Self-assembly of a π-electronic amphiphile consisting of a zinc porphyrin–fullerene dyad: formation of micro-vesicles with a high stability

Platinized spherical supramolecular nanoassemblies of a porphyrin: facile synthesis and excellent catalytic recyclability

Porphyrin-based supramolecular nanoassemblies of a spherical morphology have been attracting broad interest owing to their wide application possibilities in numerous fields of paramount significance. Most of the existing assembly protocols, however, either suffer from the requirement of elaborately-designed yet tediously-synthesized ad hoc porphyrins, the use of surfactant templates, or accurate consideration of the experimental parameters etc. The initiation of a facile surfactant-free fabrication protocol performable under ambient conditions using commercial porphyrins as building blocks is strongly desired. We herein report that a commercial metal-free porphyrins, 5,10,15,20-tetrakis(4-aminophenyl)porphyrin (TPPNH2), could be facilely organized to form well-defined discrete spherical nanoassemblies at room temperature by means of a simple reprecipitation method. We further find that the as-manufactured TPPNH2 nanospheres could work as photocatalysts towards the reduction of potassium tetrachloroplatinate(ii), leading to their self-platinization and the production of platinum/porphyrin nanosphere nanocomposites, wherein ultrathin Pt nanoparticles of a size of ca. 3 nm are immobilized on the porphyrin nanospheres. Significantly, by taking the advantage of their easy sedimentation from aqueous suspensions, we show that the as-produced composites could serve as qualified heterogeneous nanocatalysts in terms of their excellent catalytic stability and recyclability towards the reduction of 4-nitrophenol, where the catalytic reactivity exhibits only trivial changes even after the reactions have been repeated 8 times continuously. Taking into account the general concerns of porphyrins- and Pt-based nanostructures, this might provide a facile method for the construction of spherical porphyrin nanostructures with self-platinization capability. Meanwhile, considering the high cost and scarcity of Pt, our nanocomposites with excellent stability and recyclability likely have a bright future of potential uses.

Enhanced Electrochemiluminescence of One-Dimensional Self-Assembled Porphyrin Hexagonal Nanoprisms

In this work, we synthesized the one-dimensional nanostructure of zinc 5,10,15,20-tetra(4-pyridyl)-21H,23H-porphine (ZnTPyP) via a self-assembly technique. Using sodium dodecyl sulfate (SDS) as "soft template", the self-assembled ZnTPyP (SA-ZnTPyP) had the morphology of hexagonal nanoprisms with a uniform size (diameter of 100 nm). The SA-ZnTPyP exhibited remarkably different spectral properties compared to those of the original ZnTPyP. The as-prepared SA-ZnTPyP was used to modify glassy carbon electrodes (GCE), and the electrochemiluminescence (ECL) behaviors of the SA-ZnTPyP/GCE were investigated. The hydrophilic carbon dots (C-dots) could efficiently prevent the dissolution of SA-ZnTPyP in DMF containing 0.1 mol L^-1 TBAP and, simultaneously, could accelerate electron transfer. Therefore, the enhanced ECL was realized by C-dots/SA-ZnTPyP/GCE by using H₂O₂ as co-reactant. This amplification of ECL was further studied by ECL spectroscopies and cyclic voltammetry, and the corresponding mechanism was proposed.

Cooperative self-assembly of porphyrins with polymers possessing bioactive functions

This review covers recent research on design strategies for the cooperative self-assembly of porphyrins with polymers and its implementation as bioactive assembly.

Self-assembly of a tetrapodal adamantane with carbazole branches into hollow spherical aggregates in organic media

A hydrophobic tetrapodal molecule is composed of carbazole units at the periphery linked by a phenyl spacer on an adamantane core. Tetrapodal adamantane self-assembles into hollow spherical aggregates with a multilayer membrane in organic media. The spherical assembly size is dependent on the organic solvent used. Hollow spheres can entrap guest molecules within their internal spaces. By increasing the concentrations of tetrapodal molecules, hollow spheres fused into necklace-shaped nanostructures and two-dimensional networks were obtained.

Chemical designs of functional photoactive molecular assemblies

Molecular assemblies with defined structures capable of photo-induced electron transfer or photochemical reactions are reviewed, emphasizing their supramolecular features.

Programmed self-assembly of large π-conjugated molecules into electroactive one-dimensional nanostructures

Electroactive one-dimensional (1D) nano-objects possess inherent unidirectional charge and energy transport capabilities along with anisotropic absorption and emission of light, which are of great advantage for the development of nanometer-scale electronics and optoelectronics. In particular, molecular nanowires formed by self-assembly of π-conjugated molecules attract increasing attention for application in supramolecular electronics. This review introduces recent topics related to electroactive molecular nanowires. The nanowires are classified into four categories with respect to the electronic states of the constituent molecules: electron donors, acceptors, donor-acceptor pairs and miscellaneous molecules that display interesting electronic properties. Although many challenges still remain for practical use, state-of-the-art 1D supramolecular nanomaterials have already brought significant advances to both fundamental chemical sciences and technological applications.

pH dependent molecular self-assembly of octaphosphonate porphyrin of nanoscale dimensions: nanosphere and nanorod aggregates

Self-assembled nanostructures of zwitterionic octaphosphanatoporphyrin 1, of either nanoparticles or nanorods, depending on small changes in the pH, is demonstrated based on the J-aggregates. Porphyrin 1 self-assembled into nanosphere aggregates with a diameter of about 70–80 nm in the pH range 5–7, and nanorod aggregates were observed at pH 8.5. Hydrogen bonding, π-π stacking and hydrophilic interactions play important roles in the formation of this nanostructure morphology. Nanostructures were characterized by UV/Vis absorbance, fluorescence, atomic force microscopy (AFM) and transmission electron microscopy (TEM). This interesting pH dependent self-assembly phenomenon could provide a basis for development of novel biomaterials.

Chiroselective assembly of a chiral porphyrin-fullerene dyad: photoconductive nanofiber with a top-class ambipolar charge-carrier mobility

Upon slow admission of MeOH, the enantiomerically pure form of chiral amphiphilic porphyrin-fullerene dyad 1 in CH(2)Cl(2) self-assembles at 25 degrees C into nanofibers with a built-in donor/acceptor heterojunction, while its racemic form, under identical conditions, self-assembles into submicrometer-sized spheres with a donor/acceptor arrangement essentially different from that in the nanofiber assembly. Although a cast film of the latter hardly shows a photoconducting profile on micrometer-gap electrodes, the former sample clearly displays photoconduction with an ambipolar charge-transporting character. The electron and hole mobilities under zero electric field, as estimated from time-of-flight profiles, are 0.14 and 0.10 cm(2) V(-1) s(-1), respectively, which are comparable to or even better than those reported for top-class organic materials with a donor/acceptor heterojunction.

Vesicle self-assembly by tetrathiafulvalene derivatives in both polar and nonpolar solvents and pseudo-rotaxane mediated vesicle-to-microtube transformation

This paper reports the self-assemblies of vesicles from two tetrathiafulvalene (TTF) derivatives (T1 and T2), that bear four or two amphiphilic side chains, in both polar and nonpolar solvents. The formation of vesicles is evidenced by scanning electron microscopy (SEM), atomic force microscopy (AFM), transmission electron microscopy (TEM), and dynamic light scattering (DLS) experiments, while the microstructural aspects of the vesicles are investigated by UV-vis, (1)H NMR, and high resolution TEM, which support a monolayer model for the vesicles. It is revealed that the formation of vesicles is driven by the combination of multiple noncovalent interactions, including pi-pi stacking, hydrogen-bonding, van der Waals force, and S...S interactions. It is also found that, in the presence of electron-deficient cyclobis(paraquat-p-phenylene) tetracation cyclophane, vesicles of T2 can transform into microtubes as a result of the formation of the pseudo[2]rotaxane between the TTF unit of T2 and the cyclophane. This process can be reversed by introducing pristine TTF into the solution of microtubes, due to release of T2 from the pseudo[2]rotaxane through the formation of a more stable complex between pristine TTF and tetracation cyclophane.

Self-assembly of vesicles from amphiphilic aromatic amide-based oligomers

A novel class of linear arylamide oligomers has been designed and synthesized from naphthalene-2,7-diamine and benzene-1,3,5-tricarboxylic acid segments. The molecules carry two (tert-butoxycarbonylamino) groups at the ends and one to three hydrophilic N,N-bis(2-(2-(2-methoxyethoxy)ethoxy)ethyl)amino groups at one side of the backbone. The oligomers self-assembled into vesicular structures in methanol as a result of ordered stacking of the oligomeric amide backbones, which were evidenced by SEM, AFM, TEM, and fluorescent micrography experiments. It was also found that the tert-butoxycarbonylamino groups at the ends played an important role in promoting the ordered stacking of the backbones. Structural factors that affected the self-assembly of the oligomers were investigated. A two-layer model that was supported by TEM has been proposed for the formation of the vesicular structures, which was driven by both the hydrogen bonding and aromatic stacking.

Self-assembly and properties of low-dimensional nanomaterials based on π-conjugated organic molecules

Building supramolecular architectures with well-defined shapes and functions is of great importance in materials science, nanochemistry, and biomimetic chemistry. In recent years, we have devoted much effort to the construction of well-defined supramolecular structures through noncovalent forces such as hydrogen bonding, π-stacking, metal-ligand bonds, and hydrophilic and hydrophobic interactions, with the aid of functional building blocks. The morphologies and their physical properties were studied, and new methods for the construction of one-dimensional nanoscale structures have been developed. In this review, we summarize our recent studies on the design and synthesis of the supramolecular systems, as well as the physical properties of nanoscale structures.

Challenges and breakthroughs in recent research on self-assembly

The controlled fabrication of nanometer-scale objects is without doubt one of the central issues in current science and technology. However, existing fabrication techniques suffer from several disadvantages including size-restrictions and a general paucity of applicable materials. Because of this, the development of alternative approaches based on supramolecular self-assembly processes is anticipated as a breakthrough methodology. This review article aims to comprehensively summarize the salient aspects of self-assembly through the introduction of the recent challenges and breakthroughs in three categories: (i) types of self-assembly in bulk media; (ii) types of components for self-assembly in bulk media; and (iii) self-assembly at interfaces.

Aggregation of a C60-didodecyloxybenzene dyad: structure, dynamics, and mechanism of vesicle growth

The mechanism of formation and the stability of spontaneously formed vesicles upon self-assembly of a partially ground-state charge-separated, nonpolar-polar-nonpolar fullerene(C60)-didodecyloxybenzene (DDB) dyad in binary solvent mixtures requiring a critical dielectric constant of approximately 30 are reported. Molecular interactions giving rise to defined vesicles with in-plane bilayer packing are detailed from the predominant van der Waals and electrostatic interactions existing on the dyad's framework. The vesicles are formed with a large bending rigidity of 18kBT, which on further extraction into a polar water medium resulted in uniform spheres that corroborated well with the theoretical predictions. Furthermore, the water-extracted spherical dyad aggregates at an increased dyad concentration, leading to the formation of giant micrometer-sized fractals following diffusion-limited cluster aggregation. These dyad aggregates act as efficient quenchers of fluorescent dyes with a quenching rate of 4.6 x 10(13) M(-1) s(-1).