Porphyrin

Tetra (4-carboxyphenyl) porphyrin (TCPP) was loaded on the surface of Pt/g-C3N4 via a simple adsorption process, and the microstructure and chemical structure of the composites were characterized by high resolution transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, UV-visible diffused reflectance spectroscopy and photoluminescence spectroscopy. Loading TCPP onto Pt/g-C3N4 enhanced the visible-light-driven photocatalytic evolution of H2 from water...

The quantum efficiency or the rate of conversion of incident photon to free electron in photosynthesis is known to be extremely high. It has long been thought that the origin of this efficiency are molecular vibrations leading to a very fast separation of electrons and holes within the involved molecules. However, molecular vibrations are commonly in the range above 100 meV, which is too high for excitations in an ambient environment. Here, we analyze experimental spectra of single organic molecules on metal surfaces at ~ 4 K, which often exhibit a pronounced dip...

In this study, a new type of functional, self-assembled nanostructure formed from porphyrins and polyamidoamine dendrimers based on hydrogen bonding in an aqueous solution is presented. As the aggregates formed are promising candidates for solar-energy conversion, their photocatalytic activity is tested using the model reaction of methyl viologen reduction. The self-assembled structures show significantly increased activity as compared to unassociated porphyrins. Details of interaction forces driving the supramolecular structure formation and regulating catalytic efficiency are fundamentally discussed...

Improving molecular catalysis for important electrochemical PCET reactions, such as the interconversions of H+/H2, O2/H2O, CO2/CO, and N2/NH3, is an ongoing challenge. Synthetic modifications to the molecular catalysts are valuable but often show trade-offs between turnover frequency (TOF) and the effective overpotential required to initiate catalysis (eff). Herein, we derive a new approach for improving efficiencies - higher TOF at lower eff - by changing the concentrations and properties of the reactants and products, rather than by modifying the catalyst...

An enzyme mimic harboring iron porphyrin (DhHP-6) embedded in zeolite imidazolate framework-8 (ZIF-8) was constructed through biomimetic mineralization approach to obtain the composite DhHP-6@ZIF-8. The composite was then used as catalyst in the ATRP of poly(ethylene glycol) methyl ether methacrylate (PEGMA500) in which poly(PEGMA500) could be synthesized with monomer conversion of 76.1% and Mn of 45,900 g/mol, stronger than free DhHP-6 as catalyst. More importantly, it could efficiently overcome the drawbacks of free DhHP-6 and achieve the easy separation of DhHP-6 from the catalytic system and the elimination of iron residues in the synthesized polymer...

A hydroxamic acid group has been employed for the first time as an anchoring group for cobalt-based dye-sensitized solar cells (DSSCs). The porphyrin dye YD2-o-C8HA with the hydroxamic acid anchoring group exhibited a power conversion efficiency (η) of 6.4%, which is close to that of YD2-o-C8, a representative porphyrin dye with a conventional carboxylic acid one. More importantly, YD2-o-C8HA was found to be superior to YD2-o-C8 in terms of both binding ability to TiO2 and durability of cobalt-based DSSCs...

We report a general anion sensing platform based on a portable and cost-effective ion-selective optode and a smartphone detector equipped with a color analysis app. In contrast to traditional anion-selective optodes using a hydrophobic polymer and/or plasticizer to dissolve hydrophobic sensing elements, the new optode relies on hydrophilic cellulose paper. The anion ionophore and a lipophilic pH indicator are inkjet-printed and adsorbed on paper and form a "dry" hydrophobic sensing layer. Porous cellulose sheets also allow the sensing site to be modified with dried buffer that prevents any sample pH dependence of the observed color change...

Metal-organic frameworks (MOFs) are ideal precursors/ templates for porous carbons with homogeneous doping of active components for energy storage and conversion applications. Herein, metalloporphyrinic MOFs, PCN-224-FeCo, with adjustable molar ratio of Fe(II) /Co(II) alternatively residing inside the porphyrin center, were employed as precursors to afford FeCo-N-doped porous carbon (denoted as FeCo-NPC) by pyrolysis. Thanks to the hollow porous structure, the synergetic effect between highly dispersed FeNx and CoNx active sites accompanied with a high degree of graphitization, the optimized FeCo2 -NPC-900 obtained by pyrolysis at 900 °C exhibits more positive half-wave potential, higher diffusion-limited current density, and better stability than the state-of-the-art Pt/C, under both alkaline and acidic media...

The main aim of nanotechnology is to create functional systems by controlling the matter at the nanometer level. In this context DNA is a versatile building block for the fabrication of micrometer-scale objects with a subnanometer-scale resolution. Over the last 15 years, DNA nanotechnology has considerably developed with the invention of DNA origami, double crossover structures and molecule/oligonucleotide hybrids. Our interest is focused on the combination of short complementary DNA sequences with organic molecules with a view to create large self-assembled nanostructures...

An off-axis supramolecular rotor was composed of four components: a zinc-porphyrin based stator with four phenanthroline stations and a zinc-salphen based rotator were self-assembled with DABCO and four copper(i) ions to furnish the rotor ROT-2 in quantitative yield. The DABCO serves as a connecting axle between the rotator and the stator, while the rotator is additionally connected to two copper(i)-loaded phenanthroline stations of the stator via its two pyridine terminals (Npy → [Cu(phen)](+)). For the thermally activated rotation both Npy → [Cu(phen)](+) interactions have to be cleaved...

Graphene-based materials (GBMs), with graphene, their most known member, at the head, constitute a large family of materials which has aroused the interest of scientists working in different research fields such as chemistry, physics, or materials science, to mention a few, arguably as no other material before. In this review, we offer a general overview on the most relevant synthetic approaches for the covalent and non-covalent functionalization and characterization of GBMs. Moreover, some representative examples of the incorporation into GBMs of electroactive units such as porphyrins, phthalocyanines, or ferrocene, among others, affording electron donor-acceptor (D-A) hybrids are presented...

A novel supramolecular miktoarm star polymer was successfully constructed in water from a pyridine end-decorated polymer (Py-PmDEGA) and a metalloporphyrin based star polymer (ZnTPP-(PEG)4) via metal-ligand coordination. The Py-PmDEGA moiety was prepared via a combination of reversible addition-fragmentation chain transfer polymerization (RAFT) and subsequent aminolysis and Michael addition reactions to introduce the pyridine end-group. The ZnTPP(PEG)4 star-polymer was synthesized by the reaction between tetrakis(p-hydroxyphenyl)porphyrin and toluenesulfonyl-PEG, followed by insertion of a zinc ion into the porphyrin core...

Recent advances in the engineering of picoscale gaps between electroburnt graphene electrodes provide new opportunities for studying electron transport through electrostatically gated single molecules. But first we need to understand and develop strategies for anchoring single molecules to such electrodes. Here, for the first time we present a systematic theoretical study of transport properties using four different modes of anchoring zinc-porphyrin monomer, dimer, and trimer molecular wires to graphene electrodes...

Advances in photodynamic therapy of cancer have been restrained by lack of cancer specificity and side effects to normal tissues. Molecularly targeted photodynamic therapy can achieve higher cancer specificity by combination of active cancer targeting and localized laser activation. We aimed to use albumin as a carrier to prepare targeted nanoconjugates that are selective to cancer cells and smaller than conventional nanoparticles for superior tumor penetration. IRDye® 700DX (IR700), a porphyrin photosensitizer, was covalently conjugated to human serum albumin that was also linked with tumor-targeting RGD peptides...

We report here a highly facile one-pot synthesis of a new series of fully π-conjugated unsymmetric chlorin-porphyrin heterodimers with quantitative yields by utilizing intermacrocyclic interactions. One-electron oxidations of dicopper(II) and dipalladium(II) porphyrin dimers using mild oxidants such as iodine at room temperature resulted in the formation of a strongly interacting cofacial mixed-valent π-cation radical dimers. The radical being highly reactive drives spontaneous and rapid transformation involving a new N=C bond formation, 1,2-ethyl migration and the generation of a new indolizinium ring that bridges between the two macrocycles...

A strategy assisted by an inorganic template was developed to promote the organized self-assembly of meso-(tetrakis)-(p-sulfonatophenyl)porphyrin (TSPP) on pH sensitive core-shell polyelectrolyte microcapsules (PECs) of poly(styrene sulfonate) (PSS) and poly(allylamine hydrochloride) (PAH). A key feature of this strategy is the use of template CaCO3 microparticles as a nucleation site endorsing inside-outside directional growth of porphyrin aggregates. Using this approach, TSPP self-assembly in positively charged PECs with CaCO3 (PAH/PSS)2PAH as a sequence of layers was successfully achieved using pH mild conditions (pH 3)...

DNA polymorphism exerts a fascination on a large scientific community. Without crystallographic structural data, clarification of the binding modes between G-quadruplex (G4) and ligand (complex) is a challenging job. In the present work, three porphyrin compounds with different flexible carbon chains (arms) were designed, synthesized and characterized. Their binding, folding and stabilizing abilities to human telomeric G4 DNA structures were comparatively researched. Positive charges at the end of the flexible carbon chains seem to be favorable for the DNA-porphyrin interactions, which were evidenced by the spectral results and further confirmed by the molecular docking calculations...

Polyethyleneimine (PEI) has long been considered as "golden standard" for polymeric gene delivery carriers. However the molecular basis of the cytotoxicity of PEI is poorly understood. Little is known about the effects of PEI on the structure and functions of biomacromolecules. In this work, fluorescence, UV-vis absorption, circular dichroism spectroscopy were conducted to investigate the influence of PEI of average molecular weight 25, 10 and 1.8kDa (denoted as PEI25k, PEI10k and PEI1.8k) on the conformation of horseradish peroxidase (HRP) and its catalytic efficiency...

The synthesis of a porphyrin rotaxane by dipolar cycloaddition takes advantage of the ditopic character of a phenanthroline-strapped porphyrin. The success of the click reaction was conditioned by the presence of both a coordinatively unsaturated metal in the porphyrin and a copper(I) bound to the phenanthroline, pointing at a new "tandem active metal template" mechanism.

The spin Hamiltonian (SH) parameters experimentally determined by EMR (EPR) may be corroborated or otherwise using various theoretical modeling approaches. To this end semiempirical modeling is carried out for high-spin (S=2) manganese (III) 3d(4) ions in complex of tetraphenylporphyrinato manganese (III) chloride (MnTPPCl). This modeling utilizes the microscopic spin Hamiltonians (MSH) approach developed for the 3d(4) and 3d(6) ions with spin S=2 at orthorhombic and tetragonal symmetry sites in crystals, which exhibit an orbital singlet ground state...