Magnetic-field-tuned phase transition of a molecular material from the isolated-spin to the coupled-spin regime.
SANTANA, Vinicius T.; CUNHA, Beatriz N.; PLUTÍN, Ana M.; SILVEIRA, Rafael G.; CASTELLANO, Eduardo Ernesto; BATISTA, Alzir A.; CALVO, Rafael; NASCIMENTO, Otaciro Rangel.
SANTANA, Vinicius T.; CUNHA, Beatriz N.; PLUTÍN, Ana M.; SILVEIRA, Rafael G.; CASTELLANO, Eduardo Ernesto; BATISTA, Alzir A.; CALVO, Rafael; NASCIMENTO, Otaciro Rangel.
 Abstract: We report the preparation, X-ray structure, chemical properties, and electron paramagnetic resonance (EPR) studies at Q and X-bands and temperature (mainly) T = 293 K of powder and oriented single crystal samples of the new compound [Cu(N0,N0-dimethyl-N0-benzoylthiourea)(2,20-bipyridine)Cl], called CuBMB. The EPR spectra of single crystal samples at the Q-band display abrupt merging and narrowing of the peaks corresponding to two rotated copper sites as a function of magnetic field (B0) orientation. This behaviour indicates a quantum transition from an array of quasi-isolated spins to a quantumentangled spin array associated with exchange narrowing processes and produced by weak intermolecular exchange interactions Ji between neighbour copper spins. This transition occurs when the magnitudes of the anisotropic contributions to the Zeeman couplings, tuned with the direction of B0, approach these The spectrum of polycrystalline (powder) samples at the Q-band is a sum of contributions of microcrystals in each phase, and the fraction F of the entangled phase depends on the microwave frequency. The X-band spectrum is compatible with the Q-band results, but does not display a transition, and the spin system is in the quantum-entangled phase for all field orientations. This behaviour is further studied with a simple geometric model giving basic predictions. The crystal structure of CuBMB is monoclinic, space group P21/n, with a = 11.9790(3) Å, b = 14.0236(5) Å, c = 12.1193(3) Å, b = 104.952(2)1 and Z = 4, and the copper ions are equatorially bonded to the benzoylthiourea and bipyridine ligands in a heavily distorted square pyramidal structure. | |
| Physical Chemistry Chemical Physics |
| v. 21, n. 8, p. 4394-4407 - Ano: 2019 |
| Fator de Impacto: 3,906 |
| http://dx.doi.org/10.1039/c8cp06719h |  @article={002929500,author = {SANTANA, Vinicius T.; CUNHA, Beatriz N.; PLUTÍN, Ana M.; SILVEIRA, Rafael G.; CASTELLANO, Eduardo Ernesto; BATISTA, Alzir A.; CALVO, Rafael; NASCIMENTO, Otaciro Rangel.},title={Magnetic-field-tuned phase transition of a molecular material from the isolated-spin to the coupled-spin regime},journal={Physical Chemistry Chemical Physics},note={v. 21, n. 8, p. 4394-4407},year={2019}} |