Looking Back and Looking Ahead in Electrochemical Reduction of CO2

Electrochemical reduction of carbon dioxide (CO₂) to valuable organic compounds is promising as to recycling of carbon source of CO₂ and technical compatibility with systems using renewable energy resources. In recent years, considerable efforts have been devoted to the research field of CO₂ conversion using electrocatalysis. This personal account particularly focuses on the recent progress that has been achieved by the Ertl Center and a number of groups in South Korea that becomes one of the larger CO₂ emitters. The research trends of catalyst development divided into different categories according to the primary products are presented first. Afterwards, several studies on theoretical calculations and electrolytic reactors are reviewed taking into account the fundamental understanding and feasibility of the CO₂ electroreduction. Finally, a perspective on the challenges and needs in achieving the advanced level of research and development is presented.     

Looking for clear solutions

The familiar ways of reaching consensus about measurements are leading analytical chemists into troubled waters.     

Looking at atomic orbitals through fourier and wavelet transforms

Solutions of Hartree–Fock equations expressed as Gaussian functions are studied in various spaces: position, momentum, and position–momentum spaces. The use of the wavelet transform allows one to visualize position and momentum characteristics of atomic orbitals on the same drawing. A complementary viewpoint is then obtained on top of usual position and momentum representations. Applications to Gaussian “atomic” orbitals modeled as one-dimensional functions are performed. © 1993 John Wiley & Sons, Inc.     

Looking for the Origin of Allosteric Cooperativity in Metallopolymers

The basic concept of allosteric cooperativity used in biology, chemistry and physics states that any change in the intermolecular host–guest interactions operating in multisite receptors can be assigned to intersite interactions. Using lanthanide metals as guests and linear multi‐tridentate linear oligomers of variable lengths and geometries as hosts, this work shows that the quantitative modeling of metal loadings requires the consideration of a novel phenomenon originating from solvation processes. It stepwise modulates the intrinsic affinity of each isolated site in multisite receptors, and this without resorting to allosteric cooperativity. An easy‐to‐handle additive model predicts a negative power law dependence of the intrinsic affinity on the length of the linear metallopolymer. Applied to lanthanidopolymers, the latter common analysis overestimates cooperativity factors by more than two orders of magnitude.     

Looking Back and Ahead: Gas-Phase Electron Diffraction at 75

At 75, gas-phase electron diffraction is still the method of choice for selected problems in molecular structure determination. It works best when being applied with other techniques in a concerted way.     

Looking for a synergic effect between NHCs and chiral P-ligands

The issue of the added value of NHCs in asymmetric catalysis with respect to trusted chiral P-ligands was addressed: considering a prototypical asymmetric allylic alkylation reaction as a model, the association of a priori inhibiting and achiral NHCs with modular P-ligand resulted in enhancement of er up to 508% and increased rates.     

Looking for Linearity: Integrating Graphing for First-Year Chemistry Students

Based on our observation that the general literature does not provide an organizing principle for the graphs that science students encounter, an approach called Looking for Linearity has been described. This approach is based on the hypothesis that when scientists look at their data and begin to represent it, they initially look for linearity. This is to say that scientists use Occams Razor; variables are used and transformed in such ways that when plotted against each other, the simplest representation—the straight line—is produced. A brief review of the topics typically covered in the first year of chemistry reveal a substantial number of relationships either expressed in the form of a straight line (gas laws, free energy, rate laws) or in terms of ratios that when graphed produce straight lines (density, specific heat capacity, stoichiometry). Looking for Linearity is an approach to graphing that serves four purposes for teaching first year chemistry students: 1) it weaves a common theme or thread through the entire year of General Chemistry, 2) it allows students to work like scientists, 3) it connects an important mathematical construct with chemical concepts, and 4) it provides a method to process data in other scientific fields like physics. The linearity heuristic is represented in what is called a Graphing Decision Tree. This tree shows, in simplified terms, how linearity can be used to organize different types of graphs found in the first year of chemistry. The Decision Tree is hierarchically structured from simple to increasing graphing complexity. Straight lines were listed as being the simplest to interpret, followed by exponential curves and then non-exponential curves; exponential curves were second because they could be converted to straight lines by using logarithms. Each pathway ends with examples of some of the different types of graphs our students will encounter in the first year of chemistry.     

Looking inside the entanglement “tube” using molecular dynamics simulations

For 30 years, the dynamics of entangled polymers have been explained using the phenomenological “tube” model, where the “tube” represents the confining effects of surrounding chains, but the tube properties, such as its length and diameter, could only be inferred indirectly by fitting the tube model to rheological data. Now, however, molecular simulations are allowing these properties to be directly computed. The computational advances in molecular dynamics and related methods that have made this possible are here reviewed. In addition, it is discussed how new findings, such as an apparent time dependence of the tube diameter and direct observation of “hopping” of branch points along the tube, are helping to refine the tube model. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 3240–3248, 2007     

Looking at self-consistent-charge density functional tight binding from a semiempirical perspective

The self-consistent-charge density functional tight binding (SCC-DFTB) method is compared with other semiempirical methods (MNDO, AM1, PM3, OM1, OM2, OM3). Despite the differences in the underlying philosophy and derivation, these methods share many common features. Systematic evaluations of their performance are reported for standard test sets that are in common use. The overall accuracy of SCC-DFTB and the other methods is in the same range, with the overall tendency AM1相似文献   

Analytical atomic spectrometry and imaging: Looking backward from 2020 to 1975

Some general aspects of the evolution of atomic spectrometry for chemical analysis over the period 1975 to now are described. Performance parameters such as detection limits and spatial analytical potential (lateral and depth resolution) are compared with the evolution of integrated circuit technology as described in Moore's Law. A few general trends of future development for the coming decade are postulated. Attention will be focused on analysis and imaging with beam techniques, especially secondary ion mass spectrometry and X-ray techniques on the basis of excitation with synchrotron radiation.     

Looking for the origin of the switch between coordination-captured helicates and catenates

Self-assembly of the linear segmental ligand L5, consisting of a tridentate binding unit flanked with two bidentate binding units, with a mixture of Fe(II)/Ag(I) yields the trinuclear coordination-captured [2]catenate [AgFeAg(L5)(2)](4+) instead of the planned isomeric double-stranded helicate. Replacing the octahedral (Fe(II)) and tetrahedral (Ag(I)) cations with Zn(II), which is compatible with both geometries, gives intricate mixtures of homometallic complexes upon reaction with the twin ligand L6, from which the macrocyclic dinuclear complex [Zn(2)(L6)](4+) can be isolated. Application of the thermodynamic site binding model attributes the origin of the ligand preference for producing single-stranded macrocycles, the precursors of the trinuclear catenate, to the abnormally low value of the effective molarity controlling the intramolecular connection leading to the usual double-stranded helical isomer.