Metal Phthalocyanines Research Articles

Sulfonated nickel phthalocyanine redox flow cell for high-performance electrochemical water desalination

With clean water availability raising a great technological and social challenge, saltwater desalination has become a key strategic solution. Herein, we report a nickel phthalocyanine tetrasulfonic acid tetrasodium salt (NiPcTATS)-based redox flow desalination cell (RFDC) that allows safe, efficient and continuous water-salt separation. With the new, water-soluble NiPcTATS/NiPcTATS+ redox couple as electrolyte, the RFDC effectively desalinates saltwater and achieves a high average salt removal rate of 3.11 gNaCl/(molNiPcTATS·h) and a low energy consumption of 15.0 kJ/molNaCl at 0.5 V cell voltage. The cell exhibits excellent reversibility and durability for long-term operation, benefiting from the fast-redox kinetics and chemical stability of the redox couple. Efficient solar-driven RFDC for water desalination is demonstrated by powering the cell with a solar panel. This RFDC method provides a low-cost, efficient and safe strategy to purify saltwater, and the findings with NiPcTATS-based redox couple offer new opportunities of utilizing metal phthalocyanines and derivatives in water desalination research.

Effect of metal phthalocyanines on the synthesis and physicochemical properties of polyaniline

The polymerization of aniline in the presence of metal phthalocyanines was accomplished and the effect of the metal complexes on the physicochemical properties of polyaniline was examined based on UV-visible spectra, cyclic voltammograms, morphology and conductivity of the polymers. The formation of polyaniline in the presence of metal phthalocyanines led to an increase in polymer particle sizes and to a slightly higher conductivity of the samples, as compared to those of the initial polyaniline.

Synthesis and Properties of Metal Phthalocyanines Containing Anthraquinone Chromophores

Synthesis and Properties of Metal Phthalocyanines Containing Anthraquinone Chromophores

Intercalation of Copper Phthalocyanine Within Bulk Graphite as a New Strategy Toward the Synthesis of CuO-Based CO Oxidation Catalysts.

Graphite is a widely available natural form of carbon with peculiar chemical and surface properties. It is essentially hydrophobic and consists in very stable stacks of graphene layers held together by highly delocalized π-π interactions. Its use in chemistry and in particular for catalytic applications requires modification of its structure to increase its surface area. This is commonly achieved by harsh oxidation methods which also modifies the chemical composition of graphite and enables subsequent deposition of catalytic phases via common impregnation/reduction methods. Here we show that copper phthalocyanine (CuPc) can be incorporated into unmodified bulk graphite by the straight-forward sonication of a dimethylformamide solution containing CuPc and graphite flakes. Immobilization of the CuPc complex in the graphitic matrix is shown to rely on π-π interactions between the Pc ligand and graphenic surfaces. This strong CuPc-graphene interaction facilitates oxidation of the graphitic matrix upon oxidation of the immobilized complex, as shown by thermogravimetric analysis in air. Nevertheless, a soft oxidation treatment can be designed to produce CuO nanoparticles (NPs) without degrading the dispersing graphitic matrix. These well-dispersed CuO NPs are shown (1) to decrease the degree of stacking of graphite in the solid-state by intercalation in-between graphitic stacks, (2) to be more easily reducible than bulk CuO, and (3) to be catalytically active for the oxidation of carbon monoxide. The higher mass-specific CO oxidation rates observed, as compared with CuO/alumina benchmarks, highlight the beneficial role of the carbon support and the relevance of this new strategy toward the design of copper oxide catalysts from copper phthalocyanine metal complexes.

Formation of Three-Dimensional Electronic Networks Using Axially Ligated Metal Phthalocyanines as Stable Neutral Radicals

Organic π-radical crystals are potential single-component molecular conductors, as they involve charge carriers. We fabricated new organic π-radical crystals using axially ligated metal phthalocyanine anions ([MIII(Pc)L2]−) as starting materials. Electrochemical oxidation of [MIII(Pc)L2]− afforded single crystals of organic π-radicals of the type MIII(Pc)Cl2·THF (M = Co or Fe, THF = tetrahydrofuran), where the π-conjugated macrocyclic phthalocyanine ligand is one-electron oxidized. The X-ray crystal structure analysis revealed that MIII(Pc)Cl2 formed three-dimensional networks with π-π overlaps. The electrical resistivities of CoIII(Pc)Cl2·THF and FeIII(Pc)Cl2·THF at room temperature along the a-axis were 6 × 102 and 6 × 103 Ω cm, respectively, and were almost isotropic, meaning that MIII(Pc)Cl2·THF had three-dimensional electronic systems.

Electric field control of molecular magnetic state by two-dimensional ferroelectric heterostructure engineering

Two-dimensional multiferroics have attracted tremendous attention due to their intriguing physics and promising applications. However, it has been a major challenge to discover and design two-dimensional multiferroic materials with large electric polarization and strong magnetoelectric coupling. In this work, we propose a strategy to design a two-dimensional van der Waals heterostructure with strong magnetoelectric coupling by stacking a transition metal phthalocyanine (TMPc) molecule with ferroelectric monolayer In2Se3. By first-principles electronic structure calculations, we predict that the magnetic states of the TMPc molecule can be controlled by electrically switching the polarization direction of In2Se3 using an external electric field. This strong magnetoelectric coupling effect originates from the interfacial charge transfer and orbital splitting, resulting in the different magnetic states of TMPc/In2Se3 heterostructures in two opposite ferroelectric phases. Based on the TMPc/In2Se3 heterostructure, a high-density magnetic memory device is proposed for pure electric writing and magnetic reading. Our predictions may open avenues for finding and designing multiferroic heterostructures by using two-dimensional ferroelectric materials and zero-dimensional magnetic molecules with a strong proximity effect.

Organic Heterojunction Devices Based on Phthalocyanines: A New Approach to Gas Chemosensing.

Organic heterostructures have emerged as highly promising transducers to realize high performance gas sensors. The key reason for such a huge interest in these devices is the associated organic heterojunction effect in which opposite free charges are accumulated at the interface making it highly conducting, which can be exploited in producing highly sensitive and faster response kinetics gas sensors. Metal phthalocyanines (MPc) have been extensively studied to fabricate organic heterostructures because of the large possibilities of structural engineering which are correlated with their bulk thin film properties. Accordingly, in this review, we have performed a comprehensive literature survey of the recent researches reported about MPc based organic heterostructures and their application in gas sensors. These heterostructures were used in Organic Field-Effect Transistor and Molecular Semiconductor—Doped Insulator sensing device configurations, in which change in their electrical properties such as field-effect mobility and saturation current in the former and current at a fixed bias in the latter under redox gases exposure were assessed to determine the chemosensing performances. These sensing devices have shown very high sensitivity to redox gases like nitrogen dioxide (NO2), ozone and ammonia (NH3), which monitoring is indispensable for implementing environmental guidelines. Some of these sensors exhibited ultrahigh sensitivity to NH3 demonstrated by a detection limit of 140 ppb and excellent signal stability under variable humidity, making them among the best NH3 sensors.

Comparative photophysical and femtosecond third-order nonlinear optical properties of novel imidazole substituted metal phthalocyanines

Two novel phenanthro [9,10-d]imidazole substituted metal phthalocyanines, ImCuPc and ImZnPc, have been synthesized and their potential as photosensitizers has been investigated through optical, electrochemical, and ultrafast nonlinear optical (NLO) studies, including their excited state dynamics. The absorption as well as emission spectra of both the title compounds exhibited negligible Stokes shift in different solvents. The molecules depicted a broad Soret band due to the incorporation of phenanthro[9,10-d]imidazole moiety while the Q-bands were characteristic to their metal phthalocyanine group. DFT studies elucidated the HOMO-LUMO (4.99–2.90 eV) levels of these molecules with their energy optimized structures generated using DFT, TD-DFT analysis. The fs-TAS spectra of both the molecules exhibited contribution from singlet-singlet excited state absorption followed by transition to triplet states via intersystem crossing, ISC. The lifetimes calculated from obtained kinetics at specific wavelengths using global fitting demonstrated slow singlet to triplet state intersystem crossing in ImCuPc (decay rate of 1.6 × 108 s−1) and ImZnPc (decay rate of 1.4 × 108s−1). The ns-TAS studies established long lived triplet states in both the molecules with ImCuPc depicting a slightly higher triplet lifetime of ~1.4 μs over ImZnPc with a triplet lifetime of ~1.2 μs The triplet quantum yields (φT) were calculated to be 0.51 for ImCuPc while it was 0.27 for ImZnPc suggesting ImCuPc to be a better photosensitizer (PS) over ImZnPc. We believe the intramolecular D-π-A interaction is stronger in ImCuPc resulting in higher triplet yield. Third-order NLO studies performed at a non-resonant excitation of 800 nm (~50 fs, 1 kHz pulses) demonstrated ImZnPc had a larger two-photon absorption cross-section (994 GM), possibly due to heavy atom effect, while ImCuPc was found to possess superior n2 (3.7 × 10−15 cm2/W). The slightly superior nonlinear optical (NLO) performance of ImCuPc over ImZnPc could also possibly be due to lower energy gap and Copper's open 3d shells as opposed to full 3d shell in Zinc which overlaps with Pc 2p shells making it more active.

Functionalization of Zirconium‐Based Metal–Organic Layers with Tailored Pore Environments for Heterogeneous Catalysis

AbstractIntriguing properties and functions are expected to implant into metal–organic layers (MOLs) to achieve tailored pore environments and multiple functionalities owing to the synergies among multiple components. Herein, we demonstrate a facile one‐pot synthetic strategy to incorporate multiple functionalities into stable zirconium MOLs via secondary ligand pillaring. Through the combination of Zr6‐BTB (BTB=benzene‐1,3,5‐tribenzoate) layers and diverse secondary ligands (including ditopic and tetratopic linkers), 31 MOFs with multi‐functionalities were systematically prepared. Notably, a metal–phthalocyanine fragment was successfully incorporated into this Zr‐MOL system, giving rise to an ideal platform for the selective oxidation of anthracene. The organic functionalization of two‐dimensional MOLs can generate tunable porous structures and environments, which may facilitate the excellent catalytic performance of as‐synthesized materials.

Functionalization of Zirconium-Based Metal-Organic Layers with Tailored Pore Environments for Heterogeneous Catalysis.

Intriguing properties and functions are expected to implant into metal-organic layers (MOLs) to achieve tailored pore environments and multiple functionalities owing to the synergies among multiple components. Herein, we demonstrate a facile one-pot synthetic strategy to incorporate multiple functionalities into stable zirconium MOLs via secondary ligand pillaring. Through the combination of Zr6 -BTB (BTB=benzene-1,3,5-tribenzoate) layers and diverse secondary ligands (including ditopic and tetratopic linkers), 31 MOFs with multi-functionalities were systematically prepared. Notably, a metal-phthalocyanine fragment was successfully incorporated into this Zr-MOL system, giving rise to an ideal platform for the selective oxidation of anthracene. The organic functionalization of two-dimensional MOLs can generate tunable porous structures and environments, which may facilitate the excellent catalytic performance of as-synthesized materials.

Photophysical and nonlinear optical properties of the positional isomers of 4-(4-tertbutylphenoxy) substituted cobalt, nickel and copper phthalocyanines

This paper reports on the third order nonlinear optical properties of cobalt, nickel and tetrakis(4-terbutylphenoxy)phthalocyaninatocopper(II) isomers, using the Z-scan technique. Metal-free isomers were found to have high nonlinear absorption coefficient (β) values compared to the metalated isomers. Metal-free C2v isomer was found to have the highest β value of 1.52 × 10−10 mMW−1 in THF. All the metal-free and metal phthalocyanine isomers nonlinear properties were found to be dependent on the singlet state absorption. Imaginary second order nonlinear hyperpolarizability (Im[γ]), ground state cross section (σg), excited states cross sections (σs and σt) and two photon absorption (TPA) cross section (σTPA) values are reported in this work. The five-energy level model rate equations were used to model the nonlinear response and absorption cross sections.

Synthesis and Characterization of New Imidazole Phthalocyanine for Photodegradation of Micro-Organic Pollutants from Sea Water

In this study, a series of new metal phthalocyanines with imidazole function MPc(Imz) (M: Cd, Hg, Zn and Pd) were synthesized to improve the photocatalyst performances. All physical properties such as total energy, HOMO, LUMO energies of MPc(Imz), as well as their vibrational frequencies have been determined by DFT method using B3LYP theory level at 6-311G (d, p) and sdd basis set. The gap of energy level between work function (WF) of ITO and LUMO of PdPc(Imdz) was 1.53 eV and represents the highest barrier beneficial to electron injection compared to WF of ZnPc(Imz), HgPc(Imz), and CdPc(Imz). Furthermore, the PdPc(Imdz) thin films on indium tin oxide (ITO) glass were prepared by spin coating and vacuum evaporation technique, and were characterized by X-ray diffraction (XRD), surface electron morphology (SEM), atomic force microscopy (AFM), and UV–Vis spectroscopy. The photocatalytic activity of the ITO/glass supported thin films and degradation rates of chlorinated phenols in synthetic seawater, under visible light irradiation were optimized to achieve conversions of 80–90%. Experiments on synthetic seawater samples showed that the chloride-specific increase in photodegradation could be attributed to photochemically generated chloride radicals rather than other photoproduced reactive intermediates [e.g., excited-state triplet PdPc(Imz) (3PdPc(Imz)*), reactive oxygen species]. The major 2,3,4,5-Tetrachlorophenol degradation intermediates identified by gas chromatography-mass spectrometry (GC/MS) were 2,3,5-Trichlorophenol, 3,5-dichlorophenol, dichlorodihydroxy-benzene and 3,4,5-trichlorocatechol.

Synthesis and characterization of metal phthalocyanine bearing carboxylic acid anchoring groups for nanoparticle dispersion and their application to color filters

The color filter is an integral part of the white-OLED display, LCD, and CMOS image sensor. This study aimed to improve the color property and thermal stability of a dye-based color filter. For this purpose, the dispersed-dye-based color filter was developed using dye dispersions. Six metal (Cu, Zn) phthalocyanine dyes bearing bulky benzoic acid groups and chlorine were synthesized and their optimized molecular structures, electrostatic potential surfaces, optical properties, thermal stability, and dispersion properties were determined using computational modeling, UV–Vis spectrometry, TGA, and DLS. The synthesized dyes showed suitable spectral properties and thermal stability for green color filters. Among the dyes, polychloro zinc phthalocyanine had superior dispersion properties owing to its distorted geometric structure. A dispersant containing both amine and ammonium groups as anchors was effective in dispersing the dyes. The color filters with the dye dispersions were prepared by spin-coating. As the bulkiness of the dye increased, their dispersibility was enhanced but their thermal stability decreased. On the other hand, it was observed that the higher the dispersibility of the dye, the superior the color properties and the smaller the thickness of the films. All color filters showed better stability than the traditional soluble-dye-based color filter. This study confirmed that the dispersed-dye-based color filter with fine dye particles exhibits superior stability compared with the dye-based color filter, without compromising color properties.

Highly sensitive and selective sensing of acetone and hydrogen sulfide using metal phthalocyanine – carbon nanotube hybrids

Noncovalent functionalization of carbon nanotubes with metal phthalocyanine has great potential for sensor nanodevices, nevertheless, some aspects of their electron transport mechanism behind the sensing properties have not been understood yet. Here, we evaluate the sensing performance of metal phthalocyanine – carbon nanotube hybrids for acetone and hydrogen sulfide (H2S) detection in terms of sensitivity and selectivity, using density functional theory and the non-equilibrium Green’s function method. We systematically investigated the effects of central transition metal atoms (Fe, Co, and Mn) of metal phthalocyanine with different chiralities (quasi-metallic CNT (9,0) zigzag and metallic CNT(5,5) armchair) of single-walled carbon nanotubes and tuning the gate voltages making this nanosensor highly sensitive and selective to acetone and H2S.

Copper (II) phthalocyanines: Electrode modification and sensing studies

Metal phthalocyanine complexes have been used as electro catalysts in various reactions. Chemically inert and thermally stable Para chloro phenyl [1,3,4] oxadiazole substituted copper phthalocyanine was used for the determination of dopamine and ascorbic acid. Experiments revealed that the compound possesses strong electro catalytic activity towards the oxidation of dopamine and ascorbic acid. The modified carbon paste electrode (MCPE) has talented features such as simplicity of electrode preparation, high stability and distinct advantage of simple polishing. Also there was no leaching or discharge of electrode because of insoluble nature of phthalocyanine in aqueous solution and hence a single electrode surface can be used for multiple analytical determinations.

Degradation of carbamazepine by MWCNTs-promoted generation of high-valent iron-oxo species in a mild system with O-bridged iron perfluorophthalocyanine dimers

Metal phthalocyanine has been extensively studied as a catalyst for degradation of carbamazepine (CBZ). However, metal phthalocyanine tends to undergo their own dimerization or polymerization, thereby reducing their activity points and affecting their catalytic properties. In this study, a catalytic system consisting of O-bridged iron perfluorophthalocyanine dimers (FePcF16-O-FePcF16), multi-walled carbon nanotubes (MWCNTs) and H2O2 was proposed. The results showed MWCNTs loaded with FePcF16-O-FePcF16 can achieve excellent degradation of CBZ with smaller dosages of FePcF16-O-FePcF16 and H2O2, and milder reaction temperatures. In addition, the results of experiments revealed the reaction mechanism of non-hydroxyl radicals. The highly oxidized high-valent iron-oxo (Fe(IV)=O) species was the main reactive species in the FePcF16-O-FePcF16/MWCNTs/H2O2 system. It is noteworthy that MWCNTs can improve the dispersion of FePcF16-O-FePcF16, contributing to the production of highly oxidized Fe(IV)=O. Then, the pathway of CBZ oxidative degradation was speculated, and the study results also provide new ideas for metal phthalocyanine-loaded carbon materials to degrade emerging pollutants.

Collective Dipole‐Dominated Doping of Monolayer MoS2: Orientation and Magnitude Control via the Supramolecular Approach

AbstractMolecular doping is a powerful, tuneable, and versatile method to modify the electronic properties of 2D transition metal dichalcogenides (TMDCs). While electron transfer is an isotropic process, dipole‐induced doping is a collective phenomenon in which the orientation of the molecular dipoles interfaced to the 2D material is key to modulate and boost this electronic effect, despite it is not yet demonstrated. A novel method toward the molecular functionalization of monolayer MoS2 relying on the molecular self‐assembly of metal phthalocyanine and the orientation‐controlled coordination chemistry of axial ligands is reported here. It is demonstrated that the subtle variation of position and type of functional groups exposed on the pyridinic ligand, yields a molecular dipole with programed magnitude and orientation which is capable to strongly influence the opto‐electronic properties of monolayer MoS2. In particular, experimental results revealed that both p‐ and n‐type doping can be achieved by modulating the charge carrier density up to 4.8 1012 cm−2. Density functional theory calculations showed that the doping mechanism is primarily resulting from the effect of dipole‐induced doping rather than charge transfer. The strategy to dope TMDCs is a highly modulable and robust, and it enables to enrich the functionality of 2D materials‐based devices for high‐performance applications in optoelectronics.

Metal Phthalocyanine-Derived Single-Atom Catalysts for Selective CO2 Electroreduction under High Current Densities.

Single-atom catalysts (SACs) with atomically dispersed metal sites in nitrogen-doped carbon matrices (M-N/C) have been identified as promising candidates for the electrocatalytic CO2 reduction reaction (CO2RR). However, recent studies aiming at economic viability have been inhibited by the low faradaic efficiency (FE) and instability under high current density. Herein, we report a series of SACs derived from cyano-substituted metal phthalocyanines (MePc-CN) in ZIFs (denoted as Me-SACs (Pc)). These phthalocyanine molecules enable the efficient construction of SACs, affording higher metal loading and less variation when compared with their counterparts from metal nitrates (denoted as Me-SACs (S)). Thus, Me-SACs (Pc) exhibit higher activities and selectivities than Me-SACs (S) in H-cell measurements. In gas-diffusion electrode (GDE) setups, the unstable Fe-SAC (Pc) shows only a 50% FE of CO (FEco) at -100 mA cm-2. In contrast, Ni-SAC (Pc) exhibits a higher FEco of >96% at current densities from -10 to -200 mA cm-2 and can stably operate for over 16 h at -200 mA cm-2. The performances of Ni-SAC (Pc) are comparable to those of precious metal catalysts and the best SACs reported so far, representing a promising candidate for practical electrolyzer devices for CO2RR.

Screen-Printed Electrodes Modified with Metal Phthalocyanines: Characterization and Electrocatalysis in Chlorinated Media.

Metal phthalocyanines are well-known sensing phases with applications in different scientific fields due to their interesting properties. Detailed characterization by Raman spectroscopy was performed in order to study the shifting of the vibrational bands related to the coordination sphere of each metal phthalocyanine. In this work, a study involving the use of screen-printed electrodes (SPEs) with various metal phthalocyanines to electrochemically detect and quantify chlorine (Cl2) gas is presented. The Cl2 gas was generated in-situ via oxidation of the chloride present in form of aqueous salt solutions. The developed method offers not only the possibility to quantify chlorine, but also to discriminate among several chlorinated species due to the changes observed in the voltammetric profiles associated with the interaction between the specie assayed and the phthalocyanine metallic center. Optimization of detecting parameters was also performed to apply this procedure for the quantification of chlorine generated from commercial chlorine tablets. The development of this proof of concept shows interesting possibilities and easy-to-use applications with novel on metal phthalocyanines based SPE sensors.

Promoted Deposition of Three-Dimensional Li2S on Catalytic Co Phthalocyanine Nanorods for Stable High-Loading Lithium-Sulfur Batteries.

The sulfur redox in Li-S batteries involves a complex sequence of solid-liquid-solid conversions, and reaction catalysis has recently become a focused area for further advancement. The deposition of solid Li2S from liquid Li2S4 contributes to three-quarters of the total theoretical capacity and is therefore of great significance over the entire cathode reaction. This study demonstrates a cathode material composed of carbon nanofibers decorated with catalytic Co phthalocyanine nanorods (CoPc@CNF), which are highly effective in promoting the deposition of Li2S in three-dimensional (3D) fine particles rather than 2D thin films. This significantly alleviates cathode passivation during cell charge and discharge, leading to obviously improved sulfur utilization and cycling stability for high loading cathodes. DFT calculations indicate that the promoted 3D deposition of Li2S is related to the facilitated migration of deposition precursors (Li2S4 and Li-ions) to migrate on the CoPc nanorods. Lithium-sulfur (Li-S) pouch cells were prepared with high specific (954 mAh g-1), areal (4.8 mAh cm-2), and total (235 mAh) capacities achieved at 0.5 C under high sulfur content. As metal phthalocyanines possess a high structural variability, this study provides opportunities to the design of a new class of Li-S cathode materials.