Current Organic Chemistry - Volume 18, Issue 15, 2014

It is our great pleasure as Guest Editors of the journal ‘Current Organic Chemistry’ to present you with a ‘hot topic issue’ on supramolecular chemistry, 'chemistry beyond the molecule'. Supramolecular chemistry examines the weaker interactions that hold groups of molecules together, no bonds that hold atoms together in a molecule [1]. The weaker interactions provide control, which allows the development of functional molecular and supramoleclar devices, defined as structurally organized and functionally integrated systems built from suitably designed molecular components performing a given action and endowed with the structural features required for assembly into an organized supramolecular architecture [1, 2]. The purpose of this special issue is to underscore the concepts and techniques of modern supramolecular chemistry, demonstrating how these paradigms evolve into nanometric size systems, nanotechnology, and materials science. The supramolecular self-assembly of polymer chains by specific, directional, and dynamic non-covalent interactions, including H-bond interaction, host-guest interaction, and amphiphilic association, has led to the development of novel polymeric supramolecular materials (PSMs). The first review of this issue is written by Drs. Liao, Zhang and their colleagues, who summarized the main strategies for the construction of PSMs and their applications in biomedical fields, such as drug delivery, tissues engineering, and biosensors. As they mentioned, it is still a challenge to finely control the process of selfassembly to produce PSMs with well-controlled properties. In the following article, Dr. Liang and his colleagues summarized recent advances in nanopore DNA sequencing, DNA Sequencing by Recognition, evolution of recognition molecules applied in Sequencing by Recognition, and discussed the opportunities and challenges in this rapidly growing field. Proposed interactions between recognition molecules and DNA bases in the nanopore should be investigated in detail by supramolecular chemist to help understand Sequencing by Recognition technique. In the third article of this issue, Dr. Fang and his colleagues highlighted the recent advances in the development of electronic sensors, in which the active conducting/semiconducting materials are incorporated with specific supramolecular receptors. Depending on the nature of the active conducting layer, these devices can be categorized into carbon materials-based sensors and organic semiconductor-based sensors. As they noted, recent groundbreaking developments of conductive Covalent Organic Frameworks (COFs)/ Metal Organic Frameworks (MOFs), supramolecular host-incorporated MOFs, and surface grown COFs have paved the way to the next generation electronic sensing materials. In the forth article of this issue, Dr. Wang and his colleagues summarized the recent research progress in the field of Organic Molecular Cages (OMCs) from synthesis, functionalization, and applications aspects. Since the gained specific surface areas are now comparable to those of MOFs and COFs, OMCs will definitely play a distinct role in the future of porous materials. In the fifth review, Dr. Zhang and his colleagues outlined the common design strategies and synthetic approaches used for the preparation of Ionic MOFs (I-MOFs), which are a unique type of MOFs that are composed of charged (positive or negative) frameworks containing mobile or loosely bound extra-framework counter ions. Enhanced gas adsorption and small molecules uptake due to the ionic feature of I-MOFs was discussed in detail. Recently reported potential applications for IMOFs in catalysis, optics, and photonics were also addressed. In the sixth article, Dr. Gassensmith and his colleagues discussed the chemistry within confined spaces. It was noted that the field is moving more toward solid-state and naturally porous systems in the short-term future; in particular, catalysis and reactivity within porous solids will likely dominate the landscape. Self-healing or self-repairing materials are a kind of ‘smart material’ that are able to repair their damage caused by mechanical force, and represent the forefront developments of 21st century in materials chemistry and engineering. In the seventh review, Dr. Liu and his colleagues described a few excellent examples of self-healing supramolecular polymers based on host–guest interactions, and discussed their advantages and versatility. In the last article of this issue, Drs. Yuan, and Liang reviewed the recent advances in the development and application of amphiphilic photomicroreactors with “soft” cavities in terms of supramolecular chemistry. In the limited space of the article, attention was focused primarily upon the microreactors bearing “soft” cavities including micelles, vesicles, polymers and dendrimers. Contrary to the “hard” cavities that usually show specific selectivity to the guests, “soft” cavities have a large applicability towards the substrates, since the size, shape and other properties of the “soft” cavities can be easily altered by such conditions as temperature, solvent, light or by the guest molecules themselves. We would like to sincerely thank all authors for their excellent work, and thank all reviewers for their scrutiny of manuscripts published in this special issue. It was a great opportunity for us to cooperate with researchers involved in this special issue. We hope that readers will enjoy this issue, obtain useful information, and be inspired with new ideas for future research on molecular recognition and supramolecular devices.

The supramolecular self-assembly of polymer chains by specific, directional, and dynamic non-covalent interactions, including hydrogen bonds, host-guest interactions, and amphiphilic associations, has led to the development of novel polymeric supramolecular materials (PSMs). PSMs in the form of micelles, fibers, and hydrogels, which exhibit unique chemical, physical, and biological properties, have been fabricated and shown to have great potential in biomedical applications. This review focuses on recent advances in the construction, as well as biomedical applications, of PSMs, such as in drug delivery matrices, tissue engineering scaffolds, and biosensors.

Nanopore based DNA Sequencing by Recognition technique relies on the sense of current between a pair of electrodes, which span nanopore and trap DNA nucleotides. The electrodes typically are tips of scanning tunneling microscope (STM) functionalized with recognition molecules that can distinguish individual DNA bases through hydrogen bonds. This manuscript aims to provide a summary of current research progress of nanopore DNA sequencing, DNA Sequencing by Recognition, evolution of recognition molecules applied in Sequencing by Recognition, and discusses the opportunities and challenges in this rapidly growing field.

Supramolecular host-guest chemistry allows sensitive and selective recognition of a certain substrate by using a rationally designed receptor. Such a molecular receptor can be incorporated into an electronic chemical sensor so that the anticipated host-guest binding event can be transduced directly into electric signals. In particular, chemiresistors and chemically sensitive field-effect transistors report the change of conductance/resistance of the active conducting materials upon the desired supramolecular binding event via varied mechanisms. This mini-review highlights the recent advances in the development of electronic sensors, in which the active conducting/ semiconducting materials are incorporated with specific supramolecular receptors. Depending on the nature of the active conducting layer, these devices can be categorized into carbon materials-based sensors and organic semiconductor-based sensors. At the end of this review, an outlook of the related field is provided and discussed.

The design and synthesis of molecular container compounds is playing an important role in host–guest chemistry. Porous organic molecular cages (OMCs) represent an exciting type of container-like compounds and have attracted intensive attention in the past few decades. These materials are constructed through covalent bonds and can be synthesized in reasonable yield by making use of dynamic covalent chemistry. Furthermore, they can pack to form crystalline materials with void spaces, thus showing potential applications in gas absorption and molecular separation. In this article, we highlight the state-of-the-art development in the synthesis, functionalization and application of OMCs.

Ionic metal-organic frameworks (I-MOFs) are porous crystalline materials with either positively or negatively charged frameworks. The nanosized and charged pores in these ionic architectures provide a strong interaction between the host and guest molecules including enhanced adsorption towards small gases and solvent molecules. Via ion exchange, I-MOFs can be easily modified and accommodate other charged guest molecules, making them an ideal platform for different applications as functional materials. The present review discusses the most recent advances in I-MOFs. The design strategies based on both charged organic linkers and inorganic clusters are summarized. Additionally, several applications of I-MOFs including gas and small molecule’s adsorption, chemical sensing, proton conductors, photonics, and catalysis are described.

The reactivity in the confined spaces of zeolites, metal-organic frameworks, cage compounds and macrocycles differ in many aspects from those conducted in bulk solution. Cases of altered regioselectivity, enhanced stability and accelerated substrate reactivity are presented within the context of non-covalent interactions between host and guest molecules, which define much of supramolecular chemistry, being unique and imparting highly useful properties that are of interest for their intellectual merit as well as their immense commercial value.

Self-healing or self-repairing materials are ‘smart materials’ that repair damage caused by mechanical force and are a key development of 21st century materials chemistry and engineering. In this review we describe a few excellent examples of self-healing supramolecular polymers based on host-guest interactions and discuss their advantages and versatility.

The recent advances in the development and application of amphiphilic photomicroreactors with “soft” cavities in terms of supramolecular chemistry are reviewed. In this article, we describe how these microreactors alter the photochemical behavior of guests inside their “soft” confined and restrict microenvironment. The main aim is to show the different types of amphiphilic microreactors, the photoreactions occurring within them and the great promise of these microreactors. Finally a comparison between the “soft” cavities and “hard” cavities (such as zeolite, cage molecules, etc.) as well as the current challenges and further directions of these microreactors are also discussed at the end of this review.

The carbon-carbon double bond offers a possibility to incorporate a cyclopropane ring into a molecule. The special electronic nature of the cyclopropane ring can significantly change the electronic and biological properties of the new derivatives. Herein we present natural compounds containing a fused cyclopropane ring and natural compounds condensed with a cyclopropane ring synthetically.

Detection of single nucleotide polymorphisms (SNPs) is critical for early stage diagnosis. However, available clinical methods for detecting SNPs require strict assay conditions or complicated enzyme reactions. DNA hybridization by Au nanoparticles is a new microscopic method for DNA detection, which offers many advantages over traditional ones. But currently, this method is limitedly used because of low yield of hybridization. Here we report novel strategies which use toehold-mediated strand displacement on DNA origami Chip by employing AuNPs, and we greatly improved the yield of hybridization to 80% from less than 10%. Based on the kinetic characteristic of toehold-mediated strand displacement reaction, DNA strands with unmatched sequences can be easily replaced by fully complementary ones, and the exchange rate depends on the length of the toehold region. Therefore, variation on ssDNA sequence can be differentiated by their different displacement time. With this approach we detect SNPs of age-related macular degeneration on DNA origami chip. This approach offers a new, simple and sensitive way to detect SNP.

This book provides exhaustive and timely information about the use of copper compounds as catalysts in asymmetric synthesis. The introductory chapter reflects the importance of bimetallic chiral copper-containing compounds, the so called cuprates, especially in two synthetically useful reactions: the conjugate addition and the allylic substitution, both in an asymmetric fashion. In Chapter 1, the use of mixed cuprates containing organometallic reagents derived from lithium, magnesium, zinc, boron, aluminium, silicon or tin, in combination with a chiral ligand in asymmetric synthesis, is considered. Next Chapter 3 is devoted to the asymmetric conjugate addition and allylic substitution starting from more extended multiple-bond systems, such as polyconjugated Michel acceptors or allyl derivatives. Asymmetric allylic alkylation is the subject of Chapter 4, in which different carbon-nucleophiles and functionalized substrates are studied, together with asymmetric processes such as desymmetrization of meso-allylic substrates or kinetic resolution processes, as well as direct enantioconvergent transformations. Chapter 5 shows the copper-catalyzed asymmetric ring opening of substituted epoxides with amines, or the same process using an organometallic reagent with epoxides, aziridines or heterobicyclic systems. The formation of carbon-boron or carbon-silicon bonds mainly when a new sterocenter is involved in the process is the topic included in Chapter 6. The following Chapter 7 studied the use of copper hydride in asymmetric reductions, including conjugate reductions, 1,2-additions and some heterogeneous catalytic processes. The asymmetric cyclopropanation and azirinidation of olefins is the subject of Chapter 8. In Chapter 9 the copper-catalyzed asymmetric alkylation, allylation, arylation and alkynylation of imines, as well as the use of copper as a Lewis acid catalyst in asymmetric reactions with imines is considered. The carbometallation of cyclopropenes and alkynes are treated in Chapter 10. Chiral copper Lewis acids is the topic considered in Chapter 11, which includes cycloadditions, Claisen rearrangements, ene reactions, nucleophilic addition to carbonyl compounds and imines, conjugate additions,