Characterization Of Porphyrins Research Articles

Synthesis, characterization of porphyrin and CdS modified spherical shaped SiO2 for Reactive Red 120 degradation under direct sunlight

Initially, sphere shaped SiO2 was explored by adopting simple sol-gel method without any template. Later, the sphere like SiO2 was modified with cadmium sulfide (CdS) semiconductor and porphyrins. The formation of composites (CdS/SiO2-porphyrins) brought out by diverse characterization techniques that include XRD, Raman, FT-IR, FE-SEM, EDS, DRS and PL measurements. The photocatalytic activity of CdS/SiO2 was slightly influenced by porphyrins such as meso-tetra-phenyl-porphyrin (TPP) and 5,10,15,20-meso-tetra-(para-amino)-phenyl-porphyrin (TPAPP). The mechanism which has been proposed for Reactive Red 120 (RR 120) degradation by CdS/SiO2- porphyrins under sunlight.

Synthesis and Computational Study of Pentacenequinone-Fused Porphyrins with Triply-Split Soret Bands

Porphyrins are one of nature’s most prolific aromatic macrocycles and are one of the most important components of light harvesting in green plants. In pursuit of organic dyes with applications in artificial photosynthesis, porphyrins with broadened and red-shifted UV-Vis spectra are of interest in optimizing the energy obtained from the solar spectrum. Extension of the conjugation of porphyrins through fused rings to the β-positions of the porphyrin induces red-shifted and broadened UV-Visible absorption spectra, but synthesis and characterization of porphyrins with triply-split Soret bands with potential to further enhance the capture of the solar spectrum are unexplored. Herein there is report of synthesis, crystal structure, and computational study of cross-conjugated β-extended pentacenequinone-fused porphyrins with triply-split Soret bands, which to the best of our knowledge are the first to exhibit such Soret bands. These molecules’ experimental UV-Vis spectrum is compared to computationally derived UV-Vis spectra, and magnetic circular dichroism (MCD) is used to elucidate the electronic transitions that give rise to the triply-split Soret band. Figure 1

XPS Characterization of Porphyrin Based Self-Assembled Monolayers on Gold

XPS characterization of self-assembled monolayers (SAMs) of tetraphenylporphyrin bearing a rigid tripodal linker by chemisorption of the thiol-derivatized terminal groups on gold substrate is described. The surface structure of the SAMs bearing tripodal linker were analyzed by X-ray photoelectron spectroscopy (XPS), and electrochemical cyclic voltammetry (CV) measurements. XPS confirms the formation of porphyrin SAMs on Au surface and identified bonding configurations of porphyrin molecules in the chemisorption of SAMs. The film thickness values (36 Å) obtained by XPS agree well with the estimated value by assuming the vertical orientation of the molecules on the gold surface. Using the Au4f7/2 as an internal standard, a lower binding energies shift (1.8 eV) of S2p in the SAMs reveals that the porphyrins were chemisorbed onto the surface via sulfurgold bonds. Electrochemical CV measurements suggest near monolayer coverage of the tripodal porphyrins with good stability of the redox SAMs, which have promising application in the development of molecular based electronic device and memory architectures.

Synthesis and characterization of porphyrin nanotubes/rods for solar radiation harvesting and solar cells

Energy transfer and electron transfer events as they occur between well arranged light harvesting antenna molecules, the reaction center and other factors determine the function of natural photosynthesis. The overall small reorganization energy and the well-balanced electronic coupling between each component bear key characters for the unique efficiency of natural photosynthesis. Such aspects permit the design and assembly of artificial systems that efficiently process solar energy, replicating the natural processes. The rich and extensive transitions seen in porphyrin-based materials hold great expectation as light harvesting building blocks in the construction of molecular architectures, allowing an efficient use of the solar spectrum. Hence in this study porphyrin nanorods are synthesized and characterized for future application in the construction of the artificial light harvesting system. Understanding the sizes and growth mechanism of porphyrins nanorods by self-assembly and molecular recognition is essential for their successful implementation in nanodevices. Spectroscopic and microscopic studies were carried out to investigate the effect that time, concentration and solvents have on the fabrication of porphyrin nanorods by ionic self-assembly of two oppositely charged porphyrins. We investigate in details the heteroaggregate behavior formation of [H4TPPS4]2− and [SnTPyP]2+ mixture by means of the UV–vis spectroscopy and aggregates structure and morphology by transmission electron microscopy (TEM). This study demonstrates the potential for using different concentrations and solvents to influence the physical and optical properties of porphyrin based nanorods.

Highly tunable metal–organic frameworks with open metal centers

We report the synthesis and characterization of porphyrin containing metal–organic frameworks that show high metal tunability without altering the framework topology.

Characterization of Porphyrins, Chlorins, and Bacteriochlorins Formed via Allomerization of Bacteriochlorophylla. Synthesis of Highly Stable Bacteriopurpurinimides and Their Metal Complexes

Allomerization of bacteriochlorophyll a (Bchl a) was studied under various reaction conditions. Bchl a on stirring with KOH/propanol produced an "unstable bacteriochlorin", which decomposed in acidic conditions to give a complex mixture containing bacteriopurpurin a as a principal component. The yields of other compounds varied and were found to be dependent on reaction condition. The structures of the isolated porphyrins, chlorins, and bacteriochlorins, related to Bchl a, were assigned on the basis of 1D, 2D NMR (ROESY), and mass spectroscopy analyses. The presence of fused anhydride rings in porphyrin, chlorin, and bacterichlorin systems showed a significant influence on their optical properties. Compared to bacteriochlorophyll a and bacteriopheophytin, the related structurally modified analogues, e.g., the bacteriopurpurin a, 13(1)/15(1)-N-alkyl isoimide, and the imide analogues were found to be more stable with a significant difference in spectroscopic properties. Bacteriochlorins containing anhydride, imide, or isoimide cyclic rings demonstrated a significant bathochromic shift of their Q bands in their electronic absorption spectra. Under basic conditions the formation of the 12-hydroxymethyl, 12-formyl, and 12-methylene analogues as byproducts from the 12-methyl-bacteriopurpurin-N-hexylimide could be due to subsequent oxidation of the vinylogous enolate intermediates. To investigate the effect of the central metal in the electronic spectra, the stable bacteriopurpurin-18-N-hexylimide was converted to a series of metal complexes [Zn(II), Cd(II), and Pd(II)] by following the direct or transmetalation approaches. Compared to the free-base analogue, these complexes showed a remarkable shift in their electronic absorption spectra.

Syntheses and characterization of porphyrins and their zinc complexes appending a multi-dentate ligand

Porphyrins with a multi-dentate ligand have been prepared by a covalent binding of nitrilotriacetic acid (NTA) to meso-mono ( ortho- or para-aminophenyl)-triphenylporphyrin. The equilibrium between the porphyrins and Zn 2+ has been analyzed by ultra violet–visible (UV–Vis) and 1H NMR spectroscopies and the porphyrins are found to form complexes with porphyrin/zinc ratios of 1:1 and 1:2. The zinc complexes with the porphyrin/zinc ratios of 1:1 and 1:2 have been prepared and characterized by UV–Vis, infrared (IR) and 1H NMR spectroscopies. An accelerated zinc incorporation reaction into the porphyrin appending NTA at its ortho-phenyl group is reported.

Preparation and Characterization of Porphyrin c Analogs as Agents for Photodynamic Therapy

The porphyrin c analogues (4)-(10) were prepared by reaction of the appropriate thiol with the dibromohematoporphyrin adduct (3). The porphyrins were obtained in high yield and purity and were characterized by 1H and 13C n.m.r. spectroscopy and f.a.b. mass spectrometry.

High-temperature GC/MS characterization of porphyrins and high molecular weight saturated hydrocarbons

Determination of the exact structure and relative concentrations of metalloporphyrins and high molecular weight cyclic and acyclic hydrocarbon is of importance since these are useful «biomarkers» in petroleum exploration. Description of the recent efforts in high-temperature gas chromatography /electron impact mass spectrometry (GC/EIMS) and gas chromatography/field ionisation mass spectrometry (GC/FIMS) analysis of these relatively high molecular weight components in petroleum and petroleum sediments