Porphyrin Molecules Research Articles

Novel Synthesis of [2,3] Naphthaloporphyrins

Polycyclic aromatic hydrocarbons such as tetracene, pentacene and their derivatives have been of immense interest to chemists because of their unique electronic properties such as high charge mobility and semiconductor like properties. Derivatives of various acenes have been used to fabricate OFET devices. Appending such acene moieties to porphyrin molecules at the 2,3 C-C bond of the porphyrin molecule gives rise to pi-extended acenes. The absorbance of such acenes are red-shifted compared to the parent porphyrins because of extended conjugation. Devices containing porphyrin based acenes should also be modulated by light in addition to an electrical impulses, which should help in areas such as signal processing. One of the main problems faced by chemists is to synthesize diversely functionalized [2,3] naphthaloporphyrins, which in turn could be further functionalized to give higher acenes. Towards this goal we introduce a new method to synthesize [2,3] naphthaloporphyrins and their push pull derivatives. Figure 1

Selective-Assembling Hybrid Porphyrin-Silicon Nanowire Field-Effect Transistor (PSNFET) for Photonic Sensor

In this letter, a novel photonic sensor composed of a selective-assembling porphyrin-silicon nanowire field-effect transistor (PSNFET) was proposed and fabricated by the complimentary metal-oxide-semiconductor (CMOS)-compatible technique. By intensively designing the hydrophobic isolation structure in the novel device, selective assembling of a wealth of porphyrin molecules to the surface of the poly-Si nanowire can be achieved, which was verified by the laser confocal fluorescence microscopy, SEM, and AFM. Meanwhile, compared to the control group, the selective-assembling PSNFET shows improved sensitivity to porphyrin assembly itself as well as the photo-electronic detection. Such a device structure provides an innovative scheme for photonic sensitivity enhancement and the possibility for the hybrid sensor integration on silicon.

A Diprotonated Porphyrin as an Electron Mediator in Photoinduced Electron Transfer in Hydrogen-Bonded Supramolecular Assemblies

We have successfully constructed hydrogen-bonded supramolecular assemblies based on a diprotonated saddle-distorted porphyrin (H4DPP2+) and redox-active molecules bearing a carboxylate group, such ...

Porphyrin‑silver nanoparticles hybrids: Synthesis, characterization and antibacterial activity

The preparation of light-activated hybrid antibacterial agent combining the porphyrin molecules, bound to the silver nanoparticles (AgNPs) surface is reported. AgNPs were synthesized by N-methyl-2-pyrrolidone-initiated reduction without additional reducing agents. The chemical structure of protoporphyrin IX was modified with the aim to introduce thiol groups. The size distribution and shape features of AgNPs were checked using TEM and HRTEM microscopies. The introduction of thiol groups into the porphyrin was proved by IR spectroscopy. The AgNPs-porphyrin binding was performed in solution and confirmed by fluorescence quenching, Raman spectroscopy and energy-filtered transmission electron microscopy (EFTEM). The antibacterial tests were performed against S. epidermidis and E. coli upon to LED illumination and in the dark. The synergetic effect of AgNPs and porphyrin as well as light activation of the created antibacterial conjugates were observed.

Cationic Porphyrin-Graphene Oxide Hybrid: Donor-Acceptor Composite for Efficient Photoinduced Electron Transfer.

Non-covalent nanohybrids composed of cationic 5,10,15,20-tetra(4-trimethylammoniophenyl)porphyrin tetra(p-toluenesulfonate) (TMAP) and the graphene oxide sheets were prepared under two pH values (6.2 vs. 1.8). The TMAP molecule was positively charged, regardless of the pH value during preparation. However, protonation of the imino nitrogens increased the overall charge of the porphyrin molecule from +4 to +6 (TMAP4+ and TMAP6+ ). It was found that at acidic pH, interaction of TMAP6+ with GO was largely suppressed. On the other hand, results of FTIR, Raman spectroscopy, thermogravimetric analysis, atomic force microscopy (AFM) and elemental analysis confirmed effective non-covalent functionalization of graphene oxide with cationic porphyrin at pH 6.2. The TMAP4+ -GO hybrids exhibited well defined structure with a monolayer of TMAP4+ on the GO sheets as confirmed by AFM. Formation of the ground-state TMAP4+ -GO complex in solution was monitored by the red-shift of the porphyrin Soret absorption band. This ground-state interaction between TMAP4+ and GO is responsible for the static quenching of the porphyrin emission. Fluorescence was not detected for the nanohybrid which indicated that a very fast deactivation process had to take place. Ultrafast time-resolved transient absorption spectroscopy clearly demonstrated the occurrence of electron transfer from the photoexcited TMAP4+ singlet state to GO sheets, as proven by the formation of a porphyrin radical cation.

Temperature Dependence of Photoluminescence for Spin-Coated Semiconductor Quantum Dots and Quantum Dot-Dye Nanoassemblies on Quartz Substrate

The attachment of pyridyl substituted porphyrin molecule to the surface of CdSe/ZnS quantum dots in solutions is realized in the competition with capping ligand TOPO molecules resulting in the specific change of photoluminescence for the quantum dots across the temperature range of 77–290[Formula: see text]K. We have shown that fixation of alone quantum dots or quantum dot-porphyrin nanoassemblies on quartz substrate changes significantly temperature dependence of photoluminescence. In contrast to the samples in a glass-forming solution no phase transition of the TOPO capping layer was observed upon removal of the capping layer.

Bilayer Adsorption of Porphyrin Molecules Substituted with Carboxylic Acid atop the NN4A Network Revealed by STM and DFT.

Bottom-up technology is a bridge connecting a two-dimensional (2D) monolayer structure with a three-dimensional (3D) bulk structure. From 2D to 3D, it helps us to understand the driving force of an organization process to control the molecular arrangement in the 3D phase. Here, we aimed at the fabrication of multilayer nanostructures on solid substrates. Bis(3,5-diacidic)diazobenzene (NN4A) was chosen as one molecule because of its photosensitive azo group and carboxylic group possessing hydrogen bonding effect, while porphyrin molecules composed of different numbers and positions of carboxylic acid groups were used as the other component. It was found that the porphyrin molecules could adopt different adsorption configurations because of the influence of carboxylic groups, leading to different subsequent coassemblies on the solid surface. The NN4A/porphyrin systems underwent structural transformation when NN4A molecules were adsorbed on the highly oriented pyrolytic graphite surface with predeposited porphyrin. This work displayed an efficient method on the construction of multilayer nanostructures in the molecular surface engineering and provided a new way to construct 3D structures based on the molecular design.

Formation of Nanostructure-controlled Strong Coupling of Porphyrin Molecules and Silver Nanoparticles Using Layered Silicates

The nanostructure control of strong coupling has been less thoroughly investigated in organic semiconductor structures than in resonator structures. We achieved strong coupling by introducing a lay...

Enzymatic Micromotors as a Mobile Photosensitizer Platform for Highly Efficient On‐Chip Targeted Antibacteria Photodynamic Therapy

AbstractPhotodynamic therapy (PDT) functions when the light‐excited photosensitizers transfer energy to oxygen molecules (3O2) to produce cytotoxic singlet oxygen (1O2) that can effectively kill cells or bacteria. However, the PDT efficacy is often reduced by the limited availability of 3O2 surrounding the photosensitizer and extremely short diffusion range of the photoactivated 1O2. Herein, an enzymatic micromotor based on hollow mesoporous SiO2 (mSiO2) microspheres is constructed as a mobile and highly efficient photosensitizer platform. Carboxylated magnetic nanoparticles are connected with both hollow spheres and 5,10,15,20‐tetrakis(4‐aminophenyl)porphyrin molecules through covalent linkage between amino and carboxylic groups within a one‐step reaction. Due to the intrinsic asymmetry of the mSiO2 spheres, the micromotors can be propelled by ionic diffusiophoresis induced by the enzymatic decomposition of urea. Via numerical simulation, the self‐propulsion mechanism is clarified and the movement direction is identified. By virtue of active self‐propulsion, the current system can overcome the long‐standing shortcomings of PDT and significantly enhance the PDT efficacy by improving the accessibility of the photosensitizer to 3O2 and enlarging the diffusing range of 1O2. Therefore, by proposing a new solution to the bottleneck problems of PDT, this work provides insightful perspectives to the biomedical application of multifunctional micro/nanomotors.

Constructing Artificial Light-Harvesting Systems by Covalent Alignment of Aggregation-Induced Emission Molecules.

The characteristics of chloroplasts harvesting solar energy and conducting energy transfer have inspired chemists to mimic similar processes. However, accurate manipulation to gain regularly displayed antenna chromophores in mimicking chloroplasts is a great challenge. Herein, a rational design is presented that combines orderly arranged chromophores with aggregation-induced emission (AIE) to develop artificial light-harvesting systems. Tetraphenyl ethylene (TPE) molecules, which exhibited strong AIE properties, are considered as building blocks to fabricate high emissive 2D nanosheets and nanovesicles, respectively. Furthermore, the well-aligned TPE molecules are also developed as donor chromophores in light-harvesting processes. After subsequent surface modification by porphyrin molecules as acceptor chromophores, an efficient light-harvesting system has been integrally constructed. This study demonstrates a novel strategy to utilize AIE feature to mimic chloroplasts process in nature.

Covalently Grafting Cobalt Porphyrin onto Carbon Nanotubes for Efficient CO2 Electroreduction

AbstractMolecular complexes with inexpensive transition‐metal centers have drawn extensive attention, as they show a high selectivity in the electrochemical conversion of CO2 to CO. In this work, we propose a new strategy to covalently graft cobalt porphyrin onto the surface of a carbon nanotube by a substitution reaction at the metal center. Material characterization and electrochemical studies reveal that the porphyrin molecules are well dispersed at a high loading of 10 wt. %. As a result, the turnover frequency for CO formation is improved by a factor of three compared to traditional physically‐mixed catalysts with the same cobalt content. This leads to an outstanding overall current density of 25.1 mA cm−2 and a Faradaic efficiency of 98.3 % at 490 mV overpotential with excellent long‐term stability. This work provides an effective pathway for the improvement of the performance of electrocatalysts that could inspire rational design of molecular catalysts in the future.

Supramolecular Complexes of Graphene Oxide with Porphyrins: An Interplay between Electronic and Magnetic Properties

Graphene oxide (GO) was modified by two modified porphyrins (THPP and TCPP) to form GO–porphyrin hybrids. Spectroscopic measurements demonstrated the formation of stable supramolecular aggregates when mixing two components in solution. The Fourier transform infrared (FTIR) and Raman scattering measurements confirm π-stacking between hydrophobic regions of GO nanoflakes and porphyrin molecules. On the number and the kind of paramagnetic centers generated in pristine GO samples, which originate from spin anomalies at the edges of aromatic domains within GO nanoflakes. More significant changes in electronic properties have been observed in hybrid materials. This is particularly evident in the drastic increase in the number of unpaired electrons for the THPP-GO sample and the decrease in the number of unpaired electrons for the TCPP-GO. The difference of paramagnetic properties of hybrid materials is a consequence of π-stacking between GO and porphyrin rings. An interesting interplay between modifiers and the surface of GO leads to a significant change in electronic structure and magnetic properties of the designed hybrid materials. Based on the selection of molecular counterpart we can affect the behavior of hybrids upon light irradiation in a different manner, which may be useful for the applications in photovoltaics, optoelectronics, and spintronics.

Covalently Grafting Cobalt Porphyrin onto Carbon Nanotubes for Efficient CO2 Electroreduction

Molecular complexes with inexpensive transition-metal centers have drawn extensive attention, as they show a high selectivity in the electrochemical conversion of CO2 to CO. In this work, we propose a new strategy to covalently graft cobalt porphyrin onto the surface of a carbon nanotube by a substitution reaction at the metal center. Material characterization and electrochemical studies reveal that the porphyrin molecules are well dispersed at a high loading of 10 wt. %. As a result, the turnover frequency for CO formation is improved by a factor of three compared to traditional physically-mixed catalysts with the same cobalt content. This leads to an outstanding overall current density of 25.1 mA cm-2 and a Faradaic efficiency of 98.3 % at 490 mV overpotential with excellent long-term stability. This work provides an effective pathway for the improvement of the performance of electrocatalysts that could inspire rational design of molecular catalysts in the future.

Pathways for Improving the Photovoltaic Efficiency of Porphyrin and Phosphorene Antidot Lattice Nanocomposites: An Insight from a Theoretical Study

The porosity of a newly synthesized phosphorene antidot lattice (PAL) is promising for encapsulating the porphyrin molecule and thus shows a versatile route to fabricate porphyrin/PAL nanocomposite...

Surface decorating of CH3NH3PbBr3 nanoparticles with chemically adsorbed porphyrin

An organolead halide (CH3NH3PbBr3) nanoparticle was modified successfully with a porphyrin (POR) bearing an -NH3+ head group. The nanoparticles are homogeneous with high crystallinity. The photoluminescence of CH3NH3PbBr3 is quenched completely by the chemically adsorbed POR molecules. The efficient energy transfer from CH3NH3PbBr3 to POR is responsible for the fluorescence quenching. The modified nanoparticles can be dispersed in organic solvents and the resulting dispersion remains stable for several days. This result provides a new way to tune the photophysical properties of organolead halide CH3NH3PbBr3 nanoparticles.

Photoreactions of Macrocyclic Dyes on (1010) Wurtzite Surface – Interplay Between Conformation and Electronic Effects

Macrocyclic dyes such as phthalocyanine and porphyrin molecules are modeled on (1010) wurzite surfaces using the DFT and molecular dynamics approaches. It is found that the single dye anchored on the wurtzite surface stabilizes in an inclined geometry with its core facing the surface at a tilting angle of ca 60∘. The tilting of the dye relative to the crystal surface has a dual effect on the charge transfer from a chromophore to the semiconductor. Increasing the tilting angle leads to a stronger coupling between the lowest level of the semiconductor conduction band and dye’s LUMO, thus raising the tunneling probability of the electron injection. By contrast, the electrostatic interaction between units upon the tilting of macrocycles results in a lowering of the molecule LUMO level with respect to the conduction band minimum of the wurzite crystal, which may hinder the electron transfer. The type of a linker and peripheral substituents significantly affect the mutual conformation of the moieties, and their proper choice can facilitate the photoinduced charge transfer reactions.

Facile Synthesis and Self‐Assembly of Zinc (2‐Diethoxyphosphorylethynyl)porphyrins

The synthesis of zinc (2‐diethoxyphosphorylethynyl)porphyrins and their self‐organization in solid state and in solution are reported. Copper‐cocatalyzed Sonogashira reaction involving bromoporphyrins and diethyl ethynylphosphonate was used to prepare meso‐substituted derivatives Zn4 and Zn5 bearing one or two ethynylphosphonate substituents at the macrocycle. In contrast, copper‐free Sonogashira coupling of 2‐bromoporphyrin with diethyl ethynylphosphonate is more convenient to prepare porphyrin Zn6 bearing this substituent at the β‐pyrrolic position of the macrocycle. The structures of complexes Zn4a·C7H8, Zn4a·CHCl3, Zn4c and Zn5b·CH2Cl2 in crystals were elucidated by X‐ray diffraction analysis. The supramolecular self‐assembly through weak coordinative binding of the phosphoryl group of one porphyrin molecule to the zinc(II) ion located in the center of another macrocyclic cavity is observed in all crystals. However, ZnII‐porphyrinates Zn4a and Zn5b exist in the solid state as mutually coordinated dimers while complex Zn4c displays a 1D polymer structure. In all dimer complexes, neighboring porphyrin rings are spatially separated, with Zn–O and P=O bond lengths being similar, while the interplanar porphyrin distance is variable, depending on weak intermolecular interactions in the crystals. The self‐organization of (phosphorylethynyl)porphyrins is also observed in weakly polar chloroform and detectable by NMR and UV/Vis spectroscopy. The mutually coordinated dimer of electron‐deficient porphyrin Zn5b was observed in 5 × 10–3 m chloroform solution even at room temperature. The kinetic lability of this supramolecular complex was proven by NMR spectroscopy. The associates of more electron‐donating porphyrins Zn4a and Zn4c are less stable, and self‐assembled dimers become the predominant species in 5 × 10–3 m chloroform solution only below 225 K. The self‐assembly of porphyrin Zn4a and Zn5b in more diluted solutions (up to 10–6 m) was also investigated by UV/Vis spectroscopy.

Theoretical study of novel porphyrin D-π-A conjugated organic dye sensitizer in solar cells

In this study, the characteristic of the designed porphyrin sensitizer was studied by density functional theory (DFT) and time-dependent density functional theory (TDDFT). D-π-A sequence of seven donor-acceptor dyes A-F in the organic dye-sensitized solar cell (DSSCs) was analyzed. Firstly, the structure and frequency of porphyrin dyestuffs with different substituents were optimized by DFT method, and the structure and properties of the ground state of porphyrin dyes were studied by comparing the energy differences of different orbitals. Then, the TDDFT method was used to study the porphyrin molecules with different π bridge. The structure and properties of the excited state are discussed in terms of the energy and charge separation state of the molecular orbital of the porphyrin sensitizer. According to the absorption spectrum, the characteristic of the light absorption for the sensitizer molecule is investigated. The results shown that the key characteristic parameters closely related to the open circuit photovoltage (VOC) and the short circuit current density (JSC) of the porphyrin sensitizers helped to clarify different π bridges. The change of VOC and JSC affected the energy level change of the porphyrin sensitizers with different π bridge. Finally, a suitable π bridge was selected as a porphyrin sensitizer candidate with higher conversion efficiency.

Insight into conformationally-dependent binding of 1-n-alkyl-3-methylimidazolium cations to porphyrin molecules using quantum mechanical calculations.

The first step in the biodegradation of imidazolium-based ionic liquids involves the insertion of the -OH group into the alkyl side chain, and it is believed to be triggered by cytochrome P450. However, at present, there is a lack of fundamental understanding of why the hydroxylation process is observed only for longer alkyl chain analogues. As the initial step of the hydroxylation reaction involves the ionic liquid binding to Fe-porphyrin (FeP) - the catalytic center of cytochrome P450, the orientation of ionic liquids presented to FeP is expected to play a crucial role in eventual hydroxylation of the alkyl side chain. In order to elucidate the chain-length dependent binding preferences exhibited by the homologous series of 1-n-alkyl-3-methylimidazolium (n = 2, 4, 6, 8, and 10) [Cnmim]+ cations, a quantum mechanical treatment of the cations in the presence of free base porphyrin (FBP) and FeP is carried out at the B3LYP-D2 and M06 levels. The binding energy of different complexes with FBP and FeP is investigated by considering three vastly different starting relative orientations of the cations with respect to FBP and FeP: tail down, tail up, and interplanar. Our calculations of binding energies reveal that the cation orientations initiated from the tail down conformations (alkyl chain facing the porphyrin molecules) are progressively destabilized as the alkyl chain length increases. The decomposition of the binding energies into various energetic contributions shows that the interaction energy between the cations and porphyrin molecules varies with the cation geometries presented to porphyrin molecules and is the primary determinant of the magnitude of the binding energies. We further demonstrate that the propensity of the cation-FeP complexes to acquire an electron, the next step in the hydroxylation reaction cycle upon substrate binding, is favored independent of the cations and conformations, suggesting that this step is not the reason for the low biodegradability of short alkyl chain bearing cations. Furthermore, the weaker binding of the ionic liquid to FeP is anticipated to facilitate dioxygen binding to FeP, the step following the electron transfer reaction. Overall, the results of the present calculations indicate that the destabilization of the tail down conformations relative to the other two conformations correlates with the experimental results of the chain length-dependent biodegradation of imidazolium-based ionic liquids.

Supramolecular chirogenesis in zinc porphyrins by enantiopure hemicucurbit[n]urils (n = 6, 8).

Chiral cyclohexanohemicucurbit[n]urils (n = 6, 8) (cycHCs) are able to bind guests through multiple "outer surface interactions", which in the case of planar zinc porphyrins leads to induction of chirality. Crystal structures of complexes of complementary sized hosts revealed social self-sorting, while in the solution phase one cycHC can accommodate up to three porphyrin molecules with log Ktotal 9.