Cobalt Phthalocyanine Derivatives Research Articles

Tuning the Interfacial Electronic Structure of MoS2 by Adsorption of Cobalt Phthalocyanine Derivatives

Tuning the Interfacial Electronic Structure of MoS₂ by Adsorption of Cobalt Phthalocyanine Derivatives

3D hybrid materials based on zinc and cobalt phthalocyanine derivatives bearing terminal ethynyl substituents as active layers for chemiresistive gas sensors

Porous 3D hybrid materials (SWCNT/CoPc and SWCNT/ZnPc) were prepared by the reaction between single walled carbon nanotubes (SWCNT) functionalized with azido groups and ZnPc or CoPc phthalocyanines containing 16 terminal ethynyl groups and characterized by various physical methods. It was shown by thermogravimetric analysis (TGA) that the number of CoPc molecules attached on the SWCNT surface was one CoPc molecule per 115 carbon atoms, which is larger than in the case of the SWCNT/ZnPc (one ZnPc molecule per 312 carbon atoms). The prepared hybrids were studied as active layers of chemiresistive sensors for the detecting gaseous H2S at low concentrations (0.1–50 ppm). It was found that the sensor response of SWCNT/CoPc was about 4 times higher than in the case of SWCNT/ZnPc, which correlated well with the larger number of CoPc molecules on the SWCNT surface. The prepared hybrids are promising materials for the creation of fully reversible sensors for the detection of H2S at room temperature. The calculated LOD (3σ/m) of H2S was 18 and 65 ppb for SWCNT/CoPc and SWCNT/ZnPc, respectively.

Cobalt and Iron Phthalocyanine Derivatives: Effect of Substituents on the Structure of Thin Films and Their Sensor Response to Nitric Oxide.

In this work, we study the effect of substituents in cobalt(II) and iron(II) phthalocyanines (CoPcR4 and FePcR4 with R = H, F, Cl, tBu) on the structural features of their films, and their chemi-resistive sensor response to a low concentration of nitric oxide. For the correct interpretation of diffractograms of phthalocyanine films, structures of CoPcCl4 and FePcCl4 single crystals were determined for the first time. Films were tested as active layers for the determination of low concentrations of NO (10-1000 ppb). It was found that the best sensor response to NO was observed for the films of chlorinated derivatives MPcCl4 (M = Co, Fe), while the lowest response was in the case of MPc(tBu)4 films. FePcCl4 films exhibited the maximal response to NO, with a calculated limit of detection (LOD) of 3 ppb; the response and recovery times determined at 30 ppb of NO were 30 s and 80 s, respectively. The LOD of a CoPcCl4 film was 7 ppb. However, iron phthalocyanine films had low stability and their sensitivity to NO decreased rapidly over time, while the response of cobalt phthalocyanine films remained stable for at least several months. In order to explain the obtained regularities, quantum chemical calculations of the binding parameters between NO and phthalocyanine molecules were carried out. It was shown that the binding of NO to the side atoms of phthalocyanines occurred through van der Waals forces, and the values of the binding energies were in direct correlation with the values of the sensor response to NO.

“Substituents optimization” and “push effect” dual strategy for design of cobalt phthalocyanine catalyst on oxygen reduction reaction

Molecular metallocycle electrocatalysts like metalloporphyrins and metallophthalocyanines were found to be effective for oxygen reduction reaction (ORR) due to their M–N4 active sites and large conjugated electronic molecular structures. Herein, the “substituents optimization” strategy combined with “push effect” modification was innovatively employed to target a single Co–N4 active site in three substituted phthalocyaninato cobalt complexes: tetranitrophthalocyaninato cobalt (CoTNPc), tetra(4-nitrophenoxy) phthalocyaninato cobalt (CoTPNPc), and tetraphenoxy phthalocyaninato cobalt (CoTPPc) electrocatalyst, also with 4-phenylpyridine axial coordination on Co–N4 unit. Through substituents screening, the half-wave potential (E1/2) for ORR increases in the order of CoTPNPc (0.75 V) < CoTPPc (0.80 V) < CoTNPc (0.83 V) along with decreased electron-withdrawing ability of their substituents from –OC6H4–NO2, –OC6H5 to –NO2 in the three cobalt phthalocyanine derivatives. CoTNPc with the weakest electron-withdrawing substituent exhibits the best ORR performance among the three compounds. This is attributed to its higher electron delocalization and lifted HOMO energy level with the lower energy barrier in the rate-determining step relative to the other two compounds, which facilitate the electron transfer and reduction of oxygen as evidenced by XPS, UPS, and DRS analysis combined with DFT calculations. Further coordination of 4-phenylpyridine shifts the E1/2 up to 0.78, 0.82, and 0.85 V for CoTPNPc, CoTPPc, and CoTNPc. DFT calculations demonstrate that the introduction of the electron-donating phenylpyridine ligand into the cobalt phthalocyanines breaks the symmetry of the Co–N4 center and also raises the electron density of Co sites, which promotes O2 adsorption and improves ORR performance. After comparing the two strategies, the substituents on metallophthalocyanine are more determined by the electroactivity than the axial group, which directly regulates the coordination environment and then the activation barrier of the ORR process. This work provides theoretical and experimental guidance by two coupling strategies for the design of highly active molecular CoPc-based ORR electrocatalysts in the practical application.

Kinetic Study of the Oxidation of Hydrogen Sulfide and Ethyl Mercaptan with Molecular Oxygen in the Presence of an Ammonia Solution of Cobalt Phthalocyanine Derivatives

Kinetic Study of the Oxidation of Hydrogen Sulfide and Ethyl Mercaptan with Molecular Oxygen in the Presence of an Ammonia Solution of Cobalt Phthalocyanine Derivatives

Photocatalytic oxidation of butan-2-ol over multi walled carbon nanotubes/cobalt phthalocynanine composites

ABSTRACT. This study involves synthesis of new substituted of cobalt phthalocyanine derivatives (CoPc) from starting materials naphthalene-1,4,5, tetracarbonic acid dianhydride (NDI) and phthalic anhydride by dry process. Nano composites materials were prepared from multi wall carbon nanotubes (MWCNTs), and MO (Cr2O3-NiO) to yield (MWCNTs/MO) nanocomposite and mixed with cobalt phthalocyanine to yield (MWCNTs/CoPc-MO). These materials were investigated using different analytical and spectrophotometric methods such as FTIR spectroscopy, X-rays diffraction (XRD), and scanning electron microscopy (SEM). Then the activity of these materials was investigated by conducting photocatalytic oxidation of butann-2-ol over a suspension of these composites under irradiation with UV light from middle pressure mercury lamp. The concentration of the produced 2-butanone was followed by spectrophotometric method using 2,4-dinitro phenyl hydrazone which was detected by measuring absorbance at 480 nm. Different reaction conditions and parameters were investigated such as effect of weight of the catalyst, temperature of reaction, reaction period and the effect of pH of reaction mixture.&#x0D;                &#x0D; KEY WORDS: Cobalt phthalocynanine, Nanocomposite, Photocatalytic oxidation of alcohols&#x0D; Bull. Chem. Soc. Ethiop. 2022, 36(1), 197-207.                                                            &#x0D; DOI: https://dx.doi.org/10.4314/bcse.v36i1.16                                                     &#x0D;  

Co2P Embedded into P and N Dual-Doped Carbon Nanotubes and Graphene as a Bifunctional Oxygen Electrocatalyst

The reasonable design of inexpensive and efficient bifunctional electrocatalyst towards oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is still challenging for Zn-air batteries. Herein, a novel and effective design is proposed to fabricate Co2P nanoparticles encapsulated in doped carbon nanotubes and rGO sheets (Co2P/NPCNTs-rGO) through a direct self-catalyzed growth procedure. That is, cobalt phthalocyanine derivatives as the cobalt sources are not only employed to form Co2P nanoparticles, but also used to catalyze the formation of CNTs and rGO. Benefiting from the unique structure and composition, the Co2P/NPCNTs-rGO-800 shows significant OER (overpotential of 420 mV) and ORR (half-wave potential of 0.73 V) properties. Most importantly, the activity parameter of Co2P/NPCNTs-rGO-800 (ΔE=0.92 V) is comparable to that of RuO2(0.91 V) and lower than that of Pt/C (1.05 V), indicating that Co2P/NPCNTs-rGO-800 is of a good comprehensive ORR/OER bifunctional performance. This work provides an effective strategy for the synthesis of outstanding multifunctional catalysts for wider practical applications.

Heterogeneous Nature of Electrocatalytic CO/CO2 Reduction by Cobalt Phthalocyanines.

Molecular catalysts for electrochemical CO2 reduction have traditionally been studied in their dissolved states. However, the heterogenization of molecular catalysts has the potential to deliver much higher reaction rates and enable the reduction of CO2 by more than two electrons. In light of the recently discovered reactivity of heterogenized cobalt phthalocyanine molecules to catalyze CO2 reduction into methanol, direct comparison is needed to uncover the distinct catalytic activity and selectivity in homogeneous catalysis versus heterogeneous catalysis. Herein, soluble cobalt phthalocyanine derivatives were synthesized, and their catalytic activities in the homogeneous solutions were evaluated. The results show that the observed catalytic activities for both CO2 -to-CO and CO-to-methanol conversions in aqueous solutions of the cobalt phthalocyanines are predominantly heterogeneous in nature through the adsorbed species on the electrode.

Ammonia sensing performance of thin films of cobalt(II) phthalocyanine bearing fluorinated substituents

In this work, a new cobalt phthalocyanine derivative bearing 5-(trifluoromethyl)-2-mercaptopyridine substituents (CoPc) was synthesized and characterized. The redox properties of CoPc were studied by cyclic voltammetry (CV) and square wave voltammetry (SWV) methods. The sensing performance of CoPc thin films deposited by spin coating of its solution in ethylacetate was studied against low concentrations of ammonia (0.3 to 50 ppm) by measuring changes in the films’ conductivity at different humidity. It has been shown that the CoPc-based sensor displays an improved ammonia sensing performance in terms of sensitivity, response and recovery times. Ammonia can be detected in the presence of volatile organic vapors, and its detection limit was found to be 0.3 ppm. At the same time, low concentrations of CO2 comparable with the concentrations of ammonia do not influence on the sensitivity of CoPc film to ammonia, however the sensor response noticeably distorts in the presence of high CO2 concentrations in the gas mixture.

Electrochemical Properties of Tetrasubstituted Cobalt Phthalocyanines with Fragments of Benzoic Acid

The method of cyclic voltammetry is used for the first time to study the electrochemical behavior of cobalt phthalocyanine derivatives with fragments of benzoic acid CoPc(4-O–C6H4COOH)4 and CoPc(4- S–C6H4COOH)4 in an aqueous alkaline solution. Comparative analysis is carried out of the electrochemical behavior and change in the electrocatalytic activity of metal phthalocyanines in the reaction of molecular oxygen electroreduction depending on the functional substitution in the macrocycle molecule. In the case of the CoPc(4-O–C6H4COOH)4 and CoPc(4-S–C6H4COOH)4 compounds, central metal ion oxidation (Co2+ → Co3+) and reduction (Co2+→ Co1+) processes and also two successive one–electron stages of phthalocyanine ligand electroreduction are registered. It is shown that the studied cobalt phthalocyanine derivatives manifest electrocatalytic activity in the process of molecular oxygen electroreduction.

Synthesis, electrochemistry and electrocatalytic activity of cobalt phthalocyanine complexes – Effects of substituents for oxygen reduction reaction

The synthesis, characterization, electrochemistry and electrocatalytic activity of the mono (pyridine-4-oxy)-tri (tert-butyl) phthalocyaninato Co(II) (Pc1) and mono (pyridine-4-oxy)-hexa (hexyl) phthalocyaninato Co(II) (Pc2) are reported here. One reversible and one irreversible oxidation couples and two quasi-reversible reduction couples are observed for two complexes on the cyclic voltammograms. Both cobalt phthalocyanine derivatives (CoPcs) and multiwall carbon nanotube (MWCNT) composite (CoPcs/MWCNT) electrodes are coated on glassy carbon electrodes and used as electrocatalysts for oxygen reduction reaction (ORR). The morphology of composite surfaces is characterized using Scanning Electron Microscope (SEM). The results obtained using rotating disk electrode (RDE) reveal that the high catalytic activity is observed with 4e− and mixed 2e− – 4e− ORR mechanisms for Pc1/MWCNT and Pc2/MWCNT hybrid catalysts in alkaline media, respectively. The tert-butyl substituent is more efficient with desired 4e− mechanism on the catalytic activity of the composite electrode compared to the hexyl substituent on the CoPc ring.

Low symmetric metallophthalocyanine modified electrode via click chemistry for simultaneous detection of heavy metals

Beside different methods and materials used to develop electrochemical sensors, the modification of the electrode using click reaction based on metallophthalocyanine (MPc) compounds are shown to improve the stability and sensitivity of the sensor. This work reported the development of electrochemical sensor for mercury (II), Lead (II), copper (II) and cadmium (II) ions detection based on the synthesized novel low symmetry alkyne terminated cobalt Phthalocyanine (CoPc) derivative. Differential pulse stripping voltammetry (DPSV) technique was employed for the first time in simultaneous determination of trace levels of the above metal ions using modified glassy carbon electrode (GCE) via click chemistry. Under the optimum experimental conditions, the anodic peak current is proportional to the concentrations of metal ions over a wide range of 0 to 0.1 mM with nanolevel detection limit of 81.94, 327.71, 55.87 and 347.06 nM and the sensitivity of 866.23 ± 5.48, 215.82 ± 2.16, 1979.48 ± 11.47 and 204.50 ± 1.10 μA/mM for Hg(II), Cu(II), Pb(II) and Cd(II), respectively. The selectivity of the clicked-CoPc modified GCE toward Hg(II), Cu(II), Pb(II), Cd(II) present no interference from these metals ions. The fabricated electrochemical sensor exhibited very good electrochemical properties such as good reproducibility, stability, reusability and is suitable for the detection of heavy metal ions in tap water in our laboratory.

π-Extended hexadeca-substituted cobalt phthalocyanine as an active layer for organic field-effect transistors.

Due to their flexibility and solution applicability, organic field-effect transistors (OFETs) are considered prominent candidates for application in flexible and low-cost devices. A soluble phthalocyaninato cobalt(ii) complex was designed and synthesized based on a hexadeca-substitution pattern by introducing peripheral phenylethynyl groups and non-peripheral n-butoxy groups. The cobalt phthalocyanine derivative was characterized using a wide range of spectroscopic and electrochemical methods, as well as single-crystal X-ray diffraction analysis. An OFET device was fabricated using a spin-coated film of soluble 1,4,8,11,15,18,22,25-octakisbutoxy-2,3,9,10,16,17,23,24-octakis-ethynyl phenyl phthalocyaninato cobalt(ii) with a bottom-gate top-contact device configuration. The transfer and output characteristics were investigated to evaluate the charge carrier mobility. The mechanisms of the leakage current through the gate dielectric were also investigated, which revealed that the dominant leakage current mechanism is Fowler-Nordheim tunneling.

Electrochemical and photovoltaic properties of highly efficient solar cells with cobalt/zinc phthalocyanine sensitizers

The cyclic voltammetry studies indicated that the HOMO and LUMO energy levels of three sensitized metallophthalocyanines could ensure efficient electron injection and thermodynamically favorable dye regeneration. The S-bridged 4-mercaptobenzoic acid substituted cobalt(II) phthalocyanine (4-MKBa-CoPc) sensitized solar cell devices possessed a short-circuit photocurrent density of 9.70 mA/cm2, an open-circuit voltage of 0.88 V, and a fill factor of 0.49, corresponding to an overall conversion efficiency of 4.18% under standard AM 1.5 sun light. The present results demonstrated that the cobalt(II) phthalocyanine derivative had dramatically higher solar cell efficiency value as compared to zinc(II) phthalocyanine and as a linker atom, instead of oxygen linker, sulfur atoms slightly improved solar cell efficiency. The above results indicated that a low cost sensitizer made up of symmetrically substituted phthalocyanine with an earth abundant metal at the inner core can reach sufficiently high solar cell efficiency when compared with the alternative sensitizers for DSSCs applications.

Effects of Substituents on the Electrocatalytic Activity of Cobalt Phthalocyanines when Conjugated to Graphene Quantum Dots

AbstractWe report on the π–π interactions between graphene quantum dots (GQDs) and the following cobalt phthalocyanine derivatives: cobalt monocarboxyphenoxy phthalocyanine (complex 1), cobalt tetracarboxyphenoxyphthalocyanine (complex 2), and cobalt tetraaminophenoxy phthalocyanine (complex 3). The conjugates (conj) with GQDs are represented as 1@GQDs(conj), 2@GQDs(conj) and 3@GQDs(conj), respectively. The resulting phthalocyanine/GQDs conjugates were adsorbed on containing a glassy carbon electrode (GCE) using the drop and dry method. We explore the electrochemical properties of phthalocyanines functionalized with both electron withdrawing groups and electron donating groups when non‐covalently linked to the π‐electron rich graphene quantum dots. GCE/3, GCE/2@GQDs(conj) and GCE/1@GQDs(conj) had the lowest limits of detection (LOD). Sequentially modified electrodes showed less favourable detection limits compared to the conjugates.

Non-covalent associates of metal phthalocyanines: the role of axial ligand and catalytic activity

The problem about the role of the coordinated exobidentate ligand in the formation of dimeric structures of sulfonated cobalt phthalocyanine derivatives is considered. The size of the peripheral substituent of the macrocycle and remoteness of the ionogenic group from the macrocycle play the key role in the formation of dimers of a specified type. As the extension of the peripheral substituent of the macrocycle increases, the stability of dimeric associates of the Н-type decreases and that of the associates formed due to the donor—acceptor interaction (J- and Т-aggregates) increases. The latter can be stabilized by hydrogen bonds at the periphery of the macromolecule. A series of catalytic activity of the macrocycles under study is inverted compared to the series of stability of the H-dimers.

Effect of the solvation properties of the solvent on the formation of associated structures of water-soluble Co(II) phthalocyanines

Self-association processes of sulfonated cobalt phthalocyanine derivatives were studied. The effects of the size of peripheral substituent and the solvation properties of the solvent on the formation of H- and J-aggregates of metal phthalocyanines were demonstrated. The possibility to control the associative equilibrium of metal phthalocyanines via coordination to DABCO was established. The introduction of DABCO was found to induce dissociation of H- and J-aggregates followed by the formation of sandwich type dimers.

Electrode modification using nanocomposites of electropolymerised cobalt phthalocyanines supported on multiwalled carbon nanotubes

A polymer of tetra(4)-(4,6-diaminopyrimidin-2-ylthio) phthalocyaninatocobalt(II) (CoPyPc) has been deposited over a multiwalled carbon nanotube (MWCNT) platform and its electrocatalytic properties investigated side by side with polymerized cobalt tetraamino phthalocyanine (CoTAPc). X-ray photoelectron spectroscopy, scanning electron microscopy and cyclic voltammetry studies were used for characterization of the prepared polymers of cobalt phthalocyanine derivatives and their nanocomposites. l-Cysteine was used as a test analyte for the electrocatalytic activity of the nanocomposites of polymerized cobalt phthalocyanines and multiwalled carbon nanotubes. The electrocatalytic activity of both polymerized cobalt phthalocyanines was found to be superior when polymerization was done on top of MWCNTs compared to bare glassy carbon electrode. A higher sensitivity for l-cysteine detection was obtained on CoTAPc compared to CoPyPc.

Investigation of structural, optical and electrical properties of a new cobalt phthalocyanine thin films with potential applications in perchlorate sensor

Optical, structural and electrical properties of new cobalt phthalocyanine derivatives (Co(II)Pc-AP) thin films have been investigated. The Raman spectroscopy study shows the different vibrations bands corresponding to the metallophthalocyanine. The cobalt-phthalocyanine derivative films exhibit absorption spectra with a resolved electronic structure in the UV–vis range and the energy gap was determined by the Tauc method. Electrical properties of the ITO/Co(II)Pc-AP/Al structure have been investigated by I–V characteristics and impedance spectroscopy measurements. The conduction is governed by space-charge-limited current (SCLC) mechanism. The impedance spectroscopy study showed a hopping transport process, which is a typical behavior of disordered materials. The electrical characteristics of the devices were modeled by a single parallel resistor and capacitor network in series with a resistance.

Comparative electrocatalytic studies of nanocomposites of mixed and covalently linked multiwalled carbon nanotubes and 4-(4,6-diaminopyrimidin-2-ylthio) phthalocyaninato cobalt(II)

Electrocatalytic behavior of 4-(4,6-diaminopyrimidin-2-ylthio) phthalocyaninato cobalt(II) (CoPyPc) when mixed or covalently mixed to multiwalled carbon nanotubes (MWCNTs) is reported. Infra-red spectroscopy was used to confirm amide linkage of the covalently linked nanocomposite. Rotating disk electrode (RDE) and cyclic (CV) voltammetry studies were used for the electrochemical characterization of the prepared phthalocyanine and MWCNT nanocomposite. The electrocatalytic effects of the nanocomposites of the cobalt phthalocyanine derivative were then investigated towards l-cysteine oxidation using both RDE and CV experiments, and the electrocatalytic performance of the covalently linked cobalt phthalocyanine-MWCNT was found to be superior over the mixed nanocomposite.