Cyclodipeptide-bridged porphyrin dimer supramolecular assemblies

Porphyrin-based supramolecular polymers

Porphyrin derivatives are ubiquitous in bio-organisms and are associated with proteins that play important biological roles, such as oxygen transport, photosynthesis, and catalysis. Porphyrins are very fascinating research objects for chemists, physicists, and biologists owing to their versatile chemical and physical properties. Porphyrin derivatives are actively used in various fields, such as molecular recognition, energy conversion, sensors, biomedicine, and catalysts. Porphyrin derivatives can be used as building blocks for supramolecular polymers because their primitive structures have C₄ symmetry, which allows for the symmetrical introduction of self-assembling motifs. This review describes the fabrication of porphyrin-based supramolecular polymers and novel discoveries in supramolecular polymer growth. First, we summarise the (i) design concepts, (ii) growth mechanism and (iii) analytical methods of porphyrin-based supramolecular polymers. Then, the examples of porphyrin-based supramolecular polymers formed by (iv) hydrogen bonding, (v) metal coordination-based interaction, (vi) host-guest complex formation, and (vii) others are summarised. Finally, (viii) applications and perspectives are discussed. Although supramolecular polymers, in a broad sense, can include either two-dimensional (2D) networks or three-dimensional (3D) porous polymer structures; this review mainly focuses on one-dimensional (1D) fibrous supramolecular polymer structures.

Bioinspired porphyrin-peptide supramolecular assemblies and their applications

Inspired by the hierarchical chiral assembly of porphyrin-proteins in photosynthetic systems, the hierarchical self-assembly of porphyrin-amino acids/peptides provides a novel strategy for constructing functional materials. How to artificially simulate the assembly of porphyrins, proteins, and other cofactors in the photosynthesis system to obtain persistent strong light capture, charge separation and catalytic reactions has become an important concern in the construction of biomimetic photosynthesis systems. This paper summarizes the different assembly strategies adopted in recent years, the effects of driving forces on self-assembly, and the application of porphyrin-peptides in catalysis and biomedicine, and briefly discusses the challenges and prospects for future research.

Tunable Redox Potential Photocatalyst: Aggregates of 2,3-Dicyanopyrazino Phenanthrene Derivatives for the Visible-Light-Induced α-Allylation of Amines

This work highlights the tunable redox potential of 6,11-dibromo-2,3-dicyanopyrazinophenanthrene (DCPP3) aggregates, which can be formed through physical π-π stacking interactions with other DCPP3 monomers. Electrochemical and scanning electron microscopy showed that the reduction potential of [DCPP3]_n aggregates could be increased by decreasing their size. The size of [DCPP3]_n aggregates could be regulated by controlling the concentration of DCPP3 in an organic solvent. As such, a fundamental understanding of this tunable redox potential is essential for developing new materials for photocatalytic applications. The [DCPP3]_n aggregates as a visible-light photocatalyst in combination with Pd catalysts in the visible-light-induced α-allylation of amines were used. This [DCPP3]_n photocatalyst exhibits excellent photo- and electrochemical properties, including a remarkable visible-light absorption, long excited-state lifetime (16.6 μs), good triplet quantum yield (0.538), and high reduction potential (E_red([DCPP3]_n/[DCPP3]_n^-) > -1.8 V vs SCE).

Bioinspired Applications of Porphyrin Derivatives

Porphyrin derivatives are ubiquitous in nature and have important biological roles, such as in light harvesting, oxygen transport, and catalysis. Owing to their intrinsic π-conjugated structure, porphyrin derivatives exhibit characteristic photophysical and electrochemical properties. In biological systems, porphyrin derivatives are associated with various protein molecules through noncovalent interactions. For example, hemoglobin, which is responsible for oxygen transport in most vertebrates, consists of four subunits of a globular protein with an iron porphyrin derivative prosthetic group. Furthermore, noncovalently arranged porphyrin derivatives are the fundamental chromophores in light-harvesting systems for photosynthesis in plants and algae. These biologically important roles originate from the functional versatility of porphyrin derivatives. Specifically, porphyrins are excellent host compounds, forming coordination complexes with various metal ions that adds functionality to the porphyrin unit, such as redox activity and additional ligand binding at the central metal ion. In addition, porphyrins are useful building blocks for functional supramolecular assemblies because of their flat and symmetrical molecular architectures, and their excellent photophysical properties are typically utilized for the fabrication of bioactive functional materials. In this Account, we summarize our endeavors over the past decade to develop functional materials based on porphyrin derivatives using bioinspired approaches. In the first section, we discuss several synthetic receptors that act as artificial allosteric host systems and can be used for the selective detection of various chemicals, such as cyanide, chloride, and amino acids. In the second section, we introduce multiporphyrin arrays as mimics of natural light-harvesting complexes. The active control of energy transfer processes by additional guest binding and the fabrication of organic photovoltaic devices using porphyrin derivatives are also introduced. In the third section, we introduce several types of porphyrin-based supramolecular assemblies. Through noncovalent interactions such as metal-ligand interaction, hydrogen bonding, and π-π interaction, porphyrin derivatives were constructed as supramolecular polymers with formation of fiber or toroidal assembly. In the last section, the application of porphyrin derivatives for biomedical nanodevice fabrication is introduced. Even though porphyrins were good candidates as photosensitizers for photodynamic therapy, they have limitations for biomedical application owing to aggregation in aqueous media. We suggested ionic dendrimer porphyrins and they showed excellent photodynamic therapy (PDT) efficacy.

Peptide-Tetrapyrrole Supramolecular Self-Assemblies: State of the Art

The covalent and noncovalent association of self-assembling peptides and tetrapyrroles was explored as a way to generate systems that mimic Nature's functional supramolecular structures. Different types of peptides spontaneously assemble with porphyrins, phthalocyanines, or corroles to give long-range ordered architectures, whose structure is determined by the features of both components. The regular morphology and ordered molecular arrangement of these systems enhance the photochemical properties of embedded chromophores, allowing applications as photo-catalysts, antennas for dye-sensitized solar cells, biosensors, and agents for light-triggered therapies. Chemical modifications of peptide and tetrapyrrole structures and control over the assembly process can steer the organization and influence the properties of the resulting system. Here we provide a review of the field, focusing on the assemblies obtained from different classes of self-assembling peptides with tetrapyrroles, their morphologies and their applications as innovative functional materials.

Peptide-Modulated Self-Assembly of Chromophores toward Biomimetic Light-Harvesting Nanoarchitectonics

Elegant self-assembling complexes by the combination of proteins/peptides with functional chromophores are decisively responsible for highly efficient light-harvesting and energy transfer in natural photosynthetic systems. Mimicking natural light-harvesting complexes through synthetic peptides is attractive due to their advantanges of programmable primary structure, tunable self-assembly architecture and easy availability in comparison to naturally occuring proteins. Here, an overview of recent progresses in the area of biomimetic light-harvesting nanoarchitectonics based on peptide-modulated self-assembly of chromophores is provided. Adjusting the organization of chromophores, either by creating peptide-chromophore conjugates or by the non-covalent assembly of peptides and chromophores are highlighted. The light-harvesting properties, especially the energy transfer of the biomimetic complexes are critically discussed. The applications of such complexes in the mineralization of inorganic nanoparticles, generation of molecular hydrogen and oxygen, and photosynthesis of bioactive molecules are also included.

Synthesis and self-assembly of DNA–chromophore hybrid amphiphiles

DNA based amphiphiles are synthesized through a modular “click” chemistry approach, and the DNA–chromophore hybrid amphiphiles undergo amphiphilicity-driven self-assembly into vesicular or micellar nanostructures having a DNA shell and functional core.

Morphology-controlled self-assembly of an organic/inorganic hybrid porphyrin derivative containing polyhedral oligomeric silsesquioxane (POSS)

An organic/inorganic hybrid porphyrin derivative, namely, metal-free tetrakisphenyl porphyrin-polyhedral oligomeric silsesquioxanes (H2 TPP-POSS) was synthesized by azide-alkyne click chemistry. The self-assembly behavior of H2 TPP-POSS was systematically studied in CHCl3 at different concentrations and in solvents with different polarities. Novel nanovesicles could be obtained through the self-assembly of H2 TPP-POSS in CHCl3 at a concentration lower than 10(-4)  m. Diffuse microrods formed at a concentration higher than 10(-4)  M. Additionally, the polarity of the solvent also greatly influenced the assembled morphologies, and a series of assembled morphologies, including crescent-shaped micelles, spherical micelles, doughnut-shaped vesicles, and ordered square sheets, could form in solvents with different polarities.

Cascade sensing of gold and thiols with imidazole-bearing functional porphyrins

An imidazole-bearing zinc porphyrin (PZn) has been designed for the selective detection of Au³⁺, and the porphyrin and gold complex (PZn·Au³⁺) can additionally be used to identify gold-binding functional groups such as cysteine residues and other mercaptans.