Highly Fluorescent Rigid Supramolecular Polymeric Nanowires Constructed Through Multiple Hydrogen Bonds

Multiple hydrogen bonding driven supramolecular architectures and their biomedical applications

Supramolecular chemistry combines the strength of molecular assembly via various molecular interactions. Hydrogen bonding facilitated self-assembly with the advantages of directionality, specificity, reversibility, and strength is a promising approach for constructing advanced supramolecules. There are still some challenges in hydrogen bonding based supramolecular polymers, such as complexity originating from tautomerism of the molecular building modules, the assembly process, and structure versatility of building blocks. In this review, examples are selected to give insights into multiple hydrogen bonding driven emerging supramolecular architectures. We focus on chiral supramolecular assemblies, multiple hydrogen bonding modules as stimuli responsive sources, interpenetrating polymer networks, multiple hydrogen bonding assisted organic frameworks, supramolecular adhesives, energy dissipators, and quantitative analysis of nano-adhesion. The applications in biomedical materials are focused with detailed examples including drug design evolution for myotonic dystrophy, molecular assembly for advanced drug delivery, an indicator displacement strategy for DNA detection, tissue engineering, and self-assembly complexes as gene delivery vectors for gene transfection. In addition, insights into the current challenges and future perspectives of this field to propel the development of multiple hydrogen bonding facilitated supramolecular materials are proposed.

Recent Advances in Organic Molecular-to-Supramolecular Self-Assembled Room-Temperature Phosphorescent Materials for Biomedical Applications

This minireview focuses on recent advancements in organic molecular-to-supramolecular self-assembled room-temperature phosphorescent (RTP) materials and their prospective biomedical applications. RTP materials, having their unique capacity to emit long-lasting phosphorescence at ambient temperature, have piqued researchers' interest in various biological applications, including biosensing, bioimaging, drug delivery, and photodynamic therapy (PDT). These materials have several benefits, including high sensitivity, remarkable photostability, and low cytotoxicity. RTP materials' self-assembly into supramolecular structures improves their performance and broadens their uses. Researchers have built organic RTP systems with long-lasting phosphorescence by leveraging weak noncovalent interactions in aquatic conditions. These materials have demonstrated incredible promise as biosensors that enable sensitive analyte detection and as photosensitizers in PDT that target and sensitize specific cell types. The review also outlines future directions and challenges in developing and utilizing pure organic RTP materials for biological imaging purposes, providing valuable guidelines for their future design and application.

Truxene-Centered Electron Acceptors for Non-Fullerene Solar Cells: Alkyl Chain and Branched Arm Engineering

A series of symmetrical truxene-centered and 3-ethylrhodanine end-capped electron acceptors with high absorption coefficient, namely Tr(Hex)₆-3RD, Tr(Dec)₆-3RD, and Tr(Hex)₆-6RD, were prepared and constructed for non-fullerene solar cells. To satisfy solution-processability, multiple energy levels, and suitable morphology, these three acceptors were comparatively studied through alkyl chain (hexyl/decyl) and branched-arm engineering (three/six branched arms). The six-bladed propeller acceptor of Tr(Hex)₆-6RD recorded the power conversion efficiency (PCE) of 1.1% blending with PTB7-Th without additional additives and post-processing. This work highly broadens the potential applications of star-shaped truxene building blocks in the fields of organic electronics.

Metallacycle-Cored Supramolecular Polymers: Fluorescence Tuning by Variation of Substituents

Herein, we present a method for the preparation of supramolecular polymers with tunable fluorescence via the combination of metal-ligand coordination and phenanthrene-21-crown-7 (P21C7)-based host-guest interactions. A suite of rhomboidal metallacycles with different substituents were prepared via the coordination-driven self-assembly of a P21C7-based 60° diplatinum(II) acceptor and 120° dipyridyl donors. Upon variation of the substituents on the dipyridyl donors, the metallacycles exhibit emission wavelengths spanning the visible region (λmax = 427-593 nm). Metallacycle-cored supramolecular polymers were obtained via host-guest interactions between bis-ammonium salts and P21C7. The supramolecular polymers exhibit emission wavelengths similar to those of the individual metallacycles and higher fluorescent efficiency in solution and thin films. Utilizing a yellow-emitting supramolecular polymer thin film with high quantum yield (0.22), a white-light-emitting LED was fabricated by painting the thin film onto an ultraviolet LED. This study presents an efficient approach for tuning the properties of fluorescent supramolecular polymers and the potential of the metallacycle-cored supramolecular polymers as a platform for the fabrication of light-emitting materials with good processability and tunability.

Self-Assembled Fluorescent Organic Nanomaterials for Biomedical Imaging

Fluorescent nanomaterials, self-assembled from building blocks through multiple intermolecular interactions show diversified structures and functionalities, and are potential fluorescence contrast agents/probes for high-performance biomedical imaging. Self-assembled nanomaterials exhibit high stability, long circulation time, and targeted biological distribution. This review summarizes recent advances of self-assembled nanomaterials as fluorescence contrast agents/probes for biomedical imaging. The self-assembled nanomaterials are classified into two groups, i.e., ex situ and in situ construction of self-assembled nanomaterials. The advantages of ex situ as well as in situ constructed nanomaterials for biomedical applications are discussed thoroughly. The directions of future developments for self-assembled nanomaterials are provided.

Fluorescent Supramolecular Polymeric Materials

Fluorescent supramolecular polymeric materials are rising stars in the field of fluorescent materials not only because of the inherent optoelectronic properties originating from their chromophores, but also due to the fascinating stimuli-responsiveness and reversibility coming from their noncovalent connections. Especially, these noncovalent connections influence the fluorescence properties of the chromophores because their state of aggregation and energy transfer can be regulated by the assembly-disassembly process. Considering these unique properties, fluorescent supramolecular polymeric materials have facilitated the evolution of new materials useful for applications in fluorescent sensors, probes, as imaging agents in biological systems, light-emitting diodes, and organic electronic devices. In this Review, fluorescent supramolecular polymeric materials are classified depending on the types of main driving forces for supramolecular polymerization, including multiple hydrogen bonding, electrostatic interactions, π-π stacking interactions, metal-coordination, van der Waals interactions and host-guest interactions. Through the summary of the studies about fluorescent supramolecular polymeric materials, the status quo of this research field is assessed. Based on existing challenges, directions for the future development of this field are furnished.

In situ supramolecular polymerization promoted by the marriage of dynamic covalent bonding and pillar[5]arene-based host–guest interaction

A temperature and pH dual-responsive linear supramolecular polymer was efficiently constructed by unifying dynamic covalent bonding and pillar[5]arene-based host–guest interaction through in situ supramolecular polymerization.

Molecular Coplanarity and Self-Assembly Promoted by Intramolecular Hydrogen Bonds

Active conformational control is realized in a conjugated system using intramolecular hydrogen bonds to achieve tailored molecular, supramolecular, and solid-state properties. The hydrogen bonding functionalities are fused to the backbone and precisely preorganized to enforce a fully coplanar conformation of the π-system, leading to short π-π stacking distances, controllable molecular self-assembly, and solid-state growth of one-dimensional nano-/microfibers. This investigation demonstrates the efficiency and significance of an intramolecular noncovalent approach in promoting conformational control and self-assembly of organic molecules.

Functional supramolecular polymers for biomedical applications

As a novel class of dynamic and non-covalent polymers, supramolecular polymers not only display specific structural and physicochemical properties, but also have the ability to undergo reversible changes of structure, shape, and function in response to diverse external stimuli, making them promising candidates for widespread applications ranging from academic research to industrial fields. By an elegant combination of dynamic/reversible structures with exceptional functions, functional supramolecular polymers are attracting increasing attention in various fields. In particular, functional supramolecular polymers offer several unique advantages, including inherent degradable polymer backbones, smart responsiveness to various biological stimuli, and the ease for the incorporation of multiple biofunctionalities (e.g., targeting and bioactivity), thereby showing great potential for a wide range of applications in the biomedical field. In this Review, the trends and representative achievements in the design and synthesis of supramolecular polymers with specific functions are summarized, as well as their wide-ranging biomedical applications such as drug delivery, gene transfection, protein delivery, bio-imaging and diagnosis, tissue engineering, and biomimetic chemistry. These achievements further inspire persistent efforts in an emerging interdisciplin-ary research area of supramolecular chemistry, polymer science, material science, biomedical engineering, and nanotechnology.

A new class of red fluorescent organic nanoparticles: noncovalent fabrication and cell imaging applications

Cyano-substituted diarylethlene derivatives R-OMe (-H, -CF3) with different peripheral substituted groups were synthesized in high yield. Water-soluble red fluorescent organic nanoparticles (FONs) could be facilely prepared from them via hydrophobic interaction with polyoxyethylene-polyoxypropylene-polyoxyethylene triblock copolymer (Pluronic F127). The optical properties and surface morphology of the synthesized FONs were characterized, and their biocompatibilities as well as their applications in cell imaging were further investigated. We demonstrate that such red FONs exhibit antiaggregation-caused quenching properties, broad excitation wavelengths, excellent water dispersibilities, and biocompatibilities, making them promising for cell imaging.

Supramolecular self-assemblies as functional nanomaterials

In this review, we survey the diversity of structures and functions which are encountered in advanced self-assembled nanomaterials. We highlight their flourishing implementations in three active domains of applications: biomedical sciences, information technologies, and environmental sciences. Our main objective is to provide the reader with a concise and straightforward entry to this broad field by selecting the most recent and important research articles, supported by some more comprehensive reviews to introduce each topic. Overall, this compilation illustrates how, based on the rules of supramolecular chemistry, the bottom-up approach to design functional objects at the nanoscale is currently producing highly sophisticated materials oriented towards a growing number of applications with high societal impact.

Supramolecular Fluorescent Nanoparticles for Targeted Cancer Imaging

By a combination of excellent fluorescent performance with smart targeting capability for cancer-specific delivery, a promising class of calcein-based supramolecular fluorescent nanoparticles has been successfully prepared via a "bricks and mortar" strategy. Through tuning the molar ratio of adamantane-functionalized calcein (CA-AD)/β-cyclodextrin-grafted branched polyethylenimine (PEI-CD), the size of these fluorescent nanoparticles can be effectively controlled. Importantly, the β-cyclodextrin/adamantane (β-CD/AD = 1/1) host-guest interaction dramatically suppresses the π-π stacking and fluorescence self-quenching of calcein chromophores in water, leading to the formation of highly fluorescent nanoparticles. By introduction of the folate receptor, these fluorescent nanoparticles exhibit excellent cancer imaging efficiency.

Stimuli-responsive supramolecular polymeric materials

Supramolecular materials, dynamic materials by nature, are defined as materials whose components are bridged via reversible connections and undergo spontaneous and continuous assembly/disassembly processes under specific conditions. On account of the dynamic and reversible nature of noncovalent interactions, supramolecular polymers have the ability to adapt to their environment and possess a wide range of intriguing properties, such as degradability, shape-memory, and self-healing, making them unique candidates for supramolecular materials. In this critical review, we address recent developments in supramolecular polymeric materials, which can respond to appropriate external stimuli at the fundamental level due to the existence of noncovalent interactions of the building blocks.