Host-Guest Interactions Facilitated by Chalcogen Bonding within Selenadiazole Functionalised Porphyrin Nanotubes

The structural rigidity of tetrakis(4-pyridyl)porphyrin (TPyP) has been utilised to prepare a robust novel porous coordination polymer of composition Cd2(TPyP)(sez)2 (TPyP=5,10,15,20-tetra(4-pyridyl)porphyrin, sez=1,2,5-benzoselenadiazole-5-carboxylate). The coordination polymer may be described as a hexagonal porphyrin nanotube (PNT) and has the potential to bind guest molecules through chalcogen bonding. Single crystal X-ray diffraction (SCXRD) data indicate an internal pore diameter ~9 Å which represents ~35 % of the crystal volume. Immersion of the PNTs in solvents such as DMSO and CS2 result in the incorporation of these molecules within the nanotubes with chalcogen bonding between host and guest. The crystallographic guest-inclusion investigations are complemented by solid-state 77Se, 13C, 113Cd and 2H NMR studies which provide insights into dynamic behaviour. The porosity of the crystals was further explored using gas adsorption experiments, indicating the reversible uptake of CO2, CH4, H2 and N2. Structure-function relationships are clearly established from complementary crystallographic, NMR and adsorption investigations.

Porphyrin-based porous organic polymers synthesized using the Alder-Longo method: the most traditional synthetic strategy with exceptional capacity

Porphyrin is a typical tetrapyrrole chromophore-based pigment with a special electronic structure and functionalities, which is frequently introduced into various porous organic polymers (POPs). Porphyrin-based POPs are widely used in various fields ranging from environmental and energy to biomedicine-related fields. Currently, most porphyrin-based POPs are prepared via the copolymerization of specific-group-functionalized porphyrins with other building blocks, in which the tedious and inefficient synthesis procedure for the porphyrin greatly hinders the development of such materials. This review aimed to summarize information on porphyrin-based POPs synthesized using the Alder-Longo method, thereby skipping the complex synthesis of porphyrin-bearing monomers, in which the porphyrin macrocycles are formed directly via the cyclic tetramerization of pyrrole with monomers containing multiple aldehyde groups during the polymerization process. The representative applications of porphyrin-based POPs derived using the Alder-Longo method are finally introduced, which pinpoints a clear relationship between the structure and function from the aspect of the building blocks used and porous structures. This review is therefore valuable for the rational design of efficient porphyrin-based porous organic polymer systems that may be utilized in various fields from energy-related conversion/storage technologies to biomedical science.

Porous and Close Packed Supramolecular Assemblies from 2,4-Difluoronitrobenzene with Three Different Linkers and an n-Butylamine Cap

A porous structure formed from sheets with cavities and two close packed structures were crystallised from building blocks prepared from 2,4-difluoronitrobenzene, a diamine linker and n-butylamine. The porous structure crystallised from a flexible building block prepared using 1,4-diaminobutane as linker. The close packed structures were prepared using either piperazine or 1,4-bis(aminomethyl)benzene as a linker and have less conformational freedom.

Organic-Inorganic Porphyrinoid Frameworks for Biomolecule Sensing

Porphyrinoids and their analogous compounds play an important role in biosensing applications on account of their unique and versatile catalytic, coordination, photophysical, and electrochemical properties. Their remarkable arrays of properties can be finely tuned by synthetically modifying the porphyrinoid ring and varying the various structural parameters such as peripheral functionalization, metal coordination, and covalent or physical conjugation with other organic or inorganic scaffolds such as nanoparticles, metal-organic frameworks, and polymers. Porphyrinoids and their organic-inorganic conjugates are not only used as responsive materials but also utilized for the immobilization and embedding of biomolecules for applications in wearable devices, fast sensing devices, and other functional materials. The present review delineates the impact of different porphyrinoid conjugates on their physicochemical properties and their specificity as biosensors in a range of applications. The newest porphyrinoid types and their synthesis, modification, and functionalization are presented along with their advantages and performance improvements.

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.

2D Porphyrinic Metal-Organic Frameworks Featuring Rod-Shaped Secondary Building Units

Metal-organic frameworks (MOFs) encompass a rapidly expanding class of materials with diverse potential applications including gas storage, molecular separation, sensing and catalysis. So-called 'rod MOFs', which comprise infinitely extended 1D secondary building units (SBUs), represent an underexplored subclass of MOF. Further, porphyrins are considered privileged ligands for MOF synthesis due to their tunable redox and photophysical properties. In this study, the CuII complex of 5,15-bis(4-carboxyphenyl)-10,20-diphenylporphyrin (H2L-CuII, where H2 refers to the ligand's carboxyl H atoms) is used to prepare two new 2D porphyrinic rod MOFs PROD-1 and PROD-2. Single-crystal X-ray analysis reveals that these frameworks feature 1D MnII- or CoII-based rod-like SBUs that are coordinated by labile solvent molecules and photoactive porphyrin moieties. Both materials were characterised using infrared (IR) spectroscopy, powder X-ray diffraction (PXRD) spectroscopy and thermogravimetric analysis (TGA). The structural attributes of PROD-1 and PROD-2 render them promising materials for future photocatalytic investigations.

Porphyrin MOF-Derived Porous Carbons: Preparation and Applications

Metal–organic frameworks (MOFs) are crystalline materials with permanent porosity, composed of metal nodes and organic linkers whose well-ordered arrangement enables them to act as ideal templates to produce materials with a uniform distribution of heteroatom and metal elements. The hybrid nature of MOFs, well-defined pore structure, large surface area and tunable chemical composition of their precursors, led to the preparation of various MOF-derived porous carbons with controlled structures and compositions bearing some of the unique structural properties of the parent networks. In this regard, an important class of MOFs constructed with porphyrin ligands were described, playing significant roles in the metal distribution within the porous carbon material. The most striking early achievements using porphyrin-based MOF porous carbons are here summarized, including preparation methods and their transformation into materials for electrochemical reactions.

Recent Advances in Porphyrin-Based Inorganic Nanoparticles for Cancer Treatment

The application of porphyrins and their derivatives have been investigated extensively over the past years for phototherapy cancer treatment. Phototherapeutic Porphyrins have the ability to generate high levels of reactive oxygen with a low dark toxicity and these properties have made them robust photosensitizing agents. In recent years, Porphyrins have been combined with various nanomaterials in order to improve their bio-distribution. These combinations allow for nanoparticles to enhance photodynamic therapy (PDT) cancer treatment and adding additional nanotheranostics (photothermal therapy-PTT) as well as enhance photodiagnosis (PDD) to the reaction. This review examines various porphyrin-based inorganic nanoparticles developed for phototherapy nanotheranostic cancer treatment over the last three years (2017 to 2020). Furthermore, current challenges in the development and future perspectives of porphyrin-based nanomedicines for cancer treatment are also highlighted.

Mixed Tb/Dy coordination ladders based on tetra(carboxymethyl)thiacalix[4]arene: a new avenue towards luminescent molecular nanomagnets

The macrocyclic ligand calix[4]arene (L1) and its sulphur-containing analogue thia[4]calixarene (L2) are promising precursors for functional molecular materials as they offer rational functionalization with various organic groups. Here, we present the first example of lanthanide-based coordination polymers built from the macrocyclic thiacalix[4]arene backbone bearing four carboxylic moieties, namely, ligand H₄L3. The combination of H₄L3 with the Tb³⁺ and Dy³⁺ cations led to the formation of 1D ladder-type coordination polymers with the formula [Ln^IIIHL3DMF₃]·(DMF) (where DMF = dimethylformamide and Ln = Tb or Dy, denoted as HL3–Tb and HL3–Dy), which resulted from the coordination of the lanthanide cations with the partially deprotonated ligand HL3³⁻ that behaved as a T-shape connector. The coordination sphere around the metal was completed by the coordinated DMF solvent molecules. By combining both Tb³⁺ and Dy³⁺ cations, isostructural heterobimetallic solid solutions HL3–Tb_1−xDy_x were also prepared. HL3–Tb and HL3–Dy showed visible light photoluminescence originating from the f–f electronic transitions of pale green emissive Tb³⁺ and pale yellow emissive Dy³⁺ with efficient sensitization by the functionalized thia[4]calixarene ligand HL3. In the HL3–Tb_1−xDy_x solid solutions, the Tb/Dy ratio governed both the emission colour as well as the emission quantum yield, which reached even 28% at room temperature for HL3–Tb. Moreover, HL3–Dy exhibited a slow magnetic relaxation effect related to the magnetic anisotropy of the dodecahedral Dy³⁺ complexes, which were well isolated in the crystal lattice by expanded organic spacers.

The single crystals of the two isostructural Tb³⁺- and Dy³⁺-based coordination polymers (HL3–Tb and HL3–Dy) were structurally characterized, and their photophysical properties were investigated, together with their corresponding solid solutions.

Metalloporphyrinic metal-organic frameworks: Controlled synthesis for catalytic applications in environmental and biological media

Recently, as a new sub-family of porous coordination polymers (PCPs), porphyrinic-MOFs (Porph-MOFs) with biomimetic features have been developed using porphyrin macrocycles as ligands and/or pillared linkers. The control over the coordination of the porphyrin ligand and its derivatives however remains a challenge for engineering new tunable Porph-MOF frameworks by self-assembly methods. The key challenges exist in the following respects: (i) collapse of the large open pores of Porph-MOFs during synthesis, (ii) deactivation of unsaturated metal-sites (UMCs) by axial coordination, and (iii) the tendency of both coordinated moieties (at peripheral meso- and beta-carbon sites) and the N₄-pyridine core to coordinate with metal cations. In this respect, this review covers the advances in the design of Porph-MOFs relative to their counterpart covalent organic frameworks (Porph-COFs). The potential utility of custom-designed porphyrin/metalloporphyrins ligands is highlighted. Synthesis strategies of Porph-MOFs are also illustrated with modular design of hybrid guest@host composites (either Porph@MOFs or guest@Porph-MOFs) with exceptional topologies and stability. This review summarizes the synergistic benefits of coordinated porphyrin ligands and functional guest molecules in Porph-MOF composites for enhanced catalytic performance in various redox applications. This review shed lights on the engineering of new tunable hetero-metals open active sites within (metallo)porphyrin-MOFs as out-of-the-box platforms for enhanced catalytic processes in chemical and biological media.

Tetra- and poly-nuclear Cd(ii) complexes of an N3O4 Schiff base ligand: crystal structures, electrical conductivity and photoswitching properties

A tetranuclear and a polymeric Cd(ii) complex have been synthesized and characterized. The polymeric complex based device behaves as a Schottky barrier diode and exhibits a photoswitching property.

Porphyrin as Diagnostic and Therapeutic Agent

The synthesis and application of porphyrins has seen a huge shift towards research in porphyrin bio-molecular based systems in the past decade. The preferential localization of porphyrins in tumors, as well as their ability to generate reactive singlet oxygen and low dark toxicities has resulted in their use in therapeutic applications such as photodynamic therapy. However, their inherent lack of bio-distribution due to water insolubility has shifted research into porphyrin-nanomaterial conjugated systems to address this challenge. This has broadened their bio-applications, viz. bio-sensors, fluorescence tracking, in vivo magnetic resonance imaging (MRI), and positron emission tomography (PET)/CT imaging to photo-immuno-therapy just to highlight a few. This paper reviews the unique theranostic role of porphyrins in disease diagnosis and therapy. The review highlights porphyrin conjugated systems and their applications. The review ends by bringing current challenges and future perspectives of porphyrin based conjugated systems and their respective applications into light.

Coordination self-assembly through weak interactions in meso-dialkoxyphosphoryl-substituted zinc porphyrinates

The self-assembly of seven zinc 10-(dialkoxyphosphoryl)-5,15-diarylporphyrinates Zn5-Zn11 containing different substituents at the phosphonate and aryl groups was investigated. Single crystals of Zn5-Zn9 complexes were grown under the same conditions and analyzed by X-ray structural analysis. A supramolecular self-assembly is observed in all crystals through weak coordinative bonding of the phosphoryl group of one porphyrin molecule to the zinc(ii) ion of a second molecule. The geometry of the porphyrin macrocycle is similar in all of the studied crystals and the central zinc atom in each case adopts a distorted tetragonal pyramidal environment. However, the Zn5-Zn7 porphyrins display a 1D polymeric structure while the Zn8 and Zn9 complexes exist as discrete cyclotetramers in the crystals. This data demonstrates that the non-coordinating meso-aryl substituents of meso-(dialkoxyphosphoryl)porphyrins influence their crystalline organization. A self-assembly of the Zn5-Zn11 complexes is also observed in toluene and chloroform solutions over a large temperature range (223-323 K). According to NMR studies, the associates exhibit dynamic behavior. A well-defined supramolecular aggregate of complex Zn10 at 10-3 M in toluene and chloroform solutions was unambiguously characterized as a cyclotetramer [Zn10]4 by 1H NMR spectroscopy at 223 K. The structure of the Zn10 association in toluene and chloroform shows a concentration dependence. When a solution of Zn10 in toluene was diluted from 10-3 M to 10-5 M, the average number of molecules in the associated unit decreased to about two.

An Organic Zeolite With 10 Å Diameter Pores Assembles From a Soluble and Flexible Building Block by Non-Covalent Interactions

Two similar molecular building blocks, which both contain a hydrogen-bonded nitro group, have been prepared and crystallised. One structure has more flexibility with a butyl side chain which allows an open framework organic zeolite to form with large 10 Å diameter pores, whereas the other structure has less flexibility with an aryl side chain and is close packed. The pore size is comparable with those of the aluminophosphate VPI-5 (12 Å). It is concluded that some flexibility in the design of the building block for porous organic molecular materials was beneficial.

Helix-Sense-Selective Polymerization of Phenylacetylenes Having a Porphyrin and a Zinc-Porphyrin Group: One-Handed Helical Arrangement of Porphyrin Pendants

Newly synthesized two kinds of achiral phenylacetylenes having a free-base- or a zinc-porphyrin (1 and Zn1, respectively) were polymerized by using a chiral rhodium catalyst system, Rh⁺(nbd)[(η⁶-C₆H₅)B⁻(C₆H₅)₃] catalyst and (R)-(+)- or (S)-(⁻)-1-phenylethylamine ((R)- or (S)-PEA, respectively) cocatalyst. Poly(1) and poly(Zn1) in THF showed a Cotton signal at the absorption region of the porphyrin and the main chain in the circular dichroism (CD) spectra. This result suggests that poly(1) and poly(Zn1) exist in a conformation with an excess of one-handed helix sense and the porphyrin moiety arranged in chiral helical fashion. The one-handed helical structure of poly(1) could be sustained in a mixture of THF/HMPA (10/2, v/v) due to stabilizing by stacking effect of porphyrin moieties along the main chain. This is the first example about helix-sense-selective polymerization by using Rh⁺(nbd)[(η⁶-C₆H₅)B⁻(C₆H₅)₃] catalyst. Additionally, poly(Zn1) showed about 10 times larger CD intensity in comparison with poly(1). This result suggests the regularity of arrangement of the porphyrin in poly(Zn1) is higher compared with poly(1). Spatial arrangement of porphyrins was achieved by utilizing a one-handed helical poly(phenylacetylenes) as a template.

Supramolecular frameworks based on 5,10,15,20-tetra(4-carboxyphenyl)porphyrins

Hydrogen bonding is used to prepare porphyrin-containing supramolecular frameworks.

Carbene insertion into N–H bonds with size-selectivity induced by a microporous ruthenium–porphyrin metal–organic framework

A stable and porous porphyrinic metal–organic framework Ru-PMOF-1(Hf) has been prepared and used for N–H insertion reactions with high efficiency and selectivity.

Trace Oxygen Sensitive Material Based on Two Porphyrin Derivatives in a Heterodimeric Complex

The successful preparation of a novel dimer complex formed between 5,10,15,20-tetrakis(3,4-dimethoxyphenyl)-porphyrin Fe(III) chloride and (5,10,15,20-tetraphenylporphinato) dichlorophosphorus(V) chloride using the well-known reactivity of the P-X bond is reported. The obtained complex was characterized by UV-vis, Fourier transform infrared spectroscopy (FT-IR), fluorescence, ¹H-NMR, ¹³C-NMR, and ³¹P-NMR spectroscopic techniques and also by additional Heteronuclear Single Quantum Coherence (HSQC) and Heteronuclear Multiple Bond Correlation (HMBC) experiments in order to correctly assign the NMR signals. Scanning electron microscopy (SEM) and EDX quantifications completed the characterizations. This novel porphyrin dimer complex demonstrated fluorescence sensing of H₂O₂ in water for low oxygen concentrations in the range of 40-90 µM proving medical relevance for early diagnosis of diseases such as Alzheimer's, Parkinson's, Huntington's, and even cancer because higher concentrations of H₂O₂ than 50 μM are consideredcytotoxic for life. Due to its optical properties, this novel metalloporphyrin-porphyrin based complex is expected to show PDT and bactericidal activity under visible-light irradiation.

Supramolecular porphyrin-based metal–organic frameworks: Cu(ii) naphthoate–Cu(ii) tetrapyridyl porphine structures exhibiting selective CO2/N2 separation

Porphyrin-based MOFs with copper acetate or copper 1-naphthoate exhibit different pore structure and unique CO₂/N₂ selectivity.

A synchrotron study of [5,10,15,20-tetrakis(3-cyanophenyl)porphyrinato-κ4N5,N10,N15,N20]copper(II) nitrobenzene trisolvate at 80 K

Porphyrin assemblies display interesting photophysical properties and a relatively high thermal stability. Moreover,meso-functionalized porphyrins with virtually fourfold symmetry can be relatively readily synthesized from pyrrole and the appropriate aldehyde. A number of metallo derivatives of 5,10,15,20-tetrakis(4-cyanophenyl)porphyrin, where the N atom of the linear cyano group can act both as a donor for coordination bonds or as an acceptor for hydrogen bonds, have been structurally characterized by single-crystal X-ray analysis. The supramolecular and structural chemistry of the corresponding 2- and 3-cyanophenyl isomers of the parent porphyrin, however, has remained largely unexplored. The crystal structure of [5,10,15,20-tetrakis(3-cyanophenyl)porphyrinato]copper(II) (CuTCNPP) nitrobenzene trisolvate, [Cu(C48H24N8)]·3C6H5NO2, has been determined at 80 K by synchrotron single-crystal X-ray diffraction. CuTCNPP exhibits aC2h-symmetric ααββ conformation, despite an unsymmetrical crystal environment, and is situated on a crystallographic centre of symmetry. The CuIIion adopts a genuine square-planar coordination by the four pyrrole N atoms. The 24-membered porphyrin ring system shows no marked deviation from planarity. In the crystal, the CuTCNPP molecules and two nitrobenzene molecules are face-to-face stacked in an alternating fashion, resulting in corrugated layers. The remaining nitrobenzene guest molecule per CuTCNPP resides in the region between four neighbouring columnar stacks of CuTCNPP and sandwiched nitrobenzene molecules, and is disordered over four positions about a centre of symmetry.

Metal organic frameworks mimicking natural enzymes: a structural and functional analogy

In this review, we have portrayed the structure, synthesis and applications of a variety of biomimetic MOFs from an unprecedented angle.

On the synthesis of functionalized porphyrins and porphyrin conjugates via β-aminoporphyrins

A two-step methodology to prepare a series ofmeso-tetraarylporphyrin conjugates bearing water-soluble moieties, anchoring groups and receptor subunits.

A robust indium–porphyrin framework for CO2 capture and chemical transformation

A robust indium–porphyrin framework based on amido-decorated porphyrin ligands is used for CO₂ capture and chemical fixation, showing good catalytic activity and recyclability.

Recent developments in metal-metalloporphyrin frameworks

Metal-organic frameworks (MOFs) based on porphyrin or metalloporphyrin components are of particular interest due to their potential applications in molecular sorption, light-harvesting, and heterogeneous catalysis. This perspective is focused on recent advances in the syntheses and functional properties of metal-metalloporphyrin frameworks, which are classified according to coordination moieties on the porphyrin ligands.

Stable porphyrin Zr and Hf metal-organic frameworks featuring 2.5 nm cages: high surface areas, SCSC transformations and catalyses

Two isostructural porphyrin Zr and Hf metal-organic frameworks (FJI-H6 and FJI-H7) are rationally synthesized, and are constructed from 2.5 nm cubic cages. Notably, they both possess high water and chemical stability and can undergo single-crystal to single-crystal transformations to embed Cu2+ ions into the open porphyrin rings. FJI-H6 has a high BET surface area of 5033 m2 g-1. Additionally, they exhibit promising catalytic abilities to convert CO2 and epoxides into cyclic carbonates at ambient conditions.

A novel terbium-cobalt tetra(4-sulfonatophenyl)porphyrin: Synthesis, structure and photophysical and electrochemical properties

A novel terbium-cobalt porphyrin {[ Tb ( H 2 O )3][ Co ( TPPS )]}n•n H 3 O (1) (TPPS = tetra(4-sulfonatophenyl)porphyrin) has been synthesized via a hydrothermal reaction and structurally characterized by X-ray single crystal diffraction. Compound 1 is characterized by a three-dimensional (3-D) porous open framework, which is originated from the Co ( TPPS ) moieties interconnected by the terbium ions. The fluorescence study shows that compound 1 displays an emission band in the blue region. Nanosecond transient spectra reveals that the fluorescence lifetime is 1.14 ms. The cyclic voltammetry (CV) and differential pulse voltammetry (DPV) experiments discovers one reversible wave with E1/2 = -0.80 V .

Directed synthesis of a halogen-bonded open porphyrin network

A strategy for the elaboration of a halogen-bonded porphyrin network with nano-sized tubular channels is reported.