Spin Transition Diagram of (2Me-5Et-PyH)[Fe(Th-5Cl-Sa)_2] Studied by EPR

A. Krupska a, M.A. Augustyniak-Jabłokow a, V.Yu. Yablokova and V.V. Zelentsovb aInstitute of Molecular Physics, Polish Academy of Sciences, Mariana Smoluchowskiego 17, 60-179 Poznań, Poland bMoscow Physical Technical Institute, 141 700 Dolgoprudnii, Russia

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Received: 24 04 2005;

The high-spin ↔ low-spin transition in (2Me-5Et-PyH)[Fe(Th-5Cl-Sa)_2] was studied by EPR under hydrostatic pressure in the temperature range of 80-310 K. Two modifications of the low-spin complexes: low-pressure (LS-1) and high-pressure (LS-2) ones were revealed. The low-spin complexes are associated in domains. Under atmospheric pressure LS-1 appears or disappears at 220 K. The hydrostatic pressure shifts the transition to high temperatures. Above 410 MPa the abrupt changes of the g-factor and width Δ B of the EPR line are observed. The pressure-induced transition LS-1 ↔ LS-2 is almost independent of T up to 275 K where under pressure 420 MPa a triple point is observed. When the pressure has been decreased the reverse transition from LS-2 to LS-1 or to high spin phase (at T>260 K) occurs with a large hysteresis about 95 MPa.

DOI: 10.12693/APhysPolA.108.291 PACS numbers:76.30.-v, 33.35.+r