Publication detail

Exchange couplings and quantum phases in two dissimilar arrays of similar copper dinuclear units

Sartoris, RP. Santana, VT. Freire, E. Baggio, RF. Nascimento, OR. Calvo, R.

Original Title

Exchange couplings and quantum phases in two dissimilar arrays of similar copper dinuclear units

Type

journal article in Web of Science

Language

English

Original Abstract

To investigate the magnetic properties and the spin entanglement of dinuclear arrays, we prepared compounds [{Cu(pAB)(phen)H2O}(2)NO3pABH2H(2)O], 1, and [Cu-2(pAB)(2)(phen)(2)pz](n), 2 (pABH = p-aminobenzoic acid, phen = 1,10-phenanthroline and pz = pyrazine). The structure of 1 is known and we report here that of 2. They contain similar dinuclear units of Cu-II ions with 1/2-spins S-1 and S-2 bridged by pairs of pAB molecules, with similar intradinuclear exchange and fine interactions , but different 3D crystal arrays with weak interdinuclear exchange J ', stronger in 2 than in 1. To investigate the magnetic properties and the spin entanglement produced by J ', we collected the powder spectra of 1 and 2 at 9.4 GHz and T between 5 and 298 K, and at 34.4 GHz and T = 298 K and single-crystal spectra at room T and 34.4 GHz as a function of magnetic field (B-0) orientation in three crystal planes, calculating intradinuclear magnetic parameters J(1)0 = (-75 +/- 1) cm(-1), J(2)0 = (-78 +/- 2) cm(-1), |D-(1)| = (0.142 +/- 0.006) cm(-1), |D-(2)| = (0.141 +/- 0.006) cm(-1) and E-(1) similar to E-(2) similar to 0. Single crystal data indicate a quantum entangled phase in 2 around the crossing between two fine structure EPR absorption peaks within the spin triplet. This phase also shows up in powder samples of 2 as a U-peak collecting the signals of the entangled microcrystals, a feature that allows estimating |J '|. Transitions between the two quantum phases are observed in single crystals of 2 changing the orientation of B-0. We estimate interdinuclear exchange couplings |J '((1))| < 0.003 cm(-1) and |J '((2))| = (0.013 +/- 0.005) cm(-1), in 1 and 2, respectively. Our analysis indicates that the standard approximation of a spin Hamiltonian with S = 1 for the dinuclear spectra is valid only when the interdinuclear coupling is large enough, as for compound 2 (|J '((2))/J(2)0| similar to 1.7 x 10(-4)). When J ' is negligible as in 1, the real spin Hamiltonian with two spins 1/2 has to be used. Broken-symmetry DFT predicts correctly the nature and magnitude of the antiferromagnetic exchange coupling in 1 and 2 and ferromagnetic interdinuclear coupling for compound 2.

Keywords

ELECTRON-PARAMAGNETIC-RESONANCE; PHOTOSYNTHETIC REACTION CENTERS; BOSE-EINSTEIN CONDENSATION; MAGNETIC-PROPERTIES; GENERAL-THEORY; COMPLEXES; EPR; TRANSITION; PARAMETERS; ANISOTROPY

Authors

Sartoris, RP.; Santana, VT.; Freire, E.; Baggio, RF.; Nascimento, OR.; Calvo, R.

Released

28. 4. 2020

Publisher

ROYAL SOC CHEMISTRY

Location

CAMBRIDGE

ISBN

1477-9234

Periodical

Dalton Transactions

Year of study

49

Number

16

State

United Kingdom of Great Britain and Northern Ireland

Pages from

5228

Pages to

5240

Pages count

13

URL

https://pubs.rsc.org/en/content/articlelanding/2020/DT/D0DT00567C#!divAbstract

BibTex

@article{BUT164054,
  author="Sartoris, RP. and Santana, VT. and Freire, E. and Baggio, RF. and Nascimento, OR. and Calvo, R.",
  title="Exchange couplings and quantum phases in two dissimilar arrays of similar copper dinuclear units",
  journal="Dalton Transactions",
  year="2020",
  volume="49",
  number="16",
  pages="5228--5240",
  doi="10.1039/d0dt00567c",
  issn="1477-9234",
  url="https://pubs.rsc.org/en/content/articlelanding/2020/DT/D0DT00567C#!divAbstract"
}