Comparison of ensemble and single molecule approaches to probing polymer relaxation dynamics near Tg

2002 ◽  
Vol 116 (13) ◽  
pp. 5850-5856 ◽  
Author(s):  
Laura A. Deschenes ◽  
David A. Vanden Bout
Keyword(s):  
Single Molecule ◽  
Relaxation Dynamics ◽  
Polymer Relaxation

An air stable radical-bridged dysprosium single molecule magnet and its neutral counterpart: redox switching of magnetic relaxation dynamics

2017 ◽  
Vol 53 (14) ◽  
pp. 2283-2286 ◽  
Author(s):  
Brian S. Dolinar ◽  
Silvia Gómez-Coca ◽  
Dimitris I. Alexandropoulos ◽  
Kim R. Dunbar
Keyword(s):  
Magnetic Properties ◽  
Single Molecule ◽  
Quantum Tunneling ◽  
Magnetic Relaxation ◽  
Thermal Relaxation ◽  
Relaxation Dynamics ◽  
Single Molecule Magnet ◽  
Neutral Compound ◽  
Redox Switching ◽  
P Addition

Addition of a radical to the bridging tetrazine ligand of a Dy2 complex dramatically alters the magnetic properties. The radical complex undergoes magnetic relaxation via a thermal relaxation pathway, whereas the neutral compound relaxes via quantum tunneling of the magnetization.

scholarly journals Ab Initio Prediction of High-Temperature Magnetic Relaxation Rates in Single-Molecule Magnets

2021 ◽  
Author(s):  
Daniel Reta ◽  
Jon G. C. Kragskow ◽  
Nicholas Chilton
Keyword(s):  
High Temperature ◽  
Ab Initio ◽  
Single Molecule ◽  
Magnetic Relaxation ◽  
Quantitative Prediction ◽  
Relaxation Dynamics ◽  
Efficient Design ◽  
Relaxation Rates ◽  
Design Strategies ◽  
Single Molecule Magnets

<p>Organometallic molecules based on [Dy(Cp<sup>R</sup>)<sub>2</sub>]<sup>+</sup> cations have emerged as clear front-runners in the search for high-temperature single-molecule magnets. However, despite a growing family of structurally-similar molecules, these molecules show significant variations in their magnetic properties, demonstrating the importance of understanding magneto-structural relationships towards developing more efficient design strategies. Here we refine our <i>ab initio</i> spin dynamics methodology and show that it is capable of quantitative prediction of relative relaxation rates in the Orbach region. Applying it to all reported [Dy(Cp<sup>R</sup>)<sub>2</sub>]<sup>+</sup> cations allows us to tease out differences in their relaxation dynamics, highlighting that the main discriminant is the magnitude of the crystal field splitting. We subsequently employ the method to predict relaxation rates for a series of hypothetical organometallic sandwich compounds, revealing an upper limit to the effective barrier to magnetic relaxation of around 2200 K, which has been reached. However, we show that further improvements to single-molecule magnets can be made by moving vibrational modes off-resonance with electronic excitations.</p>

scholarly journals Probing Relaxation Dynamics in Five‐Coordinate Dysprosium Single‐Molecule Magnets

2020 ◽  
Vol 26 (35) ◽  
pp. 7774-7778 ◽  
Author(s):  
Vijay S. Parmar ◽  
Fabrizio Ortu ◽  
Xiaozhou Ma ◽  
Nicholas F. Chilton ◽  
Rodolphe Clérac ◽  
...  
Keyword(s):  
Single Molecule ◽  
Relaxation Dynamics ◽  
Single Molecule Magnets

See-Saw Shaped Dy(III) Single-Molecule Magnets with High Anisotropy Barriers

2020 ◽  
Author(s):  
Katie L. M. Harriman ◽  
Jesse Murillo ◽  
Elizaveta A. Suturina ◽  
Skye Fortier ◽  
Muralee Murugesu
Keyword(s):  
Magnetic Susceptibility ◽  
Single Molecule ◽  
Molecular Geometry ◽  
High Energy ◽  
Zero Field ◽  
Relaxation Dynamics ◽  
Single Molecule Magnets ◽  
Ancillary Ligands ◽  
Spin Reversal ◽  
Magnetic Spin

<p>Utilizing a terphenyl bisanilide ligand, two Dy(III) complexes [K(DME)<sub>x</sub>][L<sup>Ar</sup>Dy(X)<sub>2</sub>] (L<sup>Ar</sup> = {C<sub>6</sub>H<sub>4</sub>[(2,6-<i><sup>i</sup></i>PrC<sub>6</sub>H<sub>3</sub>)NC<sub>6</sub>H<sub>4</sub>]<sub>2</sub>}<sup>2-</sup>), X = Cl (<b>1</b>) and X = I (<b>2</b>) were synthesized. The ligand imposes an unusual see-saw shaped molecular geometry leading to a coordinatively unsaturated complex with near-linear N-Dy-N (avg. 159.9° for<b>1</b> and avg. 160.3<sup>o</sup> for <b>2</b>) bond angles. These complexes exhibit Single-Molecule Magnet (SMM) behavior with significant uniaxial magnetic anisotropy as a result of the transverse coordination of the bisanlide ligand which yields high energy barriers to magnetic spin reversal of <i>U</i><sub>eff</sub> = 1334 K/ 927cm<sup>-1</sup> (<b>1</b>) and 1299 K/ 903 cm<sup>-1</sup> (<b>2</b>) in zero field. Magneto-structural correlations are discussed with the goal of finding a link between halide ancillary ligands in the structurally analogous complexes and the through barrier relaxation dynamics observed in the ac magnetic susceptibility, despite the similar dc magnetic susceptibility for compounds <b>1</b> and <b>2</b>. <i>Ab initio</i> calculations reveal that the dominant crystal field of the bisanilide ligand controls the orientation of the main magnetic axis which runs nearly parallel to the N-Dy-N bonds, and defines the height of the energy barrier. Thus, further validating the use of transverse ligands to enhance the SMM properties of Dy(III) ions.</p>

Single Molecule Probing of the Local Segmental Relaxation Dynamics in Polymer above the Glass Transition Temperature

2009 ◽  
Vol 131 (34) ◽  
pp. 12201-12210 ◽  
Author(s):  
Els Braeken ◽  
Gert De Cremer ◽  
Philippe Marsal ◽  
Gérard Pèpe ◽  
Klaus Müllen ◽  
...  
Keyword(s):  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Single Molecule ◽  
Relaxation Dynamics ◽  
Segmental Relaxation

Dynamic Mechanical Analysis and Dielectric Relaxation for Second Order Nonlinear Optical Applications

1995 ◽  
Vol 392 ◽  
Author(s):  
Leah A. Sullivan ◽  
Hilary S. Lackritz
Keyword(s):  
Nonlinear Optical ◽  
Second Harmonic ◽  
Mechanical Analysis ◽  
Second Order ◽  
Mechanical Relaxation ◽  
Processing Temperature ◽  
Relaxation Techniques ◽  
Relaxation Dynamics ◽  
Dielectric Relaxations ◽  
Polymer Relaxation

AbstractRelaxation dynamics of poly(methyl methacrylate) (PMMA) and doped PMMA systems are investigated as a function of processing temperature and frequency. Polymer relaxations and changes in local mobility are responsible for chromophore reorientation and lead to a loss in second-order nonlinear optical (NLO) properties. Studying polymer relaxations enables the temporal and thermal stability of the NLO polymer systems to be more accurately and readily predicted. The polymer dynamics are studied by correlating mechanical and dielectric relaxations to polymer and chromophore relaxations that occur during chromophore reorientation in second harmonic generation experiments. Dielectric and mechanical relaxation techniques enable polymer relaxation dynamics to be observed over a broad frequency range. The plasticization effect of the NLO chromophores on the polymer relaxation dynamics is also investigated.

scholarly journals Tetranuclear dysprosium single-molecule magnets: tunable magnetic interactions and magnetization dynamics through modifying coordination number

2019 ◽  
Vol 48 (6) ◽  
pp. 2135-2141 ◽  
Author(s):  
Kun Zhang ◽  
Gao-Peng Li ◽  
Vincent Montigaud ◽  
Olivier Cador ◽  
Boris Le Guennic ◽  
...  
Keyword(s):  
Coordination Number ◽  
Single Molecule ◽  
Magnetic Interactions ◽  
Relaxation Dynamics ◽  
Magnetization Dynamics ◽  
Single Molecule Magnets ◽  
Coordination Environment ◽  
Coordination Sites ◽  
Fine Control

The magnetic interactions and relaxation dynamics are modulated in two polynuclear dysprosium(iii) SMMs through a fine control of the coordination environment on the changeable coordination sites.

scholarly journals Ab Initio Prediction of High-Temperature Magnetic Relaxation Rates in Single-Molecule Magnets

2021 ◽  
Author(s):  
Daniel Reta ◽  
Jon G. C. Kragskow ◽  
Nicholas Chilton
Keyword(s):  
High Temperature ◽  
Ab Initio ◽  
Single Molecule ◽  
Magnetic Relaxation ◽  
Quantitative Prediction ◽  
Relaxation Dynamics ◽  
Efficient Design ◽  
Relaxation Rates ◽  
Design Strategies ◽  
Single Molecule Magnets

<p>Organometallic molecules based on [Dy(Cp<sup>R</sup>)<sub>2</sub>]<sup>+</sup> cations have emerged as clear front-runners in the search for high-temperature single-molecule magnets. However, despite a growing family of structurally-similar molecules, these molecules show significant variations in their magnetic properties, demonstrating the importance of understanding magneto-structural relationships towards developing more efficient design strategies. Here we refine our <i>ab initio</i> spin dynamics methodology and show that it is capable of quantitative prediction of relative relaxation rates in the Orbach region. Applying it to all reported [Dy(Cp<sup>R</sup>)<sub>2</sub>]<sup>+</sup> cations allows us to tease out differences in their relaxation dynamics, highlighting that the main discriminant is the magnitude of the crystal field splitting. We subsequently employ the method to predict relaxation rates for a series of hypothetical organometallic sandwich compounds, revealing an upper limit to the effective barrier to magnetic relaxation of around 2200 K, which has been reached. However, we show that further improvements to single-molecule magnets can be made by moving vibrational modes off-resonance with electronic excitations.</p>

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