Spin-crossover (SCO) compounds are promising materials for a wide variety of
industrial applications. However, the fundamental understanding of their nature
of transition and its effect on the physical properties are still being fervently
explored; the microscopic knowledge of their transition is essential for tailoring
their properties. Here an attempt is made to correlate the changes in
macroscopic physical properties with microscopic structural changes in the
orthorhombic and monoclinic polymorphs of the SCO compound Fe(PMBia)
2(NCS)2 (PM = N-20-pyridylmethylene and Bia = 4-aminobiphenyl) by
employing single-crystal X-ray diffraction, magnetization and DSC measurements.
The dependence of macroscopic properties on cooperativity, highlighting
the role of hydrogen bonding, – and van der Waals interactions is discussed.
Values of entropy, enthalpy and cooperativity are calculated numerically based
on the Slichter–Drickamer model. The particle size dependence of the magnetic
properties is probed along with the thermal exchange and the kinetic behavior
of the two polymorphs based on the dependence of magnetization on
temperature scan rate and a theoretical model is proposed for the calculation
of the non-equilibrium spin-phase fraction. Also a scan-rate-dependent two-step
behavior observed for the orthorhombic polymorph, which is absent for the
monoclinic polymorph, is reported. Moreover, it is found that the radiation dose
from synchrotron radiation affects the spin-crossover process and shifts the
transition region to lower temperatures, implying that the spin crossover can be
tuned with radiation damage.

Title

Acta. Cryst.

Publisher

John Wiley & Sons Inc.

Publisher Country

United States of America

Indexing

Scopus

Impact Factor

None

Publication Type

Prtinted only

Volume

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Year

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Pages

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