Axial Coordination Reaction Research Articles

Ultra-sensitive detection of pyridine in water using zinc porphyrin incorporated in a transparent hydrophobic film

In this study, we investigated the axial coordination reaction between pyridine and zinc meso-tetra(4-sulfonatophenyl)porphyrin (ZnTPPS) incorporated in a transparent layered double hydroxide (LDH) film modified with 1-decanesulfonate (C10S) in an aqueous solution. The apparent equilibrium constant ({K}_{11}) of the axial coordination reaction between pyridine and ZnTPPS incorporated in the transparent ZnTPPS/C10S/LDH film was approximately 260 times that of the corresponding reaction in an aqueous solution. The hydrophobisation of the LDH interlayer space by C10S, which led to the elimination of water molecules surrounding ZnTPPS and enabled the accumulation of pyridine molecules, was responsible for such a significant increase in the apparent {K}_{11} value. The developed film can detect pyridine in aqueous solutions with ultra-high sensitivity in the order of 10−5 mol/L through changes in the colour tone, which is comparable to the molecular detection ability of insect antennae. The sensing response was also observed at pyridine concentrations as low as 10−9 mol/L.

Oriented Self-Assembled Monolayer of Zn(II)-Tetraphenylporphyrin on TiO2 Electrode for Photoelectrochemical Analysis.

The photoelectrochemical performance of a zinc porphyrin sensitized TiO2 photoelectrode fabricated through the axial-coordination strategy has been studied. Zinc(II) tetraphenylporphyrin (TPPZn) was immobilized on the TiO2 electrode through the axial coordination reaction with surface premodified methyl 4-(1 H-imidazol-1-yl)benzoate (PhImMe). Spectral characterizations were carried out to confirm the robust interaction between TPPZn and PhImMe, while the chemical bonding of PhImMe on TiO2 surface has been evidenced by XPS measurement. The modified TiO2 electrode produces a stable and enhanced photocurrent signal under 410 nm irradiation at a bias of 0.2 V in phosphate buffer solution, compared with pristine TiO2. A sensitive increment of the photocurrent is observed with the addition of l-glutathione. A possible mechanism for this photoelectrochemical process includes the photoexcitation of the porphyrin, electron injection from porphyrin toward the TiO2, and the hole-scavenging process by the reductants. The "lying-low" surface conformation of the porphyrin plane might facilitate the PEC process owing to the enhanced electronic coupling between the porphyrin plane and the TiO2 substrate. A PEC analysis on l-glutathione has been carried out to evaluate the photoelectrochemical performance of the modified TiO2 electrode, which presents the wide linear ranges of 5-80 μM and 80-5000 μM, with a lower detection limit of 3.21 μM at an S/N ratio of 3. This work reports for the first time on the PEC performance of metalloporphyrin axially coordinated on a semiconductor surface and could lead to the designing of more efficient photoelectrochemical sensors and devices based on similar electrode structures.

Axial coordination reactions with nitrogenous bases and determination of equilibrium constants for zinc tetraarylporphyrins containing four β,β′-fused butano and benzo groups in nonaqueous media

The axial coordination properties of six zinc tetraarylporphyrins with seven different nitrogenous bases were examined in CH2Cl2 for derivatives containing four [Formula: see text],[Formula: see text]-fused butano or benzo groups and the equilibrium constants (log[Formula: see text] determined using spectral titration methods. The examined compounds are represented as butano(YPh)4PorZn and benzo(YPh)4PorZn, where Por is the porphyrin dianion and Y is a CH3, H or Cl substituent on the para-position of each meso-phenyl ring of the macrocycle. The initial four-coordinate butano- and benzoporphyrins will axially bind one nitrogenous base to form five-coordinate derivatives in CH2Cl2 and this leads to a 4–22 nm red-shift of the Soret and Q bands. The log[Formula: see text] values range from 1.98 to 4.69 for butano(YPh)4PorZn and from 3.42 to 5.36 for benzo(YPh)4PorZn, with the exact value depending upon the meso and [Formula: see text]-substituents of the porphyrin and the conjugate acid dissociation constants (p[Formula: see text] of the nitrogenous base.

Spectroscopic properties of zinc porphyrin-functionalized poly(4-vinylporphine) derivatives in the solutions, solid powders and doped PMMA films

Polymeric zinc porphyrin derivatives were prepared through an axial coordination reaction of a charged water-soluble zinc porphyrin (ZnTMPyP) with poly(4-vinylpyridine) (PVP). Molar ratios of the porphyrin substituents relative to the pyridine monomers of PVP in the as-prepared polymeric porphyrins were about 1:30, 1:250 and 1:1000. Moreover, ZnTMPyP and ZnTMPyP–PVP doped poly(methylmethacrylate) (PMMA) composites and their optically transparent thin films were prepared. Compositions and spectroscopic properties of these porphyrins were investigated by using UV–vis absorption, infrared, X-ray electron and fluorescence spectroscopy as well as time-resolved fluorescence spectroscopy. The Soret absorption band of the porphyrins appeared at 438nm in the methanol solutions, which red shifted to 456nm in the doped PMMA films. Although the ZnTMPyP solid powders gave off very weak luminescent emission, its functionalized polymers and doped PMMA thin films gave off strong emissions at around 640nm. It was revealed that emission lifetime of the zinc porphyrin was about 0.2ns in the solid powders and 0.6–1.5ns in the polymeric porphyrins and the doped composite thin films.

Pd(II)-directed layer-by-layer assembly and characterization of zinc tetrapyridylporphyrin-linked poly(4-vinylpyridine) multilayers on substrate surfaces

Polymeric zinc porphyrin derivatives have been synthesized through an axial coordination reaction of zinc tetra(pyridylporphyrin) chloride tetrakis(methochloride) (ZnTMPyP) with poly(4-vinylpyridine) (PVP). The molar fractions of ZnTMPyP relative to pyridyl substituents of PVP in the as-prepared ZnTMPyP-PVP polymers were 1:30 and 1:250. Palladium (II) directed Pd/ZnTMPyP-PVP coordination polymer multilayers were constructed on the quartz and gold substrate surfaces by the layer-by-layer (LBL) method with the use of Na2PdCl4 as the connector and the polymeric zinc porphyrins as the linkers. Compositions, film structure and morphologies of the LBL multilayers were characterized by using UV–vis absorption, X-ray photoelectron spectroscope, scanning electron microscope and atomic force microscope. The fluorescence emission properties of the porphyrins in the LBL multilayers were similar to those in the methanol solutions. The emission lifetime was about 1.36 and 0.16ns for the zinc porphyrins in the ZnTMPyP-PVP30 solution and LBL multilayers, respectively. It was revealed that the present Pd/ZnTMPyP-PVP LBL multilayers could be used as heterogeneous photocatalyst for the degradation of methyl orange under irradiation at room temperature. Because the multilayers were anchored on the substrate surface through covalent and coordinative bonding, they were of high stability, good recyclability, and facile separation from the reaction system.

Coordination Reaction between Series Hydroxyl-Porphyrins and Pb<sup>2+</sup> Studied by Spectroscopic Method

Reaction conditions and spectroscopy properties of series hydroxyl-porphyrins for bonding with Pb2+ were described. A stable complex was formed with molar ratio 1:1 in the solution of N,N-dimethylformamide (DMF) with 0.6ml tween-80 as surfactant, when the pH was controlled at 6.5. The hydroxyl group on the benzene ring resulted in Soret band red shift of Pb-porphyrin complexes from 415.8 to 422.7nm, and isosbestic point of the axial coordination reaction appeared at 419.5nm. The study of thermodynamics predicted that the monohydroxyl-porphyrin had the optimal identification effects for Pb2+.

The catalytic activity of poly(N-vinylimidazole)/SiO2-supported metalloporphyrins in ethyl benzene oxidation

In this paper, novel kind of supports for immobilizing metalloporphyrin catalysts, poly(N-vinylimidazole)/SiO2 (PVI/SiO2) were prepared in the manner of “grafting from”. Then, various metalloporphyrins (MPs), such as cobalt, iron and manganese tetraphenylporphyrins (CoTPP, FeTPP, MnTPP), cobalt tetra (para-nitrophenyl) porphyrin (CoTNPP), and cobalt tetra (para-chlorophenyl) porphyrin (CoTClPP), were immobilized on the supports PVI/SiO2 via the axial coordination reaction between MPs and the imidazole groups of the grafted PVI, resulting in the heterogenized catalysts MPs–PVI/SiO2. The supported catalysts were characterized by IR and UV–Vis spectra. The catalytic performances of MPs–PVI/SiO2 for the oxidation of ethyl benzene in the absence of any reductant and solvent were investigated and compared in detail. The experimental results revealed that MPs–PVI/SiO2 could effectively activate dioxygen, and obviously catalyze the oxidation of ethyl benzene to acetophenone. The catalytic activities of MPs–PVI/SiO2 increased with increase of the electron-deficient degree of the peripheral substituent attached to the benzene ring outside the porphyrin ring. The catalytic activities of MPs–PVI/SiO2 differed among the different metals and the different substitutional groups according to the following sequences: Co(II) > Fe(III) > Mn(III), and CoTNPP > CoTClPP > CoTPP. In comparison, the catalytic activity of CoTNPP–PVI/SiO2 was the best. Under the reaction conditions of 120 °C and the ordinary pressure of oxygen, the catalyst CoTNPP–PVI/SiO2 gave wonderful results with 33.4 mol% yield of acetophenone.

Coordination properties of zinc 5,15-di(ortho-aminophenyl)octaalkylporphyrin in reactions with mono- an dibasic nitrogen bases

The coordination properties of zinc 5,15-di(ortho-aminophenyl)octaalkylporphyrin in reactions with mono- and dibasic nitrogen bases in benzene are studied by means of computational modeling and spectrophotometric titration. The stability of molecular zinc porphyrinate complexes in solution is estimated and their structure is determined. The correlation between the coordination properties of the compound under investigation and electronic and conformational factors of the macrocycle is established. The base nature is shown to affect the stability of zinc porphyrinate complexes. The correlations between the calculated σ bond energy of the zinc atom with the nitrogen atom of the base (E b) and the equilibrium constant of the axial coordination reaction are obtained. It is demonstrated that the reaction is accompanied by an increase in steric hindrance and a change in the type of deformation of the porphyrin ligand.

Axial Coordination Reaction Between Nitryl Phenyl Zn Porphyrin and Imidazole Derivatives Studied by Spectroscopic Method

The spectroscopic properties of coordination reactions between two Zn prophyrin [5-(p-nitrylphenyl)-10,15,20-triphenyl Zn porphyrin and 5-(o-nitrylphenyl)-10,15,20-triphenyl Zn porphyrin] and three imidazole(Im) derivatives were studied by means of UV-Vis spectroscopy titrations and fluorescence spectroscopy.The axial coordination reactions were related to different positions of substituent group in Zn prophyrin and the structure of guest.The results show:the axial coordination reaction was carried out in a molar ratio of 1∶1,the association constants decreased in the order of K(2-MeIm)K(N-MeIm)K(Im),in which the maximum association constant was 5.85×105 L/mol between 5-(o-nitrylphenyl)-10,15,20-triphenyl Zn porphyrin and 2-MeIm;the association constant would decrease with increasing temperature,which was a disadvantage factor for the reaction;the thermodynamic parameters revealed that the driving force was the change of enthalpy and the reaction was spontaneous;the intensity of fluorescence increased in the system of axial coordination reaction of 5-(p-nitrylphenyl)-10,15,20-triphenyl Zn porphyrin(fluorescence peak:592.9 nm,634.2 nm) with increasing the guest concentration,and the fluorescence quenching exhibited in the system of axial coordination reaction of 5-(o-nitrylphenyl)-10,15,20-triphenyl Zn porphyrin(fluorescence peak:583.6 nm,629.8 nm).The fluorescence effect was determined by the position of nitryl group in Zn prophyrin and independent of the structure of guest.

Realizing metalloporphyrin functionalization of 4-vinylpyridine copolymer via axial coordination reaction

Cobalt tetra(para-chlorophenyl)porphyrin ( CoTCPP ) and zinc tetraphenyl porphyrin ( ZnTPP ) were linked on the side chains of the copolymer of 4-vinylpyridine (4VP) and styrene (St), P(4VP-co-St), via axial coordination reactions, respectively, and the metalloporphyrin-functionalized macromolecules, CoTCPP -P(4VP-co-St) and ZnTPP -P(4VP-co-St), were prepared. Their chemical structures were characterized by FTIR and 1H NMR. The spectral properties of the two macromolecular axial coordination complexes were mainly studied, and their photophysical behavior were discussed in depth. The experimental results show that the metalloporphyrin-functionalized macromolecules, CoTCPP -P(4VP-co-St) and ZnTPP -P(4VP-co-St), can be prepared favorably through axial coordination reaction with the side pyridine groups of the copolymer P(4VP-co-St) as ligands. The two complexes have characteristic spectra similar to that of the small molecular metalloporphyrins, CoTCPP and ZnTPP , respectively. At the same time, they also display the characteristic spectroscopic property of axial coordination complexes: the electronic adsorption spectra of CoTCPP -P(4VP-co-St) and ZnTPP -P(4VP-co-St) red-shifted obviously as compared to that of CoTCPP and ZnTPP , and the fluorescence emission of ZnTPP -P(4VP-co-St) blue-shifted apparently with respect to that of ZnTPP . For CoTCPP -P(4VP-co-St) and ZnTPP -P(4VP-co-St), some polymer effects were found: (1) the bonding degree of the small molecular metalloporphyrin, CoTCPP or ZnTPP , on the side chains of the copolymer P(4VP-co-St) has a limit value because of the steric hindrance and there is a bonding degree difference between the actual value and the theoretical value; (2) for ZnTPP -P(4VP-co-St), slight energy transfer between adjacent ZnTPP units on an identical macromolecule occurs, leading to slight static quench of the fluorescence emission as the bonding density of ZnTPP units on the side chains of the copolymer P(4VP-co-St) reaches a certain value.

Structure and properties of cobalt(III) porphyrinate molecular complexes

By combined calculation and spectral methods the structure and properties of the molecular complexes of cobaltoctaalkylporphyrin in benzene were studied. Geometric and energy characteristics of the optimized molecules of cobalt porphyrinate and its molecular complexes were calculated. Their stability and degree of deformation were evaluated. It was established that the process of axial coordination is accompanied by the reduction of cobalt. Interrelation between the stability of the cobalt porphyrinate complexes and the nature of the base was noted. A change in the degree of deformation of the porphyrin ligand in the course of reaction was shown. Correlations between the calculation data and the value of the equilibrium constant of the axial coordination reaction were obtained.

Preparation of cross-linked copolymer microspheres 4VP/St and cobalt tetraphenylporphyrins supported on it

The cross-linked microspheres 4VP/St made of 4-vinylpyridine (4VP) and styrene(St) were prepared with suspension copolymerization method using ethyl glycol dimethacylate (EGDMA) as cross-linker and polyvinyl alcohol (PVA) as disperser. The cobalt tetraphenylporphyrins (CoPs) were immobilized on 4VP/St microspheres via the axial coordination reaction between CoPs and the pyridine groups of 4VP/St microspheres, resulting in the functional microspheres CoP-4VP/St. The chemical structure of 4VP/St and CoP-4VP/St were characterized with infrared spectrum and their morphologies were observed with the scanning electron microscope. The experimental results show that via controlling the various reaction conditions of the suspension copolymerization, the 4VP/St microspheres with excellent sphericity and narrow particle diameter distribution can be gained. In addition, CoPs are successfully immobilized on 4VP/St microspheres by means of Co–N bonds, on which the immobilized content of CoPs goes up to 10.7–17.5 μmol/g.

Studies on preparation of metalloporphyrin‐functionalized PVI and PVI/SiO2 via axial coordination reaction

AbstractCobalt tetraphenylporphyrin (CoTPP) was bond on the side chains of poly(N‐vinylimidazole) (PVI) and immobilized on PVI/SiO2 via axial coordination reactions, respectively, leading to the soluble metalloporphyrin‐functionalized PVI (denoted as CoTPP–PVI) and the particles CoTPP–PVI/SiO2. The above two target products were characterized using spectroscopy methods such as infrared spectrum, electronic absorption spectrum, and fluorescence emission spectrum. And the effects of various factors on the bonding reaction and immobilization reaction of CoTPP were studied in detail. The experimental results show that CoTPP–PVI and CoTPP–PVI/SiO2 can be prepared favorably through axial coordination reaction of CoTPP with the side imidazole groups of PVI and PVI/SiO2. In addition, the soluble CoTPP–PVI has all the spectral characteristics of CoTPP. As compared to CoTPP, the adsorption spectra of CoTPP–PVI exhibit red shift obviously. In the immobilization process of CoTPP on PVI/SiO2, the higher the concentrations of CoTPP and the reaction temperature, the greater the immobilization amount of CoTPP is. Copyright © 2009 John Wiley & Sons, Ltd.

In vivo Electrochemistry of C‐Type Cytochrome‐Mediated Electron‐Transfer with Chemical Marking

In subsurface environments, certain types of microbes employ a unique metabolic strategy to respire on the naturally abundant iron-based minerals. Metal-reducing bacteria, such as those of the genus Shewanella and Geobactor, have a significant quantity of redox proteins located in their outer membrane (OM), and they transfer electrons from the cell surface to attached Fe oxides. 3] This is the terminal step in metabolism, and is an essential process to eliminate the excess electrons generated during the microbial oxidation of organic matter. Fe oxide respiration is considered to play an important role in the global biogeochemical cycling of iron. This process has also gained increasing attention for its potential application in mediatorless microbial fuel cells (MFCs). A great deal of research has been focused on measuring and proving bacterial extracellular electron-transfer (ET) respiration. The decaheme c-type cytochromes (c-Cyts), such as OmcA and MtrC, have been predicted to mediate ET to Fe oxides or electrodes. Up until this point, however, electrochemical and spectroscopic characterization of OM c-Cyts has been strictly limited to studies with purified proteins, although ET in living systems might be different from ET in purified proteins. In the whole-cell system, c-Cyts form a membrane-associated protein complex, and protein–protein and protein– membrane interactions would largely affect the energetics and kinetics of extracellular respiratory ET reactions. The main obstacle for the whole-cell study lies in the shortage of methods to differentiate c-Cyts from a number of uncharacterized biological molecules. Moreover, the extreme complexity and dynamic properties of living cells impede our ability to utilize knowledge developed in studies with purified proteins. Herein we report the control of the electronic states of OM c-Cyts in living cells of Shewanella by using an axial-coordination reaction on the heme groups of c-Cyts. We are the first to electrochemically identify OM c-Cyts and determine their ET kinetics under living conditions by using the specific binding affinity of nitric monoxide (NO). Our results reveal the existence of an respiratory ET chain with unusually high efficiency at the outer cell-membrane/electrode interfaces. Extracellular ET in living cells of Shewanella loihica PV-4 was monitored by using a single-chamber, three-electrode system with lactate as the carbon source and electron donor, as described in our previous studies. A tin-doped indium oxide electrode (ITO) was used as the working electrode and was placed on the bottom surface of the reactor. The cells were inoculated into the reactor under potentiostatic conditions at 0.4 V (versus the standard hydrogen electrode, SHE) for 25 h to prepare an electrode with attached cells. The optical microscopy image showed the formation of a thin layer (approximately 2 mm in length and 0.5 mm in width) that consisted of rod-shaped cells ; most of the cells attached horizontally to the electrode surface, not through the apex of their rod-like shape. Viability of the cells on the ITO electrode was confirmed by the generation of a microbial current (Figure S1 in the Supporting Information). As shown in the cyclic voltammograms (CVs, Figure 1), strain PV-4 exhibited one redox wave with a

Efficient biomimetic aerobic oxidation of phenylethane catalyzed by P(4VP-co-St)/SiO 2-supported metalloporphyrins

In this work, three kinds of metalloporphyrins (CoPs, FePs, and MnPs) were immobilized on the grafting particles P(4VP-co-St)/SiO 2 through the axial coordination reaction, respectively, and the supported biomimetic catalysts MP-P(4VP-co-St)/SiO 2 (M = Co, Fe and Mn) were prepared. The catalytic performances of various supported biomimetic catalysts for the oxidation of phenylethane in the absence of any reductant and solvent were investigated and compared detailedly. The experimental results show that the supported catalysts MP-P(4VP-co-St)/SiO 2 can effectively activate dioxygen, and obviously catalyze the oxidation of phenylethane to hypnone. When MPs are immobilized on the supports P(4VP-co-St)/SiO 2, the catalytic activity of MP-P(4VP-co-St)/SiO 2 is improved greatly. Also the catalytic activities of MP-P(4VP-co-St)/SiO 2 differ among the different metals, according to the following series: Co(II) > Fe(III) > Mn(III). Under the reaction conditions of 393 K and the ordinary pressure of oxygen, the catalyst CoP-P(4VP-co-St)/SiO 2 gave wonderful results with 24 mol% yield and 95% selectivity to the main product hypnone, and the another product, α-phenylethanol was few. All these results indicate that the grafting particles P(4VP-co-St)/SiO 2 can not only protect metalloporphyrin from oxidation, but also promote it to activate O 2. Additionally, some rules were specially found in the studies: (1) CoPs as a biomimetic catalyst had an optimum used amount, and excess addition would make the catalyst activity worse; (2) the immobilization density of CoPs on P(4VP-co-St)/SiO 2 surface still had the high-point; (3) the catalyst activity trended to steady during nine cycle.

A novel method for immobilization of Co tetraphenylporphyrins on P(4VP-co-St)/SiO 2: Efficient catalysts for aerobic oxidation of ethylbenzenes

In this paper, poly(4vinylpyridine-co-styrene) (P(4VP-co-St)) was grafted on silica gel particles in the manner of “grafting from”, and the grafting particle P(4VP-co-St)/SiO 2 was gained. The grafting particle P(4VP-co-St)/SiO 2 is a novel kind of supports for immobilizing metalloporphyrin catalysts. Then, the immobilization of cobalt tetraphenylporphyrin (CoTPP) on the supports P(4VP-co-St)/SiO 2 was carried out via the axial coordination reaction between CoTPP and the pyridine groups of the grafted P(4VP-co-St), resulting in the heterogenised catalysts CoTPP–P(4VP-co-St)/SiO 2. The synthesized catalysts were characterized by FTIR and the axial coordination process between CoTPP and the grafted P(4VP-co-St) was confirmed by UV–vis. The effects of various factors on the immobilization reaction of CoTPP were studied in detail. Finally, the catalytic performance of CoTPP–P(4VP-co-St)/SiO 2 in the catalytic oxidation process of ethyl benzene was investigated. The experimental results show that the axial coordination reaction is a very easy and novel method for favorably immobilizing CoTPP onto the P(4VP-co-St)/SiO 2 surfaces. During the immobilization process of CoTPP on P(4VP-co-St)/SiO 2, the most bonding amount of CoTPP (0.19 g/g) is obtained under the lower temperature (5 °C) and the higher concentration of CoTPP(6.0 mg/ml) lasting 4 h. Moreover, the supported catalyst CoTPP–P(4VP-co-St)/SiO 2 can effectively activate the dioxygen, and obviously catalyze the transform of ethylbenzene into acetophenone. So it exhibits the fine catalytic activity.

Electrochemical and binding properties of a meso-tetra(4-pyridyl)porphyrinatozinc supermolecule containing four μ3-oxo-triruthenium acetate clusters

The synthesis and characterization of a zinc meso-tetra(4-pyridyl)porphyrin containing four coordinated μ3-oxo-triruthenium acetate cluster complexes, ZnTCP , are reported. The coordination of four ruthenium acetate clusters to the zinc porphyrin has been confirmed by 1 H and 13 C NMR spectroscopy, including COSY and HETCOR bidimensional correlation techniques. Cyclic voltammetry and spectroelectrochemistry studies have revealed the presence of seven redox processes in the −1.5 to 2.5 V range, four of them attributed to cluster-centered ( Ru IV,IV,III/ Ru IV,III,III/ Ru III,III,III/ Ru III,III,II/ Ru III,II,II) and three to porphyrin ring-centered ( ZnP +/ ZnP / ZnP .−/ ZnP 2−) redox reactions. The axial coordination reaction has been monitored by spectrophotometric titrations in dichloromethane and acetonitrile, in the 380–480 nm range, using pyridine, imidazole, water and acetonitrile as ligands. The influence of the peripheral ruthenium complexes on the electronic properties of the porphyrin ring has been assayed by measuring the axial coordination properties of the zinc ion. The calculated equilibrium constants for axial coordination of pyridine and imidazole to ZnTCP in dichloromethane are respectively one and two orders of magnitude higher than for meso-tetraphenylporphyrinatozinc, showing a regular increase as a function of the basicity of the ligands. The results have demonstrated that the Ru (III,III,III) species act as electron-withdrawing groups, decreasing significantly the electronic density on the porphyrin ring.

Formation of a Porphyrin Monolayer Film by Axial Ligation of Protoporphyrin IX Zinc to an Amino-Terminated Silanized Glass Surface

A porphyrin covalently appended monolayer film on a glass substrate prepared by axial coordination reaction of protoporphyrin IX zinc (ZnPP) and a self-assembled monolayer of (3-aminopropyl)trimeth...

Thermodynamic study of axial coordination reaction of zinc porphyrin with metal Schiff base and imidazole complex

AbstractA thermodynamic study is reported for the coordination reaction of ZnT ( m‐X)PP derivatives (X = NO2, Cl, OCH3, H or CH3) with various ligands L (L= imidazole (Im), 2‐methylimidazole (Melm), clotrimidazole (CIM), imidazol‐4‐carboxaldehyde (4‐CHOIm), unsymmetrical tetradentate copper Schiff base, Culm(p‐C1), Ch(p‐Br), and nickel Schiff base, Nilm(p‐CI)), in dichloromethane solvent. Conversion of the four‐coordinated ZnT( m‐X)PP to the five‐coordinated species is followed and isosbestic behavior is exhibited in the region among 450 and 700 nm. The reaction of a copper(II) or nickel(II) imidazolate Schiff base with ZnT( m‐X)PP results in the formation of an imidazolate bridged heterobinuclear complex. The stochiometric number is unity for all axial ligands. The equilibrium constants were determined using the β band of ZnT( m‐X)‐PP in the 293–308 K range by the method of Rose and Drago. It increases with decrease in temperature, and ΔH0 0, Δ09 0. The stronger the nucleophilic ability of the axial ligand is, the larger the stability of the axial coordination product is. Hammet linear relationships and isoequilibrium relationships exist in the system studied.

The Visible Spectra and Electronic Effects in Axial Coordination Reaction of Zinc Porphyrin Complexes

The Visible Spectra and Electronic Effects in Axial Coordination Reaction of Zinc Porphyrin Complexes