scholarly journals Shifted loops and coercivity from field-imprinted high-energy barriers in ferritin and ferrihydrite nanoparticles

2011 ◽  
Vol 84 (10) ◽  
Author(s):  
N. J. O. Silva ◽  
V. S. Amaral ◽  
A. Urtizberea ◽  
R. Bustamante ◽  
A. Millán ◽  
...  
Keyword(s):  
High Energy ◽  
Energy Barriers

Planar Dy3 + Dy3 clusters: design, structure and axial ligand perturbed magnetic dynamics

2015 ◽  
Vol 44 (47) ◽  
pp. 20316-20320 ◽  
Author(s):  
Xiao-Lei Li ◽  
Han Li ◽  
Di-Ming Chen ◽  
Chao Wang ◽  
Jianfeng Wu ◽  
...  
Keyword(s):  
Single Molecule ◽  
High Energy ◽  
Axial Ligand ◽  
Magnetic Behaviour ◽  
Energy Barriers ◽  
Magnetic Dynamics ◽  
Design Structure

Coupling Dy3 triangles results in two unique Dy6 complexes showing single-molecule magnetic behaviour with high energy barriers of 116 and 181 K for Dy6–NO3 and Dy6–SCN, respectively.

N.M.R. studies of some chromium(III) dithiocarbamate complexes

1974 ◽  
Vol 27 (10) ◽  
pp. 2089 ◽  
Author(s):  
RM Golding ◽  
PC Healy ◽  
P Colombera ◽  
AH White
Keyword(s):  
Temperature Dependence ◽  
Hyperfine Coupling ◽  
Relaxation Mechanism ◽  
High Energy ◽  
Coupling Constants ◽  
Energy Barriers ◽  
Double Peak ◽  
Hyperfine Coupling Constants

The temperature dependence of the proton N.M.R. spectra of some simple tris(N,N-disubstituted dithiocarbamato)chromium(111) derivatives, [Cr(S2CNR2)3], has been studied in deuterochloroform solution over the range ? 60� to + 60�C. In these spectra, which are very broad, the N-CHn protons in certain cases exhibit a double peak unlike the iron(111) or manganese(111) complexes-probably a consequence of high energy barriers between the Δ and Δ enantiomers, the broadness of the spectra being ascribed to the lack of an appropriate relaxation mechanism. The spectra of a number of further iron(111) and manganese(111) derivatives are reported and the hyperfine coupling constants in the three series of complexes compared.

scholarly journals A REP-FAMSEC Method as a Tool in Explaining Reaction Mechanisms: A Nucleophilic Substitution of 2-Phenylquinoxaline as a DFT Case Study

Molecules ◽  
2021 ◽  
Vol 26 (6) ◽  
pp. 1570
Author(s):  
Brian Kamogelo Mdhluli ◽  
Winston Nxumalo ◽  
Ignacy Cukrowski
Keyword(s):  
Nucleophilic Substitution ◽  
Intramolecular Interaction ◽  
Molecular System ◽  
High Energy ◽  
Energy Barriers ◽  
Subsequent Formation ◽  
Irreversible Reaction ◽  
Very High Energy ◽  
Very High

In search for the cause leading to low reaction yields, each step along the reaction energy profile computed for the assumed oxidative nucleophilic substitution of hydrogen (ONSH) reaction between 2-phenylquinoxaline and lithium phenylacetylide was modelled computationally. Intermolecular and intramolecular interaction energies and their changes between consecutive steps of ONSH were quantified for molecular fragments playing leading roles in driving the reaction to completion. This revealed that the two reactants have a strong affinity for each other, driven by the strong attractive interactions between Li and two N-atoms, leading to four possible reaction pathways (RP-C2, RP-C3, RP-C5, and RP-C10). Four comparable in energy and stabilizing molecular system adducts were formed, each well prepared for the subsequent formation of a C–C bond at either one of the four identified sites. However, as the reaction proceeded through the TS to form the intermediates (5a–d), very high energy barriers were observed for RP-C5 and RP-C10. The data obtained at the nucleophilic addition stage indicated that RP-C3 was both kinetically and thermodynamically favored over RP-C2. However, the energy barriers observed at this stage were very comparable for both RPs, indicating that they both can progress to form intermediates 5a and 5b. Interestingly, the phenyl substituent (Ph1) on the quinoxaline guided the nucleophile towards both RP-C2 and RP-C3, indicating that the preferred RP cannot be attributed to the steric hindrance caused by Ph1. Upon the introduction of H2O to the system, both RPs were nearly spontaneous towards their respective hydrolysis products (8a and 8b), although only 8b can proceed to the final oxidation stage of the ONSH reaction mechanism. The results suggest that RP-C2 competes with RP-C3, which may lead to a possible mixture of their respective products. Furthermore, an alternative, viable, and irreversible reaction path was discovered for the RP-C2 that might lead to substantial waste. Finally, the modified experimental protocol is suggested to increase the yield of the desired product.

scholarly journals Correlating blocking temperatures with relaxation mechanisms in monometallic single-molecule magnets with high energy barriers (Ueff > 600 K)

2019 ◽  
Vol 55 (49) ◽  
pp. 7025-7028 ◽  
Author(s):  
Marcus J. Giansiracusa ◽  
Andreas K. Kostopoulos ◽  
David Collison ◽  
Richard E. P. Winpenny ◽  
Nicholas F. Chilton
Keyword(s):  
Single Molecule ◽  
High Energy ◽  
Energy Barriers ◽  
Single Molecule Magnets

Correlating blocking temperatures with relaxation mechanisms in single-molecule magnets.

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