Tetraphenylporphyrin Complexes Research Articles

Near-infrared luminescent Sn(IV) complexes of N-confused tetraphenylporphyrin: Effect of axial anion coordination

Novel tin(IV) halo complexes of an N-confused tetraphenylporphyrin with different axial ligands have been synthesized and characterized by various spectroscopic methods including X-ray crystallographic analysis. The molecular structures of the dichloro and dibromo derivatives possess perfect octahedral geometries, which are nearly comparable to the corresponding regular porphyrin complexes. In contrast, the iodide/triiodide complex obtained by a same reaction manner, demonstrated that the tin(IV) cation is slightly displaced towards axially coordinated iodide anion, giving rise to the different electronic structure due to the tautomeric form of N-confused porphyrin ligand. These structural differences reflected to the distinct photophysical and electrochemical properties. The Sn(IV) complexes are near IR luminescent, however the unsymmetrical axial coordination of iodide and triiodide anions in the tin(IV) N-confused porphyrin complex allows, in particular, the longer emission lifetimes and a smaller singlet-triplet energy gap, which were investigated by steady-state and time-resolved spectroscopies as well as theoretical calculations.

Photocatalytic Oxidation of 2-Mercaptoethanol to Disulfide using Sb(V)-, P(V)-, and Ge(IV)-porphyrin Complexes

Visible-light irradiation of MeCN solution containing di(hydroxo)metallo(tetraphenyl)porphyrin complex <TEX>$(tppM(OH)_2$</TEX>: 1a; <TEX>$M=Sb(V)^+Br^-$</TEX>, 1b; <TEX>$M=P(V)^+Cl^-$</TEX>, 1c; M=Ge(IV)) and 2-mercaptoethanol (2-ME) as a substrate under aerated condition gave bis(2-hydroxyethyl)disulfide (2-HEDS) as an oxidative product of 2-ME. It is indicated that the oxidation of 2-ME should proceed with a photocatalytic process by 1, because the turn over number (TON) for the formation of 2-HEDS was over unit. The TON was determined to be 642 as a maximum value when 1a was used as a sensitizer. The formation of 2-HDES was extremely slow under argon atmosphere. The fluorescence of 1 was not quenched by 2-ME at all, and the free energy change (<TEX>${\Delta}G$</TEX>) with electron transfer (ET) from 2-ME to excited triplet state of <TEX>$1(^31^*)$</TEX> was estimated as a negative value. The quenching rate constant (<TEX>$k_r$</TEX>) of <TEX>$^31^*$</TEX> by 2-ME, obtained by the kinetics for the formation of 2-HEDS, strongly depends on <TEX>${\Delta}G$</TEX>. These findings indicate that 1-sensitized oxidation was initiated by photoinduced ET from 2-ME to <TEX>$^31^*$</TEX> to generate both radical cation of 2-ME (<TEX>$2-ME^{+\bulle}$</TEX>) and porphyrin radical anion (<TEX>$1^{-\bulle}$</TEX>), resulting that the formation of 2-HEDS can be proceeded by the dimerization of <TEX>$2-ME^{+\bulle}$</TEX>, and through a catalytic cycle due to returning to 1 by the ET from <TEX>$1^{-\bulle}$</TEX> to molecular oxygen.

Electrochemical charactreistics of membranes based on Mn(III) tetraphenylporphyrin

Anion-selective electrodes with polymer membranes based on manganese(III) tetraphenylporphyrin (TPP) complexes with various axial ligands (chloride, perchlorate, nitrate, and rhodanide) were studied. The electrodes showed high (compared with other anions) selectivity toward the salicylate anion in a wide range of concentrations at different pH values. The selectivity coefficients of membrane electrodes \(K_{Sal^ - /X^{n - } }^{sel} \) were determined by the bi-ionic potential method. A selectivity series was obtained based on \(K_{Sal^ - /X^{n - } }^{sel} \), which differs from Hofmeister series for classical anion exchangers. The possibility of using these electrodes in clinical practice for determining salicylate ions in human blood was shown.

Theoretical study on the electronic structure, formation and absorption spectra of lithium, sodium and potassium complexes of N-confused tetraphenylporphyrin

The present work is a theoretical study on lithium, sodium and potassium complexes of N-confused tetraphenylporphyrin (NCTPP). Its purpose is to determine the stability, binding, absorption spectra and formation energy of the complexes of NCTPP with sodium and potassium, studied here for the first time. All calculations were carried out employing density functional theory (DFT) and time-dependent DFT, using the B3LYP, PBE0 and M06-2X functionals in conjunction with the 6-31G(d,p) basis set. The results show that the energy ordering of different low-lying minimum energy structures of the three metal complexes is not the same, with the global minimum energy structures of the lithium and sodium resulting from the same tautomer of NCTPP while potassium complexes result from another tautomer of NCTPP. The insertion of Li, Na and K into NCTPP in the presence of THF is exothermic with reaction energies calculated to be −68, −56 and −50kcal/mol using the corresponding metal bis-(trimethylsilyl)amide reagents. The absorption vis–UV spectra are similar for the different metals and the Q and Soret bands are slightly red shifted as the metal changes from Li to K.

A novel complex of zinc tetraphenylporphyrin with two dioxane molecules in a rare attachment. Crystal structure, spectroscopy and theoretical calculations

We have shown the X-ray crystal structure of a novel ZnTPP–(Dioxane)2 complex and the results of solution studies by means of steady state absorption and fluorescence as well as time-resolved fluorescence techniques complemented by theoretical DFT and TD DFT B3LYP/6-31G(d,p) calculations. The ZnTPP–(Dioxane)2 crystallizes in centrosymmetric monoclinic unit cell, space group P21/c and shows a unique structure, with two dioxane molecules in “chair” conformation, placed in equatorial and axial position relative to ZnTPP core. Analysis of TD DFT B3LYP/6-31G(d,p) wave functions of ZnTPP–(Dioxane)2, allowed us to describe the nature of particular electronic transitions and to identify two bands (LE, CT) absent in its components. The former, results from the symmetry reduction of ZnTPP and the latter, from a mixed character of the HOMO (220) orbital of the complex. A red shift of the Soret and the Q band found in absorption and fluorescence spectra indicating the complex formation in solution is confirmed by the simulated absorption spectra of ZnTPP–(Dioxane)2 relative to ZnTPP unit both in the gas phase and in dioxane solution by PCM model. The estimated lifetime of the complex (1.75ns) is shorter than that of free ZnTPP unit (∼2ns).

Detection of DNA hybridization by various spectroscopic methods using the copper tetraphenylporphyrin complex as a probe

We are presenting new and highly sensitive hybridization assays. They are based on various spectroscopic methods including resonance light scattering, circular dichroism, ultraviolet spectra and fluorescence spectra, as well as atomic force microscopy, and relies on the interaction of the Cu(II), Ni(II), Mg(II), Co(II), Cd(II), and Zn(II) complexes, respectively, of tetraphenylporphyrin (TPP) with double-strand DNA (dsDNA) and single strand DNA (ssDNA). The interaction results in amplified resonance light scattering (RLS) signals and enables the detection of hybridization without the need for labeling DNA. The RLS signals are strongest in case of the Cu (II)-TPP complex which therefore was selected as the probe. The technique is simple, robust, accurate, and can be completed in less than one hour.

The gas-phase reactions of metal porphyrins with diazoacetate esters

The Mn(III), Fe(III) and Co(III) complexes of tetraphenylporphyrin were allowed to react with ethyl and t-butyl diazoacetate in an ion trap mass spectrometer. The manganese system produces only adducts, but the iron and cobalt systems give addition with loss of N2 to produce carbene-like species. All the reactions are fast and approach the collision-controlled limit. Fragmentation of the iron and cobalt carbene species follow three major pathways: (a) alkene loss from the ester to give a carboxylic acid (which can subsequently decarboxylate to give CH2 complexed to the metal porphyrin), (b) homolytic cleavage of the ester OR bond with loss of CO2 and an alkyl radical to produce CH complexed to the metal porphyrin, and (c) alcohol loss to give CCO complexed to the metal porphyrin. Computational data from density functional theory (B3LYP) are consistent with the observed reactivity trends and indicate that all the carbene complexes prefer a MN insertion structure where the carbene carbon bonds to the metal and one of the porphyrin nitrogens (metalnitrogen bond is lost). The MN insertion structures are generally more than 25kcal/mol more stable than the conventional metal carbene structures, MC, at the B3LYP level and should dominate their reactivity.

Computational Insight into the Electronic Structure and Absorption Spectra of Lithium Complexes of N-Confused Tetraphenylporphyrin

The present work is a theoretical investigation on lithium complexes of N-confused tetraphenylporphyrins (aka inverted) employing density functional theory (DFT) and time-dependent DFT, using the B3LYP, CAM-B3LYP, and M06-2X functionals in conjunction with the 6-31G(d,p) basis set. The purpose of the present study is to calculate the electronic structure and the bonding of the complexes to explain the unusual coordination environment in which Li is found experimentally and how the Li binding affects the Q and the Soret bands. The calculations show that, unlike a typical tetrahedral Li(+) cation, this Li forms a typical bond with one N and interacts with the remaining two N atoms, and it is located in the right place to form an agostic-like interaction with the internal C atom. The reaction energy, the enthalpy for the formation of the lithium complexes of N-confused porphyrins, and the effect of solvation are also calculated. The insertion of Li into N-confused porphyrin, in the presence of tetrahydrofuran, is exothermic with a reaction energy calculated to be as high as -72.4 kcal/mol using the lithium bis(trimethylsilyl)amide reagent. Finally, there is agreement in the general shape among the vis-UV spectra determined with different functionals and the experimentally available ones. The calculated geometries are in agreement with crystallographic data, where available.

Photoinduced electron transfer in pentacoordinated complex of zinc tetraphenylporphyrin and isoquinoline N-oxide. Crystal structure, spectroscopy and DFT studies

A novel, pentacoordinated complex of (1:1) zinc tetraphenylporphyrin and isoquinoline N-oxide (ZnTPP–IQNO) was synthesized and its crystal structure along with photophysical properties by experimental methods (absorption, steady state and time-resolved emission) in conjunction with DFT and TD DFT calculations were investigated. In ZnTPP–IQNO complex, the isoquinoline N-oxide ligand (IQNO) is directly coordinated to the central zinc atom of the ZnTPP unit through the oxygen atom of the NO group and crystallizes in centrosymmetric triclinic unit, in the space group P 1 ¯ . Particular contacts between the two monomeric units (hydrogen bonds, O ⋯ H–C interactions, …etc.) lead to a supramolecular dimer which forms the layers propagating both along the a and the b-axis. The electronic locally excited and the charge-transfer states of the complex were calculated by TDDFT CAM-B3LYP/6-31G(d,p) method. A surprising presence of the charge transfer states between the Soret and the Q bands leads to excitation energy dissipation processes involving the opening of the radiationless channels of excited ZnTPP–IQNO complex. Emission from the S 1 state (Q band) in ethyl acetate decays accordingly to monoexponential function (1.92 ns) while a bi-exponential decay is found in n-propanol [(2.5 ns (87%); 14.4 ns (13%)] and in the solid state [1.36 ns (67.5%), 7.31 ns (32.5%)].

Preparation and preliminary evaluation of [67Ga]-tetra phenyl porphyrin complexes as possible imaging agents

[67Ga]labeled tetraphenyl porphyrin ([67Ga]-TPP) was prepared using freshly prepared [67Ga]GaCl3 and tetraphenyl porphyrin (TPPH2) for 30–60 min at 25 °C (radiochemical purity: >97 ± 1% ITLC, >98 ± 0.5% HPLC, specific activity: 13–14 GBq/mmol). Stability of the complex was checked in final formulation and human serum for 24 h. The partition coefficient was calculated for the compound (log P 1.89). The biodistribution of the labeled compound in vital organs of wild-type rats was studied using scarification studies and SPECT imaging up to 24 h. A detailed comparative pharmacokinetic study performed for 67Ga cation and [67Ga]-TPP. The complex is mostly washed out from the circulation through kidneys and can be an interesting tumor imaging/targeting agent due to low liver uptake and rapid excretion through the urinary tract.

Electrospray ionization mass spectrometric analyses of rhodium tetraphenylporphyrin complexes as electrocatalysts for CO oxidation by tandem mass spectrometry and hyphenated method with capillary electrophoresis

Carbon monoxide (CO) poisoning of platinum (Pt)-based electrocatalysts is a huge obstacle in the development of proton-exchange membrane fuel cells. Fuel cell performance can be improved by removing CO through electrolytic oxidation. Yamazaki et al. synthesized several rhodium (Rh) tetraphenylporphyrin complexes as electrocatalysts to reduce CO poisoning. Experimental results showed that these complexes display higher electrochemical CO oxidation activity than previously synthesized Rh octaethylporphyrin complex and that the differences in the structures of p-substituted groups influence their activity. To confirm the formation of these Rh tetraphenylporphyrin complexes, analyses were performed using electrospray ionization mass spectrometry (ESI-MS), electrospray ionization tandem mass spectrometry (ESI-MS/MS), and capillary electrophoresis-electrospray ionization mass spectrometry (CE-ESI-MS). In ESI-MS, peaks other than that of the Rh tetraphenylporphyrin complex were occasionally detected at different m/z values. The ESI-MS/MS and CE-ESI-MS results suggest that these peaks correspond to the complexes coordinating CO or other ions, or to remaining uncoordinated tetraphenylporphyrins. Coordination of CO is supported by the ESI-MS/MS results for the Rh octaethylporphyrin complex. Separation of the uncoordinated tetraphenylporphyrin from Rh tetraphenylporphyrin complex was achieved by CE-ESI-MS.

Immobilization of Zinc Porphyrin Complexes on Pyridine-Functionalized Glass Surfaces

In order to immobilize sublimable and fluorescent dye molecules on transparent surfaces for the detection of far field molecular interference experiments, we investigate the potential of pyridine-functionalized glass substrates as coordination sites for the zinc complex of tetraphenylporphyrin (ZnTPP). Borosilicate glass is functionalized with 4-(6-(ethoxydimethylsilyl)hexyloxy)pyridine in order to cover the glass surface with pyridine subunits. ZnTPP molecules are deposited by sublimation through mechanical masks of various sizes in a high-vacuum chamber. The resulting micropatterns are analyzed using epifluorescence microscopy which also allows us to define a measure for the quality of molecular immobilization. We observe a reduced mobility and an increased efficiency for the trapping of ZnTPP on pyridine-functionalized surfaces.

Luminescence of metal complexes of chelate-substituted tetraphenylporphyrin

The luminescence and absorption spectra of some metal complexes of new tetraphenylporphyrin derivatives containing a chelating group with a heavy atom in the ligand structure were studied and compared with the properties of the zinc complex of unsubstituted tetraphenylporphyrin. The quantum yields of fluorescence and phosphorescence of liquid and frozen solutions of these compounds were measured. The life-times of delayed emission have been estimated, and the nature of bands in the absorption and luminescence spectra of the complexes and their relation with the structure are discussed.

Optical Non-Linearity in Thin Films and Solutions of C&lt;SUB&gt;60&lt;/SUB&gt;-Zn(II) Tetraphenylporphyrin Complexes

Optical Non-Linearity in Thin Films and Solutions of C-60-Zn(II) Tetraphenylporphyrin Complexes

Chlorophyll and Metal Porphyrins in Photocatalytic Redox Reactions of Hydrogen Peroxide

The photocatalytic decomposition of Н 2 О 2 in the presence of chlorophyll and metal complexes of tetraphenylporphyrin and phthalocyanine immobilized on silica was studied. The value of adsorption of porphyrins is shown to influence kinetics of Н 2 О 2 decomposition. Processes of reduction of some electron acceptors photocatalyzed by chlorophyll in Н 2 О 2 solution are demonstrated.

Structure of pluronic F-127 and its tetraphenylporphyrin complexes: X-ray diffraction study

The structure of pluronic F-127 and its complexes with tetraphenylporphyrin has been studied by SAXS and WAXS techniques. It has been shown that the samples prepared via evaporation of chloroform and aqueous solutions of pluronic and its mixtures with tetraphenylporphyrin have a semicrystalline layered structure with the crystalline phase composed of poly(ethylene oxide). The identity period of layers in the samples prepared from the aqueous solution of pluronic has been found to be larger than that in the samples prepared from chloroform solutions of the polymer. This result may apparently be explained by a more pronounced hydration of the samples prepared by the former method. The presence of tetraphenylporphyrin in the samples has an insignificant effect on the parameters of the crystalline and layered structures of pluronic. When the tetraphenylporphyrin content is not larger than its solubilization limit with pluronic, tetraphenylporphyrin concentrates in the amorphous layers of pluronic in the noncrystalline finely dispersed state.

Luminescent Au(iii) organometallic complex of N-confused tetraphenylporphyrin

An organometallic Au(III) complex of N-confused tetraphenylporphyrin has been synthesized and its electrochemical and photophysical properties investigated; unique emission is observed in solution at ambient temperature.

Immobilization of Fe, Mn and Co tetraphenylporphyrin complexes in MCM-41 and their catalytic activity in cyclohexene oxidation reaction by hydrogen peroxide

Metalloporphyrin catalysts are able to carry out selective oxidation of organic substrates with several oxidizing agents. Recently, mesoporous materials have been studied as supports because they present high specific surface area, better dispersion and regeneration properties. This work presents the results of synthesis, characterization and application of three metalloporphyrin catalysts (FeTPPCl, MnTPPCl and CoTPP, where TPP = tetraphenylporphyrin) anchored on MCM-41, in the reaction of cyclohexene oxidation with hydrogen peroxide. A modified sol–gel preparation was chosen for the synthesis of the MCM-41 mesoporous material, as well as the anchoring was followed by Soxhlet extraction to ensure strong adsorption of the complex. The supported materials were much more stable than pure metalloporphyrins. The synthesized catalysts were characterized by UV–vis, FTIR, XRD, ICP-AES, 29Si MAS-NMR and thermal analysis, before and after incorporation. Evidence of the metalloporphyrin immobilization was confirmed by elemental analysis and their activity in the oxidation reaction. FeTPPCl/MCM-41 showed higher conversion than CoTPP/MCM-41 and MnTPPCl/MCM-41. However, MnTPPCl/MCM-41 even in low concentration on the support showed a good conversion for the direct oxidation of cyclohexene with the highest turnover number (1.54 × 10 5). All catalysts showed similar selectivity that favors allylic oxidation products over epoxidation. No leaching of the metalloporphyrins was observed after the reaction.

Oxidação seletiva de benzeno a fenol utilizando catalisadores metaloporfirínicos

Tetraphenylporphyrin (5,10,15,20 meso-tetraphenylporphyrin, TPP) complexes containing copper (II) [CuII(TPP)] and iron (III) [FeIII(TPP)Cl] have been investigated as catalysts in the direct oxidation of benzene to phenol, utilizing tert-butyl hydroperoxide and hydrogen peroxide, in liquid phase. The catalysts have been prepared by methods described in the literature and have been characterized by a variety of methods, presented in this work. The most promising catalytic system was [FeIII(TPP)Cl] with hydrogen peroxide, in acetonitrile. Various reaction parameters such as molar ratio of substrate, molar ratio of oxidant, catalyst concentration and reaction temperature have been studied. The effect of oxidant and the role of solvent are discussed in the present work.

Femtosecond time-resolved photo-absorption studies on the excitation dynamics of chromium(III) porphyrin complexes in solution

The electronic relaxation dynamics of the excited states of the chromium(III) tetraphenylporphyrin complexes, [Cr(TPP)(Cl)(L)] (L = H 2O, pyridine, 1-methylimidazole), in toluene were studied by using femtosecond time-resolved absorption spectroscopy. The excited state ( 4T 1) of 1-methylimidazole and pyridine complexes given by a very rapid intersystem crossing from 4S 1 to 4T 1 decays to establish the 4T 1 ⇌ 6T 1 equilibrium in several hundred picoseconds. The 4T 1 state of [Cr(TPP)(Cl)(H 2O)] exhibits a biexponential decay composed of the photodissociation process of the axial H 2O ligand and the decay of the photolyzed intermediate to the ground state of [Cr(TPP)(Cl)].