Self-assembly and self-metallization of porphyrin nanosheets

Constructing cuprous oxide-modified zinc tetraphenylporphyrin ultrathin nanosheets heterojunction for enhanced photocatalytic carbon dioxide reduction to methane

The application of supermolecular naonostructures in the photocatalytic carbon dioxide reduction reaction (CO2RR) has attracted increasing attentions. However, it still faces significant challenges, such as low selectivity for multi-electron products and poor stability. Here, the cuprous oxide (Cu2O)-modified zinc tetraphenylporphyrin ultrathin nanosheets (ZnTPP NSs) are successfully constructed through the aqueous chemical reaction. Comprehensive characterizations confirm the formation of type-II heterojunction between Cu2O and ZnTPP in Cu2O@ZnTPP, and the electron transfer from Cu2O to ZnTPP through the Zn-O-Cu bond under the static contact. Under the visible-light irradiation (λ > 420 nm), the optimized Cu2O@ZnTPP sample as catalyst for photocatalytic CO2RR exhibits the methane (CH4) evolution rate of 120.9 μmol/g/h, which is ∼ 4 and ∼ 10 times those of individual ZnTPP NSs (28.0 μmol/g/h) and Cu2O (12.8 μmol/g/h), respectively. Meanwhile, the CH4 selectivity of ∼ 98.7 % and excellent stability can be achieved. Further experiments reveal that Cu2O@ZnTPP has higher photocatalytic conversion efficiency than Cu2O and ZnTPP NSs, and the photoinduced electron transfer from ZnTPP to Cu2O can be identified via the path of ZnTPP→ (ZnTPP•ZnTPP)*→ ZnTPP-→ Zn-O-Cu → Cu2O. Consequently, Cu2O@ZnTPP exhibits a shorter electron-hole separation lifetime (3.3 vs. 9.3 ps) and a longer recombination lifetime (23.1 vs. 13.4 ps) than individual ZnTPP NSs. This work provides a strategy to construct the organic nanostructures for photocatalytic CO2RR to multi-electron products.

Supramolecular Self-Assembled Nanostructures Derived from Amplified Structural Isomerism of Zn(II)-Sn(IV)-Zn(II) Porphyrin Triads and Their Visible Light Photocatalytic Degradation of Pollutants

Two structural isomeric porphyrin-based triads (Zn(II)porphyrin-Sn(IV)porphyrin-Zn(II)porphyrin) denoted as T1 and T2 were prepared from the reaction of meso-[5-(4-hydroxyphenyl)-10,15,20-tris(3,5-di-tert-butylphenyl)porphyrinato]zinc(II) (ZnL) with trans-dihydroxo-[5,10-bis(3-pyridyl)-15,20-bis(phenyl)porphyrinato]tin(IV) (SnP1) and trans-dihydroxo-[5,15-bis(3-pyridyl)-10,20-bis(phenyl)porphyrinato]tin(IV) (SnP2), respectively. All the compounds were characterized using UV-vis spectroscopy, emission spectroscopy, ESI-MS, 1H NMR spectroscopy, and FE-SEM. Most importantly, the two structurally isomeric porphyrin-based triads supramolecularly self-assembled into completely different nanostructures. T1 exhibits a nanosphere morphology, whereas T2 exhibits a nanofiber morphology. The amplified geometric feature in the structural isomeric porphyrin-based triads dictates the physical and chemical properties of the two triads. Both compounds showed the morphology-dependent visible light catalytic photodegradation of rhodamine B dye (74-97% within 90 min) and tetracycline antibiotic (44-71% within 45 min) in water. In both cases, the photodegradation efficiency of T2 was higher than that of T1. The present investigation can significantly contribute to the remediation of wastewater by tuning the conformational changes in porphyrin-based photocatalysts.

Exploring Linker-Group-Guided Self-Assembly of Ultrathin 2D Supramolecular Nanosheets in Water for Synergistic Cancer Phototherapy

Water is ubiquitous in natural systems where it builds an essential environment supporting biological supramolecular polymers to function, transport, and exchange. However, this extreme polar environment becomes a hindrance for the superhydrophobic functional π-conjugated molecules, causing significant negative impacts on regulating their aggregation pathways, structures, and properties of the subsequently assembled nanomaterials. It especially makes the self-assembly of ultrathin two-dimensional (2D) functional nanomaterials by π-conjugated molecules a grand challenge in water, although ultrathin 2D functional nanomaterials have exhibited unique and superior properties. Herein, we demonstrate the organic solvent-free self-assembly of one-molecule-thick 2D nanosheets based on exploring how side chain modifications rule the aggregation behaviors of π-conjugated macrocycles in water. Through an in-depth understanding of the roles of linking groups for side chains on affecting the aggregation behaviors of porphyrins in water, the regulation of molecular arrangement in the aggregated state (H- or J-type aggregation) was attained. Moreover, by arranging ionic porphyrins into 2D single layers through J-aggregation, the ultrathin nanosheets (thickness ≈ 2 nm) with excellent solubility and stability were self-assembled in pure water, which demonstrated both outstanding 1O2 generation and photothermal capability. The ultrathin nanosheets were further investigated as metal- and carrier-free nanodrugs for synergetic phototherapies of cancers both in vitro and in vivo, which are highly desirable by combining the advantages and avoiding the disadvantages of the single use of PDT or PTT.

Porphyrin nanotubes based on a hydrogen-bonded organic framework

Tubular structures offer a wide variety of applications; therefore, designing such materials with distinct dimensions is highly desirable yet challenging. In the current report, we have demonstrated the synthesis of a one-dimensional (1D) tubular assembly comprising porphyrin nanoring subunits. The porphyrin nanoring (PNR) 2 bearing ester groups was synthesized via Pt-mediated cyclization and then hydrolyzed to obtain PNR 3 with carboxylic groups. Under optimized conditions, porphyrin nanotubes (PNTs) were formed through hydrogen bonding between the carboxylic groups of 3. The morphology investigated by both SEM and TEM displayed well-defined arrays of nanotube bundles up to several micrometers long. Small crystals of PNTs were obtained by heating a solution of 3 in DMSO. High-resolution transmission electron microscopy (HR-TEM) accompanied by selected-area electron diffraction (SAED) exhibited a line of diffractions with d-spacing values of 6.17, 3.08, 2.07, and 1.57 Å. The miller indices of these diffractions could be assigned as 300, 600, 900, and 1200, respectively, suggesting that an ordered structure of 1D PNTs has been formed.

Shape-assisted self-assembly

Self-assembly and molecular recognition are critical processes both in life and material sciences. They usually depend on strong, directional non-covalent interactions to gain specificity and to make long-range organization possible. Most supramolecular constructs are also at least partially governed by topography, whose role is hard to disentangle. This makes it nearly impossible to discern the potential of shape and motion in the creation of complexity. Here, we demonstrate that long-range order in supramolecular constructs can be assisted by the topography of the individual units even in the absence of highly directional interactions. Molecular units of remarkable simplicity self-assemble in solution to give single-molecule thin two-dimensional supramolecular polymers of defined boundaries. This dramatic example spotlights the critical function that topography can have in molecular assembly and paves the path to rationally designed systems of increasing sophistication.

Self-assembly and molecular recognition usually depend on strong, directional non-covalent interactions but also topography can play a role in the formation of supramolecular constructs which makes it nearly impossible to discern the potential of shape and motion in the creation of complexity. Here, the authors demonstrate that long-range order in supramolecular constructs can be assisted by the topography of the individual units even in the absence of highly directional interactions.

Three Isomeric Zn(II)-Sn(IV)-Zn(II) Porphyrin-Triad-Based Supramolecular Nanoarchitectures for the Morphology-Dependent Photocatalytic Degradation of Methyl Orange

Three isomeric Zn(II)-Sn(IV)-Zn(II) porphyrin-based triads (T2, T3, and T4) were synthesized by the reaction of common Zn(II) porphyrins (ZnL) with different Sn(IV) porphyrins (SnP n ). The Sn(IV) porphyrin precursors differ with respect to the position of the pyridyl-N atoms. All compounds were characterized by 1H NMR, UV-vis, fluorescence spectroscopy, electrospray ionization-mass spectrometry, and field-emission scanning electron microscopy measurements. In these structures, the intramolecular cooperative metal-ligand coordination of the 3-pyridyl nitrogen in SnP 3 with axial ZnL and the π-π interactions between the adjacent porphyrin triad are the determining factors affecting the nanostructures of T3. Owing to the geometrical constraints of the SnP 2 center, this type of interaction is not possible for T2. Therefore, only the π-π interactions affect the self-assembly process. In the case of SnP 4 , intermolecular coordinative interactions and then π-π interactions are responsible for the nanostructure of T4. The morphology-dependent photocatalytic degradation of methyl orange (MO) dye in aqueous solution under visible light irradiation was observed for these photocatalysts, and the degradation ratio of MO varied from 76 to 94% within 100 min. Nanorod-shaped T3 exhibited higher performance compared to nanosphere T2 and nanoflake T4.

Supramolecular polymerization based on metalation of porphyrin nanosheets in aqueous media

Despite its great potential in supramolecular chemistry to achieve structural complexity and sophisticated functionality, the kinetic control over the molecular self-assembly in coordination supramolecular polymerization still constitutes a challenge. Herein,...

Applications of Fluorous Porphyrinoids: An Update†

Porphyrins and related macrocycles have been studied broadly for their applications in medicine and materials because of their tunable physicochemical, optoelectronic and magnetic properties. In this review article, we focused on the applications of fluorinated porphyrinoids and their supramolecular systems and summarized the reports published on these chromophores in the past 5-6 years. The commercially available fluorinated porphyrinoids: meso-perfluorophenylporphyrin (TPPF₂₀ ) perfluorophthalocyanine (PcF₁₆ ) and meso-perfluorophenylcorrole (CorF₁₅ ) have increased photo and oxidative stability due to the presence of fluoro groups. Because of their tunable properties and robustness toward oxidative damage these porphyrinoid-based chromophores continue to gain attention of researchers developing advanced functional materials for applications such as sensors, photonic devices, component for solar cells, biomedical imaging, theranostics and catalysts.

Self-Assembled Nanomaterials Based on Complementary Sn(IV) and Zn(II)-Porphyrins, and Their Photocatalytic Degradation for Rhodamine B Dye

A series of porphyrin triads (1–6), based on the reaction of trans-dihydroxo-[5,15-bis(3-pyridyl)-10,20-bis(phenyl)porphyrinato]tin(IV) (SnP) with six different phenoxy Zn(II)-porphyrins (ZnLⁿ), was synthesized. The cooperative metal–ligand coordination of 3-pyridyl nitrogens in the SnP with the phenoxy Zn(II)-porphyrins, followed by the self-assembly process, leads to the formation of nanostructures. The red-shifts and remarkable broadening of the absorption bands in the UV–vis spectra for the triads in CHCl₃ indicate that nanoaggregates may be produced in the self-assembly process of these triads. The emission intensities of the triads were also significantly reduced due to the aggregation. Microscopic analyses of the nanostructures of the triads reveal differences due to the different substituents on the axial Zn(II)-porphyrin moieties. All these nanomaterials exhibited efficient photocatalytic performances in the degradation of rhodamine B (RhB) dye under visible light irradiation, and the degradation efficiencies of RhB in aqueous solution were observed to be 72~95% within 4 h. In addition, the efficiency of the catalyst was not impaired, showing excellent recyclability even after being applied for the degradation of RhB in up to five cycles.

Self-Assembly of Discrete Porphyrin/Calix[4]tube Complexes Promoted by Potassium Ion Encapsulation

The pivotal role played by potassium ions in the noncovalent synthesis of discrete porphyrin-calixarene nanostructures has been examined. The flattened-cone conformation adopted by the two cavities of octa-cationic calix[4]tube C4T was found to prevent the formation of complexes with well-defined stoichiometry between this novel water-soluble calixarene and the tetra-anionic phenylsulfonate porphyrin CuTPPS. Conversely, preorganization of C4T into a C_4v-symmetrical scaffold, triggered by potassium ion encapsulation (C4T@K⁺), allowed us to carry out an efficient hierarchical self-assembly process leading to 2D and 3D nanostructures. The stepwise formation of discrete CuTPPS/C4T@K⁺ noncovalent assemblies, containing up to 33 molecular elements, was conveniently monitored by UV/vis spectroscopy by following the absorbance of the porphyrin Soret band.

Supramolecular Porphyrin Nanostructures Based on Coordination-Driven Self-Assembly and Their Visible Light Catalytic Degradation of Methylene Blue Dye

A series of porphyrin triads (1–4), in which each triad is composed of a Sn(IV) porphyrin and two free-base (or Zn(II)) porphyrins, was synthesized and their self-assembled nanostructures were studied. Depending on the substituent on porphyrin moieties, each triad was self-assembled into a different nanostructure. In particular, the cooperative coordination of 3-pyridyl groups in the Sn(IV) porphyrin with the axial Zn(II) porphyrins in triad 4 leads to forming uniform nanofibers with an average width of 10–22 nm. Other triads without the coordinating interaction between the central Sn(IV) porphyrin and the axial porphyrins formed irregularly shaped aggregates in contrast. The morphologies of nanofiber changed drastically upon the addition of pyrrolidine, in which pyrrolidine molecules break down the self-assembly process by coordinating with the axial Zn(II) porphyrins. All porphyrin aggregates exhibited efficient photocatalytic performances on the degradation of methylene blue dye under visible light irradiation. The degradation efficiencies after 2 h were observed to be between 70% and 95% for the aggregates derived from the four triads.

Diameter-dependent structural and electronic property of fused porphyrin nanotubes: A density functional study

We have systematically carried out a density functional theory-based investigation to understand the structural and electronic properties of various fused metalloporphyrin nanotubes (MPNT; M = Sc and Ti) by varying their diameters ranging from 7.91 Å to 18.70 Å for ScPNT and 7.90 Å to 18.59 Å for TiPNT. Binding energies and curvature energies are calculated to access the binding strength and stability of the nanotubes (NTs). From band structure and density of states, it is observed that the ScPNTs are metallic in nature and TiPNTs are semiconductors with small band gaps. The energy gap increases with increasing tube diameter. Our study also indicates that the transition metal atoms play an important role in determining the electrical nature (metallic or semiconducting) of the NTs. Furthermore, work functions for the fused NTs are found to decrease with increasing tube diameter. These results may have direct relevance to the technological applications in terms of band gap engineering or controlled thermionic emission.

Preparations of Core H2O-Bound 5, 10, 15, 20-Tetrakis-4-chlorophenyl Porphyrin, 1 , and O-Methylation of Phenol and Its P-Substituted Analogues

The treatment of a dichloromethane solution of 5, 10, 15, 20-tetrakis-4-chlorophenyl porphyrin, P 1 , with methanolic solutions of each of phenol, p-amino phenol, and p-nitro phenol for just 1 h results in the formation of water-molecule-bound amorphous solids of P 1 . In addition to the straightforward access to the H2O-molecule-coordinated species of P 1 thus produced, the another chief advantage of this synthetic strategy is the successful recoveries of anisole, p-amino anisole, and p-nitro anisole at the end of the reactions. The present work therefore further reports the use of P 1 as an efficient catalyst for the selective O-methylation of phenols using methanol as an environmentally friendly methylating agent. The H2O-bound amorphous solids of P 1 exhibit higher-intensity absorption as well as photoluminescence emission bands in dichloromethane compared with the parent crystalline form. Further, the measurement of the solid-state emission properties of both the crystalline and amorphous forms indicates quenching of fluorescence bands corresponding to amorphous solids in comparison with that of parent crystalline form. The crystalline form of P 1 and the H2O-bound amorphous solids were further studied by scanning electron microscope/transmission electron microscope (SEM/TEM), powder X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET), and thermal analysis techniques. The results of these studies indicate change in morphological and structural features, surface areas, porosities, and thermal robustness upon core coordination of water molecules with the macrocyclic rings of P 1 .

Monitoring the Hierarchical Evolution from a Double-Stranded Helix to a Well-Defined Microscopic Morphology Based on a Turbine-like Aromatic Molecule

1H-Indazolo[1,2-b]phthalazine-5,10-dione IPDD with an approximate turbine-like spatial structure, primary assembled double-stranded helices at the first level, was predicted by quantum chemical calculations and confirmed by atomic force microscopy. The higher-dimensional hierarchical architectures including fibrils, helical fibers, spherical shells, and porous prismatic structures were observed in sequence by the scanning electron microscopy technique. The final porous prismatic structures sensitive to NH₃ vapors have the potential to be applied in gas sensing and absorbing materials.

Mechanism for Copper(II)-Mediated Disaggregation of a Porphyrin J-Aggregate

J-aggregates of anionic meso-tetrakis(4-sulfonatophenyl)porphyrin form at intermediate pH (2.3-3.1) in the presence of NiSO₄ or ZnSO₄ (ionic strength, I.S. = 3.2 M). These aggregates convert to monomeric porphyrin units via metallation with copper(II) ions. The kinetics for the disassembly process, as monitored by UV/vis spectroscopy, exhibits zeroth-order behavior. The observed zeroth-order rate constants show a two-term dependence on copper(II) ion concentrations: linear and second order. Also observed is an inverse dependence on hydrogen ion concentration. Activation parameters have been determined for the disassembly process leading to ΔH ^≠ = (+163 ± 15) kJ·mol^-1 and ΔS ^≠ = (+136 ± 11) J·K^-1. A mechanism is proposed in which copper(II) cation is in pre-equilibrium with a reactive site at the rim of the J-aggregate. An intermediate copper species is thus formed that eventually leads to the final metallated porphyrin either through an assisted attack of a second metal ion or through a direct insertion of the metal cation into the macrocycle core.

Cluster-Mediated Nucleation and Growth of J- and H-Type Polymorphs of Difluoroboron Avobenzone for Organic Microribbon Lasers

Controlled fabrication of organic polymorphisms with well-defined dimensions and tunable luminescent properties plays an important role in developing optoelectronic devices, sensors, and biolabeling agents but remains a challenge due to the weak intermolecular interactions among organic molecules. Herein, we developed a two-step solution self-assembly method for the controlled preparation of blue-emissive or green-emissive microribbons (MRs) of difluoroboron avobenzone (BF₂AVB) by adjusting the cluster-mediated nucleation and subsequent one-dimensional growth processes. We found that blue-emissive MRs belong to the monoclinic phase, in which BF₂AVB molecules form slipped π-stacks, resulting in J-aggregates with the solid-state photoluminescence efficiency φ = 68%. Meanwhile, green-emissive MRs are ascribed to the orthorhombic phase and exhibit cofacial π-stacks, which lead to H-aggregates with φ = 24%. Furthermore, these as-prepared MRs can both act as polymorph-dependent Fabry-Pérot resonators for lasing oscillators. The strategy described here might offer significant promise for the coherent light source of optoelectronic devices.

SMART Design of a Bulk-Capped Supramolecular Segment for the Assembly into Organic Interdigital Lipid Bilayer-Like (ILB) Nanosheets

Rational molecular design for the organic nanocrystal morphology still remains a challenge due to the structural diversity and complicated weak intermolecular interactions. In this work, a typical attractor-repulsor molecule N,N-diphenyl-4-(9-phenyl-fluoren-9-yl) phenylamine (TPA-PF) is designed to explore a general assembly strategy for 2D nanocrystals. Via an interdigital lipid bilayer-like (ILB) molecular packing mode, large-sized lamellar 2D nanosheets are obtained with a length:width:thickness ratio as ≈2500:1000:1. The d-spacing of the largest (001) plane is 1.32 nm, which equals to the thickness of a single interdigital stacking layer. The synergetic effect of the attractive supramolecular segment (TPA) and the repulsive bulky group (PF) is supposed to be the critical factor for the ILB packing that leads to the 2D structures. The attractor-repulsor molecule design is expected to be an effective strategy for the growth of 2D nanocrystals based on small organic molecules.

Self-Assembled One-Dimensional Porphyrin Nanostructures with Enhanced Photocatalytic Hydrogen Generation

There has been a widespread interest in the preparation of self-assembled porphyrin nanostructures and their ordered arrays, aiming to emulate natural light harvesting processes and energy storage and to develop new nanostructured materials for photocatalytic process. Here, we report controlled synthesis of one-dimensional porphyrin nanostructures such as nanorods and nanowires with well-defined self-assembled porphyrin networks that enable efficient energy transfer for enhanced photocatalytic activity in hydrogen generation. Preparation of these one-dimensional nanostructures is conducted through noncovalent self-assembly of porphyrins confined within surfactant micelles. X-ray diffraction and transmission electron microscopy results reveal that these one-dimensional nanostructures contain stable single crystalline structures with controlled interplanar separation distance. Optical absorption characterizations show that the self-assembly enables effective optical coupling of porphyrins, resulting in much more enhanced optical absorption in comparison with the original porphyrin monomers, and the absorption bands red shift to more extensive visible light spectrum. The self-assembled porphyrin network facilitates efficient energy transfer among porphyrin molecules and the delocalization of excited state electrons for enhanced photocatalytic hydrogen production under visible light.

(Metallo)porphyrins for potential materials science applications

The bottom-up approach to replace existing devices by molecular-based systems is a subject that attracts permanently increasing interest. Molecular-based devices offer not only to miniaturize the device further, but also to benefit from advanced functionalities of deposited molecules. Furthermore, the molecules itself can be tailored to allow via their self-assembly the potential fabrication of devices with an application potential, which is still unforeseeable at this time. Herein, we review efforts to use discrete (metallo)porphyrins for the formation of (sub)monolayers by surface-confined polymerization, of monolayers formed by supramolecular recognition and of thin films formed by sublimation techniques. Selected physical properties of these systems are reported as well. The application potential of those ensembles of (metallo)porphyrins in materials science is discussed.

Target-triggered cascade assembly of a catalytic network as an artificial enzyme for highly efficient sensing

Determining the catalytic activity of artificial enzymes is an ongoing challenge. In this work, we design a porphyrin-based enzymatic network through the target-triggered cascade assembly of catalytic nanoparticles. The nanoparticles are synthesized via the covalent binding of hemin to amino-coated gold nanoparticles and then the axial coordination of the Fe center with a dual-functional imidazole or pyridine derivative. The network, which is specifically formed by coordination polymerization triggered by Hg2+ as the target, shows high catalytic activity due to the triple amplification of enzymatic activity during the cascade assembly. The catalytic dynamics are comparable to those of natural horseradish peroxidase. The catalytic characteristics can be ultrasensitively regulated by the target, leading to a selective methodology for the analysis of sub-attomolar Hg2+. It has also been used for "signal-on" imaging of reactive oxygen species in living cells. This work provides a new avenue for the design of enzyme mimics, and a powerful biocatalyst with signal switching for the development of biosensing protocols.

Porphyrin-Based Nanostructures for Photocatalytic Applications

Well-defined organic nanostructures with controllable size and morphology are increasingly exploited in optoelectronic devices. As promising building blocks, porphyrins have demonstrated great potentials in visible-light photocatalytic applications, because of their electrical, optical and catalytic properties. From this perspective, we have summarized the recent significant advances on the design and photocatalytic applications of porphyrin-based nanostructures. The rational strategies, such as texture or crystal modification and interfacial heterostructuring, are described. The applications of the porphyrin-based nanostructures in photocatalytic pollutant degradation and hydrogen evolution are presented. Finally, the ongoing challenges and opportunities for the future development of porphyrin nanostructures in high-quality nanodevices are also proposed.

Water Dispersible and Biocompatible Porphyrin-Based Nanospheres for Biophotonics Applications: A Novel Surfactant and Polyelectrolyte-Based Fabrication Strategy for Modifying Hydrophobic Porphyrins

The hydrophobility of most porphyrin and porphyrin derivatives has limited their applications in medicine and biology. Herein, we developed a novel and general strategy for the design of porphyrin nanospheres with good biocompatibility and water dispersibility for biological applications using hydrophobic porphyrins. In order to display the generality of the method, we used two hydrophobic porphyrin isomers as starting material which have different structures confirmed by an X-ray technique. The porphyrin nanospheres were fabricated through two main steps. First, the uniform porphyrin nanospheres stabilized by surfactant were prepared by an interfacially driven microemulsion method, and then the layer-by-layer method was used for the synthesis of polyelectrolyte-coated porphyrin nanospheres to reduce the toxicity of the surfactant as well as improve the biocompatibility of the nanospheres. The newly fabricated porphyrin nanospheres were characterized by TEM techniques, the electronic absorption spectra, photoluminescence emission spectra, dynamic light scattering, and cytotoxicity examination. The resulting nanospheres demonstrated good biocompatibility, excellent water dispersibility and low toxicity. In order to show their application in biophotonics, these porphyrin nanospheres were successfully applied in targeted living cancer cell imaging. The results showed an effective method had been explored to prepare water dispersible and highly stable porphyrin nanomaterial for biophotonics applications using hydrophobic porphyrin. The approach we reported shows obvious flexibility because the surfactants and polyelectrolytes can be optionally selected in accordance with the characteristics of the hydrophobic material. This strategy will expand the applications of hydrophobic porphyrins owning excellent properties in medicine and biology.

Semi-insulating behaviour of self-assembled tin(IV)corrole nanospheres

Three novel tin(iv)corrole complexes have been prepared and characterized by various spectroscopic techniques including single crystal X-ray structural analysis. Packing diagrams of the tin(iv)corroles revealed that corrolato-tin(iv)-chloride molecules are interconnected by intermolecular C-HCl hydrogen bonding interactions. HCl distances are 2.848 Å, 3.051 Å, and 2.915 Å, respectively, for the complexes. In addition, the C-HCl angles are 119.72°, 144.70°, and 147.08°, respectively, for the complexes. It was also observed that in one of the three synthesized complexes dimers were formed, while in the other two cases 1D infinite polymer chains were formed. Well-defined and nicely organized three-dimensional hollow nanospheres (SEM images on silicon wafers) with diameters of ca. 676 nm and 661 nm are obtained in the complexes, forming 1D polymer chains. By applying a thin layer of tin(iv)corrole nanospheres to an ITO surface (AFM height images of ITO films; ∼200 nm in height), a device was fabricated with the following composition: Ag/ITO-coated glass/tin(iv)corrole nanospheres/ITO-coated glass/Ag. The resistivity (ρ) of the nanostructured film was calculated to be ∼2.4 × 10(8) Ω cm, which falls in the range of semi-insulating semiconductors. CAFM current maps at 10 V bias show bright spots with a 10-20 pA intensity and indicate that the nanospheres (∼250 nm in diameter) are the electron-conducting pathway in the device. The semi-insulating behavior arises from the non-facile electron transfer in the HOMOs of the tin(iv)corrole nanospheres.

Water-soluble porphyrin nanospheres: enhanced photo-physical properties achieved via cyclodextrin driven double self-inclusion

We describe a method to construct water-soluble porphyrinic nanospheres with enhanced photo-physical properties as a result of precluding (via intra-molecular host-guest interactions) the individual porphyrins units from aromatic-aromatic stacking.

Tetraphenylethene-based star shaped porphyrins: synthesis, self-assembly, and optical and photophysical study

Supramolecular self-assembly and self-organization are simple and convenient ways to design and create controlled assemblies with organic molecules, and they have provoked great interest due to their potential applications in various fields, such as electronics, photonics, and light-energy conversion. Herein, we describe the synthesis of two π-conjugated porphyrin molecules bearing tetraphenylethene moieties with high fluorescence quantum yield. Photophysical and electrochemical studies were conducted to understand the physical and redox properties of these new materials, respectively. Furthermore, these derivatives were used to investigate self-assembly via the solvophobic effect. The self-assembled aggregation was performed in nonpolar and polar organic solvents and forms nanospheres and ring-like nanostructures, respectively. The solution based aggregation was studied by means of UV-vis absorption, emission, XRD, and DLS analyses. Self-assembled ring-shape structures were visualized by SEM and TEM imaging. This ring-shape morphology of nanosized macromolecules might be a good candidate for the creation of artificial light-harvesting nanodevices.

Two-dimensional soft nanomaterials: a fascinating world of materials

The discovery of graphene has triggered great interest in two-dimensional (2D) nanomaterials for scientists in chemistry, physics, materials science, and related areas. In the family of newly developed 2D nanostructured materials, 2D soft nanomaterials, including graphene, Bx Cy Nz nanosheets, 2D polymers, covalent organic frameworks (COFs), and 2D supramolecular organic nanostructures, possess great advantages in light-weight, structural control and flexibility, diversity of fabrication approaches, and so on. These merits offer 2D soft nanomaterials a wide range of potential applications, such as in optoelectronics, membranes, energy storage and conversion, catalysis, sensing, biotechnology, etc. This review article provides an overview of the development of 2D soft nanomaterials, with special highlights on the basic concepts, molecular design principles, and primary synthesis approaches in the context.

N-doped mesoporous inverse opal structures for visible-light photocatalysts

N-doped, mesoporous IO TiO₂ structures were fabricated as visible-light photocatalysts.

Self-assembly and optical properties of a porphyrin-based amphiphile

A porphyrin-based amphiphile that exhibits various self-assembled nanostructures in different solvents has been successfully prepared. The effect of aggregated structure on optical properties of this amphiphile has been well investigated. Furthermore, this porphyrin-based amphiphile and its assemblies show dynamic/reversible variations in morphology and optical properties in response to light.

Porphyrin nanoassemblies via surfactant-assisted assembly and single nanofiber nanoelectronic sensors for high-performance H₂O₂ vapor sensing

Porphyrins are recognized as important π-conjugated molecules correlating supramolecular chemistry, nanoscience, and advanced materials science. So far, as their supramolecular nanoassemblies are addressed, most efforts focus on the photo- or opto-related subjects. Beyond these traditional subjects, it is strongly desired to develop advanced porphyrin nanoassemblies in some other new topics of paramount importance. By means of a surfactant-assisted assembly, we herein show that porphyrins of different central metal ions, 5,10,15,20-tetra(4-pyridyl)-21H,23H-porphine (H2TPyP), zinc 5,10,15,20-tetra(4-pyridyl)-21H,23H-porphine (ZnTPyP), and oxo-[5,10,15,20-tetra(4-pyridyl)porphyrinato]titanium(IV) (TiOTPyP), could be organized to form irregular aggregates, short nanorods, and long yet straight nanofibers, respectively. Remarkably, in terms of an organic ribbon mask technique, we show that such long yet straight TiOTPyP nanofibers could be integrated into single nanofiber-based two-end nanoelectronics. Such simple nanodevices could serve as high-performance sensors of a satisfactory stability, reproducibility, and selectivity for an expeditious detection of vapor-phase H2O2. This provides a new alternative for a fast sensing of vapor-phase H2O2, which is currently an important issue in the fields of anti-terrorism, industrial healthcare, etc. In contrast to the traditional investigations focusing on the photo- or opto-related topics, our work endows porphyrin nanostructures with new opportunities as advanced nanomaterials in terms of portable yet high-performance nanoelectronic sensors, which is an issue of general concern in modern advanced nanomaterials.

Light-responsive three-dimensional microstructures composed of azobenzene-based palladium complexes

We describe not only fleeting assembly of photoisomerizable azobenzene-based palladium complexes into microstructured crystalline architectures but also their light-responsive functions. A transformation in the crystalline morphology from two-dimensional (2D) parallelogram-like sheets to three-dimensional (3D) cuboid- or rhombus-like structures was achieved by changing the solvent from tetrahydrofuran (THF) to acetone and N,N-dimethylformamide (DMF). The sizes of the structures, ranging from a few hundred nanometers to several hundred micrometers, were also modified by varying the complex concentration. In stark contrast to the very stable 2D sheets in the THF-H2O suspensions, exposure of 3D structures in polar DMF-H2O suspensions to ultraviolet (UV) light led to fast disassembly of the structures into isolated metal complexes and further dissociation of free azobenzene ligands from the complexes. In acetone-H2O suspensions, interestingly, disassembly of 3D cuboid-like structures into isolated complex components occurred upon exposure to UV light without further dissociation of azobenzene ligands from the palladium complexes. Considering the photoisomerization ability of the azobenzene-based palladium complex in common organic solvents, the π-stacking interactions that support 3D structures are likely to be sufficiently weak that they might be broken by the UV-induced trans-to-cis isomerization in more polar solvent mixtures. As a consequence, disassembly proceeded under UV light irradiation. Moreover, the effect of solvent polarity on the UV-assisted dissociation (in DMF-H2O) may be associated with the coordination ability of solvent molecules with the metal center.

Photo- and electro-functional self-assembled architectures of porphyrins

Recent developments in supramolecular strategies have enabled us to construct novel well-defined assemblies of dye molecules. These fundamental researches of such organic materials also entail the synthetic and photophysical processes of molecular aggregates at the nano- and micro-meter scale, since their optical properties significantly differ from those of monomeric species. One of the promising candidates for such functional molecules is a porphyrin dye, which acts as an electron donor as well as a sensitizer. In this perspective, the focus is on the recent advances in the construction of optically and electronically functionalized molecular architectures of porphyrins for light energy conversion and electronics. First, porphyrin aggregates with morphologies such as cube, rod and fiber, which are prepared by three different supramolecular techniques, are reported. Then, we discuss composite molecular nanoarchitectures of porphyrins and carbon nanotubes such as single-wall carbon nanotubes (SWCNTs), stacked-cup carbon nanotubes (SCCNTs) and carbon nanohorns (CNHs). Finally, the structural and photophysical properties of the composite assemblies of porphyrins and graphenes including polycyclic aromatic hydrocarbons (PAH) are presented.

Supramolecular chemistry of metal complexes in solution

Building on established supramolecular chemistry, metal coordination and organometallic chemistry have been widely explored for supramolecular polymers and nanostructures. Increasingly, research has demonstrated that this approach is promising for the synthesis of novel materials with functions and properties derived from metal elements and their coordination structures. Unique self-assembling behaviour and unexpected supramolecular structures are frequently discovered due to multiple non-covalent interactions in addition to metal coordination. However, an explicit understanding of the synergistic effects of non-covalent interactions for designed synthesis of metal containing assemblies with structure correlated properties remains a challenge to be addressed. Recent literature in the area is highlighted in this review in order to illustrate newly explored concepts and stress the importance of developing well understood and controlled supramolecular chemistry for designed synthesis.

Effect of dispersion on surface interactions of cobalt(ii) octaethylporphyrin monolayer on Au(111) and HOPG(0001) substrates: a comparative first principles study

Implication of dispersion interactions on geometric, adsorption and electronic properties of porphyrin monolayer on conductive surfaces using density functional theory.