Neo-Porphyrinoids: New Members of the Porphyrinoid Family

Composite porphyrin-based conjugated microporous polymer/graphene oxide capable of photo-triggered combinational antibacterial therapy and wound healing

Developing antibiotic-free treatment strategies to cope with the crisis on drug-resistant bacteria, are urgently needed. Antibiotics-independent physical approaches, especially the non-invasive phototherapies, worked through the assistance of photosensitizer (PS), have geared intensive attention and interests. Here, composite porphyrin-based conjugated microporous polymer/graphene oxide, denoted as GO-TAPP, combining the advantages of each component perfectly, was developed as broad-spectrum antibacterial agent. GO-TAPP, prepared via the self-oxidation coupling of tetraethynyl porphyrin on the surface of graphene oxide, could exert synergistic photothermal (PTT, ascribed to the graphene) and photodynamic (PDT, derived from the Porphyrin polymer) antimicrobial effectiveness. Both the in vivo and in vitro experiments have confirmed GO-TAPP are extremely potent against the Gram-positive (Staphylococcus aureus) and Gram-negative (Escherichia coli) pathogens, which presents a remarkably enhanced sterilizing effect in comparison with its counterparts (the bare GO, and TAPP). Meanwhile, the synergistic effect of GO-TAPP could significantly accelerate the healing of open wound infected by bacterial. Altogether, this work proposed a new approach for the rational preparation of highly biocompatible graphene-based composite materials as antibiotic-free agents with synergistic antibacterial effect to combat bacterial infections.

Fast cathodic electrodeposition of ZnTCPP-functionalized metal-organic framework films for preparation of a fluorescent aptamer sensor for microcystin determination

A one-step electrodeposition-assisted self-assembly technique has been developed for preparation of ZnTCPP@MOF films with three-dimensional mesoporous structure in a three-electrode system. The internal structure of the ZnTCPP@MOF films was tuned by adjusting the electrochemical deposition voltage, deposition time, and the concentration of ZnTCPP at room temperature. The ZnTCPP@MOF films under different deposition conditions were characterized by scanning electron microscopy, Fourier transformation infrared spectroscopy, and X-ray photoelectron spectroscopy. The prepared ZnTCPP@MOF films exhibited excellent fluorescence properties, in which ZnTCPP molecules were encapsulated inside the MOF as fluorescent signal probes and structure-directing agents, which affected the electrochemical response of the ZnTCPP@MOF films. The sensing platform based on ZnTCPP@MOF film was used to detect microcystin with a wide determination range (1.0 × 10^-12 mol/L ~ 1.0 × 10^-5 mol/L), low determination limit (3.8 × 10^-13 mol/L), and high sensitivity. More importantly, the strategy is simple, low-cost, green, and environmentally friendly, and it provides a new strategy for the direct use of MOFs films as signaling components.

Organometallic chemistry confined within a porphyrin-like framework

The world of modified porphyrins changed forever when an N-confused porphyrin (NCP), a porphyrin isomer, was first published in 1994. The replacement of one inner nitrogen with a carbon atom revolutionised the chemistry that one is able to perform within the coordination cavity. One could explore new pathways in the organometallic chemistry of porphyrins by forcing a carbon fragment from the ring or an inner substituent to sit close to an inserted metal ion. Since the NCP discovery, a series of modifications became available to tune the coordination properties of the cavity, introducing a fascinating realm of carbaporphyrins. The review surveys all possible carbatetraphyrins(1.1.1.1) and their spectacular coordination and organometallic chemistry.

Piperazine Bridged Thianorrole Dimer

Oxidative cyclization of open chain thiabilanes yielded the first examples of unique piperazine bridged thianorrole dimers instead of the expected thianorrole monomer. In the thianorrole dimer, the two thianorrole monomeric units are linked via two direct pyrrole C-C bonds by involving the inverted pyrrole and adjacent pyrrole rings of each thianorrole macrocycle and generate a six-membered piperazine ring that bridges the two thianorrole macrocycles. The spectral studies indicated that the thianorrole dimers are nonaromatic in nature.

Synthesis of Benzofuran-Embedded Selena- and Telluraporphyrins

The benzofuran-embedded selena- and telluraporphyrins are resulted by replacing the pyrrole ring that is across the selenophene/tellurophene ring in meso-tetraaryl 21-selenaporphyrin and 21-telluraporphyrin respectively by a benzofuran unit. Three examples of benzofuran-embedded selenaporphyrins and one example of benzofuran-embedded telluraporphyrin were synthesized by adopting a simple 3 + 2 synthetic protocol involving the condensation of benzofuran based tripyrrane with appropriate 2,5-bis(hydroxymethylaryl) selenophene/telluorophene to afford pure benzofuran-embedded selenaporphyrins and telluraporphyrin in 3-6% yields. The macrocycles were thoroughly characterized and studied by various spectroscopic and computational techniques. The spectral and computational studies certified their nonaromatic nature unlike aromatic meso-tetraaryl 21-selena/21-telluraporphyrins, which proves that replacement of pyrrole with a benzofuran ring results in complete alteration of electronic properties. The DFT studies revealed that the benzofuran moiety hinders π-electron delocalization in the macrocycle due to its inflexibility, and the macrocycles adopt highly deformed saddle-shaped structures. The absorption spectra of benzofuran-embedded selena- and telluraporphyrins showed one strong band at ∼350-380 nm and one broad band at ∼650-695 nm that extended up to ∼900 nm. However, the protonated derivatives of macrocycles absorb strongly in the NIR region with a band trailing up to 1200 nm. The electrochemical studies revealed that the macrocycles are electron deficient, and theoretical studies resembled the experimental observations.

Synthesis, Structure and Studies of Meso-Triaryl 22-Oxabenzonorroles

The first examples of meso-triaryl 22-oxabenzonorroles were synthesized in 18-21% yields by oxidation of appropriate meso-triaryl oxabenzobilane. The key precursors, the meso-triaryl oxabenzobilanes were synthesized readily by treating 16-oxatripyrrane with (1H-indol-3-yl)(p-tolyl)methanol under acid catalyzed conditions. The meso-triaryl 22-oxabenzonorroles were obtained in free base form by following our simple straight-forward synthetic strategy. The X-ray structure obtained for meso-tritolyl 22-oxabenzonorroles revealed that the indole ring was deviated by an angle of 41.27o from the mean plane. The NMR studies supported the presence of diatropic ring current effect as inner NH and CH protons were observed in the upfield region. The absorption spectra of 22-oxabenzonorroles exhibited one strong Soret band and four weak Q-bands. The electrochemical studies revealed that the macrocycles are electron rich and undergo easier oxidations. The DFT and TD-DFT studies were in agreement with the experimental observations and NICS and HOMA values supports the aromatic nature of meso-triaryl oxabenzonorroles.

Synthesis and Properties of Stable 20π Porphyrinoids

The 20π porphyrinoids are immediate higher homologues of 18π porphyrins and differ from porphyrins in aromaticity which in turn affects the structure, properties and chemical reactivities. Research over the years indicated that the 20π porphyrinoids can be stabilized as non-aromatic/anti-aromatic or Mobius aromatic macrocycles using different strategies such as core-modification of porphyrins, non-metal/metal complexation of porphyrins, peripheral modification of porphyrins and expanded porphyrinoids. The structural properties such as aromaticity of the macrocycle can be controlled by choosing the right synthetic strategy. This review will provide an overview of the development in the chemistry of 20π porphyrinoids giving emphasize on the synthesis, structure and electronic properties of these macrocycles which have huge potential for various applications.

Synthesis of meso-Triaryl 22-Oxanorroles

Norroles are isomers of corroles containing a direct pyrrole N-pyrrole C link instead of a pyrrole C-pyrrole C link of corroles. 22-Oxanorroles are core-modified norroles in which one of the pyrroles is replaced with a furan ring. A straightforward route is adopted to synthesize the first examples of aromatic meso-triaryl-22-oxanorroles containing a pyrrole N-pyrrole α-C direct bond in 4-7% yields by condensing 16-oxatripyrrane and (1H-pyrrol-3-yl)(p-tolyl)methanol in CH₂Cl₂ under mild acid-catalyzed conditions followed by oxidation with DDQ.

Metal Complexes of Porphyrinoids Containing Nonpyrrolic Heterocycles

The replacement of one or more pyrrolic building block(s) of a porphyrin by a nonpyrrolic heterocycle leads to the formation of so-called pyrrole-modified porphyrins (PMPs), porphyrinoids of broad structural variability. The wide range of coordination environments (type, number, charge, and architecture of the donor atoms) that the pyrrole-modified frameworks provide to the central metal ions, the frequent presence of donor atoms at their periphery, and their often observed nonplanarity or conformational flexibility distinguish the complexes of the PMPs clearly from those of the traditional square-planar, dianionic, N₄-coordinating (hydro)porphyrins. Their different coordination properties suggest their utilization in areas beyond which regular metalloporphyrins are suitable. Following a general introduction to the synthetic methodologies available to generate pyrrole-modified porphyrins, their general structure, history, coordination chemistry, and optical properties, this Review highlights the chemical, electronic (optical), and structural differences of specific classes of metalloporphyrinoids containing nonpyrrolic heterocycles. The focus is on macrocycles with similar "tetrapyrrolic" architectures as porphyrins, thusly excluding the majority of expanded porphyrins. We highlight the relevance and application of these metal complexes in biological and technical fields as chemosensors, catalysts, photochemotherapeutics, or imaging agents. This Review provides an introduction to the field of metallo-PMPs as well as a comprehensive snapshot of the current state of the art of their synthesis, structures, and properties. It also aims to provide encouragement for the further study of these intriguing and structurally versatile metalloporphyrinoids.

Oxygen-Varying Correlated Fluorescence for Determining the Stern-Volmer Constant of Porphyrin

The achievement of the Stern-Volmer constant (K_SV) of porphyrin, a parameter to describe the ability of energy transfer to oxygen, enables us to understand and engineer the functionalities of porphyrin. In this study, we propose a new method to obtain K_SV by steady fluorescence based on the population correlation between the excited triplet state (T₁) and the singlet excited state (S₁). Nonlinear fluorescence intensity of porphyrin [hematoporphyrin monomethyl ether (HMME)] as a function of pump power is observed, and this nonlinearity is oxygen-concentration-dependent. These observations originated from the population correlation, where more intense pump power introduces a stronger population correlation. Most importantly, we have found that the oxygen content can influence this correlation via the quenching of T₁ based on its sequent change of fluorescence intensity; K_SV ∼ 28 kPa^-1 can be obtained theoretically for HMME. Our investigation not only offers a promising method of achieving K_SV conveniently by steady fluorescence but also enlightens the advances of regulable fluorescence correlation.

Creation from Confusion and Fusion in the Porphyrin World─The Last Three Decades of N-Confused Porphyrinoid Chemistry

Confusion is a novel concept of isomerism in porphyrin chemistry, delivering a steady stream of new chemistry since the discovery of N-confused porphyrin, a porphyrin mutant, in 1994. These days, the number of confused porphyrinoids is increasing, and confusion and associated fusion are found in various fields such as supramolecular chemistry, materials chemistry, biological chemistry, and catalysts. In this review, the birth and growth of confused porphyrinoids in the last three decades are described.