Crystal Engineering of Dual Channel p/n Organic Semiconductors by Complementary Hydrogen Bonding

The supramolecular arrangement of organic semiconductors in the solid state is as critical for their device properties as the molecular structure, but is much more difficult to control. To enable supramolecular design of semiconducting materials, we introduced dipyrrolopyridine as a new donor semiconductor capable of complementary hydogen bonding with naphthalenediimide acceptors. Through a combination of solution, crystallographic, and device studies, we show that the self‐assembly driven by H bonding a) modulates the charge‐transfer interactions between the donor and acceptor, b) allows for precise control over the solid‐state packing, and c) leads to a combination of the charge‐transport properties of the individual components. The predictive power of this approach was demonstrated in the synthesis of three new coassembled materials which show both hole and electron transport in single‐crystal field‐effect transistors. These studies provide a foundation for advanced solid‐state engineering in organic electronics, capitalizing on the complementary H bonding.     

Supramolecular Clippers for Controlling Photophysical Processes through Preorganized Chromophores

A novel supramolecular clipping design for influencing the photophysical properties of functional molecular assemblies, by the preorganization (clipping) of chromophores, is described. Several chromophores end functionalized with molecular recognition units were designed. These molecular recognition units serve as handles to appropriately position these systems upon noncovalent interactions with multivalent guest molecules (supramolecular clippers). Towards this goal, we have synthesized 1,5‐dialkoxynaphthalene (DAN) and naphthalenediimide (NDI) functionalized with dipicolylethylenediamine (DPA) motifs. These molecules could preorganize upon noncovalent clipping with adenosine di‐ or triphosphates, which resulted in preassociated excimers and mixed (cofacial) charge‐transfer (CT) assemblies. Chiral guest binding could also induce supramolecular chirality, not only into the individual chromophoric assembly but also into the heteromeric CT organization, as seen from the strong circular dichroism (CD) signal of the CT transition. The unique ability of this design to influence the intermolecular interactions by changing the binding strength of the clippers furthermore makes it very attractive for controlling the bimolecular photophysical processes.     

Diverse Role of Solvents in Controlling Supramolecular Chirality

Supramolecular self-assembly stands for the spontaneous aggregation of small organic compounds or polymers into ordered structures at any scale. When being induced by inherent molecular chiral centers or ambient asymmetric factors, asymmetric spatial arrangement between building units shall occur, which is defined as supramolecular chirality. Except for molecular design, utilizing external stimulus factors to tune supramolecular chirality is a promising approach. In this Concept article, we particularly discuss the important role of solvents in manipulating the chirality of self-assembled systems. The impact of solvents on the chirality is generally based on three properties of solvents, i.e., chirality, polarity, and active coassembly with building blocks. Molecular self-assembly in chiral solvents could undergo the chirality transfer, exhibiting a chiral induction effect. Solvent polarity often determines intermolecular orientation. As a consequence, those building blocks with both polar and apolar segments might change their chirality depending on the solvent polarity. We elaborate the active participation of solvent molecules into ordered structures together with building blocks, where solvents and building blocks exhibit a coassembly manner. By specific treatments such as heating and cooling, solvents could be released or re-entrapped, allowing a smart control over supramolecular chirality. The solvent effect in manipulating two-dimensional chiral self-assemblies is then discussed. The perspective and future development in this research field are presented at last.     

A Boat-Shaped Tetracationic Macrocycle with a Semiconducting Organic Framework

We report the synthesis of a tetracationic macrocycle which contains two N,N′-bis(methylene)naphthalenediimide units inserted in between the pyridinium rings of the bipyridinium units in cyclobis(paraquat-p-phenylene) (CBPQT⁴⁺ or “blue box”) and describe the investigation of its potential use in materials for organic electronics. The incorporation of the two naphthalenediimide (NDI) units into the constitution of CBPQT⁴⁺, not only changes the supramolecular properties of the tetracation in the solid state, but also has a profound influence on the electrochemical and electronic behavior of the resulting tetracationic macrocycle. In particular, the solid-state (super)structure, investigated by single-crystal X-ray diffraction, reveals the formation of a three-dimensional (3D) supramolecular framework with ca. 2.8 nm diameter one-dimensional (1D) hexagonal channels. Electrochemical studies on solid-state thin films of the macrocycle show that they exhibit semiconducting properties with a redox-conductivity of up to 7.6×10⁻⁴ S m⁻¹. Moreover, EPR and ENDOR spectroscopies show that charge is equally shared between the NDIs within the one-electron reduced state of the NDI-based macrocycle on the time scale of these techniques.     

The use of (metallo-)supramolecular initiators for living/controlled polymerization techniques

The introduction of supramolecular interactions in synthetic polymers seems to be a promising approach towards novel 'smart' materials that combine both the (reversible) supramolecular interactions and the properties of the polymers. In this tutorial review, the use of (metallo-)supramolecular initiators for the preparation of end-functionalized (metallo-)supramolecular polymers will be discussed in detail. The different polymerization techniques that have been applied as well as the different ligands and metal complexes that were used to initiate these polymerizations will be discussed together with the resulting polymer properties.     

How to Make Weak Noncovalent Interactions Stronger

By employing noncovalent interactions, chemists have constructed a variety of molecular aggregates with well‐defined structures and fascinating properties. In fabricating stable and large molecular assemblies, noncovalent interactions with high binding strength are needed. This Concept summarizes some strategies to modify and optimize the structures of building blocks for making weak noncovalent interactions stronger. The strategies include: 1) Preorganization of binding sites; 2) spatial confinement effects; 3) multivalent enhancement; 4) synergistic binding with multiple forces. Examples of the fabrication of supramolecular architectures by utilizing these strategies are presented and discussed. Guidance is offered in the construction and fabrication of stable molecular assemblies and supramolecular materials.     

Programming supramolecular peptide materials by modulating the intermediate steps in the complex assembly pathway: Implications for biomedical applications

Self-assembling peptides form a prominent class of supramolecular materials with in general good biocompatibility. To afford better control over the material properties, tremendous progress has been made in studying the supramolecular organization of the peptide assemblies. This knowledge has helped us to understand the correlation between the molecular structure of the peptide building blocks and the properties of the supramolecular products. However, peptide self-assembly consists of a complex pathway rather than a spontaneous thermodynamic process. This implies that the outcome of the self-assembly is critically governed by the assembly pathway. Here, we are going to discuss how peptide self-assembly can be modulated at the intermediate steps in the self-assembly pathway. The focus will be to demonstrate this engineering approach on the example of zero-dimensional/one-dimensional nanostructure selectivity over the β-sheet assembly pathway. In addition, we provide examples of biomedical applications of such steered peptide assemblies in the field of drug delivery and tissue engineering.     

The tandem Claisen rearrangement in the construction of building blocks for supramolecular chemistry

The tandem Claisen rearrangement is a simple but highly efficient reaction to synthesize useful building blocks for supramolecular chemistry. It provides in one step two new C-C bonds in very high yield. The scope and limits of this reaction will be discussed in this review and it will be shown, how macrocyclic compounds as well as rotaxanes or helicates can be formed by use of butenylidene bridged aromatic compounds obtained after the rearrangement reaction. Special aspects will cover the search for new receptors and sensors or for energy transfer properties. The contents of this tutorial review are within the field of preparative organic synthesis but in addition cover aspects of inorganic and supramolecular chemistry.     

Templates, "wheeled reagents", and a new route to rotaxanes by anion complexation: the trapping method

The topological aspects of rotaxanes are compared with those of the other families of mechanically interlocked molecules: catenanes and molecular knots. The role of the different types of templates in the well-known threading and clipping procedures often used for rotaxane synthesis are discussed. Finally the conceptually new trapping method that is based on the action of supramolecular nucleophiles formed by anionic stopper-wheel complexes is described.     

Coronarenes: recent advances and perspectives on macrocyclic and supramolecular chemistry

Synthetic macrocyclic host molecules always play an essential role in the establishment and development of supramolecular chemistry. Along with the continuous interests in the study of classical macrocycles, recent decades have witnessed the emergence and rapid development of the chemistry and supramolecular chemistry of novel and functional macrocycles. Owing to their easy availability, a self-tunable V-shaped cavity resulted from 1,3-alternate conformation, and diversified electronic features steered by the interplay between heteroatom linkages and aromatic rings, heteracalixaromatics act as a type of versatile and powerful macrocyclic hosts in molecular recognition and fabrication of supramolecular systems. Very recently, by means of engineering the bond connectivity or the recombination of chemical bonds within heteracalixaromatics, we have devised coronarenes, a new generation of macrocycles. In this concise review, macrocyclic and supramolecular chemistry of coronarenes are summarized in the order of their syntheses, structural features, molecular recognition and self-assembly properties. In the last part of this article, personal perspectives on the study of macrocyclic and supramolecular chemistry will also be discussed.     

Recent advances in biocompatible supramolecular assemblies for biomolecular detection and delivery

Inspired by sophisticated biological structures and their physiological processes,supramolecular chemistry has been developed for understanding and mimicking the behaviors of natural species. Through spontaneous self-assembly of functional building blocks,we are able to control the structures and regulate the functions of resulting supramolecular assemblies.Up to now,numerous functional supramolecular assemblies have been constructed and successfully employed as molecular devices, machines and biological diagnostic platforms.This review will focus on molecular structures of functional molecular building blocks and their assembled superstructures for biological detection and delivery.     

Template-Free Self-Assembly of Molecular Trefoil Knots and Double Trefoil Knots Featuring Cp*Rh Building Blocks

Understanding and controlling the topology of self-assembled structures plays a fundamental role in supramolecular chemistry. Herein, the preparation of a series of tetranuclear metallarectangles and hexanuclear trefoil knots featuring Cp*Rh building blocks by template-free self-assembly with four different rigid and flexible ligands is described. Transformations between the trefoil knots and the corresponding macrocycles can be induced by using concentration effects. Remarkably, the hexanuclear trefoil knot 5 was shown to assemble further to provide rare examples of [12+1] heteronuclear double trefoil knots ( 5 a/5 b/5 c/5 d ) through coordination of the amide oxygen atoms to the secondary metal ions Na⁺/K⁺/Ca²⁺/Cd²⁺. The synthetic results are supported by single-crystal XRD.     

Recent developments in the supramolecular chemistry of terpyridine-metal complexes

This critical review describes recent developments in the field of supramolecular chemistry of terpyridine-metal complexes. The synthesis and characteristics of single as well as multiple homo- and heterometallic complexes is discussed. Furthermore, complexes containing fullerenes, biological building blocks, extended aggregates of different architectures as well as rings are presented. A special emphasis is placed upon the properties (e.g. redox properties, luminescence etc.) of functional systems. Potential applications in optical nano-devices, molecular storage units, molecular switches and solar cells are discussed.     

Chiral induction by helical neighbour: spectroscopic visualization of macroscopic-interaction among self-sorted donor and acceptor π-stacks

Supramolecular induction of chirality to a π-stacked dialkoxynaphthalene (DAN)-fiber (made of achiral building blocks) from a neighbouring helical naphthalenediimide (NDI)-fiber is reported. CD-studies helped in understanding the nature of co-assembly in the donor-acceptor chromophore mixture from molecular to macroscopic scale.     

Simple Organic Salts Having a Naphthalenediimide (NDI) Core Display Multifunctional Properties: Gelation,Anticancer and Semiconducting Properties

Following a supramolecular synthon rationale, a dicarboxylic acid derivative having a naphthalenediimide (NDI) core, namely, bis‐N‐carboxymethyl naphthalenediimide ( NDI‐G ), was reacted with n‐alkyl amines with varying alkyl chain lengths to generate a new series of primary ammonium dicarboxylate (PAD) salts. The majority of the salts (≈85 %) were found to gel various polar solvents. The gels were characterized by dynamic rheology and high‐resolution electron microscopy. Single‐crystal and powder X‐ray diffraction analyses were used to study the supramolecular synthon present in one of the gelator salts (i.e., S8 ). Charge‐transfer (CT)‐induced gelation with donor molecules such as anthracene methanol ( Ant ) and pyrene ( Py ) was also possible with S8 . The CT complex ( S8.Ant ) displayed anticancer activity as probed by cell migration assay on the highly aggresive breast cancer cell line MDA‐MB‐231 . The DMSO gel of S8.Ant also displayed semiconducting behavior. To the best of our knowledge, simple organic salts with an NDI core that display such mulitifunctional properties are hitherto unknown.     

DNA-based supramolecular hydrogels: From construction strategies to biomedical applications

DNA-based supramolecular hydrogels are important and promising biomaterials for various applications due to their inherent biocompatibility and tunable physicochemical properties. The three-dimensional supramolecular matrix of DNA formed by non-covalently dynamic cross-linking provides exceptional adaptability, self-healing, injectable and responsive properties for hydrogels. In addition, DNA hydrogels are also ideal bio-scaffold materials owing to their tissue-like mechanics and intrinsic biological functions. Technically, DNA can assemble into supramolecular networks by pure complementary base pairing; it can also be combined with other building blocks to construct hybrid hydrogels. This review focuses on the development and construction strategies of DNA hydrogels. Assembly and synthesis methods, diverse responsiveness and biomedical applications are summarized. Finally, the challenges and prospects of DNA-based supramolecular hydrogels are discussed.     

Stepwise Adsorption of Alkoxy-Pyrene Derivatives onto a Lamellar,Non-Porous Naphthalenediimide-Template on HOPG

The development of new strategies for the preparation of multicomponent supramolecular assemblies is a major challenge on the road to complex functional molecular systems. Here we present the use of a non-porous self-assembled monolayer from uC₃₃-NDI-uC₃₃ , a naphthalenediimide symmetrically functionalized with unsaturated 33 carbon-atom-chains, to prepare bicomponent supramolecular surface systems with a series of alkoxy-pyrene ( PyrOR ) derivatives at the liquid/HOPG interface. While previous attempts at directly depositing many of these PyrOR units at the liquid/HOPG interface failed, the multicomponent approach through the uC₃₃-NDI-uC₃₃ template enabled control over molecular interactions and facilitated adsorption. The PyrOR deposition restructured the initial uC₃₃-NDI-uC₃₃ monolayer, causing an expansion in two dimensions to accommodate the guests. As far as we know, this represents the first example of a non-porous or non-metal complex-bearing monolayer that allows the stepwise formation of multicomponent supramolecular architectures on surfaces.     

Spatiotemporal dynamics of supramolecular polymers by in situ quantitative catalyst-free hydroamination

Implementing chemical reactivity into synthetic supramolecular polymers based on π-conjugated molecules has been of great interest to create functional materials with spatiotemporal dynamic properties. However, the development of an in situ chemical reaction within supramolecular polymers is still in its infancy, because one needs to design optimal π-conjugated monomers having excellent reactivity under mild conditions possibly without byproducts or a catalyst. Herein we report the synthesis of a supramolecular polymer based on ethynyl core-substituted naphthalenediimide (S-NDI2) molecules that react with various amines quantitatively in a nonpolar solvent, without a catalyst, at 298 K. Most interestingly, the in situ reaction of the S-NDI2 supramolecular polymer with a linear aliphatic diamine proceeded much faster than the homogeneous reaction of a monomeric naphthalenediimide with the same diamine, affording diamine-linked S-NDI2 oligomers and polymers. The acceleration of in situ hydroamination was presumably due to rapid intra-supramolecular cross-linking between ethynyl and amino groups fixed in close proximity within the supramolecular polymer. Such intra-supramolecular cross-linking did not occur efficiently with an incompatible diamine. The systematic kinetic studies of in situ catalyst-free hydroamination within supramolecular polymers provide us with a useful, facile and versatile tool kit for designing dynamic supramolecular polymeric materials based on electron-deficient π-conjugated monomers.

A supramolecular polymer based on ethynyl core-substituted naphthalenediimides reacted with various amines quantitatively without a catalyst, exhibiting unconventional reaction kinetics and products.     

Ligand-template directed assembly: an efficient approach for the supramolecular encapsulation of transition-metal catalysts

Supramolecular encapsulation of small guest molecules inside well-defined cavities of molecular capsules has witnessed broad attention because of the unusual behaviour of these systems. The molecular capsules generally consist of rigid complementary building blocks that are held together by multiple, complementary non-covalent interactions. Interestingly, it has been shown that chemical transformations can take place inside these capsules and in some examples the reaction is accelerated, while in other cases otherwise instable intermediates could be isolated in the capsulated form. Many reactions of interest require a transition-metal (TM) catalyst, and the creation of new capsules in which such catalysts are implemented within the structure is thus required for the development of resourceful type of catalyst systems for these processes. In this concept article we will discuss new strategies to arrive at such systems, with a focus on a ligand-templated approach. In this approach, multifunctional ligands are used as templates for the encapsulation process by supramolecular building blocks and concomitantly for the formation of TM complexes that are active in catalytic processes. The obtained encapsulated transition-metal catalysts show unusual reactivity and selectivity behaviour that will be discussed in detail.     

界面超分子聚合

超分子聚合物诞生于高分子化学与超分子化学的交叉融合,一般是指单体间通过非共价键作用连接形成的聚合物,并在溶液或体相中表现出类似聚合物的性质。目前超分子聚合物一般通过均相溶液聚合制备得到,但溶液中的超分子聚合是一个自发的组装过程,具有浓度依赖性,组装过程不易可控。为解决此问题,研究人员可以将超分子聚合从均相溶液转移到界面,在界面上可控地制备超分子聚合物。通过界面聚合制备超分子聚合物具有一些独特的优势,如可以制备得到分子量更高的超分子聚合物,易于制备一些缺陷少、面积大、有序的二维超分子聚合物等。本文基于在液-液、气-液和固-液三种界面上制备超分子聚合物的一些代表性工作,介绍了界面超分子聚合方法和应用,并展望其未来发展。