Advanced search
Start date
Betweenand
(Reference retrieved automatically from Web of Science through information on FAPESP grant and its corresponding number as mentioned in the publication by the authors.)

Aminoxyl Radicals of B/P Frustrated Lewis Pairs: Refinement of the Spin-Hamiltonian Parameters by Field- and Temperature-Dependent Pulsed EPR Spectroscopy

Full text
Author(s):
de Oliveira, Jr., Marcos [1] ; Knitsch, Robert [2] ; Sajid, Muhammad [3] ; Stute, Annika [3] ; Elmer, Lisa-Maria [3] ; Kehr, Gerald [3] ; Erker, Gerhard [3] ; Magon, Claudio J. [1] ; Jeschke, Gunnar [4] ; Eckert, Hellmut [1, 2]
Total Authors: 10
Affiliation:
[1] Univ Sao Paulo, Inst Fis Sao Carlos, POB 369, BR-13560970 Sao Carlos, SP - Brazil
[2] WWU Munster, Inst Phys Chem, Corrensstr 30, D-48149 Munster - Germany
[3] WWU Munster, Inst Organ Chem, Corrensstr 30, D-48149 Munster - Germany
[4] ETH, Phys Chem Lab, Vladimir Prelog Weg 2, CH-8049 Zurich - Switzerland
Total Affiliations: 4
Document type: Journal article
Source: PLoS One; v. 11, n. 6 JUN 23 2016.
Web of Science Citations: 4
Abstract

Q-band and X-band pulsed electron paramagnetic resonance spectroscopic methods (EPR) in the solid state were employed to refine the parameters characterizing the anisotropic interactions present in six nitroxide radicals prepared by N, N addition of NO to various borane-phosphane frustrated Lewis pairs (FLPs). The EPR spectra are characterized by the g-anisotropy as well as by nuclear hyperfine coupling between the unpaired electron and the B-11/B-10, N-14 and P-31 nuclear magnetic moments. It was previously shown that continuous-wave spectra measured at X-band frequency (9.5 GHz) are dominated by the magnetic hyperfine coupling to N-14 and P-31, whereas the g-tensor values and the B-11 hyperfine coupling parameters cannot be refined with high precision from lineshape fitting. On the other hand, the X-band electron spin echo envelope modulation (ESEEM) and hyperfine sublevel correlation (HYSCORE) spectra are completely dominated by the nuclear hyperfine coupling to the B-11 nuclei, allowing a selective determination of their interaction parameters. In the present work this analysis has been further validated by temperature dependent ESEEM measurements. In addition, pulsed EPR data measured in the Q-band (34 GHz) are reported, which present an entirely different situation: the g-tensor components can be measured with much higher precision, and the ESEEM and HYSCORE spectra contain information about all of the B-10, B-11, N-14 and P-31 hyperfine interaction parameters. Based on these new results, we report here high-accuracy and precision data of the EPR spin Hamiltonian parameters measured on six FLP-NO radical species embedded in their corresponding hydroxylamine host structures. While the ESEEM spectra at Q-band frequency turn out to be very complex (due to the multinuclear contribution to the overall signal) in the HYSCORE experiment the extension over two dimensions renders a better discrimination between the different nuclear species, and the signals arising from hyperfine coupling to B-10, B-11, N-14 and P-31 nuclei can be individually analyzed. (AU)

FAPESP's process: 13/23490-3 - Magnetic resonance techniques for the study of Structure/Property correlations in photonic glassy and glass ceramic materials
Grantee:Marcos de Oliveira Junior
Support type: Scholarships in Brazil - Post-Doctorate
FAPESP's process: 13/07793-6 - CEPIV - Center for Teaching, Research and Innovation in Glass
Grantee:Edgar Dutra Zanotto
Support type: Research Grants - Research, Innovation and Dissemination Centers - RIDC
FAPESP's process: 15/04063-2 - Coordination environments of rare-earth ions in photonic glasses analyzed by pulsed electron paramagnetic resonance techniques
Grantee:Marcos de Oliveira Junior
Support type: Scholarships abroad - Research Internship - Post-doctor