Encapsulation of a CrIII Single‐Ion Magnet within an FeII Spin‐Crossover Supramolecular Host

Single functional molecules are regarded as future components of nanoscale spintronic devices. Supramolecular coordination chemistry provides unlimited resources to implement multiple functions to individual molecules. A novel coordination [Fe₂] helicate exhibiting spin‐crossover is demonstrated to be ideally suited to encapsulate a [Cr(ox)₃]^3? complex anion (ox=oxalate), unveiling for the first‐time single ion slow relaxation of the magnetization for this metal. A possibility of tuning the dynamics of this relaxation as well as the performance of the Cr^III center as qubit arises from the observation that metastable high spin Fe^II centers from the host can be generated by irradiation with green light at low temperature.     

Direct Time‐Domain Observation of Conformational Relaxation in Gas‐Phase Cold Collisions

Cooling molecules in the gas phase is important for precision spectroscopy, cold molecule physics, and physical chemistry. Measurements of conformational relaxation cross sections shed important light on potential energy surfaces and energy flow within a molecule. However, gas‐phase conformational cooling has not been previously observed directly. In this work, we directly observe conformational dynamics of 1,2‐propanediol in cold (6 K) collisions with atomic helium using microwave spectroscopy and buffer‐gas cooling. Precise knowledge and control of the collisional environment in the buffer‐gas allows us to measure the absolute collision cross‐section for conformational relaxation. Several conformers of 1,2‐propanediol are investigated and found to have relaxation cross‐sections with He ranging from σ=4.7(3.0)×10^?18 cm² to σ>5×10^?16 cm². Our method is applicable to a broad class of molecules and could be used to provide information about the potential energy surfaces of previously uninvestigated molecules.     

我国理论化学2008年研究进展简述

2008年中国大陆理论化学工作者在多个领域的研究都取得了新进展. 这些领域包括密度泛函理论的方法和应用、化学动力学和反应势能面的构造、光化学反应动力学、生物分子及生命现象、立体化学等. 本文简述了2008年中国大陆理论化学方面的研究工作进展, 重点突出了几个引起国际同行广泛关注的亮点.     

Functionalized Silicas for Metal‐Free and Metal‐Based Catalytic Applications: A Review in Perspective of Green Chemistry

Heterogeneous catalysis plays a key role in promoting green chemistry through many routes. The functionalizable reactive silanols highlight silica as a beguiling support for the preparation of heterogeneous catalysts. Metal active sites anchored on functionalized silica (FS) usually demonstrate the better dispersion and stability due to their firm chemical interaction with FSs. Having certain functional groups in structure, FSs can act as the useful catalysts for few organic reactions even without the need of metal active sites which are termed as the covetous reusable organocatalysts. Magnetic FSs have laid the platform where the effortless recovery of catalysts is realized just using an external magnet, resulting in the simplified reaction procedure. Using FSs of multiple functional groups, we can envisage the shortened reaction pathway and, reduced chemical uses and chemical wastes. Unstable bio‐molecules like enzymes have been stabilized when they get chemically anchored on FSs. The resultant solid bio‐catalysts exhibited very good reusability in many catalytic reactions. Getting provoked from the green chemistry aspects and benefits of FS‐based catalysts, we confer the recent literature and progress focusing on the significance of FSs in heterogeneous catalysis. This review covers the preparative methods, types and catalytic applications of FSs. A special emphasis is given to the metal‐free FS catalysts, multiple FS‐based catalysts and magnetic FSs. Through this review, we presume that the contribution of FSs to green chemistry can be well understood. The future perspective of FSs and the improvements still required for implementing FS‐based catalysts in practical applications have been narrated at the end of this review.     

Synthesis of Functional Poly(disubstituted acetylene)s through the Post‐Polymerization Modification Route

We report the recent progress in the preparation of functional poly(disubstituted acetylene)s (PDSAs) through post‐polymerization modification routes. The metathesis polymerization of disubstituted acetylene monomers activated by Mo/W–Sn complex catalysts, which do not tolerate highly polar functionalities, was assumed to be a key step in the polymer synthetic procedures. We and other groups have explored several approaches to prepare PDSAs with latent reactive functionalities, which are inactive to Mo/W–Sn complex catalysts but can be used as highly reactive sites for post‐polymerization modification. Click chemistry, Michael‐type addition reactions, the use of activated esters and other strategies are demonstrated by recently published examples. These works indicate that post‐polymerization modification is an efficient route to the synthesis of various functional PDSAs.     

Chemically Functionalized Two‐Dimensional Carbon Materials

Nanographenes (NGs), also known as graphene quantum dots, have recently been developed as nanoscale graphene fragments. These nanocarbon species can be excited with UV light and emit light from the UV‐to‐visible region. This photoemission has received great attraction across multiple scientific fields. NGs can be produced by cutting off carbon sources or fusing small organic molecules to grow graphitic structures. Furthermore, the organic synthesis of NGs has been intensely studied. Recently, the number of research papers on postsynthetic modification of NGs has gradually increased. Installed organic groups can tune the properties of NGs and provide new functionalities, opening the door for the development of sophisticated carbon‐based functional materials. This review sheds light on recent progress in the postsynthetic modification of NGs and provides a brief summary of their production methods.     

The Modeling of Grain Surface Chemistry

Astrochemistry has made great progress in recent years. Especially the grain surface chemistry played important roles in the explanation of the formation of the interstellar molecules. In this review, we will discuss the progress, including the different numerical methods to simulate the ice mantles in the astrochemical models. We will also introduce the laboratory astrochemical experimental results, and their contributions to the grain surface chemistry in the review.     

Porous Polyelectrolytes: The Interplay of Charge and Pores for New Functionalities

The past decade has witnessed rapid advances in porous polyelectrolytes and there is tremendous interest in their synthesis as well as their applications in environmental, energy, biomedicine, and catalysis technologies. Research on porous polyelectrolytes is motivated by the flexible choice of functional organic groups and processing technologies as well as the synergy of the charge and pores spanning length scales from individual polyelectrolyte backbones to their nano‐/micro‐superstructures. This Review surveys recent progress in porous polyelectrolytes including membranes, particles, scaffolds, and high surface area powders/resins as well as their derivatives. The focus is the interplay between surface chemistry, Columbic interaction, and pore confinement that defines new chemistry and physics in such materials for applications in energy conversion, molecular separation, water purification, sensing/actuation, catalysis, tissue engineering, and nanomedicine.     

Robust Atomistic Modeling of Materials,Organometallic, and Biochemical Systems

Modern chemistry seems to be unlimited in molecular size and elemental composition. Metal‐organic frameworks or biological macromolecules involve complex architectures and a large variety of elements. Yet, a general and broadly applicable theoretical method to describe the structures and interactions of molecules beyond the 1000‐atom size regime semi‐quantitatively is not self‐evident. For this purpose, a generic force field named GFN‐FF is presented, which is completely newly developed to enable fast structure optimizations and molecular‐dynamics simulations for basically any chemical structure consisting of elements up to radon. The freely available computer program requires only starting coordinates and elemental composition as input from which, fully automatically, all potential‐energy terms are constructed. GFN‐FF outperforms other force fields in terms of generality and accuracy, approaching the performance of much more elaborate quantum‐mechanical methods in many cases.     

Design of Bioinorganic Materials at the Interface of Coordination and Biosupramolecular Chemistry

Protein assemblies have recently become known as potential molecular scaffolds for applications in materials science and bio‐nanotechnology. Efforts to design protein assemblies for construction of protein‐based hybrid materials with metal ions, metal complexes, nanomaterials and proteins now represent a growing field with a common aim of providing novel functions and mimicking natural functions. However, the important roles of protein assemblies in coordination and biosupramolecular chemistry have not been systematically investigated and characterized. In this personal account, we focus on our recent progress in rational design of protein assemblies using bioinorganic chemistry for (1) exploration of unnatural reactions, (2) construction of functional protein architectures, and (3) in vivo applications.     

Real‐time quantum chemistry

Significant progress in the development of efficient and fast algorithms for quantum chemical calculations has been made in the past two decades. The main focus has always been the desire to be able to treat ever larger molecules or molecular assemblies—especially linear and sublinear scaling techniques are devoted to the accomplishment of this goal. However, as many chemical reactions are rather local, they usually involve only a limited number of atoms so that models of about 200 (or even less) atoms embedded in a suitable environment are sufficient to study their mechanisms. Thus, the system size does not need to be enlarged, but remains constant for reactions of this type that can be described by less than 200 atoms. The question then arises how fast one can obtain the quantum chemical results. This question is not directly answered by linear‐scaling techniques. In fact, ideas such as haptic quantum chemistry (HQC) or interactive quantum chemistry require an immediate provision of quantum chemical information which demands the calculation of data in “real time.” In this perspective, we aim at a definition of real‐time quantum chemistry, explore its realm and eventually discuss applications in the field of HQC. For the latter, we elaborate whether a direct approach is possible by virtue of real‐time quantum chemistry. © 2012 Wiley Periodicals, Inc.     

The power of thiol‐ene chemistry

As a tribute to Professor Charlie Hoyle, we take the opportunity to review the impact of thiol‐ene chemistry on polymer and materials science over the past 5 years. During this time, a renaissance in thiol‐ene chemistry has occurred with recent progress demonstrating its unique advantages when compared with traditional coupling and functionalization strategies. Additionally, the robust nature of thiol‐ene chemistry allows for the preparation of well‐defined materials with few structural limitations and synthetic requirements. To illustrate these features, the utility of thiol‐ene reactions for network formation, polymer functionalization, dendrimer synthesis, and the decoration of three‐dimensional objects is discussed. Also, the development of the closely related thiol‐yne chemistry is described. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 743–750, 2010     

A Collection of Fullerenes for Synthetic Access Toward Oriented Charge‐Transfer Cascades in Triple‐Channel Photosystems

The development of synthetic methods to build complex functional systems is a central and current challenge in organic chemistry. This goal is important because supramolecular architectures of highest sophistication account for function in nature, and synthetic organic chemistry, contrary to high standards with small molecules, fails to deliver functional systems of similar complexity. In this report, we introduce a collection of fullerenes that is compatible with the construction of multicomponent charge‐transfer cascades and can be placed in triple‐channel architectures next to stacks of oligothiophenes and naphthalenediimides. For the creation of this collection, modern fullerene chemistry—methanofullerenes and 1,4‐diarylfullerenes—is combined with classical Nierengarten–Diederich–Bingel approaches.     

The Effect of Cholesterol on Membrane Dynamics on Different Timescales in Lipid Bilayers from Fast Field‐Cycling NMR Relaxometry Studies of Unilamellar Vesicles

The general applicability of fast field‐cycling nuclear magnetic resonance relaxometry in the study of dynamics in lipid bilayers is demonstrated through analysis of binary unilamellar liposomes composed of 1,2‐dioleoyl‐sn‐glycero‐3‐posphocholine (DOPC) and cholesterol. We extend an evidence‐based method to simulating the NMR relaxation response, previously validated for single‐component membranes, to evaluate the effect of the sterol molecule on local ordering and dynamics over multiple timescales. The relaxometric results are found to be most consistent with the partitioning of the lipid molecules into affected and unaffected portions, rather than a single averaged phase. Our analysis suggests that up to 25 mol %, each cholesterol molecule orders three DOPC molecules, providing experimental backup to the findings of many molecular dynamics studies. A methodology is established for studying dynamics on multiple timescales in unilamellar membranes of more complex compositions.     

Metalated Container Molecules

The coordination chemistry of metalated container molecules is currently attracting much interest, because the properties of such compounds are often different from those of their constituent components. By adjusting the size and form of the binding cavity it is often possible to coordinate coligands in unusual coordination modes, to activate and transform small molecules, or to stabilize reactive intermediates. Such compounds also allow for an interplay of molecular recognition and transition‐metal catalysis, and for the construction of more effective enzyme mimics. Consequently, a number of research groups are involved in the development of new supporting ligands that create confined environments about active metal coordination sites. This research report briefly reviews recent progress in this field including the results of my own group. It is shown that N‐functionalized derivatives of Robson‐type macrocyclic hexaaza‐dithiophenolate ligands form bioctahedral transition metal complexes of the type [(L^R)M₂(μ‐L′)]⁺ (M = Mn, Fe, Co, Ni, Zn) with an overall calixarene‐like structure. These complexes are amongst the first prototypes for polynuclear complexes with well defined binding cavities. Since the active coordination site L′ is accessible for a wide range of exogenous coligands, the [(L^R)M₂(μ‐L′)] complexes exhibit a rich coordination chemistry. It is demonstrated that the presence of the binding cavity influences many properties of the binuclear [(L^R)M^II₂]²⁺ complex fragments, including color, molecular and electronic structure, hydrogen bonding interactions, redox potential, complex stability, and reactivity. The unusual properties of the complexes can be traced back to complementary host‐guest interactions and the distinct size and form of the binding pocket of the [(L^Me)M₂]²⁺ fragments.     

Artificial enzyme catalysis controlled and driven by light

Bio-inspired chemistry based on photoresponsive molecules is a rapidly developing new strategy to mimic the function of various biological systems. The interaction of electromagnetic radiation with molecular systems is ideally suited for the control and powering of dynamic processes at the speed of light. Besides typical applications in artificial photosynthesis, many other aspects, such as the catalytic turnover of substrates or the controlled release or uptake of small bioactive molecules, are readily verified with light-driven model systems. The potential of this novel approach in biomimetic chemistry is briefly explored in this concept article.     

Over one century after discovery: pyrylium salt chemistry emerging as a powerful approach for the construction of complex macrocycles and metallo-supramolecules

Over one century after its discovery, pyrylium salt chemistry has been extensively applied in preparing light emitters, photocatalysts, and sensitizers. In most of these studies, pyrylium salts acted as versatile precursors for the preparation of small molecules (such as furan, pyridines, phosphines, pyridinium salts, thiopyryliums and betaine dyes) and poly(pyridinium salt)s. In recent decades, pyrylium salt chemistry has emerged as a powerful approach for constructing complex macrocycles and metallo-supramolecules. In this perspective, we attempt to summarize the representative efforts of synthesizing and self-assembling large, complex architectures using pyrylium salt chemistry. We believe that this perspective not only highlights the recent achievements in pyrylium salt chemistry, but also inspires us to revisit this chemistry to design and construct macrocycles and metallo-supramolecules with increasing complexity and desired function.

This perspective summarizes the representative efforts of synthesizing and self-assembling large, complex architectures using pyrylium salt chemistry.     

On the Mechanism of Copper(I)‐Catalyzed Azide–Alkyne Cycloaddition

The copper(I)‐catalyzed azide–alkyne cycloaddition (CuAAC) reaction regiospecifically produces 1,4‐disubstituted‐1,2,3‐triazole molecules. This heterocycle formation chemistry has high tolerance to reaction conditions and substrate structures. Therefore, it has been practiced not only within, but also far beyond the area of heterocyclic chemistry. Herein, the mechanistic understanding of CuAAC is summarized, with a particular emphasis on the significance of copper/azide interactions. Our analysis concludes that the formation of the azide/copper(I) acetylide complex in the early stage of the reaction dictates the reaction rate. The subsequent triazole ring‐formation step is fast and consequently possibly kinetically invisible. Therefore, structures of substrates and copper catalysts, as well as other reaction variables that are conducive to the formation of the copper/alkyne/azide ternary complex predisposed for cycloaddition would result in highly efficient CuAAC reactions. Specifically, terminal alkynes with relatively low pK_a values and an inclination to engage in π‐backbonding with copper(I), azides with ancillary copper‐binding ligands (aka chelating azides), and copper catalysts that resist aggregation, balance redox activity with Lewis acidity, and allow for dinuclear cooperative catalysis are favored in CuAAC reactions. Brief discussions on the mechanistic aspects of internal alkyne‐involved CuAAC reactions are also included, based on the relatively limited data that are available at this point.