Transition Metal Phthalocyanines Research Articles

Modified reverse degree descriptors for combined topological and entropy characterizations of 2D metal organic frameworks: applications in graph energy prediction.

Topological descriptors are widely utilized as graph theoretical measures for evaluating the physicochemical properties of organic frameworks by examining their molecular structures. Our current research validates the usage of topological descriptors in studying frameworks such as metal-butylated hydroxytoluene, NH-substituted coronene transition metal, transition metal-phthalocyanine, and conductive metal-octa amino phthalocyanine. These metal organic frameworks are crucial in nanoscale research for their porosity, adaptability, and conductivity, making them essential for advanced materials and modern technology. In this study, we provide the topological and entropy characterizations of these frameworks by employing robust reverse degree based descriptors, which offer insightful information on structural complexities. This structural information is applied to predict the graph energy of the considered metal organic frameworks using statistical regression models.

A prediction of high temperature magnetic coupling in transition metal phthalocyanines.

In spintronics, a perennial goal has been the generation of organic spin-bearing semiconductor materials with magnetic ordering stable at room temperature. To this end, the class of transition metal phthalocyanines has shown much promise in fulfilling this ambition. In particular, alpha-phase cobalt (II) phthalocyanine (α-CoPc) exhibits strong antiferromagnetic exchange interactions producing a long range order up to ∼100K. However, the underlying mechanism by which this magnetic interaction proceeds is not well understood. In this report, a simple mechanism has been proposed based on the Hubbard Hamiltonian, which elucidates the exchange coupling in α-CoPc. The mechanism provides stipulations for increasing the magnetic coupling, and this directs to a proposal that substitution of the central cobalt ion for rhodium will lead to a significant increase in coupling strength. The strength of this exchange interaction has been evaluated using broken symmetry hybrid exchange density functional theory and indicates that the novel rhodium (II) phthalocyanine system is indeed predicted to exhibit significantly stronger magnetic ordering. This study, therefore, identifies the coupling mechanism in α-CoPc as primarily attributable to kinetic exchange, explains its previously reported strong coupling relative to its first-row transition metal counterparts, and suggests that rhodium (II) phthalocyanine is likely to exhibit stable magnetic ordering at room temperature.

Charge-Transfer Spectroscopy and Electrochemistry of Transition-Metal Phthalocyanines

Charge-transfer spectroscopy of the selected transition-metal phthalocyanines will be discussed in conjunction with their electrochemical properties. Specifically, UV-Vis and magnetic circular dichroism (MCD) spectra of the PcFe(II)L2, PcRu(II)L2, PcMn(III)LX, and PcCr(III)LX (L is a neutral and X is a monoanionic ligand) will be discussed in terms of their metal-to-ligand (MLCT) and ligand-to-metal (LMCT) charge-transfer spectroscopy determined by the experimental UV-Vis and MCD as well as theoretical (time-dependent density functional theory) methods. Lever's EL scale was used to predict and correlate the MLCT and LMCT transitions in transition-metal phthalocyanines.

Modulating the coordination environment and metal choice in carbon buckypapers supported metal phthalocyanines for enhanced electrocatalytic carbon dioxide reduction

In the search of versatile electrocatalysts for the electrochemical reduction of carbon dioxide (CO2RR), different transition metal phthalocyanines (MPc, where M=Fe, Co, Ni and Cu) have been immobilized by an easy and scalable wet impregnation on carbon nanotubes (CNTs) in the form of buckypaper (BP). Both the nature of the metal and the surface chemistry of the carbon support were found to play a pivotal role in determining their CO2RR efficiency and selectivity. We disclose here a potentiodynamic strategy for the controlled surface modification of BP with N- and P-containing polymeric species as a simple heterogenization strategy for molecular catalysts, enabling to easily tune their electrocatalytic performance. Syngas (mixture of H2 and CO) was obtained as the main product from CO2RR using FePc, CoPc and NiPc as electrocatalysts on functionalized (BPf) or non-modified BP. In contrast, CuPc was found to mainly catalyze the hydrogen evolution reaction (HER), with small amounts of formate as the only CO2RR product. It is possible to modulate the H2/CO ratio in the final product through the appropriate selection of the metal in MPc, the modification of the coordination environment by the controlled functionalization of the carbon support and the adjustment of the operating conditions. In particular, H2/CO ratios in a range between 0.17 and 1.28 have been obtained with good stability during electrolysis. Among all the MPc studied, CoPc surfaced as the most promising candidate for the reduction of CO2 to CO and H2 production, a finding substantiated by computational studies highlighting the positive impact of phosphate ligands on CoPc. This strategy outlines the starting line of a potential route toward the controlled generation of CO2RR-related products.

Catalytic Activity of MWCNTs Doped with Some Transition Metal Phthalocyanines and Modified with Silver in ORR

Catalytic Activity of MWCNTs Doped with Some Transition Metal Phthalocyanines and Modified with Silver in ORR

Spin filtering, magnetoresistance and seebeck effects in phthalocyanine based molecular junctions between phosphorus nanoribbon electrodes

This research utilized the non-equilibrium Green’s function (NEGF) method combined with density functional theory (DFT) to explore spin transport in binuclear transition metal phthalocyanine (TMPc) molecules between black phosphorus nanoribbon electrodes. The device achieves near 100% SFE with ferromagnetic coupling of Manganese phthalocyanine (MnPc) and Iron phthalocyanine (FePc). When the MnPc and FePc molecules exhibited anti-ferromagnetic coupling, with the transports in the two spin channels significantly smaller than in the ferromagnetic coupling scenario, demonstrating giant magnetoresistance effects. MnPc shows high Seebeck polarization at 149 K, while FePc maintains it at a low temperature. This research opens new avenues for designing molecular spintronic devices with two-dimensional electrodes.

Computation of reverse neighbourhood degree-based topological indices for the transition metal phthalocyanine polymers (poly-TMPc)

In this article, we discuss the reverse neighbourhood degree-based topological indices for the transition metal phthalocyanine polymers (poly- TMPc). Degree-based topological indices have been extensively studied and linked to a variety of chemical properties. An even more recently established methodology for assessing chemical systems and geometries is the use of numerical descriptors based on the degree of definition defined by the reverse-degree concept technique. It highlights molecular characteristics as numerical descriptors based on the reverse-degree concept’s degree of definition and delivers numerical descriptors in algebraic form. On the other hand, due to their high catalytic activity, photostability, resistance to severe environments, and adaptable properties, transition metal phthalocyanines are a fascinating class of organic semiconductors. Furthermore, different types of reverse neighbourhood topological indices, such as the augmented Zagreb index, first and second Zagreb indexes, and Randi ć indexes, are defined and used to assess the complexity, stability, and other properties of poly-TMPc(m,n).

Electrochromic Smart Window Based on Transition-Metal Phthalocyanine Derivatives.

Phthalocyanines have been widely investigated as electrochromic materials because of their large conjugated structure. However, they have shown limited applicability due to their complex electrochromism mechanism and low solubility in common organic solvents. Replacement of central metal ions in phthalocyanines affects their stability and is responsible for various electrochromic phenomena, such as color change. Herein, the relationship between the electron d-orbital arrangement in the outermost layer of transition metals and the electrochromic stability of phthalocyanine derivatives has been investigated. An enhanced solubility of phthalocyanines in organic solvents was obtained through the introduction of quaternary tert-butyl substitution. Electrochromic devices fabricated with transition-metal phthalocyanine derivatives showed high response speeds and good stability. The fast color-switching feature between blue/green and blue/purple makes it a promising candidate for smart windows and adaptive camouflage applications.

Electronic structures of two-dimensional covalent organic frameworks based on a series of period 4 transition metal phthalocyanines and ethynyl moieties

Two-dimensional metal–phthalocyanine-based covalent organic frameworks (MPc COFs) have unique electronic properties to be applied in electrocatalytic and photochemical reactions.

Mono-, bi- and tri-metallic Fe-based platinum group metal-free electrocatalysts derived from phthalocyanine for oxygen reduction reaction in alkaline media.

In this manuscript, a comprehensive study is presented on Fe-based electrocatalysts with mono, bi, and tri-metallic compositions, emphasizing the influence of processing-structure correlations on the electrocatalytic activity for the oxygen reduction reaction (ORR) in the alkaline medium. These electrocatalysts were synthesized through the mixing of transition metal phthalocyanines (TM-Pc) with conductive carbon support, followed by controlled thermal treatment at specific temperatures (600 °C and 900 °C). An extensive analysis was conducted, employing various techniques, including X-ray Absorption Spectroscopy (XAS), Transmission Electron Microscopy (TEM), and X-ray Diffraction (XRD), providing valuable insights into the structural characteristics of the synthesized nanoparticles. Importantly, an increase in the Fe-Pc weight percentage from 10% to 30% enhanced the ORR activity, although not proportionally. Furthermore, a comparative analysis between mono, bi, and tri-metallic samples subjected to different functionalization temperatures highlighted the superior electrocatalytic activity of electrocatalysts functionalized at 600 °C, particularly Fe 600 and Fe-Ni-Cu 600. These electrocatalysts featured Eon values of 0.96 V vs. RHE and E1/2 values of 0.9 V vs. RHE, with the added benefit of reduced anionic peroxide production. The potential of these Fe-based electrocatalysts to enhance ORR efficiency is underscored by this research, contributing to the development of more effective and sustainable electrocatalysts for energy conversion technologies.

The trials and triumphs of modelling X-ray absorption spectra of transition metal phthalocyanines.

This study explores the electronic structure of Co, Fe and Mn phthalocyanines (TMPcs) as well as their perfluorinated counterparts through a series of electronic structure calculations utilizing multireference methods and by simulating their metal L-edge and ligand (nitrogen and fluorine) K-edge X-ray absorption spectra (XAS) in an angle-resolved manner. Simulations targeting different ground-state symmetries, where relevant, have been conducted to observe changes in the N K-edge lineshape. The applicability of the quasi-degenerate formulation of n-electron valence state perturbation theory (QD-NEVPT2) for L-edge X-ray absorption spectroscopy (XAS) is evaluated, alongside the use of a restricted active space (RAS) formalism to describe the final-state multiplets generated by L-shell X-ray processes. Our findings provide valuable insights into the electronic properties of TMPcs, in particular with respect to the effect of fluorination, and demonstrate the broad applicability of various formulations of NEVPT2 in spectral simulations. Moreover, this study highlights the utility of manual truncation of the configuration spaces in order to allow for large active orbital spaces in aforementioned calculations.

Theoretical Screening, Regulation, and Prediction of Transition Metal Phthalocyanine Electrocatalysts for NO Reduction into NH3

Theoretical Screening, Regulation, and Prediction of Transition Metal Phthalocyanine Electrocatalysts for NO Reduction into NH₃

Revealing a Double-Volcano-Like Structure-Activity Relationship for Substitution-Functionalized Metal-Phthalocyanine Catalysts toward Electrochemical CO2 Reduction.

Electron-donating/-withdrawing groups (EDGs/EWGs) substitution is widely used to regulate the catalytic performance of transition-metal phthalocyanine (MPc) toward electrochemical CO2 reduction, but the corresponding structure-activity relationships and regulation mechanisms are still ambiguous. Herein, by investigating a series of substitution-functionalized MPc (MPc-X), this work reveals a double-volcano-like relationship between the electron-donating/-withdrawing abilities of the substituents and the catalytic activities of MPc-X. The weak-EDG/-EWG substitution enhances whereas the strong-EDG/-EWG substitution mostly lowers the CO selectivity of MPc. Experimental and calculation results demonstrate that the electronic properties of the substituents influence the symmetry and energy of the highest occupied molecular orbitals of MPc-X, which in turn determine the CO2 adsorption/activation and lead to diverse CO2 reduction pathways on the EWG or EDG substituted MPc via different CO2 adsorption modes. This work provides mechanism insights that could be guidance for the design and regulation of molecular catalysts.

Fe phthalocyanine stabilized on phosphorous-doped multi-defective carbon nanoribbons as oxygen reduction electrocatalysts

Coordination polymers can be utilized as ideal precursors due to their ability to change their growth behavior and topological structure through solvent-induced effects. In this work, nanostrip-like crystalline particles, transformed from interchangeable indium-based coordination polymers (InOF-25/26), are treated to synthesize phosphorus-doped multi-defective carbon nanoribbons for efficiently anchoring iron phthalocyanine. The obtained FePc-Fe2P@25-CNR electrocatalyst exhibits a superior half-wave potential of 0.899 V and a large diffusion current density of 5.152 mA cm−2 in oxygen reduction reaction (ORR). Meanwhile, it also shows excellent stability in homemade Zn-air batteries with satisfactory charge/discharge durability over 100 cycles. In this case, the ORR performance can be improved by phosphating the carbon surface, reinforcing tight bonding with transition metal phthalocyanines, and inducing charge migration to increase the electrocatalysis kinetics, which is further validated by relevant theoretical calculation. This synthetic strategy combines structurally variable coordination polymers with metallomacrocyclic molecules, exploiting a feasible pathway for the preparation of high-performance electrochemical catalysts.

Oxygen Radical Anion Substituted Iron Phthalocyanine as an Effective Redox Mediator for Li-O2 Batteries.

Transition metal phthalocyanines are potential soluble redox mediators for Li-O2 batteries. In this work, effective strategies to control the redox potentials and activities of iron phthalocyanine (FePc) based redox mediators are designed by the introduction of electron-withdrawing or electron-donating groups. Substituted electron-donating groups can shift the oxidation potential of FePc to a higher energy level, consequently reducing the charging voltage of Li-O2 batteries. Especially, oxygen radical anion (-O-) modified FePc (FePc-O-) shows the most significant improvement to the oxygen reduction and evolution reactions of Li-O2 batteries. Electronic analysis indicates that -O- substitution can break the symmetry of electronic structures of FePc which further tunes the reduction of O2 and the oxidation of Li2O2. Detailed reaction mechanisms of (FePc-O-)-mediated Li-O2 batteries are proposed based on first-principles molecular dynamics simulations and thermodynamic free energy calculations.

Interaction of Carbon Monoxide with Transition Metal Phthalocyanines

Interaction of Carbon Monoxide with Transition Metal Phthalocyanines

Dynamical Screening of Local Spin Moments at Metal–Molecule Interfaces

Transition-metal phthalocyanine molecules have attracted considerable interest in the context of spintronics device development due to their amenability to diverse bonding regimes and their intrinsic magnetism. The latter is highly influenced by the quantum fluctuations that arise at the inevitable metal-molecule interface in a device architecture. In this study, we have systematically investigated the dynamical screening effects in phthalocyanine molecules hosting a series of transition-metal ions (Ti, V, Cr, Mn, Fe, Co, and Ni) in contact with the Cu(111) surface. Using comprehensive density functional theory plus Anderson's Impurity Model calculations, we show that the orbital-dependent hybridization and electron correlation together result in strong charge and spin fluctuations. While the instantaneous spin moments of the transition-metal ions are near atomic-like, we find that screening gives rise to considerable lowering or even quenching of these. Our results highlight the importance of quantum fluctuations in metal-contacted molecular devices, which may influence the results obtained from theoretical or experimental probes, depending on their possibly material-dependent characteristic sampling time-scales.

Electronic properties of two-dimensional kagome lattice based on transition metal phthalocyanine heterojunctions

Transition metal phthalocyanine molecules serve as building blocks for two-dimensional (2D) metal-organic frameworks with potential applications in optics, electronics, and spintronics. Previous theoretical studies predicted that a two-dimensional transition metal phthalocyanine framework with kagome lattice (kag-TMPc) has stable magnetically ordered properties, which are promising for spintronics and optoelectronics. However, there is a lack of studies on their heterojunctions, which can effectively tune the properties through interlayer coupling despite its weak nature. Here we use the density functional theory (DFT) to calculate the electronic properties of eight representative 2D kag-TMPc vertical heterojunctions with two different stackings (AA and AB) and interlayer distances. We find that most of the kag-MnPc-based heterojunctions can maintain the electronic properties of monolayer materials with low bandgap. The kag-MnPc/ZnPc is a ferromagnetic semiconductor with magnetic exchange energy above 40 meV, regardless of stacking sequences; the electronic properties of kag-MnPc/MnPc heterojunctions change from magnetic half-metal to magnetic semiconductor during the transition from AA stacking to AB stacking. Interestingly, the AB stacked kag-CuPc/CoPc heterojunction is a ferromagnetic semiconductor, and the spin-polarized energy band arrangement changes with the layer spacing: when the layer spacing is as long as the equilibrium distance, the spin-up and spin-down energy bands are aligned as type II; when the layer spacing increases by 0.2 Å, the spin-up energy bands are aligned as type-I energy bands, while the spin-down energy bands are aligned as type-II energy bands. This distance-dependent spin properties can realize magnetic optoelectronic “switching” and has potential applications in new magnetic field modulated electromagnetic and optoelectronic devices.

Interaction mechanism of transition metal phthalocyanines on transition metal nitride supports

We investigated the electronic interactions between transition metal phthalocyanine (TMPc’s) on a refractory transition metal nitride support, specifically copper phthalocyanine (CuPc) on titanium nitride (TiN). X-ray Photoelectron Spectroscopy (XPS) results suggest a presence of a few nanometer native oxide layer on the surface of the TiN nanoparticles, which consists of TiN, TiO2, and Titanium oxynitrides (TixOyNz). A TiNCuPc nanocomposite was synthesized via a simple mixing method due to the strong binding between CuPc and TiN confirmed by density functional theory (DFT) calculations. Both XPS data and DFT calculations revealed an electron transfer from TiN substrate to CuPc molecule. The nature of charge transfer is not influenced by the presence of an oxide layer on the surface of TiN. Substantial deviations are however found between photoelectron emission microscopy (PEEM) measured work function for TiN (4.68 eV) and theoretically calculated work function for pristine stoichiometric TiN (2.63 eV). This behavior is attributed to the presence of an oxide layer on the TiN surface. TiNCuPc composite system has a work function value between those of TiN and CuPc. Our studies open up an opportunity to apply a new class of materials based on transition metal phthalocyanine/transition metal nitride composites to catalysis and optoelectronic devices.

Influence of central atoms on the catalytic effect of transition metal phthalocyanines in Li-S battery cathodes

Transition metal phthalocyanines (MPc) with different central metal atoms of Co(II), Fe(II), Ni(II), Mn(II) and Cu(II) were loaded on carbon nanofibers to act as the cathode catalytic materials for Li-S batteries. The influence of central atoms on the catalytic activity was explored. Higher specific capacities and cycling stability were achieved with CoPc and FePc, exhibiting higher catalytic activities for the oxidation and reduction processes respectively. The MPc molecules all present similar adsorption geometries with Li2S6 and adsorption energy was found to be unsuitable to explain the difference. The presence of unoccupied dz2 orbitals in Co and Fe might be the origin for the higher catalytic activities.