Spin Modulation in Highly Distorted FeIIIPorphyrinates by Using Axial Coordination and Their π-Cation Radicals

2016 ◽  
Vol 2016 (21) ◽  
pp. 3441-3453 ◽  
Author(s):  
Dipankar Sahoo ◽  
Tapas Guchhait ◽  
Sankar Prasad Rath
Keyword(s):  
Axial Coordination ◽  
Cation Radicals ◽  
Spin Modulation

Seeking Magneto-Structural Correlations in Easily Tailored Pentagonal Bipyramid Dy(III) Single-Ion Magnets

2019 ◽  
Author(s):  
Guo-Zhang Huang ◽  
Ze-Yu Ruan ◽  
Jie-Yu Zheng ◽  
Yan-Cong Chen ◽  
Si-Guo Wu ◽  
...  
Keyword(s):  
Single Molecule ◽  
Structural Engineering ◽  
Magnetic Hysteresis ◽  
Sweep Rate ◽  
Coordination Bond ◽  
Pentagonal Bipyramid ◽  
Single Molecule Magnets ◽  
Crystal Field Theory ◽  
Bond Angles ◽  
Axial Coordination

<p><a></a>Controlling molecular magnetic anisotropy via structural engineering is delicate and fascinating, especially for single-molecule magnets (SMMs). Herein a family of dysprosium single-ion magnets (SIMs) sitting in pentagonal bipyramid geometry have been synthesized with the variable-size terminal ligands and counter anions, through which the subtle coordination geometry of Dy(III) can be finely tuned based on the size effect. The effective energy barrier (Ueff) successfully increases from 439 K to 632 K and the magnetic hysteresis temperature (under a 200 Oe/s sweep rate) raises from 11 K to 24 K. Based on the crystal-field theory, a semi-quantitative magneto-structural correlation deducing experimentally for the first time is revealed that the Ueff is linearly proportional to the structural-related value S2<sup>0</sup> corresponding to the axial coordination bond lengths and the bond angles. Through the evaluation of the remanent magnetization from hysteresis, quantum tunneling of magnetization (QTM) is found to exhibit negative correlation with the structural-related value S<sub>tun</sub> corresponding to the axial coordination bond angles.<br></p>

scholarly journals The Long-Lasting Story of One Sensor Development: From Novel Ionophore Design toward the Sensor Selectivity Modeling and Lifetime Improvement

Sensors ◽  
2021 ◽  
Vol 21 (4) ◽  
pp. 1401
Author(s):  
Larisa Lvova ◽  
Donato Monti ◽  
Corrado Di Natale ◽  
Roberto Paolesse
Keyword(s):  
Anion Exchanger ◽  
Specific Interaction ◽  
Spectroscopic Studies ◽  
Polymeric Membranes ◽  
Polymeric Membrane ◽  
Active Components ◽  
Nitrite Ion ◽  
Working Mechanism ◽  
Axial Coordination ◽  
Porphyrin Aggregation

The metalloporphyrin ligand bearing incorporated anion-exchanger fragment, 5-[4-(3-trimethylammonium)propyloxyphenyl]-10,15,20-triphenylporphyrinate of Co(II) chloride, CoTPP-N, has been tested as anion-selective ionophore in PVC-based solvent polymeric membrane sensors. A plausible sensor working mechanism includes the axial coordination of the target anion on ionophore metal center followed by the formed complex aggregation with the second ionophore molecule through positively charged anion-exchanger fragment. The UV-visible spectroscopic studies in solution have revealed that the analyte concentration increase induces the J-type porphyrin aggregation. Polymeric membranes doped with CoTPP-N showed close to the theoretical Nernstian response toward nitrite ion, preferably coordinated by the ionophore, and were dependent on the presence of additional membrane-active components (lipophilic ionic sites and ionophore) in the membrane phase. The resulting selectivity was a subject of specific interaction and/or steric factors. Moreover, it was demonstrated theoretically and confirmed experimentally that the selection of a proper ratio of ionophore and anionic additive can optimize the sensor selectivity and lifetime.

scholarly journals Resonance Raman studies of iron spin and axial coordination in distal pocket mutants of ferric myoglobin.

1990 ◽  
Vol 265 (21) ◽  
pp. 12143-12145 ◽  
Author(s):  
D Morikis ◽  
P M Champion ◽  
B A Springer ◽  
K D Egebey ◽  
S G Sligar
Keyword(s):  
Resonance Raman ◽  
Axial Coordination

Azacalix[4]arene cation radicals: spin-delocalised doublet- and triplet-ground states observed in the macrocyclic m-phenylene system connected with nitrogen atoms

2008 ◽  
pp. 2812 ◽  
Author(s):  
Koichi Ishibashi ◽  
Hirohito Tsue ◽  
Naoko Sakai ◽  
Satoshi Tokita ◽  
Kazuhiro Matsui ◽  
...  
Keyword(s):  
Ground States ◽  
Cation Radicals

Density functional theory investigation of the effect of axial coordination and annelation on the absorption spectroscopy of nickel(II) and vanadyl porphyrins relevant to bitumen and crude oils

2013 ◽  
Vol 91 (9) ◽  
pp. 872-878 ◽  
Author(s):  
Stanislav R. Stoyanov ◽  
Cindy-Xing Yin ◽  
Murray R. Gray ◽  
Jeffrey M. Stryker ◽  
Sergey Gusarov ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Polyaromatic Hydrocarbons ◽  
Geometry Optimization ◽  
Soret Band ◽  
Heavy Oils ◽  
Visible Absorption ◽  
Functional Theory ◽  
Axial Coordination ◽  
Td Dft

The vanadium and nickel components in heavy oils and bitumen are important impurities in catalytic processing and form aggregates with other asphaltene components. Metalloporphyrins are commonly analyzed using the characteristic Soret band in the UV–vis absorption spectrum. However, the Soret band of metalloporphyrins in petroleum is broadened and weaker than expected based on the concentration of Ni and V in heavy oils and the extinction coefficients of isolated porphyrins. We hypothesize that the low intensity and broadening of the Soret band could be due to axial coordination of the metal center or fusion (annelation) of aromatic rings on the porphyrin π-system. This hypothesis is examined using the density functional theory for geometry optimization and time-dependent density functional theory (TD-DFT) for calculation of excited states of nickel(II) and vanadyl porphyrins with axially coordinated ligands and annelated polyaromatic hydrocarbons. Predictions of the excited electronic states performed using the tandem of TD-DFT and conductor-like polarizable continuum model of solvation support this hypothesis and provide insight into the extent of Soret band broadening and intensity decrease due to coordination and annelation. These computational results, validated with respect to visible absorption spectra, are important for understanding asphaltene aggregation and spectroscopic characterization and suggest methods for removal of transition metals from heavy oil.

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