Hierarchical cooperative binary ionic porphyrin nanocomposites

Self-Assembled Nanostructure of Ionic Sn(IV)porphyrin Complex Based on Multivalent Interactions for Photocatalytic Degradation of Water Contaminants

[Sn(H2PO4)2(TPyHP)](H2PO4)4∙6H2O (2), an ionic tin porphyrin complex, was synthesized from the reaction of [Sn(OH)2TPyP] (1) with a dilute aqueous solution of a polyprotic acid (H3PO4). Complex 2 was fully characterized using various spectroscopic methods, such as X-ray single-crystal crystallography, 1H NMR spectroscopy, elemental analysis, FTIR spectroscopy, UV-vis spectroscopy, emission spectroscopy, EIS mass spectrometry, PXRD, and TGA analysis. The crystal structure of 2 reveals that the intermolecular hydrogen bonds between the peripheral pyridinium groups and the axially coordinated dihydrogen phosphate ligands are the main driving force for the supramolecular assembly. Simultaneously, the overall association of these chains in 2 leads to an open framework with porous channels. The photocatalytic degradation efficiency of methyl orange dye and tetracycline antibiotic by 2 was 83% within 75 min (rate constant = 0.023 min-1) and 75% within 60 min (rate constant = 0.018 min-1), respectively. The self-assembly of 2 resulted in a nanostructure with a huge surface area, elevated thermodynamic stability, interesting surface morphology, and excellent catalytic photodegradation performance for water pollutants, making these porphyrin-based photocatalytic systems promising for wastewater treatment.

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.

Porphyrin-Based Nanomaterials for the Photocatalytic Remediation of Wastewater: Recent Advances and Perspectives

Self-organized, well-defined porphyrin-based nanostructures with controllable sizes and morphologies are in high demand for the photodegradation of hazardous contaminants under sunlight. From this perspective, this review summarizes the development progress in the fabrication of porphyrin-based nanostructures by changing their synthetic strategies and designs. Porphyrin-based nanostructures can be fabricated using several methods, including ionic self-assembly, metal-ligand coordination, reprecipitation, and surfactant-assisted methods. The synthetic utility of porphyrins permits the organization of porphyrin building blocks into nanostructures, which can remarkably improve their light-harvesting properties and photostability. The tunable functionalization and distinctive structures of porphyrin nanomaterials trigger the junction of the charge-transfer mechanism and facilitate the photodegradation of pollutant dyes. Finally, porphyrin nanomaterials or porphyrin/metal nanohybrids are explored to amplify their photocatalytic efficiency.

Sn(IV)-Porphyrin-Based Nanostructures Featuring Pd(II)-Mediated Supramolecular Arrays and Their Photocatalytic Degradation of Acid Orange 7 Dye

Two robust Sn(IV)-porphyrin-based supramolecular arrays (1 and 2) were synthesized via the reaction of trans-Pd(PhCN)2Cl2 with two precursor building blocks (SnP1 and SnP2). The structural patterns in these architectures vary from 2D to 3D depending on the axial ligation of Sn(IV)-porphyrin units. A discrete 2D tetrameric supramolecule (1) was constructed by coordination of {(trans-dihydroxo)[5,10-bis(4-pyridyl)-15,20-bis(phenyl) porphyrinato]}tin(IV) (SnP1) with trans-PdCl2 units. In contrast, the coordination between the {(trans-diisonicotinato)[5,10-bis(4-pyridyl)-15,20-bis(phenyl)porphyrinato]}tin(IV) (SnP2) and trans-PdCl2 units formed a divergent 3D array (2). Axial ligation of the Sn(IV)-porphyrin building blocks not only alters the supramolecular arrays but also significantly modifies the nanostructures, including porosity, surface area, stability, and morphology. These structural changes consequently affected the photocatalytic degradation efficiency under visible-light irradiation towards acid orange 7 (AO) dye in an aqueous solution. The degradation efficiency of the AO dye in the aqueous solution was observed to be between 86% to 91% within 90 min by these photocatalysts.

Zn (II)-porphyrin-based photochemically green synthesis of novel ZnTPP/Cu nanocomposites with antibacterial activities and cytotoxic features against breast cancer cells

This study focuses on synthesizing novel nanocomposites, zinc(II)tetrakis(4-phenyl)porphyrin/Cu nanoparticles (ZnTPP/Cu-NPs),with antibacterial activity, fabricated through a single-step green procedure. In this regard, the self-assembly of ZnTPP was carried out through an acid-base neutralization method to prepare ZnTPP nanoparticles. Then, the copper nanoparticles (Cu-NPs) were grown on ZnTPP nanoparticles through a visible-light irradiated photochemical procedure in the absence and presence of polyacrylic acid (PAA) as a modulator. The effect of PAA on the morphological properties of the prepared nanocomposites was evaluated. Eventually, the antibacterial activity of nanocomposites with different morphologies was investigated. In this way, the average zone of inhibition growth of diameter, minimum inhibitory concentration, and minimum bactericidal concentration values was determined. Besides, the cytotoxicity of the nanocomposites was evaluated by (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay MCF-7and (HEK-293) cell lines. The specific features of the synthesized nanocomposites identified them as antibacterial compounds which have therapeutic effects on breast cancer.

Sn(IV) Porphyrin-Based Ionic Self-Assembled Nanostructures and Their Application in Visible Light Photo-Degradation of Malachite Green

A series of porphyrin-based ionic complexes were prepared through the reaction of two porphyrin precursors, 5,10,15,20-tetrakis(4-(2-pyridyl)phenyl)porphyrin H2TPhPyP (1) and trans-dihydroxo [5,10,15,20-tetrakis(4-(2-pyridyl)phenyl)porphyrinato]tin(IV) Sn(OH)2TPhPyP (2), with various acids (HCl, HNO3, CF3COOH, H2SO4, H2CO3, and H3PO4). The complexes were characterized via elemental analysis, 1H nuclear magnetic resonance spectroscopy, electrospray ionization mass spectrometry, Fourier transform infrared (FT-IR) spectroscopy, ultraviolet (UV)-visible spectroscopy, fluorescence spectroscopy, and field-emission scanning electron microscopy (FE-SEM). Each compound exhibited different results for UV-visible, fluorescence, FT-IR, and FE-SEM studies depending on the counter anions. The complexes possessed different self-assembled nanostructures based on electronic interactions between the cations of compounds 1 and 2 with different counter anions. These aggregated species are stabilized by electrostatic forces and the π-π stacking interactions between the two porphyrin rings, in which the counter anions play an important bridging role. The counter anions also play an important role in controlling the morphology and photocatalytic properties of the as-developed materials. The complexes were then used for the photocatalytic degradation of the malachite green (MG) dye in aqueous media under visible light irradiation for up to 70 min. A morphology-dependent photocatalytic degradation of the MG dye was observed for all the ionic complexes, with efficiencies ranging from 50% to 95%.

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.

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.

Kinetic Investigation on Tetrakis(4-Sulfonatophenyl)Porphyrin J-Aggregates Formation Catalyzed by Cationic Metallo-Porphyrins

Under mild acidic conditions, various metal derivatives of tetrakis(4-N-methylpyridinium)porphyrin (gold(III), AuT₄; cobalt(III), CoT₄; manganese(III), MnT₄ and zinc(II), ZnT₄) catalytically promote the supramolecular assembling process of the diacid 5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrin (H₂TPPS₄) into J-aggregates. The aggregation kinetics have been treated according to a well-established model that involves the initial formation of a critical nucleus containing m porphyrin units, followed by autocatalytic growth, in which the rate evolves as a power of time. An analysis of the extinction time traces allows to obtain the rate constants for the auto-catalyzed pathway, k_c, and the number of porphyrins involved in the initial seeding. The aggregation kinetics have been investigated at fixed H₂TPPS₄ concentration as a function of the added metal derivatives MT₄. The derived rate constants, k_c, obey a rate law that is first order in [MT₄] and depend on the specific nature of the catalyst in the order AuT₄ > CoT₄ > MnT₄ > ZnT₄. Both resonance light scattering (RLS) intensity and extinction in the aggregated samples increase on increasing [MT₄]. With the exception of AuT₄, the final aggregated samples obtained at the highest catalyst concentration exhibit a negative Cotton effect in the J-band region, evidencing the occurrence of spontaneous symmetry breaking. The role of the nature of the metal derivative in terms of overall charge and presence of axial groups will be discussed.

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.

Nanoparticles as template for porphyrin nanostructure growth

Porphyrins and metalloporphyrins are one of the most widely studied platforms for the construction of supramolecular structures. These compounds have an extended aromatic system that allows [Formula: see text]–[Formula: see text] stacking interactions which, together with hydrogen bonds, electrostatic forces and the formation of inter-metallic complexes arising from peripheral groups, offer a versatile platform to control the self-assembly mechanism. In this work, we present the study of nanostructures formed by self-assembly of the water-soluble porphyrins meso-tetra([Formula: see text]-methyl-4-pyridyl)porphyrin (TMPyP) and meso-tetra(4-sulfonatophenyl)porphyrin (TPPS) in the presence of hard nanotemplates. Different nanoparticles (silica, gold, and polystyrene), concentrations and synthetic procedures were explored. The obtained materials were characterized by SEM and AFM microscopies, UV-vis absorption spectroscopy and dynamic light scattering measurements. A clear modification of the SiO2 NP surface roughness using one-pot synthesis was observed. The results were variable depending on the porphyrin–surface interactions and concentrations used. At lower porphyrin concentrations, a shift of the Soret band was observed, while at higher concentrations, free NS were formed. This reflects a competition between surface and solution directed self-assembly.

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.

Hierarchical Self-Assembly of a Porphyrin into Chiral Macroscopic Flowers with Superhydrophobic and Enantioselective Property

Supramolecular self-assembly provides an efficient way to fabricate simple units into various hierarchical nano/microstructures, which could mimic the bioself-assembly and develop functional materials. Since chiral molecules and chiral nanostructures are widely adopted by biological systems, an introduction of the chiral factor into the self-assembly process will provide better understanding of the biological systems. Here, using a chiral amphiphilic histidine to assist the self-assembly of a porphyrin with four carboxylic acids, we obtained hierarchical chiral nano- to microstructures. We have found that through the hydrogen bonds/electrostatic interactions between the porphyrin and histidine derivatives, the π-π stacking between the porphyrins, and hydrophobic interactions between the amphiphilic histidine, the two components could self-assemble into chiral nanohelices and microflowers. The supramolecular chirality of these structures was confirmed by scanning electron microscopy images as well as the circular dichroism spectra, which was found to follow the molecular chirality of the histidine derivative. More interestingly, the microflower structures formed a superhydrophobic and chiral surface, which exhibited macroscopic enantioselective recognition of some l- and d-amino acids via contact angle measurements.

Morphology-Controlled Synthesis and Metalation of Porphyrin Nanoparticles with Enhanced Photocatalytic Performance

The design and engineering of the size, shape, and chemistry of photoactive building blocks enables the fabrication of functional nanoparticles for applications in light harvesting, photocatalytic synthesis, water splitting, phototherapy, and photodegradation. Here, we report the synthesis of such nanoparticles through a surfactant-assisted interfacial self-assembly process using optically active porphyrin as a functional building block. The self-assembly process relies on specific interactions such as π-π stacking and metalation (metal atoms and ligand coordination) between individual porphyrin building blocks. Depending on the kinetic conditions and type of surfactants, resulting structures exhibit well-defined one- to three-dimensional morphologies such as nanowires, nanooctahedra, and hierarchically ordered internal architectures. Specifically, electron microscopy and X-ray diffraction results indicate that these nanoparticles exhibit stable single-crystalline and nanoporous frameworks. Due to the hierarchical ordering of the porphyrins, the nanoparticles exhibit collective optical properties resulted from coupling of molecular porphyrins and photocatalytic activities such as photodegradation of methyl orange (MO) pollutants and hydrogen production.

Pressure-Tuned Structure and Property of Optically Active Nanocrystals

Investigations through high-pressure X-ray scattering and spectroscopy in combination with theoretical computations shows that high-pressure compression can systematically tune the optical properties and mechanical stability of the molecular nanocrystals.

Hyperbranched crystalline nanostructure produced from ionic π-conjugated molecules

We report the first synthesis of a hyperbranched sheaf-like nanostructure by ionic self-assembly of organic semiconductors that forms via combined oriented attachment and Ostwald ripening growth mechanisms.

Morphology-controlled self-assembly and synthesis of photocatalytic nanocrystals

Abilities to control the size and shape of nanocrystals in order to tune functional properties are an important grand challenge. Here we report a surfactant self-assembly induced micelle encapsulation method to fabricate porphyrin nanocrystals using the optically active precursor zinc porphyrin (ZnTPP). Through confined noncovalent interactions of ZnTPP within surfactant micelles, nanocrystals with a series of morphologies including nanodisk, tetragonal rod, and hexagonal rod, as well as amorphous spherical particle are synthesized with controlled size and dimension. A phase diagram that describes morphology control is achieved via kinetically controlled nucleation and growth. Because of the spatial ordering of ZnTPP, the hierarchical nanocrystals exhibit both collective optical properties resulted from coupling of molecular ZnTPP and shape dependent photocatalytic activities in photo degradation of methyl orange pollutants. This simple ability to exert rational control over dimension and morphology provides new opportunities for practical applications in photocatalysis, sensing, and nanoelectronics.

Interfacial self-assembly driven formation of hierarchically structured nanocrystals with photocatalytic activity

We report the synthesis of hierarchical structured nanocrystals through an interfacial self-assembly driven microemulsion (μ-emulsion) process. An optically active macrocyclic building block Sn (IV) meso-tetraphenylporphine dichloride (tin porphyrin) is used to initiate noncovalent self-assembly confined within μ-emulsion droplets. In-situ studies of dynamic light scattering, UV-vis spectroscopy, and electron microscopy, as well as optical imaging of reaction processes suggest an evaporation-induced nucleation and growth self-assembly mechanism. The resulted nanocrystals exhibit uniform shapes and sizes from ten to a hundred nanometers. Because of the spatial ordering of tin porphyrin, the hierarchical nanocrystals exhibit collective optical properties resulting from the coupling of molecular tin porphyrin and photocatalytic activities in the reduction of platinum nanoparticles and networks and in photodegradation of methyl orange (MO) pollutants.

Porphyrins functionalized by quaternary pyridinium units

In this review, free-base and metalloporphyrins, functionalized on meso-positions by quaternary pyridinium units, also referred to as cationic porphyrins, are presented. The article consists of five parts. In the first part free-base porphyrins are described, especially taking account on generation of singlet oxygen; next parts concern metalloporphyrins. The second and third parts deal with zinc and manganese porphyrins, respectively; in the fourth part copper, palladium, and platinum porphyrins are presented. In the fifth part, describing porphyrins with various metal ions an attention is paid to porphyrin metal-organic frameworks (MOFs) and metal-organic materials (MOMs) in which metalloporphyrins are immobilized; syntheses and characterization of obtained products are shown.

Protonation state of core nitrogens in the meso-tetra(4-carboxyphenyl)porphyrin impacts the chemical and physical properties of nanostructures formed in acid solutions

Organic self-assemblies of meso-tetra (4-carboxyphenyl)porphine (TCPP) prepared in trifluoroacetic acid (TFA) and hydrochloric acid solutions at pH < 1 were studied by X-ray photoelectron spectroscopy (XPS) in order to determine the protonation state of the porphyrin building blocks present in the solid self-assembled nanostructures. XPS measurements were conducted both at room and at elevated temperatures. Room temperature N 1s spectra showed two bands with a 3:1 intensity ratio consistent with three protonated and one unprotonated nitrogen in the structures prepared in both TFA and HCl solutions. We attribute this result to TCPP existing as a 50:50 mixture of the free-base and diacid forms of the porphyrin core in the self-assembled state. Upon heating to 150 °C the TCPP/TFA and TCPP/HCl nanomaterials exhibit loss of pyrrolic hydrogens and retain different amounts of their respective counter ions. Atomic force microscopy (AFM) and transmission electron microscopy (TEM) images of the nanostructures showed that these systems have different morphologies depending on the acid employed during fabrication and the post preparation temperature treatment. High resolution transmission electron microscopy (HRTEM) and selected area electron diffraction (SAED) of the TCPP nanostructures indicate that those prepared in HCl are crystalline while the nanoassemblies made in TFA are polycrystalline or amorphous.