Property ◽  
Property Relations ◽  
Key Features ◽  
Novel Applications

Mono- and di-quaternized 4,4′-bipyridine derivatives constitute a family of heterocyclic compounds, which in recent years have been employed in numerous applications. These applications correspond to various disciplines of research and technology. In their majority, two key features of these 4,4′-bipyridine-based derivatives are exploited: their redox activity and their electrochromic aptitude. Contemporary materials and compounds encompassing these skeletons as building blocks are often characterized as multifunctional, as their presence often gives rise to interesting phenomena, e.g., various types of chromism. This research trend is acknowledged, and, in this review article, recent examples of multifunctional chromic materials/compounds of this class are presented. Emphasis is placed on solvent-/medium- and environment-responsive 4,4′-bipyridine derivatives. Two important classes of 4,4′-bipyridine-based products with solvatochromic and/or environment-responsive character are reviewed: viologens (i.e., N,N′-disubstituted derivatives) and monoquats (i.e., monosubstituted 4,4′-bipyridine derivatives). The multifunctional nature of these derivatives is analyzed and structure–property relations are discussed in connection to the role of these derivatives in various novel applications.

scholarly journals Synthesis, crystal structure and structure–property relations of strontium orthocarbonate, Sr2CO4

2021 ◽  
Vol 77 (1) ◽  
pp. 131-137
Author(s):  
Dominique Laniel ◽  
Jannes Binck ◽  
Björn Winkler ◽  
Sebastian Vogel ◽  
Timofey Fedotenko ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Polycrystalline Sample ◽  
Building Blocks ◽  
Structure Property ◽  
X Ray Diffraction ◽  
Orthorhombic Crystal ◽  
Property Relations ◽  
Experimental Findings ◽  
Raman And Ir Spectra

Carbonates containing CO4 groups as building blocks have recently been discovered. A new orthocarbonate, Sr2CO4 is synthesized at 92 GPa and at a temperature of 2500 K. Its crystal structure was determined by in situ synchrotron single-crystal X-ray diffraction, selecting a grain from a polycrystalline sample. Strontium orthocarbonate crystallizes in the orthorhombic crystal system (space group Pnma) with CO4, SrO9 and SrO11 polyhedra as the main building blocks. It is isostructural to Ca2CO4. DFT calculations reproduce the experimental findings very well and have, therefore, been used to predict the equation of state, Raman and IR spectra, and to assist in the discussion of bonding in this compound.

Proposal for a Generic Materials Processing Course

MRS Bulletin ◽  
1990 ◽  
Vol 15 (8) ◽  
pp. 35-36 ◽  
Author(s):  
Merton C. Flemings ◽  
Klavs F. Jensen ◽  
Andreas Mortensen
Keyword(s):  
Materials Science ◽  
Building Blocks ◽  
Materials Processing ◽  
Structure Property ◽  
Science And Engineering ◽  
Specific Subject ◽  
Amorphous Phases ◽  
Property Relations ◽  
Materials Science And Engineering ◽  
The Subject

In the early 1950s when “materials science” was beginning to take shape in the minds of educators in materials departments, discussions were heated on the subject of how (and whether) intellectually rich courses could be developed with such broad coverage. It was argued by many that materials are too complex and vary too greatly from one another in their properties and in their applications to be treated in a single course. These individuals argued that if “materials” was to be taught, then it would have to be in courses or segments of courses broken down by materials classes-metals, ceramic, polymers, semiconductors.A full generation of faculty has passed through our ranks since those days, and the arguments regarding teaching of at least the beginning materials science subjects are now muted and perhaps moot. Few materials departments begin today with a materials-specific subject (e.g., metallurgy, ceramics) for either their own students or as a service subject for other engineering departments. Most begin with a subject in materials science or materials science and engineering that deals generically with all materials for at least a major portion of the subject. Examples are drawn from individual materials classes, and emphasis may shift to individual materials classes as the subject progresses.The key to development of these subjects, and the intellectual foundation on which they rest, is structure and structure-property relations. We can understand, and teach, how the building blocks of materials (atoms, molecules, grains, amorphous phases, etc.) fit together to build macroscopic structures.

Tailoring structure formation and mechanical properties of particle brush solids via homopolymer addition

2016 ◽  
Vol 186 ◽  
pp. 17-30 ◽  
Author(s):  
Michael Schmitt ◽  
Chin Ming Hui ◽  
Zachary Urbach ◽  
Jiajun Yan ◽  
Krzysztof Matyjaszewski ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Colloidal Crystal ◽  
Degree Of Polymerization ◽  
Structure Property ◽  
Precise Control ◽  
Property Relations ◽  
Linear Chains ◽  
Sensitive Dependence ◽  
Tethered Chains

Recent progress in the area of surface-initiated controlled radical polymerization (SI-CRP) has enabled the synthesis of polymer-grafted colloids with precise control over the architecture of grafted chains. The resulting ‘particle brush materials’ are of interest both from a fundamental as well as applied perspective because structural frustrations (associated with the tethering of chains to a curved surface) imply a sensitive dependence of the interactions between brush particles on the architecture of surface-tethered chains that offers new opportunities to design hybrid materials with novel functionalities. An important prerequisite for establishing structure–property relations in particle brush materials is to understand the role of homopolymer impurities that form, for example, by thermal self-initiation. This contribution presents a detailed discussion of the role of homopolymer additives on the structure and mechanical properties of particle brush materials. The results suggest that the dissolution of homopolymer fillers follows a two-step mechanism comprised of the initial segregation of homopolymer to the interstitial regions within the array and the subsequent swelling of the particle brush (depending on the respective degree of polymerization of brush and linear chains). Addition of even small amounts of homopolymer is found to significantly increase the fracture toughness of particle brush assembly structures. The increased resistance to failure could enable the synthesis of robust colloidal crystal type materials that can be processed into complex shapes using ‘classical’ polymer forming techniques such as molding or extrusion.

scholarly journals The Building Blocks of Social Trust: The Role of Customary Mechanisms and Property Relations for the Emergence of Social Trust in the Context of the Commons

2021 ◽  
pp. 004839312110084
Author(s):  
Marc Goetzmann
Keyword(s):  
Complex System ◽  
Social Trust ◽  
Building Blocks ◽  
Institutional Structure ◽  
External Effects ◽  
Property Relations ◽  
Management Of Resources ◽  
Mutual Monitoring ◽  
The Commons

This paper argues that social trust is the emergent product of a complex system of property relations, backed up by a sub-system of mutual monitoring. This happens in a context similar to Ostrom’s commons, where cooperation is necessary for the management of resources, in the absence of external authorities to enforce sanctions. I show that social trust emerges in this context because of an institutional structure that enables individuals to develop a generalized disposition to internalize the external effects of their actions. This is made possible by the “patrimonial” nature of this structure.

Exchange Spin Coupling from Gaussian Process Regression

2020 ◽  
Author(s):  
Marc Philipp Bahlke ◽  
Natnael Mogos ◽  
Jonny Proppe ◽  
Carmen Herrmann
Keyword(s):  
Machine Learning ◽  
Gaussian Process ◽  
Gaussian Process Regression ◽  
Molecular Magnets ◽  
Molecular Structures ◽  
Spin Coupling ◽  
Structure Property ◽  
Data Set ◽  
Uncertainty Estimates

Heisenberg exchange spin coupling between metal centers is essential for describing and understanding the electronic structure of many molecular catalysts, metalloenzymes, and molecular magnets for potential application in information technology. We explore the machine-learnability of exchange spin coupling, which has not been studied yet. We employ Gaussian process regression since it can potentially deal with small training sets (as likely associated with the rather complex molecular structures required for exploring spin coupling) and since it provides uncertainty estimates (“error bars”) along with predicted values. We compare a range of descriptors and kernels for 257 small dicopper complexes and find that a simple descriptor based on chemical intuition, consisting only of copper-bridge angles and copper-copper distances, clearly outperforms several more sophisticated descriptors when it comes to extrapolating towards larger experimentally relevant complexes. Exchange spin coupling is similarly easy to learn as the polarizability, while learning dipole moments is much harder. The strength of the sophisticated descriptors lies in their ability to linearize structure-property relationships, to the point that a simple linear ridge regression performs just as well as the kernel-based machine-learning model for our small dicopper data set. The superior extrapolation performance of the simple descriptor is unique to exchange spin coupling, reinforcing the crucial role of choosing a suitable descriptor, and highlighting the interesting question of the role of chemical intuition vs. systematic or automated selection of features for machine learning in chemistry and material science.

Modular, Stereocontrolled Cβ–H/Cα–C Activation of Alkyl Carboxylic Acids

2019 ◽  
Author(s):  
Ming Shang ◽  
Karla S. Feu ◽  
Julien C. Vantourout ◽  
Lisa M. Barton ◽  
Heather L. Osswald ◽  
...  
Keyword(s):  
Carboxylic Acid ◽  
Heterocyclic Compounds ◽  
Cross Coupling ◽  
Building Blocks ◽  
Enantioselective Synthesis ◽  
Carbon Centers ◽  
Drug Candidates ◽  
Rapid Diversification ◽  
Directing Group ◽  
Compound Series

<div> <div> <div> <p>The union of two powerful transformations, directed C–H activation and decarboxylative cross-coupling, for the enantioselective synthesis of vicinally functionalized alkyl, carbocyclic, and heterocyclic compounds is described. Starting from simple carboxylic acid building blocks, this modular sequence exploits the residual directing group to access more than 50 scaffolds that would be otherwise extremely difficult to prepare. The tactical use of these two transformations accomplishes a formal vicinal difunctionalization of carbon centers in a way that is modular and thus amenable to rapid diversity incorporation. A simplification of routes to known preclinical drug candidates is presented along with the rapid diversification of an antimalarial compound series. </p> </div> </div> </div>

Population Control (Review Article)

1961 ◽  
Vol 1 (3) ◽  
pp. 89-98
Author(s):  
Karol J. Krotki
Keyword(s):  
Population Control ◽  
Review Article ◽  
Small Enterprise ◽  
Opportunity Costs ◽  
Relative Importance ◽  
Factual Information ◽  
Undue Influence ◽  
Clear Cut ◽  
Economic Considerations

Discussions about the role of small enterprise in economic development tend to remain inconclusive partly because of the difficulty of assessing the relative importance of economic and non-economic objectives and partly because of the dearth of factual information on which to base an economic calculus. It is probably true, moreover, that, because of a lack of general agreement as to the economic case for or against small enterprise, non-economic considerations, including some merely romantic attitudes toward smallness and bigness, tend to exert an undue influence on public policies. There may, of course, be no clear-cut economic case. And noneconomic considerations should and will inevitably weigh significantly in policy decisions. If, however, some of the economic questions could be settled by more and better knowledge, these decisions could more accurately reflect the opportunity costs of pursuing non-economic objectives.

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