Transition Metal Phthalocyanines Research Articles

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.

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.

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.

Transition Metal Phthalocyanines as Redox Mediators in Li-O2 Batteries: A Combined Experimental and Theoretical Study of the Influence of 3d Electrons in Redox Mediation.

Redox mediation is an innovative strategy for ensuring efficient energy harvesting from metal-oxygen systems. This work presents a systematic exploratory analysis of first-row transition-metal phthalocyanines as solution-state redox mediators for lithium-oxygen batteries. Our findings, based on experiment and theory, convincingly demonstrate that d5 (Mn), d7 (Co), and d8 (Ni) configurations function better compared to d6 (Fe) and d9 (Cu) in redox mediation of the discharge step. The d10 configuration (Zn) and non-d analogues (Mg) do not show any redox mediation because of the inability of binding with oxygen. The solution-state discharge product, transition-metal bound Li2O2, undergoes dissociation and oxidation in the charging step of the battery, thus confirming a bifunctional redox mediation. Apart from the reaction pathways predicted based on thermodynamic considerations, density functional theory calculations also reveal interesting effects of electrochemical perturbation on the redox mediation mechanisms and the role of the transition-metal center.

Interplay of hetero-MN4 catalytic sites on graphene for efficient oxygen reduction reaction

Noble-metal-free macrocycles dispersed on a carbonaceous support are a promising alternative to expensive Pt-based electrocatalysts to revolutionize the market outreach of low-cost clean energies technologies like fuel cells. Herein, a new composite material made of two transition metal phthalocyanines (MPc; M: Co, Fe) immobilized on a graphene support is presented as efficient and stable electrocatalyst for the oxygen reduction reaction (ORR). Electrochemical activation breaks the microparticles of MPcs into nanoclusters, facilitating their homogeneous dispersion on the support. The catalytic performance of the composite examined in oxygen-saturated KNO3 revealed tetra-electronic behavior and superior ORR activity compared to the similar loading of Pt/C catalyst. Moreover, high stability and negligible interference from methanol on the ORR response of the composite make it an ideal catalyst for direct methanol fuel cell. Density Functional Theory (DFT) calculations provide insights into the composite structure, revealing preferred arrangements in which two MPc sandwich graphene, and into the ORR mechanism in such configurations. The simulations revealed intricate interplay of interaction strengths between the composite's metal ions and ORR intermediates and O2, demonstrating that mixture of MPc facilitates higher ORR efficiency. Such enhancement is attributed to charge redistribution in sandwiched configurations, causing localization of dipoles on MPc.

Interaction Mechanism of Transition Metal Phthalocyanines on Transition Metal Nitride Supports

Interaction Mechanism of Transition Metal Phthalocyanines on Transition Metal Nitride Supports

Quasiparticle electronic structure of phthalocyanine:TMD interfaces from first-principles GW.

Interfaces formed between monolayer transition metal dichalcogenides and (metallo)phthalocyanine molecules are promising in energy applications and provide a platform for studying mixed-dimensional molecule-semiconductor heterostructures in general. An accurate characterization of the frontier energy level alignment at these interfaces is key in the fundamental understanding of the charge transfer dynamics between the two photon absorbers. Here, we employ the first-principles substrate screening GW approach to quantitatively characterize the quasiparticle electronic structure of a series of interfaces: metal-free phthalocyanine (H2Pc) adsorbed on monolayer MX2 (M = Mo, W; X = S, Se) and zinc phthalocyanine (ZnPc) adsorbed on MoX2 (X = S, Se). Furthermore, we reveal the dielectric screening effect of the commonly used α-quartz (SiO2) substrate on the H2Pc:MoS2 interface using the dielectric embedding GW approach. Our calculations furnish a systematic set of GW results for these interfaces, providing the structure-property relationship across a series of similar systems and benchmarks for future experimental and theoretical studies.

Range-separated hybrid functionals for mixed dimensional heterojunctions: Application to phthalocyanines/MoS2

We analyze the electronic structure and level alignment of transition-metal phthalocyanine (MPc) molecules adsorbed on two-dimensional MoS2 employing density functional theory (DFT) calculations. We develop a procedure for multi-objective optimal tuning of parameters of range-separated hybrid functionals in these mixed-dimensional systems. Using this procedure, which leads to the asymptotically correct exchange–correlation potential between molecules and two-dimensional materials, we obtain electronic structures consistent with experimental photoemission results for both energy level alignment and electronic bandgaps, representing a significant advance compared to standard DFT methods. We elucidate the MoS2 valence resonance with the transition-metal phthalocyanine non-frontier 3d orbitals and its dependence on the transition-metal atomic number. Based on our calculations, we derive parameter-free model self-energy corrections that quantitatively account for the effects of the heterogeneous dielectric environment on the electronic structure of these mixed-dimensional heterojunctions.

A density-functional-theory-based and machine-learning-accelerated hybrid method for intricate system catalysis

Being progressively applied in the design of highly active catalysts for energy devices, machine learning (ML) technology has shown attractive ability of dramatically reducing the computational cost of the traditional density functional theory (DFT) method, showing a particular advantage for the simulation of intricate system catalysis. Starting with a basic description of the whole workflow of the novel DFT-based and ML-accelerated (DFT-ML) scheme, and the common algorithms useable for machine learning, we presented in this paper our work on the development and performance test of a DFT-based ML method for catalysis program (DMCP) to implement the DFT-ML scheme. DMCP is an efficient and user-friendly program with the flexibility to accommodate the needs of performing ML calculations based on the data generated by DFT calculations or from materials database. We also employed an example of transition metal phthalocyanine double-atom catalysts as electrocatalysts for carbon reduction reaction to exhibit the general workflow of the DFT-ML hybrid scheme and our DMCP program.

Bimetal Phthalocyanine‐Modified Carbon Nanotube‐Based Bifunctional Catalysts for Zinc‐Air Batteries

AbstractA series of non‐precious bifunctional electrocatalysts composed of first‐row transition metal phthalocyanine (MPc, M=Mn, Ni, Co) modified multi‐walled carbon nanotubes (CNTs) was prepared and examined for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in alkaline media. The use of MPc in carbon matrix is attractive due to the formation of M‐Nx sites, which are responsible for ORR electrocatalysis and transition metal oxides that are OER‐active. Physical characterisation of the prepared catalysts was carried out by scanning electron microscopy/energy dispersive X‐ray spectroscopy, scanning transmission electron microscopy, N2 physisorption analysis, X‐ray diffraction and X‐ray photoelectron spectroscopy. The highest ORR activity among bimetallic catalysts was shown by a MnCoN‐CNT catalyst with half‐wave potential of 0.84 V. The electrochemical results of the prepared bimetallic catalysts revealed superior OER activity of NiCoN‐CNT with EOER of 1.61 V at 10 mA cm−2 and also good ORR activity (E1/2=0.83 V). Furthermore, NiCoN‐CNT exhibited excellent stability for both, ORR and OER, with only 5 mV change in half‐wave potential and only 14 mV loss in EOER, respectively. For checking bifunctionality, the NiCoN‐CNT catalyst was used as an air electrode and tested for zinc‐air battery (ZAB). Good ZAB performance was obtained, with open circuit voltage (OCV) of 1.338 V.