Invited Speaker
Prof. Georgiy Levchenkо
State Key Laboratory of High Pressure and Superhard MaterialsCollege of Physics, Jilin University, China
Speech Title: Pressure-Induced Low-Spin State Destabilization in an Iron(II) Spin Crossover Complex with Pyrazol-Pyridine-Triazolate Coordination Core
Abstract: Rapidly developing science and technology demand new materials with versatile properties for practical applications. In this context, pseudo-octahedral iron(II) spin crossover (SCO) complexes are particularly appealing—not only for their fundamental scientific interest but also for their perspectives to be used in modern technologies and devices. This talk presents the synthesis and structure of a new mononuclear SCO complex [FeII(L)2]0·nMeOH (n = 2, 0) where L is the asymmetrically substituted tridentate ligand [4-trifluoromethylphenyl-(1H-1,2,4-triazol-5-yl)-6-(1H-pyrazol-1-yl) pyridine], hereafter referred 4CF3 (MeOH). The regular Oh geometry of the unsolvated form, 4CF3, favors a complete spin transition (ST) at room temperature, which has been investigated, in the pressure interval 0–0.64 GPa. Contrary to experience, the increase of pressure on 4CF3 denotes a radically abnormal behavior of this ST, involving: i) decrease of the characteristic temperatures, ii) increase of the high-spin molar fraction in the temperature range of the low-spin state; iii) above certain threshold pressure, full stabilization of the high-spin state. These observations have been explained in the framework of a thermodynamic model based on the elastic interactions.
Keywords: High pressure, spin transition, spin crossover, optical spectra, magnetic susceptibility.
Biography: Georgiy Levchenko is a Doctor of Philosophy and Physical and Mathematical Sciences, Member of the National Academy of Sciences of Ukraine (NASU), Professor of the Jilin University and Chief Researcher of the Donetsk Institute of Physics and Technology of the National Academy of Sciences of Ukraine. In 1974 Georgiy Levchenko graduated with honors from the Faculty of Physics of Donetsk State University, in 1977 he completed postgraduate studies at the Donetsk Institute of Physics and Technology of the NASU. In 1984 he defended his Ph.D., in 1994 – his doctoral dissertation, in 2010 he received the title of Professor in the specialty "Solid State Physics". He is a laureate of the L.V. Shubnikov Prize. Since 2015 – Corresponding Member of the National Academy of Sciences of Ukraine. G.G. Levchenko is a well-known scientist in the field of solid-state physics, magnetism and high-pressure physics. He is one of the originators of the beginning of a broad experimental study of the effect of pressure on various properties of materials and the development of thermodynamic and microscopic approaches to describe this effect.