scholarly journals Ammonia adsorption on iron phthalocyanine on Au(111): Influence on adsorbate–substrate coupling and molecular spin

2011 ◽  
Vol 134 (11) ◽  
pp. 114710 ◽  
Author(s):  
Cristina Isvoranu ◽  
Bin Wang ◽  
Evren Ataman ◽  
Karina Schulte ◽  
Jan Knudsen ◽  
...  
Keyword(s):  
Iron Phthalocyanine ◽  
Ammonia Adsorption ◽  
Substrate Coupling ◽  
Molecular Spin

A Pyridinic Fe-N4 Macrocycle Effectively Models the Active Sites in Fe/N-Doped Carbon Electrocatalysts

2020 ◽  
Author(s):  
Travis Marshall-Roth ◽  
Nicole J. Libretto ◽  
Alexandra T. Wrobel ◽  
Kevin Anderton ◽  
Nathan D. Ricke ◽  
...  
Keyword(s):  
Oxygen Reduction ◽  
Active Sites ◽  
Catalytic Properties ◽  
Reduction Reaction ◽  
Iron Phthalocyanine ◽  
Electrochemical Studies ◽  
Onset Potential ◽  
Nitrogen Doped Carbon ◽  
Iron Active Sites

Iron- and nitrogen-doped carbon (Fe-N-C) materials are leading candidates to replace platinum in fuel cells, but their active site structures are poorly understood. A leading postulate is that iron active sites in this class of materials exist in an Fe-N<sub>4</sub> pyridinic ligation environment. Yet, molecular Fe-based catalysts for the oxygen reduction reaction (ORR) generally feature pyrrolic coordination and pyridinic Fe-N<sub>4</sub> catalysts are, to the best of our knowledge, non-existent. We report the synthesis and characterization of a molecular pyridinic hexaazacyclophane macrocycle, (phen<sub>2</sub>N<sub>2</sub>)Fe, and compare its spectroscopic, electrochemical, and catalytic properties for oxygen reduction to a prototypical Fe-N-C material, as well as iron phthalocyanine, (Pc)Fe, and iron octaethylporphyrin, (OEP)Fe, prototypical pyrrolic iron macrocycles. N 1s XPS signatures for coordinated N atoms in (phen<sub>2</sub>N<sub>2</sub>)Fe are positively shifted relative to (Pc)Fe and (OEP)Fe, and overlay with those of Fe-N-C. Likewise, spectroscopic XAS signatures of (phen<sub>2</sub>N<sub>2</sub>)Fe are distinct from those of both (Pc)Fe and (OEP)Fe, and are remarkably similar to those of Fe-N-C with compressed Fe–N bond lengths of 1.97 Å in (phen<sub>2</sub>N<sub>2</sub>)Fe that are close to the average 1.94 Å length in Fe-N-C. Electrochemical studies establish that both (Pc)Fe and (phen<sub>2</sub>N<sub>2</sub>)Fe have relatively high Fe(III/II) potentials at ~0.6 V, ~300 mV positive of (OEP)Fe. The ORR onset potential is found to directly correlate with the Fe(III/II) potential leading to a ~300 mV positive shift in the onset of ORR for (Pc)Fe and (phen<sub>2</sub>N<sub>2</sub>)Fe relative to (OEP)Fe. Consequently, the ORR onset for (phen<sub>2</sub>N<sub>2</sub>)Fe and (Pc)Fe is within 150 mV of Fe-N-C. Unlike (OEP)Fe and (Pc)Fe, (phen<sub>2</sub>N<sub>2</sub>)Fe displays excellent selectivity for 4-electron ORR with <4% maximum H<sub>2</sub>O<sub>2</sub> production, comparable to Fe-N-C materials. The aggregate spectroscopic and electrochemical data establish (phen<sub>2</sub>N<sub>2</sub>)Fe as a pyridinic iron macrocycle that effectively models Fe-N-C active sites, thereby providing a rich molecular platform for understanding this important class of catalytic materials.<p><b></b></p>

Engineering Electronic Structure to Protect Phase Memory in Molecular Qubits by Minimising Orbital Angular Momentum

2018 ◽  
Author(s):  
Ana Maria Ariciu ◽  
David H. Woen ◽  
Daniel N. Huh ◽  
Lydia Nodaraki ◽  
Andreas Kostopoulos ◽  
...  
Keyword(s):  
Electron Spin ◽  
Quantum Coherence ◽  
Quantum Information Processing ◽  
Pulse Sequences ◽  
Grover Algorithm ◽  
Ligand Shell ◽  
Information Strategies ◽  
Spin Qubit ◽  
Molecular Spin ◽  
The Impact

Using electron spins within molecules for quantum information processing (QIP) was first proposed by Leuenberger and Loss (1), who showed how the Grover algorithm could be mapped onto a Mn12 cage (2). Since then several groups have examined two-level (S = ½) molecular spin systems as possible qubits (3-12). There has also been a report of the implementation of the Grover algorithm in a four-level molecular qudit (13). A major challenge is to protect the spin qubit from noise that causes loss of phase information; strategies to minimize the impact of noise on qubits can be categorized as corrective, reductive, or protective. Corrective approaches allow noise and correct for its impact on the qubit using advanced microwave pulse sequences (3). Reductive approaches reduce the noise by minimising the number of nearby nuclear spins (7-11), and increasing the rigidity of molecules to minimise the effect of vibrations (which can cause a fluctuating magnetic field via spin-orbit coupling) (9,11); this is essentially engineering the ligand shell surrounding the electron spin. A protective approach would seek to make the qubit less sensitive to noise: an example of the protective approach is the use of clock transitions to render spin states immune to magnetic fields at first order (12). Here we present a further protective method that would complement reductive and corrective approaches to enhancing quantum coherence in molecular qubits. The target is a molecular spin qubit with an effective 2S ground state: we achieve this with a family of divalent rare-earth molecules that have negligible magnetic anisotropy such that the isotropic nature of the electron spin renders the qubit markedly less sensitive to magnetic noise, allowing coherent spin manipulations even at room temperature. If combined with the other strategies, we believe this could lead to molecular qubits with substantial advantages over competing qubit proposals.<br>

Topochemical pyrolytic synthesis of quasi-Mxene hybrids via ionic liquid-iron phthalocyanine as a self-template

2019 ◽  
Vol 55 (6) ◽  
pp. 771-774
Author(s):  
Ruixuan Chen ◽  
Kun Rui ◽  
Xiaofei Yang ◽  
Aoming Huang ◽  
Yao Zhang ◽  
...  
Keyword(s):  
Ionic Liquid ◽  
Liquid Iron ◽  
Iron Phthalocyanine

A novel quasi-Mxene structure hybrid is first realized through topochemical pyrolysis with the assistance of an ionic liquid.

scholarly journals Encoding Information on the Excited State of a Molecular Spin Chain

2021 ◽  
pp. 2009467
Author(s):  
Kostantine Katcko ◽  
Etienne Urbain ◽  
Franck Ngassam ◽  
Lalit Kandpal ◽  
Bhavishya Chowrira ◽  
...  
Keyword(s):  
Excited State ◽  
Spin Chain ◽  
Molecular Spin

AFM Imaging of Molecular Spin-State Changes through Quantitative Thermomechanical Measurements

2014 ◽  
Vol 26 (18) ◽  
pp. 2889-2893 ◽  
Author(s):  
Edna M. Hernández ◽  
Carlos M. Quintero ◽  
Olena Kraieva ◽  
Christophe Thibault ◽  
Christian Bergaud ◽  
...  
Keyword(s):  
Spin State ◽  
Afm Imaging ◽  
Molecular Spin ◽  
State Changes
Sign in / Sign up

Export Citation Format

Share Document