From Molecular Diversity to Template-Directed Self-Assembly – New Trends in Metallo-Supramolecular Chemistry

Molecular diversity can easily be generated in metallo-supramolecular systems by simple mixing of oligodentate ligands and appropriate metal ions. In this reaction either a defined coordination compound is formed in a selective self-assembly process or a mixture is obtained. Depending on the system such a mixture can possess a statistical distribution of components or the formation of some species is thermodynamically favored leading to only a few out of several possible compounds (or in the extreme to only one). Simple well-defined mixtures containing only a few components or pure supramolecular aggregates can be generated from sequential or directional ligands, from mixtures of ligands and/or metals, and by introducing templates which support the formation of defined metallo-supramolecular aggregates. In the latter case it is possible first to generate a mixture of components which are in dynamic equilibrium (dynamic combinatorial library). In a second step, a template can be added, which in a dynamic process transforms such a library into one well-defined species. Thus, the initial generation of molecular diversity allows in a subsequent selection step in an evolutionary process the formation of the most favored receptor/substrate adduct (``dynamic combinatorial chemistry').     

New Routes to Hydrogen Peroxide: Alternatives for Established Processes?

The reduction of dioxygen to hydrogen peroxide occurs in the presence of copper and palladium catalysts. The first mentioned biomimetic process uses primary alcohols as the reductant, while in the second, in which the key feature is the use of chelating nitrogen ligands, CO fulfills this function (see scheme). Whether these two new methods will become commercial scale and compete with the established anthraquinone method for production remains unanswered.     

Protein-Templated Fragment Ligations—From Molecular Recognition to Drug Discovery

Protein-templated fragment ligation is a novel concept to support drug discovery and can help to improve the efficacy of protein ligands. Protein-templated fragment ligations are chemical reactions between small molecules (“fragments”) utilizing a protein's surface as a reaction vessel to catalyze the formation of a protein ligand with increased binding affinity. The approach exploits the molecular recognition of reactive small-molecule fragments by proteins both for ligand assembly and for the identification of bioactive fragment combinations. In this way, chemical synthesis and bioassay are integrated in one single step. This Review discusses the biophysical basis of reversible and irreversible fragment ligations and gives an overview of the available methods to detect protein-templated ligation products. The chemical scope and recent applications as well as future potential of the concept in drug discovery are reviewed.     

9,9′-Bicarbazole: New Molecular Skeleton for Organic Light-Emitting Diodes

Carbazole is a classic tricyclic aromatic compound that has been widely used in organic optoelectronics. Appropriate functionalization on its aromatic rings will significantly increase the possibilities for its application as an optoelectronic material. Position engineering of carbazole not only leads to its structural diversity, but also substantially enriches its functionality. Bicarbazoles have 15 isomers, most of which are well studied and have been applied in organic light-emitting diodes (OLEDs). However, one isomer, 9,9′-bicarbazole, is rarely investigated as an OLED material. Therefore, two 9,9′-bicarbazole derivatives, 3,3′-di(10H-phenoxazin-10-yl)-9,9′-bicarbazole and 3,3′-di(10H-phenothiazin-10-yl)-9,9′-bicarbazole, have been designed and prepared for use as host materials for green and red OLEDs. These two compounds demonstrated good device performances, and it is believed that the 9,9′-bicarbazole building block could be a novel platform for the design of efficient host materials for OLEDs.     

From Disymmetric Molecules to Chiral Polymers: A New Twist for Supramolecular Synthesis?

A new branch of crystal engineering appears to have borne fruit: A noncovalently bonded network consisting of the complex illustrated as a stick model on the right is converted directly into a coordination polymer with a similar molecular architecture. The implications of the new work extend beyond the boundaries of coordination chemistry since the same strategy should work equally well in organic and organometallic systems.     

Chemistry:The Molecular Nature of Matter and Change 评述

从内容编排、栏目设置、插图与版式设计等几个角度对美国普通化学教材Chemistry:The Molecular Nature ofMatter and Change的编写特色进行评析,以期对我国同类教材的编写提供参考。     

Ionic Liquids: New Perspectives for Inorganic Synthesis?

Ionic liquids are credited with a number of unusual properties. These include a low vapor pressure, a wide liquid‐phase range, weakly coordinating properties, and a high thermal/chemical stability. These properties are certainly of great interest for inorganic synthesis and the creation of novel inorganic compounds. On the other hand, the synthesis repertoire for preparing inorganic compounds has always been broad, ranging from syntheses in solutions and melts to solid‐state reactions, and from crystal growth in the gas phase to high‐pressure syntheses. What new aspects can ionic liquids then add to the synthesis of inorganic compounds? This Minireview uses some early examples to show that the use of ionic liquids indeed provides access to unusual inorganic compounds.     

Analytical Chemistry — a time for change?

A report of the RSC-Analytical Division Automated Methods Group Symposium, held in Ferndown, Dorset, U.K., 28–30 October 1987.     

Anisotropy of Thermal-expansion for β-Octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine: Quantum Chemistry Calculation and Molecular Dynamics Simulation

Molecular dynamics simulations on octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) at 303-383 K and atmospheric pressure are carried out under NPT ensemble and COMPASS force field, the equilibrium structures at elevated temperatures were obtained and showed that the stacking style of molecules don't change. The coefficient of thermal expansion (CTE) values were calculated by linear fitting method. The results show that the CTE values are close to the experimental results and show anisotropy. The total energies of HMX cells with separately increasing expansion rates (100%-105%) along each crystallographic axis was calculated by periodic density functional theory method, the results of the energy change rates are anisotropic, and the correlation equations of energy change-CTE values are established. Thus the hypostasis of the anisotropy of HMX crystal's thermal expansion, the determinate molecular packing style, is elucidated.     

Metal Organic Framework Glasses: A New Platform for Electrocatalysis?

Metal organic framework (MOF) glasses are a coordination network of metal nodes and organic ligands as an undercooled frozen-in liquid, and have therefore broadened the potential of MOF materials in the fundamental research and application scenarios. On the road to deploying MOF glasses as electrocatalysts, it remains several basic scientific hurdles although MOF glasses not only inherit the structural merits of MOFs but also endow with active catalytic features including concentrated defects, metal centers and disorder structure etc. The research on the ionic conductivity, catalytic stability and reactivity of MOF glasses has yielded scientific insights towards its electrocatalytic applications. Here, we first comb the history, definition and basic properties of MOF glasses. Then, we identify the main synthetic methods and characterization techniques. Finally, we advance the potentials and challenges of MOF glasses as electrocatalysts in furthering the understanding of these themes.